I know there have been loads of posts about this sort of problem before, but please bear with me.
My house has a 40-year old open vented system with an oil-fired boiler. It has a gravity circuit for the hot water controlled with a 2-port valve and a thermostat on the HW cylinder. The central heating is on a separate circuit from the boiler, on a ‘one-pipe’ arrangement with a pump and serves a total of 13 radiators and a length of strip/skirting heating. It has worked well for years and no significant alterations have recently been done.
Earlier in the year I had been having problems with the HW cylinder that wasn’t heating properly. Back in June I disconnected the feed and return from the HW cylinder coil, hooked up a couple of hoses and flushed it out with water from the bath tap. This seemed to cure it and assuming that sludge was to blame, when I re-filled the system I put some sludge cleaner in.
Recently when I started to use the central heating, I realised that the small feed and expansion tank was filling with warm water and over-flowing. The sludge cleaner had been in for about 4 months by now and so was long over-due for removal. I therefore drained the system hoping this might sort things out. Not much sludge came out, just plenty of brown water. I re-filled, but didn’t use any inhibitor because I wanted to be confident it was working OK.
The tank is still over-flowing though. There also seems to be a lot of air getting into the radiators. I bleed them all down and it behaves for a day or two, but then the gurgling noises start and the over-flow begins to run again. It only happens when the central heating is on. Once the pump is turned off it immediately stops overflowing and the level in the tank drops about 4 or 5 inches (due to cooling of the water?). The water level in the F & E tank is lower than the cold water tank and because the F & E tank is not overflowing all the time I am assuming that the HW cylinder coil is still OK.
A blockage somewhere would seem like the other cause, but the system filled up OK after draining down and once the radiators have been bled they all get warm, so there must be reasonable circulation of water. I’m at a loss to think what’s going wrong. Do you guys have any suggestions?
My house has a 40-year old open vented system with an oil-fired boiler. It has a gravity circuit for the hot water controlled with a 2-port valve and a thermostat on the HW cylinder. The central heating is on a separate circuit from the boiler, on a ‘one-pipe’ arrangement with a pump and serves a total of 13 radiators and a length of strip/skirting heating. It has worked well for years and no significant alterations have recently been done.
Earlier in the year I had been having problems with the HW cylinder that wasn’t heating properly. Back in June I disconnected the feed and return from the HW cylinder coil, hooked up a couple of hoses and flushed it out with water from the bath tap. This seemed to cure it and assuming that sludge was to blame, when I re-filled the system I put some sludge cleaner in.
Recently when I started to use the central heating, I realised that the small feed and expansion tank was filling with warm water and over-flowing. The sludge cleaner had been in for about 4 months by now and so was long over-due for removal. I therefore drained the system hoping this might sort things out. Not much sludge came out, just plenty of brown water. I re-filled, but didn’t use any inhibitor because I wanted to be confident it was working OK.
The tank is still over-flowing though. There also seems to be a lot of air getting into the radiators. I bleed them all down and it behaves for a day or two, but then the gurgling noises start and the over-flow begins to run again. It only happens when the central heating is on. Once the pump is turned off it immediately stops overflowing and the level in the tank drops about 4 or 5 inches (due to cooling of the water?). The water level in the F & E tank is lower than the cold water tank and because the F & E tank is not overflowing all the time I am assuming that the HW cylinder coil is still OK.
A blockage somewhere would seem like the other cause, but the system filled up OK after draining down and once the radiators have been bled they all get warm, so there must be reasonable circulation of water. I’m at a loss to think what’s going wrong. Do you guys have any suggestions?
