RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources
The primary purpose of the equipment grounding conductor (green wire) is to provide a low-impedance path for fault current on a branch circuit. The lowest-possible impedance is realized only when the EGC is routed alongside the phase conductor. Article 250.24(C)(1) states: This conductor shall be routed with the phase conductor... I didn't quote the entire sentence, because it is very long. I understand that. What I was saying is that isn't the *only* ground path. You're almost guaranteed to have multiple ground fault paths, therefore EGC's from both systems are already tied together by virtue of those other paths. Even if you didn't intentionally jumper the EGC's together, if you had one device plugged into one outlet and another plugged into another outlet and both devices mounted in the same rack (or, even just sitting on top of each other), the EGC's will be electrically joined through the units' metal cabinet exteriors. The reason for keeping the equipment grounding conductors separate is very simple; we are talking about a hospital, not some ordinary radio shack. The critical (red) buss likely feeds catheter labs, dialysis machines, mechanical respirators, and similar equipment that is connected to human bodies. Even a few milliamperes of stray current flowing through a grounding conductor may take a side trip through a patient's heart and kill them. Well, now we're getting into a completely different topic. Line powered medical equipment is wholly isolated from the patient. While I'm no expert on the subject, there's something called the isolation barrier which wholly isolates the patient from the electrical system. One of the previous posters suggested putting the computer on the white buss, with the repeater on the red buss. That's a good idea, but be careful to use a fiber-optic link to pass data between them, else the two devices will have a common ground connection through the data cable's shield. Depending on what the interface is between the two, that may or may not be necessary. Twisted pair Ethernet is transformer-coupled, so no additional isolation is necessary (just don't use shielded cable). For simple things like control logic (PTT, COR, whatever), just use an optocoupler. For audio, transformers. --- Jeff WN3A
RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources
Jeff, Whether multiple ground paths exist is irrelevant. What the NEC requires is a direct, low-impedance fault return path for each branch circuit, considered individually. You cannot dispense with any ground paths because you think there exists alternate paths. While it is true that parallel paths may decrease the total impedance to a fault on any one branch circuit, that in no way constitutes license to eliminate a required grounding connection. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jeff DePolo Sent: Friday, July 18, 2008 7:50 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources The primary purpose of the equipment grounding conductor (green wire) is to provide a low-impedance path for fault current on a branch circuit. The lowest-possible impedance is realized only when the EGC is routed alongside the phase conductor. Article 250.24(C)(1) states: This conductor shall be routed with the phase conductor... I didn't quote the entire sentence, because it is very long. I understand that. What I was saying is that isn't the *only* ground path. You're almost guaranteed to have multiple ground fault paths, therefore EGC's from both systems are already tied together by virtue of those other paths. Even if you didn't intentionally jumper the EGC's together, if you had one device plugged into one outlet and another plugged into another outlet and both devices mounted in the same rack (or, even just sitting on top of each other), the EGC's will be electrically joined through the units' metal cabinet exteriors. The reason for keeping the equipment grounding conductors separate is very simple; we are talking about a hospital, not some ordinary radio shack. The critical (red) buss likely feeds catheter labs, dialysis machines, mechanical respirators, and similar equipment that is connected to human bodies. Even a few milliamperes of stray current flowing through a grounding conductor may take a side trip through a patient's heart and kill them. Well, now we're getting into a completely different topic. Line powered medical equipment is wholly isolated from the patient. While I'm no expert on the subject, there's something called the isolation barrier which wholly isolates the patient from the electrical system. One of the previous posters suggested putting the computer on the white buss, with the repeater on the red buss. That's a good idea, but be careful to use a fiber-optic link to pass data between them, else the two devices will have a common ground connection through the data cable's shield. Depending on what the interface is between the two, that may or may not be necessary. Twisted pair Ethernet is transformer-coupled, so no additional isolation is necessary (just don't use shielded cable). For simple things like control logic (PTT, COR, whatever), just use an optocoupler. For audio, transformers. --- Jeff WN3A
RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources
Jeff, Whether multiple ground paths exist is irrelevant. What the NEC requires is a direct, low-impedance fault return path for each branch circuit, considered individually. You cannot dispense with any ground paths because you think there exists alternate paths. While it is true that parallel paths may decrease the total impedance to a fault on any one branch circuit, that in no way constitutes license to eliminate a required grounding connection. 73, Eric Lemmon WB6FLY I KNOW! I'm not trying to eliminate the required EGC run along with the current-carrying conductors. What I'm asking is why you originally said that you should switch the EGC supplied by the two outlets rather than tying the two together. I had asked if there were any provisions in NEC that allowed for EGC's (whether from two different SDS's or otherwise) to ever be switched, as I can't recall there being any such case allowed in NEC. You replied that by tying EGC's together that you would create a new path whereby new, harful currents could flow. I replied that there always exist multiple EGC paths, whether desired or not, and in the instant case, there are, or would be, paths between the EGC's of the two systems whether or not you tied them together. So, my question remains, is there a case to be made where it is desirable, or even allowable, that the EGC can or should be switched? Let's assume that in the instant case (the hospital) that they are SDS's. --- Jeff WN3A
RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources
Jeff, I understand and appreciate the nuances of your question. I guess what I am trying to convey, perhaps unsuccessfully, is that it is unwise to attempt to make a case for an exception to the NEC based upon conventional wisdom. I guess I'm not explaining myself well either then. I'm trying NOT to go against NEC. I don't believe NEC allows you to switch EGC as you originally proposed - that's the issue at hand. I'm not proposing that you eliminate the NEC-required EGC in any way, shape, or form, even though there likely exist many alternative ground paths capable of tripping the overcurrent device in the event of a fault even if the hard-wired EGC didn't exist. I was just pointing out that even if the two outlets are on two different SDS's, that the EGC's are already effectively tied together whether or not you hard-wired them together in the switching gizmo in the repeater rack. I believe that you are saying that if we assume that we have two SDS's, then we have two totally independent EGC's, and the two EGC's must not be allowed to be tied together, hence the need to switch the EGC's (as well as the hot and neutral) when switching between the sources, for if you don't, you will create a hazardous condition. That's where I started to disagree, which is what prompted me to ask if there is *any* situation where switching EGC is allowed in NEC, because I can't recall ever seeing anything like that in the past but I thought maybe you knew something I didn't. My advice is to always ask the AHJ (Authority Having Jurisdiction) to provide an interpretation in writing. His or her interpretation of the NEC will always trump that of a hospital electrician, or even a consulting engineer. The answer to your specific question varies, depending upon the opinion of the AHJ, and nothing I or you say or think will change that, I agree that the AHJ is the final word. But it's not necessarily an issue of the AHJ official's *interpretation* of NEC. There are plenty of AHJ's that have regulations that are more stringent than NEC, or less stringent than NEC, or in some cases, completely contradictory to NEC. --- Jeff WN3A
RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources
At 08:44 AM 07/14/08, you wrote: On Sun, 13 Jul 2008, Richard wrote: Maybe you could install a battery bank with a good quality four stage charger to power the repeaters. When the power drops, since the repeaters are already running on batteries, the switchover would be seamless. Good idea, but batteries weigh a lot. And they can explode when struck by lightning. Also, does the original poster own the radio room? If not, he probably can't dictate how much more space he takes in the place. Your IRLP computer could be powered with a 1500 watt or better UPS. This should allow sufficient runtime, plus the higher capacity should get you out of the cheapo consumer grade UPS category. As Eric A 1500W UPS is overkill for a 100W load. -- Kris Kirby, KE4AHR [EMAIL PROTECTED] Yeah, but they are pretty much free if you know where to look. A while back I had to re-battery six of them that were recovered from a dumpster behind a hospital. Nothing wrong with them, just needed new batteries. And some of the older APCs had a 150a powerpole mount in the bottom for an external battery pack that gave more run-time.. Mike WA6ILQ
Re: [Repeater-Builder] Switching a Repeater Betwen AC Sources
Good points Richard. Not trying be a smart a$$, so please don't take this comment that way, but what is the service worth to the community? SKYWARN, and up here in Canada CANWARN, are valuable services that can save lives. Property can be replaced, lives can't. Maybe there is some local, state or federal money that could be tapped into or maybe even some private money for that matter. Maybe suppliers would be willing to give the group a break on pricing or even provide it at a substantial savings to the group. I would go direct to the manufacturer. Couple of thoughts on monitoring power outage. - Some controllers have inputs that can be monitored and if a signal is sensed it sets off an alarm. But a walwart could be plugged into the main receptacle and connected to a controller input with some cleaned up DC of course. In the event of a power failure, the controller would no longer see the precense of the required voltage and notification could be provided, hopefully spoken if that option is available, and a designated person(s) could attend the site to check power. If you know your runtime on the UPS, you know what your response time needs to be. - I forgot that there was an IRLP computer at the site. In that case, some UPS monitoring software will run on a unix/linux platform, there is notification as well, as this software can advise you of outages, self test results etc, etc by email. I am thinking here of the APC line, we use them at our data centre for backup server power and in all of our LAN closets for backup switch stack power. I mentioned APC, I have nothing to do with APC, I have only used their products and have always been pleased with the results. Eric, VA3EAM Richard wrote: It would have to be a very large, very high capacity UPS, in order to handle the current the transmitters draw. This would be very expensive. Maybe you could install a battery bank with a good quality four stage charger to power the repeaters. When the power drops, since the repeaters are already running on batteries, the switchover would be seamless. Your IRLP computer could be powered with a 1500 watt or better UPS. This should allow sufficient runtime, plus the higher capacity should get you out of the cheapo consumer grade UPS category. As Eric suggests, you could plug the serial cable into the computer, and with the right software, the node could monitor the battery voltage when it is running on the UPS, then shut the computer down gracefully if the voltage drops too low. Richard www.n7tgb.net http://www.n7tgb.net/
RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources
It is important to switch all three power leads, not just the hot lead, because neutrals from separate sources cannot be made common- especially when a separately-derived power source is involved- and the equipment grounds must guide any fault current back to the source via the most direct route, which is alongside the respective hot conductor. Eric, you probably have more experience with industrial electrical than I do, but I can't recall anywhere in NEC where switching EGC is permitted, even with separately-derived systems. My copy of NEC is back at the shop, maybe you have yours handy and can provide a reference for my own edjumication. I would tend to think that in a large industrial complex like a hospital or high-rise building that the distributed, and unavoidable, ground paths, (i.e. the entire building including conduits, building steel, concrete, water pipes, etc.) is almost guaranteed to pose a much lower impedance fault current path than can a single equipment grounding conductor run alongside the hot. As a sidebar, many, if not most, emergency generator installations at communication sites are not seperately-derived systems because the neutrals *are* tied together at the transfer switch. However, in the instant case, where it is unknown whether or not the red and white are on separate systems, I agree that switching the neutral and hot is the only safe way to go. --- Jeff WN3A
RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources
On Sun, 13 Jul 2008, Richard wrote: Maybe you could install a battery bank with a good quality four stage charger to power the repeaters. When the power drops, since the repeaters are already running on batteries, the switchover would be seamless. Good idea, but batteries weigh a lot. And they can explode when struck by lightning. Also, does the original poster own the radio room? If not, he probably can't dictate how much more space he takes in the place. Your IRLP computer could be powered with a 1500 watt or better UPS. This should allow sufficient runtime, plus the higher capacity should get you out of the cheapo consumer grade UPS category. As Eric A 1500W UPS is overkill for a 100W load. -- Kris Kirby, KE4AHR [EMAIL PROTECTED] But remember, with no superpowers comes no responsibility. --rly
RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources
Jeff, The primary purpose of the equipment grounding conductor (green wire) is to provide a low-impedance path for fault current on a branch circuit. The lowest-possible impedance is realized only when the EGC is routed alongside the phase conductor. Article 250.24(C)(1) states: This conductor shall be routed with the phase conductor... I didn't quote the entire sentence, because it is very long. The reason for keeping the equipment grounding conductors separate is very simple; we are talking about a hospital, not some ordinary radio shack. The critical (red) buss likely feeds catheter labs, dialysis machines, mechanical respirators, and similar equipment that is connected to human bodies. Even a few milliamperes of stray current flowing through a grounding conductor may take a side trip through a patient's heart and kill them. It the cath lab, there are usually grounding monitors that will cause an alarm if any stray current is detected. The notion that someone is jury-rigging an electrical connection that will make common connections between a white and a red system is frightening. Although such a connection will likely be passive most of the time, if a fault occurs in the equipment, that fault may perturb critical medical equipment- with tragic results. In the hospital where I have a repeater on the red circuit, that circuit is separately-derived by definition, since it has a separate transformer upstream of the automatic transfer switch. Even though I am a certified electrical inspector, I asked for an independent inspection and a signed certificate of compliance before I plugged anything in. One of the previous posters suggested putting the computer on the white buss, with the repeater on the red buss. That's a good idea, but be careful to use a fiber-optic link to pass data between them, else the two devices will have a common ground connection through the data cable's shield. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jeff DePolo Sent: Monday, July 14, 2008 8:20 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources It is important to switch all three power leads, not just the hot lead, because neutrals from separate sources cannot be made common- especially when a separately-derived power source is involved- and the equipment grounds must guide any fault current back to the source via the most direct route, which is alongside the respective hot conductor. Eric, you probably have more experience with industrial electrical than I do, but I can't recall anywhere in NEC where switching EGC is permitted, even with separately-derived systems. My copy of NEC is back at the shop, maybe you have yours handy and can provide a reference for my own edjumication. I would tend to think that in a large industrial complex like a hospital or high-rise building that the distributed, and unavoidable, ground paths, (i.e. the entire building including conduits, building steel, concrete, water pipes, etc.) is almost guaranteed to pose a much lower impedance fault current path than can a single equipment grounding conductor run alongside the hot. As a sidebar, many, if not most, emergency generator installations at communication sites are not seperately-derived systems because the neutrals *are* tied together at the transfer switch. However, in the instant case, where it is unknown whether or not the red and white are on separate systems, I agree that switching the neutral and hot is the only safe way to go. --- Jeff WN3A
RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources
You do have a point about the batteries. I did see that it was revealed in a later post that his main Skywarn (ARES? I forget which) repeater is a MastrII, which I don't think lends itself well to run on batteries. The reason I suggested that size UPS, was to move out of the junk consumer grade UPS' that I don't think should be in a repeater site. Besides, think of the runtime with a UPS a large as that! Richard http://www.n7tgb.net/ www.n7tgb.net _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Kris Kirby Sent: Monday, July 14, 2008 8:44 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources On Sun, 13 Jul 2008, Richard wrote: Maybe you could install a battery bank with a good quality four stage charger to power the repeaters. When the power drops, since the repeaters are already running on batteries, the switchover would be seamless. Good idea, but batteries weigh a lot. And they can explode when struck by lightning. Also, does the original poster own the radio room? If not, he probably can't dictate how much more space he takes in the place. Your IRLP computer could be powered with a 1500 watt or better UPS. This should allow sufficient runtime, plus the higher capacity should get you out of the cheapo consumer grade UPS category. As Eric A 1500W UPS is overkill for a 100W load. -- Kris Kirby, KE4AHR [EMAIL PROTECTED] mailto:kris%40catonic.us us But remember, with no superpowers comes no responsibility. --rly
RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources
I'm not taking it the wrong way, not to worry! Good idea on the soliciting of funds, but I'd be careful of any strings attached. That is a good idea about the monitoring software on the IRLP node. I use that on mine, and it sends an email to my cell phone when the power drops, then again when it is restored. Richard http://www.n7tgb.net/ www.n7tgb.net _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Eric M. Sent: Monday, July 14, 2008 5:12 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Switching a Repeater Betwen AC Sources Good points Richard. Not trying be a smart a$$, so please don't take this comment that way, but what is the service worth to the community? SKYWARN, and up here in Canada CANWARN, are valuable services that can save lives. Property can be replaced, lives can't. Maybe there is some local, state or federal money that could be tapped into or maybe even some private money for that matter. Maybe suppliers would be willing to give the group a break on pricing or even provide it at a substantial savings to the group. I would go direct to the manufacturer. Couple of thoughts on monitoring power outage. - Some controllers have inputs that can be monitored and if a signal is sensed it sets off an alarm. But a walwart could be plugged into the main receptacle and connected to a controller input with some cleaned up DC of course. In the event of a power failure, the controller would no longer see the precense of the required voltage and notification could be provided, hopefully spoken if that option is available, and a designated person(s) could attend the site to check power. If you know your runtime on the UPS, you know what your response time needs to be. - I forgot that there was an IRLP computer at the site. In that case, some UPS monitoring software will run on a unix/linux platform, there is notification as well, as this software can advise you of outages, self test results etc, etc by email. I am thinking here of the APC line, we use them at our data centre for backup server power and in all of our LAN closets for backup switch stack power. I mentioned APC, I have nothing to do with APC, I have only used their products and have always been pleased with the results. Eric, VA3EAM Richard wrote: It would have to be a very large, very high capacity UPS, in order to handle the current the transmitters draw. This would be very expensive. Maybe you could install a battery bank with a good quality four stage charger to power the repeaters. When the power drops, since the repeaters are already running on batteries, the switchover would be seamless. Your IRLP computer could be powered with a 1500 watt or better UPS. This should allow sufficient runtime, plus the higher capacity should get you out of the cheapo consumer grade UPS category. As Eric suggests, you could plug the serial cable into the computer, and with the right software, the node could monitor the battery voltage when it is running on the UPS, then shut the computer down gracefully if the voltage drops too low. Richard http://www.n7tgb.net/ www.n7tgb.net http://geo.yahoo.com/serv?s=97359714/grpId=104168/grpspId=1705063108/ msgId=83529/stime=1216011209/nc1=4025338/nc2=5191955/nc3=5349276
Re: [Repeater-Builder] Switching a Repeater Betwen AC Sources
I work in a hospital, so I have some insight into this. First off, at least in Missouri, the receptacles, wiring, and circuit breakers are rated for 20 amps each. SO, normally, this would not be a problem. In fact, you could probably run the radio systems entirely on the red receptacles all the time. I wouldn't try to put in any kind of relay, or transfer switch, as that's handled down near the generators. HOWEVER, I would definitely run this past the hospital's electricians to ensure that the circuits involved do not have something else sharing the circuit. Sometimes, alas, several receptacles may be fed by only one circuit. This may have been the case with your white receptacles as well. So you need to make sure that there's nothing else on that circuit that will overload things. I'll mention this, look and see if there was a laser printer on the white circuit. They have high instatenous loads as they heat up the fuser drum, and it might've been the combination of your power supplies and the printer coming on that tripped the breaker. And keep the printer on the white receps, as there's almost no reason to have a laser printer on emergency power (unless an administrator orders it). Ray Brown, CBET, BMET II(KB0STN) Laryn Lohman [EMAIL PROTECTED] wrote: We have two repeaters, plus an IRLP computer, on one emergency-fed circuit at a hospital. There are normally no problems with this. During a recent storm, the AC panel circuit breaker tripped, taking everything down in the middle of our Skywarn net. There are two receptacles near our equipment. One is normal power, the other is the red Critical Power receptacle. What problems would anyone see if we would feed everything from the normal power circuit, and if it would ever trip off, switch to the red receptacle. That way, if lightning trips the normal circuit, we would instantly feed our equipment from the red receptacle. This sounds so simple, and I'm inclined to build such a setup, but am I missing something obvious that could cause problems? Any better ideas? Laryn K8TVZ
Re: [Repeater-Builder] Switching a Repeater Betwen AC Sources
