Thrush Flow Control Mystery

FrankGarro_2

Help! I'm baffled as to why I cannot get flow through the below grade basement circuit on this 3 zone, 3 circ system. I replaced the failed circ and added purge valves to the basement loop but still no flow through the circuit.

When I only call for heat in the basement the circ comes on but doesn't move water through the loop but rather through the air bubble line that goes up to the tank. Those air bubble lines are tee'd together before they connect to the tank up above.

I reviewed the museum pdf file, should I assume the disc is simply stuck in the closed postion?

Jamie Hall

air bubble lines? Eh? But if you have pipes which make a shorter path for the water, and there are no valves on them to block the flow, that's where the water will go.

FrankGarro_2

...the pipe that goes to the compression tank.

EdTheHeaterMan

Not every Thrush flow valve needs to be connected to the expansion tank. Just one of them. And that is not always the best location for the expansion tank.

So think like water. it will take the path of least resistance. if the path that connects the two thrush flow valves together is less restrictive than the path that requires opening the weighted valve and going thru all those radiators, then that is where the water will go.

What is the chance that the flow valve is stuck closed? It might be. The only way to tell is to open it up and look. Is there a handle or lever on the other side that allows you to open the valve manually? That may help.

Here is the instructions that came with the valve!
https://heatinghelp.com/assets/documents/221.pdf

EBEBRATT-Ed

@FrankGarrow_2

Almost all flow control valves have a way of manually opening them. Sometimes it is a lever on the side of the valve.

FrankGarro_2

I did move the lever and it didn't seem to change at all. It moved freely, maybe too freely as if it was not connected to the disc perhaps. I thought about plugging the line to the tank to prevent the short cycling of the water. I think that will be my next move. Thanks @EdTheHeaterMan

EdTheHeaterMan

Thrush Flow Valves were popular long before Copper Tube with Fin Baseboard radiators were popular. So the question in my mind is, What kind of radiators are connected to the basement zone? Purge station works best on copper tube baseboard for removing air. Not so much on cast iron radiation or multi channel convectors.

WMno57

Frank, could you give us some more details. Did all zones work before? Which zones work now?

My Thrush.

FrankGarro_2

All the zones are 3/4 baseboard. The basement zone hasn't worked for a couple of years. The circ had failed and I hoped replacing the circ would fix the problem. @WMno57, your thrush looks quite nice.

WMno57

The lever on my Thrush is seized in the NORMAL position. The other position (OPEN) is to allow gravity flow in case of circulator failure. When my single circulator is not running the pipe above my Thrush is not warm, but my boiler is always warm (because I'm doing warm start).
So based on the difference in temperature when feeling pipes, I assume my disc is opening and closing normally. The line to the compression tank on mine sometimes gets lukewarm, but not hot.
I only have one zone, so I'm not familiar with your two lines to the tank setup. I'm not pumping away, so I am pushing water through the Thursh. You appear to be pumping away on the basement zone, so you are pulling water through the Thrush
I'm not sure what your next step should be:
Cap off the air line from the basement zone Thrush
or
Take the Thrush apart and verify the disc is not sized