3ton 15.5 seer rheem 10.5hspf 1850sqft. Demand defrost vision pro iaq.

3ton 15.5 seer rheem 10.5hspf 1850sqft. Demand defrost vision pro iaq.

3ton 15.5 seer rheem 10.5hspf 1850sqft. Demand defrost vision pro iaq.

I would leave the 10 degree lockout alone...

IMO

Ok sounds like a plan. I guess there is a reason I set it in the first place. This is just the first time for it to be below the lockout for more than an hour or two and the strips are not active. Of course I am also running the pellet stove full tilt which is probably 30-35k btu in the partially insulated basement so if it wasn't on the strips and pump would probably be on solid.

What's the reason for a lockout? Does it damage the pump to be running when it's that cold out? Or is it just blowing cold air into your house b/c it can't extract much heat from the ground? Are you talking about a conventional (air source) heat pump?
I'm not sure what our ground temp is with 275ft deep wells, the air temp has been up and down all over lately - mostly seasonable, a couple days in single digits (and nights below) but then near 30 yesterday, all night, 40 now, dropping again tomorrow. So I don't think the ground froze too deep yet - not like February each year after sustained below-freezing temps.

There are two considerations about best lockout temp. I can not even know if 10 is correct, possibly it should be higher.

There is the wear and tear to running a condenser non stop. I don't like that scenario at all. You will get disagreement from others about that.

And second, there is the operating cost issue. Certainly, you don't want to run a heat pump where it costs more in electricity than the BTUs it produces. Just as well off to run straight emergency strip heat.

IMO

Thanks - I could certainly see this case down south where the heat pumps are sitting outside but was wondering why set a lockout based on outdoor air temp for a GSHP. I did see that Aux Heat was running the other day (and DH hadn't turned on the breaker for the 2nd strip yet, I told him to b/c more cold weather coming, we usually turn it on around Tgiving but he didn't do it then and Dec was a little warmer than usual). For sure I didn't want to load down the pump calling for more heat than the 1st stage Aux could supply!

I will have to check our manual and go through the setup to see what the lockout temp is set at. Thanks

OK, just checked - same VisionPro IAQ t-stat as countryboy, 350 is set to 0 (no lockout) and 360 is also set to 0 (no aux heat lockout, not a big deal since we usually keep 1 of the 2 breakers turned off except dead of winter).

Our outdoor temp sensor always seems to read a bit high - they put it near the dryer vent so I know not to trust it when the dryer is running, but Sat AM lowest I saw (at 4AM when I got up) was -2, neighbor 2 doors down saw -8 on his high/low recording thermometer. DH even stuffed an old wool hat in the dryer vent outside to keep it closed (I will be sure to remove it before I do laundry again), so I hope we're not losing heat through there.

Default setting is 40 - seems high for a GSHP (gee, when outdoor air is 40 the ground is usually nice and toasty). I just set it to 15 since my sensor seems to be about 5-6 degrees high, so maybe the compressor won't run if the actual temp drops below 10. Also set the aux lockout to 50 while I was at it.

So, I can see on display when the Aux Heat is on, is there any way to tell whether the compressor is running or not (besides going to the basement and listening)?

I can't think of why the installer would have changed the default lockout temp to "no lockout" - maybe he thought he was setting it to 0 degrees F?

Thanks

This post was edited by ajsmama on Mon, Jan 6, 14 at 14:38

" mostly seasonable, a couple days in single digits (and nights below) but then near 30 yesterday, all night, 40 "

"I'm not sure what our ground temp is with 275ft deep wells"

" Aux Heat was running the other day (and DH hadn't turned on the breaker for the 2nd strip yet, I told him to b/c more cold weather coming, we usually turn it on around Tgiving"

I don't want to hijack this thread, but I find these statements interesting. From what I understand you have a geothermal system with wells down to 275 feet and you need to heat the house with electric auxiliary heat when the temperature drops below 20 degrees? I am not the geothermal expert, but this performance sounds disappointing. People who own the Carrier Greenspeed heat pump have reported better performance.

Am I missing something here?

Yes we have 2 wells, I think they are actually 279ft deep, I don't recall why we turn on breakers to Aux Heat late Nov or so, it could be that we were finding calls to Aux Heat on the display when temp was actually above freezing outside and we thought geo could keep up (and it has). We change temp on a schedule (though not by much, we've actually been told it's better to keep it set at 1 temp), 67-68 during the day downstairs (I'm home), 66 upstairs, bring downstairs to 66 at night, but raise temp briefly to 68 upstairs around DD's bedtime and then again early AM before DH gets up. Just enough to make it bearable to jump in bed, and then to get out, though blankets are fine at 66.

A few years ago I probably could have quoted the specs but I forget now, have to look them up, It's a ClimateMaster Tranquility 27 installed summer 2007 when we built.

This post was edited by ajsmama on Mon, Jan 6, 14 at 14:58

Actually, as I recall now we picked the 2-degree difference to avoid having the Aux Heat kick in, but hoping that 2 degrees lower at night (and upstairs during the day when I'm downstairs) would save a little money in the winter. Not sure if it is better to swing from 66-68 and back down to 66 or just leave it set at 67 all the time?

And another question (or 2) about lockout. Maybe the installer set it to "no lockout" b/c GSHP will *always* have COP of 1+, so better than electric strip? Is there any situation where a closed loop GSHP would have a COP of I know this all involves the entering water temp (which is actually an antifreeze solution, so could that get below 32 F?) and leaving water temp, which I don't think I have any way of measuring (unless I just try sticking a thermometer under my cold water faucet and assume water temp is the same as what's in my loops, and maybe DHW feed from HP is the LWT, obviously very low right now, we have it piped to 2nd tank with electric coil set at 120). And then I'd have to correlate the EWT to the outdoor air temp (or at least what my sensor is reading).

But is the HP in a vertical well closed loop system ever going to get to the point where it "costs more in electricity than the BTUs it produces" as tigerdunes suggested? If so, has anybody roughly correlated the drop in COP (realizing all HPs have different COPs at 50 degrees EWT) to the air temp?

I'm still thinking outdoor air temp might not really require lockout for a GSHP, b/c COP should always be better than the heat strips so even though the condenser may be running all the time (a separate consideration), simply in terms of energy efficiency (and money, until it comes time to replace that worn-out condenser) it would be better to let the HP run and let the Aux Heat just supply whatever the HP can't?

Above 10 my unit still cycles without using strips and usually any moisture that is falling is dry enough it doesn't cause as many defrosts as a 30 degree snow or rain event. I also have noticed that if it is below 10 the unit starts to get noisy and it doesn't sound bad but not happy either.

I just got paranoid because I hate for the strips to run. I need to get a day that is hovering around 15 and lock out the pump and compare 3 hours with the heat pump off compared to letting it run.

My heat pump draws about 3500watts. The strips run about 9000.

I'm glad I only have 10kw of strips running instead of the 20 I used to have.
I lock out the strips above 35 degrees.

Do you have a GSHP, is it located in the basement, what's the basement temp when it's 10 F without the pellet stove running?

7 degrees (according to my outdoor sensor) here right now, don't know how low it got but I took the lockout back off last night, stat display read 'Wait Following schedule' at 6:35, but schedule brought temp up 1 degree at 6AM, it wasn't still trying to raise the temp, not sure why the Wait message, but then Heat On message came on (not Aux Heat) so I assume HP alone is maintaining 67 degrees.