fluctuating water temp on new combi

[pauly]

Not really a DIY question however this is the most appropriate group i can find.

I just had a new combi boiler fitted to replace an old system with boiler and immersion. Problem is the water temperature varies quite a lot - sometimes its blazing hot and give it a minute and it goes cold before getting too hot again.

The guy who fitted it is really good (reputation) and am trusting him to figure it out however i've got curious as to what it could be.

What could be the cause?

fwiw my house is a 3 bed semi 30 years old and no water supply problems that i've noticed. New boiler is a Worcester.

Thanks

Paul

[John]

various things but as a starter can you quote the commissioning figures he has filled in for model number, water temperatures, flow rates, gas rate etc on your little blue benchmark book that came with the boiler

[a]

I must say I have found our worcester combi a bit more awkard than having a hot water cylinder. I find you cant really have the hot taps on just a little as you need a certain flow before the boiler kicks in (so the water stays cold), opening it a bit more and the boiler kicks in and the water becomes mad hot, only when the tap is open about half way (a ceramic tap) do I get a nice hot temperature that doesnt scold my hands! I cant say I have had the constant hot-cold-hot... with a constant flow.

[Paul]

I haven't seen the book you mention yet. Do you mean figures obtained after testing or manufacturer figures for that particular boiler? The Model is a Worcester 28i Junior.... is this table any use?

(its an image on worcester-bosch.co.uk)

Paul

[Mathew J. Newton]

Which model have you got? You could always turn the DHW temperature down on your boiler (assuming it's got one)!

[a]

we have the Junior 24i I think. Is there any adjustment possible on the flow rate needed to fire up the boiler?

[Stuart Noble]

I've got one of those, and a right pain in the arse it is too. If you find a way to get it to fire up without delivering a gallon of cold water first, I'd love to hear about it.