Voltage Question

[Keith K]

Need some advice from anyone knowledgable about electrical systems. We're currently volunteering in our motorhome at a wildlife refuge which only provides 30A power. I have a voltmeter that plugs into a wall socket and notice that many times when multiple appliances are running the voltage drops into the "red", reading as low as 102 volts. I haven't had any breakers pop but wonder if the A/C compressor or other systems can be damaged. Appreciate any advice.

[Keith K]

Need some advice from anyone knowledgable about electrical systems. We're currently volunteering in our motorhome at a wildlife refuge which only provides 30A power. I have a voltmeter that plugs into a wall socket and notice that many times when multiple appliances are running the voltage drops into the "red", reading as low as 102 volts. I haven't had any breakers pop but wonder if the A/C compressor or other systems can be damaged. Appreciate any advice.

[RV Wizard]

Keith, inductive loads, motor especially do not like long periods of low voltage or any periods of extreme low voltage. Make sure all of your connections are as tight and short as possible. Try self energy management methods too. If you want to heat up something in the mirowave turn off the air conditioner while doing so. You may want to concider an "AutoFormer", this is a device that can boost the voltage if it is a continuing and persistant problem. Good luck.

[barth]

I have a diesel pusher with a diesel generator. When I try to start the GENerator or use the HWH levelers all it does is click. When I push the AUX start switch every thing works.I f ound that after generator is running and I try to use the jacks it kills the generator.If plugged into 110 AC every thing works.all batteries check out good,connections clean and tight. All lights /pump/heator /furnace/ works fine on 12 volts not being plugged into 110 AC. BARTH

["007"]

Barth, check you ground wire for GEN to frame of coach in fact check all gnd's convertor, battery's to the frame or a common gnd post location. May have a dirty or loose connection use star washers to keep from becoming loose. "007"

[alvinc]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Keith Krejci:
I have a voltmeter that plugs into a wall socket and notice that many times when multiple appliances are running the voltage drops into the "red", reading as low as 102 volts. I haven't had any breakers pop but wonder if the A/C compressor or other systems can be damaged. </div></BLOCKQUOTE>The Air Conditioning motors are most at risk, as RV Wizard describes. The AutoFormer would certainly help, but I have to wonder about the wiring of the 30 amp circuit. A properly fused and wired circuit should not have a 15 volt drop. By properly wired, I mean the correct wire gauge for the distance it covers. The general rule is that 10g is large enough (3% drop) for 30 amps, but only to 50 ft. At 50 feet you need 8g, at 100 ft 6g, 150 ft 4g, etc. I suspect the service is underwired, which also means it is heating up.

The autoformer will help but it will cause an even higher current draw in order to boost the voltage.

What would I do? Install the autoformer and then manage the loads. For example, don't try to run both AC's and the microwave at the same time. Maybe run only one AC when cooking.

[Keith K]

Thanks guys for the information. Alvin, I suspect you're right about the wiring, we're full timers, have been on 30A often and I've never experienced such a big drop in voltage. I don't believe the autoformer's the answer if it is the wiring; I'll try and teach my wife power management........that should be fun. Any idea of the danger area of low voltage; for example is 105 volts going to hurt the compressor or is this pretty much a guess depending on the quality of the motor?

[Gary RVRoamer]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Any idea of the danger area of low voltage; for example is 105 volts going to hurt the compressor or is this pretty much a guess depending on the quality of the motor? </div></BLOCKQUOTE>

The generally accepted minimum voltage for any motor is 106 (and a max of 128). That's based on the voltage specs for AC power generation, which is 117 VAC plus or minus 10%. Any alternating current electrical device is supposed to be able to function reliably within that range. A better quality motor may survive longer or with less complaining, but quality is not really the issue here. It's more a matter of the design tradeoffs used by the electrical engineer who designed the motor and the tolerances of the components used when it was built.

As the voltage drops, the current (amperes) needed to produce the necessary power goes up. More amps produces more heat, which at some point to cause internal failure. Most motors will run for short periods at low volatge & high amps, but longer periods are almost sure to cause damage and outright failure. Some motors may have low voltage or thermal cut-outs (internal circuit breakers) that protect them from failure.

[barth]

007 you were wright on the money. The grounds all looked good at the battereys but they were corroded at the frame.Ive been in the auto busines for 42 years and run across this sort of thing many times.I guess I,am getting forgetful working on my own stuf.a little thing like a ground can drive you crazy. Thanks so much for your reply. Barth

[Keith K]

Alvin, you were right on the money. After reading your post I asked that a professional electrician look at the wiring; sure enough, it was too small a gauge. As a result, they're rewiring the post for 50A. Thanks!