Heat Pump

Question>: I was reading your Winter Un-Wonderland page, and wanted to make a post about heating. I am looking into buying a heat pump with AC which

Heat Pump

by Shannon

Question>: I was reading your Winter
page, and wanted to make a post about heating. I am looking into buying a heat pump with AC which is at least 2 to 3 times more efficient than a standard electric heater (any electric heater).

However, one big issue to me is the RV AC/Heat pump manufacturers – Atwood and Dometic – won’t tell me how efficient they are. I have inquired with Dometic and Atwood for a few weeks now and they state that the Coefficient of Performance (COP) data is “unavailable”.

In contrast other manufacturers give you COP. For instance, a standard GE 9,000 btuh heat pump unit for house or Motel room, window and PTAC, runs at a COP of 2.9 and 3.7 respectively. The problem for RVers lies in where do you mount a 110 VAC window unit (finding a window that can fit one). And with the PTAC, most – if not all – are 220 VAC and you need a much bigger hole (16×42)to install.

If anyone out there can get this COP (btuh output vs. Watts input) data for the RV heat pump units please post it here.

Answer: Your question about a COP for an RV A/C-Heat pump is a first for us. We’ve done some searching online and, like you, have not gotten any hits specific to Dometic or Atwood A/C units for RVs.

However, here is what my calculated number is for pur specific Dometic A/C unit with heat pump.

Our AC/heat pump units are built in roof-top and we have been happy with their performance. We have a Duo-Therm Penguin model # 63515.321 (manufactured in 2002).

BTU/hr 13,500
Compressor rated load amps are 12.4 at 115 volts
Fan motor rated load amps are 3.1 Watts = 1782.5

We’ve looked at the formulas for calculating COP and they seem to be dependent on temperature, so it is a moving target. Perhaps this is why you have not been able to get a direct answer from Dometic or Atwood.

If you have a simple way of converting my numbers to COP then you may have a start.

Maybe others can provide further information.

Comments for Heat Pump

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Dec 13, 2012

Portable AC with Heat Pump May be Best Option

by: shannon

The Portable AC with heat pump units with a vent hose through a window or appropriate sized hole are likely the most efficient as well as most cost effective way to own a heat pump for a RVer.

I have done some research on these over the last few years and with the “published” available data these units are just as efficient (COP of 2.2-2.5) or maybe even more efficient than the units that Dometic, Coleman and Atwood sell at nearly double the price.

For around 500 dollars you can buy a LG or New Air, which seem to be the better ones. I have seen some complaints on the Soleus models.

However, I still cannot get any data for COP from Atwood or Dometic for their roof mounted AC w/heat pump. They are continuing to stone wall my inquiries

Perhaps the efficiency and price of these portable units is why they don’t want to “publish” their COP data?

So, join me and start asking that Dometic, Atwood amd Coleman “publish” their COP for their heat pump units.

Nov 26, 2012

COP rating

by: Shannon

When calculating Coefficient of Performance (COP) most all Heat Pump manufacturers stick to an industry standard of 47 degrees F.

Also, for most heat pump/AC units the BTUH advertised rated output is usually just in cooling mode. When the unit is operating in reverse cycle heating mode (without any sort of electric resistance heat strip) the rated BTUH output is usually less than the cooling output.

So, the BTUH rating for a unit is usually for cooling only.

I have been told that the Dometic HP (High Performance) Heat Pump is the best or most efficient but again Dometic won’t reveal COP at 47 degrees F.

A local large RV dealer/maintenance shop tried to get this data for me from Dometic but relayed to me a few days later that this data was not “published” data.
I think it is kind of strange that a RV maintenance tech would use such a word as “published” data in his response to me.
It sounds like a lawyer’s response.

I just want to know which unit compares to a GE window unit and which RV roof top unit is the best so I can make a definitive decision to a purchase the most efficient heat pump.

By the way, I haven’t asked Coleman yet. One RV website (PPL Motorhomes I believe) when describing a Coleman Heat Pump they sell stated “2.5 times more efficient than electric resistence heat” . I am not sure how they calculated this or if this data was taken from “published” Coleman data?

Thanks and perhaps someday we’ll get Dometic, Atwood and Coleman to “publish” the COP data for their heat pumps.

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