Gas pipe size

[gigz]

At work yesterday installing a ravenheat csi 85t combi (i was changing the rad valves) the (older) gasfitter could'nt get to the 22mm gas pipe (on the other side of a dwarf wall) but could see it. Now on these boilers you are allowed 3m including bends etc of 15mm gas pipe to the boiler so he connected a 15mm to 22mm reducer to the exsisting gas main (leaving approx 2 feet of 15mm) then proceeded to take 22mm to approx 4 inches away from the boiler. When commisioning all was fine with the gas pressures (inlet pressure 20mb burner pressure 10.5 mb). I would have thought this was wrong(and told him) but he just said as long as the pressures are ok it does'nt matter. What do you guys think of that then

 

[2face]

dodgy do as the book says .. 22 to boiler .. reduce on run up ..

 

[gigz]

Thats what i thought, he said a lot of installers do this and if readings are correct theres no problem.

 

[fitz1]

approached corgi with similar type problem , they were unsure but said as long as the pressures were right then should be o.k.not ideal but in extreme circumstances.

 

[chrishutt]

It doesn't make any difference where in the run the reduced pipe size is, providing the overall pressure drop is within acceptable limits - i.e. 1 mbar. A metre of 15mm tube has the same resistance to the flow of gas whether it's at the beginning, middle or end of a run. However the beginning of a run is more likely to be shared with other appliances in which case they would also be affected.

 

[kevplumb]

if you don't know how to size your pipework yer shouldn't be let loose

 

[gigz]

if you don't know how to size your pipework yer shouldn't be let loose


I do know how to size pipework, i just thought this practice was wrong obviously not

 

[kevplumb]

so read chrishutts reply