Thank you Ona! that is exactly what is happening. Downstair has been running 100% of the time while upstairs have a longer running time but it also stops for about 5 to 7 minutes and then it kicks on again.

Are you also on a 2 zone thermostat?

OK here is what I have done.  Our weather forecast is pretty  constant here for the next few days...see the attached.

I have created a new graph that shows the average out side temp and run time per day.

Last night I set the tstat back 8° , tonight I will not  set back.  I will alternate like this for a few days and we will see what happens.

You can see the graph here,  it is at the bottom of the page titled "SetBack.gif"

geodean ~ great experiment. I do have a question though; won't giving your home 24 hours of constant temp in between the days that you do the setback give false readings? Giving the house and the ground to almost recouperate in between giving it the 8 degree setback? I'm not questioning your knowledge, rather I'm probably demonstrating my lack of it.

conniepangan ~ I do have 2 zones and the upstairs zone almost never turns on! It's always 1-2 degrees warmer upstairs without it even coming on. So, all the energy is going to the first floor and the second floor is warmed just via heat rising. (although from what I understand the dampers in zones are never fully closed so the second floor is getting something when the first floor is on).

Ona, I never seen upstairs thermostat auxilliary heat on. What is your thermostat setting at the first floor and second floor?. I set downstairs at 67 degrees or 68 sometimes, upstairs at 66 and it's warmer upstairs. Sometimes, when I see that aux. heat on. I bring down one notch and the aux. comes off. Do you adjust yours at times or do you just let it stay in one setting?

connie ~ don't be shocked by my first floor is at 64 and my second floor is set at 60, but the second floor actual temp is 65-66. the only thing upstairs are our spare bedrooms and office so we are rarely up there. We used to keep our tstat at 58 when we had an oil boiler so believe it or not, 64 is a warmer relief! I don't change my tstat because I was told not to, but from what I am hearing it seems like it might be do-able.

Ona-wow! that's great that you can handle that and the rest of your family. My husband is still complaining that it is cold at 67 or 68. I wonder if I jack it up to 70 degrees then that means our bill will spiked too?

We set ours at 65 degrees when we had the oil. We used less than 500 gallon on oil last year but still our bill was close to $2000 which includes the yearly contract for maintenance $180 which is they only visit about 2 a year.

Ona,

This is far from being a scientific, accurate experiment.

My thoughts are thus:
During the day, my set point is 71°
During the night it is 63°

So on set back days, the heat pump does not run at all during the night and then  has to run several hours in the morning to catch up.

On non set back days,  the heat  will run off and on during the night to maintain temp and will not have to catch up in the morning.

The difference in run times will tell us which method is more efficient if any.

It will be interesting.

Well, let's just say that it is an ongoing tug of war between my husband and myself. If it were up to my husband I believe it would be set at 62 and fully up to me it would be set at 67. I'm a west coast girl and my east coast husband told me that "everyone" in the northeast kept their tstats at 58! He and his entire family (4 brothers, 1 sister and parents) all keep theirs around 60 so I believed him. Then I started making my own friends and soon found out the truth... we were living in unrealistic conditions! I put my foot down and now we have geothermal. In the previous 4 years we used ~ 1,000 gallons of fuel oil per year (keeping it cold) so you can do the math as to how much money we put into fuel oil.

geodean ~ this will be interesting and show us really how much of a difference in energy costs the setbacks charge... it may not be that much! Thanks for being the test lab!

The effect of the set back will have a direct relationship with the time it is turned down . I was told once less then eight hours not worth it , and the decreased LRA, also countered by decreased EWT . I dont know if attempting to factor this by measuring KWH is possible , but it would be more accurate then run time

KWH is based on run time

The H in KWH is based on run time , the KW part is power consumed , which is not constant , ie start up more , more start ups = more KWH when compared to KWH of constant running.

Dont care to much any data would be interesting

Geothermalman,

I also like your idea. Do you have a part number for the normally open temperature sensor?

 

Johnson A419GBF-1C 24VAC Single Stage Temperature Control about 70 bucks
Ranco makes a 2 stage control a bit more pricey

Sorry didnt mean to answer when not asked

Thanks Dewayne, looking forward to your results. Should be food for thought. Also jealous of your weather forcast. We're sub zero at night and looking forward to a balmy 20* Sunday.
J

I currently have an outside temp controller for aux.  Could I swap it out for a Ranco 2-stge & have it control 2nd & aux?  Say 2nd @ 30F & aux @ 5F for example?

I don't THINK the slight loss of efficiency arising from stage two operation of a 2 speed geo justifies expensive, complicated measures to minimize it.

Locking out Aux until absolutely needed is worthwhile, but these are both opinions unsupported by hard data.

If your opeinion is right about 'slight' and 'expensive' - then you're of course - right.

I wonder if anybody has data.  Other posts I've seen using math say that 1st stage is 15% more efficient than 2nd.  If that's the case (in my case) a couple of hundred bucks for an outside control to maintain 1st stage only until it ran out of capacity would proably have a 1 to 2 year payback.  Hell, I just bought a geothermal system that might have a 10 year payback.

15% in the fossil fuel world would be a headliner.  So is 15% in the ballpark or no?  Anybody know? 

Tough to quantify - so many different thermostat and control systems give a myriad of alternative scenarios.

Some thoughts:

1) Bin data (hourly average temperatures) coupled with an accurate Manual J building load calculation should predict # of hours of 'legitimate' stage 2 operation (as well as stage 3 hours)

2) From that data you'd need to try to winkle out the 'extra' hours caused by suboptimal zone control board or overactive thermostat(s) Not sure how to go about that other than via placing hour meters on stage 1 and stage 2 signal wires and comparing it using actual weather data (not BIN - every year is different from averages)

Calculating the efficiency difference between stages is not trivial - certainly one would use the manufacturer performance tables as a starting point. Then actual data would have to be gathered at the system in question - ARI efficiency ratings assume a specific drop in EWT when 2nd stage kicks in. EWT will drop (closed loop, not open loop - yet another consideration) but not exactly as ARI assumes.

Another complication is that for most systems no effort is made to increase GPM at 2nd stage. However, manufacturer performance tables use different, higher flows for stage 2 tables.

Finally there is the need to interpolate, probably 2 dimensionally, using the tables - EWT data is only provided every 10 degrees, and flow in even or odd values every 2 GPM. Rounding for simplicity could introduce errors near or greater than the calculated loss of efficiency.

Finally finally, all of this assumes airflow is at rated CFM. ECM blowers supposedly deliver specified CFM to within 5% but ONLY IF duct ESP is within bounds - for many duct systems it isn't. For zoned systems, ESP may be in bounds only if large zones are calling, but not in the case of small zones, a design compromise sometimes tolerated under the theory that single small zone operation is relatively rare and short-lived. If CFMs aren't where they need to be, all bets are off with efficiency calculations. There are correction tables, but knowing the CFM in a high static situation isn't easy.

I'm okay with 15% as a basis for back-of-envelope estimates, but determining the fraction of 2 stage hours that are unnecessary (and therefore available for optimized controls) vs those legitimately needed owing to building load is not trivial.

jambsi,
You already have a recovery problem due to usage. It will not improve by tightening the parameters under which your heat pump can employ second stage.
j