do you have to buy a furnace separate than a heat pump

Unknown

if you look in a Water Furnace ground source HP you will find,,,supplementary electric strip heaters. I was a bit surprised to find them actually, but there they were.

s taylor

confused

when getting a heating and cooling system installed, is the furnace included in a "heat pump" or is that considered an "extra"? would you only heat your home with a heat pump?

Bruce Stevens_2

Depends

A heat pump is a an air conditioner that removes heat from the home in cooling mode and removes heat from outside and places it in your home in the heat mode. Whether or not you need a furnace depends on where you live and what heat pump you buy. How cold it gets outside in the winter where you live will determine what you need or if you need a furnace to take over at lower temperatures, there are some newer HPs that will work at lower temps now. That is the short answer I am sure someone will mosey along and expound on my take.

Unknown

Most HPs...

need some form of supplementary heat because they can't do the job well enough down below certain outdoor temps. The cheap / quick fix is to install electric resistance strip heaters in the fan coil unit but is the least efficient way to address the problem. A high efficiency fuel fired furnace or boiler for supplemental heat is probably the better answer without getting too exotic. In the past boilers feeding hydro coils were not the best answer due to the time lag between a cold iron call and the actual production of usable hot water. Todays smaller mod/con boilers provide much faster response times and may be a more viable option than the old 80% cast iron types were. Hope this helps.

John L

furnace

What system do you currently have? A furnace of fan coil are needed to blowe the air thru the home. You may need to upgrade either depending on what type of new system you are putting in. A gas furnacecan be used for supplemental heat.
John L

Rich L.

HP's

"Most HP's need some form of supplementary heat because they can't do the job well enough down below certain outdoor temps."

This is for air source heat pumps and is not applicable if you are considering a ground source heat pump. They operate efficiently regardless of how low the outdoor temp goes.

Also note most heat pumps are sized for the cooling load of the house and therefore come up short on heating requirements in the coldest temps. That's where the back-up heat enters into the picture. If the unit were sized to the heating requirements it would most always be way oversized for cooling and thereby not provide efficient, comfortable AC. It could also cost quite a bit more upfront. There are two stage units out to address this problem. More money up front again.

Rich L.

Actually

MPF you'll find strip heaters on most water to air units. It's not due to outdoor temps, it's all about not over-sizing the A/C.

Sizing for cooling is the standard practice. This leaves you short on heating, therefore the aux heat. Works like a second stage (w2) if the HP can't keep up. Most of the time the unit works off the HP, in the extremes, w2 kicks in also. In the event of a mechanical failure with the HP equipment it serves as a back-up source of heat as well.

Rich L.

Actually

it IS all about outdoor temps! I was thinking btu's of heat in outdoor air as it gets colder vs. outdoor temps/ heat loss of the building.


Air to air units loose efficiency as it gets colder outside because they have to work harder to get heat out of the outside (ambient) air. GSHP's get their heat from the ground which stays at a REATIVELY moderate temp year round.

Generally either type of unit is going to have or require aux. heat on the air side due to sizing of the equipment for the AC load. Sorry for any confusion!

Unknown

Interesting,,,

I was not aware of the "sizing for cooling" issue. I'm just a bit skeptical when I see what is essentially one of the most efficient means of heating tied to the least efficient for supplemental heat. Makes me say, "Hmmm,,,"

Brings me back to the talks I had once with someone about tying "auto start" wood stoves to your heat pump. Below it's COP a spark ignitor could be used to start the stove. The big problem was how to shut it back off when the ODT went back up. A CO2 flooding system for the firebox maybe? LOL...

Seriously though, I'd rather see the forced indoor air style revert to a high efficiency furnace and the hydronic style supplemented by a mod con. Just my $0.02 of course.

Craig R. Bergman_4

Rich...

We size for the heating needs of the home. We try to get a Geo unit that will handle 92%-97% of the heat load at design temp.(-5* for us) Aux heat makes up the 3%-8% needed, and serves as emergency back-up. We use two stage equipment so the cooling doesn't get oversized. I know it's possible to get a home that will be way oversized in cooling but, in eight years, we have yet to have one. The only single stage unit we have is in a home with a west window wall. The heating and cooling loads are almost equal.

Bergy