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Wirsbo radiant heat not triggering pump

2328 Views 7 Replies 3 Participants Last post by  kernbrian
I have a wirsbo radiant floor heat system with 3 zones, one controller, and a Honeywell RA89A switching relay that is used to trigger a grundfos circulating pump. The problem is the thermostats call for heat (yellow led) and then nothing more, at the output side of the control board (wires going to the RA89A) i have both 24v and continuity and I also have continuity at the board on the RA89A, it just does not close the relay to activate the pump. If I put a jumper across those terminals at the control board all fires up and works as it should, the red lights come on and the pump runs. I have already replaced the RA89A thinking it was getting weak or something but that didnt fix it. I dont get it, my fluke tells me that the circuit is closing and the RA89A should therefore be closing and activating the pump but it is like it isnt a good enough connection. I have removed, checked, and re-tightened all wire connections. Any suggestions? I hate to replace the control board when that seems unlikely to solve the problem. It for the record is a A303003 by wirsbo. Anybody have any suggestions? I have attached a picture of the general set up, in the picture I had a jumper installed, without it you would not be seeing the red LEDs on those two zones calling for heat. For the record this has all worked every heating season for 6 years and appeared to fail at this year's start up.


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Could the older valve actuators play into this since they have end switch outputs?
I would say unlikely as all of the valves would have to be bad. Are the valves opening up for the correct zones and end switches working?

If you measure for 24 VAC across TT in the R98A, it should be close to zero when calling for the pump.
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