Why such a huge pressure drop in gas to boiler

[Gary80gas]

Just fitted a Worcester 38cdi. Ive run 15m of 28mm with 9 bends and im getting a 5mb drop from the meter to the boiler. Ive connected to a 22mm union on the meter and stepped up to 28mm, then used a Worcester own top feed kit to feed pipes behind boiler which is about 1.5m of 22mm.
Is my maths wrong. Is it the meter union or the Worcester behind boiler kit.
Any ideas appreciated. Ta.

 

[Gasmk1]

are you testing at the gas valve or a test point on inlet to boiler as the gas valves lose quite a bit

 

[Scott_D]

Cut in a test point below
What are your readings at the meter and the boiler?

 

[sammathias]

What scott said, what's your working pressure at meter? And pressure on gas valve? Ideally you want a test point just before boiler.

 

[Harvest Fields]

As above mate. Put a test point just before the boiler and test again.

 

[ShaunCorbs]

Or allow the specd drop think it's around 4mbar

2.5 through the gas valve 1.5 on the pipe

 

[sammathias]

No less than 18mb at a inlet test point on the Worcester's.

 

[Gary80gas]

The gas meter reads 21mb in engineers mode and im testing 16mb at the inlet pressure on gas valve. Does the 22mm union on the gas meter make a difference?

 

[Harvest Fields]

The gas meter reads 21mb in engineers mode and im testing 16mb at the inlet pressure on gas valve. Does the 22mm union on the gas meter make a difference?

You need to cut a test point into the gas pipe before the gas valve right below the boiler mate. You will find that you probably have 20/19 at this point

 

[Scott_D]

Check for muck or flux in the gas valve

 

[sammathias]

You need to cut a test point into the gas pipe before the gas valve right below the boiler mate. You will find that you probably have 20/19 at this point

Doesn't Worcester stat no less than 18mb at gas valve inlet test point tho?

 

[sammathias]

The gas meter reads 21mb in engineers mode and im testing 16mb at the inlet pressure on gas valve. Does the 22mm union on the gas meter make a difference?

No union won't make a difference...unless it's blocked.

 

[Harvest Fields]

Believe the pressure difference from meter to gas valve is 2.5 mb then a further 1.5mb across the valve is allowed. That is for a 30cdi classic ERP

 

[Darren Jackson]

I've just worked it out & I get, 15m of 28mm with 9 elbows = 0.42 mB Pressure Drop & 1.5 m of 22mm with 1 swept bend = 0.13 mB Pressure Drop. Total PD 0.42 + 0.13 = 0.55 mB PD. from meter to appliance. Well within the maximum allowed 1mB pressure drop on pipework only. What did you work it out to? I bet if you cut in your own test point you will get roughly a 0.5 mB pressure drop, unless you have some debris in your pipework and it is partially blocked.

 

[Gary80gas]

Thanks Darren, my calc was similar 0.42 + 0.16 =0.58. Im going to fit a test point under the boiler. Fingers crossed that will give the right reading.