Cut through boiler cable next to the watertank.

colin jesson · 20 Jan 2018

Anyone, please advise what I may have damaged

I was cutting screws under the skirting board next to the water tank airing cupboard to find myself cutting through the blue wire of the 4 core 1mm cable, this tripped the boiler 3amp fuse and the boiler cut off.

I replaced the cable but now the boiler light is solid red. Lockout mode. I can confirm I have double check the wiring and everything is as it was before and terminated correctly.

I fear I have damaged part of something.

What could I have missed or done.

Before I get an engineer out us there anything I can do?

stem · 20 Jan 2018

You don't give any details of your boiler, but some reset automatically after a lockout, some have to be manually reset. It sounds that yours may be the latter. Check your boiler manual for details of how to reset it manually.

colin jesson · 20 Jan 2018

Hi

Its a potterton suprima 30 40 or 50

I have held the reset button for 10 seconds. It then goes orange then stays flashing red (flashes red 5 times repeatedly)

I then hold the reset button for 5 seconds, it goes back to solid red. Lockout.

stem · 20 Jan 2018

Hmm. Usually suggests a problem with the overheat. Turn the thermostat knob to minimum / off. The lockout light should go out. Now turn it back up and the boiler should fire up.

colin jesson · 20 Jan 2018

Hi the red light is still on

stem · 20 Jan 2018

Sorry then, that's me out of ideas.

colin jesson · 20 Jan 2018

Thank you. I was hoping that would work.

Thanks for your help

colin jesson · 20 Jan 2018

I do wonder if this could have damaged a component on a circuit board or blew the pump somehow?

I would be great if nothing was damaged but I can't clear the lockout for some reason

colin jesson · 22 Jan 2018

Hi Stem

I will be calling the boiler engineers shortly.

One thing that I'm not sure about.

Is seems the fuse was blown from a small nick in the blue wire (return from pump), is this possible?

Thanks

stem · 22 Jan 2018

A fuse blows when an electric current exceeding the rating of the fuse flows through it. To achieve this you would have needed to create a 'live to neutral' or 'live to earth' short circuit.

A live to neutral short circuit would occur for example if you had made contact between a live conductor and neutral conductor. With heating system wiring, a blue wire is not always used as a neutral, sometimes it is used as a live conductor.

A live to earth short circuit would occur for example if you had made contact between a live conductor and earth conductor, or live conductor and an earthed object such as a power tool, or metal pipes.

colin jesson said:
Is seems the fuse was blown from a small nick in the blue wire (return from pump)

Just making a "nick" in a single cable without making contact with anything else wouldn't blow a fuse, as no current would flow.

colin jesson said:
to find myself cutting through the blue wire of the 4 core 1mm cable

Also, you sure that you have remade all of the connections correctly? The pump only has L, N & E connections, so doesn't require a 4 core cable.

endecotp · 22 Jan 2018

Are there any additional fuses on the boiler PCB?

stem · 22 Jan 2018

Oooh be careful, you will get into trouble for suggesting that the OP starts tinkering with his boiler internals.

John D v2.0 · 22 Jan 2018

stem said:
Just making a "nick" in a single cable without making contact with anything else wouldn't blow a fuse, as no current would flow

My only comment on your otherwise excellent post is that in this case the blade of the cutter may well have been earthed through the mains lead. Not all are II equipment, so cutting into a live conductor would create a live to earth short.
Edit: of course I did just assume the OP was using a mains powered cutter rather than a hacksaw!

Also the op should confirm the other core isn't used for something else eg tank thermostat or zone valve.

stem · 22 Jan 2018

John D v2.0 said:
the blade of the cutter may well have been earthed through the mains lead.

Isn't that the same as:

stem said:
or live conductor and an earthed object such as a power tool.

John D v2.0 · 22 Jan 2018

stem said:
Isn't that the same as:

Didn't spot that one

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Cut through boiler cable next to the watertank.

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