Generator Switch Box
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02-28-2013, 16:34
Post: #1
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Generator Switch Box
Late last summer we lost power on leg two of our Powertech 15kw generator. At the time I suspected the failure was a result of the extreme current I would see when the front AC would start. The amp meter on leg two would peg out.
I called Powertech and they told me I would need a new genny. Anyway I got around to looking at it today and found a burnt wire on the T1 terminal of the generator contractor. The wire size on T1 and T3 was 10ga. All other wire size was 6ga! I replaced the burnt wire and fired up the genny and both legs were hot. Turned on all AC's and noticed the smell and smoke of insulation at the same bad terminal. Turned genny off, seeked help. Are these supposed to be rudimentary fuses? Just kidding. Has any one else seen this? Darrell |
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02-28-2013, 16:58
(This post was last modified: 02-28-2013 17:08 by davidbrady.)
Post: #2
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RE: Generator Switch Box
Hi Darrell,
In the Powertech manual (below) there's specs for the stator coil resistance - I have no experience with checking this, but it's recommended in the troubleshooting tips. Also, it looks like 10 gauge wiring at T1 and T3 is factory standard. You may want to check for excessive current draw from the AC's, but it seems that a circuit breaker should also trip. Maybe both a faulty circuit breaker and excessive current draw. Here's a Powertech Owner's Manual with troubleshooting tips: http://wanderlodgegurus.com/showthread.php?tid=129 david brady, '02 Wanderlodge LXi 'Smokey' (Sold), '04 Prevost H3 Vantare 'SpongeBob' "I don't like being wrong, but I really hate being right" |
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02-28-2013, 17:20
(This post was last modified: 02-28-2013 17:40 by pgchin.)
Post: #3
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RE: Generator Switch Box
Darrell,
David gave you excellent advice on troubleshooting the powertech. I have not seen this before on the bird BUT, I have elsewhere. If it were me, I'd do the resistance check David suggestion and if its good, then rewire again. Keep the AC unit that pegs leg 2 OFF and try and turn on a few things so you can get a 20-30 amp load on both legs, then see where you are at with the new wiring. The only other things I can think of for a SWAG would be the bearing is starting to go but there is no way to check that without tearing the head apart. Take a peak at the voltage regulator if you can and see what kind of shape it's in....... The AC unit that pegs the meter probably has a bad or weak start motor capacitor or the compressor is shot. I'm willing to bet your Blueberry farm on it! ![]() ![]() Pete and Donna Chin 95 42' WLWB On The Road Always! :-) " We'll raise up our glasses against evil forces singing, Whiskey for my men, and beer for my horses!"-Toby Keith & Willie Nelson - The bridge from Toby Keith's title album track "beer for my horses" |
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03-02-2013, 09:52
Post: #4
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RE: Generator Switch Box
(02-28-2013 17:20)pgchin Wrote: Darrell, More info on generator transfer switch. Thanks to you both for the insight and direction. Once again I ran all 3 AC's under load (had to set the thermostats at 40F) and observed the amp gages. During normal cycling of the AC's no current spiking was observed. The replacement 10 ga wire didn't get warm, no smell or smoke and my clamp-on amp meter agreed with the coaches. About 12amps per unit under load. If I manually start an individual unit while there is a demand in that zone I will see a prolonged spike on the meter of which ever leg that unit is wired to. I haven't had the guts to leave it on for more than 3 to 5 seconds and the 20amp breaker doesn't trip. This happens to all 3 units including the center unit which was replaced last spring. Yes indeed the transfer switch comes from the factory with 10ga wires between both sets of T1 and T3 terminals and one 6ga wire between the T2s (white neutral). The balance of the terminals were wired by BB with 6ga. Should there be some logic in the AC units or the thermostat that delays engaging the compressor until the motor has started? Why don't the breakers trip? I'm pretty sure this condition is what fried the earlier 10 ga wire. Nice to have the Aqua Hot last night, warm floors too! D |
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03-02-2013, 10:40
Post: #5
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RE: Generator Switch Box
Darrell,
We have different thermostats so we'll David to weigh in here as he has what you have. Two points though, I could never run 3 ac's on the generator. One would always overload the system and automaticity shut one down. When I manually start any of mine, the motor starts first pulling about five amps. Then about five minutes later, the compressor kicks in and a momentary spike of thirty amps happen and the system settles in at 12-15 amps steady state. Pete and Donna Chin 95 42' WLWB On The Road Always! :-) " We'll raise up our glasses against evil forces singing, Whiskey for my men, and beer for my horses!"-Toby Keith & Willie Nelson - The bridge from Toby Keith's title album track "beer for my horses" |
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03-02-2013, 10:59
Post: #6
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RE: Generator Switch Box
(03-02-2013 10:40)pgchin Wrote: Darrell, Good stuff Yours works like I think it should, except the overload condition. Motor starts fan only, compressor pulls in after delay with a little spike. Mine can be started under a load resulting in a locked rotor! Not good... D |
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03-02-2013, 11:27
(This post was last modified: 03-02-2013 11:32 by davidbrady.)
Post: #7
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RE: Generator Switch Box
Darrell,
The installation manual specs locked compressor inrush at 60A and locked fan motor at 6A. I don't think there's any delay built in to delay compressor startup. I believe this cause there are addons to dometics to insert delays. What are your leg voltages during compressor startup? If the genny is a weak voltage source then voltage will fall more than normal and inrush current will increase above those spec-ed in the manual. I think max inrush would occur only for the first half second or so and quickly disappear and be over within 3s (exponential decay). I have had no problems running three AC's on the genny. The manual specs a minimum generator capacity of 3.5KW per AC unit, so our 15KW units are easily adequate if operating normally. http://www.dometic.com/1f24ead8-6316-41b...6bad.fodoc david brady, '02 Wanderlodge LXi 'Smokey' (Sold), '04 Prevost H3 Vantare 'SpongeBob' "I don't like being wrong, but I really hate being right" |
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03-02-2013, 11:33
(This post was last modified: 03-02-2013 11:41 by pgchin.)
Post: #8
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RE: Generator Switch Box
(03-02-2013 10:59)Darrell Snell Wrote:OK,(03-02-2013 10:40)pgchin Wrote: Darrell, So I WAS SUPPOSED to be working out in my garage this am on other punch lists, BUT it is so cold, I decided to fire up the puter instead of the phone since I still type like an infant on that thing and kabbits with you guys! ![]() Duh, Just saw David's post after I wrote this, Thanks David!!!!! I knew you would have some insight!!!!! :-) Pete and Donna Chin 95 42' WLWB On The Road Always! :-) " We'll raise up our glasses against evil forces singing, Whiskey for my men, and beer for my horses!"-Toby Keith & Willie Nelson - The bridge from Toby Keith's title album track "beer for my horses" |
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03-02-2013, 11:48
Post: #9
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RE: Generator Switch Box
Pete,
My 96 will run all 3 on the genny. I've got to be a little careful, as the middle and rear are on leg 2, along with a bunch of other stuff. It's really easy to imbalance the two legs. But other than that, I have no issues with the A/C's. John Mace 06 450LXi bigger bird living in the wild hinterlands of the north free to roam without the man getting me down |
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03-02-2013, 11:53
Post: #10
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RE: Generator Switch Box
(03-02-2013 11:27)davidmbrady Wrote: Darrell,Thanks David I didn't realize the compressor and fan motors were not the same. I will check the voltage during startup in generator and shore power mode. D |
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