strebel scb60 wall hung condensing boiler intermittent lockout

[Dsgas]

hi im working on 3 strebel scb60 boilers on a low loss header sharing a common flue.2 of the boilers have got very high co readings on flue gas analyser.
upon further inspection the flue seemed to be leaking inside the boiler casing at the top of each boiler.the flame picture was very unstable.the 3rd boiler was replaced a year ago with a warped heat exchanger.i have compilled a quote to rectify leaking flues in the two boilers but am looking a second opinion.if the heat exchangers are warped would this affect the co readings by partially blocking the flue outlet?
Any replies appreciated.

 

[SimonJohns]

These boiler can suffer with recirculaton

Be aware that you should be analysing these boilers with the cover off

And then afterwards like this to check for recerc

Also you should have a non return valve in flue outlet. It will make a tink noise when the boiler is starting up if it's working correctly

If you can commission the boilers correctly before putting the cover back on it will help make sure you haven't got a loose air gas box, faulty gas valve. Or recerc

Be sure to strip these every other year. The he can coke up quite quick

 

[Dsgas]

Many thanks for reply simon.

tested flue gases with analyser with cover off but co was over 1000ppm. there was also strong smell of flue gases and visable spillage & condensate around top of flue gas collection box.

had non return valve out of flue to check for operation which was ok.

if heat exchanger coked up which is best way to clean.have flushed water through it as per manufacturers instructions.these boilers have been neglected!

Many thanks
Dave

 

[SimonJohns]

Good old get inside and brush/scrub over

It's the same type of he as a valliant.
Did you have alot of green and yellow deposits.

If you have got all then issues. I would repair as necessary and then fully recommission. So reset gas valve and set high and lows.

 

[Dsgas]

alot of green and yellow deposits around flue gas collection box at top heat exchanger had just some lint that could be hoovered out on heat exchanger, it was quite sooty around the flue gas test point plastic screw.

the people that changed the other boiler said it had a warped heat exchanger i had a look at the old boiler heat exchanger as it had been left there and it looked ok!

 

[SimonJohns]

I've never heard of that happening

I look after a few of these and I have been told that vinegar is good for heavy deposits. But I've never tried that. Just taken my time scrubbing and getting it off.

 

[Dsgas]

would you get flue gases recerc even with the cover removed to give a high co reading.

sorry for picking your brains contacted the manufacturer on this and did'nt get a definative answer.

thanks again
dave

 

[SimonJohns]

I wouldn't expect it with cover off. I would suspect over gassing with blocked flueways.

Have you checked integrity of air gas box?

 

[Dsgas]

I think i need to get heat exchanger out and give thorough clean and also clean inside of plastic flue gas casing.

Air gas box seemed fine will check again.

 

[SimonJohns]

It's dead easy to get he out. Only a few clamps and 2 unions.

If your going to take it out. It may be worth using a dry side cleaner.

Be careful putting it back in. The gas pipe won't line up with air gas box If the he is not located proper.