Can a 16 amp fuse on the consumer board be changed to a 40 amp fuse?

[Peter70]

I have had power installed to my shed some years ago and have only now noticed that the fuse fitted by the electrician on the main board only gives me 16 amps and I have just purchased a Plasma Cutter that requires 40 amps, 32 amps minimum and was hoping I could change the 16 amp fuse for a 40 amp on my main board without any problems.

 

[Fleeting]

It would depend on the type, size and installation method of the cable along with volt drop and ADS requirements. 

 

[ProDave]

That depends entirely on the size and length of the cable between the house consumer unit and the shed.

The fact it only has a 16A mcb at present hints at it being a small cable so the answer is probably no you can't.

 

[SPECIAL LOCATION]

I have had power installed to my shed some years ago and have only now noticed that the fuse fitted by the electrician on the main board only gives me 16 amps and I have just purchased a Plasma Cutter that requires 40 amps, 32 amps minimum and was hoping I could change the 16 amp fuse for a 40 amp on my main board without any problems.

The purpose of the fuse, (yours is probably a miniature circuit breaker MCB), is not to allow power to supply whatever equipment you want to connect to the circuit..

Rather it is there to ensure the cables supplying your equipment are NOT damaged by the power that your appliances need..

The basic concept is something along these lines..

Electricity ALWAYS generates heat as it flows around a circuit..

More current = More heat..

Cables carrying more current will need bigger conductors compared to cables carrying less current..

Bigger cables cost more money..

Most jobs are designed for the most cost effective balance of power required -vs- cost of the cables needed..

As a general rule it is unlikely that most circuits could have their current carrying capacity more than doubled without some new wiring installed..

The weakest link MUST be the protective device NOT the cable..

Otherwise you will just end up melting your cable!!

There are other problems such as Volt Drop, & earth loop impedance which also need to be considered..

So without knowing exactly what size cable is currently installed and how far away the shed is..

it is impossible to say 100%.

But on the balance of probability it is very unlikely you can safely just uprate your 16A MCB with a 40A MCB.

:coffee      

 

[Andy™]

well you could... but then you may find the cable is your new 'fuse' when it melts and or burns the place down.

 

[Sharpend]

If you do I wouldn’t worry too much about the heat of the plasma cutter you might find that the cable goes through your arse like a cheese cutter. 

 

[Peter70]

Thank you for all your very helpful reply's. I should of explained my self better in that the supply cable to my shed is an armoured cable twice the thickness of the mains cable  coming into my house and the shed is about 18 mitres away from my home so will the same rules apply to the answers you have given me or is this a game changer?   

 

[SPECIAL LOCATION]

Thank you for all your very helpful reply's. I should of explained my self better in that the supply cable to my shed is an armoured cable twice the thickness of the mains cable  coming into my house and the shed is about 18 mitres away from my home so will the same rules apply to the answers you have given me or is this a game changer?   

No change to anything that has been said so far, as we still haven't been told the CSA of the cable conductors..??

 

[Sharpend]

Have a look on the outer sheath of the swa for any cable markings, amongst them you may find a mm2 reference and No of cores. 
that would help.  

 

[Peter70]

Thank you Sharpend for the information, I have checked the Armoured Cable and there is no writing on it probably dew to being out in all weathers after so many years but the size of this SWA is 16mm 3 cored and the cable that runs from that to the consumer board is a 6mm 3 cored wire, it is the same size as my cooker wire.

I don't know if this information helps in my quest to change a 16amp pcb to a 60amp pcb but I would appreciate any info you can give.

 

[Fleeting]

I think you need to get an electrician. Seeking correct advice with random information on an internet forum isn't the best way forward.

 

[Bruspark]

When you "had power installed to my shed some years ago"   did you get a certificate with test results etc. recorded on it ? 

If so that may clarify the cable ratings and reasoning and whether your 'fuse' is actually a fuse (in which case a check-over the entire installation is definitely due..)
-- It may also suggest a good electrician to ask for advice on your question

If there wasn't a certificate/record ; there's a lot of preliminary fact gathering and testing to do to even begin to safely answer your question N years on . .