Hot water affects gas pressure

[aimber]

I have recently had a new Vaillant Combi boiler fitted and now, when the hot water is running in the kitchen, I have noticed that the flames on the cooker shrink dramatically, returning to normal when the hot water is turned off. I assume this is to do with gas pressure.

Is this normal? If not what is wrong and what can be done to remedy it?

Thanks

 

[gas4you]

No it is not normal

It shows that the gas pipe from your meter to the combi and cooker is too small.

The installer should have calculated the m3/hr needed for all your gas appliances when on together and upgraded you gas pipe accordingly.

Basic stuff for a competent RGI

 

[ollski]

Phone the fitter back up and ask why your gas pipe is undersized

 

[giblets]

Phone the fitter back up and ask why your gas pipe is undersized

And if he tries to blag his way out of it threaten to call CORGI (assuming he is CORGI registered of course )

 

[aimber]

Combi is in the loft (new location) while cooker is obviously unmoved - are you saying the new pipe to the boiler is the one that is undersized?

 

[Paul Barker]

the boiler has a compressor which draws gas out of the pipe via the zero gosvenor gas valve if there isn't sufficient supply of gas in extreme circumstances it could suck the flame out of the hob altogether.

Which is why manufacturers of zero gosvenor appliances specify adequate gas pipe sizing.

 

[Onetap]

Combi is in the loft (new location) while cooker is obviously unmoved - are you saying the new pipe to the boiler is the one that is undersized?

Probably; the installer is responsible for ensuring the installation is adequately sized after he has amended it.

So, if he connected the new boiler pipe to a tee off an existing gas pipe, then the existing pipe from meter to tee may then be undersized to handle the gas required by boiler and cooker simultaneously, even though it was adequate in the old installation. The new pipe to the boiler could be correctly sized. This sounds convoluted, but it is quite likely if he has connected the new boiler pipe to the tee that had served the old boiler.
It is the installer's responsibility to do the maths.

It might also be a defective governor on the meter, so he's not yet proven guilty.

........ in extreme circumstances it could suck the flame out of the hob altogether.

In other words, the flames on some or all of the cooker burners could be extinguished by drawing off hot water in the bathroom. When the hot water draw-off stops, gas would be spilling from the unlit and unattended burners.

 

[scatmanjohn]

Well...was he CORGI registered or not?

My money is on ...Not.

 

[aimber]

Well...was he CORGI registered or not?

My money is on ...Not.

No - definitely CORGI registered, he signed the boiler guarantee off with his CORGI number and I've since had a Building Regulations compliance certificate through from CORGI.

 

[gigz]

Either way you want him back to check pipe size and governor to see where the fault lies. Dont want to alarm you but it is potentially dangerous.

 

[scatmanjohn]

Well...was he CORGI registered or not?

My money is on ...Not.

No - definitely CORGI registered, he signed the boiler guarantee off with his CORGI number and I've since had a Building Regulations compliance certificate through from CORGI.

Well he has been a naughty boy then tut tut.

Have you not already asked him about it?