Checking an oil fired burner inside a converted Rayburn

But where?

I don't have a combustion analyser, but if I did, where would I put it?

Open the door and stick it in? Same problem

In through the flue box? Same problem

Basically, the system is sealed up from inlet vent to flue cowl, and it's quite deliberately designed that way.

Flue dampers, as I understand them, work by letting a small amount of air in from the room to the flue system and that small amount of air affects the draw (if it didn't the flue damper wouldn't work). So anywhere I make a hole in the system, whether that's to look in or to stick a probe in, it's going to act like a flue damper and change the draw.

I'm not going to be testing the system I actually want tested, but rather it's testing a different system with that hole in it. Doesn't matter if it's a door, or a flue access plate, or a flue box cover… Anywhere I open a gap to get at the flue gasses is going to change the very system I'm trying to check is OK.

I could climb up on the roof and analyse the gasses coming out of the flue I suppose…

You both seem to have misinterpreted my question, my fault for not being clear enough, I'm sure. The key part of my question was "one issue has always puzzled me…". I'm not asking for a solution, I'm asking for an explanation.

There currently is no such hole, nor is there any such hole in any of my friend's oil ranges. So although I can see exactly how drilling such a hole would be a solution, it doesn't explain why there isn't already such a hole in every oil fired Rayburn in the country as standard… if such a feature is necessary.

Basically, I'm asking how it is that such solutions are not common and yet seem the only answer, or perhaps I'm asking why such modification has become necessary, why there isn't a much simpler system already. I doesn't seem to make sense.

For background - I had a (fully qualified) heating engineer fit a new woodburner last year. As part of the fitting he installed a CO detector, a legal requirement for the fitting to be signed off, even though we already had three in the house. He said "if you get any warning from that, call me, otherwise, it's all good". And that's exactly what I expect. If there's something potentially dangerous about a system, I have an alarm to tell me something's wrong, otherwise I can relax in the knowledge that it's working.

I was puzzled by the conflicting information regarding oil-fired heating which seemed to imply that some special methods were required to obtain that same state of relaxed assurance (I obviously have a CO detector in the same room as the Rayburn too), and yet were far from standard and not even a legal requirement. Why is it that the necessary safety protection for my woodburner is a legal requirement, but I'm having to find out from some helpful folk on an internet forum what the necessary safety protection for my Rayburn is?

(Further background, I've obviously had a few engineers service the Rayburn when I first moved in, I didn't just guess how it was done, I watched them and copied. None tested the flue gasses, none drilled any holes. They just took the burner out, scraped to carbon off, replaced the wicks, vacuumed the chamber, re-lit it and then left

I live in a very rural area. There are two oil-fired heating specialists within 50 miles of me, I've had them both out and both repeated the above, the last one even told me to leave the bottom door slightly ajar all the time which another helpful internet expert told me was positively dangerous advice.

Long and short of it is that I'm out of engineers, so not really a solution for me)

Anyway, it looks like I'm going to remain baffled. Thanks for trying though.

Thanks everyone for the further comments.

Yes, I am indeed on the other side of the pond. South-West England. And @EdTheHeaterMan has hit the nail squarely on the head with a picture of my exact Rayburn (minus it's modified oil pipes), with a wick style burner.

Unfortunately I couldn't drill a hole in the outlet flue as it goes out the back of the flue chamber underneath the old chimney breast, there's no more than about 2 inches of leeway around it. I'd have to drill into the flue chamber itself.

If that would still work, then a hole and smoke spot tester might well be my best course of action, thanks.

If it's smoke (and soot presumably) that I'm looking for, then I can check for that even without the hole/detector because - one advantage of being the homeowner rather than a tradesman - I can have a look in the Rayburn tomorrow, next week, in a month etc. By chance the insulation material in the firebox and flue chamber are white, meaning that I can see the slightest soot build up on them. This has happened only once since I've been maintaining it, after a really weird load of puffing and small explosive noises about 5 years ago, I serviced it and the inside was fairly dark with soot. It's never happened since and every time I come to service it, the inside is completely soot free. The restrictor plate in the flue box has a thin dusting of brown soot after about a year (between services).

