They are a supplement to a central heat system? Are they expensive? Do they require a duct system? Do they all work for both cold and hot seasons? If you have one, are you pleased with it?
TIA!
TIA!
The 411 on heat pumps
- Thread starter Mrs. Krabappel
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Bottom line--they can be a highly cost effective way to provide most or all of your heating, esp in mild or maritime climates. Basically looks like an AC and provides AC in summer, can be ducted (like central air) or units mounted in wall (common in commercial applications like restaurants). Basic tech systems are only slightly more than central air units, high eff units can be more expensive....
The technology has advanced in the last 10 years, folks with older units (or bad installs) give bad reports. Those with newer/good installs are generally quite satisfied. There have been many discussions in the green room if you search.
One feature is that their cost/BTU varies with the outside temp, so economic analysis can difficult. This also makes them a good companion for wood heating--let the pump run in the shoulder seasons for low cost heat, burn in the cold weather to offset running costs.
What is your climate zone? What is your average high and low temps in January?
The technology has advanced in the last 10 years, folks with older units (or bad installs) give bad reports. Those with newer/good installs are generally quite satisfied. There have been many discussions in the green room if you search.
One feature is that their cost/BTU varies with the outside temp, so economic analysis can difficult. This also makes them a good companion for wood heating--let the pump run in the shoulder seasons for low cost heat, burn in the cold weather to offset running costs.
What is your climate zone? What is your average high and low temps in January?
Modern mini-split systems can be the primary heater in your climate. They do not require a duct system and are ultra-efficient. Yes, they run in reverse as an AC unit. In Asia, Hawaii and Australia you see lots of these units. The Japanese have really developed this type of heating to great efficiencies. There are several posts in the Green Room on this topic including personal experiences with these systems.
Or, one can install a heatpump that ties into existing ductwork. But that is the less efficient route unless the system gets a good tightening up and insulation.
Or, one can install a heatpump that ties into existing ductwork. But that is the less efficient route unless the system gets a good tightening up and insulation.
I am zone 7a
Climate http://www.weather.com/outlook/health/fitness/wxclimatology/daily/28791?climoMonth=1
Thanks for the info. Will check out the green room.
Climate http://www.weather.com/outlook/health/fitness/wxclimatology/daily/28791?climoMonth=1
Thanks for the info. Will check out the green room.
For about 90% of your weather, a good mini-split would cover your heating. Daikin and Fujitsu make good models. Depending on the unit, you should be well covered down to about 10-15F. After that, it will still try, but I would be burning wood in the big boy then. To find the threads in the Green Room, search on heat pump or search on Daikin or Fujitsu.
If you start looking at units, they will have an HSPF rating, where higher is better, like SEER for AC units.
You can use the HSPF number to estimate operating costs, that is, cost per million BTU, to compare to the price of operating your existing heating system.
It is a measure of BTUs delivered divided by watts of electricty used, averaged over a season, with typical values from 7-12.
So, for a given HSPF, divide by 3.414, to get a measure called SCOP (seasonally averaged coefficient of performance), values are generally 2-3. The SCOP
is easier to understand--it is a measure of how much more efficient a HP is compared to electric baseboard (which turns the elec directly to heat). So, a
nice minisplit system will deliver heat with an SCOP of 3+, and heat your house for less than 1/3 the cost of electric baseboard. A cheapo Goodman HP will have
a SCOP of 2.5, it will cost you 1/2.5=40% as much as electric baseboard.
So, once you've got an HSPF/SCOP number, and your cost per kWh from your elec bill, go to the handy dandy hearth.com calculator
https://www.hearth.com/econtent/index.php/articles/fuel_cost_comparison_calculator/
to compute cost per million BTU for any fuel. For the HP, put in your cost per kWh into the electric, and put the SCOP*100 for a potential HP into the efficiency
box (that is, eff = 200-300%). It will give you a bar chart of operating costs relative to other options.
In your climate, it should come out quite favorable, but still depends on your elec rate. The real HSPF/SCOP figure does depend on climate, and the reported
value is nominally computed for a climate resembling Atlanta. Your climate is close enough I think it will be fine, your HP running costs might be a few % higher
than estimated above. In my climate (Philly), my HP costs me about 25% more than the nominal HSPF would suggest.
You can use the HSPF number to estimate operating costs, that is, cost per million BTU, to compare to the price of operating your existing heating system.
It is a measure of BTUs delivered divided by watts of electricty used, averaged over a season, with typical values from 7-12.
So, for a given HSPF, divide by 3.414, to get a measure called SCOP (seasonally averaged coefficient of performance), values are generally 2-3. The SCOP
is easier to understand--it is a measure of how much more efficient a HP is compared to electric baseboard (which turns the elec directly to heat). So, a
nice minisplit system will deliver heat with an SCOP of 3+, and heat your house for less than 1/3 the cost of electric baseboard. A cheapo Goodman HP will have
a SCOP of 2.5, it will cost you 1/2.5=40% as much as electric baseboard.
So, once you've got an HSPF/SCOP number, and your cost per kWh from your elec bill, go to the handy dandy hearth.com calculator
https://www.hearth.com/econtent/index.php/articles/fuel_cost_comparison_calculator/
to compute cost per million BTU for any fuel. For the HP, put in your cost per kWh into the electric, and put the SCOP*100 for a potential HP into the efficiency
box (that is, eff = 200-300%). It will give you a bar chart of operating costs relative to other options.
In your climate, it should come out quite favorable, but still depends on your elec rate. The real HSPF/SCOP figure does depend on climate, and the reported
value is nominally computed for a climate resembling Atlanta. Your climate is close enough I think it will be fine, your HP running costs might be a few % higher
than estimated above. In my climate (Philly), my HP costs me about 25% more than the nominal HSPF would suggest.
