which 3 core flex for combi boiler?

[RMB]

I have a Potterton 28i combination boiler.It is rated at 230v and has an
external 3 amp fuse(in the FCU/fused connection unit)with power consumption of 190w.I need to replace the 3 core flex which leads from the FCU to the combi boiler with a longer one.I had assumed I would need a 3amp 3 core flex-but the one already on it is far thicker than this-more like a 13-15amp flex.Is this due to the heat generated?Is it safe to use a thicker one?

 

[Steve]

Not much heat generated, i think its thicker partly because it looks better than the thin flex (being such a big appliance, it looks like a bodge with a little tiny flex supplying it!) also theres the issue of wear. thicker wire is going to take knocks better. I may be wrong, but i wouldnt like to see a big boiler wired up in bellwire!!

 

[RMB]

Thanks for that Crafty-but does this mean I can use a thicker 10 amp or 15 amp flex(even though the external fuse is only 3 amps).I know you can't use a lower amp flex but is there any danger in using a higher amp flex/cable in electrical jobs in general?

 

[securespark]

No, there isn't. As long as it is the correct type of flex, and you can physically get the conductors into the terminals, you can use a larger CSA (cross-sectional area).

It could well be that the flex on your boiler at present is HR (heat-resisting), and that would explain the diameter.

Have you got the manual? If not, ring Potterton and ask what sort of flex it recommends.

If you cannot get mfrs advice, I would play it safe and plump for .75 or 1.0mm2 3 core HR.

 

[RMB]

Thanks to both of you for the advice!