Low gas pressure

[jaydebruyne]

Nope your looking at the tables wrong. That 2.9m3 refers to a 3m length of 15mm with a 1mb drop.
A mere 20 cm section would flow alot more than that...by my loose reckoning easily in excess of 5m3

I wasn't looking at a table. I was using the mr combi pipe size app and for the length of 15 I have with 1 elbow you won't get higher, needs to be 22

 

[mfgs]

Why not put a reducer on the connection from the boiler and take it straight to 22 or 28? That's what I do with boilers which have 15mm connections. I would also tee the hob off either the 22 or 28mm pipe.

 

[joni os]

App. and Tables in agreement 2.9 flow gives 3 meters and 20 meters for 15 &22.
Length 700mm pressure drop 700/3000 & 700/20000 which equates to the 0.233 & 0.035 given by App.
Phil also right with flow through 700mm length of 15mm. 1/4 of 3 meter length could be expected to give double the 3 meter flow, ( L X Q X Q approx constant).

 

[jaydebruyne]

App. and Tables in agreement 2.9 flow gives 3 meters and 20 meters for 15 &22.
Length 700mm pressure drop 700/3000 & 700/20000 which equates to the 0.233 & 0.035 given by App.
Phil also right with flow through 700mm length of 15mm. 1/4 of 3 meter length could be expected to give double the 3 meter flow, ( L X Q X Q approx constant).

Why does the app say for 2.91 with an effective length of 700mm you need 22?

 

[jaydebruyne]

Why not put a reducer on the connection from the boiler and take it straight to 22 or 28? That's what I do with boilers which have 15mm connections. I would also tee the hob off either the 22 or 28mm pipe.

I will do from now on! But from what Phil and Joni say I should get enough flow from that short run of 15 ... so what gives?

 

[newcastle phill]

Can you upload a drawing. Something doesnt add up here from what youv'e said.

 

[mfgs]

Sorry if you have answered this before, but what is the working pressure at the meter?

 

[jaydebruyne]

Sorry if you have answered this before, but what is the working pressure at the meter?

21.5

 

[jaydebruyne]

Can you upload a drawing. Something doesnt add up here from what youv'e said.

A drawing of the run?

 

[newcastle phill]

I dont use apps or rather put an over reliance on them. Pen and paper is best. But ive downloaded one that says different anyway which is more in line with my ready reckoning.

And 30kw is 30kw wether its vaillant, ideal or heatline - its not the boiler. As this demonstrates that small bit of run can handle upto a theoretical 45 ish kilowat

Edit.
Yep accurate drawing of the run.

 

[jaydebruyne]

I dont use apps or rather put an over reliance on them. Pen and paper is best. But ive downloaded one that says different anyway which is more in line with my ready reckoning.

And 30kw is 30kw wether its vaillant, ideal or heatline - its not the boiler. As this demonstrates that small bit of run can handle upto a theoretical 45 ish kilowat

Edit.
Yep accurate drawing of the run.

What app is that Phil?

Agreed re: heat input ratings.. I've tried drawing it and my drawings are confusing.. but basically there are 24 elbows, 2 45s and approx 14 meters of 28mm.

 

[joni os]

Very experienced Gas Engineer was perplexed to be reading 16 at meter with his brand new certified digital manometer. Explanation, it was set for mmHg instead of mbar. Trust nothing at first sight.

 

[jaydebruyne]

Very experienced Gas Engineer was perplexed to be reading 16 at meter with his brand new certified digital manometer. Explanation, it was set for mmHg instead of mbar. Trust nothing at first sight.

Lol oh dear!! I used a manual wet u-gauge though

 

[newcastle phill]

I cant put that into a visual way.

But all id say is if youve teed off the 15mm to the hob - I wouldn't have done that. Id have teed off the 28 to the hob and left that final 15mm run to the boiler unimpinged.

 

[jaydebruyne]

I cant put that into a visual way.

But all id say is if youve teed off the 15mm to the hob - I wouldn't have done that. Id have teed off the 28 to the hob and left that final 15mm run to the boiler unimpinged.

I hear you about the hob. If need be I'll change it. But even with the hob disconnected from the supply it didn't change the readings I got for the boiler.

 

[Last Plumber]

That's equivalent of 27 meters ish !

Has it grown ?

 

[Last Plumber]

If your hob is tee'd into that 15 it will be affected !

 

[Simon F]

Was the 21.5 at the meter with the boiler on max or just with the hob on.
And as everyone elce is saying dont have the hob and boiler both of the same section of 15mm pipe.

 

[Simon F]

Was the 21.5 at the meter with the boiler on max or just with the hob on?
And as everyone elce is saying dont have the hob and boiler both of the same section of 15mm pipe.

 

[ShaunCorbs]

found this mate and thought of you

https://twitter.com/irbheating/status/834063695613423618

incoming 20 mbar

gas test nipple 15.7 mbar

 

[jaydebruyne]

found this mate and thought of you

https://twitter.com/irbheating/status/834063695613423618

incoming 20 mbar

gas test nipple 15.7 mbar

You, Sir, have MADE MY FRIGGIN DAY!!!!!!!!!!!!!!! ))

 

[jaydebruyne]

found this mate and thought of you

https://twitter.com/irbheating/status/834063695613423618

incoming 20 mbar

gas test nipple 15.7 mbar

Where can I get these compression test points???? I've searched but can't find them

 

[Atouchofgas]

Use one of these
https://www.bes.co.uk/22-mm-x-22-mm-x-1-2in-tee-compression-x-compression-x-bsp-f
With one of these
https://www.bes.co.uk/1-2in-x-1-8in-hexagon-bsp-parallel-reducing-bush
And one of these
https://www.bes.co.uk/test-point-nipple-brass#product-details-tab

 

[ShaunCorbs]

Where can I get these compression test points???? I've searched but can't find them

15mm or 22mm to 1/2 t and then reducing bush from 1/2 to 1/8th

 

[jaydebruyne]

Use one of these
https://www.bes.co.uk/22-mm-x-22-mm-x-1-2in-tee-compression-x-compression-x-bsp-f
With one of these
https://www.bes.co.uk/1-2in-x-1-8in-hexagon-bsp-parallel-reducing-bush
And one of these
https://www.bes.co.uk/test-point-nipple-brass#product-details-tab

Aaah I see!!! Cheers dude