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Intake and return manifolds

nckennedy
nckennedy Member Posts: 11
We just noticed recently that on two of the radiant floor heat zones, the return manifolds are cold to the touch, while the sending manifolds are hot. On another zone both the sending and return manifolds are hot to the touch. So I am wondering which is correct? My understanding is that for an efficient system the water temps only should vary a few degrees between the sending and return? So what might be causing this apparent extreme temps? Pumps appear to be working, or at least turning ok.
Thanks for sharing any ideas you might have.

Comments

  • Peakedtoosoon
    Peakedtoosoon Member Posts: 59
    Any Pics of manifolds?
  • Jamie Hall
    Jamie Hall Member Posts: 20,432
    Assuming that the radiant is constant circulation, which it should be, he area served by the cold manifold isn't getting much if any flow. Then the question is -- is it heating the floor, and if not, why not?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 18,195
    Do the two zones have different circulators, or zone valves to turn them on and off?
    How many thermostats do you have?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • nckennedy
    nckennedy Member Posts: 11
    We have three zones in service at present, others are planned but not hooked up yet. Each zone has its own pump controlled by its own thermostat.
  • Kickstand55
    Kickstand55 Member Posts: 79
    Is this a new system untested prior to this question?
    If so, are there any pics and or blueprints of the layout?
  • hot_rod
    hot_rod Member Posts: 18,195
    Is it radiant in a concrete slab.. if so it can take hours, maybe a day to get up to a condition wher the temperature difference is 15 degrees between supply and return.

    Usually within a few hours you can feel some temperature difference.

    If it is low mass radiant, plates below the floor it will warm faster. Easily within an hour you’ll feel the system heating at the manifolds

    If not, you may have air bubbles in the loops.

    Assuming the pump is actually spinning?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • mattmia2
    mattmia2 Member Posts: 7,156
    btw, with a mod con boiler bigger differences between supply and return are usually more efficient.
  • nckennedy
    nckennedy Member Posts: 11
    This system has been in place for about four years. I tried to open a value going into the manifold to check for air, but didn't get much. Water just trickles out, very low volume; is that normal? See pics below.
    Craig




  • mattmia2
    mattmia2 Member Posts: 7,156
    what does the pressure gauge on the boiler say?
  • nckennedy
    nckennedy Member Posts: 11
    Oh my. That's a good question. It is only 2 or 3 pounds max. on the gauge. Temp is up to 110-120.
    So what does that mean? Bad pump? The pressure gauge is on the outlet pipe from the boiler then followed by a gate value. I turned the value off for a moment and pressure went up to 20 or so lbs.
    Any ideas?
  • Jamie Hall
    Jamie Hall Member Posts: 20,432
    If the pressure went up and the pump was pumping against the closed valve (?) then the pump is working -- but if the system pressure is that low, you have lots of air in there and not a whole lot of water. You'll likely need to purge the whole system, zone by zone, to get rid of all the air, and then repressurise it and see if it holds.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • nckennedy
    nckennedy Member Posts: 11
    Wow, ok. One of the zones seems to be working ok, so I guess I should start with the worst zone.
    So to do so I need to open the evacuation value just after the return manifold and let out any air. Will the automatic value that controls new water coming into the system allow more water into the system? I am just thinking I may have to leave the evacuation value open for a few minutes in order to get all the air out?
  • hot_rod
    hot_rod Member Posts: 18,195
    edited January 20
    Your auto-fill valve should have a fast fill mode that you engage when you purge to assure adequate flow to push the air out. Do 1 loop at a time. Purge into a plastic bucket so you see when all the air has come out.

    A pic of the fill valve or look up online to see how to activate fast fill mode.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • nckennedy
    nckennedy Member Posts: 11
    Oh great. Can do that. Makes sense. I will try it and let you know on the worst (coldest) zone first.
    Thanks
  • nckennedy
    nckennedy Member Posts: 11
    I drained off about 3 gals of water with the auto fill value open and the return manifold value open. Water pressure jumped to 20 lbs or so, return manifold got a little warm after a couple of hrs. but this AM it seems to be cool again but water pressure is still up.
  • hot_rod
    hot_rod Member Posts: 18,195
    Are you certain the boiler is running the whole time. You either have flow issues or temperature issues.
    Did you purge the loops one at a time?

    If you turn off all but two loops do those warm up, that would indicate inadequate flow when all loops are opened.

    Pump is on speed 3?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • nckennedy
    nckennedy Member Posts: 11
    pump was on speed 1 so I changed it to speed 2 I only pursed one loop so far. I will do the other today.
  • hot_rod
    hot_rod Member Posts: 18,195
    When you purge, the ball valve, lever handle, to the right of the drain/ purge valve is turned off, Correct?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • nckennedy
    nckennedy Member Posts: 11
    No I didn't turn it off. I will try it again and turn it off first. I did turn off the values going in and out of the boiler
  • nckennedy
    nckennedy Member Posts: 11
    I turned off the ball value, opened the drain value that is attached to a hose and did get some air out of it. But the water soon stoped. Apparently the zone had drained dry, so I close the drain value opened the ball value and returned auto-fill value to normal. Still have a cold return manifold. I am not doing something correctly.
  • hot_rod
    hot_rod Member Posts: 18,195
    Are you sure that purge valve is on the return manifold? Water needs to flow out the supply manifold, around the loop, stop at that ball valve to purge out.

    Or else the fill valve is not filling or filling fast enough. Close all the white handle loop valves but one, see if one loop will keep flowing. If so you don’t have adequate fill flow.

    Could be the strainer in the fill valve is plugged. A pic of the entire boiler piping would help.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • yellowdog
    yellowdog Member Posts: 22
    radiant can be a pain to purge all of the air out of. even more so if the installer did not line up the loops correctly. i would first start by verifying that the loops line up, then purge them one by one always closing a loop after it is air purged. you also want to start with the one farthest away from the purge valve and work your way towards it. with the impressive amount of different tubing and different fastening types, i would almost assume that the loops do not line up which will make it impossible to purge until you identify each loop.
  • nckennedy
    nckennedy Member Posts: 11
    Ok, But what do you mean by "lining up"? Well, I finally called in a professional, guy that made all the connections. I did the pex and manifold install. It took him a while but he discovered that the internal check value in the circulation pump had stuck closed. So he is coming back in a couple of days to replace the pump. So we should know soon as to the final outcome. I will send you an update in a few days after the new pump is installed. We will have to purge it of course after it's installed. Thanks for all your input. I feel that I have learned a lot. Craig
  • yellowdog
    yellowdog Member Posts: 22
    @nckennedy a quality contractor will line up pex loops on supply and return manifolds so the farthest ones to the left are 1 loop then the next 2 are the next loop and so on. a fly by night contractor will just cut the tubes and attach them to the manifold in any order that they choose not caring to make it simpler for anyone down the road to identify each loop.
  • hot_rod
    hot_rod Member Posts: 18,195
    A label on the pex loops help keep the straight also, just a magic marker number will help keep them paired correctly.

    No harm from marking pipes.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    yellowdog