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.