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T

TPES

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Simple quick question

Im going to put a new feed to a boiler, into a switched spur as it is now..

The cable being used at the moment is black rubber flex with a 3a fuse. (not sure if this was done right in past)

What size cable do i replace this with..?

Is 0.75 heat resistance flex Ok on a 3a fuse? or does it have to be bigger csa?
 
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R

randyrat

  • Thread Starter Thread Starter
  • #2
Normally a 5A switch fuse supplying a (modern) combi boiler. Heat res flex only really needed for Immersion Heater supply...most modern boilers are "cool touch", negating the need for a heat resistant cable.
hope this helps
Randyrat
 
R

randyrat

  • Thread Starter Thread Starter
  • #4
Oops....forgot to answer the question.....
Depending on factors such as ambient temp etc which derate the supply cable, as a rough guide a 1mm cable will cope with 15.5 amps clipped direct...plenty!! Obviously if its a hundred yards long through insulation you need to perform the full calcs to determine current carrying capacity. If in doubt go large!!!!
 
M

maddfridge

  • Thread Starter Thread Starter
  • #5
Simple quick question

Im going to put a new feed to a boiler, into a switched spur as it is now..

The cable being used at the moment is black rubber flex with a 3a fuse. (not sure if this was done right in past)

What size cable do i replace this with..?

Is 0.75 heat resistance flex Ok on a 3a fuse? or does it have to be bigger csa?

hi there

small world a city and guilds design project has this in it !
i have run to the spur in 2.5mmm2 but from the spur to the combi is left to the designer

answer look at the manufactureres installation instructions


cheers
 
N

nick182

  • Thread Starter Thread Starter
  • #6
hey guys

what cable size/type would u use in a plug point for a boiler? I have a friend installing a boiler and shes asking for a plug point up in her loft? Wanted to know if i could help.

thanks..

nick
 

polo1

-
Arms
See the comments above. Size the cable(flex) in relation to demand info. Preferable to have heating supply on it's own radial to a SFS, appropriately fused, not off a RMF.
Regards.
 
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