Welcome Maverick, nice to have another HVAC guy around. :) I agree about the plenum temps. I can't count how many calls I did where someone just bought into a house with a HP coming from a gas or electric furnace and complained about the cool air blowing half the time.

Yes it does keep it energized, most all of the stats that I've seen working in HP mode energize the reversing valve continuously once it's in either heat or cooling mode. If the valve is energized in cooling mode, once you turn the stat to cooling you'll hear the valve energize whether it's calling for cooling or not, the same works in heating mode. Although it does use a little more power this way, it reduces wear and tear on the valve instead of activating it everytime there's a call. I believe this is why i've only ever seen two of them fail.

Good to know.

I have a good theorical understanding of HVAC (from reading service manuals, HVAC boards, and a little bit of formal education) but there are many things you can only pick up in the field.

A heat pump works it's best only down to 45 F (@ 7 C) then there just isn't enough heat in the outside air.

I think it really depends on many factors including sizing, heat loss, and outdoor humidity. (defrost cycles kill efficiency!) Plotting heat loss (load calculation required) and system output on a chart to determine the balance point is a good idea prior to making any decisions. There are people (search on www.hvac-talk.com) who have successfully used them well below 45F; I don't like to subcribe to "rules of thumb" since every application is different.

Heat pumps are often being mentioned unfavorably for no reasons. They are not supposed to compete with 2 stage gas furnace with ECM motor. Heat pumps are not meant to be used in tandem with this type of furnaces.

Heat pumps shine when they replace electric resistive heating. Well, baseboard heaters or strips remain in the house, but only as back up or supplemental heat.

A heat pump works it's best only down to 45 F (@ 7 C) then there just isn't enough heat in the outside air.

It was correct statement when heat pumps were based on 10 SEER air conditioners. Today's heat pumps work efficiently up to -10C. Ductless systems lead the way. A ductless heat pump is only $200 more expensive than a similar air conditioner. The best thing is that everything has been taken care of by the manufacturer. Even things like low temperature cut off, different modes of operation, etc.

Unfortunately it is not the case with central air units. That's why sometimes they are $2000 more expensive than similar air conditioners. We installed only a few of them. Every time it was a special situation and every time the customer approached us. No complain so far. Knocking on the wood. :)

Back to ductless units. You can see a small gallery of ductless heat pump (http://www.cozyworld.ca/ductless-air-installation.html) installations. All of them are variable capacity Mr Slim from Mitsubishi units. Efficiency in 16-17 SEER range. Today you can get 23 SEER units without much price premium attached.

gm

Very good points GM10. The Mitsubishi's ductless splits have been doing it for a long time now, especially in Europe and beyond where they are more the norm than the exception. I really like the new LG units. Having said that, in our contry where central heat and air are more the standard you don't see them too much in residential applications. Not really practical as a whole home solution.

(...) A heat pump works it's best only down to 45 F (@ 7 C) then there just isn't enough heat in the outside air. (...)Well Maverick69, it seems my experience validates your statement. It's too bad I didn't know that before buying though... All the sales guys always claim heatpumps are good to -12C and that's why I was wondering if mine was not working properly.

BTW, my heatpump is a 13 SEER/8 HSPF YZB 3½ ton York affinity. And while I was at it, I also replaced the 20 year old furnace and got a "matching" variable speed York "modular air handler" with a 25KW electric element.

BTW, my heatpump is a 13 SEER/8 HSPF YZB 3½ ton York affinity. And while I was at it, I also replaced the 20 year old furnace and got a "matching" variable speed York "modular air handler" with a 25KW electric element.

That's actually a very nice heatpump, however going all electric was NOT a smart move. (heatpump with furnace gives you the lowest operating costs)

Make sure that your thermostat is setup to run the heat strips and pump simultaneously; that way, the heatpump will be able to provide a portion of the heat well below the balance point. (strips will cycle on and off, and you will notice a significant reduction in energy costs)

It sounds like the installer didn't know how to set up the t-stat correctly.

