In ,
John typed:
"pauly" wrote in message
...
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?

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

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?
http://tinyurl.com/3sq4a (its an image on worcester-bosch.co.uk)

Paul