Roof top A/C and heat pump

[frecku]

Planning on replacing my 15,000 BTU A/C, came across a Dometic unit with a "heat pump".
How does this technology work, are they as efficient as the forced air propane heaters ?
How much amps do they draw ?
I have a vented system A/C so I presume with a replacement heat pump A/C unit the hot air would be directed out the ceiling cooling vents, how efficient can that be ?

[frecku]

Thanks again for the great examples. 🙂

[Rolin]

We purchased a used MH which had the heat pump option.

Pro's:1. Doesn't require a space heater which takes valuable room to store.
Con's: 1. Our ducted heat pump makes too much noise..same as running the AC, 2. Takes the same amount of power as running the AC, 3. The butane furnace heats the unit up much faster in the morning.

It has a cool feature....on ours you set the thermostat to heat pump and it monitors the outside air temp and if the temp drops to a certain point it will automatically switch from heat pump to the propane furnace and or back to heat pump.

We prefer the electric space heater as it is quieter and that radiant heat blowing on you feels warmer on chilly mornings. When boondocking we plan to use a small catalytic heater.....no power required.

Personal opinion: I would not pay for the heat pump option if I were buying new

[tatest]

I use my Coleman Mach 15,000 BTU/hr heat pump for most of my heating needs March and April, September through November outings in this part of the country.

It puts out air about 20F warmer than it takes in, so if thermostat is set for maintaining house temperature about 70F, you heat with a larger volume of warm (about 90F) air from above, rather than a smaller volume of hot (120-150F) air delivered at floor level.

The noise is no greater heating than cooling, and in my bedroom with ducted air, I find the furnace and heat pump equally annoying, either will wake me when cycling on.

Efficiency? Measuring BTUs in fuel burned, a RV propane furnace delivers 70-80% of the heat to the interior of the RV (used to be as low as 60% in older furnaces).

Electric resistance heat is 100% efficient if you measure KWH you buy to BTU delivered to interior. A heat pump is usually 200% to 300% efficient, by that measure, thus it can deliver at least twice as much heat from the same power, compared to a resistance heater.

How that measures against propane, BTUs for fuel burned, depends on efficiency at the electric power plant and transmission losses bringing the power to you. Your fuel burning power source may be less than 70% efficient (especially your RV generator at about 20-25%) or it may burn no fuel at all if wind power or hydro. Figuring out fuel efficiency of an electrical device is pointless if you have no control over how the power is generated and how far it is transmitted.

[Dakzuki]

snowdance wrote:

eric1514 wrote:
However...a heat pump will require that you are plugged into shore power whereas your furnace needs only 12 volt. Personally, if I'm getting 120v power, I'm plugging in a virtually silent space heater instead of listening to the AC/Heat pump.

Eric

X2 hate all the AC noise when not needed..

Me too. Heat pump was an option I passed on due to the noise.

[Altern]

eric1514 wrote:
However...a heat pump will require that you are plugged into shore power

A heat pump will also operate with power from your generator - yes, in both heating and/or cooling mode.

[GrumpyandGrandm]

I switched our's for the heat-pump as well and love it. We also use space heaters (have the one that looks like a fireplace "atmosphere to boot") so we are bacically all electric. We don't mind the fan noise and I think it helps circulate the heat better since the return pulls the warm air off the ceiling. We have the Coleman and it also has the heat strip built in for when the temp dips too low for the heat pump (not as efficient but it still helps).

[snowdance]

eric1514 wrote:
However...a heat pump will require that you are plugged into shore power whereas your furnace needs only 12 volt. Personally, if I'm getting 120v power, I'm plugging in a virtually silent space heater instead of listening to the AC/Heat pump.

Eric

X2 hate all the AC noise when not needed..

[eric1514]

However...a heat pump will require that you are plugged into shore power whereas your furnace needs only 12 volt. Personally, if I'm getting 120v power, I'm plugging in a virtually silent space heater instead of listening to the AC/Heat pump.

Eric

[frecku]

Thanks for all the info.

[Altern]

pianotuna wrote:
A heat pump is nothing more than a refrigerator running "backwards".

Said a bit differently - A heat pump is nothing more than an air conditioner with the capability to reverse its flow of refrigerant thereby providing either heat or cooling whichever is desired.

Here's a little VIDEO for further explanation.

[Frosty_s_Mom]

while it's true you can't use a heat pump much below 40 degrees, we use ours very effectively when it starts getting really cool. love the savings on the propane tank; extending the propane usage. I haven't done any comparison in costs, but if you are paying for an RV space which includes electric, you are getting it included w/o spending the propane; another good thing.

[pianotuna]

Hi,

A heat pump is nothing more than a refrigerator running "backwards". They draw the same number of amps as the air conditioner does when it is set in cooling mode. Because it is extracting heat from the environment if you compare it to an equivalent size resistance heater, and the outside air temperature is not lower than about 40 F they "produce" somewhere between 2 and 2.5 as many btu's for the identical number of watts.

If and when my air conditioner dies, I will be considering a heat pump as an upgrade.

I've already "broken out" my furnace control from the OEM Dometic thermostat--so I can run the heat strip and the propane furnace at the same time.

[Mandalay_Parr]

They have an internal freon reversing valve. The air flow remains the same.