A heat pump is the main reason I burn wood.
They don't work very well below 15 or 20°F and are usually a main heat source with propane, oil or electric back -up.
I consider wood my main heat source and electric/heatpump the secondary source.
As it gets colder out the discharge air gets colder and colder and it runs longer and longer, mine will run 40 or 45 mins just to raise the temp. in the house a degree or two.
It will turn off and then not 10 mins. later turn back on and run another 45 mins. This is on cold days when there is no fire (very rare occurance).
If you add resistance heaters to supplement the heat when it's very cold out your cost skyrockets.
You will have the added benefit of central air in the summer. Mine works out to less than a dollar a day for AC, when set at 74°.
My replacement unit (Trane split system with new variable speed air handler) cost nearly 7$K back in 2007, it is much more efficient than the original 1989 model Trane it replaced.
The new unit was next to the top model in efficiency, and the ductwork was already installed. The most efficient unit was $2500 more for a small jump in HSPF.
A complete with ductwork traditional non split system would be very expensive to install.
We have a couple dozen minisplits in the plant where I work for offices. These cool and heat 120 Sq. ft. areas and are dependable and quiet. Biggest problem is condensate handling. I saw several leak all over the place when the drains stopped working.
They don't work very well below 15 or 20°F and are usually a main heat source with propane, oil or electric back -up.
I consider wood my main heat source and electric/heatpump the secondary source.
As it gets colder out the discharge air gets colder and colder and it runs longer and longer, mine will run 40 or 45 mins just to raise the temp. in the house a degree or two.
It will turn off and then not 10 mins. later turn back on and run another 45 mins. This is on cold days when there is no fire (very rare occurance).
If you add resistance heaters to supplement the heat when it's very cold out your cost skyrockets.
You will have the added benefit of central air in the summer. Mine works out to less than a dollar a day for AC, when set at 74°.
My replacement unit (Trane split system with new variable speed air handler) cost nearly 7$K back in 2007, it is much more efficient than the original 1989 model Trane it replaced.
The new unit was next to the top model in efficiency, and the ductwork was already installed. The most efficient unit was $2500 more for a small jump in HSPF.
A complete with ductwork traditional non split system would be very expensive to install.
We have a couple dozen minisplits in the plant where I work for offices. These cool and heat 120 Sq. ft. areas and are dependable and quiet. Biggest problem is condensate handling. I saw several leak all over the place when the drains stopped working.
- Jan 30, 2009
- 456
FYI - I have been looking at installing a heat pump in place of my central air system. They have air handlers that have electric back up too for when your heat pump is not going to be efficient. I was going to do it solely because it is much more efficient than my electric baseboard heat and i would get great benefit out of it from April to June and September to November. I heat with wood from Oct/Nov to April...and don't use my AC too much at all - duct work is all there.
maple1
Minister of Fire
kettensäge said:
So would you say that they work OK down to 15/20°F? Or should you really turn them off & light a fire when it gets down to say the freezing point?
maple1 said:
I light a fire when it stays below 50° during the day, and turn the thermostat down to 65°. This keeps the heat pump from running 95% of the time.
I wouldn ot say they work OK down to 15 or 20, they are struggling at that point.
I think they are OK down to about 30°, then the efficiency drops off quickly. The discharge air gets colder.
It's not a constant warm feeling heat like oil fired air unless it's in the 40's.
Depends on the make and model. Some have remarkable HSPF ratings. We have one fellow that heated last season with a Daikin split system. Said it was still heating down to zero. I visited a few houses last winter during our LaNina cold spell. 2 Fujitsu systems and one Daikin. It was 14F outside and all were heating fine with just the heat pump. But our system (American Std. Heritage 16) starts getting anemic below about 24F.
Be careful when buying, make sure you have a reputable brand. Maine has 2 builders of cold climate heat pumps, one went from 0 to 800 employees in about a year and screwed the pooch. The other Nyle, makes good stuff and stands behind it. Not sure if Nyle is pushing their products, they stopped selling a Hot water heat pump under their name and started selling under the name Geyser
From the experience we had with our 27 year old unit back when it was new it should be good for you. We just used wood heat for so long it finally died of old age and just sitting there. And a couple of window units keep this place cool in the hottest weather for chump change so I haven't replaced it.
Need to. It is getting old out around here.
Need to. It is getting old out around here.
I have posted about it a lot, but the quick story is:
We had an old AC that died, replaced it and paid a bit more to have it be a heat pump. The existing oil fired burner is the backup for below 20F.
We still heat primarily with wood, but the heat pump is amazingly cheap to run! Well, at least when compared to oil!
I also let the heat pump run on the shoulder season, its cheaper then. The warmer outside, the more heat it can bring inside. If its below about 45F I just use the fireplace as much as I can.
If you are replacing a AC unit, get a heat pump, no brainer. If you are adding one... you would have to think about your specific situation pretty hard to make sure you are spending money wisely.
We had an old AC that died, replaced it and paid a bit more to have it be a heat pump. The existing oil fired burner is the backup for below 20F.
We still heat primarily with wood, but the heat pump is amazingly cheap to run! Well, at least when compared to oil!
I also let the heat pump run on the shoulder season, its cheaper then. The warmer outside, the more heat it can bring inside. If its below about 45F I just use the fireplace as much as I can.
If you are replacing a AC unit, get a heat pump, no brainer. If you are adding one... you would have to think about your specific situation pretty hard to make sure you are spending money wisely.
In your house one or two mini-split heat pumps would be a great idea. I am wrestling with whether to do them or not since I already have the duct work. But the heat and cooling loss from the duct work gives me pause.
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