24v system help

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swyman
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Post by swyman » Fri. Jan. 05, 2018 9:27 am

My system is setup and running good but I would like to shut off one circulator while there no call for heat as it has a Delta T of 6-8* just circulating. I am using a Taco zone controller with this circulator which has it's own 24v power supply so what I would like to do is make that circuit with my furnace control board. Problem is when I try to hook it up to my furnace control it blows the 5a fuse on my furnace control board? The furnace transformer is a 40va so I would think that would handle it? I tested the relay with the Taco circuit to test voltage drop... I read 28-30v with no load and when I energize the relay the voltage drops to 9v. Is it just to much of a current draw to energize that relay? If so, do they make a smaller relay that takes less amperes to energize? Or is there a different/better way?

 
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nepacoal
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Post by nepacoal » Fri. Jan. 05, 2018 2:45 pm

Does your furnace control board have an end switch? If so, it could just go to the thermostat inputs on the taco zone controller. Problem would be solved

 
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swyman
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Post by swyman » Fri. Jan. 05, 2018 3:08 pm

nepacoal wrote:
Fri. Jan. 05, 2018 2:45 pm
Does your furnace control board have an end switch? If so, it could just go to the thermostat inputs on the taco zone controller. Problem would be solved
Not sure, I will have to check the wiring diagram. Does that shut off the 24v on the board so it just uses the zone controller?


 
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nepacoal
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Post by nepacoal » Fri. Jan. 05, 2018 3:47 pm

End switches are typically just passive switches that close on a call for heat from the thermostat on the furnace. Also check to see if you have any connections labeled N/O. It's also possible to use those to mimic thermostat inputs to the taco. I did something similar in my old SF-260 boiler with Johnson controls controlling my loop pump on my taco zvc403.

 
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nepacoal
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Post by nepacoal » Fri. Jan. 05, 2018 6:15 pm

If you don't have an end switch and still want to control it with a 24vac output from the furnace board, search Google for a 24v relay in a box. The N/O output could be used as the thermostat input on the taco

 
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Post by Rob R. » Fri. Jan. 05, 2018 7:06 pm

You can't connect the two 24v systems like you attempted, they need to be isolated by a relay.

A simple 24v RIB would work, or you could use a 120v relay and turn it into the blower circuit. Lots of options.


 
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swyman
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Post by swyman » Sat. Jan. 06, 2018 7:40 am

Rob R. wrote:
Fri. Jan. 05, 2018 7:06 pm
You can't connect the two 24v systems like you attempted, they need to be isolated by a relay.

A simple 24v RIB would work, or you could use a 120v relay and turn it into the blower circuit. Lots of options.
I have one setup like that now that I use in emergency situations. My buddy stopping by tonight to try and figure out what I'm doing wrong...

 
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Post by titleist1 » Sat. Jan. 06, 2018 7:56 am

If I understand your description correctly I agree with Rob to get an interposing relay to keep the furnace and zone controller circuits separate. The coil side of the relay is wired to the furnace board so it controls the latching side of the relay which is wired to the 24V supply from the zone controller to power the circulator.

 
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swyman
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Post by swyman » Mon. Jan. 08, 2018 7:26 am

titleist1 wrote:
Sat. Jan. 06, 2018 7:56 am
If I understand your description correctly I agree with Rob to get an interposing relay to keep the furnace and zone controller circuits separate. The coil side of the relay is wired to the furnace board so it controls the latching side of the relay which is wired to the 24V supply from the zone controller to power the circulator.
Done, done, and DONE! Got this done and is working perfect. Thank you Hotblast for keeping me on the right track for many days!

 
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Post by hotblast1357 » Mon. Jan. 08, 2018 7:49 am

Anytime! Glad to help.

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