Trying to connect the thermostat wires coming from the first and second floors of the house, going to my propane boiler. Both thermostats are twist tied together to close the relay for the propane furnace. I tried tapping on to these wires and send them to a taco relay panel. It worked great at turning on the pump that supplies water from my pressurized system to the manifold but when no more heat was being called for, the pump continued to run. Checked resistance of the thermostat wires and it's reading 8.6 ohms. Where do I go from here? When I connect back up with the resistance, the pump doesn't turn back on but makes the transformer hum a little more.
ohm resistance
- Thread starter ulooknatme
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Is the Taco relay panel a ready made unit or a panel you made yourself. If it's ready made, it sounds like you have 2 transformers involved in the total hookup you made.......one that was working the propane boiler and one probably built into the taco relay panel. Is this the case?
I have a hunch that's a good guess. You're probably going to have to install an isolation relay in the thermostat circuit to keep the two transformers from fighting with each other.
The Taco panel is from Taco. It has 6 relays but only one was in use. All it did was kick on the pump for dhw. Both air handlers came with there own cir pumps installed. The air handler that I'm messing with does have a transformer as does the Taco panel and the boiler too but I had already disconnected that one before all this began.
Now, what is a separation relay you speak of?
Now, what is a separation relay you speak of?
You can solve the problem with or without a third relay (I attached a crude simple wiring diagram that will work). If you prefer not to use a third, you must make sure that you only have one tranformer in the TT circuit. You connect the two relays in parallel, and these leads are connected ........one to the TT and the other to the transformer. (the other lead on the transformer is connected to the remaining lead on the TT.) So the TT and the transformer are actually in series. You probably can solve this multi transformer problem if you disconnect the Taco relay bank (it is probably connected to household juice somewhere) . That will take the Taco transformer out of the mix.
If you prefer to use a third relay, you could use one of those unused ones on the Taco strip.
If you prefer to use a third relay, you could use one of those unused ones on the Taco strip.
Attachments
You could also use your unused Taco bank relays to solve the problem:
Hook the TT leads directly to two unused relays (in parallel) (to the TT or control screws)
From one of these relays connect the relay activated wires(screws) to the pump relay where you had the TT wires formerly attached. From the other relay connect the activated wires(screws) to the Propane boiler relay that the TT was originally attached to. This will prevent any cross connection through transformer or relay coil, which I suspect was your original problem.
In this case, do not disconnect any transformers, except there should be NO transformer in the TT line, just TT directly to the 2 taco relays.
If you want another of my art masterpiece circuits, let me know. Sometimes a diagram is easier.
Hook the TT leads directly to two unused relays (in parallel) (to the TT or control screws)
From one of these relays connect the relay activated wires(screws) to the pump relay where you had the TT wires formerly attached. From the other relay connect the activated wires(screws) to the Propane boiler relay that the TT was originally attached to. This will prevent any cross connection through transformer or relay coil, which I suspect was your original problem.
In this case, do not disconnect any transformers, except there should be NO transformer in the TT line, just TT directly to the 2 taco relays.
If you want another of my art masterpiece circuits, let me know. Sometimes a diagram is easier.
You have a third choice:
Connect your TT wires directly to the TTscrews on the Taco pump relay AND the TT(control) screws of one of the unused relays (this is your "separation" or "isolation" relay)
Connect the unused relay's activated wires(screws) to the propane boiler's relay to the screws where you originally had the TT wires.
This will work just as well. It's a matter of what is easier or what you understand better.
Note: The TT leads must not go through any transformer, just 2 wires from TT to Taco relays.
Connect your TT wires directly to the TTscrews on the Taco pump relay AND the TT(control) screws of one of the unused relays (this is your "separation" or "isolation" relay)
Connect the unused relay's activated wires(screws) to the propane boiler's relay to the screws where you originally had the TT wires.
This will work just as well. It's a matter of what is easier or what you understand better.
Note: The TT leads must not go through any transformer, just 2 wires from TT to Taco relays.
I went back to the boiler and traced the red and white wires back to the air handler. (there were two sets of red and white tied together at the boiler so I took it for granted that they were the thermostat wires from upper and lower air handlers) Low and behold one set came from the taco relay box marked X X in the lower left corner.(isolated end switch) So what I was doing was looping it from XX right up to the TT above it! I ohm'ed the XX and sure enough, 8.7 ohms. NOW, which wires are from the TT in the thermostats? They are set up for emerg heat, heat pump, and a/c. Propane boiler is the emerg heat setting. Are there standard colors for each? I pulled out the old honeywell and thought I might be able to decipher but nothing says which is which. There was 6 different colored wires coming out. Blue/C, red/R, white/W2, which is also jumped to E, yellow/Y1 which is also jumped with W1, orange/O/B and green/G. Thanks
I'm just a hobbyist. Maybe a pro will see this and be able to tell you. TT wires are usually red and white for heat side. You might look up your TT online and find a manual that will tell all. You could also take the front off the TT; that may reveal what is what. Actually you did have the two wires that were connected to the propane. Can't you work from those, since you know they did turn everything on?
Here's a way to test for what wires come from the heat side of the TT.
Pick the 2 you think are correct (I'd go with red and white) and disconnet them. (I assume you are using a VOM to check resistance)
Connect the VOM to these two wires FIRST to see if any voltage is present (Use the AC scale that will measure 24v).
Have a helper turn your TT well above rm. temp to call for heat. If no voltage is present, switch over to the ohmmeter, if it reads 0, have the helper lower the TT to way below rm temp.. If it reads infinity(incomplete circuit), you have the correct wires, if not, start the whole proc over with another set of wires.
When the helper raises and lowers the TT your ohmmeter should swing from 0 to inf.
Pick the 2 you think are correct (I'd go with red and white) and disconnet them. (I assume you are using a VOM to check resistance)
Connect the VOM to these two wires FIRST to see if any voltage is present (Use the AC scale that will measure 24v).
Have a helper turn your TT well above rm. temp to call for heat. If no voltage is present, switch over to the ohmmeter, if it reads 0, have the helper lower the TT to way below rm temp.. If it reads infinity(incomplete circuit), you have the correct wires, if not, start the whole proc over with another set of wires.
When the helper raises and lowers the TT your ohmmeter should swing from 0 to inf.
Thats a great idea.
The only thing that gets me is why is there resistance in the wires going to the propane boiler? I know the old fashioned thermostats of 30 years ago were just mercury bulbs that completed the circuit. And the aquastats I installed to the Tarm are not powered. I'm just trying to make sense of the whole thing. I can't figure out where the 24v transformers come in except to power the relay.
The only thing that gets me is why is there resistance in the wires going to the propane boiler? I know the old fashioned thermostats of 30 years ago were just mercury bulbs that completed the circuit. And the aquastats I installed to the Tarm are not powered. I'm just trying to make sense of the whole thing. I can't figure out where the 24v transformers come in except to power the relay.
powering the relay (s) could be the only thing the 24v is used for. Could the resistance your reading across the input to the boiler be the relay its wired into on the control circuit for the pump ? I know in some equipment I have worked on there is protection inline to prevent damage to the internal circuit board.
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