All the sales guys always claim heatpumps are good to -12C and that's why I was wondering if mine was not working properly.

The sales guy was telling the truth, but he left out an absolutely critical peice of information.

The following graph shows the output of a 3.5 ton goodman heatpump - yours should be similar...

http://img.photobucket.com/albums/v215/AMDtcm/capacity.jpg?t=1234843973

As the outdoor temp falls, capacity falls. Even below the temperature at which output matches heat loss, it can still provide a large amount of heat.

For example, at 15F (nearly -10C), the unit can still provide around 26,480 BTUs using 2.87Kw of electricity. (Source: Page 22 of goodman's product specs) Defrost cycles aside, your electric heat strips would have to consume 7.76kw of electricity to provide the same amount of heat! :o:o However, 26k BTUs coming out of a system moving 1400 CFM of air can still feel cool. Get yourself a thermometer and measure the output temperature during cold weather (below 0C/32F) - it should still be 15F-20F above room temperature.

Since your backup is electric, I recommend doing the following...

1. Leave the circuit breaker on at all times. Let the heatpump run continuously until the outdoor temperature is below -10C. (Heat strips should cycle in and out to maintain setpoint) Even if the output feels "cool", it's still warmer than room temperature.

Note: Occasionally during cold weather, the outdoor fan will stop operating and you'll see "steam" coming off the unit. (defrost cycle) If the supply air temperature drops dramatically when this happens, your installer screwed up. (Heat strips should come on to temper the air)

2. Make sure that the heat pump remains on when the thermostat calls for auxiliary heat. If it doesn't, one of the settings in the installer's menu isn't correct. If the heat strips are downstream of the indoor coil, option 47 should be set to "ON." Refer to page 10 on the install manual.

3. When the heatpump is operating (outdoor temp above -10C), do not under any circumstances setback the thermostat when sleeping or away. Any energy saved will be lost the second your heat strips come on for recovery. Set it and forget it.

4. Emergency heat should be an option on the thermostat. Check the installer's setup menu and make sure it's set up correctly for a heatpump with electric backup. (Set to "electric furnace", not gas furnace) If this still presents a problem, contact the installer. During really cold weather, turn it to emergency heat to bypass the heatpump.



5. Set electric heat differential to 1 degree Fahrenheit to avoid discomfort below the balance point.

Heat pumps are often being mentioned unfavorably for no reasons. They are not supposed to compete with 2 stage gas furnace with ECM motor. Heat pumps are not meant to be used in tandem with this type of furnaces.

I think that's because many people don't understand how they're supposed to operate, and what the limitations are.

I don't understand the second statement though; I still think it's a great idea to pair a high end furnaces with heatpumps in duel fuel applications. Aside from the high price tag, that is: I guess this climate is too cold to justify duel fuel from an economic perspective.

I think we've lost our way a bit here. The original poster, who's in Gatineau, wanted to know if a heat pump was worth an extra $2K for him.

I said "no" because the climate in his area wouldn't allow him to realize a reasonable return on invenstment.

I'm not trashing heat pumps - just suggesting that they don't have universal applicability.

That's actually a very nice heatpump, however going all electric was NOT a smart move. (heatpump with furnace gives you the lowest operating costs)
Thanks for all the detailed and thorough information txv. I did not (and still do not) have gas in the house. This 20-year-old house has always been on electric heat (forced air), probably because of the (somewhat) lower cost of electricity in Quebec. Switching to gas would have cost me even more. Although not getting a heatpump would have provided some offset...

(...) Get yourself a thermometer and measure the output temperature during cold weather (below 0C/32F) - it should still be 15F-20F above room temperature. I assume you mean measuring temperature in the conduit near the furnace output. I actually did something similar to that last winter: I stuck a thermometer where the air is coming out of the duck on the floor. The air was not even at 20C. I remember that the temperature in the house actually went down after the heatpump had run for a while. That's when I decided to shut off the heatpump for the winter.

