HVAC Heat Pump

[Isaac Zachary]

Originally Posted by JSH

$5,000 to $7,000 sounds about right for a new NG furnace. My parents just replaced theirs and it was about $10,000 installed for a 97% efficient furnace for their 1000 sq ft home

Do they live in a mobile or modular home? One HVAC technician I talked to said that the units for mobile or modular homes are actually more expensive than the ones for traditional homes.

What was the BTU of theirs?

Originally Posted by JSH

You would likely spend a similar amount for a heat pump that would go in the same space.

Yes. Interestingly, I can find forced air heat pumps that are designed to replace a mobile home furnace. They are around $4,500 and up for just the unit itself, and apparently come precharged with refrigerant. I'm not sure how much other stuff I'd need if I were to DIY.

Originally Posted by JSH

How large are the temperature swings in your home. You said you turn off the heat at night - how cold does it get. What is the temp you heat your home to during the day when you are there?

Heat pumps can vary temperature fine but they are slower to heat up a cold room than a gas furnace because for a ducted system a furnace puts out air at 150F to 160F while a heat pump is 105 - 115F

Not that it has to be this way, but what we've done is this:

• 45 °F at night while we sleep. We used to go down to 40 °F but then the pipes would occasionally freeze. Unless it's below 0 °F outside, the house usually never actually gets that cold inside.
• Then up to 65 °F an hour or two before we wake up. If it's well below 0 °F then the house will have reached 45 °F and takes a couple hours to get back up to 65 °F.
• Less importantly, we turn it back down to 45 °F when we're out of the house. Usually, it doesn't drop down below 55 °F or so during the day.
• Occasionally we bump it up to as much as 68 °F if we're just hanging out on a holiday or if someone is sick.

Electric rates are the same regardless of time of day or day of week.

Originally Posted by JSH

We are shifting our temperature a max of 10 F which works fine. If you are heating from 45F in the morning to 65 - 70F and then turning off the heat again when you go to work then on again at night when you are home I doubt a heat pump will work well for you.

But we could go to 55 °F to 65 °F instead of down to 45 °F. As far as comfort is concerned, even 60 °F to 65 °F would be fine. Really, we use 45 °F because it's not uncomfortable and because it seems to save us money.

My heat pump is set on a program:

• Mon - Thur 62F at (9 pm), warm to 67 in the morning (4:30 am), drop to 65F at 6:00am, heat to 72F at 3:00 pm, then 65F at 5 pm.
• Friday we are home so it is 69 from 6 am to 3 pm
• Sat / Sunday it is 69 from 6am to 9 pm (no peak electrical rates on weekends)

Originally Posted by JSH

With a heat pump as a primary heat source you would also need back-up heat for at night when the outside temp drops below the heat pump rating. (assuming you heat at night) A small electric heater would do that.

That would be the question there. Last couple of nights have shown us that at 10 °F/nights and 35 °F/days outside a 1,500W heater isn't quite enough to keep the house warm at night, but it does warm up the house enough by mid morning, before noon. But in a worse case scenario a small electric heater would be more than enough to heat our room. The main thing would be keeping the pipes from freezing and figuring out how to eat breakfast in the cold.

Originally Posted by JSH

DIY you would likely need to go with a 36,000 BTU ductless in your kitchen / living room and then a smaller 24,000 BTU unit on the other end of the house in the master bedroom. That would likely cost as much as a furnace or singled ducted heat pump

A 4 ton 48,000 BTU forced air unit starts at around $4,500. I guess that would suffice. With dual systems I'm afraid the bathroom would be hard to keep heated without putting vents in the wall. Ducted heating also, inefficiently, spills heat to under the trailer which helps keep pipes from freezing.

Originally Posted by JSH

Realistically just replacing the furnace is likely your best bet in your climate.

Yeah. I'm afraid you're right.

[redpoint5]

Might be able to set a staggered heating schedule to gradually raise the temperature from 45 F without kicking on the backup heat. You could experiment on what temperature differentials cause the inefficient backup heater to kick on, and then set a schedule that incrementally heats to the desired temp.

[Isaac Zachary]

Originally Posted by redpoint5

Might be able to set a staggered heating schedule to gradually raise the temperature from 45 F without kicking on the backup heat. You could experiment on what temperature differentials cause the inefficient backup heater to kick on, and then set a schedule that incrementally heats to the desired temp.

The heat pumps I've been looking at don't have a backup resistance heater. I think they just won't work at temperatures below -15 °F and at certain temperatures may output less heat and do so closer to resistance heat efficiency. The backup heat would have to be me deciding to turn something else on.

