Burnt out water heater switch

DavyWavy · Mar 5, 2019

Hi all, just joined EF hoping to solve a problem. I live in a 3 year old flat in a block and my immersion heater stopped working. I have discovered the problem to be a burnt out switch (photo attached). As you can see it's pretty bad to the extent that the plastic has melted. My question is why should this happen, especially in a modern property? Cheers, Dave

[ElectriciansForums.net] Burnt out water heater switch

Midshires · Mar 5, 2019

This really should never happen. Where did you get from, when and what's the make?

westward10 · Mar 5, 2019

Could be a number of things, poor connections, poor quality accessory who knows. Unfortunately modern day accessories are not the same quality of years past and a 13A fuse connection unit is not ideal for an immersion heater and you should replace it with a 20A double pole switch.

westward10 · Mar 5, 2019

Midshires said:
This really should never happen. Where did you get from, when and what's the make?

This is true but unfortunately modern day 13A fuse connection units whoever manufacturers then do not like being pushed to their limit. In the pic the fuse carrier part appears to have melted and this could purely down to a poor connection.

DavyWavy · Mar 5, 2019

Thanks for the replies. I should say that I bought the property brand spanking new from one of the biggest developers in the country! So the switch is original! The wiring used in the photo is made up of strands.....is this ok or should it be a single core? Cheers, Dave

westward10 · Mar 5, 2019

I assume they are the outgoing conductors so they should be okay but remove any damaged parts. Strip them back, fold over and ensure the terminal screw hits a good connection to them.

telectrix · Mar 5, 2019

the outgoing cable will be stranded flex. looking at the offcuts in the pic. it's not been ferruled, which in itself is a recipe for burnt terminals. and as previous, a 20A D/P switch is preferable . overload protection should be 16A MCB in CU.

Pete999 · Mar 5, 2019

DavyWavy said:
Hi all, just joined EF hoping to solve a problem. I live in a 3 year old flat in a block and my immersion heater stopped working. I have discovered the problem to be a burnt out switch (photo attached). As you can see it's pretty bad to the extent that the plastic has melted. My question is why should this happen, especially in a modern property? Cheers, Dave
View attachment 48159

Loose connection would be my diagnosis, Hercule is my middle name

telectrix · Mar 5, 2019

Pete999 said:
Loose connection would be my diagnosis, Hercule is my middle name

or maybe a melted ~~fuse~~ nail carrier.

Silly Sausage · Mar 5, 2019

DavyWavy said:
I should say that I bought the property brand spanking new from one of the biggest developers in the country!

You're equating 'Modern' with quality, reliability, and other positive attributes.
Not necessarily so!

telectrix · Mar 5, 2019

DavyWavy said:
Thanks for the replies. I should say that I bought the property brand spanking new from one of the biggest ~~developers~~ throw it up in a week as cheap as possible in the country! So the switch is original! The wiring used in the photo is made up of strands.....is this ok or should it be a single core? Cheers, Dave

corrected that for you.

DavyWavy · Mar 5, 2019

Haha, get the point

but nevertheless a 3 yr old property - this could have been a lot more serious than no hot water for a while! So basically can we say that stranded wire, folded over, (un-ferruled), tightened securely in a 13A D/P switch should be ok?

Pete999 · Mar 5, 2019

telectrix said:
or maybe a melted ~~fuse~~ nail carrier.

Yes depends what was in the carrier, seen some real disasters waiting to happen, live 0.22 bullet.

Wilko · Mar 5, 2019

Hi DW and Welcome.
Unfortunately we do see these 13A fuse connection units that have been heat affected. Can you check if the circuit the FCU is on has a B16 rated mcb? I'm suspecting they've put yours off a 32A circuit and so felt they needed to fuse it down.

telectrix · Mar 5, 2019

DavyWavy said:
Haha, get the point but nevertheless a 3 yr old property - this could have been a lot more serious than no hot water for a while! So basically can we say that stranded wire, folded over, (un-ferruled), tightened securely in a 13A D/P switch should be ok?

yes. now the thread has been answered, here's a bit of culture: