Radiant Floor pressure change

Ed_13

I have a 43 yr old high mass slab with copper tubing. Recently the house was going to be vacant for a week so I shut down the radiant zone and closed the isolation valves to the floor. (floor pressure was 15 PSI, the system pressure) Went I arrived back home the pressure was zero. Not a good thing. Today I wanted to see how fast the floor would lose it's pressure. I closed the valves at 15 psi. After one hour the pressure was 29 PSI. After two hours the pressure was 39 PSI. I reopened the valves and ran the THE WALL for help. Is this just expansion with slight temperature changes??? Still did not solve my leak rate question.

hr

Not good

on either question You will need to isolate individual loops to find the leak. Or leaks. You may be on borrowed time for the age and material in that application!

The pressure kinda indicates an expansion tank problem, ofr a fill valve that is seeping through.

I'm concerned about the 39 psi number, generally boilers have 30 lb relief valves. Your's may be stuck, missing, plugged? This is not good.

Best get a contractor with hydronic experience to check all the above.

I'd recommend shopping for retro fit options. Just in case

hot rod

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Ed_13

Pressure change

This pressure change is happening in the floor loop between isolation valves. The expansion tank and boiler are not even in the picture. The boiler always maintains 15 psi. This loop is shut off on both ends by isolation valves. Losing pressure points to a small leak. I just don't understand any pressure rise when the all the boiler goodies are valved off.....

hr

That's interesting

good chance those old valves are not sealing tightly. Maybe the fill pressure, from the boiler fill valve is squeezing by? The pressure is coming from either expansion or fill pressure, it would seem.

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Dave Yates (PAH)

pressure

changes in isolated loops are likely due to sunlight or surrounding air temperature changes. That's especially applicable where you see an increase in pressure, rather than a steady decline towards zero PSI. We see similar results in tubing during a concrete pour. The most reliable detection will be the addition of a water meter at the hydronic feed line & they're not very expensive.

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hr

Dave has a point

but from 15 to 39 in one hours time, inside a building with the heat off would be a big jump. Especially in a system that recently dropped to zero.

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Jerry Boulanger_2

It only takes a minor

change in fluid volume to get a big change in pressure. It takes 3,000 psi to add 1% more water to a full closed vessel, so the pressure will drop from 3,000 to 0 psi with a 1% loss of fluid.

Ed_13

tewmp change

That's what I believe. The floor was explosed to sunlight in the dining room and it raised the temp. When my system was installed I had a pressure gauge added within the floor loop. Tells me system pressure, (as well as the main gauge), it tells me head pressure when the circulator is on, and it could tell me if I had a leak if I shut the zone down and closed the isolation valves. This is a 1 yr old install. All valves are new. I do not believe any seepage is occurring. It's a temp vrs pressure thing. ..
Fact remains my floor is most likely ready to fail :^(