Heat Pump vs. Aux Only

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  #41  
Old 01-18-11, 05:32 PM
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you are missing the purpose the OP started this thread which to automatically add aux heating as the outdoor temp drops so you dont have to manually switch a toggle switch

white rogers outdoor stat open on rise
 
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  #42  
Old 01-18-11, 09:27 PM
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My system is entirely contained outdoors. There is no indoor fan. The t-stat sends a signal down to the unit when it wants the fan turned on. This is the fan signal I'm thinking of tapping into, in the outdoor unit control area.
I realize that as long as I have it set up this way, if I turned the fan on the strips will come on, as long as it is cold enough outside.
I understand the logic of using the compressor circuit, but sometimes it feels like the fan is running without the compressor and I would like the air to not be so cold then. It just feels like it is defeating the purpose to run the system, get the temp up, then pump cold air through the house, dropping it back down.
If there isn't anything dangerous about doing it this way, I'm going to try it and see if it works as I expect. I'll report back in a few days.
 
  #43  
Old 01-19-11, 03:54 AM
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there is a cool off delay setting that needs changed. I misunderstood that your heatpump is a package unit. I thought it was a split system. sorry for the confusion
 
  #44  
Old 01-19-11, 05:19 AM
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Originally Posted by hvactechfw View Post
there is a cool off delay setting that needs changed. I misunderstood that your heatpump is a package unit. I thought it was a split system. sorry for the confusion
I'd rather do this right, and if piggybacking off the compressor signal is the best way to do it, I'll go that way. This hinges on being able to eliminate that cold air issue, though.
I'm not finding anything in the T-stat or HVAC manuals that is clearly labeled as a "cool off delay". Is there another name it might be under? It is a logical option to have, so I figure it is there, I'm just not recognizing it.
By the way, I appreciate the rather amazing level of patience you've demonstrated while helping me out with this. Is there some way of giving "attaboys" to contributors?
 
  #45  
Old 01-19-11, 02:32 PM
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as far as attaboys...... thank you.....there may not be a cool off delay.... what is the model # of your unit? (if the sun has not faded it away.) When is the cold air issue? when it first comes on?
 
  #46  
Old 01-19-11, 05:31 PM
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Originally Posted by hvactechfw View Post
as far as attaboys...... thank you.....there may not be a cool off delay.... what is the model # of your unit? (if the sun has not faded it away.) When is the cold air issue? when it first comes on?
Armstrong 4PHP13E36P-1A

When it comes on and when it shuts off. The second is the more annoying to me, though.
 
  #47  
Old 01-19-11, 06:16 PM
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from what I can find on your system and thermostat there is no adjustment. also from what I can find the fan should shut off immediately when the stat stops calling for heat or cool.
 
  #48  
Old 01-19-11, 06:52 PM
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Originally Posted by hvactechfw View Post
from what I can find on your system and thermostat there is no adjustment. also from what I can find the fan should shut off immediately when the stat stops calling for heat or cool.
I forgot to update the thermostat. I mentioned in an earlier post that I was not happy with the Honeywell's 1 degree temperature swing. I found a t-stat at Lowes that has an adjustable swing. It is a Hunter Easy Saver model 44860.
 
  #49  
Old 01-19-11, 07:19 PM
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system settings 8 residual cooling timer default of 30 seconds. this potentially will affect the heating as well because you are using a HP. set this to 0
 
  #50  
Old 01-31-11, 05:57 AM
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Update

To those who have tried to help and appreciate closure.
I installed the external thermostat and in principle it works, but at this point, in practicality, it doesn't.
The problem is that the control area is not completely exposed to the outside temperature so the thermocouple never closes the relay. I brought a cup of ice water outside and put the thermocouple in it and sure enough the strips turned on. I would drill a couple of holes in the bottom of the access panel (it is not insulated) but I'm not sure that would be enough and am concerned about allowing excess moisture into the area.
For the time being I have mounted a switch on the wall that, when in the "on" position, connects the fan relay out to the heater strip circuit. When it is cold enough to need the help, I flip the switch on. It works, although eventually I'll have to figure out a way to get the outdoor thermostat to work properly, as I want the whole thing to be automated.
 
