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Old 11-23-2008, 03:07 PM   #1
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Heat Pump vs Aux Electric Heat


I have a brand new Heil Heat Pump, I think it achieves 17.5 SEER or something close to that. The heat pump is 3 Ton dual stage, the air handler is 5 ton variable speed, my house is about 1700 sqft and I live in Roanoke VA. I have one of those programmable thermostats installed, although I have it on override for now. When the outside Temp gets down below 35 or so, the aux heat kicks in a little breath of warm air but the heat pump runs continuosly until the outside temperature gets back above 35. This means continuos operation of the heat pump for 10 - 12 hours. The temperature stays EXACTLY where it is set. Since it cycles on and off above 35, then I believe everything is working correctly - you argee??

Question 2, on nights when the temperature will be below 30, is it more efficient to let the heat pump run continously or should I set the thermostat to emergency heat and let the 3 5KW strip heaters take over?? There is no outside thermostat to do this for me and I do not believe my indoor thermostat will do this as there is no outdoor temperature displayed.

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Old 11-23-2008, 05:24 PM   #2
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Heat Pump vs Aux Electric Heat


I am not in the hvac field, but I would think it would be better to let the heat pump run with help from the auxillary heat.. I know that strip heat alone is the lease cost effective.....but I would think as long as your inside temperature was maintaining the temperature you have the thermostat set at, then it's ok. I would think the only time I would shut down the heat pump and switch over to emergency heat is if it were so cold outside the heat pump + auxillary heat couldn't warm your home to the temp. set at the stat.... I just had new heat pumps put in 2 months ago, like you, high seer rating of 17 with 20K strip heat in the attic that is supposed to come on in increments of 5 kw until the temperature is satisfied. Last week it dropped down the high 20's here and i noticed my system was running the aux. heat and heat pump. It did not run non stop for 10 hours like you stated, but it would run for awhile then shut down for maybe 10 to 15 minutes and start up again. I had the temp set at 70 and it was holding the set point. So in a nutshell I would assume as long as your system is reaching the desired temp you set at the stat, let her run.

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Old 11-23-2008, 07:09 PM   #3
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Heat Pump vs Aux Electric Heat


have you read all the literature that comes with the unit ? 3 5kw strips will pull almost 60 amps thats like running your dryer, hotwater heater, and stove at the same time so is it more efficient hardly. is it more comfortable? probably.im sure that unit is running on the lower stage of heat and as such it will have longer run times.You cant compare your old unit to the new one as far as what your used to its like compareing a chevy cavilier to a corvette
i would suggest if you havent done so to read all your operating manuals
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Old 11-25-2008, 12:20 PM   #4
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Heat Pump vs Aux Electric Heat


Sounds to me like your system is not working.
I have a 3 ton heatpump rated 8.65 HSPF and 14 seer and I live in PA.
Mu unit hardly ever uses aux heat when set to 71 degrees.
I am a nut job when it comes to weatherstripping and insualtion so perhaps you have issues there??
OR you system is not laid out well at all.
Brian
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Old 11-25-2008, 12:21 PM   #5
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Heat Pump vs Aux Electric Heat


Forgot add that in above post
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Old 12-02-2008, 08:56 PM   #6
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Heat Pump vs Aux Electric Heat


If your thermostat has a CPH setting for the aux heat, set it to a lower number.
Then it will satisfy the heat demand with with the aux heaters instead of running the HP all night long.
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Old 12-03-2008, 05:02 PM   #7
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Heat Pump vs Aux Electric Heat


Thank you. I have discovered that my Aux heat is really not coming on. I have three stages, a low and high for the heat pump and then aux. What I thought was aux heat was really just the 2nd stage of the heat pump. I guess the aux heat could be coming on some, but most of the time it is just the 2nd stage of the heat pump. When it gets below 30 headed towards the mid 20's outside it seems the 1st stage runs continuously with the second stage heat pump coming on occasionally to keep the temp within the desired range. I am guessing this is energy efficient although having the air whirrring all the time gets annoying.

Based on your response of setting the CPH for the aux heat lower, I guess I could lower the 2nd Stage Heat pump number and it would accomplish the same thing??
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Old 12-03-2008, 05:06 PM   #8
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Heat Pump vs Aux Electric Heat


Yes it would.
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Old 12-03-2008, 05:12 PM   #9
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Heat Pump vs Aux Electric Heat


Below are the instructions, what numbers would you choose assuming my current settings are as recommended:
0240
First stage heat cycle rate (CPH= cycles per hour)
5 Gas or oil furnaces of less than 90% efficiency
1 Steam or gravity systems
3 Hot water systems & furnaces of 90%+ efficiency
9 Electric furnaces
[Other options: 2, 4, 6, 7, 8, 10, 11, 12 CPH]