On Sun, 13 Jul 2008, Ray Brown wrote: Laryn Lohman [EMAIL PROTECTED] wrote: We have two repeaters, plus an IRLP computer, on one emergency-fed circuit at a hospital. There are normally no problems with this. During a recent storm, the AC panel circuit breaker tripped, taking everything down in the middle of our Skywarn net. There are two receptacles near our equipment. One is normal power, the other is the red Critical Power receptacle. What problems would anyone see if we would feed everything from the normal power circuit, and if it would ever trip off, switch to the red receptacle. That way, if lightning trips the normal circuit, we would instantly feed our equipment from the red receptacle. Plug the repeaters into the red outlet, and plug everything else into the white outlet. -- Kris Kirby, KE4AHR [EMAIL PROTECTED] But remember, with no superpowers comes no responsibility. --rly
RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources
Laryn, The simple, and most practical solution, is to use a 3PDT AC relay to switch between normal and emergency sources. Feed the coil of the relay from your normal source, and wire the hot, neutral, and ground from the normal source to the NO contacts, and the hot, neutral, and ground wires from the emergency source to the NC contacts. The common (swinger) leads go to your repeater. This way, the relay normally stays energized, and the now-closed NO contacts feed your repeater. When the normal buss fails, the relay relaxes and closes the NC contact to connect your repeater to the emergency buss. Voila! It is important to switch all three power leads, not just the hot lead, because neutrals from separate sources cannot be made common- especially when a separately-derived power source is involved- and the equipment grounds must guide any fault current back to the source via the most direct route, which is alongside the respective hot conductor. You might discuss this issue with the hospital electrician, since the critical buss may already be supplied from the normal buss during normal operation. If that's true, the proposed relay scheme is redundant. But, before you do anything, find out what caused that tripped circuit breaker- there may be a dangerous condition that must be fixed. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Laryn Lohman Sent: Sunday, July 13, 2008 5:18 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Switching a Repeater Betwen AC Sources We have two repeaters, plus an IRLP computer, on one emergency-fed circuit at a hospital. There are normally no problems with this. During a recent storm, the AC panel circuit breaker tripped, taking everything down in the middle of our Skywarn net. There are two receptacles near our equipment. One is normal power, the other is the red Critical Power receptacle. What problems would anyone see if we would feed everything from the normal power circuit, and if it would ever trip off, switch to the red receptacle. That way, if lightning trips the normal circuit, we would instantly feed our equipment from the red receptacle. This sounds so simple, and I'm inclined to build such a setup, but am I missing something obvious that could cause problems? Any better ideas? Laryn K8TVZ
Re: [Repeater-Builder] Switching a Repeater Betwen AC Sources
Laryn, Your thinking is good. A simple relay, 3 pole/double throw would do what you want and power the relay coil with your normal AC power. When it goes the relay drops out and connects the repeater to the RED emergency outlet. As someone else suggested switch all 3 wires of hot, neutral and safety ground just to make sure you are not connecting something that you should not. Some suggest runing the repeater on the RED emergency outlet and all else on the normal outlet. You need to check to see if this RED outlet is powered all the time and not just when the gen/emergency power is running. Since it goes to the generator it might not be. Easy to check by plugging a lamp under normal power conditions. The only problems I see is the sudden switching back and forth that might occur quickly serval times in a short period. Like turning on/off the repeater power supply rapidly, but don't think this would be an issue. 73, ron, n9ee/r From: Laryn Lohman [EMAIL PROTECTED] Date: 2008/07/13 Sun PM 08:17:51 EDT To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Switching a Repeater Betwen AC Sources We have two repeaters, plus an IRLP computer, on one emergency-fed circuit at a hospital. There are normally no problems with this. During a recent storm, the AC panel circuit breaker tripped, taking everything down in the middle of our Skywarn net. There are two receptacles near our equipment. One is normal power, the other is the red Critical Power receptacle. What problems would anyone see if we would feed everything from the normal power circuit, and if it would ever trip off, switch to the red receptacle. That way, if lightning trips the normal circuit, we would instantly feed our equipment from the red receptacle. This sounds so simple, and I'm inclined to build such a setup, but am I missing something obvious that could cause problems? Any better ideas? Laryn K8TVZ Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: [Repeater-Builder] Switching a Repeater Betwen AC Sources
Sorry, Ron, I disagree with the relay idea. If it's critical that the radio power supply be up all the time, then run it in the emergency circuits, which ARE active all the time. Our main ambulance radio and our maintenance repeater are on emergency power, as I specificied and coordinated the istallation of both of them myself. The only switching occurs when the power goes down, all receptacles (both white and red are now dead) then the generators fire up within 15 seconds, stabilize, and transfer the feed of the red receptacles from the outside utility to the generators. Power switches back automatically after utility power has been restored and stays up for at least 5 continuous minutes with no dropouts. Then the generators run on cool-down for at least 10 minutes. My CBET rating means I'm certified as a Biomedical Equipment Technician on 6 levels of the proper care and feeding of medical instrumentation, including power supplies. :-) And, Laryn, I re-read your initial statement. You had 2 repeaters AND a computer on the same circuit, and it tripped? Again, what all was on that circuit? If the printer was also on that same circuit, you need to get it off the red and on the white. But even 100 watt repeaters with linear supplies should