Will 2nd air cond (bedroom) run when plugged in to a 30 amp service

sandrattt

Member
I have been told that when a RV has 50 amp service, one branch feeds the 2nd (13,500) a/c only, and the other branch feeds the rest of the trailer including the main a/c unit. Is this true? What I want to do is use a 4 prong-3 prong adapter to plug the 50amp cable into my 3000 watt generator. I don't think the generator will reliably run the 15,000 main a/c hence I want to run only the small a/c. Will this work? Or will the trailer wiring not allow me to feed the bedroom a/c when plugged into a 3 prong 30 amp service?
 

Rickhansen

Well-known member
Not true. I can't verify how the loads are distributed on the two breaker panel bus bars in your rig. The limitation is the power that is available to your coach. The second 50 amp leg feeds more than simply the second A/C.

I have read posts on this forum that there are 50A to 30A adapters that do not feed the second leg at all, in which case half of your rig will have no power at all, although that would be uncommon.

With 30 amp service you have 3,600 watts (120*30), whereas with 50 amp service you have 12,000 watts (120*50*2). If you try to run both A/C's at the same time (or any combination of loads exceeding 30 amps), you will trip your breaker on the 30 amp circuit.
 

hoefler

Well-known member
Yes. As long as you use a 50 amp - 30 amp adapter, not the so called 50 amp cheater that you plug into a 20 amp and a 30 amp at the same time, you will have power to everything that is 110 volt, you may not be able to run everything, but it will have power. You should be able to run your main A/C as it runs on a 20 amp circuit. Your generator is capable of 25 amp total ( 3000 w / 120 v = 25 a ), provided that is the running output and not the surge output.
 

TXBobcat

Fulltime
You can run either AC on a 30amp power. When I have to connect to a 30a power source I take my Hot Water heater off of electric and run it on propane. If I am going to stay at the location for a long time I turn the HW heater off until I want to use it and then run it on propane. If necessary I take my Reifer off electric and on propane. You might be able to run both AC's if you turn off all other electrical appliances.

I do this when I am running on my paralleled Honda 2000's.

BC
 

newbie

Northern Virginia
Those cheater plugs have both legs bonded together inside the plug. Your whole coach is run off the same 120 volt leg. You can get both air conditioners to start and run in a perfect world. The problem is when the park service voltage is running low and/or the temperatures are really high you may not be able to get the second unit to start and stay on.

If your running on generator, that's when the so called "peak amps" or "max output" is needed. On really hot days the second unit will have an extremely high amp draw for the first second or so at start up.

John
 

back2nature

Well-known member
You can run either AC on a 30amp power. When I have to connect to a 30a power source I take my Hot Water heater off of electric and run it on propane. If I am going to stay at the location for a long time I turn the HW heater off until I want to use it and then run it on propane. If necessary I take my Reifer off electric and on propane. You might be able to run both AC's if you turn off all other electrical appliances.

I do this when I am running on my paralleled Honda 2000's.

BC

Bobcat, do you have anyway way of knowing how much propane the refrig would use? Especially, the new big 4-door one? Probably, no way to measure it, but do you think it would "gulp" the propane down or a "slow-sip"? Like how many days?
 

Nabo

Southeast Region Director-Retired
We stay at state parks which only have 30 amp service with our 50 amp rig and run both units all day in upper 80/low 90 degree weather (beach). Running both units pull about 26 amps, therefore you can not run alot of other electric appliance at the same time. We use the hot water heater only on propane, turning it on just before needing hot water and then turning it back off. The refrig runs on propane during the hottest part of the day and then I put it on electricity about bedtime. If the need for coffee pot, microwave or anything that pulls more amps, I turn off the bedroom unit until I'm finished with those appliances. Object of the game is stretching the amps.
 
B

bwwalczak

Guest
Great posts. NABO just summed it up - it is all about AMP usage. Devide watts by 120 and this should give you a AMP range. So 3000 watt gen (probably peak) should generate (in theory) around 25 AMPS. Then count up the amps needed / used. A/C's (individually) draw about 12amps each. Converter should draw around 8 amps. (these numbers are ranges).

Everything will draw amps when on the 110V electric system. Items on 12V will run through the converter which is already drawing AMPS.

Key is to add up your amp draw - the secret to power managment.

Local dealers can provide you a list of how 110V/12V systems operate. Dealers are your best resource when analyzing. Hope this post helps.
 

hoefler

Well-known member
QUOTE=bwwalczak;148158]Great posts. NAB just summed it up - it is all about AMP usage. Devide watts by 120 and this should give you a AMP range. So 3000 watt gen (probably peak) should generate (in theory) around 25 AMPS. Then count up the amps needed / used. A/C's (individually) draw about 12amps each. Converter should draw around 8 amps. (these numbers are ranges).[/QUOTE]

That is A/C running draw, start up draw can double. If it is running and you turn something else on, it may be OK. But if it cycles off and tries to come back on, you may not have enough unused amperage left to start it again with other things like a coffee pot on.
 
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