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Old 10-06-2011, 01:49 PM
 
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We want to help a neighbor get window heat pumps for her trailer. We're thinking of getting two: one for the living room/kitchen (350-370 sq ft), and one for her bedroom (200 sq ft). The ac should be sufficient, but I'm unsure about the heat. I'd appreciate any help with these questions.

1. We live in NC, almost in the mountain region. Winter nights are commonly in the 20s, sometimes in teens, rarely single digits. Days usually get into the 40s, but sometimes stay below freezing for several days. Anyone have experience with window heat pumps in this climate? This would be her main heat source.

2. How do you determine the size of unit needed? I've found some information but I think it's based on the cooling BTU's, not the heating.

3. Who would we get to install it? A carpenter? The ac/heat people in our area don't seem interested.

4. Any experience with certain brands or models (good or bad)?

5. How can you tell from product descriptions whether the unit is a true heat pump, or merely an air conditioner with a heat strip (and what does this mean, anyway?)?

Thanks.
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Old 10-06-2011, 02:05 PM
 
Location: The Triad (NC)
32,467 posts, read 75,660,005 times
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Quote:
Originally Posted by sll3454 View Post
We want to help a neighbor get window heat pumps for her trailer.
1) what became of the furnace and a/c the trailer came with?
1a) replacing what was once there is usually the best approach
1b) and if the answer is truly that the trailer never had any provision for central heat or a/c then the trailer probably has even more woefully inadequate insulation than one that came with such.


That said... keep it simple. Look for a ceiling/roof mounted system that can have the air flow split front and rear:

Coleman HP2 Heat Pump 15000 btu RV Roof Air Conditioner Complete ..

For the supplemental heat you'll need on the coldest nights you're back to electric. Baseboard or even space heaters will do a fine job.
Allowing 1 watt per cubic foot of space... (550x7)= 3850watts is enough to do the heating job without ANY heat pump being used.

hth
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Old 10-06-2011, 02:44 PM
 
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Originally Posted by MrRational View Post
1) what became of the furnace and a/c the trailer came with?
Heat pump, now over 20 years old, pretty much dead. We could replace the heat pump, but she likes the idea of having the separate units for the different rooms so she doesn't have to heat/cool the whole house. Also, the heat pump would probably cost more than the trailer is worth.
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Old 10-06-2011, 03:41 PM
 
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Quote:
Originally Posted by sll3454 View Post
1. We live in NC, almost in the mountain region. Winter nights are commonly in the 20s, sometimes in teens, rarely single digits. Days usually get into the 40s, but sometimes stay below freezing for several days. Anyone have experience with window heat pumps in this climate? This would be her main heat source.
They don't work at those temperatures and use the auxiliary heat. You'd have to determine if the auxiliary heat has enough BTU's to heat that space.
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Old 10-06-2011, 03:58 PM
 
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Originally Posted by thecoalman View Post
They don't work at those temperatures and use the auxiliary heat. You'd have to determine if the auxiliary heat has enough BTU's to heat that space.
Do the window heat pumps not work at the same temperatures as regular heat pumps? Or do they not have the electric backup that other heat pumps have? And how do we determine how many BTU's are needed? (one of our main questions) I asked the guy at a home improvement store and he just told me to get the biggest one (but couldn't give me any guidelines for that determination - or answers to any of my other questions).

We use heat pumps (same neighborhood) and occasionally use our backup (propane). She could get one of those space heaters that use circulating oil as a backup, I suppose.
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Old 10-06-2011, 04:15 PM
 
Location: The Triad (NC)
32,467 posts, read 75,660,005 times
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Quote:
Originally Posted by sll3454 View Post
She could get one of those space heaters...
For the supplemental heat you'll need on the coldest nights you're back to electric.
Fixed in place baseboard or even space heaters will do a fine job.

Allowing 1 watt per cubic foot of space... (550sfx7'ceiling)= 3850watts.
This is enough to do the heating job without ANY heat pump being used.

But you still need to do additional insulation...
or you're just spitting into the wind
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Old 10-06-2011, 06:07 PM
 
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Originally Posted by sll3454 View Post
Do the window heat pumps not work at the same temperatures as regular heat pumps?
An air sourced heat pump only operates until it gets to freezing, some are set to even kick on the axillary heat above that especially if they are using natural gas for the auxiliary. As the temperature drops they become less efficient, the exact cutoff if you were using NG really depends on the rates in your area.




Quote:
Or do they not have the electric backup that other heat pumps have?
I never shopped or reserched the window models, I'd venture to guess they have with and without backup.


Quote:
And how do we determine how many BTU's are needed?
To do it correctly you need to do a heat loss calculation as it's going to vary depending on the building and other factors. Taking a guess and assuming a trailer with a lot of heat loss you're going to be in the 20 to 30K BTU range for 550 sq. ft. at those temps..... that's just a guess though.
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Old 10-06-2011, 06:13 PM
 
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Quote:
Originally Posted by MrRational View Post
Allowing 1 watt per cubic foot of space... (550sfx7'ceiling)= 3850watts.
This is enough to do the heating job without ANY heat pump being used.
That's about 13K BTU , that's not going to keep 550 sf very warm when it's in the teens, especially in a trailer.
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Old 10-06-2011, 10:15 PM
 
Location: Texas
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Considering your weather, I doubt any window unit or even two units are going to do much. All heat pumps are nothing more than an A/C unit running backwards. An A/C unit works by compressing the freon or coolant and in that environment, it absorbs heat, or as we usually say-it cools. When using the heat side, there may not be enough ambient heat outside for the unit to work. That's called the Balance Point of the unit. Most are around 40-42F. Anything lower and it requires a heat strip to help it along. As temps fall, the efficiency drops like a rock and there won't be much heat coming out of it. She needs to be looking for another source of winter heat.
I don't know if these are still made and I don't know the brand but my brother had a kerosene stove that used #1 kerosene that didn't smell and there was no open flame as such. Looked more like a glow in a bulb looking affair. It was either fan forced or radiant. He heated a complete 2000 sq ft house with it and no electricity where he was at. Kinda looked like an old Deerborn stove but it sure worked fabulous. If she has the room for something like that it may be just the ticket for her. The kerosene was available at most Home Centers and Tractor Supply in #1 grade. His had a safety device on it in case it got kicked over and would shut down but it's pretty good size to be kicked over.
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Old 10-07-2011, 04:22 AM
 
41,816 posts, read 47,565,849 times
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Quote:
Originally Posted by TrapperL View Post
Considering your weather, I doubt any window unit or even two units are going to do much.
At those temps no it won't but they certainly make sense if you're going to be using electric for heat because they are more efficient in the higher temps than regular element heaters. Plus you still have the AC in the summer which I'm going to guess is prerequisite in NC in the summer.


Quote:
I don't know if these are still made and I don't know the brand but my brother had a kerosene stove that used #1 kerosene that didn't smell and there was no open flame as such
.

I know something similar, brand name was Monitor. Almost like having a small oil burner. Looking at their web page doesn't look like they make them anymore. The kerosene heaters were huge back in the 80's and their popularity slowly waned through the nineties... I still see them at home stores. With the cost of oil might as well just use electric, it's pretty much a wash. Baseboard electric heaters are cheap and easy to install.
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