Heat Pumps and Electric Heating - gas usage same as before heat pump installed

Hello,

I live in Olympia, WA and my home is 1-story and 1340 sq ft. It's only two years old and it came with a gas furnace/forced air for heating.

Last Summer I decided to invest in a heat pump so that I could have air conditioning in the summer and use the heat pump as my primary source of heat in the winter (thereby reducing my gas usage and energy costs in the winter). My understanding is that the gas furnace would only be used as a backup heat source during the winter. My heat pump is a Trane 14-Seer 2 ton split system R-410A Heat Pump (XL14i).

I just got my November energy bill and I was shocked to find out that my gas usage was almost identical to what it was a year ago, despite the fact that my primary source of heat is supposedly my heat pump now. My electric usage went up as well (as I expected it would)... but that means my total energy costs are outrageously high compared to a year ago, and I was expecting the opposite to happen by investing in a heat pump!

I had a Puget Sound Energy technician come out and make sure that I had no natural gas leaks, and that checked out okay. While he was here, he could tell that my gas furnace was definitely coming on and being used to heat up my house. (I guess I should have been able to tell this by the sound of the furnace firing up in the garage, but I didn't know what to listen for). However, I know that my heat pump also comes on from time to time as well because it's right outside my bedroom window so I can hear it sometimes.

What's going on?! Is my primary heating source still my gas furnace despite having this new heat pump? Do I need to have the company that installed the heat pump come check it? I looked inside the heat pump to see if there was frost on it but it looked okay to me. What else could cause this?

The temperature around here right now .. average low 33, average high 44. I'm not sure what the averages were for most of November (but not this cold).


thanks,
Monica

Monica

There are several different methods of setting up a heat pump in a dual fuel system. One method is having the appropriate thermostat make the switch back and forth between the two different methods of heating. This occurs when the inside thermostat setpoint can not be maintained by the heat pump, then the thermostat will call for auxilliary heat which in a dual fuel system is your gas furnace. The outside temperature when this occurs is called your balance point.

Another method of controlling your heat pump operation is with an outside thermostat that is connected to your heat pump and sends a signal to your gas furnace. You can set the temperature that you want the heat pump to operate. For instance, this outside thermostat is set at 32 deg fah. Your heat pump will operate above this setting and when the temp drops to 32 or below, your gas furnace becomes your heating source. I prefer this method as you are in control.

I would ask your installing dealer to come out and review the operation of your dual fuel system. Find out what method setup your dual fuel system is using for heating. Your problem/complaint sounds like set-up issues and you definitely need a tech familiar with dual fuel set-ups. Based on your temps, the gas furnace should only operate very infrequently. I personally think you would have been better off getting a matching air handler rather than using a gas furnace because of your moderate winter climate. I would hope your heat pump was sized correctly as a 2 ton for a 1340 sq ft home may be questionable.

My opinion.
Good LucK!

Service technician is coming out on Tuesday to look at it. I hope I know the right questions to ask. I think I have an outside thermostat connected to the heat pump that sends a message to the furnace at a certain temp. What if he says 32 deg fah is too low of a set point for that? What is an appropriate set point?

I think 2 tons is sized appropriately for my house. They did a heat load calc last summer, and I think I was on the border between 2 and 2.5 but we chose to go down instead of up.

okay, I'm freaked out now! The service tech came this morning and he told me my heat pump "is not supposed to run during cold temperatures" and that the set point is supposed to be 40 degrees Fah. He even called someone who is the so-called expert in these matters and I also heard him say 40 degrees! I argued with him about it a little and he just gave me a blank, stunned stare. I asked him to show me how to change the set point anyway, so he did show me how and now I have it set at 30 degrees Fah. He then called someone again and they told him that I will find that the heat pump won't be able to heat my house very well at that temperature. yikes! what am I supposed to think or do?!

So then, I asked if he could change the airflow to some of my vents because my bedroom and bathroom gets way too hot. They've done this for me in another room before so I know they have to go under the house to do this. Well this guy just went over to my vent and closed it halfway using the lever thing. You can't even adjust my bathroom one in that way but he said it "feels normal to me". I told him he has to go under the house to do this and so then he goes and calls his boss again. Now he's under my house and I'm frightened at what he may do under there!

I so regret going with this company.

If it was sized properly it should be able to run to 30º no problem. If it's undersized or improperly charged it will not be able to keep up.

