Not something I’ve seen before…

[CBW]

I attended this today, boiler fitted approx 6 months ago, not working. After some initial investigation I found the mcb had tripped. Replaced the 3 amp fuse and tried again - pop goes the fuse and mcb again.

Checked inside the boiler for wiring, not the best and thought it must be a strand touching. Put connections into a wago, reset mcb and new fuse still went pop. Removed face plate for fcu - couldn’t see any wiring issues, removed receiver and presented with scorching between 2 Live terminals? Photo attached - any ideas? I’ve sorted the boiler, just wanted feedback as to if anyone knows why this has happened? Could it be the short link? - it’s L to L though

Thanks

 

[pcaouolte]

The scorching looks historic, there isn't any insulation damage on the red link wire (unless you fitted that?).

Is it possible that there was an OpenTherm module in that space and someone blew it to pieces by applying mains to it?

Edit: No, I'm wrong with the OpenTherm module guess, the BDR91 doesn't seem to be offered with anything in that space.

 

[CBW]

Yes - opentherm not supported by new or previous boiler. Scorching is definitely only last day or so, afaik, because it stopped the boiler working. Only way I could get the boiler working again was to remove the thermostat, and the red link wasn’t me (but was a colleague) - I’m not that rough.

Edit: The receiver is the same age as the boiler.

 

[BlueLoo]

Do you see the loose copper strand in the 1st photo (neutral)

 

[JohnW2]

Do you see the loose copper strand in the 1st photo (neutral)

....and isn't there also a loose strand from the L conductor, perilously close to the one on the N conductor? ...#

Kind Regards, John

 

[BlueLoo]

Round of applause to @CBW for not leaving the customer in the lurch and doing something to keep it going!

 

[CBW]

Round of applause to @CBW for not leaving the customer in the lurch and doing something to keep it going!

Thanks @BlueLoo - it’s not in my nature, and we’re not really allowed (who I work for).

 

[CBW]

Do you see the loose copper strand in the 1st photo (neutral)

Yes I did

Checked inside the boiler for wiring, not the best and thought it must be a strand touching.

 

[CBW]

....and isn't there also a loose strand from the L conductor, perilously close to the one on the N conductor? ...#

View attachment 325257

Kind Regards, John

Yep, spotted that however:

Checked inside the boiler for wiring, not the best and thought it must be a strand touching. Put connections into a wago, reset mcb and new fuse still went pop.

Also, why would the scorching happen at the receiver end?

 

[BlueLoo]

I propose:

The owner had a ****ty wire connector in here to provide a link/240v somewhere else and this shat itself because it was arcing or something then it gave up the ghost causing the heating to stop at which point the owner removed the evidence for fear of the damage voiding the boiler warranty and call you out.

"No idea mate, it was working ok and then i went for a dump and come back downstairs and it was a bit pearl harbour and then i looked at the boiler and it was off.." ...

 

[CBW]

I propose:

The owner had a ****ty wire connector in here to provide a link/240v somewhere else and this shat itself because it was arcing or something then it gave up the ghost causing the heating to stop at which point the owner removed the evidence for fear of the damage voiding the boiler warranty and call you out.

"No idea mate, it was working ok and then i went for a dump and come back downstairs and it was a bit pearl harbour and then i looked at the boiler and it was off.." ...

Nope, social housing (so countless free calls) and she’s an oap so I doubt it. It was our gas installer engineers who installed the boiler wireless thermostat and completed the wiring. Even if they had tinkered with it, it wouldn’t explain the fuse popping/mcb tripping afterwards.

 

[hovertoast]

I guess the receiver is broken? In which case, my money is on a component in the receiver failing, stopping the boiler working and also causing the scorching you see.

 

[RandomGrinch]

Only way I could get the boiler working again was to remove the thermostat,

As @hovertoast suggests, when you say you got the boiler working again, by removing the thermostat - does that mean the trips stopped when the stat was removed, or did the trips stop before, and removing the thermostat allowed the system to operate?

 

[CBW]

As @hovertoast suggests, when you say you got the boiler working again, by removing the thermostat - does that mean the trips stopped when the stat was removed, or did the trips stop before, and removing the thermostat allowed the system to operate?

It only worked/stopped tripping after removal of the receiver wiring, once I reinstated the boiler to the spur (rewired and managed to wire it up to previous ebus thermostat left on the wall). Like I said, it tripped whilst in the Wago connectors, so conclusion must be the receiver had become faulty somewhere, causing a dead short.

 

[RandomGrinch]

so conclusion must be the receiver had become faulty somewhere, causing a dead short.

It may be worth metering the resistance between N and the other terminals - hopefully you haven't got a batch of these that have some sort of defect, or you may be getting a few more call-outs...