One other type of backup heat I haven't mentioned is the possibility of wood heat. Advantages: it doesn't care if there's electricity or gas or what temperature it is or isn't. (And I'd get to play with fire ) Disadvantages: I would need to cut wood and clean the chimney. It would also increase the potential for a fire hazard.

[JSH]

I believe my parents furnace was 80 - 90,000 BTU. Variable speed blower - 97% efficiency - etc. About as expensive as you can get but the federal tax credit and utility rebate paid the difference between the high efficiency option and the 92% efficiency unit the HVAC guy wanted to sell them. They have a site built home with a basement. Furnace and duct work is in the basement so heat lost from the ducting is not actually lost.

Yes, mobile home units can be more expensive - just like everything mobile home or RV specific.

From your description I thought you had a ducted unit but it sounds like you don't. Sounds like the one that was in my grandmother's mobile home or the one in my parent's lake house. (Just a vertical unit that sucks air in from the bottom and blows hot air out the top located in the hallway near the middle of the home (or vice versa - there are updraft and downdraft versions) (See Below)

When I was giving prices I was talking installed for the forced air heat pump. So that $4,500 for the unit + installation + having an electrician run the 220 line to power it. DIY units generally prefilled and have prevacuumed lines with fixed hose lengths. With a forced air unit generally the lines are too long and even if the unit is prefilled you need to add more refrigerant to accommodate the extra volume from the long lines.

If it takes hours to raise your house temp to 65F in the morning with a forced air furnace a heat pump will not work for you. Not unless you keep your house much warmer at night - which will cost money.

[Isaac Zachary]

Originally Posted by JSH

I believe my parents furnace was 80 - 90,000 BTU. Variable speed blower - 97% efficiency - etc. About as expensive as you can get but the federal tax credit and utility rebate paid the difference between the high efficiency option and the 92% efficiency unit the HVAC guy wanted to sell them. They have a site built home with a basement. Furnace and duct work is in the basement so heat lost from the ducting is not actually lost.

Yes, mobile home units can be more expensive - just like everything mobile home or RV specific.

Got it! So a 40-50,000 BTU at 95% would hopefully be less than $10,000, even though it is for a mobile home. I was told it shouldn't be above $7,000 for me by that HVAC tech who works in Colorado. He didn't say if that's with some sort of credit or utility rebate or not. Just to expect $5,000 to $7,000, and not more than $7,000.

Originally Posted by JSH

From your description I thought you had a ducted unit but it sounds like you don't. Sounds like the one that was in my grandmother's mobile home or the one in my parent's lake house. (Just a vertical unit that sucks air in from the bottom and blows hot air out the top located in the hallway near the middle of the home (or vice versa - there are updraft and downdraft versions) (See Below)

When I was giving prices I was talking installed for the forced air heat pump.

What did I say that sounded like it wasn't ducted? It is ducted, with 6 floor vents (actually 5 now since we covered one to put the frige over it) that blow heat out. They are about 8.5 x 4" in size. The duct goes along under the trailer with the furnace in the middle.

Originally Posted by JSH

So that $4,500 for the unit + installation + having an electrician run the 220 line to power it.

If I had one installed I'd probably just go with whatever the installer offers. I have no idea what the unit price would be through an installer, just that it's no more than $7,000 for a gas unit installed.

If I go with a heat pump I think I'd go the DIY route: I'd put in my own 240V line and install it myself. I can just take the one that I installed for the 40A EVSE that was at the front door. It's plenty long, all I'd have to do is cut it as it goes right by the furnace under the floor.

Originally Posted by JSH

DIY units generally prefilled and have prevacuumed lines with fixed hose lengths. With a forced air unit generally the lines are too long and even if the unit is prefilled you need to add more refrigerant to accommodate the extra volume from the long lines.

Interesting. That makes for a lot of unknowns. Like, where is the exterior unit going to go? What does the extra refrigerant cost?

Originally Posted by JSH

If it takes hours to raise your house temp to 65F in the morning with a forced air furnace a heat pump will not work for you. Not unless you keep your house much warmer at night - which will cost money.

Yeah. It's sounding more and more like I should just ask an installer what is best and go with that option.

This is my exact unit I currently have (Coleman 7663):

[Piotrsko]

All the heat pumps I inspected, set up for self installation come over pressured with the appropriate (natural gas derivative in mine) refrigerant for +/- 20ft additional in {some are 30} and out lines so if youre careful and buy the expensive recommended puncture connections, you don't need additional refrigerant. I was 15 ft, and the installers did not add refrigerant that I saw during the install. Ducting was a different story.