MonicaP

First of all, take a deep breath. I don't believe it is as bad as it might seem. Matt is correct. If HP was sized correctly and charged correctly, you will be OK. If not, then you may have a problem. I would ask your dealer to calculate your balance point. In the meantime, I would set the outside thermostat to 33-34 deg and try this for several days to maybe a week. If your heat pump can maintain your home's thermostat setting, then you should perhaps move the outside thermostat down a few degrees. I thoroughly understand that you want comfort and at the same time to run your gas furnace as little as possible. This may take a bit of experimentation on your part.

But if your HP fails to maintain your home's inside thermostat setting at outside temp of 33-34 degrees, then I definitely would get back in touch with installing dealer. You did not purchase a HP to run at temps at or above 40 deg. That would be ridiculous and any reputable dealer would agree with that.

As far as air flow goes, you may want to check your ductwork system and see if you have adjustable dampers on each supply vent. If so, this is the proper method of adjusting air flow to your rooms.

It is not my intention to be negative but a dual fuel set-up for your climate is overkill.

Good LucK!

I don't mind experimenting with the set point, but when you say set the outside thermostat to 33-34 degrees, I am not sure if you mean I physically need to go outside to do this or if I just use the indoor thermostat and do it like he showed me to do it earlier today. (maybe this goes back to your earlier question about which kind of set-up I have, and I still don't know. The service tech this morning was no help in finding this out.)

Also, what do you mean by the heat pump being properly or improperly charged? How would I know? The cooling system seemed to work well over the Summer if that's any consolation.

So it sounds like I should contact the sales guy who did the initial work-up in my house and ask him to calculate the balance point? I made him do a heat load calc at the time but he did it on his computer and I didn't get a print-out of it. Wish I had that now.

MonicaP

As far as air flow goes, you may want to check your ductwork system and see if you have adjustable dampers on each supply vent. If so, this is the proper method of adjusting air flow to your rooms.

It is not my intention to be negative but a dual fuel set-up for your climate is overkill.

Good LucK!

Do I have to go under the house to check for adjustable dampers? I'm not sure how they did it, but when they did the initial installation, they helped reduce airflow to one of my vents (they did this as a favor at the time because they weren't able to do the installation on the scheduled day and I had to wait over the weekend for them to do it). At the time, he told me to just let him know if they need to be adjusted again.

Monicap

The supply dampers would be in your crawl space at each supply leg coming off your main supply ductwork. These dampers should be visible with a small handle for opening and closing.

As far as your refrigerant charge, this is not something that you can check. However, I think I would ask tech to check the temperature at several supply vents with a digital thermometer. Any good tech would have one. You should be getting a temp in the 90s with normal HP operation.

Your installing dealer should make your balance point calculation for you.

You need to find out the method of set-up your dealer is using to switch from HP operation to gas furnace and back and forth. I suspect you have the restrictive method where a mechanical thermostat is set inside your heat pump control cabinet that sends a signal to your furnace when the outside temperature reaches a pre-set point. Your dealer should have shown you the location of this mechanical thermostat as it is very easy to adjust up and down. Again, I suggest setting it at 33-34 degrees and then go from there.

Good LucK!

Monicap

You need to find out the method of set-up your dealer is using to switch from HP operation to gas furnace and back and forth. I suspect you have the restrictive method where a mechanical thermostat is set inside your heat pump control cabinet that sends a signal to your furnace when the outside temperature reaches a pre-set point. Your dealer should have shown you the location of this mechanical thermostat as it is very easy to adjust up and down. Again, I suggest setting it at 33-34 degrees and then go from there.

Good LucK!

I was able to change the set point from 40 degrees to 30 degrees using my indoor thermostat. I didn't have to use an outdoor mechanical thermostat. I have noticed that it is much harder for the heat pump to keep my house warm now. It does okay though... I can suffer through it. Right now it's below 30 outside anyway though so my gas furnace is doing it's job. I have noticed that when the gas furnace is working it gets hot in my house fast.

I am familiar with this model heat pump and at 30 degrees a properly sized unit has no problem keeping up. However, the air temp is much lower than that of your furnace making the house feel drafty.

Do you set the temp back at night? If you do.. Set it and forget it!

Has the furnace been changed out??

What t-stat is used to control this?

If you feel drafty. you could slow down the blower speed (warmer temp too)

The heat pump should be able to work 30 degrees

Do you set the temp back at night? If you do.. Set it and forget it!

I set it to 68 when I'm home in the evenings and down to 66 when I go to bed and when I'm gone. Are you saying set it to 68 all the time?

Has the furnace been changed out??

Don't understand this question. I still have the same gas furnace that came with the house when I bought it two years ago (brand new).

What t-stat is used to control this?

