FGA Readings - Oily question!

[dontknowitall]

I've not asked a question for ages but need some help.

I serviced a 20 year old boiler yesterday and have warned the customers (one of my regulars) that next time they should think about a boiler funeral service. In the meantime I want to make this thing run for a good six months but got some odd readings and need to know how to correct this.

I've mislaid my oil pressure gauge so will have to return to check this but boiler sounds great and the flue gas is clean (viewing and smoke test).

Last year's nozzle was quite clean (as was the one from the year before) and the readings were fine in those years. Yesterday I got:

Mistral boiler
Riello (2.2? - 1992 model)
I changed the nozzle with the same: 0.75 80 deg EH

First test produced over 15% CO2
Closed down air from 3.5 to 3 ish (scale 1-6) but the CO went to around 80ppm :redface:

I finished by adjusting the air to nearly 4 and have left the boiler until I find my oil pressure gauge.

186 degrees C
13.21% CO2
13 ppm CO
0.0001 Ratio
7.6% O2
89.2% Effn
82.1% Effg

Only other thing I can think of that might help is why I'm condemning the old girl. The customer's have been itching to have a new boiler for a while but, more importantly, the baffles are much more difficult to remove/replace for cleaning and I feel the boiler is running far too hot (metal fatigue over the years?)

So, the question is do I have to go back or are those readings sort of okay?
If it's best to return (when I find my oil gauge) what should I check/test/change?

Many thanks in advance!

 

[SimonG]

Def worth a return trip with the oil gauge, poss running a little high on the oil. At 13.2% it wont take a lot to start sooting.

I would call in next time passing and check oil pressure and adjust from there. Easier than having to de soot it 🙂

 

[dontknowitall]

Thank you, Simon!

 

[DirksPlumbing]

Def worth a return trip with the oil gauge, poss running a little high on the oil. At 13.2% it wont take a lot to start sooting.

I would call in next time passing and check oil pressure and adjust from there. Easier than having to de soot it 🙂

Very much agreed except of the fact that I would expect it mildly sooting already at 13.2%.
Maybe a good idea to have a look for a smoke pump too. That possibly would have told already.
Beautiful job to have to clean the boiler and the flue after it sooting. Gets even better on condensing models. That is usually a one job day since the rest of the day you are enjoying cleaning yourself.

Make sure before you leave this place the next time to recheck the photo cell.

By the way: I tend to find all sorts of nozzles in boilers. Quite often they should not have been used at all. Always check the MI / data badge.

 

[dontknowitall]

Many thanks for the input Dirk.

Smoke is 0-1 and no visible smoke from flue either.

What's puzzling me is why with no adjustment and having run so cleanly for the last couple of years it suddenly gives me such a high CO2 and O2 reading - and, having done so, what is causing this. (Nozzle fitted is the recommended size.)

As said, when I find my pressure gauge I'll be able to check the oil pressure as it could be the pump is on its way out.

 

[Best]

Yes, 13% is getting high. He said he had done a smoke test, so assume he used a smoke pump. When the CO2 is too high you raise the air setting to lower the CO2. Danger that someone has touched the oil pressure screw on oil pump by mistake if they previously tried to bleed the oil pump if out of oil.

 

[Best]

Many thanks for the input Dirk.

Smoke is 0-1 and no visible smoke from flue either.

What's puzzling me is why with no adjustment and having run so cleanly for the last couple of years it suddenly gives me such a high CO2 and O2 reading - and, having done so, what is causing this. (Nozzle fitted is the recommended size.)

As said, when I find my pressure gauge I'll be able to check the oil pressure as it could be the pump is on its way out.

New nozzle could be faulty! Oil pump on Riellos tend to just wear & oil pressure drops to 7 bar, which is usually just about okay on Kerosine.

 

[dontknowitall]

Many thanks Best. I've had a faulty nozzle before so I'm not discounting this but must find my gauge - I think that's 3 of us who reckon it's the pump.

I'll have a rootle (speling?) around the van over the weekend for my gauge.

 

[Best]

Get yourself a spare new oil gauge (glycerine filled gauge) for all they cost & keep it in a box with oil tools only. Its one tool you can't do without.

 

[DirksPlumbing]

Many thanks for the input Dirk.

Smoke is 0-1 and no visible smoke from flue either.

What's puzzling me is why with no adjustment and having run so cleanly for the last couple of years it suddenly gives me such a high CO2 and O2 reading - and, having done so, what is causing this. (Nozzle fitted is the recommended size.)

There is hundreds of reasons for a changed setting. You would not believe what kind of things you can sometimes find in the airway of oil boilers. Starts with missing bits of washing, animals, cob webs, wasp nests. Not to forget the all present dust in various thicknesses.

