Heating circulator incorrectly sized?

[bhm1712]

That concurs with the readings I just took - before the bypass I have 55 degree return and after the bypass the return increases to 63 degrees going back into the boiler. What a waste. I shall carry out the experiment tomorrow.

 

[bhm1712]

So at setting 2 which is 2 litres a minute that means the boiler has only 2 litres a minute flow on pump over run. Is that acceptable? Doesn't state the over run flow figure in the manual only the minimum flow during fire

 

[D_Hailsham]

So at setting 2 which is 2 litres a minute that means the boiler has only 2 litres a minute flow on pump over run. Is that acceptable? Doesn't state the over run flow figure in the manual only the minimum flow during fire

Don't forget that the boiler is not alight when on pump overrun; the water temperature will be dropping all the time; flow and return temperatures will be almost identical when overrun stops. Also the boiler may be off - flow temperature reached - but the motorized valves are still open as room not up to temperature. So there is still circulation through the rads.

The main job of an ABV is to ensure that there is a minimum flow through the boiler when rads are closed by the TRVs and only the rad without a TRV is open. 'Minimum flow' is a misleading name as it really means 'maximum differential'. So the ABV has to be adjusted so the differential across the boiler does not exceed 20C when only the rad without a TRV is on. In this situation the boiler will have modulated down to minimum output and may be running in on/off mode.

I would ask for the ABV to be installed before forking out £250+ for the UPS2 25-80.

 

[PullerGas]

Ah, I see you've taken the 'professional' advice & checking/adjusting/replacing the bypass.

Try the rest then try the best!!

It's not rocket science, like most pros I just think of how the water will flow & the route it'll take. So don't go thanking me FFS!!!

 

[bhm1712]

I've not agreed or taken anybodies advice to do anything yet it was the engineer who suggested this on the blower last night as he said the manual states it should be an ABV not a manual bypass. I was asking you guys for your opinions!!

 

[Steelmasons]

15/60 circulator is undersized , either install an additional 15/60 in series or change existing 15/60 for a 25/80....
Forget all this temperature nonsense , only the inexperienced use temp probes for balancing.

 

[Spark74]

Good read

 

[bhm1712]

More investigations have been done this weekend. Looks like the CH flow and returns split into 2 just behind the boxing in after the motorised valves. One leg feeds downstairs and the other goes upstairs. If you measure the flow and return temps after the split in pipework there is an obvious mistake somewhere in the pipework. The downstairs leg has a flow of 70 and return of 54/5 but the upstairs leg has a flow of 70 and a return of 66 which the engineer says points to an unrestricted joint between flow and return somewhere upstairs under the floor - all radiators apart from the 2 cooler ones have a 15 degree differential from a flow of 70 degrees and so couldn't possibly create a return temp of 66 degrees. This may be why the 2 radiators struggle with flow temperate being 8 degrees different than the others in the system. Next step - floorboards up he says!

 

[bhm1712]

Said this arrangement of pipework (seperate up and down legs) should have been 2 zones not just the one.

 

[St0rmer66]

"ideally" should be two... but there are millions of homes where they have exactly what you describe (upstairs/downstairs). Definitely a common thing.