Baxi 105HE high emissions

[bewsh]

Getting high emissions on a Baxi 105HE, a full strip down has been carried out but then found that the secondary heat exchanger seal behind the plastic connection had failed and was leaking condense back in to the boiler.

So, I replaced the entire secondary heat exchanger today but still getting high emissions. I took the fga out at just shy of 400ppm, but it was still slowly crawling up.

Gas pressures/gas rate all ok. Checked air intake, 0ppm 20.7% O2. Heat exchanger clear, insulation pads in good condition, burner looks fine as well.

Anyone know any common faults to look out for?

Cheers!

 

[REDSAW]

whats the burner pressure & whats the o2 reading?

 

[gassafe]

whats the burner pressure & whats the o2 reading?

I didn't think we did burner pressures on these HE boilers...

 

[REDSAW]

12.1mb
whats the ratio and co2 reading in the instruction manual ?
i assume the heat sheilds are in place?

 

[Billy Bob Bob]

There is no co2 reading for a 105 he,basically there is a high concentration of pocs in the secondary hex due to its design, if its passing a integrity test,getting 12.1mb on full rate and its otherwise got a clean burner and hex there's not.much else wrong

 

[GrahamM]

Seals good between fan and secondary exchanger?
Flue restrictor removed?
Max BP is 12.1 +/- 0.5mb. I would set it at lower end of this ie. 11.5mb.

 

[REDSAW]

There is no co2 reading for a 105 he,basically there is a high concentration of pocs in the secondary hex due to its design, if its passing a integrity test,getting 12.1mb on full rate and its otherwise got a clean burner and hex there's not.much else wrong

thats what i was getting around to
no good dipping the analyser in

 

[bewsh]

Ye getting 12.1mb burner pressure, working pressure is 19mb as well.
No flue restrictor on this boiler (i don't think). The two clamps between fan and secondary heat exchanger are all good.

I lowered the burner pressure to 11.5mb and the emissions were a lot better.

So you wouldn't have bothered analysing it then redsaw?

 

[REDSAW]

curiosity after checking the bp, never going to agree with what youd expect and theres no parameters set by baxi for it!

 

[GrahamM]

For last 6 years I have been on the books for companies who have a policy of using FGA on EVERY boiler so I don't get to pick and choose.
Personally I have never come up against a boiler with readings way out of range of MI's or general standards that could not have been put down to some issue with workings of boiler.
We have a tool at our disposal that can show up issues with standard efficiency/non-zero governed boilers so why not use it on every appliance we can.
Just my opinion!

 

[gassafe]

I agree, we have an analyser so may as well use it & it reassures us the boiler is running cleanly & safely etc...

It does catch you out tho when a boiler looks to be running clean but has high co etc lol!

 

[REDSAW]

so what do you record?

 

[bewsh]

I did speak to baxi technical about it, but they couldn't really suggest anything that I hadn't already checked. But I suppose if I didn't have my analyser that day, I would be non the wiser anyway.

 

[gassafe]

I find this with gas fires, no need to flue gas Etc but the ppm can be really high on some!!

 

[armourer]

Make sure you run these boilers for a good while before you stick your fga in too. I have had quite a few read high initially but settle down after 5 mins or so.
Also too soon and you will flood your sensor in the fga. It takes bloody ages to settle down again.