Lazy Daze Owners' Group

Campground Voltage Dropping

July 18, 2018, 10:02:14 am

Electrical mystery———  Recently I have had an issue with the incoming AC from campgrounds. The first time occurred in Labrador where the incoming voltage was 118vac. The campground had just completed a new camping area with the wiring according to local code. It was cold so we turned on the Dometic heat pump to get rid of the interior chill. Once the compressor came on the voltage began a steady slow decline to the point (around 105VAC) that the Progressive Industries Electrical Management System tripped to ‘Off’ to protect all the AC devices on the coach. The EMS is hardwired inside the coach next to the transfer switch reading the output of that switch. As the voltage was dropping the EMS display showed amperage draw was increasing while the compressor was running and the voltage dropping. Starting amp draw was 15A going up to 20A. The same occurred when using the Dometic microwave by itself.  I then ran the heat pump using the Onan generator AC power with no problem. Same with the microwave. I did try using a different power cord to the camp outlet with no change in operation.
   At another campground there was no problem running ether units. Then the same problem then occurred at another (KOA) campground in Newfoundland. I am glad we had the propane furnace as it was cold there.
   We then stayed at a Newfoundland friends house that had a 30A Rv  outlet at his garage where we have stayed in the past. From his main AC panel there is 4ga. wire 60’ to the sub main in the garage. From the 30A breaker there is 10ga. wire 30’ to the 30A outlet. Then the 10 ga. 30' cable to the LD. Thats it! Same identical problem. Resting voltage at the EMS is 120 @ 60hz.  Here we also checked the voltage with a multi-meter in the LD AC outlets which within a couple of volts matched the EMS reading. 
   My question to any of you electrical engineers out there is: What am I missing in solving this problem?

Re: Campground Voltage Dropping

Reply #2 – July 18, 2018, 11:22:18 am

Hi Mike, this sounds like a good time to mention that every year or so,  you should tighten up the wiring connections inside the power distribution box. Copper expands and contracts with the heating associated with current flow, and 'oozes' out of pinch points such as under the screw fittings in circuit breakers and distribution wiring. Larry has mentioned it a few times in past posts. Other more remote locations, like inside the EMS box, also have this creeping problem. The higher the current, the more temperature cycling, and more often this maintenance needs to be done. Left long enough, there have been fires that start in and around the high power distribution box, and its connections.    RonB

Re: Campground Voltage Dropping

Reply #4 – July 18, 2018, 04:04:50 pm

P = V x I, where P is power in watts, V = volts and I = amps.  If your load in watts is high (I don't know what you were drawing in total - converter to charge batteries, heat pump, lights, tv, etc.), your devices try to draw more amps as the voltage drops.  It can be a cycle that feeds on itself.

The first case, in the campground, might have been due to a lot of other campers drawing a lot of power, leading to a voltage drop at the pedestal.  Did you measure the voltage at the pedestal?  At the friends' house, you were running 60 feet of 10 gauge wire.  That is a lot, and may have contributed to voltage drop there.

The recommendations to check the plugs for corrosion, to torque the connections in the ATS and the power panel are good.  I suggest also checking voltage at the plug at your friends' house and in the rig while under load to see how much voltage loss you are getting from those 60 feet of cable.  As all was fine with the generator, I doubt that there is a problem with the heat pump or the microwave. 

Ken F in WY