Heat Pumps and Electric Heating - Geothermal calling for aux heat too often...
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jason1234
10-06-09, 08:36 PM
Had a new geothermal system installed in a new house. Moved in halfway through last winter. Noticed the aux heat was coming on a lot. Didn't really bother to investigate it.
Just starting to get cold here this fall. I just adjusted the temperature on the thermostat increasing it by one degree Celsius (to 22). The aux heat was called for by the thermostat about 45 seconds after I changed the temperature.
Why is the aux heat coming on so soon? Anything I can do to stop this?
Details:
-temperature outside is 3 degrees C
-thermostat is a Honneywell VisionPro TH8320U. Manual: http://customer.honeywell.com/techlit/pdf/PackedLit/69-1896.pdf
-system is a closed loop design
-water furnace brand heat pump rated at 44,500 BTUH at 32 degrees F
Just starting to get cold here this fall. I just adjusted the temperature on the thermostat increasing it by one degree Celsius (to 22). The aux heat was called for by the thermostat about 45 seconds after I changed the temperature.
Why is the aux heat coming on so soon? Anything I can do to stop this?
Details:
-temperature outside is 3 degrees C
-thermostat is a Honneywell VisionPro TH8320U. Manual: http://customer.honeywell.com/techlit/pdf/PackedLit/69-1896.pdf
-system is a closed loop design
-water furnace brand heat pump rated at 44,500 BTUH at 32 degrees F
Jay11J
10-06-09, 09:39 PM
The t-stat sees a change in temp, and it will call for Aux.
The only way to advoid that is adding an outdoor sensor to "Lock" out the aux heat.
Are you changing the set point temps often, or using the program mode?
The only way to advoid that is adding an outdoor sensor to "Lock" out the aux heat.
Are you changing the set point temps often, or using the program mode?
jason1234
10-07-09, 06:12 AM
Thanks, Jay. I'll look into getting the outdoor sensor.
I mostly use the program - just made an adjustment to the temperature after getting a chill last night. I remember last winter that when the tstat was changing temperatures based on the program (doing its "recovery" thing), the Aux would still kick in. Seems like the outdoor sensor would solve the problem.
Any suggestions on specific settings for the aux lockout temperatures? I am from Canada - we get cold winters. -30 degree overnight temperatures will be the norm in a few months, with occasional colder temps.
Thanks again for the help!!
I mostly use the program - just made an adjustment to the temperature after getting a chill last night. I remember last winter that when the tstat was changing temperatures based on the program (doing its "recovery" thing), the Aux would still kick in. Seems like the outdoor sensor would solve the problem.
Any suggestions on specific settings for the aux lockout temperatures? I am from Canada - we get cold winters. -30 degree overnight temperatures will be the norm in a few months, with occasional colder temps.
Thanks again for the help!!
Jay11J
10-07-09, 08:00 AM
My best advise rather than getting an outdoor sensor, just set the temp and forget it.
With ANY heat pump system, you don't save money doing the program set back.. HP don't recover like gas furnace, and the savings are gone when you use AUX heat.
Also, if you do the set back, and have the AUX locked out, it going to take the system so long to recover.
But, if you must or like the cool bedroom at night, then yes, order the outdoor sensor. Hopefully you are able to fish a new set of wire from the t-stat to the outdoors? The only draw back on this model of t-stat, the lock out can only go as low as 40˚F (4˚F).
If your HP is a variable speed system, maybe won't hurt to upgrade the t-stat to the Honeywell IAQ t-stat. The IAQ will lock out the Aux heat down to 5˚F (-15˚C)
With ANY heat pump system, you don't save money doing the program set back.. HP don't recover like gas furnace, and the savings are gone when you use AUX heat.
Also, if you do the set back, and have the AUX locked out, it going to take the system so long to recover.
But, if you must or like the cool bedroom at night, then yes, order the outdoor sensor. Hopefully you are able to fish a new set of wire from the t-stat to the outdoors? The only draw back on this model of t-stat, the lock out can only go as low as 40˚F (4˚F).