As well as a changed oil pressure is perfectly normal especially if you have changed the nozzle. That is one of the reasons why pumps are adjustable. Even a filter clean can make a difference when the pump does not need to try to suck desperately the filter including casing and sludge up the 10mm line anymore.

Up to smoke 5 I usually struggle to see even a shade of smoke in the fumes. Against light backgrounds. So I would not bank on that. Once you can see it smoking it is really bad. If you can read a 10 on the neighbours white bed sheets it is definitely time to pull the FGA out 😱mg_smile:.

 

[SimonG]

You generally know you have a problem when you see a little diy 4mm allen key in the bottom of the boiler 🙂

 

[kimbo]

How accurate ois your analyser if you havent had it calibrated it could give you a bad reading, I always finish off by smelling the flue gases.

 

[WHPES]

High CO readings are usually caused by one or more of the following:

1) not enough air to give complete combustion (check flue and air inlet and room ventilation)
2) too much air having the effect of "blowing out" the flame (reduce air)
3) too high pump pressure putting too much fuel through
4) worn pump giving uneven spray
5) wrong, worn or faulty nozzle
6) contaminated fuel (eg with some gas oil mixed in it)
7) soot, fuel drips etc in the combustion chamber as a result of servicing or flue sweeping (leave running for an hour to burn off and take readings again)



Possible but unlikely to be the nozzle.

Check pump pressures. Maybe pump starting to wear out. Can give poor spray pattern.

If it's a conventional flue, has it been swept recently?

Check balanced flues and low level flues using a flue brush. I once found a dead bird blocking a flue pipe.

If balanced flue check that the seal between the inlet and outlet has not started to degrade and needs replacing (common problem on 1990s Triancos with BF)

As previous poster says, smell flue gases (don't inhale of course). Oily sooty smell means too rich. Harsh, acrid smell means too lean.

If the customers are keen on something newer and more efficient, then it's getting on and it's a good idea to replace.

 

[dontknowitall]

Thank you for the continued input and BIG thank you for that post, WHPES!!

That should be required learning for people like me!!

I will be returning but need to find my gauge (I'm sure I've already said this?!)

 

[WHPES]

First and foremost I'm an engineer before a boiler guy.

Many years ago when I'd not been going long, point (7) had me puzzled when I came to set up a boiler after the chimney sweep had cleaned the flue. Took me about 1/2 an hour before I realised all the soot debris in the chamber was burning off and giving me duff readings. Came back in a couple of hours when all burned off and set it up no problem.

I once found a dead rat in a combustion chamber where the customer had not run the boiler over the summer and turned it on to find smoke coming out of the flue.

 

[DirksPlumbing]

I once found a dead rat in a combustion chamber where the customer had not run the boiler over the summer and turned it on to find smoke coming out of the flue.

Must have been a big boy. Had 3 weeks ago a boiler with a dead bat in in. To wet to get it cleaned. And wasps. Stuck the burner back in and test run it for less than 30 seconds. All had turned into ashes. Just a few bone fragments you could imagine where the bat had been.

 

[WHPES]

PS to my previous post, just thought of another reason - the air diffuser / nozzle distances set incorrectly will give high CO readings again because it results in incomplete combustion.

 

[DirksPlumbing]

PS to my previous post, just thought of another reason - the air diffuser / nozzle distances set incorrectly will give high CO readings again because it results in incomplete combustion.

Jupp. But on domestic boilers that normally requires a dodgy engineer as most of them are not or not straight to set up nowadays . Still remember the old days where the distance bolt had been accessible at the back. How often these had been "screwed" with. Possibly because they had been mistaken for air settings.

Another curiosity I have not seen since many many moons are the "blue" burners.
Hated them with a vengeance. As the ceramic blast tube easily cracked by taking the burner out.

 

[yorkie]

Called out last week October to W/bosch combi that had stopped working. Listened to customer as you do and asked him to put phone to boiler and re-set as he said it was working then stopped I didnt think it was firing just the fan purging. When he did the noise was that of a broken /stuck motor. Went round next morning and under the fan casing was a big blob of goo. Open casing and found three mice totally perished and chewed up by fan. They had gone rotten and dripped all inside casing and ran out. Cleaned all out as they had jammed fan and boiler now working after good service. Lovely jobs we have.

 

[Best]

I have just posted on the thread "mouse jam" about similar thing, except fan kept running but air was partly blocked & boiler sooted up badly. All bits of fur & grease! Terrible! :smile:

 

[WHPES]

I always have a can of Jeyes fluid in the van! You just never know.........