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Author Topic: Basic Thermostat Relay and Fan Wiring?  (Read 3587 times)

rhugg

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Basic Thermostat Relay and Fan Wiring?
« on: August 21, 2011, 06:40:18 PM »

I have a two zone basic heatpump system (two heatpumps and the downstairs at least has ane emergency strip.  I will keep that programable thermostat as is to run the heatpump and add a OWB Thermostat to turn on the boiler circulator and the houses air handler.  I'm not sure what I'll do on the upstairs system yet.  So here goes.  I can pick up the red-black-green 24v wires at the air handler and run them to the new basic digital thermostat.  What wires from the thermostat go to the relay (White Rogers Type 91)?  I assume that one or two wires also return to the air handler relay to drive the fan, do I just run the appropriate color wire from the Thermostat to both the 110 relay for the OWB and the 240 relay for the air handler.

Will the same 110 line (20 A) be able to run both OWB boiler circulators (one for each heatpump)?  Guess I need to check what amps they pull.

I'm sure this is easy for a pro but I'll need to go slow.   
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gmviso

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Re: Basic Thermostat Relay and Fan Wiring?
« Reply #1 on: September 04, 2011, 07:15:13 PM »

As to whether a single 110V 20A circuit will support both pumps, it depends on what pumps you are using, but I would think so.

What are the models and/or Horsepower of the motors on the pumps?
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RSI

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Re: Basic Thermostat Relay and Fan Wiring?
« Reply #2 on: September 04, 2011, 09:35:08 PM »

If you are anywhere close to the capacity of the relay you will have a big power bill. Lol
Depending on what pumps you are using, they will most likely be between .5 and 2 amps each.

If you are using the existing fan and you have a fan switch on your existing thermostat, I highly recommend disconnecting the fan switch and using that wire to the new thermostat. If you leave the fan switch functional and someone switches it on you will get a very warm house. (unless you use a zone valve to divert the water past the heat exchanger)
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RSI

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Re: Basic Thermostat Relay and Fan Wiring?
« Reply #3 on: September 04, 2011, 09:36:41 PM »

I guess it is late, it didn't sink in till I posted you are shutting off the pump too. Ignore the warm house comment.   lol
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Ridgekid

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Re: Basic Thermostat Relay and Fan Wiring?
« Reply #4 on: September 04, 2011, 09:52:59 PM »

First, why does anyone want to shut off the OWB pumps when the OWB is in operation? If you have a DHWX wouldn't you want the pump running consistantly?

Why do you need a seperate thermostat? I have a heatpump with a mercury thermostat and they wired a aquastat to control my heating system. Here's how: (maybe it will give you another idea)

If my thermostat calls for heat, and the aquastat is below 160F, it turns on my heatpump. If it's above 160F, it only turns on my furnace fan. BUT- if I raise the temp on the thermostat more than 3F, it kicks on my heating strips (but not my heatpump).

Unfortunately I'm sure how this is wired in, since the dealer did part of the installation.

BTW: my aquastat is surface mount, not thermowell.

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willieG

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Re: Basic Thermostat Relay and Fan Wiring?
« Reply #5 on: September 04, 2011, 10:06:08 PM »

im not sure if your heat pump is similar to mine but here goes...my in ground water furnace (heat pump) has a low speed fan that runs 24/7 and if the thermostat for the heat pump calls for heat and the compressor kicks in then the fan speeds up. i left all this asit was and just added another thermostat that operates a zone valve that controls the flow of water to the heat exchanger in the plenum. with the OWB feeding hot water at a non stop rate  the house is heated easily on teh low speed fan. when the house gets to the temp i have set then the zone valve closes and shuts the water off to the rad. This way if the wood fire went out or something happened that caused the OWB to stop functioning then the heat pump would kick in as normal. This also keeps the two heating systems virtually seperate from each other, there is no intertwining electrical wires or anything. I like simple
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RSI

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Re: Basic Thermostat Relay and Fan Wiring?
« Reply #6 on: September 04, 2011, 10:51:34 PM »

That makes sense if the fan runs all the time.
You can do the same thing with a pump with a secondary loop instead of a zone valve. Which works better just depends on the system.
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willieG

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Re: Basic Thermostat Relay and Fan Wiring?
« Reply #7 on: September 05, 2011, 08:08:55 PM »

i have one taco 0011 pumping water to a header that then branches out to the domestic hot water exchanger, the rad in the heat duct, a rad in my fireplace (no more wood in the house) a rad in my basement and pool room and also to my floor heat (although the floor heat has a circulating pump on the loop) the domestic coil has no zone valve on it, it runs 24/7 with the taco pump
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rhugg

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Re: Basic Thermostat Relay and Fan Wiring?
« Reply #8 on: September 07, 2011, 06:01:08 PM »

OK, here's what I did:
I left the thermostat alone that controls the heat pump and emergency strip heat.  I'll set it lower than the OWB Thermostat so it only comes on 'in an emergency'.