Honeywell TH8000

If you feel drafty. you could slow down the blower speed (warmer temp too)

The heat pump should be able to work 30 degrees

It works, it's just much slower to heat and seems like it has to work really hard at it.

It's good to make it work.. As long it can keep the temp it's fine.. You don't want it to cycle much.. Like in a car. you get better milage when you go down the highway vs the stop and go.

Do you set the temp back at night? If you do.. Set it and forget it!


I set it to 68 when I'm home in the evenings and down to 66 when I go to bed and when I'm gone. Are you saying set it to 68 all the time?

What t-stat is used to control this?


Honeywell TH8000

Monica, after reading your original post again, I would say your heat pump is undersized. While 2 tons may be enough for cooling, its not quite enough for heating. The sizing for heat pumps varies greatly by manufacturer and location. The contractor may have gone by the book without entering all the variables into the equation. Probably not his fault.

I'm a homeowner who, like you, is new to heat pumps.

There is more to operating a heat pump than a gas furnace but the knowledge required is not rocket science, just more detailed.

Sizing air conditioning and Heating equipment.
The size of the system depends on the geographical location.
For Olympia Wa. the following temperatures apply:
Temperature for which heating system is designed = 22*F
Temperature for which air conditioning system is designed = 83*F

Quite often the size of the heat pump is designed to handle the cooling requirements (oversizing cooling is a no, no) and may be less than the maximum winter heating requirements.

Another thing to keep in mind is the fact that heat pump capacity drops with colder temperatures while heating requirements for the house go up. I have a 2 ton heat pump in my house which puts out 24,000 BTU/hr of heat at 47*F and only 17,000 BTU/hr at 30*F. Your 2 ton heat pump will have similar characteristics.

Defrost Cycle
Another thing to bear in mind is heat pump defrosting. At outside temperatures below 45*F and especially when humidity is very high, frost forms on the coils of the outside unit; this frost has to be melted (if you have ice forming on the coils, you may have problems). Periodically, the heat pump operation is reversed (becomes an air conditioner for a short time) to melt the frost. During the defrost cycle, the furnace switches on for a short time to prevent a cold blasst of air from heat registers (remember, to defrost, the heat pump becomes an air conditioner). You may notice steam rising from the outside unit during defrosting; that's normal.

Balance Point
When the heat pump cannot handle the maximum heating requirements for the house, a calculation (or a guess) is made to determine the temperature below which, heating is switched to the gas furnace. This temperature is known as the balance point. (The original 40*F balance point for your house was, in my opinion, way too high).
If the Balance point is close to the capacity of the heat pump, the heat pump will operate for very long periods of time when near the balance point. This is normal.

Response to Thermostat Settings Changes. Temperature of Air Coming Out of Heat Registers.
A heat pump is designed to maintain a set temperature for long periods of time. It does not like big raises in temperature settings. If you raise your thermostat setting by 2 degrees or more, the furnace will switch on even if the heat pump can supply the additional heat (in a long period of time). Once the new temperature is reached, the heat pump will once again take over from the furnace.
This brings us to thermostat set backs. Newer programmable thermostats are designed to handle set backs gradually. For example if you program your thermostat for a night temperature of 66*F and want to return to 68*F at say 7 a.m., the thermostat will allow the temp. to drop to 66*F and and at approximately 5:30 or 6:00 am it will signal the heat pump to start raising the temperature gradually, to avoid furnace operation, until the temp. reaches 68*F at 7 a.m.

The temperature of air coming out of heat registers is higher when the furnace is running than when a heat pump is running. If you maintain a 68*F temperature in the house, the air coming out of the heat registers very close to the furnace will probably be 90*F to 95*F. With the furnace running it can easily reach over 100*F.

My guesses about your house
My place is a 1760 square ft. 21 year old single storey house sitting on an insulated 4 ft. high crawlspace and has a moderate amount of double glazed windows.. It is located in White Rock B.C. where the heating design temperature is 17*F (lower than yours). It is heated by a 2 ton heat pump with the balance point set 35*F. Below 35*F, heating is provided by a gas furnace.
Since your house is newer, smaller and your winters are not as cold as ours, all other things being equal, your heat pump should easily handle the heating load down to 30*F balance and maybe even lower when you take into account such additional heat sources as lights, hot water tank heat losses, heat generated by human bodies, cooking, washing clothes, etc....

My heating ducts are located in the crawl space which had poor wall insulation. I added insulation to reduce heat losses.
I also have several very long duct runs. Because of heat losses in these runs the temperature at the distant heat registers is low. I' ll be adding duct insulation in the near future.

