Search the forum,

Discuss Pressure loss through the pipework in the Plumbing Jobs | The Job-board area at PlumbersForums.net

Status
Not open for further replies.

markadams

Plumbers Arms member
Plumber
Gas Engineer
Messages
360
I have recently read a couple of posts on here that specify that the pressure loss from the meter to the applicate can be a max on 1.5 mbar.

I always understood it to be 1.0 mbar. Has it changed without my knowledge? I am due to resit my assessment soon so it was a while ago.

Mark.
 
1mb as far as I know
Then losses through boiler and gas valve as per MIs
 
Last edited:
From gas valve test port some 1.5 some 4.5 mbar
 
Can you explain further Shaun? I too am re-taking my ACS in a couple of months & I always thought it was 1 mbar drop from governor to appliance.

Depends where you take it from if there's a test point before the gas valve e.g. On the gas ISO valve then it is ,

But if your testing on the gas valve manufacturer instructions will tell you the drop Worcester are 1.5 and I think vaillint are 4.5

Understand?
 
Well it seems that it is not the case on the Ideal boilers, if taking a reading at the isolation valve test point then you can allow a higher loss based on the KW rating (as per the MI)
 
if you take the reading from the isolation valve there should be max 1mb loss if from the gas valve some manufacturers allow a bigger loss
 
Well it seems that it is not the case on the Ideal boilers, if taking a reading at the isolation valve test point then you can allow a higher loss based on the KW rating (as per the MI)

Why if it's straight through valve ? Be the same as cutting a test point below the boiler
 
Depends where you take it from if there's a test point before the gas valve e.g. On the gas ISO valve then it is ,

But if your testing on the gas valve manufacturer instructions will tell you the drop Worcester are 1.5 and I think vaillint are 4.5

Understand?

Yes mate I understand. I did mean from meter to test point before appliance is -1mbar max. I know at valve or inlet it varies with mi's. So nothing changed there then in the last 5yrs & I can relax. Thanks for elaborating anyway Shaun.
 
It's clear in training and on your ACS, it's a maximum of 1 mb from the meter to the appliance. This refers to the installation (pipework) nothing else.
 
Agree with Rory. The 1mb drop in wp from meter to pipework exit point is as per British standard whatever number. The BS is not concerned with appliance gas valves/test points etc..
 
Just reading this at our college we were doing standing pressure at the gas meter and working pressure at the meter too. Not at the appliance test point. To see if it was within the 1mb limit.
 
I have recently read a couple of posts on here that specify that the pressure loss from the meter to the applicate can be a max on 1.5 mbar.

I always understood it to be 1.0 mbar. Has it changed without my knowledge? I am due to resit my assessment soon so it was a while ago.

Mark.


The reason for the 1mb drop is because there are unregulated appliances in domestic installations in the UK.
e.g. gas fires, cookers, wall heaters etc.
The inlet WP at appliances (since Nat gas ) has been 20 mb.
In order to give that inlet pressure at appliances, the WP at meter outlets in domestic premises has been set at 21. The correct pipe sizing ensures that the pressure is correct at the appliance ( hence 1 mb drop).
Is this making sense?

Some modern Boilers have a bigger ( ish) drop through the internal pipework on the appliance to the gas valve. So it may appear the drop is 3 or 4 mb from meter to appliance but if you had a test point beneath the boiler in the pipework you would more than likely find you actually have a 1-2 mb drop (As long as your pipe sizing is good).

Bottom line is, as long as you pipe size correctly and the working pressure on one appliance is not greatly effected by another it should be fine.

You should calculate pipe sizes to give the 1 mb drop to each appliance as you’ve always done.

I hope this doesn’t sound too waffling.?

If it does say so and I’ll try again.
 
Status
Not open for further replies.

Reply to Pressure loss through the pipework in the Plumbing Jobs | The Job-board area at PlumbersForums.net

Creating content since 2001. Untold Media.

OFFICIAL SPONSORS

OFFICIAL SPONSORS

Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock