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Uneven radiant heat...

SteveR Member Posts: 18
Have a radiant floor heating system with Weil/McClain boiler and Uponon/Wisbro manifold. The system is  configured with 3 zones and two loops per zone. Upgraded from the older Wisbro telestats...the ones where you couldn't tell if they were on or not...to the newer Uponon telestats. One zone is for the two spare bedrooms, one of which heats up relatively quickly, and the other one takes quite a bit of time to heat up. I figured there was a possibility of air in the one loop, so I removed all the telestats from the manifold and closed down all the balancing valves except the offending one. I then ran the system for quite some time before any appreciable heat was noticed in that bedroom. All the other zones/loops seem to be working fine, and the system is running at 20psi. Am I doing all I can do, or am I missing something? Thanks.


  • Uneven Heat

    Did it work OK with the old manifold?  Does the new manifold have flow meters?  You should have about a 1/2 gallon per minute flow.
    Often wrong, never in doubt.
  • SteveR
    SteveR Member Posts: 18
    More info...

    The manifold has not been replaced, It is the same one since the house was built, and there are no flow meters. All this started a few weeks ago when I noticed a couple of loops were not heating. I brought in a contractor friend whose main field of expertise is plumbing and he determined there was no pressure in the system. He reconfigured the system with a quick fill valve, new/larger expansion tank, tpr valve, and a device to remove air in the system. At the time I had to purge one loop at a time, and it appeared that each loop was heating correctly. However, I went into one of the bedrooms last week and noticed it was quite cold, whereas the other was quite warm. I'm talking 60 degrees versus 70+ degrees.The thermostat is in the bedroom that is cold, so while it keeps calling for heat, the other bedroom gets excessively warm.  I tried purging the colder loop most of yesterday and it never seemed to heat as well as the other bedroom. I've convinced myself that these systems are nothing but valves that open and close and moving hot water, which leads me to believe there is something impeding the flow in that one loop. The other four loops are working fine.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,839
    Delicate balancing act...

    The older style of brass manifold had adjustment capability under the telestat operator. Hopefully, somewhere around your house you have some black plastic conical looking devices that originally came mounted on the Wirsbo manifolds. They look like a manual close off valve, and in fact are use for that purpose during construction, PLUS, if you take it off and turn it over with the pointy side pointing down, you can place it over the small stainless steel pin that is connected to the plunger of the individual circuit valve. There are two small prongs that fit in to two receiver slots. THis will allow you to turn a small round disc. This is the maximum opening capability if the actuator assembly. Normally, there should be about a dimes thickness of black plastic showing above the brass receiver that it threads in to. I have seen these completely closed, which will allow ZERO flow.

    Also, generally speaking, if you have the white plastic tubing, and you have air in suspension, you can see the bubbles working their way through the tubing. No bubbles, no air, or no bubbles, no flow... You can tell by the tube temperature. If no bubbles, but tube is warm, then no air, you have limited flow.

    Another thought, if you used the newer motorized telestat operators, as you are screwing the operator down on to the manifold receiver, you don't want to screw it down completely hard. There is a "neutral" point that you must achieve, otherwise the valve will not open, and the end switch will call continuously. There is a wiper arm that indicates wether the valve is open or closed, and with no power to the operator, you want to turn the telestat down until the wiper arm is in the CLOSED position. No more, no less. Then turn it up and see how it works.

    If you used the heat motor type of operator (real slow reaction time, like in minutes) then with that operator, you do screw it down snugly.

    Most technicians are not aware of this critical adjustment, They just swap operator for operator, screw it down and walk away.

    Good luck. ANd Happy New Year...

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • SteveR
    SteveR Member Posts: 18
    edited January 2011
    More info...

    First off, thanks for the responses. I do have the conical shaped tool and have used it to adjust the valves. The instructions I received were to only back out the valve 4 half turns, and that's what they are all set to....just below the top of the brass fitting. If I can back it out more, I will. Things worked fine for about 14 years until the discovery of the lack of pressure. I have one of the motorized zone valves and 5 of the newer Uponon telestats. The motorized one is twisted on just to the green dot, and the others are snapped onto their rings.

    Don't have much tubing (white/clear) pex to look at.

    What I've been doing to purge the system, is manually close....with the aforementionded tool....each loop except the one I want to purge and set the thermostat up for a couple of hours until I detect heat in that bedroom.

    Right now, I am letting the two bedrooms (unused) drop temperature, and will make sure I have the right telestat for the right loop/bedroom.

    Again, thanks for the responses.
  • SteveR
    SteveR Member Posts: 18

    As I said previously, I don't think these systems are that complex...just valves opening and closing and pumps moving water. I just started this morning by shutting off the valve to the  one bedroom that was heating and opened the valve (balancing) on the manifold to the bedroom that didn't seem to be heating. Did some running around and returned about 4 hours later, and that bedroom had gone from 58 to 63, which is where I set it to shut off. I guess the bitter cold over the weekend might have been a problem, but things seem to be fine now. It just may have taken a while to purge the loop. Again, thanks for the responses.
  • Kilroy
    Kilroy Member Posts: 1
    Uneven Radiant heat

    I build my home with Wisbro radiant heat system. I found the installation to be simple, but I error-ed in making significantly different length loops within each zone. Oops.

    The longer the loop the more resistance to flow. If you open all valves to the max it will cause the fluid to take the path of least resistance (i.e. the shortest loop).  Therefore, the shortest loop will get the greatest flowrate and heat up faster. You need to restrict the flow in the shorter loops to force liquid into the longer loops. I hope this helps. To determine loop length find the printing on the tube and the number is at the end of the label (ex. 09410). Find the number on both ends of the loop (supply and return ends) and subtract them. All adjustments are based on the longest loop within that zone.  

    I just installed zone 3 in my home and I need to go and balance it now. 
  • uneven floor heat

    I have seen debris in the valve section of the manifold. you could check there.also do you know the loop lengths?
  • SteveR
    SteveR Member Posts: 18
    Loop lengths....

    According to the map of the system, all the loops are around 300 feet. The system has worked fine for 14+ years. Seeing as I don't usually heat those two bedrooms, they don't get much use. After the water pressure problem, I think being dormant for so long, that particular loop was full of air. So I just took the zone valve off that loop and when ever the other zones called for heat, it eventually forced what air was in there out. I have a pressure guage installed so I can monitor the presssure so this won't happen again.
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