Fishin

while you don't say where you live, I do not believe in large setbacks for heat pumps. no more than three degrees.

however, read your evolution controller owner's manual. you will be able to lock out the auxilliary heat strip. I would start at 30-32 degrees and adjust as necessary to your climate, home's envelope, and your family's comfort.

better yet, call installing dealer to come back out and show you how to do this. many people lock out auxilliary into the 20s.

don't fret yet. it is doable.

IMO

Thanks tiger. I found it and set it to >32. It was in the Coil Setup Menu. We will see what happens in the am. Btw...Eastern NC.

Worked like a charm. The system started out in low and kicked up to high speed for a little over an hour to get from 65 to 69 set point.

Fishinguy badmouthing me like he is some kind of HVAC expert and can't even figure out how to setup his own system?

That's funny. I was waiting for the bait to be taken. Dude, my tech told me I was not allowed in that part of the menu. Can you imagine.

Put your setback to 66 or 67. Four degrees is a little too much. Don't need to continually re-warm the walls and furniture. System will run less to maintain the temp than it will to re-heat everything. Some folks just set and forget.

I use no more than three degrees and often times, two degrees. Bills went down. I orginally used the factory five degree setback and the HP lockouts. My HP islocked out at 20 degrees (natural gas backup) and setbacks again of no more than three degrees.

My annual electricity useage decreased 10.5% each year on average from the initial base year and my natural gas useage decreased nearly 70% over the same time frame. I have four years of figures to prove it. Setbacks and lockouts work.

Oh boy, the old setback fear. I setback 10 degrees and it is better than 3 degrees. As long as you don't go into aux heat, you will have a hard time convincing anyone with a thermodynamic background that you shouldn't setback as much as possible.

I personally don't have thermodynamic background. My father happens to be a PhD engineer who worked at National Labs in the 70s doing conservation work. He did lots of work on setbacks. I'll take his work over 4 years of figures on a single house.

Think about it - when does a HP work the most efficiently? When it has a long run time - just like when you are heating a house up in the morning. Also, most(all?) are more efficient on high stage.

If your house drops to 60 degrees at night and it is 30 degrees outside, then the delta T is 30. If you only setback to 65, the delta T is 35. Heat loss has everything to do with delta T.

This issue gets me pretty burned up as I think we could literally save 10% of our HVAC energy use if setbacks were used correctly. Correctly is as much as inhabitants can tolerate except if you have a heat pump and it goes into aux heat (and that aux heat happens to be electric).

Well David, glad you trust your dad. I trust the numbers I've generated and the lower bills. Pretty tough to argue with that. And yes, longer run times are more efficient. I set my CPH to 3 and my longest run times are in the morning and the return. Single stage Trane XL14i HP 3.5 ton.

Once at temp, the unit will run only when necessary. And it will run for a minimum of 15 minutes based on the CPH I have set. Depending on outside temp, the HP can run a couple of hours to get to the AWAKE/RETURN temps. I am not oversized and have one of the lowest monthly/yearly bills in my subdivision of custom 2,,400 to 3,000+ sq. feet homes. Built Green Level 3 and well insulated (R-55 in ceiling, and low E2 glass)

I use natural gas for backup heat. My annual gas bill which includes cooking (no hot water) showed me using 56 therms. (Yes, 56 therms. First year was 184.76 therms. KWH first year was 18,598. Just finished year four with 16,658 KWH)

The Pros on HVAC Talk also recommend setbacks of no more than 3 degrees. From experience I know why. Why would I return to a setback of five or more degrees that is touted as energy efficient and pay more money? That makes no sense.

Here's the figures to make it a little more clear.

07-08 (base year April to March)

18,598 KWH...184.76 therms... 5,551 HDD...84 CDD

08-09

16,976 KWH.... 72.98 therms.....5,823 HDD...115 CDD

09-10

16,684 KWH....66.0 therms...5,236 HDD...78 CDD

10-11

16,658 KWH...55.9 therms....5,607 HDD...100 CDD

Speedy - I'm glad your system is working for you. I won't try to convince you but I disagree. Not to toot my father's horn - if you google my last name and "setback", you get an article from 2007 that is still quoting his paper from 1976. A quote from the 2007 article - " The highest energy savings occurred for the lowest setback temperature (16[degrees]C [61[degrees]F]) on the days with the highest heating loads". The basis of the study was confirming the 70s work of my father on a modern tight house built to R-2000 standards (a Canadian thing apparently)

I will take his credentials (Stanford PhD) and his vast research on the subject over again a single house for 4 years. Ever thought that first year was more cloudy? More rainy leading to more defrost cycles. Actually colder and showing the imperfections in the HDD number. Maybe you sealed the house better - I find it hard to imagine that you take such an interest in your energy use and didn't do anything to change it.