  #51  
Old 01-31-11, 10:36 AM
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expose the bulb of the outdoor stat to ambient air. drilling a hole in the bottom of the electrical panel is fine. depending on the stat you purchased this can be done, however if you make a hole, fill it with silicone of putty to keep critters out of electrical compartment
 
  #52  
Old 01-31-11, 12:49 PM
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mid_life_crisis: The easiest way to achieve what you want your system to do is to use a Honeywell 8000 thermostat. The 8000 will turn on the heat strips while the heat pump is running (both at the same time) when it determines that the heat pump is running at 90% capacity. They call this droopless control. The 6000 you have and most other heat pump stats will only turn on the heat strips when the inside temp has dropped 2 or 3 degrees. The 8000 will cycle the heat strips to maintain set point. Here is a quote from the 8000 manual.

"Vision Pro 8000 Second Stage Heat Control.
While maintaining set point, several factors affect when 2nd
stage (aux heat) energizes such as load conditions, environmental
conditions, P+I control, and home insulation. The second
stage energizes when the thermostat senses 1st stage is
running at 90% capacity. This operation is droopless control."
 
  #53  
Old 01-31-11, 01:42 PM
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One problem I have is that the access panel is in full sun most of the day. I'm thinking in terms of drilling a few very small holes in a pattern near the bottom of the access panel and hanging the bulb inside near the venting but out of direct sunlight.
 
  #54  
Old 01-31-11, 01:47 PM
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Jeggs, thanks for the t-stat recommendation. Do you know how it determines the % of capacity?
 
  #55  
Old 01-31-11, 02:01 PM
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It uses an algorithm based on deviation from setpont, how long the heat pump runs to maintain setpoint etc. Another quote from the manual:

"P+I Control
The thermostat microprocessor-based control requires that
the user understands temperature control and thermostat
performance. A conventional mechanical or electronic
thermostat does not control temperature precisely at setpoint.
Typically there is an offset (droop) in the control point as the
system load changes. This is a phenomenon that most people
in the industry know and accept. Many factors contribute to
offset including switch differential, thermal lag, overshoot,
cycle rates and system load.
The thermostat microprocessor simultaneously gathers,
compares and computes data. Using this data, it controls a
wide variety of functions. The special proprietary algorithm
(program) in the thermostat eliminates the factors causing
offset. This makes temperature control more accurate than
the conventional mechanical or electronic thermostats. The
temperature control algorithm is called proportional plus
integral (P+I) control.
The thermostat sensor, located on the thermostat or remote,
senses the current space temperature. The proportional error
is calculated by comparing the sensed temperature to the
programmed setpoint. The deviation from the setpoint is the
proportional error.
The thermostat also determines integral error, which is a
deviation based on the length of error time. The sum of the
two errors is the (P+I) error. The cycle rate used to reach and
maintain the setpoint temperature is computed using the P+I.
The addition of the integral error is what differentiates the
thermostat from many other electronic and mechanical
thermostats."

I have an 8000 with a heat pump and it works just as described. When the heat pump can no longer hold setpoint the heat strips cycle to maintain setpoint while the heat pump is still running. The room temp never drops. As outside temps get lower, the heat strips cycle longer to maintain setpoint.
 
  #56  
Old 01-31-11, 02:31 PM
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My wife is going to kill me. At this rate I'm going to have a thermostat museum.
 
  #57  
Old 01-31-11, 02:33 PM
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Originally Posted by mid_life_crisis View Post
My wife is going to kill me. At this rate I'm going to have a thermostat museum.
Lol. You might want to stop by the jewelry store after you buy your Honeywell 8000.
 
  #58  
Old 01-31-11, 02:38 PM
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By the way the Honeywell model number you need for a 2 heat 1 cool heat pump is TH8320. They also have the TH8321 which has a humidity control feature built in for the summer.
 
