Worcester Bosch Guarantee Voided?

[Gerry555]

Hi, we're after a new Worcester Bosch combi and have used their site to find accredited fitters in our area. Although we now have a couple of quotes, we're wondering whether what one fitter is proposing will void the manufacturer's guarantee.

Basically, the gas pipe that supplies the existing boiler is too small for a new Worcester combi. Fitter No1 wants to bring a larger diameter pipe up an external wall (two storeys) from the meter downstairs and into our flat. Fitter No 2 informs us that 9 times out of 10 the gas pressure is high enough from smaller pipes to do a conversion/widening at the point where it connects to the new boiler. Only if the pressure isn't high enough would he bring up a new pipe from downstairs.

Keeping the existing, smaller pipe in situ is going to work out cheaper and is our preferred option. However, when we asked Fitter No 1 if he could also do this (providing the gas pressure is there), he said that using the smaller pipe would void the Worcester Bosch warranty. Is this true? Would the warranty be voided? (any Worcester fitters here?)

Also, do fluctuations in gas pressure have a wide spread? If so, I should imagine that using the smaller pipe means more chance of losing pressure. Yes? If that's the case, would this compromise the efficiency of the boiler, or worse still damage it in some way?

Any help appreciated. Thanks.

 

[namsag]

By smaller pipe do you mean 15mm as opposed to 22mm.

 

[snb]

as long as the WP at the boiler is within 1mb of the meter WP then there will be no issue from worcester

 

[corgiman]

as long as the WP at the boiler is within 1mb of the meter WP then there will be no issue from worcester

are you sure as their literature clearly stats that he incoming gas MUST be 22mm diameter minimum.

and they have never given us the lea way on it?

 

[Gerry555]

By smaller pipe do you mean 15mm as opposed to 22mm.

Yes, that's the case.

 

[simond]

CORGI (and Gas Safe) insist that the manufacturers instructions must take precedence.

The Worcester instructions are clear and unambiguous, they require a minimum of a 22mm pipe from the gas meter.

Your chap giving you the cheaper quote is a chancer and should be given the heave ho. He is not capable of self certifying the installation if he has not following the prerequisites.

So to summarise, yes, your warranty will be affected. When you sell the house, the buyer may have the boiler checked and you may have to renew the pipe anyway.

Finally, if the gas pipe can technically deliver the volume of gas needed but the sizing does not meet Worcester's installation mandatory instructions, why not fit a Vaillant? They do not mandate the actual pipe sizing (but the pressure drop still has to be within limits).

 

[bengasman]

The reason WB specifies it MUST be minimum 22 mm, is because 15 mm gives a maximum pipe length of 2 metres if there is one elbow at the meter, one at the boiler, and no other things like a cooker, and the boiler is the smallest in the series. That makes number 1 right.
Chances are that the pipe is 3/4 steel until your kitchen, which would make number 2 right as well.
But if you choose model 42 cdi, and you have a gascooker, and a fire, you would need 28

 

[Gerry555]

Your chap giving you the cheaper quote is a chancer and should be given the heave ho. He is not capable of self certifying the installation if he has not following the prerequisites.

Ironically, he gave the more expensive quote! We were wondering if the other guy could make his quote even cheaper, though. Thanks for answering.

Finally, if the gas pipe can technically deliver the volume of gas needed but the sizing does not meet Worcester's installation mandatory instructions, why not fit a Vaillant? They do not mandate the actual pipe sizing (but the pressure drop still has to be within limits).

You've pre-empted my next question! (I was going to ask if Vaillant would be OK with a 15mm pipe, assuming pressure is OK). Many thanks, again!

 

[doitall]

Sizing a gas pipe isn't guess work

Measure the length, add the number of bends, and you can tell if 15mm is ok or not, which incidentally I doubt very much.

 

[bengasman]

I rarely calcualte, only very long runs with lots of bends.
Over 1 metre = 22
Over 10 metres =28
Over 35 kw = always 28

 

[Gerry555]

Just one more question.

Is gas pressure a problem with combis only, or is it an issue with all types of boiler? Basically, we have a bog-standard, open-vent system and wanted to convert to a combi to free up space in the airing cupboard and loft (tiny flat). If we were to just replace the existing boiler with a new equivalent (non-combi), would we still have the problem with needing a 22mm pipe?

I ask as fitter No1 is really messing us about so we got another quote. Fitter No 3 tells us that pressure isn't going to be enough for a Vaillant, either, so we need a new pipe - existing, 15mm pipe is the best part of 2m long with a couple of shallow bends, by the way. If we were less ambitious with our plans and knocked the combi idea on the head, will we still need the new pipe with another type of boiler?

 

[bengasman]

Gaspipe size/pressure-loss requirement is the same for all appliances.
A heat only boiler can be smaller therefore needing less gas per hour, but I doubt if it will erase the need for a pipe upgrade.
And it brings another problem, you will need a cylinder.
That means either going back in time 50 years and install a disgusting open vent cylinder, or an unvented which will add anything from a thousand pounds upwards.