What is a "heat pump" ?

Brad38 · Mar 10, 2016

BDF said: ↑

I am resurrecting this old thread because I am finding myself buried in choosing both a heating and cooling system- cooling for the entire house and heating for the second floor only.

A bit of background: an old, two story house of about 1,500 sq. ft. Not insulated well or at all in some places though because it has the original 'sheet rock' walls and ceilings, (plaster board, a scratch coat or brown coat of a cement like material, then veneer plaster) it is somewhat insulated.... by mistake. The house had a structural failure of the roof last year and for a bunch of reasons, the entire second floor needs to be replaced. Of course this will be with modern materials and built to code (or better) with insulation. The house currently has a brand new oil- fired, hot water boiler for heat and DHW but no A/C at all- we currently use window units to cool the entire house. So of course now is the time to choose the new method, and this leads me to the subject of this thread- heat pump(s) piggy backed on the A/C units.

One last thing: I am basically forced to build 'upside down' in a way because while the second floor has complete access, the first floor does not. And due to the foundation and lower wall construction, installing anything into the first floor walls is a total nightmare. So the plan is to add virtually everything to the second floor and pipe / wire / connect it to the first floor or cellar as needed with a single chase.

So the choices are, in no particular order:

Central A/C with heating capability: Upside is upfront cost- this is the cheap solution. Downside is a lot of work ducting through the first floor ceiling (which is completely open from above and new floor trusses will provide decent paths for ducting but no first- floor air return).

Central A/C without heating capacity and forced hot water heat in each large room upstairs (first floor is already heated with boiler hot water). Upside is that we use more heat than A/C, and according to my rough calculations, this is the cheaper way to heat the upstairs. Also, each room can be individually controlled by its own thermostat for heating. Downside is cost and the more difficult situation of having to install two completely independent systems.

Mini- splits with heat pump: This one is attractive because it requires no large ducting. Upsides are easier installation, and total climate control in one system. Downsides are many: upfront cost is very high. The units are basically made to be fed with a channel running down the outside of the house and I will not do that (too many channels needed, and they are uber- ugly IMO), so I will have to use a condensate pump on each unit and plumb them into the walls and up to the space above (first floor ceiling or attic ceiling). Plumbing is extremely expensive with two insulated copper lines required for each unit. The heating units will function when it is as cold as it gets here (Mitsubishi has units that function to -13F, and we do not see those lows; this year the lowest overnight was -9F and it was a record setting temperature). Unfortunately, at $0.20 per kilowatt hour, and a low COP at lower temperatures, operating costs will be too high I expect. I have mostly given up on this system mostly due to costs, both initial as well as running (heating) costs.

Mini- splits with hydronic hot water heating: this is the most attractive alternate as I see the situation at the moment. More initial expense to install both the mini- splits and hydronic units, it will be far less expensive to actually use. It has the advantages of a fairly easy installation (including the first floor because the units can be plumbed up and across the first floor ceiling) of the mini- splits, fairly easy installation of heat (probably go with in- wall mounted, fan- forced heat exchangers which are very nice units and reasonable in cost) and the boiler is easy to add zones to for second floor heat. This system, like the mini- splits w/ heat pumps, is also expandable later to add rooms upstairs; we may initially leave the spare bedrooms without A/C and perhaps add it later.

Any useful comments or advise welcome, as are any funny or funny / abusive comments.

Brian
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Hey Brian,

My vote is option 1 if you heat the house with firewood most of the time anyway. (And you're in your "forever" house)

BDF · Mar 10, 2016

Yep Brad, gonna' die in this one- too old to move. In fact, far too old to be doing this kind of reconstruction but it was not my choice....

If you are familiar with it, how much of a nightmare is it to duct an entire ceiling with a new A/C install? And I do not believe I can get a return at the bottom of the first floor so the return intake will be on the second floor, and all the first- floor air will have to run up the staircase. ??

Thanks for the input- I would really prefer to make a decision I do not regret later :-(

Brian

Brad38 said: ↑

Hey Brian,

My vote is option 1 if you heat the house with firewood most of the time anyway. (And you're in your "forever" house)
Click to expand...

wildwest · Mar 10, 2016

BDF said: ↑

Yep Brad, gonna' die in this one- too old to move. In fact, far too old to be doing this kind of reconstruction but it was not my choice....

If you are familiar with it, how much of a nightmare is it to duct an entire ceiling with a new A/C install? And I do not believe I can get a return at the bottom of the first floor so the return intake will be on the second floor, and all the first- floor air will have to run up the staircase. ??

Thanks for the input- I would really prefer to make a decision I do not regret later :-(

Brian
Click to expand...

We have somewhat of a similar situation for different reasons. Pellet stove has been amazing for us.

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What is a "heat pump" ?

Brad38

BDF

wildwest Moderator