50 amp versus 30 amp

belfert · November 03, 2013, 10:59:50 AM

Quote from: luvrbus on November 03, 2013, 09:41:36 AM
He also said he could run 2 off 30 amps in another post Len I want to know how he does it the only way I see that happening here in the summer is 1 at time

Clifford, do I need to fly you up here next summer to prove to you I can run two 15,000 BTU rooftops off of a 30 amp service? I've been doing it for 6 or 7 summers now. It typically never gets over 95 degrees here and it is usually more like low to mid 80s. If I was in Arizona it might not work, but I'm not in Arizona. I can't run anything else off the 30 amp circuit at the same time. I've tripped the breaker more than once by trying to run too much at the same time.

I installed a 30 amp service back when I had my travel trailer and I don't want to upgrade so I make do with it. The time and money to install a 50 amp service just isn't worth it to me. I only installed 1/2" conduit so I would have to replace the conduit. I never imagined I would ever have a 50 amp RV when I installed the electrical.

Scott & Heather · November 04, 2013, 06:56:15 PM

I also don't know how you guys are running two roof airs off 30 amps. :-/ explain me!?

Sent from my iPhone using Tapatalk. Clumsy fingers may contribute to mistakes.

TomC · November 04, 2013, 10:02:27 PM

I was just at the Happy Traveler RV Park in Palm Springs, Ca. The RV park had just rewired all the power poles and had not upgraded the circuit breakers yet. They were still at 30amps. So I used one leg of 30amp and did run 2-roof airs in the middle of the day. Just made sure all other items were turned off.

One thing that I found that really helps on a hot day (my breaker boxes are inside the bus) is the computer cooling fan I installed in the power cabinet. It keeps cool air circulating through the box and really helps keeping the breakers from blowing.

When I wired the bus, it was just easier to keep all service at single 120vac instead of trying to split the service. Good Luck TomC

Midwilshire · November 05, 2013, 12:14:29 AM

Quote from: TomC on November 04, 2013, 10:02:27 PM
When I wired the bus, it was just easier to keep all service at single 120vac instead of trying to split the service. Good Luck TomC

Good idea with the computer fans; I think I'll copy that.

Why was it easier to keep your service at single 120vac? Isn't running 50 amp service just a matter of running one extra wire from your service entrance to the inverter, and one extra wire from the inverter to the main breaker panel, where the two hots power two separate bus bars? All of the breaker panels I'm finding at the home stores seem to be set up for this by default, which was what made me think of changing our design to 50 amp. And when you roll up to a 30 amp pole, a $20 dogbone connector energizes both hot legs of the bus off the single hot wire in the pole. Is there something additional that I'm missing (which is very possible)?

Scott & Heather · November 05, 2013, 04:00:17 AM

Quote from: Midwilshire on November 05, 2013, 12:14:29 AM
Good idea with the computer fans; I think I'll copy that.

Why was it easier to keep your service at single 120vac? Isn't running 50 amp service just a matter of running one extra wire from your service entrance to the inverter, and one extra wire from the inverter to the main breaker panel, where the two hots power two separate bus bars? All of the breaker panels I'm finding at the home stores seem to be set up for this by default, which was what made me think of changing our design to 50 amp. And when you roll up to a 30 amp pole, a $20 dogbone connector energizes both hot legs of the bus off the single hot wire in the pole. Is there something additional that I'm missing (which is very possible)?

This is how ours is wired. And the dog bone works just fine when on 30amp.

Sent from my iPhone using Tapatalk. Clumsy fingers may contribute to mistakes.

Oonrahnjay · November 05, 2013, 05:34:36 AM

Quote from: Scott Bennett on November 05, 2013, 04:00:17 AMThis is how ours is wired. And the dog bone works just fine when on 30amp.

