Central Heating

Boiler short cycling

Anonymous user 28 February 2024 - 3.35 PM

Hi there. My gas boiler (Viessmann Vitodens 100-W) started short cycling one morning, fires up for about 5-10 seconds and then cuts out, waits about 30 seconds and then does the same. Our radiators are getting barely luke warm, and it does the same for hot water. We had a plumber in who identified a fault with the motorised valve and circuit board so replaced these, but still didn't resolve the short cycling problem. He has tried a new pump (not this) and says the boiler is working properly and that it's definitely a circulation issue. So, he thinks the only option is to power flush the system because there must be some debris or sludge that is causing the boiler to cut out. My concern is that its going to cost rather a lot of money and we have no guarantee it's going to work! The whole central heating system and boiler is only 5 years old. I just wondered if anyone had any other ideas before we spend another £500 on top of the £500 of man hours already spent! I am not sure if he's checked for debris//grit in the boiler itself - can this be cleaned without a power flush? Many thanks in advance