heating help

[hollinhurst84]

Before I take a hammer to it
So had issue in December, heating person comes out, fits a shiny new thermostat, cleans diverter valve and says I may need a new one at some point. Fine, all sorted. Hot water is hot, happy thermostat

This week. And back to exactly the same problem
Shiny new thermostat is set to come on for hour in the morning, two hours at night. Target temp in between is 5c (so basically not coming on)
2am, boiler kicks in so I check thermostat which is bleating "target temp 5c" but yet radiators boiling hot, and my hot water barely tepid

I want my hot water hot and my radiators cold (I like a cold house!!!)
But it's randomly kicking in constantly despite the thermostat forlornly saying "5c please" and when it's doing that the hot (ha!) water is resembling fridge temperature

Ideas? Obviously I have rung the heating company but am awaiting someone to come out, and they say the thermostat is the only thing that triggers the boiler

[hollinhurst84]

Oh and it's a combi boiler, and thermostat is barely 2 months old

[Spanglecrab]

Most combis have a pre-heat function for the hot water. The boiler will kick in sporadically to keep a few litres of water ready to use inside the a

[Spanglecrab]

(Posted too soon) appliance.

It sounds like the diverter valve is allowing heat to pass to the heating circuit during the pre-heat.

I'm a bit cynical about someone saying they cleaned a diverter valve. Which boiler do you have?

[hollinhurst84]

Ideal Isar HE24 it says on it
He said at the time it was sticking. Just got a quote for a new diverter valve

[Spanglecrab]

terrible boilers sort op have some and

[Spanglecrab]

Sorry rather than sort

[hollinhurst84]

You mean the actual boiler is crap? I figured it was... New build property!

[etttvatre]

If the cylinder is calling it will switch the boiler on and the diverter valve should divert the water from the heating circuit to the cylinder.

It sounds as if the diverter valve is sticking as he is suggesting, it is not switching to divert the hot water to the cylinder as it should, and instead keeps firing it out to the heating circuit.

[hollinhurst84]

They don't know which valve it is as in apparently there's three types for that boiler and they need to check which one
Looking at between 200-260 for the part then 3-4 hours labour
I've switched the boiler off to stop it from keep kicking in and will just put it on for hot (ha!) water for now

[Spanglecrab]

I should also mention that on this model if a tiny bit of water is running from a hot tap the boiler will fire up. So check you have no dripping taps etc

[hollinhurst84]

Nope def none dripping. My dad heard the price and muttered something about ringing a "mate"
But then he also said the shower temp was "acceptable" when the army would balk at showering in it
So I'm waiting to hear what he says. If I can source the part and they will fit it then it could work out cheaper

[etttvatre]

Ignore my advice, looked at the manual and it doesn't work the way I thought it did.