[Gracepreacher]

Homeowner here. I have a heat pump and need a new thermostat. My current stat has the ability to either put second stage heat on a temperature differential (1-3 degrees) or a time delay (20-40 min.). I've been looking at the White Rodgers thermostats, and this one fits my needs well as far as I can tell, but I've searched the manuals and even called White Rodgers and have not gotten an answer to this question: Does the thermostat automatically bring in stage 2 heating if the heat pump is not keeping up on a very cold day (it seems like it has to, but the White Rodgers tech support said I would have to manually switch to emergency heat). If he's wrong, and it does switch automatically to stage2/backup heat if the heat pump cannot satisfy the setpoint, how does it decide if there are no differential or time controls?

Thanks!

 

[BaldLoonie]

It is automatic. It's logic based on time and temp, you don't have to adjust anything. It will keep you warm.

 

[Gracepreacher]

It is automatic. It's logic based on time and temp, you don't have to adjust anything. It will keep you warm.

I guess I'm actually concerned that it will come on too often, as running electric heat strips is not super efficient, from what I'm told. I currently have mine set for a 2 degree differential (which rarely, if ever happens as far as I know), or 40 minutes, which does happen sometimes, though probably less than 5-10 times a year in Texas. It's usually overnight that this would come into play, so we probably don't notice a little lag in the system while we're sleeping, and we save on heat strip energy usage. Is it likely that the heat pump will wait that long before firing stage 2?

 

[joemach]

Then I would set it to the highest differential that you can (time & temp).

Use a set back less than the temp differential or none at all.

 

[Gracepreacher]

So if I find that it is still coming on too much, is there an option to wire it in such a way to lock out the auto stage 2, and I can just switch to emergency heat on those few very cold days/nights?

 

[54regcab]

Some thermostats have the option for an outdoor sensor that locks out the strips below a certain outdoor temp.

 

[Gracepreacher]

Some thermostats have the option for an outdoor sensor that locks out the strips below a certain outdoor temp.

Interesting. I would rather lockout the strips UNLESS the outdoor temp is below a certain point. Then, I'd want strips only (no compressor). I bet I could have that too for the right money, but now we're getting into another issue.

So, without an outdoor sensor, can I lockout my strips (in terms of aux heat) just by wiring it a certain way (or leaving a wire "undone"), but still have access to emergency heat by the manual switch on the stat? Or, are those on one wire?

 

[joemach]

One of the best thermostats to do this is the Honeywell 8000 series. If you don't have enough wires run to the outside already, you can set up an outdoor sensor via wi-fi. Look for Honeywell 8321. Just make sure it is the white screen and not the green screen.

You can lock out the back up heat from coming on above a certain temp. You can also set a "Droop", so that for some reason the system can't keep up even though it is above the back up heat lock out temp it will come on to keep you comfortable.

 

[Gracepreacher]

One of the best thermostats to do this is the Honeywell 8000 series. If you don't have enough wires run to the outside already, you can set up an outdoor sensor via wi-fi. Look for Honeywell 8321. Just make sure it is the white screen and not the green screen.

You can lock out the back up heat from coming on above a certain temp. You can also set a "Droop", so that for some reason the system can't keep up even though it is above the back up heat lock out temp it will come on to keep you comfortable.

Now that sounds pretty cool. But just as I suspected...you gotta pay up for that. My current RobertShaw thermostat has all the features/control I need, at around $50, but it does this strange thing in the shoulder seasons where it seems to fall asleep when the system doesn't run for a long time, and then it doesn't reactivate when the house finally reaches the setpoint, so it comes on a few degress behind, THEN it ends up activating the strips, even though I have them on the max 40 minute delay/3 degree differential (and this is while it may be 40 degrees outside, so they shouldn't be coming on). It's so frustrating...a cold front will come in after a mild period and sometimes my wife and I will even "catch it" not reading right. Do you guys think a replacement of the same model is likely to fix this? I've been dealing with it for years now and have about had it. My gut is to run far away from RobertShaw, but when I look at the Honeywell and White Rodgers options in the same price range, they don't give as much control, and I really can't increase my budget.

