Had a heat pump installed this summer to gain air conditioning in the summer and to take some load off of the fuel oil forced air furnace in the winter (did this when fuel oil was over $3.50/gal, now it's $2.44/gal....figures). The heat pump is to use the fuel oil furnace for it's emergency heat.

Anyways, what kind of temperature swings should I have the programmable thermostat set to for the most economical heating? When we were fuel oil only I had the thermostat set at 68 during the day and 64 at night. With settings like that the new system seems to kick on the emergency heat (oil furnace) a lot, while if I set it to just hold at say 64 degrees it just runs the heat pump to maintain that temperature. I know heat pumps don't put out a ton of hot air all at once so are they just incapable of making a 4 degree swing in temperature or is something not quite right with my system (setting wise or mechanically wise)?

Just trying to get the most out of the system now until the really cold weather sets in (when I know the system will go fuel oil only).... right now outside temps are in the 40's and 50's which are well in the efficiency range of the heat pump.

Ken S.

[This message has been edited by kslish (edited 11-11-2008).]

Hmmm, I am interested to learn more also. I would think the heat pump would just run until it reached the desired temp (like A/C in the summer). Maybe the installer didn't set something right? Wouldn't the oil turn on if there was an emergency (heat pump went out) only?

Funny... our settings are 68F daytime and 58F night.... but any warmer and I don't like it.....

J.

quote Originally posted by jaskispyder: I would think the heat pump would just run until it reached the desired temp (like A/C in the summer).

I thought that as well.....what it is doing now when it tries to go from 64 to 68 is run the heat pump for a while (but not a really really long time say 20 minutes or so although I haven't really timed it), then seems to give up and kicks on the emergency heat.

quote Maybe the installer didn't set something right?

Could be....just wondering if I should place a service call (it's under warranty if it does have a problem). But if there is nothing wrong (other than my expectations) I'll probably get hit with a trip charge fee....probably like $60.

quote Wouldn't the oil turn on if there was an emergency (heat pump went out) only?

Well, the system is designed to cut out the heat pump once it's too cold outside for it to run efficiently (I think around 30 degrees).

i am in fl, we do have some heat pumps here but they all have electric heat for the emer. heat. it sounds like the t-stat is a two stage heat pump t-stat. the second stage of heat is the fuel oil, if the swing is more than say 2 degrees the t-stat will bring the second stage on. if that is the way they wired it. call the contractor you used and ask if that is how it was put in. 40 and 50's the heat pump should be able to heat to 68 by its own but the t-stat is trying to bring the heat up quick so it brings on the fuel oil heat.

quote Originally posted by dudewithoutfiero: i am in fl, we do have some heat pumps here but they all have electric heat for the emer. heat. it sounds like the t-stat is a two stage heat pump t-stat. the second stage of heat is the fuel oil, if the swing is more than say 2 degrees the t-stat will bring the second stage on. if that is the way they wired it. call the contractor you used and ask if that is how it was put in. 40 and 50's the heat pump should be able to heat to 68 by its own but the t-stat is trying to bring the heat up quick so it brings on the fuel oil heat.

Exactly.

There is nothing wrong with your system.

The t-stat doesn't know if you've just bumped the heat up from 64 to 68 or if you've had it set on 68 and it's still only 64° inside. All it knows is the ambient temp is 4° below what it's set at, so it brings on the oil heat. If set on a steady temp, the emergency heat will come on before the temp drops 4° below your setting.

You need to find out what the temp difference between stage 1 (heat pump) and stage 2 (oil) is. That's the most you can move the temp up at one time w/o bringing in the oil heat. You may be able to get a programmable t-stat that will bring the temp up a bit at a time so only the heat pump runs. If you can get a 2° swing before stage 2 kicks in, have it set at 64°, then at a certain time bump up to 66°, and later bump up again to 68°. That will let just the heat pump bring up the temp more slowly.

What kind of thermostat do you have? It may be adjustable, but keep in mind if you give it a wider range between stage 1 and 2, it's going to have to drop that far in the winter before the oil heat comes on. You could end up with the heat pump running 100% of the time, and the oil furnace cycling on and off while the house stays 4° colder than what you have it set on.

[This message has been edited by Formula88 (edited 11-11-2008).]

