Hi,
We've lived in our house for 8 years. It was a repossession, so when we moved in the CH was drained. I filled it and added inhibitor. It's worked pretty flawlessly since, except for needing a new circulation pump in Jan 17.
Earlier this week, I noticed that the radiators towards the end of each circuit were cold. When the boiler came on from cold, it was only on for a few minutes before the limit stat started kicking in and out. Normally it takes a lot longer for this to happen, whilst the full system gets warm.
The circulation pump didn't sound right, so I had it replaced under warranty. It was a Salus MP100A. The funny noise went but the problem remained. It's a variable velocity eco pump and I noticed that it was running slow (as if all the TRVs were closed and it was sensing low heat demand - they weren't)
Having read that Salus pumps are not the best, I decided to replace with a Grundfos UPS2 15-50/60, thinking my replacement Salus was a dud.
It wasn't, I still have the same problem. I've tried running the Grundfos at full speed on the constant velocity setting rather than the variable, and it makes no difference, other than to make the pump housing very hot. I've put it back to variable velocity now, but as with the Salus, it runs slow as if it is sensing low demand.
The only way I can get the cold radiators warm, is by turning other radiators off. They heat up nicely but as soon as I turn the other radiators on again, they go cool.
So for whatever reason, the pump can't push water far enough out to the furthest radiators. At present we have 3 hot radiators (these ones are on individual 15mm legs fed from a 22mm pipe) and the rest are tepid or cold. There are two other legs, but these each have 2 radiators on....again in 15mm fed from 22mm...in both cases the first radiator in the leg is tepid and the 2nd cold. If I leave the heating on for hours, the cold radiators eventually get tepid.
I'd appreciate it if anyone can suggest where to look next? Logically I'm thinking a blockage somewhere but not sure where to start with that. I've seen suggestions about balancing the radiators however the lockshields and TRVs are fully open on all the radiators and always have been?
Thanks in advance
Andy.
We've lived in our house for 8 years. It was a repossession, so when we moved in the CH was drained. I filled it and added inhibitor. It's worked pretty flawlessly since, except for needing a new circulation pump in Jan 17.
Earlier this week, I noticed that the radiators towards the end of each circuit were cold. When the boiler came on from cold, it was only on for a few minutes before the limit stat started kicking in and out. Normally it takes a lot longer for this to happen, whilst the full system gets warm.
The circulation pump didn't sound right, so I had it replaced under warranty. It was a Salus MP100A. The funny noise went but the problem remained. It's a variable velocity eco pump and I noticed that it was running slow (as if all the TRVs were closed and it was sensing low heat demand - they weren't)
Having read that Salus pumps are not the best, I decided to replace with a Grundfos UPS2 15-50/60, thinking my replacement Salus was a dud.
It wasn't, I still have the same problem. I've tried running the Grundfos at full speed on the constant velocity setting rather than the variable, and it makes no difference, other than to make the pump housing very hot. I've put it back to variable velocity now, but as with the Salus, it runs slow as if it is sensing low demand.
The only way I can get the cold radiators warm, is by turning other radiators off. They heat up nicely but as soon as I turn the other radiators on again, they go cool.
So for whatever reason, the pump can't push water far enough out to the furthest radiators. At present we have 3 hot radiators (these ones are on individual 15mm legs fed from a 22mm pipe) and the rest are tepid or cold. There are two other legs, but these each have 2 radiators on....again in 15mm fed from 22mm...in both cases the first radiator in the leg is tepid and the 2nd cold. If I leave the heating on for hours, the cold radiators eventually get tepid.
I'd appreciate it if anyone can suggest where to look next? Logically I'm thinking a blockage somewhere but not sure where to start with that. I've seen suggestions about balancing the radiators however the lockshields and TRVs are fully open on all the radiators and always have been?
Thanks in advance
Andy.