  #59  
Old 02-01-11, 07:03 AM
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What most of us are really trying to find out is at what point do we turn the heat pump off if we don't live in southern Florida. I installed an outside thermostat to do this. I know they say we need to pay somebody to survey the house and factor in the insulation, windows, siding, etc. This should have been done when the system was installed but most so called experts are charging you to size the unit for cooling, not heating. What have we done? We are now running a unit that usually only cools. We are now running 12 months out of the year instead of during the summer. We are heating from (tomorrow night) minus six degrees to 72. This is a swing of 78 degrees. We normally cool at the most from 100 degrees down to 70, a swing of 30 degrees. What a difference and the colder it gets the less efficient. The bottom line is that the unit is going to last half as long and require twice as much maintenance that nobody is figuring in. Right now I have freezing rain and had to shut the heat pump off because it was shaking like a washing machine on spin cycle because of ice on the fan blades. If I wasn't home I guess it would shake the fan off the motor mounts eventually. I installed my two units myself and do all repair work, but then I worked in hardware maintenance, electronic technician, and as a machinist before retiring. Some don't have this option and have to pay for repairs that trust me will be several hundred dollars even for something as simple as a compressor contactor or reversing valve, etc. My wife hates the cool air from the vents when it gets below freezing outside. My units can keep up to well below freezing without auxiliary heat, but its like sitting under an overhead fan.
As a user in the midwest my solution is to install an outside thermostat with a set point of around 25 degrees and go to the heat strips only for temperatures any lower. I could use both the heat pump and heat strips in tandem with this outside thermostat, but why? It beats having to be home to turn the thermostat over to the auxiliary heat when it gets really cold.
Actually today we are supposed to get up to 1/2" of ice on the powr lines. I'll probably be trying to stay warm with the fireplace when the power goes off.
 
  #60  
Old 02-01-11, 08:26 AM
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Phil - Mo I also live in the Midwest and have a heat pump with electric strip auxiliary and with the adverse weather the Midwest brings all of your points are valid. A lot of people around here are installing heat pump systems with a fossil fuel (natural gas, propane etc) back up furnace as their auxiliary heat. The initial cost is more but the heat pump only runs in mild weather (say down to 35 degrees) and then the system switches over to the gas furnace automatically with the appropriate thermostat and outdoor temp sensor. This eliminates the cool vent temps, the ice damage to the heat pump you mentioned since the heat pump is not running in freezing temps, and saves wear and tear on the heat pump itself. Also a gas furnace is a lot cheaper to run than heat strips when it gets really cold.
 
  #61  
Old 02-01-11, 02:31 PM
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I installed a Honeywell 8220U1003 with outdoor temp sensor to lock out the heat pump below a certain temperature. Currently I have the lock out point set at 25. I live in Virginia so it mostly only gets below 25 at night in January. So I figure I will save around $200 a year with an automatic control versus switching back and forth to eheat manually.

This thermostat is a commercial model I found used on ebay. I had to run a separate wire for the outdoor temp sensor. I learned of this thermostat on this forum.

http://forum.doityourself.com/thermo...ml#post1798402
 
  #62  
Old 02-02-11, 06:23 AM
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jeggs -- Sounds like we have a similar setup. Sorry I'm getting off the subject but I'm snowed and iced in today.
I live in a rural area and took three years to build a house on my farm. I'm retired except for raising cattle and putting up hay and fixing fence, etc.
I looked long and hard about using propane instead of electric heating coils for backup but when I was building, the price of propane was going up and down so much I decided to go all electric since that was what I had in the city when I worked for a living. I did put in a good size propane fireplace to keep the house above freezing if the electric goes out. I am in the middle of 240 acres at the end of the coop electric co. line and do lose power occasionally year round and sometimes slow in getting it back on. I went out and bought an electric generator for this storm and as luck would have it the electric stayed on. We got 2 inches of ice and sleet and some snow on top and going to minus 6 tonight. I think this storm is headed your way today. I guess it would have been cheaper to go to Florida like most retirees but the cows would have starved with the fields covered in ice.
A lot of country people around here use outside wood furnaces, and it seems a waste not to use all the firewood I have available, but I'm getting to old to cut it and haul it in, and then try to talk my wife into going outside in the snow to load it up (that's the woman's job, right). Sure is easy to just turn the thermostat up.
 
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