Isar loud noise, going to f l fault but ok with....

[moogwai]

Door off! Checked condense which was clear, checked flue which was clear. Took off burner and checked probes which were fine!
It's gotta be an air flow problem....would a dodgy fan cause this?
Cheers lads

 

[lame plumber]

sounds like my logic problem all over again, and the fan failed eventually, however what did your fga readings show

 

[moogwai]

Didn't do a flue gas and it's just dawned on me that it could be an fg problem! Can you adjust the ratio on these piles of poop? Can't see how quickly flicking through manual.

 

[solutions]

Any other appliances in use? Inlet pressure?

 

[villa_tom]

You can't adjust the ratio. If it's out then you need a full clean of the heat ex and new seals on the burner, failing that it's the gas valve :-(

 

[The Goose]

Well worth checking the heat pads are still in place as they can make a noise and also burn hole through the back of the heat exchanger.
I have also come across a couple which make a horrid combustion noise and it was caused by the gas valve. Often fine on full gas but made a noise as it modulated down.

 

[zeebeedee]

Check the fan venturi for a blockage

 

[Hirstgas]

The ignition probe will be bent, take out the probe and heat it up with the blow lamp to bend it back straight.

 

[Hirstgas]

Sorry didn't see you'd checked probes!
Have you checked the flue seals they can be slightly trapped or not put together right. Then they vibrate in the flue when the air is Blown past

 

[moogwai]

Any other appliances in use? Inlet pressure?

No other appliances on,inlet presure was fine.

 

[moogwai]

You can't adjust the ratio. If it's out then you need a full clean of the heat ex and new seals on the burner, failing that it's the gas valve :-(

Didn't think you could adjust the ratio on it. Will take a gas valve with me when I go back.

 

[moogwai]

Well worth checking the heat pads are still in place as they can make a noise and also burn hole through the back of the heat exchanger.
I have also come across a couple which make a horrid combustion noise and it was caused by the gas valve. Often fine on full gas but made a noise as it modulated down.

Heat pads were fine, I've also experienced the hole in the back of the heat ex!! Not good!

 

[moogwai]

Sorry didn't see you'd checked probes!
Have you checked the flue seals they can be slightly trapped or not put together right. Then they vibrate in the flue when the air is Blown past

I took the flue apart and put back...seals looked ok.

 

[moogwai]

Thanks for the replies lads....gonna go back with a gas valve and give the heat ex a good clean out....I'd normally associate this fault with blocked condense, but took that out and also had the sump cover off and it was the cleanest isar I have ever seen!

 

[TBServices]

I went to one a few weeks ago, condensate trap was clean but pipework was blocked.

 

[moogwai]

I went to one a few weeks ago, condensate trap was clean but pipework was blocked.

Pipework is fine as with the cover off the heating worked ok. Spoke to ideal they said it's Deffo and airflow prob as it works fine when cover is off.....gonna be a new flue! Which ain't covered on their policy and I don't have one to go back! #dodgedabullet

 

[Hirstgas]

If it's the old metal flue the condensate corrodes them invetweeners the air intake and outlet. Changed loads to plastic recently because of that

 

[moogwai]

Just remembered to update.....this was a dodgy flue....replaced it and it fired right away with no probs.

 

[Roger Welton]

I hope when you say replaced 'it' you're referring to the boiler. The only good isar is a scrapped isar

But good to hear it's sorted

 

[buckley plumb]

had in icos where the secondary heat exch was blocked but analyser readings were ok

 

[armourer]

I cannot believe you didn't fga it? It would have picked this up straight away.
If you check the outer flue also it will tell you if the seals have gone.

Would have taken a lot less time than taking the flue apart.

 

[moogwai]

I cannot believe you didn't fga it? It would have picked this up straight away.
If you check the outer flue also it will tell you if the seals have gone.

Would have taken a lot less time than taking the flue apart.

Flue was over the 3m height I'm allowed to work at the company I work for (only have step ladders, barmy I know)and beings there is no sample point for airflow on a isar....so there! smart ars3.

 

[Ermintrude]

There is and air intake . It's on back of boiler where burner has melted case. Read the MI!

 

[armourer]

The test point is on the top of the boiler to the right of the flue. For future reference. ;-)

And for air test. Remove the front cover andand put your fga into the outer flue at the turret. Any co readings and your seals have gone. Your right i am a clever bugger. Lol

 

[zeebeedee]

The test point is on the top of the boiler to the right of the flue. For future reference. ;-)

And for air test. Remove the front cover andand put your fga into the outer flue at the turret. Any co readings and your seals have gone. Your right i am a clever bugger. Lol

How could he fga it when the boiler wouldnt light with the case on?

 

[Ermintrude]

Check it via the pump?

 

[Ermintrude]

It's an issue with rectification leads. Buy kit

 

[armourer]

Start the fga with cover off then fit the cover. You would have seen the O2 dropping rapidly and the CO rising before the fl lock out.
It would have told you straight away what the fault was.
Im not having a go just pointing out you can get a lot of information from the fga not just ratios that will tell you what the problem is.
I know hindsight is a wonderful thing and I am just passing on information that maybe of use to people.

 

[zeebeedee]

Start the fga with cover off then fit the cover. You would have seen the O2 dropping rapidly and the CO rising before the fl lock out.
It would have told you straight away what the fault was.
Im not having a go just pointing out you can get a lot of information from the fga not just ratios that will tell you what the problem is.
I know hindsight is a wonderful thing and I am just passing on information that maybe of use to people.

Ahhh didn't know it was staying lit once it got going!!!

 

[moogwai]

note I said airflow mate.....I know about the test point for fg. The last one that I had where the flue seals had gone it had tell tale signs of condensation re-circulating back to the boiler as the combustion chamber was full of condensation...guess I was looking for that

 

[armourer]

Like I said mate, if you start with case off then case on it will show an air flow fault. Also like I said earlier run with case off and put your fga up the outer flue at the turret. Any CO reading will tell you the internal seals have gone. Still a lot quicker than stripping the flue down.