Hi,
I've been repairing my heating after some frozen pipes and can't seem to get it to circulate properly.
It's an old Baxi back boiler that provides hot water and runs 7 radiators (open system, 8mm copper pipe from just after boiler),
There was a burst in the pipes feeding the boiler and the pump. I've fixed the pipes and replaced the old Grundfos 15-50 pump with a Grundfos 15-60. I took the opportunity to remove all the radiatiors and flush them out (they were VERY dirty with black sludge) and flushed out all the 8mm pipes too, which were also very dirty. Refilled the system, ran for a few hours and flushed again, refilled and roughly balanced the system.
The problem is that when all the radiators are on, none of them get very hot, even though the boiler is getting up to temp (75C). If I just have either the downstairs 4 radiators on or the upstairs 3, I can get these all 'warm', but not hot. Max inlet temp is 45C. It seems to me that there just isn't enough flow as the the boiler quickly reaches working temp and switches off but the radiators have yet to get warm all over? Each radiator run on it's own gets nice and hot all over, but seems to take a very long time (12-15 mins) to completely fill with hot water, which also points me to low flow rate? I added a desludging agent (X400) and will leave it running for a few days to see if things improve. In the mean time, has anyone got any advice, other than replace the system
Another thought just struck me as I pondered the balanced system only being warm... I may be barking up the wrong tree but could it be that the small bore pipe has a greatly reduced ability to retain heat than 15mm pipe due to the smaller volume of water? Whilst investigating this problem I did notice the 8mm pipes are NOT insulated and the downstairs pipes are run in the foundations! Maybe, at the reduced flow rate available using 8mm in an open system, most of the heat is lost (75C from the boiler - 41C into the radiators) before the water even makes it into the radiators and after passing halfway through the rad ALL the heat has been lost? Maybe if I just insulate, then the low flow rate would no longer be a problem?
If you need any more info, please just ask.
Many thanks,
Dave.
I've been repairing my heating after some frozen pipes and can't seem to get it to circulate properly.
It's an old Baxi back boiler that provides hot water and runs 7 radiators (open system, 8mm copper pipe from just after boiler),
There was a burst in the pipes feeding the boiler and the pump. I've fixed the pipes and replaced the old Grundfos 15-50 pump with a Grundfos 15-60. I took the opportunity to remove all the radiatiors and flush them out (they were VERY dirty with black sludge) and flushed out all the 8mm pipes too, which were also very dirty. Refilled the system, ran for a few hours and flushed again, refilled and roughly balanced the system.
The problem is that when all the radiators are on, none of them get very hot, even though the boiler is getting up to temp (75C). If I just have either the downstairs 4 radiators on or the upstairs 3, I can get these all 'warm', but not hot. Max inlet temp is 45C. It seems to me that there just isn't enough flow as the the boiler quickly reaches working temp and switches off but the radiators have yet to get warm all over? Each radiator run on it's own gets nice and hot all over, but seems to take a very long time (12-15 mins) to completely fill with hot water, which also points me to low flow rate? I added a desludging agent (X400) and will leave it running for a few days to see if things improve. In the mean time, has anyone got any advice, other than replace the system
Another thought just struck me as I pondered the balanced system only being warm... I may be barking up the wrong tree but could it be that the small bore pipe has a greatly reduced ability to retain heat than 15mm pipe due to the smaller volume of water? Whilst investigating this problem I did notice the 8mm pipes are NOT insulated and the downstairs pipes are run in the foundations! Maybe, at the reduced flow rate available using 8mm in an open system, most of the heat is lost (75C from the boiler - 41C into the radiators) before the water even makes it into the radiators and after passing halfway through the rad ALL the heat has been lost? Maybe if I just insulate, then the low flow rate would no longer be a problem?
If you need any more info, please just ask.
Many thanks,
Dave.