At the end of the day I have two concerns of radically different importance;

1. I'd quite like the Rayburn to be running as efficiently as possible so my fuel bills are reduced, but as long as it's in the right ball park I'm not too fussed.
2. It's vital that no dangerous fumes enter the house.

I don't want to confuse the two in asking for advice. Quite happy to set up a system of detectors as per the advice to make sure it's running efficiently, that sounds quite do-able and although a big outlay for the smoke spot detector, it's worth it in the long run, I'm sure. But the most important thing is not what is going up the chimney, it's what isn't (ie what might be coming into the room). Here, I thought, it's FGA or nothing, so I looked up 'the best' on Google and got this result - the Testo 327-1 Flue Gas Analyser. But is says it can check CO (well I've already got an alarm which tests that), CO2, and O2 (presumably to get a ratio?), but only the very high-end ones seem to do any kind of ambient or 'sweep' testing, as the seem to call it, and then only for CO (which I already have a detector for dangerous levels of), and CO2 (which would undoubtedly be impossible to distinguish from the effects of my woodburner).

The trouble with any of these systems is that unless there is a non-machine way to detect when something might be wrong, then you're faced with either doing a 'sweep' of your kitchen every day in case something went wrong overnight, or testing once a year anyway. It's like suggesting we go the hospital for regular brain scan just in case we have tumour. We don't do that, we go when we have severe headaches which can't otherwise be explained. In other words something human-detectable prompts us to seek the technical gadgetry to find out what's wrong. Either that or we have passive alarms like my CO monitor.

So I suppose my question should now be limited to what I suppose is the meat of it - what human-detectable 'red flag' should one be on the lookout for that might cause one to call in the experts with the fancy kit to check what's wrong? If there are no such 'red flags', if it's really true that the Rayburn could be leaking dangerous fumes into the house and I'd have absolutely no way of knowing it was doing so without highly technical equipment and training, then I'm screwed. It might go wrong the day after the technician has been and what then…?

That's really helpful information. Thank you for your time, and patience.

When it's windy, our Rayburn oven temperature drops from the usual 150 (centigrade) to around 100 which seems a fairly massive drop (considering the oil input is remaining the same), so I could easily see the soot coming from the accumulation of those days over the year (it's windy quite a lot these days), rather than a continuous state of too much air, if that makes sense?

In either case, a smoke spot tester seems the way forward, so I appreciate the links.

Cool historical diversion, thanks.

So, here's what I get so far.

Getting a clean burn is about getting the right balance of fuel to air. Too much air vs fuel=unburnt fuel, too little air vs fuel=CO etc.

The restrictor plate cuts down the amount of air drawn in because oil requires less air than wood.

All well and good so far.

But the Rayburn has adjustable fuel levels. I can have it on high or low. I can't be reaching into the flue box to adjust the restrictor plate every time I turn the Rayburn up or down.

So, maybe getting the right amount of air to fuel is done at the inlet - turn the fuel up, let more air in; turn the fuel down, let less air in.

But then any tests the technician carries out on flue gasses are pointless because I'm left in charge of getting the right air:fuel balance by adjusting the inlet every time I turn the Rayburn up or down, and I don't have a FGA to check I've done it right.

So, maybe it's not that fine-tuned and so long as the restrictor plate is roughly right I'll always be in the right ballpark no matter what I do with the inlet.

But the air inlet goes all the way from completely open to screwed tight shut. So that can't be right, I've clearly got the full range of air inlet options, it can clearly be very wrong (no air at all).

So, maybe don't touch the air inlet once set by the engineer.

But then we're back to square one. If it's about air:fuel balance then how come I can turn the fuel up, not change anything about the air, and everything's still fine.

So, maybe there's a wide range of settings that work, as long as I'm not stupid about the inlet. Bit more fuel, no problem, the system will cope.

But then how could anything go wrong if the air:fuel ratios aren't that fussy? There's two holes (flue and inlet) and they've been roughly the same size for the last 30 years. How can cleaning the Rayburn possibly change either by anything other than a very minor degree which we've just established can't make much difference.

It just doesn't make any sense to me.