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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> Help with fuses - cooker and hob https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1158230173 Message started by tspkd on Sep 14^th, 2006, 11:36am

Title: Help with fuses - cooker and hob
Post by tspkd on Sep 14^th, 2006, 11:36am

Hello - any help appreciated!!

I took out my oven and hob out the other day - both were connected via separte wires (10mm, double insulated) to a junction box and then on a circut run to the main fuse board in my flat, where they have a 30a old style fuse (ie with the wire) with a switch above the hob, which turns them both on/off.

I have not installed my new oven/hob yet as - My new hob says that it needs a 30a fuse (so this is fine - i have also checked the width of the existing wire, and this is fine also)

But my new oven says 20a max! My question is - would it be better to a) replace the fuse with a 20a and then hope that i dont blow it when i turn on the hob
or
b) have an electrician come round and run a separte wire to the fuse box + a new junction box to accommodate my new requirement of the 20a fuse for the oven
or
c) put them on the existing 30a fuse - but im assuming this may harm my oven as this says 20a max?

Is there some other way this could be done?

Thanks in advance anyone out there!

Jim :-? ::) :-/

Title: Re: Help with fuses - cooker and hob
Post by CWatters on Sep 14^th, 2006, 2:52pm

Putting in a higher fuse than specified will not harm an appliance in normal opperation but...

Hob = 30A
Oven = 20A

So both on at once could potentially draw 50A. That would blow a 30A fuse.

You need to wait for a reply from someone else more familiar with this and the regs than I am. They might suggest changing the fuse to something better and can comment on the suitability of the existing wire.

Title: Re: Help with fuses - cooker and hob
Post by tspkd on Sep 14^th, 2006, 3:34pm

Thanks for your input - looking forward to hearing from someone else...
::)

Title: Re: Help with fuses - cooker and hob
Post by sparkyjonny on Sep 14^th, 2006, 4:39pm

With diversity & common sence, 40A / 45A for the both sounds suitable. If it's an old Wylex board replace the fusecarrier & its socket with a 45A (green) plug-in circuit breaker. 10mm will easily handle this. As this is protecting the cable all the way to the appliance you must keep the final cable runs from the junction to the appliances at 10mm, otherwise these may need fusing down individually.

Title: Re: Help with fuses - cooker and hob
Post by tspkd on Sep 14^th, 2006, 4:55pm

Thanks - does it not matter that the oven says 20a fuse max? Im worried if i fuse above this then then oven may get damaged if i crank it up, or am I being really thick? :-?

Title: Re: Help with fuses - cooker and hob
Post by sparkyjonny on Sep 14^th, 2006, 6:12pm

That's usually to protect the supply cable - did it come fitted with 2.5mm flex or something? There's a chance that 20A is specifyed to protect the internal controls or cabling though, but it's usually just as the max demand of the appliance will not exceed 20A.

Title: Re: Help with fuses - cooker and hob
Post by tspkd on Sep 14^th, 2006, 7:11pm

No flex, just stated 15a min, 20a max.

I need to cook a pizza tonite (lass coming round), i think ill wire it up and hope for the best.

It's my only option ;-)

Thanks!

(more advice welcome)

Title: Re: Help with fuses - cooker and hob
Post by CWatters on Sep 14^th, 2006, 8:15pm

Just a quick check on something...

You said:

>both were connected via separte wires (10mm, double insulated)
> to a junction box and then on a circut run to the main fuse board
> in my flat

It is 10mm all the way back to the fuse board not just from the appliance to the junction box :-)

Title: Re: Help with fuses - cooker and hob
Post by tspkd on Sep 26^th, 2006, 11:21am

Hi

Yes, pretty sure it's all the ways back to the board...should i run with the 40-45a?

Title: Re: Help with fuses - cooker and hob
Post by CWatters on Sep 26^th, 2006, 2:42pm

Yes. What SJ says.

Putting in a 40A circuir breaker (rather than a 20A) doesn't cause more power to be delivered to the the appliance - the appliance only draws the current it needs.

Title: Re: Help with fuses - cooker and hob
Post by baz on Sep 29^th, 2006, 11:54pm

If you have a 30A fuse in the board then its a fair bet that the cable from the board is 6mm² not 10mm². You must not change the fuse for a higher rating. Get a competent electrician in to check it out.

Although your two appliances could theoretically draw 50A they probably wont. There's a thing called diversity. From your description I would expect the diversity calc to arrive at 30Amps (10 + 10 + 30% of 30 for those 'in the know').
Mind you, it could be more than that, depending on your utilisation - like Xmas day, when its all going full belt.
You are probably OK for now but take on site advice.

Bazza