Chaffoteaux FlexiFlame 140 boiler periodically cutting out

I have a friend running a small business with a wall mounted Chaffoteaux FlexiFlame 140 boiler installed for central heating, which I am looking after while he is away.

The problem is that it turns itself off every so often - a few times a day. At the moment it keeps going for several hours if the thermostat is turned down to around 1/3 to 1/2 scale, but thats not giving enough heat output this weather. Any higher and the overheat (presumably) cuts it out. He has a Br Gas servicing contract and they have been once to find it working and walked away with "no fault found, but it very old you ought to get a new one". Calling them back 3 days later, they replaced the thermocouple. Needless to say the fault is still there. Water circulation and system pressure appear to be OK.

From the manual

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appears that the thermoelectric valve is a replaceable part - could it be that sticking? Is it still possible to still obtain one? Any other possibilities, like a PCB fault? I won't be replacing these myself but am looking for ammunition to persuade Br Gas to get their finger out and fix it rather than shrugging it off as too old.

It IS old, and could well be that its a good plan to replace it with a modern high efficiency unit, any suggestions for that please? The rating of the present one is 20.5 to 40KW though I have no idea if it is set at its max value or not.

Cheers Phil

Reply to
Phil Addison
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I'm not familiar with this model. It sounds to me that the normal thermostat is probably OK, the safety over-heat cut out is faulty.

Very likely the over-heat cut out breaks the pilot thermocouple circuit directly. Without doing my own tests right there it the part I would change first, it won't be very expensive and it's fairly straight forward.

Reply to
Ed Sirett

Thanks Ed. I don't fully understand what the fault mechanism would be there. Do you think the over-heat cut out could be permantly declaring overheat, or just declaring overheat at too low a temperature (bearing in mind the boiler does run at low main control stat settings). Is the overheat stat likely to be mechanical switch, or a thermistor type. I can more easily see how the later could fail to a reduced overheat temperature, but would expect a switch to fail either open or closed?

The Br Gas report says they "replaced the thermocouple". I'll chase them up and ask why they didn't change/check the overheat stat. Its clearly listed in the manual as service replacement item (para 8.2 in the above pdf). Can you suggest where/how I go about obtaining a suitable replacement? I can see I might finish up diy-ing it before BrGas get their finger out.

Phil

Reply to
Phil Addison

In message , Phil Addison writes

Wrong time for it to go wrong Phil

John. who works for me, has one of these - there is no way that he wouldn't know this boiler inside out

He had a heart attack last week and is in hospital ATM

If it can wait a while, as soon as he stops malingering, he'll prolly have the answer

Same as Ed, I'd look to the overheat stat as being the culprit, and being only a few quid to replace, worth a punt

It couldn't be that it's scaled up or anything, could it ?

Reply to
geoff

Oh dear, best not worry him then. To be honest my friend who owns this thing is in hospital too - getting gene therapy for pancreatic cancer... in Beijing!!!!

We have a few electric heaters in at the mo'.

Any idea where to get and what to ask for?

Could be, I don't think its been well serviced (well, there is a BG contract on it - nuff said ;) but no kettling noises from it.

Cheers Phil

Reply to
Phil Addison

In message , Phil Addison writes

YOu could ask Mark at Warmhouse,

01992 768686

He's very knowledgable but don't push it too hard IYSWIM

he's not someone who will spend time giving out free information

Reply to
geoff

I would expect it to be a simple mechanical type. probably one of those types that's a round black plastic bit about 12mm diam with a couple of tags for two spade connectors, and maybe to little screws to fix it in place.

Probably has loose bits in it, might even rattle when you remove it.

If the pilot drops out and you have no other info it migth be the bit you'd first try. Trouble is that BG send out a new technician each time so each one try a new thermocouple...

Its clearly

Boiler spares shop or online boiler spares (HRPC/ keeptheheaton maybe even Chaffoteau themselves).

Reply to
Ed Sirett

Thanks again for the info both Ed and Geoff. Armed with the knowledge its likely to be a simple fix I have bent the ear of BG and challenged their initial "you need a new boiler guv", and they are sending an engineer round friday afternoon. Yep, thats a 2 day wait on a recall, so much for the leaflet stuffed through my letterbox today saying "we come to 8 out of 10 calls the same day"!!

Will let you know what happens.

Phil

Reply to
Phil Addison

Just an update. The BrGas man came Friday, forgetting to call me 15mins in advance so I could meet him, duh!! but I did get speak to him on the phone. He said he DID replace the overheat stat along with the thermocouple "because they come joined together" huh? Anyway he reckons that now it must be the main thermostat that "has sort of gone out of calibration" and is coming back Monday to replace that. We shall see.

Meanwhile we got some oil-filled* radiators in, to keep the staff warm. Did you know that TLC sell them for several hundred pounds each, up to £1100 for what appears to some kind of 'designer' effort,

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yet also have a few quite decent 'normal' ones for under £30?
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* Friend was worried about fire risk from fan convectors being left on overnight by forgetful staff, probably quite rightly.

Phil PS We got the £30 ones LOL

Reply to
Phil Addison

That's plausible, this would not be a universal t/c but a custom one with a series connection to the o/h stat built in.

Anyway he reckons

That would depend on whether the boiler is actually over heating or not. You suggest that the boiler is not getting that hot. Anyway it's probably a NTC thermistor and would be the next in the frame. I would want to know what the REAL temperatures are that it's running at at the different setting levels.

Reply to
Ed Sirett

OK, I'll give or BrGas man benefit of the doubt on that one, shame he wasn't more specific on the job card. I should say I haven't had the chance to get my hands dirty on this one, as I'm having to stand back a bit so long as Br Gas are now conceeding that it should be repairable.

I just checked the manual ...

8.2 To replace the overheat thermostat

- Remove the two tab connectidns on the thermocouple leads to the overheat assembly.

- Remove two screws retaining overheat thermostat.

- Replace thermostat - use heat sink grease for better contact.

- Re-assembly in reverse order.

... but there isn't actually a "Replace thermocouple" section, so maybe Chaffoteaux only stock them as a pair.

Exactly, and no it wasn't getting particularly hot, that's why we got in the oil-filled rads. However, I didn't check the peak temperature the flow reached before it cut out - I'll take a thermocouple and IR thermometer down with me Monday in case our man needs convincing.

One thing I didn't mention before, they inspected it prior to taking on the 3* service contract 2 years ago, but the 1st guy that came the other day and saidt it was "too old" also stuck an "inadequate ventillation do not use" label on it. Wonder why they didn't notice that when they inspected it to take the contract on... duh!!

Phil

Reply to
Phil Addison

OK. That makes me think the O/H stat is exactly as I had imagined. The thermocouple+lead whilst having leads to the O/H stat very likely is NOT shipped with it. Does the parts list give any further clue?

Maybe because the replacement is a familiar task and/or obvious how it's done?

My suspicion that the O/H stat is dodgy is strengthening. I'd hazard a guess that when the O/H stat unit is removed you will be able to hear its innards rattle, in a way that the new one doesn't.

Reply to
Ed Sirett

Today's update:

BrGas came today and changed the main stat, and left leaving the boiler on max to heat up. He didn't have a thermometer and relied on hands-on to test the flow/return temps. Would you believe it shutdown (pilot out) after about 40 mins on full bore (the system was quite cold to start with). At this point I put my thermocouple on the flow to see what was happening....

Relighting the pilot with stat on max it ran up to 90C and then the main burner shut down. The pilot stayed on for 50 seconds then went out. I figured this was the over-heat stat shutting it down, but don't know what is generating the 50s delay.

I then turned the main stat down to about 80% and relit the pilot. Same result, it cut out at 89C, so I turned the main stat down to about 25% and re-lit. This time it cycled fine, reaching a max flow of 79/80C.

I now wanted to know how high I could turn the stat up before it went into overheat, so I increased it in steps. The highest I could go was

50% to 60% of full scale which gave a cycle of max 79/80C flow falling to 68C over 3 - 4 mins, then back up again.

Note that the main stat has its capillary sensor in the RETURN, which is correct according to the manual

2.14 Boiler thermostat Sopac AE 350 A 2.15 Thermocouple and thermoelectric valve (Chaffoteaux et Maury) The 24 blade stainless steel Chaffoteaux burner is fitted with 1.18 mm injectors. The non-adjustable permanent pilot is manually ignited by a piezo igniter. The boiler is controlled by an adjustable thermostat which is fitted into the return side of the monotube. The flow temperature measured on the flow side of the monotube will vary relative to the mass flow rate through the monotube but within the range 82C +/- 4C ( 180F +/- 7F) with a temperature differential between 11C min and 20C max.

The main stat that BrGas fitted today is different from the original, in a couple of ways. 1) Its control knob is 90 degrees rotated from the original so does not match up to the engraved setting scale (BrGas pointed this out. 2) the spindle is not perpendicular to the control panel, being canted over at some 15 degrees (BrGas did NOT point that out!!)

I take it that shutting down the pilot is normal correct operation on over-heat. This then leaves me with the main stat controlling the boiler OK, but apparently with a big shift from where it should be set. Or put another way the main stat is allowing the user to set a very high temp which will trip the overheat. Conclusion, the original stat was defective, and the one replaced today is the wrong one.

One other point, the engineer said that "if the new stat doesn't cure it, it must be the heat-exchanger blocked and that is not covered by the service contract".

Does this make sense? I'm sure it's not the heat exchanger because the water flow is fine and all the rads (lots of them) are getting piping hot so long as the over-heat doesn't trip. I have spoken with the service engineer since, stressing I'm not convinced about the heat exchanger and he is going to consult with his manager.

Ed, your advice so far is much appreciated, pointing me in he right direction.

Geoff, I don't think it is a PCB problem is it? I'm not sure it even has one!

Phil

Reply to
Phil Addison

Sounds like he put in whatever was in his van that would (almost) fit, Phil.

If you're BG, perfect sense.

Inadequate flow such as failing pump, heat exchanger can cause this - I've seen it.

Based on the replacement thermostat, something may well not be correct with that.

It sounds to me that he has fitted a thermostat intended to go on the flow side. That would explain why the flow temperature is exceeding what would be reasonable. A 25% setting on a flow side thermostat is probably in the 70 degree +/- range. Add the heat exchanger rise of 12-15 degrees or so and you have your flow side number.

You could take a look at the thermostat and check its part number then look up the spec.. While thermostats are generic, having something that doesn't fit in two ways mechanically and looks like it's doing the wrong job as well rings three alarm bells.

Let's see what Ed thinks, but I'd be escalating this with BG.

Reply to
Andy Hall

Hi Ed/Geoff,

I posted the previous before I saw this. Some comments below...

Have checked the parts list

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and it lists a combined "THERMOCOUPLE & OVERHEAT STAT" part number 507 and it DOES have a PCB, part number 2201, GC No. 366475, Manf Part No. 58100.

I meant the c/h rads were not getting that hot. I had not had a chance to measure the actual boiler temps.

It was already replaced by BrGas along with the thermocouple last friday so I didn't have the chance to rattle it. However, that did not fix the problem.

Please see other post for todays update.

Phil

Reply to
Phil Addison

It did come out of a new sealed box, but I take your point!

I didn't give 'em the service contract guv :)

I also asked when it was last cleaned. "Hang on it'll be on my laptop".... tap... tap.. "Ah, last Feb, its nearly due then"

Nearly???

Phil

Reply to
Phil Addison

But once I got it cycling at a respectable 80C flow all the rads got piping hot, and the boiler kept going on full bore for 40+ mins from cold so doesn't look like a flow restriction or dodgy pump.

Could well be. The parts list covers 2 similar boilers, but they do have different part numbers for the stat.

That's an idea... I'm a bit loathe to start taking things to bits to get at it though, at least while BG are still talking.

Will do if our engineer doesn't come back with a solution tomorrow.

Phil

Reply to
Phil Addison

Agreed, but /this/ boiler is vulnerable to any intentional or unintentional change in the primary flow rate. TRV's on a mild day may cause complete havoc.

The fact that it does not fit correctly and may be for a similar model but works in a different way is cause for concern. On older boilers, manuafactuers can and do 'upgrade' the spares and sometimes this leads to the 'correct' spare part not being correct and not fitting unless other parts are upgraded as well.

It is essential to get the right advice from the manufacturers.

I'm as pissed off with the design as with the service company.

Reply to
Ed Sirett

In message , Phil Addison writes

I thought it had a small two layer pcb, but ICBW

Reply to
geoff

Just to clarify by "our engineer" I meant the BG guy - I don't have any LOL!!

Phil

Reply to
Phil Addison

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