Yea, and keep in mind the colder it gets, the less efficient the heat pump is, to the extent that around *40 outside, its not doing a dang thing. You should have an external tempature sensor of some kind to sense this. Just keep it in mind with your tinkering, it might be more efficient to run the oil at times when the HP will still run, or if its setup wrong, the HP might still be running when its absolutely pointless, just wasting power.

quote Originally posted by 86GT3.4DOHC: Yea, and keep in mind the colder it gets, the less efficient the heat pump is, to the extent that around *40 outside, its not doing a dang thing.

It's a newer high efficiency R-410a pump that puts out noticeable heat until the outside temps are below freezing. It's efficiency graph provided by the manufacturer shows this as well. It shouldn't need substantial backup heat until it's around 30 outside according to the manufacturer's literature.

quote Originally posted by Formula88: What kind of thermostat do you have?

It's made by ICP (International Comfort Products).

quote Originally posted by dudewithoutfiero: it sounds like the t-stat is a two stage heat pump t-stat. the second stage of heat is the fuel oil, if the swing is more than say 2 degrees the t-stat will bring the second stage on.

This set me in the right direction (I think). After reading over the instruction manual for the thermostat (which was written more for the contractor than a consumer.) I finally came across hidden settings for temperature differential on the thermostat.

It is currently set at:

1st stage: 1 degree
2nd stage: 2 degrees
Em. Heat: 2 degrees

I'm assuming that since it is a two stage heat pump, the first and second stages control that and the Em. Heat is the oil furnace.

What I can't figure out is if these differentials are cumulative or just the difference from the set temp.

For example (for a 70 degree set room temp), is it:

1st stage heat turned on at 69 degrees
2nd stage heat turned on at 68 degrees
Emergency heat turned on at 68 degrees

OR

1st stage heat turned on at 69 degrees
2nd stage heat turned on at 67 degrees
Emergency heat turned on at 65 degrees

If it's the first case then that would explain my problem, it's kicking on the Emergency (oil) heat instead of the 2nd stage of the heat pump. Changing the emergency heat differential to 3 degrees should fix it if that's the case.

The contractor assures me everything he setup everything right, but I'm thinking he sets them up for more of a comfort thing rather than for efficiency and cost savings (running the oil all the time will keep you nice and toasty but it'll also cost a fortune over the entire winter).

Anybody have a dual fuel setup like mine? What's your thermostat differentials set at?

I don't have that set-up and I could be wrong but I highly doubt you have a 2 stage heat pump. Your second 'stage' is the emergency heat which is supposed to come on with a 2 degree diff. Sounds like your thermostat is capable of controlling 2 stages but you don't actually have 2 stages.

The first case scenario is correct:
For example (for a 70 degree set room temp), is it:

1st stage heat turned on at 69 degrees
2nd stage heat turned on at 68 degrees
Emergency heat turned on at 68 degrees

I wouldn't set the emergency set point at one degree less that the heat pump setting. Like 69 for heat pump and 65 for backup. When I lived in NY (electric backup) there was about a 4 degree difference between heat pump vs backup. The heat pump will keep the house temperature around 69 until it gets real cold out and the heat pump can no longer extract heat from the outside airto heat the house. I alway left the circulation fans on to stablize the house temp.

I used to have a heat pump and I would run it down to at least 30* without going to back up heat. How long does the heat pump run before the oil kicks in? I know on a 2 stage gas furnace I had I never installed a 2 stage stat and it had a timer wired in that once it ran so long without catching up it would kick in second stage. What stat are you using? i would recommend a honeywell vision pro 8000. Very nice touch screen and works with duel fuel.

quote Originally posted by Dementia: I used to have a heat pump and I would run it down to at least 30* without going to back up heat. How long does the heat pump run before the oil kicks in? I know on a 2 stage gas furnace I had I never installed a 2 stage stat and it had a timer wired in that once it ran so long without catching up it would kick in second stage. What stat are you using? i would recommend a honeywell vision pro 8000. Very nice touch screen and works with duel fuel.

He said he has an ICP stat and it sounds like it is already 2 stage. I wouldn't bother changing it out unless it can't do what he needs or isn't working right. Especially not for a pro 8000 unless he just has money to waste. Just the stat alone costs about $130 (my cost) and if you don't have any connections to get it at cost its going to be quite a bit more than that. They are very nice thermostats but even when mine breaks I just can't see myself spending that much on a thermostat.