mumkin
Minot ND USA
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Joined: 07/16/2004
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I have a small C with an AC/Heat Pump combo described on the LTV website as a "Recessed Low Profile 13,500 BTU Ducted c/w Heat Pump." The rig is in storage and I can't recall the brand. (dometic?) I was parked in front of a relative's house plugged into their outside receptacle, so likely on a 15 amp. I had run the AC all day to keep the dog cool (it was only about 75 outside and partially shaded) with no problems.
But that evening, it was chilly and I thought I would run the heat for a cycle while I got ready for bed. The power went off, but I wasn't sure if it was from me... or something else. When they got up and went to work, they reset the power. It was cold, so I thought I'd try it again. Again it popped the circuit.
I had, BTW, used similar plugs at three other friends/relatives over the week, and it didn't happen at their houses. The fridge was on 110, but nothing else while the HP was running.
Perhaps they had a bad fuse or circuit or something, but what surprised me that I would have thought that AC pulls more power than heat. Was that an incorrect assumption on my part? Since the AC didn't pop the circuit, but the heat did... does the heat pump pull more power?
Just curious...
Mumkin
2011 LTV Libero
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ScottG
Bothell Wa.
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Joined: 02/25/2005
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Does the heat-pump have a back up 120V heater if it gets too cold for the heat-pump to be efficient? That might draw more power.
Just a guess.
Scott, Grace and Wesly
2003 Dodge 3500 4x4, 6 speed Cummins (lightly bombed),
2004 Forest River 25RKS many, many mods.
H0NDA eu2000i
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randrx2
Newport News, VA
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Joined: 03/26/2005
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There are way to many factors at play here.
- If the AC was on during the day, it may have not been that hot that the compressor had to work real hard.
- The distance between the breaker and the receptacle could have been greater causing a larger voltage drop than at the other houses.
- Possible older/faulty/worn breaker.
- There were other electrical loads on in the house on that circuit.
- Etc.
When someone says, "I'm not book smart, I'm street smart." All I hear is, "I'm not real smart, I'm imaginary smart."
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mumkin
Minot ND USA
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Yea... the "ect" always gets you. 
It wasn't cold enough to cause the system to switch to the propane furnace... that is the back-up. It was neither a horribly hot day or a freezing night. Typical Minnesota spring temps.
So... thus far no one thinks it is because of the difference in draw between the "Heat" and "Cool" of the unit.
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mumkin
Minot ND USA
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Joined: 07/16/2004
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duplicate...
but I could add that I don't think that there were any other draws. At night, they were in bed... and in the morning they had both left for work.
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chuggs
Florida
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A 15amp circuit is marginal at BEST for running a rooftop unit. You were lucky to get the a/c to work. Most a/c unit's that I've seen are on a 20amp circuit in the RV...this is with relatively short wire runs.
You have a few things working against you...
The circuit breaker in their house is now running pretty WARM you might say.
The 15amp circuit could have a long run of 14awg wire from their Load Center...to the wall receptacle...and thru your dogbone adapter. There will be a voltage drop...so when your a/c unit tries to work...it has to draw even more amps than it would if there were no voltage drop
It's evening...you're probably running a few 12v lights...maybe the converter has kicked up a level to keep up with the battery drains.
Maybe, as someone else pointed out, there is a heat strip to augment the heat pump at a certain temperature spread below set point.
Maybe you shut off the compressor and started it up too soon...not allowing the pressure to drop in the system before startup. This put more resistance on the compressor motor...so it draws more amperage.
My advice... 30amps 120v... and you'll be trouble free. (NOT THE 30amp 220v DRYER PLUG!) The problem is...you'll have to add a circuit like that.
I use my 15amp dogbone ONLY for keeping the battery charged. It might be able to run a vacuum cleaner... lights...television. But I wouldn't even attempt the air conditioner.
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Chris Bryant
DeLand, Florida, USA
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Joined: 03/26/2003
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Theoretically, the 2 modes draw the same current, but due things like coil sizes, air flow over coils, and temperatures, there will be differences.
-- Chris Bryant
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mumkin
Minot ND USA
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Joined: 07/16/2004
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This is at someone else's house so, I can't make them re-wire for my visit.
The A/C had been off for a few hours before I turned it on for heat.
And, as I said, I did this (ran the heat pump about the same amount of time - once before going to bed and once after getting up) at 4 homes this past week. At 3, there were no issues, but two power outs at the last one - same usage style.
Perhaps the other 3 had 20 amp circuits in the garage and the last had a 15. I'll have to ask them, but as I said... what struck me was that the AC was no problem, but the heat was. It wasn't really cold... mid 40s to mid 50's.
But, I guess I will never know...
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wwest
Redmond WA
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Are you certain it's a heat pump and not just an A/C with (more common) electrical resistance heating?
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mumkin
Minot ND USA
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Yup I'm sure... it's a heat pump. Makes the full rig toasty very quickly - much faster than the propane furnace. Heat strips are basically useless IMHO, but that may be because I am from North Dakota.
This is a rig manufactured in the cold prairies of Canada.
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