Newbie-type question about power supply at home

[profdant139]

Our trailer is in the driveway, and we are getting ready to have some remodeling work done on our house. We want to use the trailer as a "lifeboat" during construction. We have never done this during the summer (usually we are traveling!), so we will need the air conditioner.

My concern is that the garage (where we will be plugging in the trailer) is only on a 20 amp circuit breaker. I don't want to starve the trailer for power and possibly damage the air conditioner.

So here is my question -- if we have an electrician come out and install a 30 amp breaker on our panel, will that be adequate to allow us to plug the trailer into the garage outlet and run the air conditioner? (We will be using a very heavy duty extension cord.) Or do we also have to change the wiring and the outlets in the garage?

Thank you in advance for your expert commentary!

[profdant139]

More great tips!! It did not occur to me that the fridge drew so much power, but of course it does when not running on propane. I will keep my multimeter very handy when we are using the trailer as our "driveway lifeboat" during our upcoming home remodeling project.

(Personally, I predict that DW is going to get really tired of living right next to our construction project. But she says this is what she wants, so we will see how it goes. It ain't boondocking in the silence of the Eastern Sierra, though . . . . )

[wa8yxm]

First you can't just change the breaker.. The feed to the box has to be big enough to handle it.. And in this case I do not know. the box in my garage was 30 amps at 120/240 volt so it could handle it.. but.. I buried that line myself.

Second. MANY are the stories in these forums about people who had an electrician install a TT-30 for their RV and wound up with a disaster. The electrician wired it WRONG.

Better to have him install a 50 amp RV outlet. Those they get right. Now you can use 30 amp breakers (if the garage has the needed feed) but have him put in a 50 amp RV outlet and dogbone down to 30 for the rig if needed.

My 50 amp rv is mostly happy with 30 amps. In fact the generator is breakered at 30 amps times two legs.

[LittleBill]

at 117v, your perfectly fine, i personally have never seen a 15v swing in my life, but i guess it happens

for new construction, i doubht you will see a big fluctuation, i would check it a couple times, hottest day etc. i personally think your going to have 0 issue, that was a pretty minimal drop, just make sure the compressor was running and not just the fan, some units take a couple minutes for the compressor to fire up, but again if your over 108 nothing to be concerned about.

gl hope i saved you some money. remember your pretty close to max, Microwave/ water heater on electric/ coffee maker/toaster etc are all going to blow the breaker if the ac is on etc.. one big load at a time...

[Chum_lee]

Depending on where you get the power for your house, (power company) you can't always depend on getting a static voltage to your main panel. The voltage can go up and down in your neighborhood as well. (that can effect the voltage at your panel) After your AC has been running for a few hours, it would be a good idea to check the voltage at the input of your main panel and compare that to the voltage DROP you are seeing inside your RV.

That way you will KNOW the voltage drop from your panel to the RV which could be important as summer gets in full swing and the power demand in your neighborhood goes up. (the available voltage at your panel may go down) I've seen line voltages (from the power company) fluctuate at as much as 15 volts on a 120 volt nominal residential service.

Chum lee

[pianotuna]

117 under load is excellent.

Nothing will be damaged. You may want to check with the air and fridge both on.

Why? Because in the hotter time of summer the air conditioner may want more watts. Typically the Fridge is 325 watts--so that will tell you if there is any "wiggle room" on that (lovely) 20 amp circuit.

[time2roll]

117 is perfect. The compressor is actually rated 115 +- 10%

You are good to go 24/7/365

Down to at least 108 is fine long term.

[profdant139]

I just ran it for a half hour on maximum -- the plugs and cords were all cool to the touch. But right now the weather is fairly cool -- around 70 degrees. (Coastal Calif in June.)

July and August will get up into the mid 80s. Not terrible, but not pleasant without air conditioning, especially in a small trailer.

[Sandia_Man]

No issues @ 117 as it pertains to harmful effects on your AC unit running for prolonged periods of time. Our rig is always plugged in while stored in our side yard, we have run our AC unit a few times off of a 20 amp circuit with no issues.

We use plug in type voltmeters available from Amazon or Ebay, we readily know at any given moment our state of DC and AC voltages. Once in a blue moon I will drag out the Fluke DMM although it has been a few years since the last time, these plug in voltmeters are not Fluke accurate but close enough for every day usage.

[TurnThePage]

I used to do that, then come back later and see that the voltage had sagged down to 104 or 105 after an hour or two. I happily added a breaker and RV plug recently.

[2oldman]

117 is good. Check the plugs for heat every so often.

[profdant139]

Update (and a question) -- using a heavy duty extension cord and all of the tips above, I tested the voltage in the trailer, which was 119.5. And then I ran the air conditioner, and the voltage is 117.

Not perfect, but it works!!

So of course the follow-up question -- if I run the a/c at 117 volts for a long time, will that harm any of the components in the a/c system? I know that when running the a/c, I will not run any other major appliance (like the furnace or the toaster).

Thanks, as always!

[2oldman]

I used a 20a circuit with a 10 awg extension cord successfully.

[profdant139]

Thanks!! That totally makes sense -- it is the voltage inside the RV that is indicates whether the RV is getting enough juice.

[time2roll]

Check the voltage in the RV. Any outlet or right on the breaker... your call.

Just set the meter to AC. There is no polarity for checking voltage.