The electrical subpanel in my garage is 100 amps. I found an unused circuit with a 20amp breaker and 10ga wire, which runs about 20' to an empty box on an exterior wall of the garage. I installed a 20amp outlet in the empty box, and run a 50' 12ga extension cord from the outlet to my coach, where I connect with a 15 to 50A adapter. This allows me to keep batteries charged and run low amperage fixtures/appliances.
First question:
My multimeter reads 117v at all of the outlets in the coach, but the Powerwatch panel on the wall shows 108v. Why the difference?
Question two: I read everywhere about voltage drop over distance when using extension cords, but I'm not seeing it when I measure with my multimeter. It reads 117 volts at the outlet in the garage, 117v at the far end of the extension cord, and 117v at all of the outlets inside the coach. In fact if I switch to a 100' 12ga extension cord, I get all the same readings. Does this mean that voltage drop related to cord length only appears when I put a load on the system?
Update: I just tested and when I turn the coffee maker on to heat water, voltage reading on the Powerwatch immediately drops from 108 to 103. And the microwave won't run at all, so I guess that answers my question.
Last question: If the wiring in the garage circuit is truly 10ga (and not smaller) I'm thinking I can replace the 20 amp breaker in the panel with a single pole 30 amp breaker, replace the 20 amp outlet on the side of the garage with a 30 amp 120v RV outlet, and run a 10ga extension cord instead of 12 from there to my RV. I still need to go 50' though, and connect through a 30 to 50A adapter at the coach, but with this setup I hope to be able to run one of my roof A/C units. Yes? No? Bad idea?
Not being a electrical X-pert, I will only try to answer your first question.
The PowerWatch analog volt meter is, IMO, a "rough estimate" instrument. I would not call it a precision volt meter. I'd believe your multimeter, if I was you.
I only use our PowerWatch to tell me "YES - 110V power is connected". Any questions beyond that and I'd break out my Fluke.
What do you have for a inverter/charger,is it possible you have a hybrid which would boost the voltage?
The bigger the wire the better. The more amps you draw the more voltage drop. With 10 gauge wire you can run a 30 amp breaker
Inverter/charger is turned off though.
Any chance to run your own Romex to a new outside outlet. You could then run #6 cable and still use a 30 amp RV outlet.
Another question is what else is on your 100 amp sub panel to be sure you are not near max when running 20-amps of coach power with roof air.
While #10 is rated at 30 amps, your long length from breaker to coach main breaker is pretty long.
And you passed your electrical test by learning about no-load vs load voltages. Higher the amps drawn, the lower the potential for voltage to drop.
You could also make your own outlet to coach cable by using #6 Romex with 30 amp male & female connectors.
Here in rural AZ, I ran a 20 amp circuit for my shore power but used a 50 amp outlet so I don't need any adapter to plug in my shore line.
Chris,
Wiring a 50-amp outlet on a lower amp circuit is a clever idea. And using your 50-amp motorhome shore cable eliminates any voltage drop on that length of cable.
Barry
Thank you Barry. I wish I had 50 amp service but a 50 amp outlet solved several problems. The voltage drop was one. The weight of the shore cable is also a problem (and a potential fire hazard) with both a 20 amp outlet and the plug of the adapter.