As an aside, a HP lockout at 20 degrees only makes sense if you have really cheap electricity given current NG prices. Maybe you do but taking national averages, 20 degrees is too low.

So I challenge you to find a peer reviewed article that actually claims that smaller setbacks are better at reducing energy use.

I don't need to find a reviewed article. House was brand new, Built Green Level 3.

I'll stick with the savings I get. Can't argue with results. I find it interesting that when real world results contradict what the experts say should happen, the real world results are discounted for whatever reasons. Experts can't believe there could be another result.

I don't discount your father's Stanford PHD. However, the steady results of years two three and four which are lower than my base year tell me the "energy saving setbacks" of five degrees or more actually use more energy than those of three or less. The savings amount to around $350 annually, which equates to my highest winter month and my second to the lowest summer month combined.

My electricity rates are 9.9 cents a KWH. Natural gas is now at $1.19 with fees, etc.

Oddly enough, I should have used more electricity in years 2-4 than year one if my HP lockout was at 20 instead of the factory set 40 degrees. Less natural gas was used as expected. However, more electricity for the HP should have been used. Instead it decreased.

My neighbors all use the factory five degree setbacks and a fair number keep their homes cooler during the winter than mine. Their bills are $100 to $150 a month higher than mine during the heating season.

Two neighbors with homes within 100 sq. feet of my size have paid $175 to $250 a month more than I do during the winter months. One keeps his at 70 degrees when he is home and down to 60 when gone. The other keeps it at 67 when home and 60 when gone. The point is they use large setbacks.

My point is that larger setbacks used more eneregy than the smaller setbacks. I'll take that $350 savings over my base (and more as energy rates go up) any year. Over the life of a heat pump of say 15 years, one could buy a brand new outdoor unit.

Larger setbacks with a heat pump simply cost more money than using smaller ones. A controlled environment where test are measured can give you an idea of what to expect. Real world results are always best as life isn't lived in a controlled setting.

I expect to see the same level of great results for years to come. Thanks for your input on this, Dave. I'll believe the results I see with my eyes and pay from my checkbook.

You should read the paper. It was not a controlled environment - it was actual houses. Modeling is great but they always do these tests on real houses.

I realize I won't change your mind. That is actually not my intention. What I don't want is someone else to read this thread and cut their setback's back. If anyone has this question, please do an internet search, there is a large body of research that has been done on real houses.

Speedy - you realize how your results don't make sense as your lockout change from 40 to 20 resulted in lower electricity use. Obviously something else was going on here as that is absurd. Maybe you had some parasitic load in that time period.

I can't really figure out what a "Green Level 3" home is.

I think at those rates, you would be better at 25 or 30 degrees. Each HP is different but I don't think 20 is the right switchover for you. I have a little cheaper NG but same electricity and I change over at 35. I realize that 30 would probably be cheaper but I think you are chasing pennies at that point and the added stress on the HP is not worth it in my case. 40 is obviously too high and that would certainly explain your neighbor's higher NG use. I used 24 therms last month so it isn't like 35 is killing my bill.

I didn't mean to start a big debate. 4 degree setback is working fine. I locked out the auxillary heat to >32 and the systen runs for about an hour to get back from setback. Evening low have averaged 45 degrees +-.

sigh......always needs to be something to try to explain away the obvious. No parasitic loads. No changes in living conditions or people living at home. The cat did not know how to raise the temps as far as we know, though she is a bright little bugger.

If the first year was an oddity, I'd expect to see greater useage at some point down the road. That would be the logical expectation.

Hasn't happened and isn't going to happen in my opinion.

A Level 3 Built Green Home is highly energy efficient and is based on "green" building materials and site work. Adds value to the home. If I would have been a little more knowledgable, I would have specified foam insulation in the walls and floors.

My economic balance point is 17 degrees based on a program one of the HVAC Talk guys gave me three years ago. I entered in all the data on my HP, COP at various temps, energy costs for electricity and gas amongst other things to arrive at that figure and switchover point. The unit struggles a bit to reach temp when its 23 or so but maintains temp just fine when there. When colder weather arrives next year I'm going to use a 2 degree setback. By colder, I mean under 30 degrees. Maintaining temp is more efficient than reaching temp.

