Okay, so my boiler kettles fairly badly once it reaches a moderate temperature even under conditions that are allowing good flow rates. Having resolved the system air ingress, let's move on.
The Netaheat Profile (later rebranded simply as the Profile) has a cast-iron heat exchanger. It has been run with Sentinel inhibitor for around the last 10 years but has had air ingress issues, and various amateur (and poor-quality professional) work has been carried out to the system at times, which may mean that there is limescale in the heat exchanger.
The system has a magnaclean on it for the last couple of years. It seems to be picking up more sludge than flakey rust particles, but pickup now seems to have tailed off.
I have tried the Adey MC3 cleanser as someone on here suggested, which did nothing whatever.
System water quality isn't terrible, with a glass drawn from the lowest point being almost free from debris and a lighter yellow than white wine.
The boiler has two top pipe connexions (not sure if the H.Ex. contains a dip tube or not - probably not, as the boiler was, for a time, installed with reversed flow and return (!) and worked well, albeit it ran about 10°C above the correct temperature due to the stat being on what should have been the flow pipe).
I have in the past tried draining the system via the boiler drain cap while the boiler was out of use awaiting a part, and didn't get an awful lot of of it. There are no flow issues within the system, with all the radiators heating up normally and without any indication of sludge problems.
Obviously, whenever the system has been drained, it is likely than some dirt will have been pushed the boiler's way, as the boiler is lower than the upstairs radiators.
As my gas usage is very low, I intend to keep the boiler.
Worth flushing, in case it's limescale mixed with magnetite forming a solid block in the boiler? Is it better to flush boiler and system separately to ensure system dirt does not enter boiler, or is powerflushing as good as it's supposed to be.
Bit sceptical about efficacy of powerflushing, having flushed the same system (elsewhere) two years in a row, using a Kamco flusher and Kamco magnetic filter unit, radiator SDS vibration tool, and acid flusher, neutralised etc. etc. all to Kamco guidelines (did the job properly), and got almost as much out the second time as the first time. This makes me wonder how much dirt is actually removed, particularly in a boiler which has a large area (hence lower flow speed than pipework) and (unlike a radiator) can't really be agitated.
Or is it more likely to be caused by corrosion of the H Ex? In which case, flushing won't help?
Weirdly, I once worked on a system which had a Houswarmer S boiler running on a semi-gravity Primatic system (so no inhibitor at all) and used to bang loudly. The kettling stopped completely after a gravity flush (i.e. a few drain downs and refill).
The Netaheat Profile (later rebranded simply as the Profile) has a cast-iron heat exchanger. It has been run with Sentinel inhibitor for around the last 10 years but has had air ingress issues, and various amateur (and poor-quality professional) work has been carried out to the system at times, which may mean that there is limescale in the heat exchanger.
The system has a magnaclean on it for the last couple of years. It seems to be picking up more sludge than flakey rust particles, but pickup now seems to have tailed off.
I have tried the Adey MC3 cleanser as someone on here suggested, which did nothing whatever.
System water quality isn't terrible, with a glass drawn from the lowest point being almost free from debris and a lighter yellow than white wine.
The boiler has two top pipe connexions (not sure if the H.Ex. contains a dip tube or not - probably not, as the boiler was, for a time, installed with reversed flow and return (!) and worked well, albeit it ran about 10°C above the correct temperature due to the stat being on what should have been the flow pipe).
I have in the past tried draining the system via the boiler drain cap while the boiler was out of use awaiting a part, and didn't get an awful lot of of it. There are no flow issues within the system, with all the radiators heating up normally and without any indication of sludge problems.
Obviously, whenever the system has been drained, it is likely than some dirt will have been pushed the boiler's way, as the boiler is lower than the upstairs radiators.
As my gas usage is very low, I intend to keep the boiler.
Worth flushing, in case it's limescale mixed with magnetite forming a solid block in the boiler? Is it better to flush boiler and system separately to ensure system dirt does not enter boiler, or is powerflushing as good as it's supposed to be.
Bit sceptical about efficacy of powerflushing, having flushed the same system (elsewhere) two years in a row, using a Kamco flusher and Kamco magnetic filter unit, radiator SDS vibration tool, and acid flusher, neutralised etc. etc. all to Kamco guidelines (did the job properly), and got almost as much out the second time as the first time. This makes me wonder how much dirt is actually removed, particularly in a boiler which has a large area (hence lower flow speed than pipework) and (unlike a radiator) can't really be agitated.
Or is it more likely to be caused by corrosion of the H Ex? In which case, flushing won't help?
Weirdly, I once worked on a system which had a Houswarmer S boiler running on a semi-gravity Primatic system (so no inhibitor at all) and used to bang loudly. The kettling stopped completely after a gravity flush (i.e. a few drain downs and refill).