I had a simple Honeywell Digital Thermostat (TH5220D) so I used it to turn onn the OWB pump and air handler.  I picked up the red wire from the 24v transformer (same wire that runs to old thermostat and ran it to 'R' terminal on the new.  The blue wire (return to 24v transformer) was wired to the 'C' terminal on the thermostat.  A wire went from 'W' on the thermostat to the 24v side of the relay and then a wire went from the other leg of the 24 v relay to the blue wire (return) at  the 24v transformer.  So 'W' from the thermostat control the OWB Circulating pump via the relay.  A wire from 'G' at the thermostat goes to the existing air handler relay (same connection as 'G' from the old thermostat).

I used a RoHS Type 91 relay, when it is energized with 24v terminal 1 and 3 are closed and 4 and 6 are closed.  I used 1 and 3 to switch 110 power to the OWB Circulator.  The 24V terminals are at the bottom and unmarked on my relay.

It works, the thermostat asks for heat and switches both the Circulating pump and the air handler on.

I see no reason to run the circulator constantly as I use a DHW coil in the boiler.
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willieG

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Re: Basic Thermostat Relay and Fan Wiring?
« Reply #9 on: September 07, 2011, 07:13:20 PM »

rhugg, you may elect to run as you are now and turn your pump off an on as you need heat along withyour blower and i can not say for sure if that is the best or the worst thing to do. I have been told what wears a pump out is not the running of it  but the stops and starts. I have only been told this by a couple of plumbing guys. Are the telling me the truth as they know it or only as they believe i also am not sure. i have often thought of writing taco and asking  but i do know i turn my pump on in about October and shut it off around June i have the same taco 0011 pump i started with and this coming winter will be year 12. i have replaced 2 blowers on the furnace that shut off and on when the furnace calls for air but i am still on water pump number 1 (and hoping for it to last this winter as well)
I am not sure what luck others have had that have  been using their OWB for a period of this long or longer have had, perhap some will tell us how they run their pump and how long they have lasted?
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rhugg

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Re: Basic Thermostat Relay and Fan Wiring?
« Reply #10 on: September 08, 2011, 09:25:23 AM »

I Hear ya and I see both sides of the argument.  Maybe the electric savings and lost heat savings will make up for the lost life on the pump ... if any.  Hydronic systems on old boilers and radiant baseboard heat only pumped when the thermostat asked and I never replaced that pump. 
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willieG

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Re: Basic Thermostat Relay and Fan Wiring?
« Reply #11 on: September 08, 2011, 05:24:04 PM »

rhugg, i have posted a question of om/off or run steady to taco after posting here last time. their answer is in  post in general forum (this question was only posted to them about their 00 pump line
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RSI

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Re: Basic Thermostat Relay and Fan Wiring?
« Reply #12 on: September 08, 2011, 05:51:40 PM »

I wouldn't worry about the pump life, I would be more worried about the stove boiling over. Some may not matter but I have seen some (especially when it is warmer out) that do if the pump is shut off.
It will also probably give you more shorter burn cycles.
The reason is that all the heat goes to the top. When the pump runs continuous the water in the tank keeps mixed and is the same or close from top to bottom.
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Ridgekid

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Re: Basic Thermostat Relay and Fan Wiring?
« Reply #13 on: September 08, 2011, 06:12:06 PM »

Good point, just because you shut off the pump, you didn't kill the fire!
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willieG

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Re: Basic Thermostat Relay and Fan Wiring?
« Reply #14 on: September 08, 2011, 09:24:24 PM »

i do agree that running yoru pump 24/7 is best but....if running your pump prevents your OWB from boiling over?...i guess that would mean you have sufficient heat loss in your  system to overcome the effect of the "afterburn" of the gas and air mixture still in your firebox after the draft is closed?  i would think if you depend on this then perhaps you need to turn down your aquastat to allow for the extra few degrees that would likley occur in the temp of your water while these gasses burn off and then , find out where all this heat loss is and try and prevent that as well.
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