only draw 4 amps each on full load, plus 4 for the PC and display. Something else is on the circuit. Shame you can't take pictures. Check with the hospital electrician and see what's up. Good luck! Ray Ron Wright [EMAIL PROTECTED] wrote: Laryn, Your thinking is good. A simple relay, 3 pole/double throw would do what you want and power the relay coil with your normal AC power. When it goes the relay drops out and connects the repeater to the RED emergency outlet. As someone else suggested switch all 3 wires of hot, neutral and safety ground just to make sure you are not connecting something that you should not. Some suggest runing the repeater on the RED emergency outlet and all else on the normal outlet. You need to check to see if this RED outlet is powered all the time and not just when the gen/emergency power is running. Since it goes to the generator it might not be. Easy to check by plugging a lamp under normal power conditions. The only problems I see is the sudden switching back and forth that might occur quickly serval times in a short period. Like turning on/off the repeater power supply rapidly, but don't think this would be an issue. 73, ron, n9ee/r From: Laryn Lohman Date: 2008/07/13 Sun PM 08:17:51 EDT To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Switching a Repeater Betwen AC Sources We have two repeaters, plus an IRLP computer, on one emergency-fed circuit at a hospital. There are normally no problems with this. During a recent storm, the AC panel circuit breaker tripped, taking everything down in the middle of our Skywarn net. There are two receptacles near our equipment. One is normal power, the other is the red Critical Power receptacle. What problems would anyone see if we would feed everything from the normal power circuit, and if it would ever trip off, switch to the red receptacle. That way, if lightning trips the normal circuit, we would instantly feed our equipment from the red receptacle. This sounds so simple, and I'm inclined to build such a setup, but am I missing something obvious that could cause problems? Any better ideas? Laryn K8TVZ
Re: [Repeater-Builder] Switching a Repeater Betwen AC Sources
At 07:07 PM 07/13/08, you wrote: Laryn, Your thinking is good. A simple relay, 3 pole/double throw would do what you want and power the relay coil with your normal AC power. When it goes the relay drops out and connects the repeater to the RED emergency outlet. As someone else suggested switch all 3 wires of hot, neutral and safety ground just to make sure you are not connecting something that you should not. Some suggest runing the repeater on the RED emergency outlet and all else on the normal outlet. You need to check to see if this RED outlet is powered all the time and not just when the gen/emergency power is running. Since it goes to the generator it might not be. Easy to check by plugging a lamp under normal power conditions. The only problems I see is the sudden switching back and forth that might occur quickly serval times in a short period. Like turning on/off the repeater power supply rapidly, but don't think this would be an issue. 73, ron, n9ee/r I long long time ago no, wrong story. More years than I want to think about I was at a local 2-way shop trying to beg a cabinet... the owner pointed at a old Moto 6 foot one in the corner and said clean it out, leave me the radio, take the rest. So here I was, stripping down a radio cabinet that had come out of a hospital elevator room. It turned out to be a Motrac series 90w high band paging station. The power wiring was exactly as this comment thread was describing, with two power plugs (one labeled Normal and one labeled Generator), and a 4PDT contactor relay that made the entire cabinet jump an inch when it pulled in with a BANG (the contacts were 440vAC 50a rated on a 120vAC coil). The overall design had a clock-motor-driven timer that used a cam and a roller microswitch that implemented a 15 minute delay between generator power and normal power. In other words, a switchover from normal to generator was instantaneous, but normal power had to be on for 15 minutes before the radio system was switched back to it. The box the contactor and timer were in had a rotary switch labeled normal, generator and automatic, with a note saying For bench test use generator cord and set this switch to generator. But this is old technology. Modern electrical practice is that the red outlets are hot all the time, and the white outlets die during a power failure. So the relay is totally un-necessary. Just plug the system into a red outlet, and design it so that a short (one minute or so) outage does not cause any discontent (maybe have an AGM battery in the bottom of the rack). One last comment - the hospital electrician may be keeping a list of what is on the generator outlets. Or maybe the administrative people are. Or maybe there are some other rules. Maybe the local inspectors has their nose in the hospitals electrical business. If I were in your shoes I'd get permission in writing from someone in the hospital before I plugged into that red outlet. I can envision a future situation where someone does a red-outlet-audit and finds your box, and it turns out that the recently-retired electrician gave you verbal permission a year ago, and the new guy has no idea who you are. Then the waste matter hits the rotary airfoil. I'm mentioning this because a friend works at a local convalescent hospital... they recently did a red-outlet-audit (the first in several years) and discovered that they are at 93% of generator capacity... they thought (guessed?) they were at 45-50%. Right now they are seeing what can be shed... i.e. moved from red to white, as a generator upgrade would be a political and financial nightmare (they would have to replace the underground diesel fuel tank with one that is much larger, and that would require major permits / costs / demolition / costs / installation / costs / certification / costs - and that is just for the tank. Then you have to fill it at over $5 a gallon. Then you have the same merry-go-round on upgrading the generator and it's controls and the load transfer switch. Mike WA6ILQ
Re: [Repeater-Builder] Switching a Repeater Betwen AC Sources
