Radiant heat on when thermostat says off

Phil Fluke

Attached is a photo that shows the two pumps that "leak". (my term for allowing heat to move pass them and heat the zones) The other is an overall shot of the system. It has happened since I have owned the house, 10 months but hard to notice in the summer. The problem seems to arise most when the added pump (in upper left corner of overall shot) is active. In looking at the overall shot it seems the two "offenders" are on the primary loop. So is the hot water heater, but who would notice if when it was heating? All the other zone pumps are in a secondary loop that is after the mixing valve. Should cut off valves activated by the control box be added to these two pumps?

Phil Fluke

Radiant heat on when Thermostat says off.

Help! I have a gas boiler feed hyronic heating system which feeds hot water to the baseboards in two rooms when the thermotstats are set at very low temps. It seems the hot water from the primary loop is getting past the recirculating zone pumps even when they are not running. It cools the loop and the boiler fires to keep up. This causes 78 degree room temps in the middle of the night when the outside temp is in the single digits. Its costing me a fortune in heating bills. How can I check whats wrong or if the pumps are bad?

Weezbo

oops

Weezbo

sounds like You Got Heat syndrome...

not quite the same thing as you are comfortable.

could be a lot of things. one might be the piping arrangement, another the control strategy, distribution design, building design...hard to nail that down without some clearer picture than what you describe...

Jeff Lawrence_25

Do the

Pumps/circulators have check valves on them?

Did this problem just show up?

Weezbo

that lash up looks a little bit \"Busy\"

i am somewhat curious as to the by pass around the mixing valve ...i call some bypasses by different names,not all bad mind you however that by pass i would call a step up by pass or my technical name for it is an acceleration bypass.

it is open.

not required once the heat is into the system.

i use it to bypass hydraulic control through a mixing valve yet i tend to like a gage to allow me to determine what the exact temp is going into the loops...


there are some other minor technicalities that i see yet i will let some other voices remark on them , that way i don't become the bad guy and the object of your frustration.

i stared at this picture for a while now,... and i am beginning to wonder if this is pumping away or exactly what you have going i think maybe one more pic from 90 degrees from the pic 2 might help.

you have 4 circ controlled zones off the mixing valve two more for the staple up and a parallel primary for the indirect ,?

i magnified the pic a bit and your mixing valve looks like
the ball valve is the return path back so it isn't an acceleration bypass,its the return.

.

ok i looked at it some more, i tend to think that the offending circulators are not the problem. what you have is over shoot into the radiant hose ...that means the control of the water temps through the system is not in step with the temp you actually need. you could put some variable speed circs controller on the loops , or make a n injection loop to a separate header with those two zones with outdoor reset. constant circulation doesn't bang off an on like a snap switch or relay.

Rich L.

Thermal Siphioning

Phil you may have Thermal Siphioning going on. This happens by natural convection. In other words the warm less dense water is naturally rising through the supply piping to the base board above while the cooler denser water "falls" down the return pipes to replace it.

One way to over come this is to add thermal traps. These take the warm supply water from the pipe and first travel down towards the floor, minimum of 18", all the way to the floor is better, and then up to the base boards. This would require adding some pipe to your system. Another method would be to add a spring loaded check valve to the supplies. Not my first choice but this works by restricting natural warm water convection when the pumps aren't on. The pumps push them open when they come on. The other method you're describing is a zone valve. It's an electrical mechanical valve that opens on a call for heat and allows water flow. Generally you see either pumps or zone valves rather than both together. I've never seen them together but it may be able to be done.

I can't see your entire system so that would be my best guess from here.

Phil Fluke

I tried to diagram the system in the attached drawing. I simplified it a bit but this is what the layout looks like without the complexity of actual pipe routeing. The open valve in the acceration loop is baffelling me. It seems that should be closed with all cold water returns going in the cold side of the mixer. Any advise is welcome.

jp_2

primary pump?

if the primary pump is oversized, causing too much pressure in the primary loop, causing flow checks to open in those two zone loops?

Weezbo

i think i see it clear.

i sent you an e-mail because i thought there were some difference in terms , the bypass on the return is just a normal path back into the boiler with the option to feed cool water to the mixer, usually i put a check against flow on that return so that more resistance is created and to keep unwanted thermal migration occurring .

when i pipe around the supply to the heated mix , i call that an acceleration by pass an i put a simple ball valve on it,.. the idea is should the system freeze of some part of the system say a single loop in the field,... then you can hammer the near by zones with heat at a much higher temp than you would get through the mixer.

if the loop from the boiler had a take off for the Indirect over and back and the heating loop was taken off after that with the boiler as a secondary , then you would have lower water temps rolling through the onix hose. it would no longer need to make 180 F water for the Indirect..flow past the take-offs for the hose.

that way you could modulate all the temps down ,...

We would call that a Parallel primary to the indirect. with primary secondary piping arrangement,take offs for multi temperature fluids, and a secondary take off for a remote low mix temp header. sounds like some kidna florin language *~/:)

Thats me two shillings ... i will send you a picture what that would look like..