I'm running out of time to address all of your points but I am really starting to believe that, like JohnnyG and Maverick69 (and maybe others I can't remember), heatpumps might be great equipment but just not worth it in this climate (where I live anyway).

I for some reason assumed that you were in Ontario - in quebec gas heat makes no sense. (electricity is cheap)

The air was not even at 20C. I remember that the temperature in the house actually went down after the heatpump had run for a while. That's when I decided to shut off the heatpump for the winter.

If the outdoor temperature was higher than -10 to -12C, something is definitely wrong. I can understand the temp dropping a little bit*, but the performance data of heatpumps tells me that you should still be seeing a significant temperature rise. (and I really doubt that the manufacturers are lying - everything's independently tested for efficiency)

This was taken from York's literature...


http://img.photobucket.com/albums/v215/AMDtcm/outputspecsyork.jpg
*Indoor temp will still drop without the elements on if below the balance point, but don't equate dropping with supplying absolutely no heat.


If I was in your position, I would get the refrigerant charge checked in the spring. If you decide to do that, ask the tech what the procedure is; if he just talks about pressures without mentioning subcooling or superheat, find another contractor. Good luck.

(...)If I was in your position, I would get the refrigerant charge checked in the spring. If you decide to do that, ask the tech what the procedure is; if he just talks about pressures without mentioning subcooling or superheat, find another contractor. Good luck.
Thanks for the diligent follow-up txv. Much appreciated.

gm>They are not supposed to compete with 2 stage gas furnace with ECM motor. Heat pumps are not meant to be used in tandem with this type of furnaces.

txv>I don't understand the second statement though; I still think it's a great idea to pair a high end furnaces with heat pumps in duel fuel applications. Aside from the high price tag, that is: I guess this climate is too cold to justify duel fuel from an economic perspective.
__________________


And also, I don't think it's healthy for a high efficiency furnace furnace to run in short bursts during defrost cycles. Eventually, cost of repairs may eat into the savings from using the heat pump. JMHO

However, 26k BTUs coming out of a system moving 1400 CFM of air can still feel cool. Get yourself a thermometer and measure the output temperature during cold weather (below 0C/32F) - it should still be 15F-20F above room temperature.

3. When the heatpump is operating (outdoor temp above -10C), do not under any circumstances setback the thermostat when sleeping or away. Any energy saved will be lost the second your heat strips come on for recovery. Set it and forget it.

4. Emergency heat should be an option on the thermostat. Check the installer's setup menu and make sure it's set up correctly for a heatpump with electric backup. (Set to "electric furnace", not gas furnace) If this still presents a problem, contact the installer. During really cold weather, turn it to emergency heat to bypass the heatpump.

5. Set electric heat differential to 1 degree Fahrenheit to avoid discomfort below the balance point.

I agree that 26K BTU would be cold at outdoor temps of -10°C. 26K BTU is 7583 watts of heat. Granted, it would heat. But it would be a little on the chilly side.

re: 3) Not even 1 or 2° setbacks? I can understand going from 20° down to 14° while sleeping would result in long auxiliary run times. But how about 1 or 2 degree setbacks?

re 4) Is this because the defrost cycles use more energy than the amount saved by using the heat pump? I remember spending the evening at a friend's house a couple years ago. It was -14°C (record cold for us). The heat pump thermostat was set on the traditional HEAT setting. Not emergency. The auxiliary light was on the entire time I was there. But the temps were comfortable.

re 5) I think 1°F is too close. Most people can't even feel a temp difference unless there is 2°F change. And even that's not that much.

As for the heat pump /w electric vs heat pump /w gas debate.....personally being from the west coast I've never understood why people would spend all the money on a heat pump only to match it up with an expensive rarely used natural gas setup. Why not do heat pump with the cheaper easier electric heat or else do an all natural gas setup? Then again, Alberta and east winters I can understand the need for a HOT duct temp system that the natural gas option would give while still maintaining ultra high efficiency for spring/fall with the heat pump running by itself.

