Radiators not getting hot enough, pump on constantly-help!

wizzer

moneysavingplumber wrote:

The boiler and pump are not really supposed to cycle on a system where the by-pass and lockshield valves have been set and balanced correctly. If it is working and sized correctly then the boiler should stay lit (more or less) until the room and cylinder stats are satisfied. Obviously a higher temperature on the stats will mean you will burn more gas. If you want to set your cylinder stat at 50 that is entirely up to you, but the current recommendation is 60.

If the flow temperature at the cylinder coil inlet (flow) is at around 60-65 degrees, the return should be 40-45 degrees. This is usually achieved by a lockshield valve on the cylinder return immediately upon exiting the coil which is restricted to achieve the differential. The system by-pass will usually be set up whilst the system is in hot water mode only so as to be sure to give the correct differentials between boiler flow and return whilst the system is on minimum load. Radiator valves need to be set in the same way.

If you are saying that the cylinder stat is not being satisfied at 55 degrees then you may need to check the calibration of that and the boiler stat. Ultimately, all this type of thing is the responsibility of the people that fitted the boiler under Benchmark and the Part L building regulation. I assume the installation was registered with building control via Corgi. If not, it should have been, and if it was, Corgi may select you for a spot-check to see if it's been installed correctly, I know they've contacted a few of my customers.

Our old boiler and pump etc was located in an understair cupboard that was more or less directly beneath the airing cupboard where the cylinder is. We've moved the boiler into a utility room and this means that the flow and return pipes must be about 4 metres each from/to the boiler and the cylinder and pump which has been put into the airing cupboard. Should the distance between the boiler/cylinder etc have any affect on anything?

Thanks
Wizzer

Whiteboard

I had the same problem with my rads being only warm at the top and cold at the bottom.
I was advised to either replace the rads (as the boiler was definately fine as the hot water tap was scolding) or to power flush the system.
Due to the fact that the rads were really old, didn't have any convectors (fins) on them and the bleeding key area had been painted over I was told that even if I flushed the system which costs a few hundred quid it may not even help.
I therefore replaced all the radiators in the house with new modern radiators with convectors and the house is amazingly hotter than I ever could have imagined.

moneysavingplumber

wizzer wrote:

Our old boiler and pump etc was located in an understair cupboard that was more or less directly beneath the airing cupboard where the cylinder is. We've moved the boiler into a utility room and this means that the flow and return pipes must be about 4 metres each from/to the boiler and the cylinder and pump which has been put into the airing cupboard. Should the distance between the boiler/cylinder etc have any affect on anything?

Thanks
Wizzer

If the HXi is 24KW then the primary flow and return pipes should be 28mm, even though the spigots provided from the boiler will be 22mm. Assuming that has been done correctly then 4 metres is fine. Even though the Gloworm HXi series are modulating boilers, for a 24KW to be fitted then the heat loss for the property would have to be at least 18KW which I would still have used 28mm primaries for, even though it would be 6KW short of the boiler's optimum output.

farrbott

I've had a similar but more dramatic problem. Had my system drained to fix valves, when refilled the rads don't get hot at all, not even the feed pipes! Now replaced all the rads as had the sludge idea thrown at me too. All rads now new and when the system was fired up downstairs got hot but not up. So the plumber turned off the rads downstairs to force all the pump power up. No luck yet. Just turned on downstairs rads and no heat there now. Boiler makes scalding hot water, very confused... help and ideas?

aboard_epsilon

farrbott wrote: »

I've had a similar but more dramatic problem. Had my system drained to fix valves, when refilled the rads don't get hot at all, not even the feed pipes! Now replaced all the rads as had the sludge idea thrown at me too. All rads now new and when the system was fired up downstairs got hot but not up. So the plumber turned off the rads downstairs to force all the pump power up. No luck yet. Just turned on downstairs rads and no heat there now. Boiler makes scalding hot water, very confused... help and ideas?

youve just answerd a post made 5 years ago ..

all the best.markj