Fuse size

[Jimmyb]

Just wondering after doing a job today, what is samllest fuse size you would use for sockets in a kitchen if there wasnt a washer or dryer in there ?
I put a 32a mcb with 4 double sockets and a single and when all finshed i did think with the loads present surely a 25 or 20 mcb be ok. I always had drilled into me 32 for kitchen no less for years even if there is no big app.

 

[i=p/u]

get away with a 20A radial if you wanted

 

[Jimmyb]

get away with a 20A radial if you wanted

i did think so but old habbit die hard

 

[i=p/u]

it depends on the loads, its like everyone says you have to use 6mm for a cooker circuit. you dont

 

[Jimmyb]

I do like 6mm for cookers tho cos i always think someone will install a hob and oven at a later date and say ive put loads of hobs and oven on the cooker circuit and it been fine for years.

I do always run 2.5mm for ovens and 4/6mm for hob on rewires now just because i think it better to have them seperate

 

[i=p/u]

my lecturer said to me use diversity in your favour to win jobs back in 1st year

 

[Engineer54]

When will you young electricians get it through your head, MCB's are sized to protect the cable, not the dammed loads!!!

Why would you possibly want to de-rate a perfectly sound FRC, what are you going to hope to achieve, by putting a 20A MCB on a FRC then??

 

[i=p/u]

no1 said that, but theres nothing to stop you putting in a20A radial..... if the kitchen was small and no loads tied in i.e flat or something.. come on man the rings are going going going gone

 

[Jimmyb]

When will you young electricians get it through your head, MCB's are sized to protect the cable, not the dammed loads!!!

Why would you possibly want to de-rate a perfectly sound FRC, what are you going to hope to achieve, by putting a 20A MCB on a FRC then??

I know the mcb is to protect the cable but isnt the cable selected based on the load.

I wouldnt derate a (FRC do you mean RFC and besides who mentioned them n e way) i would of maybe used 2.5mm instead of the 4mm

 

[i=p/u]

engineer you only sing when your winning, only sing when your winning

 

[i=p/u]

hes toxicated with china chicks and china beer the night...

 

[High Tower]

I'm with E54!!

The rating of your protective device MUST be more than your Design current (>IB) and at the same time less than your current carrying capacity of your cable taking into account the appropriate reference method.

The only time I derate the protective device for a general power circuit is a) if it's a radial on 2.5 cable
B) if the ring cpc is broken and cannot be repaired ( I have had a couple of occasions where the cpc's have been cut out) so I have left the ring intact and de rated the mcb to allow for the slightly higher Zs value.

 

[i=p/u]

dont think the oringinal poster wanted to add a smaller cable to the protective device... he is saying he used to just installing rings in kitchens...at 32A

wires crossed, short circuit

 

[i=p/u]

if cpcs are cut, how does that allow a fault path back if you wouldnt mind explaining , i know i missing something simple..

I'm with E54!!

The rating of your protective device MUST be more than your Design current (>IB) and at the same time less than your current carrying capacity of your cable taking into account the appropriate reference method.

The only time I derate the protective device for a general power circuit is a) if it's a radial on 2.5 cable
B) if the ring cpc is broken and cannot be repaired ( I have had a couple of occasions where the cpc's have been cut out) so I have left the ring intact and de rated the mcb to allow for the slightly higher Zs value.

 

[High Tower]

The last time I faced this, some moronic diy'er had cut the cpc's out ( I assume they cut em too short so just chopped em out)

So I had end to end continuity on L-L and N-N and broken on cpc. So removed socket from the point that the cpc's had been chopped, re instated l&n with wagos and fitted a blanking plate.

De rate breaker to 16a so all sockets have a fault path back on either leg al be it with a higher Zs

 

[jase]

why not just break the ring and turn it into 2 radials?, if you have a ring on l + n but 2 radials on cpc, where are you getting your R1+R2 from?

 

[i=p/u]

ahhh right, get ya, the conection of line and neutral and face plate says it all, so 2x Zs tests on this ring final cheers

 

[Knobhead]

OK I’ll echo E54, the MCB is to protect the circuit.

NOT the load, the plug top or FSU fuse take that responsibility.

 

[i=p/u]

yes tony you are correct but the the original poster didnt say derate cable and everyone knows Ib <In <It

 

[High Tower]

why not just break the ring and turn it into 2 radials?, if you have a ring on l + n but 2 radials on cpc, where are you getting your R1+R2 from?

Because I knew where the break was, I knew it wasn't a hazard as it wasn't current carrying and it was safer and easier to leave it intact

R1&R2 measured and recorded as per radial, offending socket removed and blanked so all remaining had continuity