Hi
First post for me. I have a problem with circulation. My system is a fully pumped vented system with 2 x 2-port valves, 14 rads. The original system was installed some 30 years ago. The boiler was replaced 5 years ago and is a Worcester Bosch Greenstar 30 cdi conventional. All was fine until this autumn when we turned the heating on. It didn't work properly. The rads just got warm, and the boiler heated up rapidly and shut off. The temperature then fell away rapidly until it reached about 30 degrees. Then the boiler would fire up and the sequence would begin again.
The system was under contract, and as luck would have it, or so I thought, the engineer was coming a couple of days later to do the annual service. I told him about the problem, and he said there was nothing wrong with the boiler, and we have a circulation problem. I decided to change the pump. I didn't think there was anything wrong with it, but it was quite old, and I was keen to have an A rated pump so I got a Grundfos Alpha2 15-50. This did not improve matters. I called the company who were contracted to maintain it. Engineer arrived. After some time he recommended a power flush. I arranged this, and when the engineer left after spending all day doing the flush, the boiler was working properly, but as he had left the thermostat at its max, I turned it down to about 5, whereupon the earlier symptoms resumed. I turned the dial back to max and it still behaved badly. It behaves the same way when hot water only is selected.
I drained the system and checked the zone valves. They are ok. The rubber seals on the actuators is ok.
I called the engineer back. Different engineer this time. He said the heat exchanger is blocked and needs to be changed. I called Worcester Bosch. They said I could get this done on a fixed price contract for £325 or if I take out a service contract with them, they would cover it under the terms of the service contract. So I took out the service contract. That was last Friday, and the engineer from Bosch arrived on Monday and replaced the heat exchanger. But guess what - the system is still not heating up properly.
There's no air in the rads or the hot water cylinder. I've changed the pump valves. I've replaced the manual bypass valve with an automatic one. I've probably done a load more things which I haven't documented here. I'm at a loss to know what to do next. I keep coming back to the fact that it worked well last winter (and several winters before that).
If anyone has any suggestions as to what I should do next, please let me know.
Nick
First post for me. I have a problem with circulation. My system is a fully pumped vented system with 2 x 2-port valves, 14 rads. The original system was installed some 30 years ago. The boiler was replaced 5 years ago and is a Worcester Bosch Greenstar 30 cdi conventional. All was fine until this autumn when we turned the heating on. It didn't work properly. The rads just got warm, and the boiler heated up rapidly and shut off. The temperature then fell away rapidly until it reached about 30 degrees. Then the boiler would fire up and the sequence would begin again.
The system was under contract, and as luck would have it, or so I thought, the engineer was coming a couple of days later to do the annual service. I told him about the problem, and he said there was nothing wrong with the boiler, and we have a circulation problem. I decided to change the pump. I didn't think there was anything wrong with it, but it was quite old, and I was keen to have an A rated pump so I got a Grundfos Alpha2 15-50. This did not improve matters. I called the company who were contracted to maintain it. Engineer arrived. After some time he recommended a power flush. I arranged this, and when the engineer left after spending all day doing the flush, the boiler was working properly, but as he had left the thermostat at its max, I turned it down to about 5, whereupon the earlier symptoms resumed. I turned the dial back to max and it still behaved badly. It behaves the same way when hot water only is selected.
I drained the system and checked the zone valves. They are ok. The rubber seals on the actuators is ok.
I called the engineer back. Different engineer this time. He said the heat exchanger is blocked and needs to be changed. I called Worcester Bosch. They said I could get this done on a fixed price contract for £325 or if I take out a service contract with them, they would cover it under the terms of the service contract. So I took out the service contract. That was last Friday, and the engineer from Bosch arrived on Monday and replaced the heat exchanger. But guess what - the system is still not heating up properly.
There's no air in the rads or the hot water cylinder. I've changed the pump valves. I've replaced the manual bypass valve with an automatic one. I've probably done a load more things which I haven't documented here. I'm at a loss to know what to do next. I keep coming back to the fact that it worked well last winter (and several winters before that).
If anyone has any suggestions as to what I should do next, please let me know.
Nick
