Boiler won't ignite after pilot light relit

[jkn]

Hi All we have an old Baxi Bermuda back boiler (yes, needs replacing, but not now...). I recently got a new gas hob fitted and after the chap left, realised that of course the pilot light for the boiler had gone out.

Then has followed some messing about to get it to re-light; this took a long time until I noticed that the wire had come away from the crimp connector at the back of the spark generator. I have recrimped this and have got the pilot light running fine.

However, now the boiler does not fire when hot water is needed! Mains power is going to the controller unit (Sunvik Select 207 XL), and the controller LEDs indicate that the hot water should be on. I can also hear the relays clicking.

Any suggestions as to what might be the trouble? I can understand something failing in this ancient setup but it seems strange to have occurred just at the same time as the pilot light had to be relit. I am next to certain that I have not disturbed any wiring...

Thanks Jon N

[jkn]

Good question, but yes ... I turned the knob from 'Off' for lighting, to '2'. I also tried it at 'High'...

Jon N

[jkn]

Update: I've checked the mains going into the boiler - there's a 2-pole connector - and that seems to be at 240V when expected (controller heating ON). So it is looking like a solenoid/gas valve problem ;-(.

I still don't really see why having the pilot light off for 24 hours would have caused this to fail, though...

Jon N

[Graham.]

On these gas valves you normally have to hold down a bypass button for (at least) a few seconds to allow the thermocouple to heat up in the pilot flame.

Can you do this test? Turn of the pilot and give it a couple of minutes to cool. Now ignite the pilot in the approved manor, except release the bypass button immediately.

Does the pilot stay lit? does the pilot flame go smaller when you release the button?

If the answer to either or both is yes I would suggest that your thermocouple needs changing.

A faulty thermocouple will certainly prevent the full rate gas being passed to the burner, and in theory it should stop the pilot flame too, but I have seen old gas valves that let-by a trickle of gas to the pilot jet in this condition.

Apart from that, in my experience, a thermocouple that has been immersed in a flame for a year or more is almost guaranteed to fail when the supply is interrupted. That was the main reason I gave my gas supplier the heave-ho when they threatened to come round with a "Smart" meter.

I should add that I am not a plumber or a gas fitter. (But I did share a Union with them in the 70s EEPTU)

[John Rumm]

Note I am assuming here that the gas valve itself is a typical mains driven one. I would start with by checking (with a multimeter) that mains does actually make it to the input terminals of the valve when there is a call for heat. Chances are you just have a loose connection somewhere. The mains feed to the valve may also pass through the boiler's internal stat. So that would be the next thing to check if you are not seeing 240V at the valve.

[Mr Pounder Esquire]

I used to install the Bermuda when I was an apprentice------------- nearly

50 years ago. The thermocouples used to fail regularly.

[jkn]

Yeah ... as per my earlier post the mains does get as far as the input to the boiler, I haven't yet checked that it gets any further. It is certainly worth me trying to see it it gets to the stat.

Should it be possible for me to hear the solenoid when the ma> On these gas valves you normally have to hold down a bypass button for

For my clarity; are there one, or two, thermocouples in these sort of things? From what I could see and imagine I'd expect one for monitoring/controlling the pilot light, and one for full ignition.

Hmm, interesting, thanks.

;-)

I am going to be away for a few days so won't have chance to look at this until I get back. Will try to post a report later.

Cheers Jon N

[John Rumm]

That's always a good start ;-)

I would just stick your meter probes on the live and neutral going to the gas valve. Check that goes live when there is a call for heat. If they don't go live, then check the boiler wiring and internal stat. If they do go live and the boiler does not fire, then its probably a knackered valve.

On the gas valve itself? probably not. However there may be a relay in the control board (if there is one) for the boiler that you can hear.

Normally there is one thermocouple, that feeds the pilot valve on the gas valve. So you hold the button down and light it, and once the thermocouple it hot and producing volts, that should be enough to hold open the pilot part of the valve.

There will likely be a secondary stat driven from a bottle style thermocouple that is sat in a pocket in the main HE, that is used to interrupt the mains feed to the gas valve when the maximum HE temperature is reached,

[John Rumm]

Should have said earlier, but I have the installer manuals for all of the Bermuda models here. Drop me an email with the exact model and I can send you a copy if it would help.

[Alan Dawes]

I have a Gloworm Majorca 2 back boiler of about the same vintage (I installed it in 1976) which on 2 occasions since then has failed like your boiler. In both cases it was the inline fuse that had failed. The holder was not obvious as it was tucked away behind the control box. It held an old 1 inch fuse which luckily I still had some spares that had come with the original boiler.

Alan

Alan

[jkn]

That's interesting, thanks. Do you mean the 'control box' (Thermostat assembly?) on the back boiler itself? I wondered about this, but haven't yet got around to checking the mains beyond the small 2-pin socket going into the fire (been away for a few days). There is mention of a fuse in some of the installation/service manuals, but no indication of where it might be ...

Thanks Jon N

[John Rumm]

Talking of two pin sockets, that reminds me...

I got asked by a mate to work out why a back boiler was not firing. Having checked through all the controls I took a close look at the fire. The mains input to it was via a plug on the underside that the installer had wired with a bit of 1mm T&E. It was stiff enough over time to pull the plug out the socket. Simply reaching under the fire (who designs a socket to go on the underside of these things?) and pushing it back in was enough to restore normal operation.

[jkn]

Hmm, interesting...

I checked the output of the Thermostat and there was mains going to the valve when the demand was on.

So I replaced the thermocouple (a pattern part replacement, bought earlier, in anticipation). This proved to be fairly straightforward.

FWIW the old thermocouple looks pretty pitted and worn at the end ... the tip of the new one (a pattern part replacement) perhaps sticks out a touch beyond the pilot light...

Anyway, replacing the thermocouple has made some difference ... now when I turn the heating on, the main boiler does not ignite - but there is a quiet background 'whooshing' noise, similar but quieter to the noise you get when the thing does ignite. I didn't leave it for too long before turning the demand off. This semi-familiar noise was not there before I replaced the thermocouple.

I wonder if there may be a blockage in the main injector, or perhaps the solenoid is half-opening, or something ... any thoughts? I realise I'm getting to the edge of my competence here and am unlikely to go much further myself, unless I'm missing something obvious.

Cheers J^n

John Rumm wrote:

[jkn]

Replying to my own posting:

curses - looks like the 'whooshing' noise was because my good lady wife, when asked to turn on the heating, did just that - turned on the hot water AND the heating. I think the 'whooshing' noise was actually the CH pump circulating (cold) water.

I think I may have to get a man in - Grrr...

J^n

jkn wrote:

[John Rumm]

;-)

It sounds like if you have a pilot that stays on once lit, then the thermocouple is fine. If you can measure mains at the input of the gas valve when the demand is on from the room stat, then the control wiring and internal thermostat and fuse etc are also fine. That leads us to the conclusion that the gas valve is knackered.

[jkn]

Yep, that was pretty much the conclusion I had come to. Just weird how it coincided with the supply being cut off. I see that the Honeywell valve models used on this boiler are relatively cheap on eBay; I may look into that option.

Thanks for your on- ad off-line help with this.

Cheers Jon N

[John Rumm]

What model valve is it? (I have a spare in my workshop that came out of a working ideal mexico)