New combi has lower pressure than old one....

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toxster

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Yesterday had a new combi fitted (Worcester Greenstar 24i Junior). Shower pressure is unacceptably low and certainly lower than the old glow worm 75e boiler.

Only change I can see is that because the fitter couldn't find the house stopcock he sliced the cold inlet to the boiler and put an isolation valve on.

Now I've seen some posts suggesting that this arrangement may drop the bore from 22mm to 15mm (internally), though no definitive answer.

Question therefore: Would it be recommended to ask (he comes back today) for him to fit a gate valve instead or might something else (also?) be causing this?

NB cold inlet pressure is fine across the house (unchanged).

Any help much appreciated.

Thanks.
 
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24i is just about the cheapest boiler they make, so it would not be reasonable to expect great performance.
At the same time, they are also one of the favourites of cowboys, which could be another reason why things are not working too well.
Is this guy really corgi registered?
Did you see his corgi card with his photo and a six-digit number on it?
If he does have a card, but it has fewer than 6 digits in the number, he is probably not registered himself, but using a company number, in which case the installation would be illegal
 
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Yes he's corgi.

He needs to come back today to complete the guarantee card and fit a trv also he wants to tidy up and do something else.
 
Don't expect more than about 9.5 l/min from the new WB.

If you have good mains flow and pressure, one wonders why you didn't go for a 30/31 Kw combi instead :confused:
 
probably one of the two reasons people get a 24i; either take the cheapest of 20 quotes, or because they are ripped off.
 
Based on property size etc the 24 was the rec. boiler by Worcester.

The 24 has the same flow rate as the scaled-up decade old combi so it's reasonable to expect a similar, or better, flow rate to the shower head. The 24 was chosen over the 27 as it fits the space exactly.

Powerflush was done - took a full day.
 
Dan_Robinson said:
and your flow rate is?

Pressure by definition would be the same.
Click to expand...

We're probably in danger of talking too techie for me.

The book says 9.8l/min - the old one was 9.4. Have I made an error in deducing that this would equate to similar/better shower pressure?
 
Ok - he's here now for a while to some cementing round the flue.

He says the main coming into the house is 16mm and the valve he's fitted takes it to 11mm! Is he making sense?

Also - measured the flow from the bathroom tap. I'm getting 7.8 litres in one minute. Input temperature is 8 degrees c, output is 45....
 
You temperature rise is below spec, which on a new boiler could mean an undersized gas pipe.

Ask him to confirm the dynamic pressure, and remember to check his CORGI card.

Changing the service valve would possibly help the flow rate, but your temperature might actually go down.
 
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