Vaillant Ecotec 831 plus - varying hot water temperature

[jamesdean1986]

Before I go and call an engineer…

Had the combi boiler installed around this time last year and all seemed to work fine but we only actually moved into the house this weekend as a result of taking a year renovate it, so never really tested the system properly with a bath or shower, only the occasional bowel of hot water to wash the cups and spoons.

Even though the hot water temperature is set to the max of 65’C there seems to be some variance in the temperature. I was able to fill the bath yesterday whilst sitting in it but other times the water is too hot to hold your hand under. Yesterday the temperature changed midway through my wife having a shower, gradually getting colder (she had been in there about 10 minutes). After this happened I turned the system off/on and the temperature seem to pick back up on it.

Flow seems to be ok.

I'm going to fetch a thermometer to check the temperature but in the meantime any suggestion or things to try?

 

[Bunnyman]

Probably a duff shower mixer , unlikely to be boiler, note, the faulty mixer passes cold water even when it's a hot tap elsewhere being opened

 

[jamesdean1986]

Thanks.
I thought that at first as we had not tested the shower apart from a leak check, but I ran the tap when she had finished and the temperature was low from that.
Also I had a quick shower before her and mine was fine.
I am new to combi boilers, but was under the impression they give unlimited continuous hot water. If for example it had been running constantly for 15 minutes or so, would it go into some sort of cool down mode from getting to hot?

 

[wannocks]

Only if there's something wrong with it!

 

[jamesdean1986]

Vaillant engineer came yesterday.

Turns out there is a blockage somewhere in the pipe between the meter and the boiler.

He could not be 100% certain that this was the cause, but considering the pressure drops from 22 down to 5 when the boiler fires up, and it should go no lower than 16.... I think there is a good chance this might be the cause. He was quite surprised the boiler does not display it as a fault.