Hope I didn't supply too much unecessary information.

I'm a homeowner who, like you, is new to heat pumps.

There is more to operating a heat pump than a gas furnace but the knowledge required is not rocket science, just more detailed.

Sizing air conditioning and Heating equipment.
The size of the system depends on the geographical location.
For Olympia Wa. the following temperatures apply:
Temperature for which heating system is designed = 22*F
Temperature for which air conditioning system is designed = 83*F

Quite often the size of the heat pump is designed to handle the cooling requirements (oversizing cooling is a no, no) and may be less than the maximum winter heating requirements.

Another thing to keep in mind is the fact that heat pump capacity drops with colder temperatures while heating requirements for the house go up. I have a 2 ton heat pump in my house which puts out 24,000 BTU/hr of heat at 47*F and only 17,000 BTU/hr at 30*F. Your 2 ton heat pump will have similar characteristics.

Defrost Cycle
Another thing to bear in mind is heat pump defrosting. At outside temperatures below 45*F and especially when humidity is very high, frost forms on the coils of the outside unit; this frost has to be melted (if you have ice forming on the coils, you may have problems). Periodically, the heat pump operation is reversed (becomes an air conditioner for a short time) to melt the frost. During the defrost cycle, the furnace switches on for a short time to prevent a cold blasst of air from heat registers (remember, to defrost, the heat pump becomes an air conditioner). You may notice steam rising from the outside unit during defrosting; that's normal.

Balance Point
When the heat pump cannot handle the maximum heating requirements for the house, a calculation (or a guess) is made to determine the temperature below which, heating is switched to the gas furnace. This temperature is known as the balance point. (The original 40*F balance point for your house was, in my opinion, way too high).
If the Balance point is close to the capacity of the heat pump, the heat pump will operate for very long periods of time when near the balance point. This is normal.

Response to Thermostat Settings Changes. Temperature of Air Coming Out of Heat Registers.
A heat pump is designed to maintain a set temperature for long periods of time. It does not like big raises in temperature settings. If you raise your thermostat setting by 2 degrees or more, the furnace will switch on even if the heat pump can supply the additional heat (in a long period of time). Once the new temperature is reached, the heat pump will once again take over from the furnace.
This brings us to thermostat set backs. Newer programmable thermostats are designed to handle set backs gradually. For example if you program your thermostat for a night temperature of 66*F and want to return to 68*F at say 7 a.m., the thermostat will allow the temp. to drop to 66*F and and at approximately 5:30 or 6:00 am it will signal the heat pump to start raising the temperature gradually, to avoid furnace operation, until the temp. reaches 68*F at 7 a.m.

The temperature of air coming out of heat registers is higher when the furnace is running than when a heat pump is running. If you maintain a 68*F temperature in the house, the air coming out of the heat registers very close to the furnace will probably be 90*F to 95*F. With the furnace running it can easily reach over 100*F.

My guesses about your house
My place is a 1760 square ft. 21 year old single storey house sitting on an insulated 4 ft. high crawlspace and has a moderate amount of double glazed windows.. It is located in White Rock B.C. where the heating design temperature is 17*F (lower than yours). It is heated by a 2 ton heat pump with the balance point set 35*F. Below 35*F, heating is provided by a gas furnace.
Since your house is newer, smaller and your winters are not as cold as ours, all other things being equal, your heat pump should easily handle the heating load down to 30*F balance and maybe even lower when you take into account such additional heat sources as lights, hot water tank heat losses, heat generated by human bodies, cooking, washing clothes, etc....

My heating ducts are located in the crawl space which had poor wall insulation. I added insulation to reduce heat losses.
I also have several very long duct runs. Because of heat losses in these runs the temperature at the distant heat registers is low. I' ll be adding duct insulation in the near future.

Hope I didn't supply too much unecessary information.

Demetrius,

Thank you so much for posting the above information. It's very helpful and confirms some of my own research as well. I feel confident that my heat pump is properly sized and that it was a good decision for me to move the balance point down to 30degFah (although I still don't get why the company doesn't even know that this is ok). Ever sine I changed the balance point I've been very happy with both the performance of my heat pump and the reduction in my gas bill!

Monica

How do you adjust the outside thermostat on the XL14i?
I want to check mine to see what it is, my aux strips come on everytime the hp comes on.
Thanks

There is nothing outside at the unit itself.. Just when it goes into defrost, it turns on the heater..


Depends what control is used, some t-stat has a lock out.(Honeywell Vision Pro w/remote sensor), or a box/control on/next to your air handler that controls the system.