Worcester 18R1 final leg of pipe size?

[Harry Bloomfield]

Busy seeking quotes for the replacement boiler and one guy quoting over the phone, when I described the layout, was suggesting the pipe from meter to boiler needs be entirely 22mm. Worcester+'s own conditions says he. It is 22mm all the way from meter, to the adjacent oven, then final 2m drops down to 15mm where it goes on to feed our present 18Kw boiler.

We have had no issues due to pressure drop in the 10 years since install, at all. The installer ten years ago was at first insistent a new pipe would need be run from the meter, outside the house to the boiler. I did the pipe calcs and made clear I would not allow him to do that, rather I would go elsewhere. He gave in and reused the existing feed.

The thing is, the branch down from 22mm to 15mm is on the wall, behind units, so swapping the 15mm to 22mm would be no simple task - but is it necessary for a Worcester / Bosch 18R1 18Kw boiler's guarantee?

[Harry Bloomfield]

Jim K laid this down on his screen :

How might I do that?

What is your phone number?

[Harry Bloomfield]

Jim K formulated the question :

The Worcester / Bosch helpline...

...and they say there is no such condition to their boiler being installed, so long as the pressure is maintained above their minimum specified pressure with all appliances in operation. No doubt it will.

[John Rumm]

I have not checked, but I would be surprised if the gas inlet is 22mm on the boiler - so it will have to reduce somewhere!

What other appliances are fed from the same pipe run?

[Brian Gaff]

Is this a wise move on an open usenet group? Brian

[Harry Bloomfield]

Brian Gaff wrote on 26/03/2018 :

No problem, it was Worcester / Bosch's helpline number.

[Harry Bloomfield]

John Rumm wrote on 26/03/2018 :

A 3.5Kw radiant gas fire and a gas oven/ hob, both branched directly off the 22mm run, then the final section of pipe at 15mm feeding the boiler. All as installed originally, except back then, the original boiler was a 32Kw unit and replaced 10 years ago with an 18kw condensing boiler, because much less heat input was needed.

The installer fitting the last boiler, suggested it would need a new pipe installed, on the surface - a long and ugly route around much of the the outside of the house. My pipe calcs at the time suggested that was rubbish and so it proved, because he gave in and used the existing supply which has been absolutely fine for the past 10 years.

Now another installer is suggesting the existing may not be adequate, from my description over the phone and is suggesting Worcester guarantee would be invalidated if the final 15mm pipe were not upgraded. Worcester said, if the pressure was adequate at the boiler, with all in use, then no problem at all.

[John Rumm]

So depending on the peak demand of the cooker, you could have another

1.5m^3 per hour there. That gives just under 20m of 22mm equivalent if you use the whole 1 mBar drop available.

(you probably need to reserve about 0.25 mBar for the 2m run of 15mm)

I have noted in the past that many installers seem to work to a rule of thumb when it comes to pipe sizing rather than actually doing the sums. So if they always suggest upgrading the pipe, then it will usually be more than adequate without needing to think about it.

[Harry Bloomfield]

John Rumm has brought this to us :

A guy called earlier, to look at the job and he agreed with me it was fine as is, unless a large combi were to be installed. The 22mm pipe run at a guess, is around 13 to 15metres, before it drops down to 15mm for the final bit to the boiler.

[ARW]

It's not the Catholic Contraception help line number that he gave out.