Horrific Taped Hager MCB

[mart64]

Hi... (must change my location back to UK..)

My friend has a small Hagar Consumer Unit in her flat (RCD on left, somewthing weird like a relay in the middle and MCBs on right with main ON/Off at the far end.

When we first started in the flat I turned on a wall switch (with a power light) that fed a plain wall socket nearby. The switch made a loud bang and there was a big flash! So i turned of the power in the consumer unit and turned the switch off again. i looked at the consumer unit and noticed that 3 of the mcbs were covered in tape so they couldn't trip, and when i removed the tape two mcbs stayed on but the third tripped and won't stay untripped. Its a Hager MT132 mcb that seems to feed the central heating boiler, the lounge ring and possibly the kitchen ring as well. This mcb has been forced "on" for ages as we have been testing the central heating so this situation must have existed for a while. How dangerous is that!!

I removed both the wall switch and the socket to look for any damage from the (i assume) short or general damage to the wires.. None can be seen. Is there a test i can do on the circuit supplying the wall switch that blew or is this really a job for an electrician?? Even with the wall-switch off the mcb still trips!

Thank for any help...

Martin.

 

[Spark123]

I think you'll find MCBs have a trip mechanism that stops them from being held on. At least the UK ones do!!

 

[solair]

You may find that some of the older ones don't have that mechanism and can be held up. Depends on the age of the installation.

However, that is really dangerous! The place could have burned down.

 

[bernardgreen]

You may find that some of the older ones don't have that mechanism and can be held up. Depends on the age of the installation.

However, that is really dangerous! The place could have burned down.

You may find the previous owner had taped them in the OFF position because there was a fault.

 

[Spark123]

You may find that some of the older ones don't have that mechanism and can be held up. Depends on the age of the installation.

However, that is really dangerous! The place could have burned down.

I've not seen any MCBs like that, wouldn't they be very dangerous if one was closed under fault conditions? Firstly it would probably try to take your fingers off as it attempted to open in 0.1s, secondly you could wrestle against the mechanism until your house burned down...

 

[RF Lighting]

Even crabtree C50s wouldn't stay on with the lever jammed.

The OP is no different from a fire alarm supply being locked 'ON' (It can't be isolated without a key, but will still trip if a fault occours)

 

[mart64]

Thanks for all the comments...

On examination I can see no damage to the switch or socket although the earth wire wasn't tight in the switch. So far we have put the switch back into the wall along with the socket having made sure the connections were good. I think the switch etc.. is on a spur put in by a previous owner.

The mcb that tripped stays off even with the main power to the board off, so is that an indication of a faulty mcb? I can hold the mcb to the ON position and the boiler comes on and all the sockets on the ring come live. It doesn't remain tripped if held ON.

So im thinking that as these mcbs are reasonably priced maybe i should try getting a new one. I assume i should get a proper Hager one not another make... and also I assume i can fit it ok. I have seen the Hager instructions so it seems easy enough...

I was so worried about the stupidness of taping the mcb in the ON position.. What a daft thing to do!!!

thanks... Martin.

 

[Spark123]

If it won't hold up with the main isolator off then it is almost certainly broken and requires replaced.

 

[mart64]

Hi...

Well the last comment clinched it. Bought a Hager MTN132 mcb and replaced the apparent faulty one.. Success...!!

Really had never changed one so was nervous about the process, but actually no problems. I suspect the blown switch was coincidence unless its related to the damage to the old mcb! Im sure time will tell...

Thanks very much everyone.