And with a $5 adapter, it works OK for times when the only thing around is a 15A 120V socket. Of course, you have to be careful with how much you draw, but if you don't have to have A/C right then and you just want to keep your house batteries charged for a day or two, it's useful.

robertglines1 · November 05, 2013, 05:56:05 AM

When running on the edge of max amp available and you make a mechanical connection (adapter) I was taught to allow for as much as a 10% drop for each. Old school prob not correct. Still think go for 50 and settle for 30 if that is all there is. Airconditioners get old and require a few more amp to start then what?

luvrbus · November 05, 2013, 06:09:11 AM

You could probably run 2 -13,500 ac off 30 amps if you started 1 let it run and settle out then start the other but if one kicks out and tries to start you are dead in water

The Rv manufactures never try and run 2 ac units off a 30 amp service they all have some type switch to run 1 at a time I think all motor homes have a 50 amp service since around 1996 even with only 1 ac

LOL Belfert running AC's at 95 degrees what a pansy here that would be a sweat shirt weather

belfert · November 05, 2013, 06:31:17 AM

Humidity is the reason to run air conditioners here in Minnesota. I was more comfortable outside in the very dry 105 degree heat in Nevada this summer than I would have been at home at 85 to 90 degrees. I do nothing special to get two 15,000 BTU A/C units to work on my 30 amp connection at home. I turn one on and then walk over to the other one and turn it on too. I suppose the short delay might be enough to get by the initial surge.

luvrbus · November 05, 2013, 06:38:54 AM

I was looking for one of Nick's old post about the the draw and starting of roof top AC's and the amp factor as the temp goes up but cannot find it here it maybe on the BNO

eagle19952 · November 05, 2013, 07:54:32 AM

Quote from: TomC on November 04, 2013, 10:02:27 PM
One thing that I found that really helps on a hot day (my breaker boxes are inside the bus) is the computer cooling fan I installed in the power cabinet. It keeps cool air circulating through the box and really helps keeping the breakers from blowing.
Good Luck TomC

Why would you suggest this....the breaker is designed to trip at a certain temperature....and you are artificially defeating it...I think that is a code no-no...

Oonrahnjay · November 05, 2013, 07:56:00 AM

Quote from: luvrbus on November 05, 2013, 06:38:54 AMI was looking for one of Nick's old post about the the draw and starting of roof top AC's and the amp factor as the temp goes up but cannot find it here it maybe on the BNO

Clifford, dunno exactly how much this tells us but Coleman lists the following for the low-profile (for instance) Mach 8 units --

Unit 13.5KBTU AC 13.5K Heat Pump 15KBTU AC 15KBTU Heat Pump
Watts ARI 1599 1647 1671 1657
"Desert"* 1913 1946 1995 2017

Another manufacturer quotes "ARI" at 80 deg F. (but others seem to reference 90); Coleman quotes Desert as being 120 degrees. So, just as a guess, I'd say that going from ARI standard to desert results in about a 20% increase in amp draw.

eagle19952 · November 05, 2013, 08:02:44 AM

Quote from: Oonrahnjay on November 05, 2013, 05:34:36 AM
And with a $5 adapter, it works OK for times when the only thing around is a 15A 120V socket. Of course, you have to be careful with how much you draw, but if you don't have to have A/C right then and you just want to keep your house batteries charged for a day or two, it's useful.

A decent Inverter Charger requires more than a 15 amp circuit, by a bunch. Running that little $5 adapter through many feet of 10 ga. wire makes the $5 apapter a fire/smoke hazard.....
My inverter/charger is on a 30 amp breaker.

Oonrahnjay · November 05, 2013, 08:07:48 AM

Quote from: eagle19952 on November 05, 2013, 08:02:44 AMA decent Inverter Charger requires more than a 15 amp circuit, by a bunch. Running that little $5 adapter through many feet of 10 ga. wire makes the $5 apapter a fire/smoke hazard..... My inverter/charger is on a 30 amp breaker.

Yes, I only use mine for "float charging" batteries that are already up and set the max current draw on the inverter to 12Amp (@120V). I don't use it if the batteries are low and require heavy charge or if I'm using other 120V loads. It's not for all circumstances but it's a tool that's useful sometimes.

luvrbus · November 05, 2013, 08:42:45 AM

Thanks Bruce that is what I am saying at 1995 watts 2 units won't run off a 30 amp service and the amps go up or down by the voltage a unit drawing 16 amps @ 120 volts will draw 18@ 110v and the temps the manufactures use are ambient temps that don't cut it on a metal roof on a bus.

I don't know how they run 2 roof tops off a 30 amp service it's a mystery to me anyway it doesn't happen here in the sun