old radiant system problems

Weezbo

therefore the first inability to purge a line should alert you to the minor technicality. give it a another path home than the one you Thought was the path home. see which witch is which sorta speak.

Bill_39

radiant

I went to a house that was built in either the 50's or 60's. The house is on a slab. Most of the first floor is radiant. The boiler is an 80,000 output hydrotherm boiler thats in the attic. There is a small zone of baseboard on the first floor (about 15') And another on upstairs about the same. The pump is on the return and there are zone valves. There is a 3/4 supply and return each going to manifolds with 6- 3/4X 1/2" od copper tees and there is no injection or mixing valves. The manifolds are in the laundry room which is right below the boiler room. THe problem is that the radiant zone does not heat. THe bathroom which is right outside the laundry room gets hot and thats it. The rest of the rooms all have rugs which is part of the problem but even the concrete under the rugs is not getting hot. There are six loops off of the manifold and two of the return loops are hot two are cold and two are warm. I tried purging the ones that were not heating and it didn't work. I also tried closing the valves on the ones that were heating and nothing changed. the radiant tubing is all copper. If I turn off the radiant zone and run one of the other zones the water will go up to 180 but then as soon as the thermostat for the radiant calls the temp goes down to 140-150?. The people just bought the house in May so they don't know if it ever worked right. I am obviously missing someting does any one have any ideas of what the problem could be?

Bill_39

I am able to purge

I just don't get any air

S Davis

Path of least resistance

If all of the zones are running off one pump your flow is probably taking the path of least resistance wich would be your baseboard zones, the radiant floor zones that are getting some heat are most likely the shortest loops.
I would put in some type of mixing and a dedicated pump for the radiant.

S Davis


Apex Radiant Heating

Bill_39

Yeah but

even when the zone is calling by itself the same thing happens. I wasn't going to put mix it because when they did the heat loss they must have done it for 180 degree water because the way it is set up it is pumping 180 through the radiant.

S Davis

Pump Head

It is also possible that the head pressure is to high for your pump in those loops so you get little or no flow, what are you pumping with, also any idea how long the loops are, do you know what areas each one serves to give an estimate of length.
As for the mixing I have been designing and installing radiant for 17 years and never had a heatloss that required 180 degree water on a slab job, they probably did not do a heat loss because somone that took the time to do a heatloss calc would most likley know not to send 180 degree water into a concrete slab.

S Davis


Apex Radiant Heating

Bill_39

ok

It is a 007. I have no idea how long the loops are. I think some of the loops are way too long though because from where the manifold is to some of the rooms are is a long distance and there are only six loops. If I do mix the radiant that should keep the water in the boiler temp from dropping right down as soon as that zone calls right? I don't think it ever worked right.