I have a Worcester Greenstar 37cdi boiler. The whole system was put in 10 yrs ago, along with new radiators and all new 15m pipes, to replace the old 10m. The boiler has run great for 10years with not one problem or replacement of any parts,( and yes lucky me) The heating still works great, all radiators work as they should, and fully hot over the entire surface area. I drained some water off two of the radiators down stairs today and the water is very clear, you would think it was drinking water. ( the system as been looked after) When turning the hot tap on' the boiler temperature reaches max temperature 90 and locks out like it should due to over heat, water coming out of the tap is not restricted in any way ( full flow) but either warm, hot for a short time or cold. Could anyone tell me if I'm thinking along the right lines that the problem is the DHW plate exchanger ? or is there any other part on the boiler that maybe the problem. many thanks.
We also have a Worcester Bosch, ours is 13 years old , our water started running cold , and we have just had a new heat exchanger fitted. It did not cost us anything under its yearly service.