hydronic baseboard heat with heat pump


  #1  
Old 06-18-14, 12:16 PM
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hydronic baseboard heat with heat pump

My house is heated by a single zone hydroponic boiler (in the basement) system using baseboard radiators and cooled by a separate outside ac unit with an air handler in the attic. I just replaced the AC unit, A-frame and lines with a new 14 seer heat pump setup. I have the system cooling fine but, I am not sure how to go about wiring up the thermostat to work best with my boiler and heat Pump.

should the boiler be hooked up as auxiliary or emergency heat?

The heatpump manufacturer says the w1 should go from the thermostat through the air handler and and on to the heat pump.

is that still necessary? and how best to wire that?

Any suggestion on best thermostat?

originally I was going to get a Honeywell RTH3100C then I was thought maybe the TH5220D would be a better choice for my situation. But I do find the Nest enticing.
 
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Old 06-18-14, 02:40 PM
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Welcome to the forums.

What needs to be considered is if you want both heating systems to operate at the same time.

Since you have two distinct plants...... heating and cooling..... you need a thermostat that can operate two units. The RTH3100C cannot. The TH5220D will work for your application.

I don't know if the nest will operate two units.

Houston, the forum pro, will stop by. He knows the best thermostats to use in most applications.
 
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Old 06-18-14, 04:41 PM
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Just some things I was thinking of while I had dinner.

Where will the thermostat go ?
Where is the single zone of heat ?

Will one thermostat be in a location where it will control both effectively ?
 

Last edited by PJmax; 06-18-14 at 05:12 PM.
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Old 06-19-14, 03:28 AM
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First and foremost, thank you so much for taking your time to help me.

I知 sure I知 misunderstanding you question but the thermostat is located in the dining room.

By single zone I was referring to the entire house. One heat pump with one air handler, one boiler and one thermostat to rule them all.

I was envisioning using the hydronic system as an auxiliary and/or emergency heat system for the heat pump system.

One of my concerns is what to do with the m1 wire running from the heatpump back to the air handler. Does it go all the way back to the thermostat? I was planning to guess it is to signal the defrost cycle from the heatpump but I知 not certain that is useful with a hybrid system.

I知 also not completely sure I understand how to wire in the boiler as the auxiliary heat on the thermostat.
 
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Old 06-19-14, 04:05 PM
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I will assume that you have a single stage heat pump.

You will want a thermostat that has a balance point type of switching.
It should be able to be set to switch to the boiler when the outdoor goes below either the safe or efficient operation point of the heat pump.

The boiler R & W should go to the W contact (or W1) of the stat, but it needs to be isolated from the heat pumps 24 VAC circuit. Many times the stat has an Rc and an Rh. the Rc switches with Y, G, O/B and Y2 if it's 2 stage. L may also be used with the heat pumps 24VAC circuit.
The Rh and W (w1) would be wired to the boiler downstairs.
If you cannot isolate W (w1) from the heat pump circuit you will need a relay between W and C. then the dry contacts can switch the boilers R and W.

Makes sense ?
 
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Old 06-19-14, 08:43 PM
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Yes the heatpump is single stage, it is a Ducane 4HP14L.

I知 not certain what a thermostat with balance point type switching would be.

I知 thinking getting a Honeywell RTH6350 until I figure out if I need something more. I致e seen some suggestions that I might need a prestiage IAQ or a visionPro IAQ with an external temperature sensors.

Here is the schematic as I thought it would start.
[ATTACH=CONFIG]33460[/ATTACH]

Here is a link to the installation instructions:
https://customer.honeywell.com/reque...form=69-2416ES

Unfortunately this thermostat does not have a C so I have to rely on batteries.

I think the unit comes with a jumper on R and RC. I figured I would need to remove that jumper put the R from the boiler to R on the thermostat and the W on Aux. and then possibly jump E and Aux.

But that seems awful simplistic considering I was hearing others talk about fossil fuel kits or more sophisticated thermostats with external sensors (I guessed to control the lockouts).

Currently the W1 is running from the heat pump to the air handler but I have it capped off there. I知 not really sure what, if anything I should do with that W1.

I am not sure I know what 電ry contacts are. ??

Does that mean I will need to manually switch from cold to heat when I am ready for the boiler to heat the house and not the heat pump? So the furnace will really not work as an Auxiliary heat system but as an emergency heat system?
 
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Old 06-20-14, 12:49 PM
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I had a suggestion that I use the focusPro 6000 instead of the RTH6350. As far as the wiring the only difference is the C allowing it to run on house power and the combining of the Aux and the E (Aux/E).

What are your opinions or suggestion regarding those two or are there any other thermostat you would suggest?

The red and green wires coming from my thermostat are wire backwards at my blower housing. the red wire, from the thermostat, is connected to the wire leading from the post on the controller board labeled R and the green wire, from the thermostat, is connected to the wire leading from the post labeled G. It seems to be working correctly and has for some time.

Thanks,
Jay
 

Last edited by GregH; 09-14-14 at 04:48 AM.
  #8  
Old 06-24-14, 04:28 PM
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an outdoor sensor gives you the added ability to use a balance point setting, what this means basically is that the thermostat will choose which system is more efficient. As the outdoor temp drops, so does your HP's efficiency.
At some point the outdoor temp becomes to cold to extract heat from it, at least very efficiently.
It's at this point that you want to stop using the heat pump and start using your back up fuel. Running a HP in cold outside air makes it run harder, and this will reduce its life span. Spending a little extra on oil or propane over the course of the year could add years to that HP's life.

I think you should find that once energized, there is continuety between R (not Rc) and E / Aux. this should wire to the TT on your boiler center.

A dry contact is one with out power, if you where to measure any terminal to com or ground there would be no voltage present.
If you have a digital VOM, then set it to ohms (lowest scale) and test for continuety between R and Aux and E when the stat calls for these contacts to close.
 
 

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