Need thermostat with auto HP / Eheat adjust


  #1  
Old 12-08-10, 04:52 PM
D
Member
Thread Starter
Join Date: Dec 2010
Location: USA
Posts: 41
Upvotes: 0
Received 0 Upvotes on 0 Posts
Need thermostat with auto HP / Eheat adjust

Does anyone know of a heat pump thermostat with an outdoor temp sensor that will automatically switch between heat pump and eheat mode based on outdoor temperature? I would like to be able to lock out the heat pump when the outdoor temp drops below 30 to save wear on the heat pump.
 
  #2  
Old 12-08-10, 05:10 PM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 16,984
Upvotes: 0
Received 0 Upvotes on 0 Posts
HOneywell VisionPro or IAQ will do the job.

30˚ is way too warm to shut off the HP unless your gas rates are dirt cheap?

Most HP I have the shut off around 10˚ to 20˚ (Depends on the gas/electric rates) An example, my parents system, we could have it shut off at -10˚ with the rate they are getting but the HP is not able to keep up under 10˚, so we have it switch over to gas.

What is your gas and electric rate?
 
  #3  
Old 12-08-10, 05:24 PM
D
Member
Thread Starter
Join Date: Dec 2010
Location: USA
Posts: 41
Upvotes: 0
Received 0 Upvotes on 0 Posts
I have an older system with SEER 10 rating heat pump with electric strip heaters. When the temp is in the 20's it runs a long time on heat pump without turning on the strip heaters. The fan noise is agravating too. I would like to cut out the heat pump and run straight strip heatere below 25 or so outoor temp. Will the VisionPro or IAQ allow this on this type of system?
 
  #4  
Old 12-08-10, 05:59 PM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 16,984
Upvotes: 0
Received 0 Upvotes on 0 Posts
The standard retail (no outside sensor) Honeywell will turn on the Aux strip to help cut down on the HP load as needed than just shutting the HP off and going all electric.. Your power bill may go up 2 to 3x's of you went all electric.

Otherwise, yes both IAQ or VisionPro can work.
 
  #5  
Old 12-08-10, 06:09 PM
D
Member
Thread Starter
Join Date: Dec 2010
Location: USA
Posts: 41
Upvotes: 0
Received 0 Upvotes on 0 Posts
The house is pretty tight and the aux strips turn on rarely. I have the standard 7-day programmable Honeywell from home depot. There doesn't seem to be a way to adjust the sensitivity of when the aux heat turns on. Aux heat will turn on if I set the temp up a few degrees so I know it is wired correctly.
 
  #6  
Old 12-08-10, 06:18 PM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 16,984
Upvotes: 0
Received 0 Upvotes on 0 Posts
What model is the air handler, and how many Khw is the heat strip? the Pro line is able to stage the strip than on at once.
 
  #7  
Old 12-08-10, 06:28 PM
D
Member
Thread Starter
Join Date: Dec 2010
Location: USA
Posts: 41
Upvotes: 0
Received 0 Upvotes on 0 Posts
I think it is a ADP 2 ton air handler and a 10kw single stage strip. The aux and e terminals are wired together.
 

Last edited by Dave-VA; 12-08-10 at 06:47 PM.
  #8  
Old 12-08-10, 06:48 PM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 16,984
Upvotes: 0
Received 0 Upvotes on 0 Posts
Ok, the IAQ is going to be too much for your system.. The VisionPro TH8320 is all you need along with the outdoor sensor. Are you able to fish up new set of wires up to the stat and outside?
 
  #9  
Old 12-09-10, 02:44 PM
D
Member
Thread Starter
Join Date: Dec 2010
Location: USA
Posts: 41
Upvotes: 0
Received 0 Upvotes on 0 Posts
I found this setting on both the TH8320 and the RTH7500 I have.
Cycles per hour (cph) for Em Heat 0270
9 Cycles per hour (cph) for Emergency Heat 1-12
1-12 is available; typical s e t t i n g s :
3 cph for hot water systems or high efficiency (90% or better) fossil fuel f o r c e d a i r s y s t ems .
5 cph for standard fossil fuel forced air s y s t ems .
9 cph for electric heat systems.
Only shown if 2 heat/1 cool or 3 heat/2 cool heat pump is selected.

Would changing this setting to a lower number make the eheat come on more quickly? It is currently set at 9 the default for heat pump system.
 
  #10  
Old 12-09-10, 02:57 PM
D
Member
Thread Starter
Join Date: Dec 2010
Location: USA
Posts: 41
Upvotes: 0
Received 0 Upvotes on 0 Posts
Jay,

Looking further ahead in the TH8320U manual I see the setting I need.

Heat Pump Compressor Lockout or (Balance Point)0350
0 No compressor lockout.
15, 20, 25,
30, 35, 40,
45

I will look into getting one. I have a few spare wires so installing should be fairly easy. Can you give me a lead on the temp sensor part number as well?
 
  #11  
Old 12-09-10, 03:07 PM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 16,984
Upvotes: 0
Received 0 Upvotes on 0 Posts
I always suggest to people to set the heating CPH to 3, and have good respond on comfort with this.

For the outdoor sensor, you need a set of wire by itself, you can't share it with others otherwise, will get a false reading.

The outdoor sensor # is. C7089U
 
  #12  
Old 12-09-10, 03:35 PM
D
Member
Thread Starter
Join Date: Dec 2010
Location: USA
Posts: 41
Upvotes: 0
Received 0 Upvotes on 0 Posts
I will try setting CPH down to 3 and let you know what happens (before I buy the other thermostat!)
 
  #13  
Old 12-10-10, 10:32 AM
D
Member
Thread Starter
Join Date: Dec 2010
Location: USA
Posts: 41
Upvotes: 0
Received 0 Upvotes on 0 Posts
Now that I think about it a little more it seems like a good thermostat should have an adjustment to control how much the heat pump runs, and beyond a set amount it would judiciously apply the strip heaters. Cutting the heat pump out entirely seems like a waste. It doesn't seem like it would take an outdoor thermometer to determine this. It seems like it could sense the rate of heat loss or temperature changes indoors and adjust the use of the heat strips accordingly.
 
  #14  
Old 12-16-10, 05:12 PM
D
Member
Thread Starter
Join Date: Dec 2010
Location: USA
Posts: 41
Upvotes: 0
Received 0 Upvotes on 0 Posts
I have heard of multi stage heat strips and thermostats with m1 and m2 terminals. If I were to add a 2nd strip heater relay so the two 5kw strips could operate separately, would the honeywell thermostat be able to operate the system more efficiently?

See this other thread: http://forum.doityourself.com/heat-p...ttings-md.html
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: