Low Inlet Pressure

[Danv44444]

Hi Guys,

I went to service a Worcester Greenstar 37cdi combi boiler for a customer today and I checked the inlet pressure on the boiler whilst running in chimney sweep mode. The Inlet pressure was only 15mb and I checked the mi's and it says the boiler should'nt be commissioned if the pressure is less that 18mb. The boiler seems to be working fine and the anaylser readings are ok but I have capped of the gas supply to the boiler for now as im not sure how to catergorise it? Is it At Risk? Are the in any danger if they continue to use it? There is a 22mm gas supply to the boiler probably about 16m with bends etc included.The property is empty at the moment and the customer wants to let it out. Any ideas guys, is the only answer to install 28mm gas pipe?

Thanks Guys

 

[glenno1]

Did you check burner pressure

 

[Danv44444]

No i didnt, would that help?

 

[EPH]

They'll work down to just below 14 I think but it's NTCS if it's working ok I believe.

They need a lot of gas, try to get as much upgraded to 28mm from the meter as possible.

Any other appliances between meter and the boiler?

 

[mikegas]

Did you gas rate it?

 

[snowhead]

What was the Standing pressure?
What was the Operating pressure measured at the meter?

 

[mfgs]

If it is not affecting the operation of the boiler i.e fga reading ok, gas rate ok then it is NCS. Make sure it isnt affecting any other appliances like a hob without a fsd or a gas fire.

 

[EPH]

Did you check burner pressure

Why do you need to do that?

 

[Destroyer2813]

Did you check burner pressure

You cant on the new Wb only the inlet pressure

 

[Danv44444]

Thanks very much for your responses guys. The trouble is the gas supply comes straight off the meter and goes in side the wall somewhere? The also have a decorative gas fire in the front room. I tried running that full rate and the boiler full rate and it still works fine.
I was wondering if it was safe to use because it might not burn correctly? but the fga says its all ok and its a room sealed appliance. I am reasonable new to gas work and I just wasnt sure so i am just wondering if you guys have come across this before.

 

[Danv44444]

The gas rate was totally fine too. It was 35.8kw

 

[EPH]

If its ok at full rate with the fire on max then just make a NTCS note on the certificate.

Especially as your FGA is saying the same, input rating just to go belt and braces but it's not in common when people upgrade boilers with little regard for a good job.

 

[Simon F]

with the two appliances working at full rate did you check the burner pressure at the fire?
as already asked what was the working pressure at the meter?
if that was low you need to call out national grid

 

[GrahamM]

Reference TB 115 & GIUSP.

If low IP is not affecting gas rate and FGA readings then as mentioned it only NCS.

 

[breakdown]

If the pipework is undersized the fga readings are usually out.The inlet pressure for a wb 30 si minimum is 16.5mbar.

 

[Danv44444]

I havent checked the pressures at the meter or the fire but i will when I go back to re connect the boiler. If the are both ok and I do a ncs ticket will that be ok?

 

[EPH]

Yes mate, make a note on the service record you give too.

 

[Danv44444]

How do you thank people for there posts?

 

[Danv44444]

Thanks very much to all of you for your help. :waving:

 

[Simon F]

How do you thank people for there posts?

press the button that says thanks on the left side of the strip at the bottom of the post.
I think if your on a phone it might not be possible.

 

[AWheating]

If the pipework is undersized the fga readings are usually out.The inlet pressure for a wb 30 si minimum is 16.5mbar.

i have fitted quite alot of worcesters and still have not come across one that has a 1.5mb internal drop, i still seem to be able to get less than 1mb from meter to gas valve inlet test point.

do many of you find the same or am i just lucky??

 

[EPH]

i have fitted quite alot of worcesters and still have not come across one that has a 1.5mb internal drop, i still seem to be able to get less than 1mb from meter to gas valve inlet test point.

do many of you find the same or am i just lucky??

I go to loads of gas safety Certs and probably 10% have the right drop or within MI's.

 

[Mike Jackson]

I've had a couple but usually where they are on a seriously long gas run with lots of 28 or even 35.

To the OP, checking the inlet pressure at the appliance is completely meaningless without checking the working pressure at the meter. The requirement is for a maximum 1 mbar drop across the pipework, if you don't know what pressure it starts at you can't tell if the problem is the pipe size or the meter regulator.

 

[Destroyer2813]

i have fitted quite alot of worcesters and still have not come across one that has a 1.5mb internal drop, i still seem to be able to get less than 1mb from meter to gas valve inlet test point.

do many of you find the same or am i just lucky??

Not lucky must just be pipe sizing correctly

 

[EPH]

But the MI's do say min 18mbar in his defence.

 

[AWheating]

Not lucky must just be pipe sizing correctly

i normally run straight off the meter with 28mm as standard practice unless boiler is only 5m away on my own boiler installs. But i have seen it with pipe run on the limits shall we say and still less than 1mb from meter to valve. Makes me wonder what this 1.5mb lose is all about, i must just be lucky then i guess.

 

[Destroyer2813]

U order up a 28mm union or 22 with22-28 red soldered up on it

 

[Danv44444]

So if the pressures right at the meter and wrong at the appliance then the pipeworks undersized? if there both wrong then its the govener?

 

[Danv44444]

U order up a 28mm union or 22 with22-28 red soldered up on it[/QUOTE
Is there much difference in using a 28mm union or a 22mm union with 28mm reducer?

 

[AWheating]

So if the pressures right at the meter and wrong at the appliance then the pipeworks undersized? if there both wrong then its the govener?

meter wp should be 21mb +- 2mb, and then 1mb drop to the appliance. tho some boilers can have a pressure loss between its iso valve and test nipple which can be taken into account.

 

[AWheating]

U order up a 28mm union or 22 with22-28 red soldered up on it

i use a 22mm tail cus i get em for free. 🙂

the difference is not great.

 

[AWheating]

U order up a 28mm union or 22 with22-28 red soldered up on it[/QUOTE
Is there much difference in using a 28mm union or a 22mm union with 28mm reducer?

slight i guess, but gas is not restricted like water so wont make much of a difference overall.

 

[buckley plumb]

thats a big boiler to run on 22mm with a fire aswell . when doing terrace houses now i am fitting 28mm from meter at front of house and part way across front bedroom then 22m to feed 30kw boiler and cooker .

ant

 

[bright spark]

I'd go with snowhead. Check the standing pressure and working pressure at the meter. If its only 15mbar working pressure leaving the meter get gas supplier round as there a prob with meter. If the pressure is fine, around 20mb then the gas supply pipe is too small. Or there could be a slight blockage in the pipe. Could take out the filter on boiler gas valve incase there is dirt in it. Has been known to happen.