Re: [AFMUG] another grounding scenario ??
Common point neutral is a good thing. But distributed earth grounds for the true ground circuit is good too. The main thing you want to accomplish for safety’s sake is to allow fault currents to find the lowest impedance path to ground as possible. It is OK to have some voltage drop on neutral circuits, but if a bad wire causes the chassis of a washing machine to become energized, you want that ground wire in the cord to find the lowest potential possible. Otherwise you could be touching the washing machine and the faucet at the same time and get zapped. If the building ground and plumbing and earth are all at the same potential, that would not happen. Earth ground circuits are also important to allow circuit breakers to trip as soon as a fault happens. Again, low impedance ground circuits help with that. I would drive ground rods. But I would also make sure that the neutral bars are floating and not bonded. That would prevent ground loops for the normal power currents. From: Paul McCall Sent: Tuesday, May 05, 2015 7:01 PM To: af@afmug.com Subject: [AFMUG] another grounding scenario ?? We are doing a new tower. Here’s the layout Customer house (Building “A”) has a small building (Building “B” for discussion purposes) about 150 feet away from main house. “B” has a sub-panel and 5 live breakers for various things. There is a 6 gauge ground wire between “B” and the Customer house. “B” connects to another “tack / feeding house” (Building “C”) about 60 feet away with another subpanel running off “B” using a 8 gauge ground wire between those two panels. Neither “B” nor “C” has a ground rod, so they are relying on ground that is ultimately, going back to the Customers house. Our tower box is going to be 200 feet away from Building “C” and because of practicalities, going back to “B” instead is not possible even if we thought that was best. So, I am running 4 gauge wire as our ground from our box to “C” but am concerned about making sure the ground is handled from that point on. An electrician on-site said that each building should actually have its own “local ground” (his simple answer was “drive a ground rod”) . The question I have is does that make sense as a complete (best solution)… making sure that Panel “C” is well grounded (and “B” too just for good measure) ?? In the single source ground concept, is his suggestion still make the best sense? Paul Paul McCall, Pres. PDMNet / Florida Broadband 658 Old Dixie Highway Vero Beach, FL 32962 772-564-6800 office 772-473-0352 cell www.pdmnet.com pa...@pdmnet.net
Re: [AFMUG] another grounding scenario ??
On 5/6/15 7:32 AM, Chuck McCown wrote: Earth ground circuits are also important to allow circuit breakers to trip as soon as a fault happens. Again, low impedance ground circuits help with that. I would drive ground rods. But I would also make sure that the neutral bars are floating and not bonded. That would prevent ground loops for the normal power currents. With pictures: https://www.mikeholt.com/instructor2/img/product/pdf/1292432628sample.pdf ~Seth
Re: [AFMUG] another grounding scenario ??
Good info. We did already verify neutrals and grounds are not tied together. We will definitely drive ground rods at each panel based on the feedback here. From: Af [mailto:af-boun...@afmug.com] On Behalf Of Chuck McCown Sent: Wednesday, May 06, 2015 10:33 AM To: af@afmug.com Subject: Re: [AFMUG] another grounding scenario ?? Common point neutral is a good thing. But distributed earth grounds for the true ground circuit is good too. The main thing you want to accomplish for safety’s sake is to allow fault currents to find the lowest impedance path to ground as possible. It is OK to have some voltage drop on neutral circuits, but if a bad wire causes the chassis of a washing machine to become energized, you want that ground wire in the cord to find the lowest potential possible. Otherwise you could be touching the washing machine and the faucet at the same time and get zapped. If the building ground and plumbing and earth are all at the same potential, that would not happen. Earth ground circuits are also important to allow circuit breakers to trip as soon as a fault happens. Again, low impedance ground circuits help with that. I would drive ground rods. But I would also make sure that the neutral bars are floating and not bonded. That would prevent ground loops for the normal power currents. From: Paul McCallmailto:pa...@pdmnet.net Sent: Tuesday, May 05, 2015 7:01 PM To: af@afmug.commailto:af@afmug.com Subject: [AFMUG] another grounding scenario ?? We are doing a new tower. Here’s the layout Customer house (Building “A”) has a small building (Building “B” for discussion purposes) about 150 feet away from main house. “B” has a sub-panel and 5 live breakers for various things. There is a 6 gauge ground wire between “B” and the Customer house. “B” connects to another “tack / feeding house” (Building “C”) about 60 feet away with another subpanel running off “B” using a 8 gauge ground wire between those two panels. Neither “B” nor “C” has a ground rod, so they are relying on ground that is ultimately, going back to the Customers house. Our tower box is going to be 200 feet away from Building “C” and because of practicalities, going back to “B” instead is not possible even if we thought that was best. So, I am running 4 gauge wire as our ground from our box to “C” but am concerned about making sure the ground is handled from that point on. An electrician on-site said that each building should actually have its own “local ground” (his simple answer was “drive a ground rod”) . The question I have is does that make sense as a complete (best solution)… making sure that Panel “C” is well grounded (and “B” too just for good measure) ?? In the single source ground concept, is his suggestion still make the best sense? Paul Paul McCall, Pres. PDMNet / Florida Broadband 658 Old Dixie Highway Vero Beach, FL 32962 772-564-6800 office 772-473-0352 cell www.pdmnet.comhttp://www.pdmnet.com/ pa...@pdmnet.netmailto:pa...@pdmnet.net
[AFMUG] another grounding scenario ??
