Floor heat boiler circulating pump

[acbruno]

The floor heat system by far my biggest headache of this car wash. I have a 7 bay self-service wash that has 36 coolant lines (18 out and 18 in) servicing the 7 bays.

When the system starts after being off for a while, the coolant takes a half hour to a hour to circulate consistently. The pressure will build and the flow will start firing the boiler for a couple sends then suddenly the flow drops off and trips the flow sensor turning off the boiler. It then sits for a few minutes with no coolant being circulated (although the pump is always running) then suddenly it builds pressure and flows some coolant for a few seconds then the flow drops off again and it repeats for about 30 minutes to one hour till it finally gets a consistent flow and the system stays running. There is no leaks in the system at all. I used air to pressure test all the lines so I'm thinking I still have large air pockets in the system. My thought is when the system shuts off, the coolant flows to the low points and the pump can't pull it in to prime it when it starts again. I have had to add a few gallons of coolant at times to get the flow started. The expansion tank appears to be ok. There is no leaks in the system (at least all lines pressure test to 15 PSI when not heated). Not sure what's going on here. Anybody heard of this?

 

[robtl]

Your system is what they call "air locked" the best thing to do to stop this and keep this from happening again is to install a "Hoffman 79" automatic air vent at the highest point in the system, just cut in a tee and add a valve and insert the Hoffman.
They can be found at most plumbing supply houses.
when first starting the system back up it will bleed air and spurt a little water and then more air, make sure you are able to keep the system full with an auto prv or manual feed it.

Hope this helps

 

[JIMT]

ACBruno,
It sounds like that your don't have a holding tank that is half full with antifreeze that is above your entire system. Our floor heat system tank is above and open at the top to allow air to escape from the system. With the tank above the pump there is always antifreeze without air available to the pump. If your system is a closed system with an expansion tank the is now way for air to escape.
JIMT

 

[acbruno]

Yeah, my system is closed with an expansion tank. It runs at 10 psi on average. I would have to get a holding tank that will handle that pressure. I would prefer it to be clear so I can monitor the coolant level. Where can I get such a tank?

 

[JIMT]

Yeah, my system is closed with an expansion tank. It runs at 10 psi on average. I would have to get a holding tank that will handle that pressure. I would prefer it to be clear so I can monitor the coolant level. Where can I get such a tank?[/QUOTE

acbruno,
I see no reason to have the system under pressure so any steel container will work.
JIMT

 

[MEP001]

You could use a white poly tank, wouldn't be clear but you can still see a liquid level through it.

 

[Laser Tracer]

I don't know exactly what your set up is. Normaly what you do in a closed situation is install a bladder tank on the feed side and pump your antifreeze into that. My background is hvacr, at one of our washes we staged 2 275,000 B.T.U boilers with techmar controls for in floor heat. We also staged 3 175,000 B.T.U boilers to make hot water with techmar controls. The techmars allow us to rotate the boilers and fire upon demand.