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Radiant "Zone" Not heating


We have a house built in the 1950's which has hydronic radiant heat in the ceiling. Since the start of heating season we have not had heat in one half of the house. I do not know tons about hydronic heating, but I do have a basic understanding of our system; I like to think.

We have a single story home, the hot water runs up into the ceiling upstairs. The pressure gauge is showing about 12-15 psi. There are not "independent" zones in the system, there is one feed pipe running from the boiler, which has two pipes that run from it, up to the attic. In the attic, there is what appears to be possibly a purge valve at the highest point (picture 4), with a small pipe that runs back down to the basement. One has another valve on it (picture 5) in the basement, the other is just open in the basement. In the attic, each of the pipes that ran up from the basement splits into 5-6 smaller pipes (11 total) that are embedded into the plaster. They then loop through the ceiling, and return to the basement, and feed into one common return pipe to the boiler(picture 6)(only the return lines nearest the boiler are pictured).

Both pipes running to the attic get hot to the touch, both in the basement, but also in the attic, and the ones that run back down nearest to the boiler are also warm. The ones about 15 feet from the boiler are cool returning to the basement, and the ceiling in three rooms in the house are cool. I assume there is air trapped in the system, in the "second zone" but do not understand how to bleed it. Everything I have seen until now talks about isolating the zone that needs to be bled, or shows how to bleed systems that don't visually seem to have any similarities with ours.

Thank You in advance everyone for all your help!


  • hot_rod
    hot_rod Member Posts: 22,118
    What brand and model boiler? Most high efficiency boilers prefer a primary secondary piping, the manual shows acceptable piping options.

    That ceiling compression tank will limit air removal, an air purger and newer style expansion tank would have been a nice upgrade.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Gordy
    Gordy Member Posts: 9,546
    edited November 2018
    I had ceiling radiant. Ranch style House was built in 52.

    Is there pet cocks On each individual pipe coming off that return manifold? The screws in the manifold adjust flow to each loop. However they appear to have been leaking, and were probably set. So I wouldn’t mess with them.

    The valve in the attic with 3/8” copper coming off of it is in the off position. The other valve is a bleeder.

    With mine there were not any bleeders in the attic, only petcock bleeders at the return manifolds in the basement.

    I’m sure if it worked before it’s air bound. It happens . You’ll have to bleed off that bleeder valve with the circulator off. Until you get no air while keeping pressure at about 20psi. Until you get water. Then drop pressure to 12-15 psi. Run system for a few heat cycles, and repeat.

    A handy device is a hand held infra red temperature gun. You can shoot the ceiling to see if the pipes are getting warm all the way around.
  • Gordy
    Gordy Member Posts: 9,546
    edited November 2018
    So looking at this setup. I’m thinking the 3/8” copper coming off the closed valve in the attic goes to the basement where the other bleeder valve is? Sound right?

    Does it go into the plaster ceiling, or into the top plate of a partition wall?

    So if my thinking is correct, the valve in the attic is redundant to the one where you bleed in the basement?

    If true then while the valve in the basement is still off, open the attic valve then bleed from the one in the basement. Once done close both valves.
  • Gordy
    Gordy Member Posts: 9,546
    edited November 2018
    As @hot rod_7 pointed out your ceiling radiant has high headloss due to the small piping. That boiler shouldn’t be piped direct as is, and should be primary secondary piped. Also air in the system will be an on going issue with out the circulator pumping away from the expansion tank, and ditching the compression tank for a diaphragm expansion tank with an air removal device.

    At the very least instal an airtrol tank fitting on the present compression tank. The piping going up to the compression tank doesn’t even really allow a direct path for air to make its way back into the tank. It gets sent back out into the system to end up in the ceiling, and now you have issues.

    With a Cast Iron boiler that setup works okay because there is a baffle in the boiler section that traps air, and sends it up to the compression tank. If that piping is piped to the tank properly.

    With the new boiler you have I don’t know why installers don’t got the little extra mile it is, and pipe it properly with a new modern x tank, and an air removal device. SMDH.
  • Gordy
    Gordy Member Posts: 9,546
    Old school air management.

  • Gordy
    Gordy Member Posts: 9,546
    edited November 2018
    Modern school air removal, and primary secondary piping using a hydraulic separator, or closely spaced tees.