TXiceman
(Near) Houston,TX
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Joined: 11/17/2000
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All an A/C does is remove heat from one place and move to another location. In the case of the A/C it absorbs the heat in the conditioned space and rejects it out side.
For a heat pump, there is a reversing valve that swaps the evaporator fro the condenser as far as the compressor is concerned. Now it absorbs the heat from the outside air and rejects it to the interior.
With outside air, the lower the temperature, the less it heat it has available to give up and once you reach about 35 to 40dF outside, the heat pump does not perform well. The coil evaporator will start to freeze and have to be defrosted often. So, the manufacturers go to a heat strip or other external direct heat source.
The heat given off from a heat pump is fairly low in temperature when compared to a standard heater. Some folks complain of a draft due to the lower quality heat.
They work fine down to about 40 dF.
Ken
KE5DFR
Vintage 1979 Silver Streak Supreme Rocket toted by a 2002 F350, crewcab dually, 7.3L,4.10 axle,SCMT. Travel with two miniature Schnauzers and one African Gray parrot. Practicing for retirement!
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PackerBacker
Home is Montreal Qc & Seasonal is NY Adirondacks
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Joined: 08/22/2002
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I have two Carrier heat pumps and really like them. They're great for those damp cool mornings to get the chill out.
Eric
2009 Holiday Rambler Admiral 33SFS (34' 3")
2008 Jeep Liberty - North Edition
FQCC/Camping Quebec, KOA, Good Sam, Coach-Net
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Johno02
Lexington, TN USA
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Joined: 10/15/2004
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We have had several heat pumps in Tennessee, Mid-Kentucky and Annapolis MD. Correctly installed heat pumps are very good and very efficient. Note the word CORRECTLY. Ductwork designed and installed for an AC generally is not insulated well enough, and cannot carry the volume of air required for a heat pump. As the heatpump does not heat air as hot, it requires more airflow to provide the same heat BTUs.
Noel and Betty Johnson
'99 Hurricane 2007 HHR 1 wife, 2 1/2 dogs
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pnichols
Santa Cruz Mountains
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Joined: 04/26/2005
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"Heat pumps units will not accomodate a heat strip."
This MAY be true for some or all RV air conditioner/heat pump combinations - I'm not sure. We've had an air conditioner/heat pump unit (AKA an "air conditioner that can run in reverse") in our residence - as our ONLY source of cooling and heating - for over 30 years and it has two stages of heat strips thermostatically controlled to kick in one or both stages for BTU boost depending upon how low outside temperatures get such that it's air-to-air heat pump mode no longer can work well.
I see no reason why an RV air conditioner/heat pump unit couldn't also include heat strips - other than it would require two separate 15 amp circuits feeding the unit so as to run both the compressor (for heat pump processing) and 1500W heat strip (for boost) at the same time.
By the way using a 110V, 15 amp, powered air conditioner/heat pump in an RV invalidates the axiom many quote to the affect that "1500 watts provides about 5000 BTU's of heat and there is no way around it". This statement is only true when using electrical power to create new heat. A heat pump can provide well beyond 5000 BTU's of heat to an RV's inderior from it's ~1500 watt 110V input .... because it merely transfers existing heat from the outside into the interior .... it does not create new heat. For situations where it's not super cold outside (below about ~35-40 degrees), it's a far more efficient use of (the Earth's) resources to heat your rig with a heat pump (and it's heat strips not on) instead of with a standard electric heater.
That's assuming you can get the warm air from the heat pump circulated down low in your rig - which is difficult with a ceiling mounted and ducted air conditioner/heat pump. If this problem is dealt with adequately, then it seems to me that an RV with an air conditioner/heat pump with heat strips - plus a conventional propane furnace - would indeed be a rig with a very versatile and flexible setup for interior temperature (and humidity) control.
Phil, 2005 E450 Itasca 324V Spirit
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Bumpyroad
Virginia
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Joined: 12/01/2005
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pnichols wrote:"Heat pumps units will not accomodate a heat strip."
This MAY be true for some or all RV air conditioner/heat pump combinations - I'm not sure. We've had an air conditioner/heat pump unit (AKA an "air conditioner that can run in reverse") in our residence - as our ONLY source of cooling and heating - for over 30 years and it has two stages of heat strips thermostatically controlled to kick in one or both stages for BTU boost depending upon how low outside temperatures get such that it's air-to-air heat pump mode no longer can work well.
you are really referring to the back up heat elements that all heat pumps in northern climes have, some do have gas back up heat however. in any event, in the house they are 30 brazillion amp powered whereas in a RV the heat strips are just the standard 1500 watt or thereabouts.
bumpy
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dougrainer
Carrolton, Texas
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Joined: 06/11/2007
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pnichols wrote:"Heat pumps units will not accomodate a heat strip."
