Vitodens 100 - Powerful enough

[rtukuk]

I've tested it a little furtehr following everyone's advice and found:

If I turn the boiler up so it's heating to about 70c and reduce the temp gauage on the tank (down to say 50c, it clicked on the way) after about 2 hours I noticed that both the pipes going in to the side (top and bootom) were both still hot and the temperature on the tank was about 70c. I know this as when I was moving the temp gauage back on the tank I moved it up to see what temp was it clicked out at.

Does this mean that the 3 port valve might not be working correctly and giving too much hot water to the boiler rather than the rads? It is an original valve and I've notice the rads occasionally get slightly warm in summer when only the hot water is on too.

I assume it will be a fairly quick cheap job for a heating engineer to replace this?

 

[JohnD]

yes

the valve is probably worn and leaking hot water to the cylinder when it should be shut off, allowing the flow to bypass the radiators. It could also be an electrical fault, but a competent engineer will easily check that.

the system will need bunging or draining to change the valve, as it is a water part, so not a 10-minute job. The more modern ones have a removable motor head so you can change the top without having to change the bottom.

have a look at the water and the removed part for traces of sediment (usually black, might be brown)

look in your F&E tank to see if it has mud in it. If so, bale it out and sponge it clean before any draining is done. You don't want to wash extra dirt into the system.