0250
Second stage heat cycle rate (CPH)
5 Gas or oil furnaces of less than 90% efficiency
1 Steam or gravity systems
3
Hot water systems & furnaces of 90%+ efficiency
9 Electric furnaces
[Other options: 2, 4, 6, 7, 8, 10, 11, 12 CPH]

0260
Third stage heat cycle rate (CPH)
9 Electric auxiliary heat or electric furnaces
1 Steam or gravity systems
3
Hot water systems & furnaces of 90%+ efficiency
5 Gas or oil furnaces of less than 90% efficiency
[Other options: 2, 4, 6, 7, 8, 10, 11, 12 CPH]
0270
Emergency heatcycle rate (CPH)
9 Electric emergency heat
1 Steam or gravity systems
3
Hot water systems & furnaces of 90%+ efficiency
5 Gas or oil furnaces of less than 90% efficiency
[Other options: 2, 4, 6, 7, 8, 10, 11, 12 CPH]
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Old 12-03-2008, 11:14 PM   #10
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Heat Pump vs Aux Electric Heat


What model thermostat.
Since you have a heat pump with electric aux heat.
Your back up is electric.

Set your CPH for your electric aux heat to 3.
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Old 12-04-2008, 02:16 AM   #11
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Heat Pump vs Aux Electric Heat


Quote:
Originally Posted by batolson View Post
I have a brand new Heil Heat Pump, I think it achieves 17.5 SEER or something close to that. The heat pump is 3 Ton dual stage, the air handler is 5 ton variable speed, my house is about 1700 sqft and I live in Roanoke VA. I have one of those programmable thermostats installed, although I have it on override for now. When the outside Temp gets down below 35 or so, the aux heat kicks in a little breath of warm air but the heat pump runs continuosly until the outside temperature gets back above 35. This means continuos operation of the heat pump for 10 - 12 hours. The temperature stays EXACTLY where it is set. Since it cycles on and off above 35, then I believe everything is working correctly - you argee??

Question 2, on nights when the temperature will be below 30, is it more efficient to let the heat pump run continously or should I set the thermostat to emergency heat and let the 3 5KW strip heaters take over?? There is no outside thermostat to do this for me and I do not believe my indoor thermostat will do this as there is no outdoor temperature displayed.
Your aux heater is also energized when your heat pump goes on defrost mode via the white wire (aux heat terminal) connected to your thermostat. This prevents blowing cold air to your house. This is normal operation of a heat pump.
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Old 12-04-2008, 06:23 PM   #12
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Heat Pump vs Aux Electric Heat


If a dual stage heat pump is running continuously, a few things may be going on. The thermistor may not have been placed properly outdoors and could be indicating an altered temp as opposed to the actual outdoor temp. The unit could be low on refrigerant, it's typical of many installers not to pull a proper vacuum on the line-set after installation for sake of time, which can lead to non-condensables in the system or unidentified leakage. Dirty outdoor or indoor coil, filters. But realistically, when the outdoor temp gets below 35 or 30 degrees, you have to understand your heat pump in heat mode is just like your A-coil in cool, it draws in the ambient humidity and transfers the heat inside. However, at such a low outdoor temperature, the ambient humidity outside is pretty minimal, meaning your outdoor unit has to work that much harder and longer to provide ample heat. Emergency would burn more energy, but it wouldn't burn it for such an expanded period of time, granted the estimator sized it accordingly. Above 35 use AUX below 35 use EMER, you may also want to look into getting a steam humidifier, humid air feels that much warmer and you can typically set the T-stat about 2 degrees lower because your more comfortable with the humidity as opposed to dry heat (average humidity an air handler puts out is 7%, the average humidty in Arizona is 27%, think about it)
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Old 12-05-2008, 04:55 AM   #13
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Heat Pump vs Aux Electric Heat


Just because its below 35, is no reason to use emergency heat.
Thats a waste of electric. And a very high heating bill.

The heat pumps COP is still well above 2 at 30.
And many are still at 2, at OD temps of 17F.
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Old 12-05-2008, 06:14 AM   #14
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Heat Pump vs Aux Electric Heat


Quote:
Originally Posted by beenthere View Post
Just because its below 35, is no reason to use emergency heat.
Thats a waste of electric. And a very high heating bill.

The heat pumps COP is still well above 2 at 30.
And many are still at 2, at OD temps of 17F.

Corrrect! That is why I installed an external thermostat on my heat pump and set it to close @ 10F. It's a waste of electricity using electric aux heater. My electric bill was higher last winter when I did not have my external thermostat. Even though my heat pump was running continuosly during those low ambient temp. it still economical to operate.
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Old 12-05-2008, 04:58 PM   #15
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Heat Pump vs Aux Electric Heat


Thanks guys, good information. I feel better about my heat pump running alot now!

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