Consumer box - replace 16amp with 32amp

[Johnnylynch]

Hi, I bought a new table saw for garage but it requires a 32 amp circuit, (trips the current 16amp). Can I simply replace the 16 with 32? Load on consumer says 80amp and current in 2x32amp sockets, 1x32amp cooker, 2 x6amp lights and 1x16amp for garage. Obviously that's more then 80amp but guessing that's total used load?

Thanks in advance.

Johnny

 

[EFLImpudence]

It depends on the cable used but unlikely to be suitable.

Are you able to tell the size of it? If it is single solid core in each wire then not suitable.

 

[ericmark]

Not as easy as that. The MCB has two parts the thermal and magnetic with B type magnetic is 5 times value of thermal. The limit for thermal part of trip is current rating of the cable. Limit for magnetic is the loop impedance.

So you need to know the earth - line loop impedance, the neutral - line loop impedance, size of the cable, It it has RCD protection, and method of earthing before one can start working out the limits.

 

[Johnnylynch]

okay thanks both, guess ill just need to run an extension cable into the house when using saw. cheers.

 

[Ian2008]

Nope that won't work. If the saw trips a 16A mcb then the 13a fuse in the plug on your extension lead will blow.

 

[ban-all-sheds]

Why will it?

 

[securespark]

Popcorn time.....

 

[sparkwright]

This should be good...

 

[plugwash]

Nope that won't work. If the saw trips a 16A mcb then the 13a fuse in the plug on your extension lead will blow.

As BAS hints that is not true. A fuse is a purely thermal device, blow time varies in a fairly smooth manner with the magnitude of the overload.

A MCB on the other hand is a combination thermal-magnetic device. The thermal part has a smooth characteristic but the magnetic part is more of a theshold detector. Even a very short excursion over the magnetic part's trip point will take out the breaker.

The first thing that needs to be done is an assesment of the wiring to and in the garage, what type is it? what size is it? how is it installed? how long is it? what does it supply? are there any protective devices at the garage end? These will help asses whether a breaker with a higher current rating is an option.

Another option could be a 16A type C breaker. This has the same thermal trip as the 16A type B but a higher setpoint on the magnetic trip. Loop impedances would still need to be calculated and/or measured to check it was safe though.

 

[kai]

Take it back to to the seller. it is obviously unsuitable for an ordinary 60/80amp single domestic supply. It is clearly an industrial pattern saw, and will cause severe interference with your neighbours supplies, as the current surge on startup will cause light to dim sharply, and possible your neighbours RCD to trip out.

 

[ericmark]

There is a huge difference between a greater than 16 amp inrush and greater than 16 amp load. There are many ways to get a motor to turn. With single phase often there is a large inrush, even a fridge freezer can take 10A start load, but run is more like 0.5A. The way around it today is three phase motors with inverters which can be set to give a nice slow start.

Compressors are a big problem, but other items often don't need to start quickly and can be designed to work with a smaller supply. One method is to allow the motor to start no load, having a over centre crank to tension belts once running works well. Also starting another motor first. With sheep shearing I had to start the sharpening stone before the shears and it then worked fine.

There is no one size fits all. And I don't think this is really DIY stuff. With a lath for example selecting slow speed to start may be enough. So first step what does the motor plate say? Once we know size of motor we will have more idea of how to cure.

 

[ban-all-sheds]

Take it back to to the seller. it is obviously unsuitable for an ordinary 60/80amp single domestic supply.

That may be so.

But there's no guarantee that it could be returned. It may be that the seller made that clear and Johnny took no notice, or he made all the information about it available and Johnny did not have the expertise needed to recognise what sort of supply it needed.

 

[Johnnylynch]

Hi, i does work fine when used on extension cable to internal 32amp socket circuit. seem like its just the initial startup that is tripping the 16amp fuse. if it was causing a dim to lights id see it in the garage and it certainly does not seem to be.

 

[Johnnylynch]

this is the saw - http://pingtek.36.ekmpowershop.net/pt48250s-table-saw-21-p.asp

 

[ban-all-sheds]

What do the instructions say about the electrical supply requirements?