Not sure why everyone is having such a hard time understanding the problem here, while unusual, for the red to go dead, it does happen. As was originally stated he thought lightning may have kicked it. So red is dead and white is light (on). So even though a relay (3 pole) sounds like the ticket I doubt you would get the contraption past the biomed electricians. Everything has to be at lwats UL approved and they won't like the thought of anything connected across the main buss and the gen buss. What about a battery bank on a charger on the red or white bank and the regular power supply on the other with diods for switching and isolation. That way you would isolate the main busses by more than a relay and the chance if backfeeding would be almost 0 Just my thoughts. Rob. Ks4ec Sent by Good Messaging (www.good.com) -Original Message- From: Ray Brown [mailto:[EMAIL PROTECTED] Sent: Sunday, July 13, 2008 10:30 PM Eastern Standard Time To: Repeater-Builder@yahoogroups.com Subject:Re: [Repeater-Builder] Switching a Repeater Betwen AC Sources Sorry, Ron, I disagree with the relay idea. If it's critical that the radio power supply be up all the time, then run it in the emergency circuits, which ARE active all the time. Our main ambulance radio and our maintenance repeater are on emergency power, as I specificied and coordinated the istallation of both of them myself. The only switching occurs when the power goes down, all receptacles (both white and red are now dead) then the generators fire up within 15 seconds, stabilize, and transfer the feed of the red receptacles from the outside utility to the generators. Power switches back automatically after utility power has been restored and stays up for at least 5 continuous minutes with no dropouts. Then the generators run on cool-down for at least 10 minutes. My CBET rating means I'm certified as a Biomedical Equipment Technician on 6 levels of the proper care and feeding of medical instrumentation, including power supplies. :-) And, Laryn, I re-read your initial statement. You had 2 repeaters AND a computer on the same circuit, and it tripped? Again, what all was on that circuit? If the printer was also on that same circuit, you need to get it off the red and on the white. But even 100 watt repeaters with linear supplies should only draw 4 amps each on full load, plus 4 for the PC and display. Something else is on the circuit. Shame you can't take pictures. Check with the hospital electrician and see what's up. Good luck! Ray Ron Wright [EMAIL PROTECTED] wrote: Laryn, Your thinking is good. A simple relay, 3 pole/double throw would do what you want and power the relay coil with your normal AC power. When it goes the relay drops out and connects the repeater to the RED emergency outlet. As someone else suggested switch all 3 wires of hot, neutral and safety ground just to make sure you are not connecting something that you should not. Some suggest runing the repeater on the RED emergency outlet and all else on the normal outlet. You need to check to see if this RED outlet is powered all the time and not just when the gen/emergency power is running. Since it goes to the generator it might not be. Easy to check by plugging a lamp under normal power conditions. The only problems I see is the sudden switching back and forth that might occur quickly serval times in a short period. Like turning on/off the repeater power supply rapidly, but don't think this would be an issue. 73, ron, n9ee/r From: Laryn Lohman Date: 2008/07/13 Sun PM 08:17:51 EDT To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Switching a Repeater Betwen AC Sources We have two repeaters, plus an IRLP computer, on one emergency-fed circuit at a hospital. There are normally no problems with this. During a recent storm, the AC panel circuit breaker tripped, taking everything down in the middle of our Skywarn net. There are two receptacles near our equipment. One is normal power, the other is the red Critical Power receptacle. What problems would anyone see if we would feed everything from the normal power circuit, and if it would ever trip off, switch to the red receptacle. That way, if lightning trips the normal circuit, we would instantly feed our equipment from the red receptacle. This sounds so simple, and I'm inclined to build such a setup, but am I missing something obvious that could cause problems? Any better ideas? Laryn K8TVZ Since 1974, the award-winning Alpert JFCS has helped families of all faiths throughout most of Palm Beach County, FL, via counseling, seniors services, residences for the disabled, mentoring children, support groups and a lot more. SOLUTIONS FOR LIVING www.JFCSonline.com Please take note of our new website and E-Mail Addresses. Please update your contacts ASAP
Re: Re: [Repeater-Builder] Switching a Repeater Betwen AC Sources
RAy, If you read my reply I stated make sure the RED outlets are powered at all times by testing with a simple lamp if you want to use all the time. Different states have different codes for Hospitals so would just have to check. I would think the hospital electrical dept would have to notified to make sure the repeater equipment could be connected to the RED outlet. Many times only certain equipment is allowed to prevent overload and other problems. The relay would work if having to switch between outlets. If the RED outlet is powered at all times then probably best to use if allowed. As for UL as someone else mentioned I assure you there are parts of that Ham repeater that do not have UL. Probably low voltage or current, but there are parts in there, but after things like power supplies that are UL. 73, ron, n9ee/r From: Ray Brown [EMAIL PROTECTED] Date: 2008/07/13 Sun PM 10:28:21 EDT To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Switching a Repeater Betwen AC Sources Sorry, Ron, I disagree with the relay idea. If it's critical that the radio power supply be up all the time, then run it in the emergency circuits, which ARE active all the time. Our main ambulance radio and our maintenance repeater are on emergency power, as I specificied and coordinated the istallation of both of them myself./div div /div div The only switching occurs when the power goes down, all receptacles (both white and red are now dead) then the generators fire up within 15 seconds, stabilize, and transfer the feed of the red receptacles from the outside utility to the generators. Power switches back automatically after utility power has been restored and stays up for at least 5 continuous minutes with no dropouts. Then the generators run on cool-down for at least 10 