If your HP is a variable speed system, maybe won't hurt to upgrade the t-stat to the Honeywell IAQ t-stat. The IAQ will lock out the Aux heat down to 5˚F (-15˚C)
Houston204
10-07-09, 08:18 AM
I have never seen Auxillary heat strips on a Geothermal heatpump before. (It's 84 degrees over here today, so this may be because of my location) Are you confident that you have heat strips in your unit?
If you do not have strips, you should reconfigure option 170 on your stat.
If you do not have strips, you should reconfigure option 170 on your stat.
Jay11J
10-07-09, 08:21 AM
I have never seen Auxillary heat strips on a Geothermal heatpump before. (It's 84 degrees over here today, so this may be because of my location) Are you confident that you have heat strips in your unit?
Houston, Most of the Geothermo up north has strip heat cuz we can get pretty cold up here. Here in MN, we can get down to -25˚, and some time the GEO may not be able to keep up, and also the person will have back up heat if something was wrong with the GEO.
Houston, Most of the Geothermo up north has strip heat cuz we can get pretty cold up here. Here in MN, we can get down to -25˚, and some time the GEO may not be able to keep up, and also the person will have back up heat if something was wrong with the GEO.
jason1234
10-07-09, 07:37 PM
Thanks for the info, guys!! Much appreciated!!!!
The heat pump is a dual stage one. And it does have an aux / emergency backup electric heat built in.
Maybe upgrading to the IAQ is the way to go. I do like having the nightime temperature a couple degrees cooler. I guess it doesn't really bother me to have the HP running for a while to bring the temperature back up in the morning.
Thanks again for the help - lots of things I am learning about the new GEO system! :-)
The heat pump is a dual stage one. And it does have an aux / emergency backup electric heat built in.
Maybe upgrading to the IAQ is the way to go. I do like having the nightime temperature a couple degrees cooler. I guess it doesn't really bother me to have the HP running for a while to bring the temperature back up in the morning.
Thanks again for the help - lots of things I am learning about the new GEO system! :-)
Jay11J
10-07-09, 07:42 PM
Glad to help out.. What is the model # of your HP?
jason1234
10-07-09, 07:54 PM
It is a waterfurnace Synergy 3D WaterFurnace Residential Product Line : Synergy3D (http://www.waterfurnace.com/products.aspx?prd=Synergy3D)
The "as built" book the installer left me lists the HP as SDV064A121CTL. Sounds more like a serial number to me, but perhaps you can infer something from it :-)
The "as built" book the installer left me lists the HP as SDV064A121CTL. Sounds more like a serial number to me, but perhaps you can infer something from it :-)
Jay11J
10-09-09, 04:17 PM
The "as built" book the installer left me lists the HP as SDV064A121CTL. Sounds more like a serial number to me, but perhaps you can infer something from it :-)
That number is a model #, it's a 5 ton unit, variable speed, and can be used with radiant floor heat.
You must have a very large home if you got something that large? Do you have radiant floor heat tied to it?
That number is a model #, it's a 5 ton unit, variable speed, and can be used with radiant floor heat.
You must have a very large home if you got something that large? Do you have radiant floor heat tied to it?
jason1234
10-11-09, 08:46 AM
I have a 1600 sq ft house. Radiant floor heat in basement (along with forced air). Radiant floor heat is sole source of heat for double car garage. The installer had to set it up so the compressor (I think) would automatically kick into it's second stage whenever heating the water for radiant heat as it wasn't heating th water enough. It is set to heat water to 100 degrees.
The system is also tied into the DHW although I don't think it make much sense. It was only heating DHW to about 115 degrees, so the installer hooked up the electric HWT back up to power to heat DHW to 140. Seems to me that the geo system can't be doing anthing for DHW as the electric thermostat will lock in long before the water temp reaches the 115 degrees that the geo system will provide. Oh well.
The system is also tied into the DHW although I don't think it make much sense. It was only heating DHW to about 115 degrees, so the installer hooked up the electric HWT back up to power to heat DHW to 140. Seems to me that the geo system can't be doing anthing for DHW as the electric thermostat will lock in long before the water temp reaches the 115 degrees that the geo system will provide. Oh well.