Central heating pump

[sherylryan]

Can you shut those valves temporarily and put a note on the gas boiler to that effect and see how the UFH operates.
Can't see attachment 76410 re DHW.

Yes I can shut those valves temporarily, if the rads call for heat off this troubled boiler they use those pipes for flow and return, both boilers can not operate at the same time. The gas is purely for backup.
Attached DHW graph

 

[John.g]

If you mean that the boiler ran continuously for 45.37 mins then its output was ~ 19.7kwh and if all that energy was inputted to the hot water cylinder then the cylinder volume would need to be 846 liters to only rise by 20C, not likely, if the HW cylinder is say a more realistic 250 liters then it would only take 5.81kwh or 13.5 min to rise it by 20C. still not clear as to what's going on but with these valves now closed then it may be become clearer.

 

[sherylryan]

If you mean that the boiler ran continuously for 45.37 mins then its output was ~ 19.7kwh and if all that energy was inputted to the hot water cylinder then the cylinder volume would need to be 846 liters to only rise by 20C, not likely, if the HW cylinder is say a more realistic 250 liters then it would only take 5.81kwh or 13.5 min to rise it by 20C. still not clear as to what's going on but with these valves now closed then it may be become clearer.

No boiler didn’t run continuously, the blue on the graph is where the flame stops but the pump still runs to circulate the water, the boiler only fired for 29 mins 38 seconds out of the 44.37 mins (sorry was not clear on my outcome)

 

[ShaunCorbs]

There’s a set of valves on the boiler so worth a test

 

[sherylryan]

No boiler didn’t run continuously, the blue on the graph is where the flame stops but the pump still runs to circulate the water, the boiler only fired for 29 mins 38 seconds out of the 44.37 mins (sorry was not clear on my outcome)

Hi John
I run the troubled manifold with the rad valves turned off and the boiler return temp was exactly the same as the ufh manifold return temp. Although the boiler ran continuously for 42.07 mins and only got to 59 degrees. The manifold points you told me to measure were spot on, so the TMV is doing it’s job. I now believe the pump set to constant pressure and being such a big pump is another issue, as water was also bypassing through the external bypass.

As you can see the Rads literally T into the flow and return so no valves to stop the flow of water, with valves turned off water was still flow the this point in these pipes.

 

[John.g]

So install zone valve on rads and problem solved?.

 

[sherylryan]

So install zone valve on rads and problem solved?.

There are zones valves already on the rads but because of the new piping the have stuffed it up, so new pipe work and zones valves I’m picking