Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Electronics => Topic started by: ph10west on November 16, 2011, 05:29:21 PM
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I have a Central Boiler. I'm using a second T'stat to control my fan in my HVAC (heatpump), but the primary t'stat has the compressor signal wire "Y" connected to the fan control wire "G". Is there a t'stat that I can use that does not connect the Y and G wires?
If the fan switch is "ON" on (the heatpump t'stat) the wires are not connected. So I have considered turning the fan switch to the on position on the HVAC t'stat and using the second t'stat to break the fan wire connection so the compressor would not come on unless the inside temp went too low. When cooling I would have to switch the fan to auto and bypass the second t'stat. Since I live in the South I'd like to be able is switch between cooling and heating easily. Less steps is better for the wife and kids. Anybody figured this out?
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New stat should be jumped over from the red r to your new stat, from the w setting on your new stat run a jumper to the g green post. New stat will work the fan only and old one will work like it always has.
If that don't work u may have to use a relay as well to stop it from back feeding and running the outside unit
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New stat should be jumped over from the red r to your new stat, from the w setting on your new stat run a jumper to the g green post. New stat will work the fan only and old one will work like it always has.
If that don't work u may have to use a relay as well to stop it from back feeding and running the outside unit
You have to remove the wire from the G on the original thermostat and splice it to the W wire on the new thermostat. Otherwise it runs the compressor.
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That's what the relay would be for, I never unhook any wires really.
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Thanks for the replys.
I think I wired it like you guys said. I ran the r old to r new and the w new back to g old. However since the old has y and g common the compressor runs. Soooo... Tell me how to wire in the relay. Pleeeease
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If you just take both wires off the G and splice them together it will work.
If you want to do the relay instead you will have to wait for Scott to reply. I don't do it that way and not sure how he wires it.
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Yoder eating could tell us all about this, he's who told me about the relays
Rsi, what do u do when you run into a variable speed fan?
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Yoder eating could tell us all about this, he's who told me about the relays
Rsi, what do u do when you run into a variable speed fan?
Don't they just have a fan switch on the thermostat the same as a regular? If they don't then I haven't run into one yet.
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I see how taking both the wires off g on the old t'stat would work fine for heating. Fan gets its signal and you are NOT sending the signal to the old t'stat so the is no feedback. But what happens when you call for cooling? I think you would have to put the g wire back on the old t'stat.
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The G has nothing to do with cooling. It is the fan only signal.
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I will try and explain how to wire it with a relay. Start with the new and old Tstats r to r and c to c, this will power the thermostat. Now, you need a extra wire in the existing thermostat wire. Use the extra wire to run from the W on the new tstat down to the relay in the blower unit. I use a white-rogers 90-293 5 pole relay. On the relay #3 pole is wired to c from unit. #1 and #2 on relay gets wired to the tstat wire from the W on new tstat. You split the tstat wire going from the g on old tstat to g on unit (normally green wire). The wire going to unit goes on #4 and the wire going to g on old tstat goes on #5. #5 and #4 is normally closed so you can use old tstat whenever you are not using the outdoor furnace. When the new Tstat activates the w it turns on the relay by powering #1 and which closes between #2 and #4 therfor opening #4 and #5. This turns on the fan but does not allow power to flow back to the g on the old tstat.
I'm sure this makes no sense but at least I tried. :) :D
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RSI, you say g has nothing to do with cooling. Then when cooling is called for the fan gets its signal from the the cooling wire? I've never messed with a t'stat much. So I don't know how all the signals work inside the HVAC unit. I realize the signals are just 24v circuit getting completed.
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The thermostat doesn't control the fan in either heat or cooling mode. It is controlled from the furnace itself. All the G wire is for is the manual fan switch on the thermostat.
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OK thanks! :thumbup: Now if I can get my bypass valve wired to bypass the heat exchanger. I have all the bugs worked out. I wanted it to open when I switch the t'stat to cooling. Any ideas on how to do that.
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What type valve do you have? Does it have a motor that just hits the end and stalls or does it drive both ways?
If it is using power all the while it is bypassing you probably don't want it running all summer.
You should be able to use a relay to do what you want. Just connect the coil between the C and Y wires. I never tried it but if the coil is enough to make the compressor run a solid state relay would probably work.
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I have a Taco 560 three way bypass valve. If I throw the manual lever it will open the valve partially to the heat exchanger. But does not open all the way and the flow to the waterheater is easier since the heatexchanger is overhead. I tried to steal power from my radiant floor pump but the valve stayed all the way closed. I'm going to get a transformer and see if that will work.
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I have a Taco 560 three way bypass valve. If I throw the manual lever it will open the valve partially to the heat exchanger. But does not open all the way and the flow to the waterheater is easier since the heatexchanger is overhead. I tried to steal power from my radiant floor pump but the valve stayed all the way closed. I'm going to get a transformer and see if that will work.
I hope you didn't connect it to 120v. If you did, it should have smoked pretty good.
You need 24 volts AC to run it.
Do you want it to open when the blower runs?
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No, Not 120V. I metered the termnal block on the zone pump and found ~28v. Thought that would be close enough. Yes I want it to open when the fan runs.
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I am not sure if a relay coil between the C and G wires would be enough to turn the fan on so this is how I would do it to make sure it doesn't.
Get a 2 pole relay with 24v coil. Connect one side of the coil to the R terminal in the furnace. Cut the G wire at the furnace and connect the side that is going to the thermostat to the other side of the coil. Connect the other side of the cut wire to the normally open contact of one of the poles (if you have a DPDT relay)
Then run a wire from the R to the terminal in the furnace to the common contact for that pole.
Then get a 24v transformer and connect one side of the 24v to the zone valve and the other wire to the common of other pole of the relay. Connect one of the wires of the zone valve to the normally open and the other wire to the other wire on the transformer. You will also have to connect the primary of the transformer to 120v AC.
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Follow-up... I ended up using Relays and switches. I have a light switch to turn on/off constant power to the 3-way valve so I can have a spring/fall or day mode. In winter or night mode I have constant flow to the ductwork heat-exchanger. There are two sets of wires coming from the transformer to the valve(one is the thru the manual switch, the other goes thru the relay. In the spring/fall mode my first relay allows (With the switch off) the hot water only to flow the heat-exchanger in my ductwork when the relay (Normally closed) is tripped by the 2ndary t'stat. This will keep from heating the air when I am trying to cool and keep the convective heat from coming from the ducts with the heat off. I got to take the panel off my air-handler and see exactly what my heating and air guy did with the other relay to break the signal that feeds back thru the primary t'stat and allow the heatpump and a/c to work normally.