 

[joemach]

Honeywell thermostats will maintain within one degree of set temp. It could be that you have some sort of deadband set.

You will pay for the new Honeywell that I mentioned in less than one season. Well worth the investment.

My belief is that YOU should be in control of your comfort and energy, not your system. The above mentioned thermostat allows that to happen.

It has on screen programming with an onscreen help file.

The actual number is: Honeywell TH8320R1003

There is even a Windows app that you can download to walk you through the set up programming.

Honeywell out did themselves on this one.

 

[Gracepreacher]

OK. I'm thinking through this again. I have my stage 1 differential set at 2 degrees. We are generally still comfortable with this, and it causes the system to start less, and I was told that less starts and longer runs are the most efficient (and the best for removing humidity in the summer, which is a BIG deal in terms of comfort in my book...maybe more than temperature sometimes). Is it possible that this is the cause of our problem in the shoulder seasons? I feel like if I switch the stage 1 differential to 1 degree, it's going to run more, cost more, remove less humidity in the summer, oh yes, and run more cold air from the attic ducts at the beginning of the ON cycle in the winter. It's hard for me to believe that this setting is our problem if we don't notice it anytime except for the shoulder seasons (when the system goes for days without running at all in good ole North Texas).

I agree completely that I should be in control of my system. That is what I'm trying to do. I'm just trying to do it for less money, and it seems like if the RobertShaw that I have would work right, it would be just fine feature-wise.

Is RobertShaw a "cheapo" brand?

 

[joemach]

Not familiar with Robert Shaw. I am sure they make high end and low end thermostats, like everyone else. If it is an older model, I would look at an upgrade. A lot has changed in the past few years thermostat-wise. Technology will keep advancing.

Maybe the best thing to do is to set a higher differential in the summer than the winter.

I am assuming you have a single stage heat pump with second stage heat being electric back up.

 

[54regcab]

Spend the money and get a thermostat with an outdoor sensor. Worth every penny on a heat pump system. Most have 2 settings, 1 for locking out the strips above a certain temp, 1 for locking out the compressor below a certain temp. You could set it to lock the strips out above 40f degrees and lock out compressor below 25f. Between 25f and 40f heat pump would be stage 1, strips stage 2. Emergency heat mode overrides outdoor temp sensor, allows strip only heat to run at any temp.

 

[beenthere]

At what temp do you intend to lock out the heat pump/compressor. If you want high efficiency, then locking out the compressor at any temp above its COP of 1.3 is a loss of efficiency.

 

[54regcab]

Some will lock out the compressor at relatively high outdoor temps because the object to the relatively cool air coming from the registers. Some have older heat pumps that don't work well when it gets down into the 20's. Others complain that they think they are using more energy since they never hear it shut off.

 

[beenthere]

Some will lock out the compressor at relatively high outdoor temps because the object to the relatively cool air coming from the registers. Some have older heat pumps that don't work well when it gets down into the 20's. Others complain that they think they are using more energy since they never hear it shut off.

The OP has only posted about efficiency.

Even older heat pumps that "didn't work well" in the 20s, had COPs of 1.5 at 17°F outdoor temp.

 

[Gracepreacher]

Not familiar with Robert Shaw. I am sure they make high end and low end thermostats, like everyone else. If it is an older model, I would look at an upgrade. A lot has changed in the past few years thermostat-wise. Technology will keep advancing.

Maybe the best thing to do is to set a higher differential in the summer than the winter.

I am assuming you have a single stage heat pump with second stage heat being electric back up.

My thermostat is about six years old.

I liked you idea about setting a lower differential in winter. I checked again...the heat pump differential is already at 1 degree...I could go to .5 in winter, but that just doesn't seem like a good move.

Yes...you got my system right.

As much as I'd love a fancy thermostat and remote sensor, I just cannot justify the cost...and I'll go ahead and say that I doubt the one year payback period mentioned.

Would you guys choose a Honeywell focus pro 5000 series over the White Rodgers in my original post? They are similarly priced, but they use the ever so confusing to me "cycles per hour" system instead of differential time and temps. Seems nebulous to me when I start to look it up. At least I did find where the WR gives a choice between a couple of differential options.

Thanks for the help.