Gas inlet pressure

[Mike Jackson]

Yea, have u seen any with the high ventilation hole installed which is required for compartment installations, I went to one and the low vent was bigger than required and because the horizontal flue kit is on the same wall as where the high vent should be, there was no vent. In my opinion the high vent can't be put in as it would more than likely draw in products of combustion, any views?

According to the instructions it says that compartment ventilation is only required if overheating is likely.


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[AWheating]

what work is being carried out? service then it could just be NCS if everthing checks out. If its a new/recent install then it needs reporting/riddor and putting right.

 

[JAH HEATING]

Just installed a Ravenheat CSI 150, had about a 16 - 18 mtr carcass in 22mm - whilst with the hot water was running at max I was getting 15mbar working at boiler, 20.5 at meter

Re-piped 6mtr of 28mm, 10mtr 22mm and say 1.5mtr of 15mm

Now am getting standing of 25 but dropping to 12mb working going upto 14mb sometimes

Had Manufactuer out and he say's it's got to be the pipe, personally I think someysthing isn't right with the gas valve myself - getting 25mb standing and dropping to 12mb after I've increased the pipe ? Strange

 

[mcniven]

u sure theres nothing in that pipeworK? solder on a test point near the boiler!

 

[Curnsie28]

JAH heating - that sounds really strange, if you had 15mbar working pressure before you increased the pipe size and 12mbar after.what kw is the boiler?

 

[JAH HEATING]

JAH heating - that sounds really strange, if you had 15mbar working pressure before you increased the pipe size and 12mbar after.what kw is the boiler?

Isn't it just, 42kw.

It's a surface mounted carcass, so I doubt anything has got in pipework ?
I'm going to change the 15 to 22 more or less right upto boiler and the other thing I fitted straight off meter union was 22 - 28 reducer ? so maybe this could be effecting ?

Never had problems in past though ?

 

[Curnsie28]

The 28mm at 6m will give u a pressure drop of 0.20mbar, the 22mm at 10m will give u 1.10mbar of a drop and the 15mm will need to be 22mm pipe. The 10m of 22mm needs to be increased to 28mm to give 0.33mbar drop - total pressure drop of 0.73mbar across total pipework without any bends considered. Hope this helps

 

[JAH HEATING]

The 28mm at 6m will give u a pressure drop of 0.20mbar, the 22mm at 10m will give u 1.10mbar of a drop and the 15mm will need to be 22mm pipe. The 10m of 22mm needs to be increased to 28mm to give 0.33mbar drop - total pressure drop of 0.73mbar across total pipework without any bends considered. Hope this helps

Much appreciated, last time I did gas piping calcs was when I renewed my ACS sadly !!

Ravenheat said 16.5 is fine to leave on by the way ?? Why it doesn't say this in MI never know

 

[mcniven]

42kw wouldnt that be 22mm inlet to boiler

 

[JAH HEATING]

42kw wouldnt that be 22mm inlet to boiler

15mm connection, last 3 meters allowed in 15 in MI it states ?

 

[mcniven]

but look at that pipe run u have mate 16m of pipework BEFORE the 3m of 15 take it all the way to boiler in 22 then u cant go wrong, fit a test point, and do a working pressure test at the appliance, if that checks ok, there will be something between the isolation valve at boiler and gas valve surely ????

 

[Curnsie28]

Some boilers come with 15mm connection and some installers are inclined to run 15 from the boiler around 1 or 2 meters but 22mm needs run as close as possible to the inlet ECM at boiler. (JAN heating - ravenheat specify a 16.5mbar pressure for safe running of the boiler because of the restriction of pipe and fittings on the internal of the boiler. A test tee needs fitted just before the inlet to the boiler to test the working pressure and verify a 1mbar drop from gas meter.

 

[JAH HEATING]

but look at that pipe run u have mate 16m of pipework BEFORE the 3m of 15 take it all the way to boiler in 22 then u cant go wrong, fit a test point, and do a working pressure test at the appliance, if that checks ok, there will be something between the isolation valve at boiler and gas valve surely ????

only have 1.5 max off 15 but will be doing this tomorrow, increasing in 22 !

cheers

 

[Curnsie28]

Spelling mistake EMV not EMC lol

 

[Curnsie28]

Don't forget the 10m of 22mm pipe needs increased to 28mm

 

[JAH HEATING]

Some boilers come with 15mm connection and some installers are inclined to run 15 from the boiler around 1 or 2 meters but 22mm needs run as close as possible to the inlet ECM at boiler. (JAN heating - ravenheat specify a 16.5mbar pressure for safe running of the boiler because of the restriction of pipe and fittings on the internal of the boiler. A test tee needs fitted just before the inlet to the boiler to test the working pressure and verify a 1mbar drop from gas meter.

Thanks for the info

 

[AWheating]

as mentioned in many other threads, even tho the manufacture may state a min. inlet pressure of 16.5mb is exceptable this does not mean that your pipework can have a drop of over 1mb. The gas regulations must be followed, MI do not overide them when pipework and its sizeing is concerned.

 

[mike_s]

Read the manufacturers instructions. Worcester greenstars are often 16.5mb working pressure as there is a further 1.5mb drop at the gas valve. So working pressure at meter must be 19-23mb, maximum 1mb drop to appliance = 18mb -1.5mb drop at the gas valve = 16.5mb.

It is only the newer greenstars which are like this and other boilers with the same gas valve.

It's at risk if lower than 18mb working pressure at the appliance unless the manufacturers state otherwise, like the new worcesters and perhaps in your case but I havn't spoke to them so I'd suggest you do if it is not clear in the book or if you havn't already.

 

[PhilJones]

I was always taught to go back to the manufacturers over the years. Having spoken to various ones when the inlet pressure is insufficient with the correct meter outlet pressure they have all given me their individual acceptable appliance inlet pressure. To be fair, most have also given their names if they feel it is suitable to be left as is (as a back up). All boiler and appliance criterias are different so just issuing a NCS or another warning notice depends on the manufacturer's recommendation; they may deem it suitable or may even deem it AR or ID so as much as we have an opinion, that won't matter in court m'lord.