Efficiency went up a bunch wrapping all the 75 year old ducting with foil backed wall insulation after final inspection

It's 24f outside this morning. system ran for 45 minutes to get house to 72 indicated on the thermostat (69 in the furthest room next to unheated garage) from 65 degree holdover

Every system I looked at had provisions for 3-5 kw supplementary electrical heat coils in the under house unit but required a second 25 amp circuit in the panel to run them. If I ever get to -14f I have a pellet stove backup

Was a buyer for 20 years or so. I kinda know how to buy stuff

[Isaac Zachary]

Originally Posted by Piotrsko

It's 24f outside this morning. system ran for 45 minutes to get house to 72 indicated on the thermostat (69 in the furthest room next to unheated garage) from 65 degree holdover

That's a long time. What about -20 °F and heating up from 50 °F?

Originally Posted by Piotrsko

Was a buyer for 20 years or so. I kinda know how to buy stuff

I apparently don't. I can't find an ultra-low-nox unit that will replace my current mobile home furnace. I just don't know how to find one on my own.

[Ecky]

I'm not sure if it still applies, but a few years back it was more cost effective and efficient to have multiple smaller mini split systems than a central heat pump. The ones I installed in Vermont would operate to nearly -30, and I had a pellet stove (a pain in the ass) for the nights when it got colder than -15 or so. The heat pumps did 95% of heating through winter and cut my bills in half. They would even function on most of the coldest nights but approached the efficiency of an electric resistive heater, so I kept a very basic system to heat the house on those nights.

Edit: however I later moved somewhere a good sized chunk of households have neither heat nor cooling. The ultimate bill reduction. No furnace to feed or fix.

[Piotrsko]

Originally Posted by Isaac Zachary

That's a long time. What about -20 °F and heating up from 50 °F?


I apparently don't. I can't find an ultra-low-nox unit that will replace my current mobile home furnace. I just don't know how to find one on my own.

Start with proper search strings: Mitsubishi heat pumps for mobile Home installation. Biggest well known company. GE, also although suspect it's Mitsubishi. rebadged bunch of Korean and vietnamese available for less$$$

-20 &50 room temps just take more time to exchange enrrgy to get to 70. My mild climate rated is still producing, just at way lower BTU on the floor registers, and takes longer to get to 70. @ -20 typical I would have installed the extra heat strips, but it don't normally get that cold here and worst case I fire up the pellet stove. Being all electric it's kinda zero NOX.

Winter electric bill is a whopping $120 @ monthly all electric house, rather un insulated and we have market time pricing

[Isaac Zachary]

Originally Posted by Piotrsko

Start with proper search strings: Mitsubishi heat pumps for mobile Home installation. Biggest well known company. GE, also although suspect it's Mitsubishi. rebadged bunch of Korean and vietnamese available for less$$$

-20 &50 room temps just take more time to exchange enrrgy to get to 70. My mild climate rated is still producing, just at way lower BTU on the floor registers, and takes longer to get to 70. @ -20 typical I would have installed the extra heat strips, but it don't normally get that cold here and worst case I fire up the pellet stove. Being all electric it's kinda zero NOX.

Winter electric bill is a whopping $120 @ monthly all electric house, rather un insulated and we have market time pricing

Heat pumps are zero NOx. And it's nice to see one that will work at -20 °F.

But this is "the coldest town in Colorado." I've seen -40 °F quite a few times. Last year it reached -30 °F several days, one day being -36 °F still at 8:00 a.m. If I went the heat pump route I'd first make sure I had a backup heat source. There's no sense in putting in a heat pump unless it's rated for -40 °F.

But let me do some math here.

Last February was the month I used the most natural gas: just over 133 CCF and the bill was $136 total, including overhead, which I think is something like $30. So about a $100 for a very cold month that I use a lot of gas.

If my math is right, that's just over 3,300 kWh of energy, or about 2,500 of kWh energy if we factor in 80% efficiency. Then take the 11.24¢ per killowatt-hour I pay. That would be $281, nearly triple to use resistance heat over gas. So, for there to be any fuel savings, the electric heat pump would have to average about 300% efficient or better.

One thing to keep in mind with all this electric heat stuff is that the trailer has a 100A panel, or 80A useable for continuous loads. A 50,000 BTU/hr electric heater running at 100% would be 14.7 kW or just over 60 amps. Now we couldn't have that running and the 30A drier at the same time, as that would be more than the usuable amperage for continuous loads.