We are doing a new tower. Here's the layout Customer house (Building A) has a small building (Building B for discussion purposes) about 150 feet away from main house. B has a sub-panel and 5 live breakers for various things. There is a 6 gauge ground wire between B and the Customer house. B connects to another tack / feeding house (Building C) about 60 feet away with another subpanel running off B using a 8 gauge ground wire between those two panels. Neither B nor C has a ground rod, so they are relying on ground that is ultimately, going back to the Customers house. Our tower box is going to be 200 feet away from Building C and because of practicalities, going back to B instead is not possible even if we thought that was best. So, I am running 4 gauge wire as our ground from our box to C but am concerned about making sure the ground is handled from that point on. An electrician on-site said that each building should actually have its own local ground (his simple answer was drive a ground rod) . The question I have is does that make sense as a complete (best solution)... making sure that Panel C is well grounded (and B too just for good measure) ?? In the single source ground concept, is his suggestion still make the best sense? Paul Paul McCall, Pres. PDMNet / Florida Broadband 658 Old Dixie Highway Vero Beach, FL 32962 772-564-6800 office 772-473-0352 cell www.pdmnet.comhttp://www.pdmnet.com/ pa...@pdmnet.netmailto:pa...@pdmnet.net
Re: [AFMUG] another grounding scenario ??
The electricians that I have spoken with say bond to existing power ground and then pound another rod right at your connection. That is what we've always done. On Tue, May 5, 2015 at 7:01 PM, Paul McCall pa...@pdmnet.net wrote: We are doing a new tower. Here’s the layout Customer house (Building “A”) has a small building (Building “B” for discussion purposes) about 150 feet away from main house. “B” has a sub-panel and 5 live breakers for various things. There is a 6 gauge ground wire between “B” and the Customer house. “B” connects to another “tack / feeding house” (Building “C”) about 60 feet away with another subpanel running off “B” using a 8 gauge ground wire between those two panels. Neither “B” nor “C” has a ground rod, so they are relying on ground that is ultimately, going back to the Customers house. Our tower box is going to be 200 feet away from Building “C” and because of practicalities, going back to “B” instead is not possible even if we thought that was best. So, I am running 4 gauge wire as our ground from our box to “C” but am concerned about making sure the ground is handled from that point on. An electrician on-site said that each building should actually have its own “local ground” (his simple answer was “drive a ground rod”) . The question I have is does that make sense as a complete (best solution)… making sure that Panel “C” is well grounded (and “B” too just for good measure) ?? In the single source ground concept, is his suggestion still make the best sense? Paul Paul McCall, Pres. PDMNet / Florida Broadband 658 Old Dixie Highway Vero Beach, FL 32962 772-564-6800 office 772-473-0352 cell www.pdmnet.com pa...@pdmnet.net
Re: [AFMUG] another grounding scenario ??
The general rule is one grounding point. However, if the sub panels are
far enough apart and/or the interconnecting ground wire is too small,
you might consider adding another ground rod. I'm guessing that the
distance to your tower is far enough away from the original ground and
the interconnect is small enough that you might want to drive another
ground rod.
OTOH, I am not an electrician...
bp
part15sbs{at}gmail{dot}com
On 5/5/2015 6:01 PM, Paul McCall wrote:
We are doing a new tower. Here�s the layout
Customer house (Building �A�) has a small building (Building �B� for
discussion purposes) about 150 feet away from main house. �B� has a
sub-panel and 5 live breakers for various things. There is a 6 gauge
ground wire between �B� and the Customer house. �B� connects to
another �tack / feeding house� (Building �C�) about 60 feet away with
another subpanel running off �B� using a 8 gauge ground wire between
those two panels. Neither �B� nor �C� has a ground rod, so they are
relying on ground that is ultimately, going back to the Customers house.
Our tower box is going to be 200 feet away from Building �C� and
because of practicalities, going back to �B� instead is not possible
even if we thought that was best. So, I am running 4 gauge wire as
our ground from our box to �C� but am concerned about making sure the
ground is handled from that point on. An electrician on-site said
that each building should actually have its own �local ground� (his
simple answer was �drive a ground rod�) .
The question I have is does that make sense as a complete (best
solution)� making sure that Panel �C� is well grounded (and �B� too
just for good measure) ?? In the single source ground concept, is his
suggestion still make the best sense?
Paul
Paul McCall, Pres.
PDMNet / Florida Broadband
658 Old Dixie Highway
Vero Beach, FL 32962
772-564-6800 office
772-473-0352 cell
www.pdmnet.com http://www.pdmnet.com/
pa...@pdmnet.net mailto:pa...@pdmnet.net
