Minimum gas working pressure?

[matt-j]

I'm having a new combi fitted (Vaillant EcoTec Plus 831), and i've been advised that i may need to replace the current 22mm pipework from the meter with 28mm, in order to achieve 19mbar working gas pressure at the boiler, under load. It's currently a run of around 6m with three 90 elbows.

The challenge is that the heating engineer has suggested running in 28mm by notching the bottom of my timber joists - and these are only 7" deep. I'm not sure that's a great idea.

So, is this 19mbar pressure a regulatory requirement? and if so, what's the best fix - should I be putting 30mm notches in the bottom of 7" joists?

 

[seco services]

as for your notching in 7" joists.
max notch is 22.5mm
and only notched from the top not bottom of a joist.

 

[matt-j]

as for your notching in 7" joists.
max notch is 22.5mm
and only notched from the top not bottom of a joist.

Thanks, it sounded a bit sub-optimal. Is this in the regs somewhere? I had a look through the Part A pdf, but it didn't seem to mention notching specifically.

 

[burygas]

17mb is ok for vaillant combis !!!!!

 

[matt-j]

17mb is ok for vaillant combis !!!!!

Well to be fair the vaillant spec. says 20mb, so I guess 19 comes from +/-1mb?

 

[doitall]

Depends what else you have on the gas. 6m run with 3 bends will give you 5m³/h and the ecotec plus 831 requires 3.3m³/h

 

[matt-j]

Depends what else you have on the gas. 6m run with 3 bends will give you 5m³/h and the ecotec plus 831 requires 3.3m³/h

I see. There's a four burner hob, and a gas fire. They all tee off from a short section of 28mm off the meter. So, is this a regulatory requirement for sign off, or sensible caution on the engineer's part? I'm not trying to catch him out, just trying to understand what might need to be done, and how best to achieve it ie not bottom notching flooring joists.

 

[doitall]

If the hob and fire tee of the 28mm, and your measurements/information are correct 22mm will be fine.