This MAY be true for some or all RV air conditioner/heat pump combinations - I'm not sure. We've had an air conditioner/heat pump unit (AKA an "air conditioner that can run in reverse") in our residence - as our ONLY source of cooling and heating - for over 30 years and it has two stages of heat strips thermostatically controlled to kick in one or both stages for BTU boost depending upon how low outside temperatures get such that it's air-to-air heat pump mode no longer can work well.
I see no reason why an RV air conditioner/heat pump unit couldn't also include heat strips - other than it would require two separate 15 amp circuits feeding the unit so as to run both the compressor (for heat pump processing) and 1500W heat strip (for boost) at the same time.
Well I AM sure as I install and repair RV AC/Heat Pumps for a living. The reason they do not have Heat Strips is simple- The AC controls use some of the heat strip connections for the Heat Pump system and there is NO REASON to have a Heat Strip on a Heat Pump since they all have either Hydronic or Furnace system on board for sub freezing temps. The reason for a Electric heat coil on Home heat Pump systems is for Heat when it stays below freezing and the Heat Pump cannot get the BTU's of heat out of the air. You COULD probably install a Heat Strip (rewire the system), but WHY?? The Heat Pump mode puts out more heat. Doug
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pnichols
Santa Cruz Mountains
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Joined: 04/26/2005
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".. there is NO REASON to have a Heat Strip on a Heat Pump since they all have either Hydronic or Furnace system on board for sub freezing temps."
If you have hookups or have a dry camp generator running .... why use either your own propane or excessive generator fuel? If temperatures are 40 degrees on up, an RV heat pump is the least expensive electrical way to heat since you are not making new heat. If for some unfortunate/emergency reason when dry camping in 40 degrees on up temperatures you are forced to get some heat into your RV for awhile using a generator, it will use less fuel powering a heat pump then it would by creating new heat from only a standard electric heater to get the same BTU's.
For marginally lower temperatures - say 35 to 40 degrees - getting some heat out of an RV's heat pump plus installed heat strips in it will STILL take less hookup or generator power than through only use of standard electrical heaters.
"The reason for a Electric heat coil on Home heat Pump systems is for Heat when it stays below freezing and the Heat Pump cannot get the BTU's of heat out of the air."
As I said, my home system has two heat strip stages. On the first stage the home is getting heated some by the heat pump and some by the first stage electrical heating elements. This is less expensive than no heat pump at all.
This reasoning also applies to an RV heat pump being supplemented/helped in the 35 to 40 degree range by 5000+ BTU's coming from it's heat strip.
"The Heat Pump mode puts out more heat."
Not in the 35 to 40 degree range - in heat pump mode you would get SOME BTU"s but not enough. Heat strips would provide 5000+ BTU's additional.
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Duck
Miami Lakes, Fl
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Joined: 03/04/2001
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We have the heat pump in our RV. Works great down to around 42 degrees and saves a lot of expensive propane. We will also use a couple of small electric space heaters that help a lot. When the temps get below 40 degrees we have to kick in the propane heater instead of the heat pump part of the a/c.
Don
08-FORD F350 PSD
08-Hitchhiker II 34.5 UKSBG
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Charlie D.
Gonzales, La.
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Joined: 09/12/2006
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Got a heat pump in my house and really like it. Has back up heat strips in the air ducting for back up if compressor fails. The unit does not have heat strips to help defrost it. When it is too cold outside, the condensor will ice up but the compressor momentarily switches back to cooling. In doing so, the high pressure line gets hot and recirculates back through the condensor. It very quickly defrosts the coils and then switches back to heat. Kinda scary if you are watching it. Looks like a lot of smoke coming from the unit.
If anyone has a heat pump, check the line outside when running. I have not checked the actual temperature but you will very quickly let go of it. Runs much hotter than the high pressure line during cooling.
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MrWizard
Van Nuys, Ca
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Joined: 06/27/2004
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Luvs2Camp wrote:On the thermostat, it has Heat Strip and Cool. How do I get it to bring heat into the camper? When I ust the heat strip, it is not very much heat and we still have to use the gas furnace to warm the place.
thats strange, because your temps & latitude is about the same as mine, here in southern Calif, and my heat strip will warm my 30ft RV up real nice, i don't use it to much, maybe some in the morning when making coffee, because we full time dry camp and use a generator for 120v power
for me Propane is cheapest way to heat. although i'm going to buy one of these for backup heat & outdoor use
portable Butane heater
it uses the same 8oz butane canisters as our single burner camp stove
Options, always have options, and the journey goes much smoother
....
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