1.25 flex of a 13 amp fused spur feeding a 3KW immersion heater

[Jako13!]

How tight is it running 1.25 flex from a 13 amp fused spur feeding a timer for an immersion heater?

 

[Dave OCD]

Firstly I'd say you shouldn't be using a 13a FCU as it's right on the limit with a 3kW Immersion heater - much better is a good quality 20 amp DP switch and it should be fed via a dedicated 2.5mm circuit from a 16a MCB or RCBO. As for the flex, 1.5mm minimum.

 

[pc1966]

1.25mm is on the limit for 13A anyway, more so in a hot area so I would also go 1.5mm

Agree with the FCU, not needed for a dedicated circuit anyway, and an indication it might be off a RFC which is not good practice.

 

[Dustydazzler]

1.25 is a fairly non standard size imo which is usually found on extension leads and 4 way plug adaptors etc

1.5 should be used for fixed hook ups like immersions and storage heaters imo

 

[brianmoooore]

Should be 3093Y (heat resistant), not 3183Y. (Plus everything above.)

 

[pc1966]

1.25 is a fairly non standard size imo which is usually found on extension leads and 4 way plug adaptors etc

Only for post-FCU use where not "fixed wiring"

1.5 should be used for fixed hook ups like immersions and storage heaters imo

Agreed!

 

[Jako13!]

Thanks guys it’s run on a 16amp radial then a 13amp FCU where the 1.25 flex goes into a timer then into the immersion heater?

 

[brianmoooore]

If it's on a 16A circuit, then the fuse in the FCU is not required, so the FCU should be replaced by a 20A DP switch. A 13A fuse will run hot feeding a 3kW immersion heater, and the plastic of the FCU will be damaged over time.

 

[Jako13!]

If it's on a 16A circuit, then the fuse in the FCU is not required, so the FCU should be replaced by a 20A DP switch. A 13A fuse will run hot feeding a 3kW immersion heater, and the plastic of the FCU will be damaged over time.

Cheers Brian I thought overload protection wasn’t required. Looks like these were initially installed like this.

 

[Jako13!]

So best option is to replace the flex to 1.5 and replace the FCU with One of these?

 

[brianmoooore]

That will do fine.

(There's a silly rule on here that posts must be at least 25 characters long.)

 

[Jako13!]

So is this an occasion where regulation 433.3.1 comes into play? I will make this 25 characters long to comply with these rules. Just about 25

 

[littlespark]

So is this an occasion where regulation 433.3.1 comes into play? I will make this 25 characters long to comply with these rules. Just about 25

You were at 25 characters at the “e” of “regulation”
25 words would be longer.

I’m not sure what this limit achieves…. Apart from stopping someone spamming threads with one letter posts just to be annoying.