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Radiant Heat Leak? / Pressure??

Built a home 5-years ago up in the Colorado Mountains. Cold!

I am concerned about having a leak in the system and why the pressure in the boiler and manifolds drop to zero if you totally isolate them.

Have three loops coming off Buderus G234X-38 boiler.

-1,900 sq. feet / five zones of radiant on main floor

-700 sq. feet / two zones of fintube on second floor

-DHW tank

-Expansion Tank is Amtrol Radiant Extrol RX-30.

-Wirsbo hePEX 3/4" and 1/2" tubing

Plumber was totally incompetent. Couldn't tell me capacity of system, amount of tubing used, amount of glycol in system. Lots of other problems throughtout house. Seemed to get everything resolved about two years ago.

We opened autofill about 2-years ago, pressurized system, and turned autofill off. Last year, during winter we were running about 15-16psi with system off (nothing running but waiting for call for heat) and 23psi when system was running everything. This year, we are starting at about 8-9psi off and 21psi when running. 

Saturday, I opened autofill and it took about 3-4 seconds to bring pressure to 13psi. Afterwards, 24psi with everything running.

To try to check for leaks, I  shutoff system (electrical) and shutoff all valves, except for valve between boiler and expansion tank. Over a couple of hours, pressure dropped in all of the manifolds and eventually hit zero?? Boiler/Ex. Tank pressure held steady at about 16psi. Note - pressure gauge on supply line close to ex. tank.

I then shutoff valve between boiler and ex. tank. Pressure in boiler dropped to zero within 20 minutes. Ex. tank pressure stayed at 16psi. Opened valve - up to 16psi on boiler, closed valve - down to zero?? No visible leaks on any of the components.

Max. boiler temp. goes to 182. Temp. when boiler valve shutoff 120.

Is it normal to drop some pressure in this type of system over a couple of  years?

Why is the boiler going to zero?

Any suggestions on how to troubleshoot?


Fraser Jim


  • Paul PolletsPaul Pollets Member Posts: 3,017
    Fiind a Pro

    You need a Pro to troubleshoot and fix.  There is probably a leak, and the change in pressure tells that the pumps are pushing towards the expansion tank, rather than away (See "Pumping Away") The "near boiler" piping will probably need a re-pipe.

    Try Mark Eatherton if in the Denver area, or use "Find a Pro"
  • Tim PotterTim Potter Member Posts: 212
    Care to share ?

    Jim, who was your plumber or plumbers you have used?

    We also have a mountain house in Grand County with hydronic problems.

    You can click on my name to see my posts.

    If you don't feel like a public reply, would you reply privately?

    I second the suggestion to contact Mark Eatherton, the guy is very knowledgeable and helpful.

    Thank You :

    "Winter Park" Tim

    [email protected]
    Winter Park, CO & Lenexa, KS
  • fraserjimfraserjim Member Posts: 3
    Pump Away

    Well - I don't think that the circ. pumps are backwards.

    I have 5  TACO pumps.

    I will attach some pictures and a drawing.

    I compressed the pictures. Have better ones.

    The second picture shows the main rdiant heat loop pump, the fintube pump, and the DHW pump. All on the ouptu side of the expansion tank. The other two (not shown) are on the radiant heat supply manifold and the variable speed injection pump from the main loop to the radinant heat loop.

    Are there markings on the TACOs to determine which way they are set-up?

  • Paul PolletsPaul Pollets Member Posts: 3,017
    Header size

    Is the boiler header 11/4 or 11/2"??  An undersized header will limit flow. The rest needs to be looked at by an expert.
  • fraserjimfraserjim Member Posts: 3
    Header Size?

    Hi Paul - Not sure what you mean by "header".

    Are you refering to size of supply line and return line in and out of boiler?

    If so, at least 1-1/2" maybe 1-3/4". I will attach photo showing part of expansion tank on right and supply going up from boiler on left. Hard to tell. I do have some foam on lines to prevent heat loss but thought that you may be able to judge based on drain valve size.


  • Paul PolletsPaul Pollets Member Posts: 3,017
    The header

    The header is the supply (or return) piping attached directly to the boiler that the distribution piping connects to.  The header needs to be sized for the load. i.e., If the zones require 140,000 BTU's, the header needs to be 11/4".

     If the header gets choked, or is undersized, flow rates to the zones will be reduced accordingly. Different pump sizes on the system would also influence the flow rates in adjacent zones without proper header sizing, and "ghost flow" is inevitable.  Some installers now use "low loss headers" or hydraulic separators to make the whole process easier. 
This discussion has been closed.


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