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voltage imbalance on Powertech 17.5
99 Royale with 1100 gen hours. Most of the time it works fine and shows about 115 volts per leg. Sometimes I can hear an a/c unit laboring to begin a compressor engagement. At the same time I can hear the generator loaded up. When I can get to the meters in time, it invariably shows 1 leg with low volts – maybe 100 volts, and high amps – maybe 30 or 40. The other leg is normal – 115 volts and no amp load. The loaded leg will struggle 5 or 10 seconds and then unload for a while, then try it again, usually the same results. Usually this happens in the middle of the night,so I don’t get to read the meter in time. It seems to have something to do with leg balance, occurring when one leg has no load. It has never happened with both legs loaded, but in the night the units cycle. It has rarely tripped what I assume is the automatic transfer switch – producing a loud slam and all a/c power going off for maybe 10 seconds, then resetting. The engine never dies or struggles, except when heavily loaded as described. It has never done anything like this on shore power, and on gen power it does not seem to happen more when heavily generating. If anything it is the opposite – one leg running an a/c unit and the other leg unloaded. Any ideas? If not, any shop or tech you can recommend? Thanks.
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7 Replies
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What do you mean by “The loaded leg will struggle 5 or 10 seconds and then unload for a while, then try it again, usually the same results”.
I would start by looking for a loose connection or bad breaker on the generator supply side that’s creating increased resistance.
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By unload, I mean that I believe the a/c unit resets due to low voltage and then tries again after 30 seconds or so.
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Had same problem on 17.5 powertech. Looked up online repair stations for Powertech and went in and Tech did ajustment in the control box in ten minutes.
Jeff and Lindsay
91 Marathon XL -
This sounds like a loose neutral on the generator side either in the generator panel or the ATS. I would get it to a tech immediately because losing a neutral is very dangerous and will destroy electronics in a hurry.
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That sounds hopeful. I have checked all connections I can think of, and oddly, it seems to happen more often under light load rather than heavy load. A heavy load, equally balanced, has never done it, making me think it is either in the generator or in the voltage protection system. Thanks. I will be needing a Powertech service center in SE Texas, Houston area if anyone can vouch for someone.
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A loose neutral would have one leg go very high voltage depending on what loads are on the two split phases.
Some voltage regulators only look at one side of the 240V split phase. This can have the other side of the split phase go low with very unbalanced loads. If this unbalanced load is a common scenario for you, it should be possible to switch the regulator over to the other leg to avoid it going low.
A simpler solution would be to just have some load on the other leg.
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Jeff with Powertech told me the generator was not the problem, that it was doing like every generator would do when one leg gets more load than the other. He told me to suspect the automatic transfer switch. I believe that my transfer switch hi/lo volts protection feature wascut failing. Below 100 volts and over 130 volts causes the switch to open to protect the electronics in the coach, and mine was cutting out somewhat earlier – maybe around 107 or so. Not all transfer switches protect in this way, but mine did. I replaced it with a Surgeguard 90 amp, and so far so good. I am looking at ways to keep some load on the other leg, as my problem usually occurred during the night when the only real load is the bedroom AC. I like it cold back there.
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