flow checks leaking through

hot_rod

you may need check protection on both the supply and return side. This is especially true with S&R piping that rises vertically from the boiler piping or in a primary secondary layout.

It i very possible for two way flow in a pipe (thermal migration), as warm water like warm air rises up the pipe and cooler water drops.

Try a circ with check protection built in and a spring check on the other, Supply? pipe.

Some installers use a check pump with a zone valve on the other side, like indirect WH piping.

There are many spring checks, built for hydronic application, with low, generally 1/2 psi pop pressure. Watts, Jomar, Conbraco are a few brands I have used.

hr

Rod Bixler

flow checks

We are fighting a hot water system with four zones. Each zone has its own circulator located on the return. Over the past two years we have changed the Taco flow checks twice. They are still leaking through. We used the cast iron angle pattern the last time we changed them on one zone. That zone still leaks through just like the sweat checks. We changed the bladder type expansion tank because I thought it was border line in size. We tore down the checks and made sure there was no obstruction. We also cleaned the seats and weights at that time. Any suggestions???

Joe Mattiello

Is this a supply/return manifold piping, or primary secondary piping? I have to agree with Hot Rod; the pressure drop across the valve must be higher then the pressure required, which is forcing open the check. Some other possibilities; do all the circulators have the same operating characteristics? Is there a system pump energized off the C1, C2 terminals?

Big Ed_4

Is the problem zone

..... A parrell system ? What size supply and what size flow valve used ? What is the location of flow valves and circlators

Jason_22

It might sound obvious but we had a problem like this and it was a bad high limit. The boiler temp was running way over which was forcing water through the flowchecks.

Indysteamer

I have run into this problem several times when the pumps are on the return. No mater what types of checks, flow controls ect. were used the problem would continue. What I have found is when a pump on the RETURN turns on in some cases it pushes water through the boiler and then into the other zones that aren't calling for heat. This may be what is happening to you??? The only way I have been able to fix this is to move the circs so they are pumping away.

Rod Bixler

answers to questions

Thanks for the responses. The boiler temp is not overriding. It stays approx. 180.But does not maintain temp 24/7. The four zones are all 3/4" and are loops. The supply manifold is about 30" above the top of boiler and the the return header is located at the bottom of the boiler. It is not a primary, secondary system. This problem has developed in the last two years. The system operated fine for, I'm guessing, 25 years.

Unknown

I had the same probs,

with B&G flow controls. Pumps on the boiler return, old gravity headers.
I just changed the pumps to small Taco`s with the built-in checks & left the flow controls, problem vanished.

The heat will still migrate through them all, regardless what circ is running, the pump checks solved-it. Kinda double resistance.

Dave

Big Ed_4

Flow Valve

I am assuming they are all 3/4" Flow valves? Either bump it up to a 1" or install a second flow valve on the return .

The 3/4" valve are know to have problems if the radiation is a rise from the flow valve.. The weight or the surface is too small...

You cleaned the seat and weights stem ..... and even changed out the valve . Some times you just need two flow valves.. I seen it with a long run or rise from the boiler to the flow valve . Or with a large supply and rise to the radiation .. Once the water starts moving you need enough force to counter the momentum ....


I don't know how a expantion tank could cause a by pass ?

billtwocase

Flow check

Is there an hivent, auto bleeder somewhere in that zone? Exspansion tank not on that zone piping? Switching relay welding? Any work been done to the system before this was an issue? How is the circulator manifold set up on the return? Pump away circs will not solve this. Does this zone disappear into a crawl space or cement floor? a leak some where can also cause this besides pressure/temp. Take some pics for us. peace