Lewden 100a switch fuse burnt out

weevilward · Jan 21, 2019

Has anyone had problems with this switch fuse??? I went to one last year which was warm to the touch, so I changed it for an Amd3 metal one. I found this one today burnt out, close call. The screw terminals were tight - the source of the heat looks to be the contact inside the switch. This one was less than 5 years old.

buzzlightyear · Jan 21, 2019

send it back ask for a refund .

weevilward · Jan 21, 2019

buzzlightyear said:
send it back ask for a refund .

Fair point but I’m thinking bigger picture - if these things are cooking off like this on a regular basis then the manufacturer needs to know before a house goes up.

Deleted member 26818 · Jan 21, 2019

Is that split con?

weevilward · Jan 21, 2019

spinlondon said:
Is that split con?

Is what split con?

buzzlightyear · Jan 21, 2019

weevilward said:
Fair point but I’m thinking bigger picture

what cinema type or tv or picture on the wall .

weevilward · Jan 21, 2019

spinlondon said:
Is that split con?

The cable coming out of the terminal is PVC/PVC 25mm tails

buzzlightyear · Jan 21, 2019

weevilward said:
Is what split con

a person that works in a circus like trapezes artist .

freddo · Jan 21, 2019

The terminals are a bit pathetic on these and the Twist Wiggle And Twist method and a large slotted screwdriver is essential to get these terminals tight. I have been to several where the terminals have been loose. IIRC the screw is made of a different metal to the terminal which is never a good idea, but I could be wrong.

The Ghost · Jan 21, 2019

Maybe that spring holds the connection and loses it's temper when heated thus relaxing the contact? But yeh, agree the manufacturer should be apprised of this failure.

Wilko · Jan 22, 2019

Looking at the pic, it does seem to show there has been molten metal flying about, with deposits and some erosion. Out of interest, was the unit installed somewhere damp?

weevilward · Jan 22, 2019

Wilko said:
Looking at the pic, it does seem to show there has been molten metal flying about, with deposits and some erosion. Out of interest, was the unit installed somewhere damp?

View attachment 47329

No, bone dry, inside a fairly modern, heated house

freddo · Jan 22, 2019

I wonder which started first, the contact erosion could have started after everything got hot from a loose cable connection and the switch contact moved position when the plastic melted/burned.

I have seen other problems with the metal Lewdon 100A switch fuses, went to look at a fault at a pub/restaurant that only had a single phase supply, a large distribution board was connected via the switch fuse. This was new and had been fitted 6 days earlier by another company as the old switch fuse burnt out. I was called to 'check the electrics' as the cutout fuse had blown. Looking in the new switch fuse the connections were all loose and one of the new 25mm tails was clearly heat damaged. I don't believe the terminals were left loose by the installer but had worked loose from the heavy thermal cycling. The brass terminals the installer fitted the tails to in the 4 100A blocks, including the 2 new ones he fitted to cut out the heat damage from the outgoing tails were all tight.

With the power on I measured 141A being drawn and the wiring and fuse soon started getting hot.

MJPD29 · Jan 22, 2019

Did you get a chance to clamp the cable and see whay kind of power it was drawing?

weevilward · Jan 22, 2019

Matthewd29 said:
Did you get a chance to clamp the cable and see whay kind of power it was drawing?

No I didn’t, but that’s a good call. I’ll put the clamp meter on in max/min mode and see what it gets to. It was an all electric 4 bedroom house (underfloor heating throughout) on a cold frosty morning with the lady at home running appliances. Could be a big number.