Why does my Cool Cat heat pump not turn on when it's below 45? - Fiberglass RV
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Old 12-10-2020, 01:18 PM   #1
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Name: Michael
Trailer: Casita
Texas
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Why does my Cool Cat heat pump not turn on when it's below 45?

https://www.dutchmen.com/resources/m...ons-manual.pdf

Finally got to test my camper in cold weather and learned that the heat pump doesn't turn on until it's 45 or above outside. I see it clearly in the manual now too!

Anyone know the science behind why that limitation exists?
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Old 12-11-2020, 01:18 PM   #2
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Your heat pump is collecting heat from outside and transferring that heat to the inside of your trailer. As the outside temperature drops, the availability of heat outside becomes scarce. The outside coils become very cold; cold enough that the condensation on the outside coils will freeze, reducing (or completely blocking) the flow of air over the coils. Most home and commercial heat pumps will briefly reverse themselves by switching to the A/C mode which pulls heat from the inside of the house to the outside coils to melt the frost and ice on the outside coils. Although heat pumps are very efficient in general, their heating ability below 40 degrees is reduced to the point that resistance heating using electric heating elements is necessary. Most compressors on heat pumps have a lifespan of ten to fifteen years. Gas furnace's lifetimes are measured in decades.
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Old 12-11-2020, 01:59 PM   #3
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thanks
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Old 12-11-2020, 08:05 PM   #4
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can't speak for you heat pump, but it makes a difference in the design. My unit is good down to 17*F and I can live with that.
Too cold outside the wall is cold enough that you might want some more heat... in the house.
It has to do with the compression of the gas and the way it is designed as to the temp possible.
One limitation is that freezing of the outside coil as it will freeze up as the moisture condenses on the surface.
I think that my unit will basically dead head the compressor to heat the coil as necessary, but I could be wrong.
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Old 12-11-2020, 09:40 PM   #5
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Originally Posted by redbarron55 View Post
can't speak for you heat pump, but it makes a difference in the design. My unit is good down to 17*F and I can live with that.
Same here. My Fujitsu 9RL2 mini-split will heat (with reduced capacity) down to 15F. Some can go even lower and even at full capacity but they are 208/230V models. It is all about how it is designed. It will use more electrical energy and need to defrost more often. The Cool Cat is designed for primarily cooling and to take the edge off in cooler shoulder season heating weather. I do see that newer models heat down to 30F so that is an improvement over the 45F on older models.
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Old 12-12-2020, 06:10 AM   #6
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There is a reason that cooling units typically use a gas like Freon to move heat from a hot location to cool down an area (swamp coolers use evaporation of water), and heating units typically rely on burning of fuel (wood, coal, oil, propane/NG). Heat pumps are great for cooling, not so good for heating. They will work with diminishing efficiency as temperatures get lower, making them less than ideal for heating in lower temperatures. And they “burn” electricity and put operational hours on a compressor better “saved” for cooling purposes. The fact that they use electricity is an important consideration. If you are using a heat pump, then access to electricity is available. If electricity isn’t available, then likely a propane furnace or heater will be used. But given the availability of shore or generator power, a 1,000 watt ceramic heater (very small box) will keep a small fiberglass trailer comfortably warm in temperatures down to the low 20s F. At 30į F my dual wattage (900w/1,500w) keeps my Escape 5.0 in the 70s all night long on the low (900w) setting, though it has to run almost constantly to do so. Ceramic heaters typically cost $25-$35 and can be purchased at Walmart or any hardware store. Unless they fail, they will operate at any temperature and they eliminate the stress and hours put on a heat pump when it is “asked” to heat rather than cool, which it is far more efficient at doing. More importantly, $25 to $35 is far less than the cost of replacing a compressor system.
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Old 12-12-2020, 08:38 AM   #7
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I have to agree that a small electric heater will keep a small trailer warm, but the analogy on electric use is not particularly correct as the heat pump will still be more efficient until it gets pretty cold oud, again depending on the outside temp.
My system still draws less than 900 watts in heat pump mode where a 1500 watt ceramic heater draws, well 1500 watts. Of course the question is how long do they run at what power setting.
The small heater, placed down low may be better for heating and I usually carry one - just in case...
The arrangement of my setup is with the air handler up high at the rear so the heat starts at the top and kinda stays there. A small fan helps move it around, but then it creates a draft the makes it seem cooler.
The fan is really there because my wife likes the fan moving air to keep her cooler and then I don't have to freeze to keep her happy (mostly cooling mode).
As above the heat pump is mainly for the shoulder seasons and not the freeze you A&& off cold.
I have thought about rigging a heat system utilizing the tankless water heater and a radiator or maybe even better heating tubes under the floor!.
(Amazing what a retired engineer will think of to keep buys)
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Old 12-12-2020, 08:49 AM   #8
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This has been informative, since my other RV has a Cool Cat unit along with a propane furnace. I tried the heat pump but quickly shut it down because I couldn’t stand the racket. The furnace is much quieter (which is saying a lot, since it’s the same Suburban unit as my Scamp).