The HVAC pros recommend 3 degree setback for heat pumps. Gas furnaces can go five degrees, but I am unsure why.

My setup works well and saves me cash. The factory 5 degree setback cost me. End of my story. Just trying to share what works.

Here is a good link, saying heat pumps should be treated differently than gas or standard electric furnaces.

http://community.seattletimes.nwsource.com/archive/?data=19910203&slug=1264145

OP - nothing wrong with a debate.

Speedy - the link didn't work.
I am going to concede that in your instance, the smaller setback is the right answer. Your relatively high NG rates and what I am guessing is a really good COP at low temps make it so. The fact that your heat pump just barely keeps up at your economic balance point also favor low setbacks.

I am really surprised by your economic balance point although my 20% lower NG rates changes things dramatically. I am curious what your COP is at 20 degrees and how you went about finding it. The efficiency of the NG obviously is an issue and if you have an 80% that again changes things significantly.

It still doesn't change that setbacks reduce heat loss and in the majority of instances, even with a heat pump, a larger setback is the best answer.

Hi FishingGuy,

Your system should have "intelligent heat" elements, where the heat elements are staged on as needed. Also your thermostat has an "intelligent recovery" option, this allows for the stat to determine how long it takes for the temperature to drop to your low set point and thus how long it may take to recover. It can be set to keep the elements off until the last possible minute and then only bring them on to finish the cycle and reach set point, at your prescribed time in the morning.

Check with the installing contractor for these set ups.

To you Health, Comfort & Energy Savings

One of the things I notice is that the system comes on low stage for a very short period of time and then immediatly goes to high stage to get to my set point. The evolution control set point goes up 1 degree at a time until it reaches my desired 69 degree set point. I would seem to me that this morning it should have stayed on the low stage since the outside ambient tempurature was 48 degrees. Is my logic flawed?

I think it is. If your in recovery mode trying to get up to setpoint temperature it makes sense that it runs in the high stage. If its just trying to maintain, thats another story. Then it depends more on the outside temperature.

neo...I would tend to agree with your logic except it is not really in a recovery mode. The Evoulution Controller raises the temp from a set back one degree at a time. My setback is 65 and my desired temp is 69. During the "recovery" mode the controller will show the set point at 66, 67, 68 and then 69. So the system is really only trying to make up one degree at a time. So last night when our low was only 52 degrees my system came on and went to high stage shortly after untill it reached my 69 degree set point. With mild outside temp such as this wouldn't it be more efficent for the system to stay in the low stage if it were able to make up the 1 degree difference?

I actually think it is more efficient to stay in high stage. There is a setting for efficiency vs comfort. Mine came set on comfort and when I switched it to efficiency, it runs at high stage more often. The extra noise was significant enough that I am adding registers.

I don't know exactly what the differences between comfort and efficiency settings except that it definitely runs in high stage more often in efficiency mode.

If you don't like the higher stage, you might try changing that setting - I can't remember where it was but it wasn't really easy to find. You may need to go into the tech settings.

I'll tell you - I saw a significant savings on efficiency mode in the summer. I think July was $200 and August (after I switched) was $160 with similar temps. Winter is so much more variable from month to month and I haven't sat down and compared to last year. But my gas bill was 60% of last year's so I'm not sure there is a meaningful comparison because this winter was so much more mild after setting a few records in Jan. I also found things to seal up.

Dave, I was supplied a custom program from a gentleman on the HVAC Talk site. He is a pro and designed it for his own use. It's pretty detailed and utilized information from Trane's data sheets. I had to pluig in figures for amount of BTU's needed to keep the house at 70 at each of the temp breakdowns (37, 32, 27, 22, etc) and plug in the electric and gas rates.

My COP at 22 degrees is 2.47. My COP at 37 is 2.84, and 2.68 and 2.56 at 32 and 27 respectively. At 42 the COP is 3.07. Single stage Trane XL14i R-22. Natural gas furnace is 90% efficient Trane.

This is what the program shows for costs:

FURNACE......37.........32..........27..........22
All day.....$15.79......$16.58.....$17.37......$18.16

12 hours.....$7.89......$8.29......$5.79.......$6.05

8 hrs run....$5.26......$5.53......$5.79........$6.05

HEAT PUMP.....37..........32.........27.........22
All day...... $12.62.....$14.00.....$5.12.....$5.55

12 hours......$6.31......$7.00......$7.69.....$8.33

8 hours.......$4.21......$4.67......$5.12.....$5.55