Boiler Short Cycling

[John.g]

When you ran with rads+UFH1 can you remember the boiler flow/return temps and the (pump) flowrate?.

 

[John.g]

If you run only one UFH then a boiler temp of 70C will result in a boiler flow of only 3.39LPM, 0.2m3/hr and a boiler dT of 33C which will probably cause the boiler to trip, if you reduce the boiler temp to 55C then the boiler flow is 6.21LPM,0.37m3/hr and a boiler dT of 18C. Running both UFH with boiler at 55C 55c will result in the same boiler dT of 18C & a flowrate of 11.55LPM,0.69m3/hr.

 

[bagaceratops]

When you ran with rads+UFH1 can you remember the boiler flow/return temps and the (pump) flowrate?.

No, But I will take some measurements later. Thanks.

Is it likely that this is just a configuration / set up issue or boiler fault?
My engineer is coming back next week, but I am really not sure where to direct him and dont want to pay labour for nothing. I got the feeling when he was last here that he did not know where to look.

Thanks

 

[John.g]

If the fault is this "14C dT" issue then would appear to be a boiler fault, is this your only issue?.

 

[bagaceratops]

Hi Pretty much

Just fired up the CH, DWH off from relatively cold.
It seems to be cutting at dT of around 15 to 16 today
running at 3.2 head and 1.1 m3/hr

this was with d0 at 20
Dropped d0 to 10, but burner barely running and water not really heating

Guess I will need to get engineer back and have him call Glow worm for advice.

thx

 

[John.g]

Don't know if you made any progress but something strange (again).
If/when the rads only are on at 9.4kw then the dT should be ~ 7.4C at a flowrate of 1.1m3/hr so wonder if boiler sensors are OK even though you seem to prove that that they are/.

 

[bagaceratops]

Don't know if you made any progress but something strange (again).
If/when the rads only are on at 9.4kw then the dT should be ~ 7.4C at a flowrate of 1.1m3/hr so wonder if boiler sensors are OK even though you seem to prove that that they are/.

Not really, otherthan it works much better with d0 set at 21. Although concious that this is not enough power when everything is on and when it is cold.

Just tried now from cold (was at 28 degrees)
Boiler headed up to 70 and settled at
flow - 70
return 57
3.47 head
1.18 flow

I put temp probes on the flow and return into the boiler and the readings pretty much (<5 degrees) matched what d40 and d41 were saying.

I have my heating person coming back next week and have e-mailed glow worm who have given me a number for him to call and do some tests. I asked if I could do these tests etc, but was told that need specialist equipment?

Thanks again

Andrew

 

[ShaunCorbs]

How fast did the return get to 57 ?

 

[bagaceratops]

Not really, otherthan it works much better with d0 set at 21. Although concious that this is not enough power when everything is on and when it is cold.

Just tried now from cold (was at 28 degrees)
Boiler headed up to 70 and settled at
flow - 70
return 57
3.47 head
1.18 flow

I put temp probes on the flow and return into the boiler and the readings pretty much (<5 degrees) matched what d40 and d41 were saying.

I have my heating person coming back next week and have e-mailed glow worm who have given me a number for him to call and do some tests. I asked if I could do these tests etc, but was told that need specialist equipment?

Thanks again

Andrew

Did not time it, maybe 20-30 mins

 

[John.g]

Not really, otherthan it works much better with d0 set at 21. Although concious that this is not enough power when everything is on and when it is cold.

Just tried now from cold (was at 28 degrees)
Boiler headed up to 70 and settled at
flow - 70
return 57
3.47 head
1.18 flow

I put temp probes on the flow and return into the boiler and the readings pretty much (<5 degrees) matched what d40 and d41 were saying.

I have my heating person coming back next week and have e-mailed glow worm who have given me a number for him to call and do some tests. I asked if I could do these tests etc, but was told that need specialist equipment?

Thanks again

Andrew

< 5C might be significant if it resulted in your dT being 8C (13-5), this, assuming flow rate correct results in a heat demand of 11kw not a whole lot away from your rad demand assuming you didn't have the ufh or cylinder calling for heat.
Hope your heating person at least brings a multimeter with him/her to measure the flow/return sensors resistance and confirm them with Glowworm, probably did that at the last visit anyway.