Worcester greenstar 40 cdi Heat Exchanger Rumble

[gary]

Hi Guys

Today a changed a gas valve on a 40 cdi and now as it burns after there's rumble (not good) sound coming from the heat exchanger. The boiler needs a service as it been requesting one for months apparently.
I'm thinking it is either the gas ratios or there is just to much crap in the heat exchanger.
I've put them on a hot water only diet for tonight and will sort it out tomorrow.
Any ideas?

 

[gary]

Cheers, i appreciate the advice.

 

[gary]

i'm proper stressing now. ​ whats the worst that can happen

 

[Destroyer2813]

When you change either a gas valve or fan on a Worcester you MUST reset the co-co2 high-low ratios

 

[gasmarc]

I hate it when I think I may have made a mistake, Like yesterday I had to go back on a job where there was a small drop and I could not remember if I tested a 22mm compression fitting ,which as it happens was fine , Unlike last friday I turned off the mains on a house and got a great shock when isolating some wires that the sparks had wired directly into the meter, That will teach me

 

[gary]

Update.. if anyone is interested. the pipework was under sized and when on Max output working pressure dropped from 23
mb to 8mb. Not a good time of the year to tell the customer he needs his concrete floor chasing to lay a new gas pipe. So Convinced it was co ratio's and my broken analyser forgot to go back to basics.

 

[Destroyer2813]

Slapped hand for whoever installed it then

 

[Kev the gas]

Update.. if anyone is interested. the pipework was under sized and when on Max output working pressure dropped from 23
mb to 8mb. Not a good time of the year to tell the customer he needs his concrete floor chasing to lay a new gas pipe. So Convinced it was co ratio's and my broken analyser forgot to go back to basics.

Gary,

Are you saying the inlet pressure dropped to 8mbar at the inlet of the boiler?

Can I suggest you recheck the working pressure at the meter test nipple.

Sounds like the meter governor is knackered.

8 mbar at a boiler inlet test nipple even tho a 40 cdi boiler is very very low, or the meter is about 30m away from the boiler and outlet in 15mm !!

or another thought were you trying to test burner pressure?, the Greenstar range only allow inlet working pressures, burner pressures can read negative !

 

[gary]

Kev

My first thought was the governer, but working pressure at the meter was 20mb.
The scary thing is that it was installed in 2006 and not picked up on commission or since. The new owners have only been there 3 months.
I don't know weather the new cit gas valve i fitted has made a difference but all my test were meter side of the valve. I suggested they get a second opinion and the other engineer came to the same conclusion.
However he was some how able to get the pressure up to 14mb, don;t know how?

 

[Kev the gas]

Hi Gary,

It depends on how you/ he is checking the inlet working pressure. ie just checking the inlet pressure with a hot tap running or using the spanner button heating on max. Later models have the boost button under the spanner.

Worcester MI state min 18 mbar !

Are you using the new gas analyser for the pressure testing ?

My telegan Sprint needs resetting on the pressure button before connecting onto a new test nipple. The unit is 6 years old but has been calibrated every year, had new pump/ sensors ect.

If you are not doing this it might explain the difference in yours / his readings ??

It does sound tho like a nice few lengths of 35mm and 28mm will be reqd very quickly.

Your co/co2 readings are irrelevant if you have such a low inlet pressure.

To cover yourself I would AR the appliance.


Kev.

 

[gary]

That's true, i was testing mine on max via the heating boost with my now much loved (expensive) Kane. If he did his on dhw it may differ, but if he has taken his readings on the dhw then he is as bad as the guy who commissioned it.
I left it with power off, gas isolated and advised them not to use it with signature. Other engineer has allowed them to use dhw till the up grade can happen.
Be it on his head, but it has been fine for 5 years and its christmas!

 

[Billy Bob Bob]

Gary,

Are you saying the inlet pressure dropped to 8mbar at the inlet of the boiler?

Can I suggest you recheck the working pressure at the meter test nipple.

Sounds like the meter governor is knackered.

8 mbar at a boiler inlet test nipple even tho a 40 cdi boiler is very very low, or the meter is about 30m away from the boiler and outlet in 15mm !!

or another thought were you trying to test burner pressure?, the Greenstar range only allow inlet working pressures, burner pressures can read negative !

kev is giving good ,solid advice here pipework may be undersized but a Governor fault is the likely fault here

 

[gary]

The supplier came out changed the whole meter, so the 2nd in a week.

 

[gary]

I'm assuming the gov is changed as part of the meter?

 

[keltoyboy]

Surely changed the govenor....prob took the opportunity to replace meter with a shiny new more efficient one while they were there.

 

[gasmarc]

Sound like a right nightmare lets hope its sorted , I had to ID a 85KW boiler in a small office block the other day and the guy was going mental and talking about closing down because he could not afford a new boiler, you could use trac pipe if you get the rerun