3) Not even 1 or 2° setbacks? I can understand going from 20° down to 14° while sleeping would result in long auxiliary run times. But how about 1 or 2 degree setbacks?

I think it depends on the climate; in southern ontario or quebec, a heatpump won't have a chance in hell of recoverying early in the morning without relying on aux heat.

4) Is this because the defrost cycles use more energy than the amount saved by using the heat pump? I remember spending the evening at a friend's house a couple years ago. It was -14°C (record cold for us). The heat pump thermostat was set on the traditional HEAT setting. Not emergency. The auxiliary light was on the entire time I was there. But the temps were comfortable

I think so, based on performance data. (not practical experience)

If the COP is only 1.5 and output is already low to begin with, practically running the A/C full blast every hour (give or take) and using aux heat to compensate would probably wipe out any savings and increase compressor/reversing valve wear.

re 5) I think 1°F is too close. Most people can't even feel a temp difference unless there is 2°F change. And even that's not that much.

A matter of personal preferance I guess; you also have to take the "draft" factor into consideration.

Apparently some of the new thermostats do staging based on rate of temperature change instead of differential. (Much better IMO)

personally being from the west coast I've never understood why people would spend all the money on a heat pump only to match it up with an expensive rarely used natural gas setup. Why not do heat pump with the cheaper easier electric heat or else do an all natural gas setup?

You pretty much answered your own question.

In cold climates the "backup" heat does the majority of the work probably from December to early march. (or April in the west) Since electricity costs over twice as much as gas in most areas, any savings associated with the HP would go out the window with electric backup. (Which is why heatpumps aren't very popular in most of Canada)

Do note that everything I posted here is based on theory only; what actually happens in the field is a different story. (I should have a disclaimer in my signature for this forum) :p

Last question...the Delta T = 1.1 x btu/hour.

Am I missing something here? If you have a 3 ton (aka 36,000 btu), that would mean the delta T would be 39,600. Only a nuclear powered heat pump could output that much heat.

oops, I meant BTUs = 1.1 x CFM x delta-t (The correction factor is really 1.08 if I remember correctly)

I had a thought on heat pumps:
They only move heat through coolant, correct (there is no internal-external air exchange?)
If this is true, could you not make a "greenhouse" or something around it in the winter? The sun would warm the air, helping your heatpump out.
In the summer, you could then remove this/open vents or something to be able to cool your house.

Crazy idea, I know. Just wondering what would happen... :p

No greenhouse could collect enough solar energy to heat a house. Putting an enclosure around an air source unit would really degrade performance. (Air would cool down quickly and be recirculated - many outdoor units move over 2000 cubic feet per minute)

Does anyone out there have any experience with the Zuba-Central heat pump by Mitsubishi ,,
I am thinking of getting one because i have electric heat and i live in the country near Orillia.
any info would be appreciated..
thanks

I am also thinking about the Zuba-Central. I have a cottage in the Kawartha Lakes with a forced air electric furnace which I keep on low during the winter and turn up when I visit periodically. However it is expensive to run and the sequencers keep blowing - almost one per year and therefore needs to be replaced. The last one went shortly after Christmas and a result, my pipes froze and ruptured, but that's another story.

My other choices are oil (smelly and expensive), propane (expensive) or ground source heat pump (extremely expensive to install). I also looked at a traditional heat pump with electric supplementary heat but concluded the extra cost for the heat pump did not make sense because it only works down to -10C. I have a ductless Samsung heat pump in my house and it supplies decent heat down to about -8C, but not much heat below that. It is much less expensive to operate than the baseboard heaters I have (no ducts unfortunately), and quite nicely supplements the heat from my gas fireplace.

The Zuba-Central and Acadia by Hallowell International offer an interesting alternative if their claims of working down to -30C are true. However, both are expensive to install (~ $15,000 according to 2 quotes I received) and the payback is greater than 10 years if I simply replaced the electric furnace. Newer electric furnaces are available with ECM blowers so there would be some savings over my 20 year old furnace, but it will still be expensive to operate.

Expert opinions as to my options would be much appreciated.