worcester 28i junior gas rate

[coley]

gas rate 2.7 m3/hr on high fire MI states 3.02 m3/hr. Working pressure 20 mbar.

readings from anaylizer

co2 9.8
02 3.6
x air 20.8
co ppm 100

CO/C0 0.0010

On low fire all readings as per MI

Whats the problem

Any help please

Thanks Coley

 

[GreenArmy]

coley have a look at this thread. What was the gas rate in Net KW?

 

[coley]

Thanks for that I did a search but I did not search hard enough. Its the very same problem I have come across. However the ratio is higher.

We have spoken to worcester regarding this and they said it was a blockage in the gas valve and are sending an engineer out.

After reading the other post I dont think this is the case.

Another problem is the hot water delivery the boiler can not keep up with demand. Which I thought was linked to the low gas rate.

Mcws is approx 6.5 bar
dhw 8 ltr per min =approx 45c to 49c to be honest its all over the place

drop it down lower say 4ltr per min and it can achieve about 55c

To compare like for like is that normal for the 28i junior.

gas rate =90@2mins = 28.86Kw gross, 26.24Kw net

Thanks
Coley

 

[GreenArmy]

If worcester are sending out an engineer then leave it at that. Your readings are good.
As far as your hot water is concerned the temperature your getting sounds ok to me based on the fact that the boiler will have a temperature rise of >30c or >35c, so based on incoming mains temperature (lets say 8degreesC) you are exceeding that at 45c.
What was the gas rate in net KW? Isn't the 3.02 m3/hr that you stated used for working out pipe sizing?

So your just over your 5% tolerance. Have you checked pipe sizing and standing pressure at meter and inlet pressure (1mbar drop across pipework) If thats all good then wait to see what worcester say and please report back to let us all know if it turns out to be a problem with gas valve.

 

[coley]

Worcester have been on site apparently all I know until Monday they have changed a part I presume the gas valve. I will not know until Monday. But will post back. Thanks for the help

Regards Coley

 

[GreenArmy]

Speaking to a fellow gas engineer this morning at the merchants who mentioned he had a problem with a brand new worcester 28i boiler that fired up first time and then wouldnt fire again. He spoke to worcester and they told him that there was a problem with some gas valves that were leaving the factory without being set up properly. Apparently to the top right of the valve there is a 2.5mm hex srew covered in that red wax (not apparently were you adjust your gas/air ratio) and these can be clogged with the red wax. Allegedly if you wind this right in till it stops and then unwind 2 1/2 times (possibly 3) this will set up the gas valve and clear any red wax blocking it. Might be worth keeping this info in back of mind in case we come across this issue again and try it.

 

[heating-eng]

Thanks for that I did a search but I did not search hard enough. Its the very same problem I have come across. However the ratio is higher.

We have spoken to worcester regarding this and they said it was a blockage in the gas valve and are sending an engineer out.

After reading the other post I dont think this is the case.

Another problem is the hot water delivery the boiler can not keep up with demand. Which I thought was linked to the low gas rate.

Mcws is approx 6.5 bar
dhw 8 ltr per min =approx 45c to 49c to be honest its all over the place

drop it down lower say 4ltr per min and it can achieve about 55c

To compare like for like is that normal for the 28i junior.

gas rate =90@2mins = 28.86Kw gross, 26.24Kw net

Thanks
Coley

never had one fail in the past , i will look out for that.

 

[Deleted member 2053]

Could also just be the meter giving a false reading. I have come across some where the first half of a measured volume takes a completely different amount of time to the second half!

 

[John Flower]

Dont forget that when taking your readings from the test point on the gas valve, i.e for resistance across the pipework,there is a resistance of 2mbar across the valve, so to confirm that i have only a 1mbar drop across the pipe work ,i cut in a test nipple on the supply underneath the boiler and test from there .

 

[heating-eng]

Could also just be the meter giving a false reading. I have come across some where the first half of a measured volume takes a completely different amount of time to the second half!

its very unlikey you will get a false reading from the meter .

 

[Deleted member 2053]

its very unlikey you will get a false reading from the meter .

'unlikely' and 'impossible' are not the same word. I can think of no other explanation as to why a meter would consistently give different timings for two halves of a measured volume than there being some meter fault.

 

[heating-eng]

'unlikely' and 'impossible' are not the same word. I can think of no other explanation as to why a meter would consistently give different timings for two halves of a measured volume than there being some meter fault.

worked at bg for 20 years and we supply the meters ,they do not go wrong.
the person reading it doesnt have a clue what there doing thats whats wrong

 

[the_ace]

Meters do read the same amount of gas at different rates thats why the test is done over 2 minutes, down to the way the bellows work inside the meter.