single loop HW flow problem

MrLeahy

Hello,

Have a problem with my heating system that I would like to resolve before this year's heating season comes along...

Two zone house - cast iron radiators. both zones are on a single loop. One of the zones radiators do not get hot towards the end of the line. Base on the attached diagram the water temp on the main pipe coming in at 'A' is hot, coming out of 'B' is also hot. Coming in on 'C' hot, coming out of 'D' warm and the trend continues. at the last radiator inlet 'E' the main pipe is completely cold.

Now, all the radiator valves are all the way open except for the one betweeb 'A' and 'B' and 'C' and 'D' as those get extremely hot. One between 'A' and 'B' is partially open, the one between 'C' and 'D' is completely closed as that room is rarely used.

The thermostat is located in the room where we have 3 radiators, the one btw 'E' and 'F' is one of them. Now regardless of how high we up the thermostat, the temp never gets to that point and the boiler shuts of - not sure why this is happening. Is it because it thinks the water temp is hot enough already?? There are are no manual bypass valves or balancing valves on the main line.

The other zone is not having any issues at all - its smaller and has baseboards. aquastat is set at 140/110 diff 20

ANy help would be greatly appreciated!

bob_46

Flow

What you have drawn is a Mono-flo system. If in fact it is you can,t close any valves on the radiation as this will reduce the head pressure available .

lchmb

problem radiator

Bob is correct in what he posted, my next question would be if there is a bleeder on the radiator and if it has been purged? If the radiator is air bound it would also make it stay cold.. As far as the boiler, if your reading the triadicator it could be faulty and or your aquastat is.

JStar

RE

Possible solution - 3 way zone valve.



You can install the valve on any radiator branch that you want to control. You'll control the valve with its own thermostat. When the valve closes, it will bypass the radiator, and send the water pressure back to the return monoflo tee, keeping system pressures where they should be.