Gas Hob pipe dia

[cumbriasteve]

Just bought a new hob and when checking the old one so I could tell the installer details I noticed the feed was 15mm with the last metre 10mm to the hob, was always suspicious of the gas flow not being what I expected....but may be wrong.

I mentioned this to him and got a "yeah mate 10mm is fine".

Googling suggests 10mm may not be sufficient even just for a hob where the oven is electric, anyone know or had similar tales on a kitchen fit.

Obviously I will be using a gas safe guy but being registered gas safe does not mean all installers work to a high or even correct standard, it would not be dangerous but I don't want poor gas feed.

Just interested if anyone has heard similar tales.

 

[daedalusminos]

Surely the hob inlet is sized according to flow rate, therefore the pipework should be sized accordingly?

 

[lshigham]

What output is the new one and how long is the run?

 

[cumbriasteve]

What output is the new one and how long is the run?

Total of the four is 8 kw and 15m pipe is about 2metres across the kitchen, connecting with 1 mtr of 10mm.

 

[cumbriasteve]

Surely the hob inlet is sized according to flow rate, therefore the pipework should be sized accordingly?

I would agree but the tale was...if there is no gas oven the pipe can be reduced to 10mm.

 

[Mikes]

Steve,
With all things gas, the other critical item is the distance that the connection is away from the meter. You are meant to have no more than 1 mbar pressure drop between the meter outlet and the appliance inlet when it is operating. This also needs to take into account any other appliances that are drawing gas from the same pipe. The 1 mbar pressure drop applies to each item of equipment. With a hob, gas fire etc, it is not uncommon for the inlet connection to be 10 mm but this does not mean that all of the pipe serving it should also be 10 mm. Normally the distribution pipe will be much larger and only reduce to 10 mm for the final connection. If you want, I can calculate the pipe size for you. I would need to know the distance from the meter, number of bends, Appliance connected load in kW or the manufacturer's stated gas flow rate.
Many houses have undersized gas distribution as a lot of 'professional' installers only ever rely on the pressure at the appliance being equal to or above the manufacturer's stated minimum inlet pressure and don't comply with the 1 mbar pressure drop requirement.
Hope this helps.

Mike.

 

[cumbriasteve]

That makes sense Mike, hence the 15mm to the location and only 10mm for the connection by the looks of it.

 

[cumbriasteve]

Thanks for the input folks... offline for a while now... Grandson will be demanding I play Nintendo switch soon.

 

[Kayos]

I usually do last metre in 10mm for ease of feeding behind and through units