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Thursday, October 16, 2014

RV Generator Over-Voltage

Doc, I recently went to exercise my RV generator and I was surprised when at about 5 minutes after turning on the generator I saw the voltage meter running at about 160-volts and it suddenly sparked but kept functioning. We turned on the AC and all the lights, although one blew. It looked to be to bright. Even with everything on the RV on it brought the voltage down to about 140-volts. I am assuming this is not a good thing and possibly dangerous. I thought it was supposed to be around 120. Can you tell me how this happens? It was running fine before I took the RV to have it serviced. A belt was squeaking and they repaired that but now I have a problem with the generator. Also you advise not running any equipment while the generator is putting out this much electricity. Unfortunately I have run my AC's while it was doing this. They seemed to run fine. But since I have done it is there some maintenance step I should take at this point for them? Again thanks for your assistance. Dale V., (Nashville, TN)

Dale, there are a few reasons why any generator may get out of adjustment depending on the condition of the unit, the number of hours, etc. It’s always been a good idea to have the generator tested annually using a load bank. The load bank device can monitor the voltage (carburetor) and the frequency (governor) as incremental loads (amperage) are placed on the generator. It’s possible someone tried to adjust the generator engine by ear or by sensing how smooth it runs, etc. I mention this fact in my articles, videos and in my seminars, but ANY mechanical adjustment done to the generator has a predictable electrical result. That’s exactly why a tech cannot tune a generator by ear.

Normal wear, carbon buildup, poor quality fuel, bumps and vibrations, etc., can all affect these finer adjustments. Combined, they create the reasons why it’s important to have the RV generator attached to a load bank... I say every year, but no less than once every two years.

If your air conditioners survived 140-volts AC for a long duration, you were quite lucky! Roof A/Cs are quite susceptible to very high and very low voltages. There’s nothing to check on the A/C units if they operate properly on shore power. If they operate correctly on shore power, no damage was done. Also, by connecting to shore power you can check all other AC system components to see if any were damaged by the high voltage. But be sure to have the voltage and frequency checked on the generator by a specialist equipped with the proper diagnostic testers before relying on it. The safe spectrum for AC electricity, (by any source), is 120-volts AC, +/- 5%. 

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