minutes.BR/div div My CBET rating means I'm certified as a Biomedical Equipment Technician on 6 levels of the proper care and feeding of medical instrumentation, including power supplies. :-) And, Laryn, I re-read your initial statement. You had 2 repeaters AND a computer on the same circuit, and it tripped? Again, what all was on that circuit? If the printer was also on that same circuit, you need to get it off the red and on the white. But even 100 watt repeaters with linear supplies should only draw 4 amps each on full load, plus 4 for the PC and display. Something else is on the circuit. Shame you can't take pictures. Check with the hospital electrician and see what's up. Good luck! Ray Ron Wright [EMAIL PROTECTED] wrote: Laryn, Your thinking is good. A simple relay, 3 pole/double throw would do what you want and power the relay coil with your normal AC power. When it goes the relay drops out and connects the repeater to the RED emergency outlet. As someone else suggested switch all 3 wires of hot, neutral and safety ground just to make sure you are not connecting something that you should not. Some suggest runing the repeater on the RED emergency outlet and all else on the normal outlet. You need to check to see if this RED outlet is powered all the time and not just when the gen/emergency power is running. Since it goes to the generator it might not be. Easy to check by plugging a lamp under normal power conditions. The only problems I see is the sudden switching back and forth that might occur quickly serval times in a short period. Like turning on/off the repeater power supply rapidly, but don't think this would be an issue. 73, ron, n9ee/r From: Laryn Lohman Date: 2008/07/13 Sun PM 08:17:51 EDT To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Switching a Repeater Betwen AC Sources We have two repeaters, plus an IRLP computer, on one emergency-fed circuit at a hospital. There are normally no problems with this. During a recent storm, the AC panel circuit breaker tripped, taking everything down in the middle of our Skywarn net. There are two receptacles near our equipment. One is normal power, the other is the red Critical Power receptacle. What problems would anyone see if we would feed everything from the normal power circuit, and if it would ever trip off, switch to the red receptacle. That way, if lightning trips the normal circuit, we would instantly feed our equipment from the red receptacle. This sounds so simple, and I'm inclined to build such a setup, but am I missing something obvious that could cause problems? Any better ideas? Laryn K8TVZ Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: [Repeater-Builder] Switching a Repeater Betwen AC Sources
Why not use a UPS? Plug the repeater and equipment into the UPS and then plug the UPS into the receptacle of choice. Might be cheaper and easier to do this then to design, test, get permission from the hospital to install, install it and maintain it. I am sure that the hospital is going to want to make sure what you install is approved for such use. Some ups's provide a serial port for communication to a serial device, maybe you can access it remotely via packet to check status, logs and battery condition. Eric. Laryn Lohman wrote: We have two repeaters, plus an IRLP computer, on one emergency-fed circuit at a hospital. There are normally no problems with this. During a recent storm, the AC panel circuit breaker tripped, taking everything down in the middle of our Skywarn net. There are two receptacles near our equipment. One is normal power, the other is the red Critical Power receptacle. What problems would anyone see if we would feed everything from the normal power circuit, and if it would ever trip off, switch to the red receptacle. That way, if lightning trips the normal circuit, we would instantly feed our equipment from the red receptacle. This sounds so simple, and I'm inclined to build such a setup, but am I missing something obvious that could cause problems? Any better ideas? Laryn K8TVZ
RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources
It would have to be a very large, very high capacity UPS, in order to handle the current the transmitters draw. This would be very expensive. Maybe you could install a battery bank with a good quality four stage charger to power the repeaters. When the power drops, since the repeaters are already running on batteries, the switchover would be seamless. Your IRLP computer could be powered with a 1500 watt or better UPS. This should allow sufficient runtime, plus the higher capacity should get you out of the cheapo consumer grade UPS category. As Eric suggests, you could plug the serial cable into the computer, and with the right software, the node could monitor the battery voltage when it is running on the UPS, then shut the computer down gracefully if the voltage drops too low. Richard http://www.n7tgb.net/ www.n7tgb.net _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Eric M. Sent: Sunday, July 13, 2008 9:25 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Switching a Repeater Betwen AC Sources Why not use a UPS? Plug the repeater and equipment into the UPS and then plug the UPS into the receptacle of choice. Might be cheaper and easier to do this then to design, test, get permission from the hospital to install, install it and maintain it. I am sure that the hospital is going to want to make sure what you install is approved for such use. Some ups's provide a serial port for communication to a serial device, maybe you can access it remotely via packet to check status, logs and battery condition. Eric. Laryn Lohman wrote: We have two repeaters, plus an IRLP computer, on one emergency-fed circuit at a hospital. There are normally no problems with this. During a recent storm, the AC panel circuit breaker tripped, taking everything down in the middle of our Skywarn net. There are two receptacles near our equipment. One is normal power, the other is the red Critical Power receptacle. What problems would anyone see if we would feed everything from the normal power circuit, and if it would ever trip off, switch to the red receptacle. That way, if lightning trips the normal circuit, we would instantly feed our equipment from the red receptacle. This sounds so simple, and I'm inclined to build such a setup, but am I missing something obvious that could cause problems? Any better ideas? Laryn K8TVZ
