Gene Heskett wrote: > On Wednesday 20 May 2009, Joerg wrote: >> Gene Heskett wrote: >>> On Wednesday 20 May 2009, Joerg wrote: >>>> DJ Delorie wrote: >>>>> Levente Kovacs <[email protected]> writes: >>>>>> 230V times 100A is something I dont want to even calculate. >>>>> It's 23000 :-) >>>>> >>>>> My air conditioner draws 123 amps at 240 volts for the first few >>>>> seconds. That's almost 30kW. >>>> Seconds and not fractions or a second? Yikes! Unless it's a 10-15 ton >>>> unit that doesn't sound normal. Did you find some of the power hogs with >>>> your new board by now? >>> Off topic reply, but could be germain too. >>> >>> Not even a 40 horse compressor in a 22 ton (rated, yeah sure) Lennox will >>> draw that much for that long. Its startup was a peak in the 250 >>> amps/phase area, and the reason I say area is that a std 400 amp scale on >>> an amp-probe on any phase line swung up to 250 and back down to its >>> running of about 39 amps/phase in a purely ballistic fashion as the >>> startup surge was only 6 or 7 cycles of the 208/3 phase line. >>> >>> Now it really gets off-topic. >>> >>> That was one of those _must_ _work_ units else a tv station was off the >>> air 10 (or less) minutes after it failed. It was also probably >>> responsible for some of the early ozone holes over the antarctic as it was >>> severely under fanned on the condensor side, and I had to add 20 pounds of >>> freon in the fall to keep it working right until it wasn't needed, and >>> bleed that 20 pounds back off as spring turned into summer. This went on >>> for 8 years on my watch, back in the 70's, and long before they started >>> regulating all that stuff. >>> >>> 2 ea. 1100rpm 1/2 horse motors turning 24" fans just didn't cut it. I got >>> tired of that one spring and fixed _some_ of it by taking a failed motor >>> to town, having the brackets stretched to carry 2 horse 1800 rpm motors, >>> replacing the motor with a 2 horse 1800 and repeating it the next week >>> with the second one. 2 horse wasn't quite enough as they ran a couple of >>> amps over nameplate when the condensor was relatively clean. When those >>> blades failed (fatigue cracks, caught before they made shrapnel), I >>> replaced them with blades with an inch less pitch. That allowed it to >>> continue to work until the ambient went over 80 degrees without bleeding >>> freon to keep the high side under 400 psi and the compressor currents >>> under 43 amps/phase else the overcurrents in the compressor would trip. >>> Based on those results, I would have said that a single 20hp motor, >>> running at full load pulling a quad torrington wheel with each half about >>> 16" wide & 14" diameter, would have been about right. That could have >>> been throttled with a 4' square louver driven by a M-H proportional >>> control Modutrol to regulate the high side pressures/temps and made it >>> work all year. Some of the crappy designs foisted off on the industry by >>> supposedly reputable, old line makers are amazingly loaded with excrement. >>> I even called Lennox and they swore on a stack of bibles that those 2, >>> 1/2 horse motors were enough. I asked what was the expected operating >>> temperature range and he said 75-90F outside. I said "and what happens >>> when you have enough heat load to need it, but the outside temp is 33F?" >>> "Its not designed to run at those temps." Why did you sell it to the >>> State of Nebraska then, you did have the specs, I've seen them? Mumble. >>> >>> Obviously I wasn't talking to a real engineer so I asked him where he got >>> his sheepskin. More mumbling. >>> >>> Being a tv engineer for the state NETV commission, when the nearest help >>> is 200 miles away in Star City, (Lincoln NE) means you truly are a Jack Of >>> All Trades. :) Those 8 years were _very_ educational, but I left because >>> I was still not the lead dog, so the scenery never changed. :) >> Thanks for sharing, that was a real story from the trenches. >> >> Not looking forward to the 105F days that are coming. I don't need A/C >> even when it gets to 95F in the office but when visitors come I have to. >> And then the compressor often goes into bypass mode making that awful >> rarrrrr noise. Then it's waiting 5-10 mins, crossing fingers, make sure >> no black cat crosses street from right to left, turn switch to the old >> Lennox back on, hold breath. > > Then it needs help like I've described. That sort of a locked rotor shutdown > is pure hell on the compressors. No other nice way to describe it unforch. >
But I can't really bleed off freon. Plus AFAIK they don't sell that stuff to ordinary folk anymore unless you have a contractor's license. I mean, I could get one, but that would go a bit far ;-) -- Regards, Joerg http://www.analogconsultants.com/ _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
