Flow Switch (Boiler) Not Working

xrabbi

Active member
Jun 22, 2020
40
NYC
As seen in the pictures, our setup includes a 5-ft straight vertical run into the heat exchanger, with a flow switch and acquastat inline. Then flow switch and acquastat are wired together so that either can trip the boiler (e.g., if pump is off and there's no flow, zone should not call for heat). All equipment is new but the flow switch does not work, the zone stays on even when pump is off. Any immediately obvious reason as to why? Is it just wired incorrectly with acquastat?Thanks.

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20200916_224937.jpg
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
20,477
Northern NJ
Your picture does not show how the flow switch is wired. The white wire just disappears into the Aquastat box. Open up the Aquastat box and show us how the wires are connected.

Then flow switch and acquastat are wired together so that either can trip the boiler (e.g., if pump is off and there's no flow, zone should not call for heat). All equipment is new but the flow switch does not work, the zone stays on even when pump is off. Any immediately obvious reason as to why? Is it just wired incorrectly with acquastat?
I would think you want the heat to the pool only when the pool pump is on (flow switch) AND the Aquastat calls for heat. Not if either/or is closed.

For AND you want the two switches wired in series. For OR you want the two switches wired in parallel.

I suspect the switches are wired in parellel.

Happy New Year!
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
7,215
Central California
If not the wiring...

I don't know much about flow switches, but I think some are just simple levers (paddles). Like the backwards check valve you fixed, could the flow switch be facing the wrong way, or at least not be aligned correctly? It might be closing because of the pressure, but staying closed because of gravity? Or it could be stuck/defective.

Oh, wait, I see the tiny little arrows. Pull it out and test it with a meter, to see if the continuity works correctly as you move the lever.

The blue wire nut in the photo Allen asked for is obscuring a bit what he wanted to see, but it looks to be wired in series.
 

xrabbi

Active member
Jun 22, 2020
40
NYC
Ugh, so I unscrewed the flow switch and this is what came out:
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It's missing the little black thing in the middle of the paddle that makes the connection. I'm pretty sure it fell off when I took the switch out of the tee because now the circuit is open and will not activate the boiler. The little black thing is now somewhere inside the pipes ... Guess I just need to buy a new flow switch?
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
7,215
Central California
Yes, new flow switch.

But you have to find/flush the missing chunk, especially if it's metal. You might luck out and it's caught in the three-way just below it. If not, you need to undo the unions of the SWG and pull that off. That's where you wouldn't want any chunk of metal landing, and shorting across the plates in the SWG cell. No bueno! If there's an easy way to disconnect the SWG wiring, or turn off it's breaker, that might be prudent, until you sort this out.

With the pool's isolation valves closed, you could check the three-way. If not there, then put the valve back together and use it to isolate the heater. Then pull the SWG. Open just the suction-side isolation valve and with any luck the pool's pressure will flush the piece out where the SWG would be. If that doesn't work, you might have to goose the flow with the pump.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
20,477
Northern NJ
If it still does not work right after you replace the flow switch then check your wire connections. This pic shows a sloppy connection...

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