Trainee gas questions in this thread ONLY please

[bassmonster]

what physical components differentiates between a zero governor and another type?

 

[acecharly]

You have a zero governor and a constant pressure governor.

In a constant pressure governor the spring inside acts downwards on the diaphragm.

In a zero governor the spring holds the diaphragm against its seating.

 

[bassmonster]

can you tell which is which just by looking at the gas valve?

 

[acecharly]

If your familiar with the boiler in question yes. If not a quick test with your gauge will tell you.

 

[Killy Bing]

if its a premix burner it will have a zero governor

 

[AWheating]

[DLMURL]http://www.radmidlands.co.uk/Downloads/ControlsDom.pdf[/DLMURL]

page 6

https://docs.google.com/file/d/0B6zTTicYyEudZnhHUVlSRnI5cVk/edit

another good source of info for guys learning the trade.

 

[combo]

Vaillant ecomax says you must have 17-25 mb at P1...this is to check the meter/pipework can supply the correct volume of gas at full working pressure. The vacuum created by the fan to premix the burner does not affect the P1 value, it only affects the P2 value ie a negative pressure........Am I right in saying this ?

 

[combo]

I guess what im saying is, these low mb inlet pressures are to allow for the usual possible pressure losses such as; 2mb WP, 1mb pipeloss, and the possible loss across meter at peak network...its nothing to do with the air/gas valve.

 

[AWheating]

yes your correct that the p1 (inlet) reading should not be effected by the way the gas valve uses the gas. No matter what the situation you are not allowed more than a 1mb drop from the meter test point to the point of connection at the appliance. The manufacturer may state its internal pipework and filters will show a 1-2.5mb drop from this conection to the inlet test point at the gas valve. But this manufacturers drop can not be used to avoid correctly sizing of the gas supply.

so i think for a WB you could have 19mb working pressure, 1mb drop on pipework, 1.5mb drop inside the appliance giving you a min working pressure of 16.5mb as required in the instructions.

 

[Barry98]

For trainees to ask questions prior to passing gas safe

 

[Dotty]

Thread from open forum merged in. Sorry Lee, it's bumped your post down!

 

[bassmonster]

Unsafe situation? It only has a rubber seal on the outside but not cemented inside.....

 

[kirkgas]

Depends on MI of specific boiler, some allow rubber collar to be used as weather seal, only required on the outside to stop POC's re entering property and going up cavity, inside seal is only for decor

 

[bassmonster]

Thank you Kirk. I'll have a nosey in the MI to be sure

 

[albatross]

Unsafe situation? It only has a rubber seal on the outside but not cemented inside.....

View attachment 17879

View attachment 17880

If neither wall is cemented its at risk. Flue must be sealed to the building with cement.(not expanding foam/silicone. Also flue must be adequately supported and the rubber will not do that and just being attached at the boiler is not good enough. If it was low enough some flues could work loose/ be pulled out causing fumes to go into the room if not securely cemented in.