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Old 01-21-2018, 06:03 PM
 
39,274 posts, read 40,625,546 times
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Quote:
Originally Posted by whirnot View Post
They are up to 4 times as efficient as resistance heat.
The key words there being "up to". Doing a true cost comparison for these is quite difficult because of so many variables and considerations. Obviously it's superior to resistance electric by itself but when you start comparing to other fuels it's not such a great deal in colder climates especially if the auxiliary is resistance electric and/or you are in area with high electric rates.
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Old 01-23-2018, 01:28 PM
 
Location: Floribama
14,809 posts, read 31,223,570 times
Reputation: 13606
Quote:
Originally Posted by guidoLaMoto View Post
As I understand things:

Heat pumps are lousy heaters compared to a furnace and lousy coolers compared to an air conditioner.
A heat pump is just an air conditioner that has the ability to run in reverse. During the summer, it takes heat from the inside and pumps it outside (thatís why you feel hot air blowing off the unit outside)...and during the winter it takes heat from outside and pumps it to the inside.

When a heat pump is in cooling mode it is no different than a plain old air conditioner.
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Old 01-23-2018, 02:04 PM
 
10,475 posts, read 15,475,867 times
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Quote:
Originally Posted by Tiffer E38 View Post
My first hand user opinion is identical to yours. Our Mitsubishi Mini Split is very efficient (23-24 SEER) and costs about $150 in electricity per year to run and keep our 600 Square Foot addition 70 degrees year round. it's quiet, too. The 3 ton heat pump for the main house costs almost that per month to keep warm or cool and we have the thermostat set to 66 in the winter and 74 in the summer. IF I were to remodel, I'd like to put a Mitsu unit on each floor of the main house and remove the main unit...

Add to this that Mitsu is very quiet and our Trane is loud as cargo train. Previous owners placed it 4 ft away from the large kitchen window, so we get all of it. Plus, when it defrosts itself, I had CLOUD of steam all over that window, until I made a stream redirecting duct over the fan. With only few freezing days lately, and temps mostly around 40, my last bill was $262. That thing chugs electricity like camel water after desert run. With 68/65 set up.
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Old 01-23-2018, 03:51 PM
 
Location: Forests of Maine
30,648 posts, read 49,319,037 times
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Quote:
Originally Posted by southernnaturelover View Post
A heat pump is just an air conditioner that has the ability to run in reverse. During the summer, it takes heat from the inside and pumps it outside (thatís why you feel hot air blowing off the unit outside)...and during the winter it takes heat from outside and pumps it to the inside.

When a heat pump is in cooling mode it is no different than a plain old air conditioner.
Most modern units are variable-speed mini-splits which are fundamental differences.
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Old 01-26-2018, 11:48 PM
 
Location: Was Midvalley Oregon; Now Eastside Seattle area
3,998 posts, read 1,842,438 times
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Found and offer accepted on a new build townhouse with a mini-split and gas hot water radiant floor heat.
We did the inspection the other day. Floor heat would take a longtime to heat the house from a cold start. Floors were still cold after 30 minutes of running. Heat pump immediately warmed the air. Outside temp was near 50 so the HP was really sucking the heat from the outside and dumping it inside.
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Old 01-27-2018, 07:11 AM
 
Location: Forests of Maine
30,648 posts, read 49,319,037 times
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Quote:
Originally Posted by leastprime View Post
Found and offer accepted on a new build townhouse with a mini-split and gas hot water radiant floor heat.
We did the inspection the other day. Floor heat would take a longtime to heat the house from a cold start. Floors were still cold after 30 minutes of running. Heat pump immediately warmed the air. Outside temp was near 50 so the HP was really sucking the heat from the outside and dumping it inside.
So long as the outside temps are so warm to begin with, I have no doubt that it would work very well.

Radiant floor heat is not an instant 'on' design.
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Old 01-27-2018, 11:41 AM
 
Location: Was Midvalley Oregon; Now Eastside Seattle area
3,998 posts, read 1,842,438 times
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Quote:
Originally Posted by Submariner View Post
So long as the outside temps are so warm to begin with, I have no doubt that it would work very well.

Radiant floor heat is not an instant 'on' design.
I had hoped to get toasted feet but apparently its a slow cook ham-hocks.
Now I know why builders put in a mini-split.
In the Puget Sound area, it is rare that temps get to freezing and above 85.
In the Willamette Valley, 200 miles south where I live, less than freezing temps and +90 are fairly common occurrences and a supplemental backup heat is necessary.
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Old 01-27-2018, 12:30 PM
 
Location: Forests of Maine
30,648 posts, read 49,319,037 times
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Some radiant systems are set in a concrete slab, which forms a HUGE thermal mass. Other systems only heat the floor, which is a smaller mass.
Regardless of the size of that mass, a radiant heating system must first heat that mass, before there is any noticeable effect on the house. If the mass is large, it will require that much more heat to get that mass warm.

If a house envelope requires 50kBtu to maintain it warm at -40F outside. That means it would need to steady state 50kBtu heat source running the whole time that it is -40F outside. In such a house, if you walk in and expect the house to be toasty in 10 minutes, you would require a much larger heat source than 50kBtu. Heating the air mass within such a house would be a far smaller task. The floor would remain cold, but the air mass might feel warm in a few minutes.

Heatpumps need to extract heat from a source, to put that heat into some other media. If it is a warm day with outside temps in the 40s, there is heat available in that air, that can be extracted and put into the house. This is an easy task for a heatpump on a warm day.

But on a chilly day of -20F there is far less heat in the outside air. It takes a lot more Btu to heat a house on a -20F, than it would on a 40F day. This is a difficult task for a heatpump to accomplish.

When there is heat in the outside air, is on days when the demand for heat is less. On days when there is very little heat in the outside air, those days have a high demand for heat in the house.
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Old 01-27-2018, 04:06 PM
 
Location: Was Midvalley Oregon; Now Eastside Seattle area
3,998 posts, read 1,842,438 times
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A chilly day in the PNW (west of Cascades) is 40.
Which is why I wonder why not more HP are being installed in Seattle area's new-builds. Cadet heaters are inexpensive but highly inefficient and takes up floor-wall space because of distance restrictions to furniture.
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Old 01-28-2018, 04:20 AM
 
Location: DC
6,510 posts, read 6,434,844 times
Reputation: 3112
Radiant floor heat is a wonderful design. You don't cycle it like a force hot air system due to it's slow response. It maintains a very constant temperature and I find you are comfortable with room temperatures about 2 degrees colder than in a forced air system. If your feet are warm, the rest of you feels warm.
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