A lot has to do with the location. The Cool Cat is mounted on the fiberglass roof right above my head, while the Suburban is mounted near the floor inside a wood cabinet at the other end of the camper.

When the Cool Cat goes, I will probably replace it with a regular window A/C unit. Like CPW, if I have power, a small ceramic heater does the job quietly and effectively.
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Old 12-12-2020, 07:06 PM   #9
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Quote:
Originally Posted by redbarron55 View Post
My system still draws less than 900 watts in heat pump mode where a 1500 watt ceramic heater draws, well 1500 watts.

<>

I have thought about rigging a heat system utilizing the tankless water heater and a radiator or maybe even better heating tubes under the floor!.
(Amazing what a retired engineer will think of to keep buys)
Once I've paid for a site with shore power, I am much less frugal with my energy consumption. 1.5KW? This "big spender" says crank up the ceramic heater and enjoy!

We also rely much more on propane than the FrankenScamp, so the hot water heating system sounds intriguing. I'd love to heat the floor below the dinette table. But, I'd best polish up the final details on our home remodel before I indulge too much in Re-Imagineering our trailer.
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Old 12-13-2020, 09:40 AM   #10
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I will admit my confusion but why would someone buy and install a piece of equipment to heat their trailer when that device can only supply heat when the outside ambient temperature is above the level where heat is required
It’s like an air conditioner that could only cool your trailer when temps are below 70 deg F
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Old 12-13-2020, 10:26 AM   #11
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Originally Posted by rubicon327 View Post
Same here. My Fujitsu 9RL2 mini-split will heat (with reduced capacity) down to 15F. Some can go even lower and even at full capacity but they are 208/230V models. It is all about how it is designed. It will use more electrical energy and need to defrost more often. The Cool Cat is designed for primarily cooling and to take the edge off in cooler shoulder season heating weather. I do see that newer models heat down to 30F so that is an improvement over the 45F on older models.
While it is too new to verify, the specifications on my recently installed Mitsubishi MITS MUZ-GI-24NA & MSZ-GL-24NA 240V 24,000BTU Mini Split does not have electric coils & will produce heat down to -4įF.

Here is hoping I don't get a chance to find out if it can actually heat at that low outside temperatures. Very quiet, and, at least down to 24įF (the lowest we have had since installed) it heats my 1000 sq ft ranch house. The installer says it will be less expensive to run than my natural gas boiler; we will see...

I purchased it primarily for cooling. I've managed to go 50 years here in the lee of Lake Ontario without AC, but after 8 90įF+ days last summer I gave up.
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Old 12-13-2020, 11:30 AM   #12
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Originally Posted by steve dunham View Post
I will admit my confusion but why would someone buy and install a piece of equipment to heat their trailer when that device can only supply heat when the outside ambient temperature is above the level where heat is required
Itís like an air conditioner that could only cool your trailer when temps are below 70 deg F
Mine works great at any temp I have been in, down below freezing.
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Old 12-13-2020, 01:08 PM   #13
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Originally Posted by redbarron55 View Post
Mine works great at any temp I have been in, down below freezing.
Most of the heat pumps I’ve worked on here in the midwest have been ground water heat pumps . Standard heat pumps work well in temps above 40 deg F and at 25 to 30 deg F usually require supplemental electric resistance heating
I can see where they may work well in Florida but not in colder climates
In the midwest they are not a viable alternative for Fall or Winter camping
When camping in the Fall as long as nighttime temperatures don’t drop below 40 deg F we don’t require heat just an extra blanket .
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Old 12-13-2020, 06:19 PM   #14
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Don't install a heat pump even if it makes sense for 99% of the cool weather camping you might do.
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Old 12-13-2020, 06:39 PM   #15
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Originally Posted by redbarron55 View Post
Don't install a heat pump even if it makes sense for 99% of the cool weather camping you might do.
A heat pump will not work for 99% of my cool / cold weather camping
The furnace in our trailer works across the full spectrum of weather we encounter when camping
We are going down to weather in the single digits tonight , which matches my definition of cool .
If it works for you in Florida thatís great but itís not a panacea for everyone
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Old 12-13-2020, 10:00 PM   #16
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I will admit my confusion but why would someone buy and install a piece of equipment to heat their trailer when that device can only supply heat when the outside ambient temperature is above the level where heat is required
Itís like an air conditioner that could only cool your trailer when temps are below 70 deg F
Steve: Installed primarily for quiet cooling. Heating capability is just a bonus. We primarily use the propane furnace or an electric resistance heater when really cold.
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Old 12-13-2020, 10:31 PM   #17
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Steve: Installed primarily for quiet cooling. Heating capability is just a bonus. We primarily use the propane furnace or an electric resistance heater when really cold.
I agree , a heat pump works well for cooling but as a four season heating option in many parts of the US , and Canada it comes up short
I understand that Wisconsin is not typical for much of the US but neither is Florida .
Weíve camped in temps ranging from -10 to -20 below F , and if you want to stay warm a heat pump just ainít going to cut it .
My point was to make people aware of a heat pumpís limitation. One size does not fit all !
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Old 12-14-2020, 07:22 AM   #18
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When it gets down in the teens the 1/8" insulation in the Scamp is not going to cut it either and the frozen pipes are a draw back as well. I plumbed mine with PEX so that freezing would not burst them, but camping that cold is not a thing for a Scamp anyway.
The heat pump is an extra that takes care of most all of the camping we will do, but auxiliary heat is a good idea just like with the home units that won't heat efficiently when it is really cold.
The new heat pumps have variable compressors, fans (inside and out) and expansion valves to tune the system for max efficiency and measure outside temp, temp in the air handler and the refrigerant and optimize the parameters as necessary.
They also know the cost of electricity and if there is a time zone for rates and choose the best option for cost.
At one time I had a dual fuel gas / electric heat pump and it almost never chose gas in Birmingham where it does get colder than here in north Florida. That system did not have electric heat strips.
There is a choice to be made, however, and as above I chose the mini-split for comfort, noise and no weight on the roof. Heating and the space saved for a heater is a bonus.
My design in the rebuild eliminated a lot of the space hogging auxiliaries and mounted them on the extended tongue in the form of a tankless water heater and heat pump.
That allowed for more space under the twin bunks for storage and for the hose reels for potable water and the gray/black macerating pump and it's hose reel. Those two items make hooking up and packing up easy, clean and quick. There is also an outside storage locker under there as well. Batteries, electrical etc is down there too.
But if it gets below 30*F with the cold from the floor, sides and windows it is not that comfortable, although the heat pump will be blowing hot air, well at least warm air...
To each his own.
My theory is build what you want, understanding that in engineering and design there are always tradeoffs. To get something you usually have to give up something else.

Best regards,

JD
KE4MD
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