Connecting 16amp p/t to supply

[stockonehundred]

Hi All,

I just got my hands on an old, single phase Cooksley p/t, which has a 16amp plug. My workshop runs off a separate switch off the board in my house and my understanding is I'll need a new board in my workshop (to save walking back and fourth if it trips) with a 32amp switch and an RCD. Then wire in a socket that'll take the blue, 16amp plug. Obviously I'll need an electrician to check everything is correct before they make the final connection to the mains supply.

I have two questions. If I went down the above route, is this just about right? Also, I cam across this...... http://www.thesafetysupplycompany.co.uk ... -fl13.html

Does the above link mean I can by-pass all that time, money and effort and literally just plug in this instead? Or will it be a trip nightmare. I thought these adaptors were only suitable for PAT testers, but there is no mention of that on this website.

Thanks in advance.

 

[deema]

The issue with starting beefy motors is that when they are stationary they appear to the electricity just like a short circuit. It's only when they start rotating do they generate something called inductance which is a form of resistance to the current flowing through it. When you first switch on a motor you generate what is called an in rush current, which is extremely high. It only lasts for a short period of time, until the motors starts to really turn. If a motor doesn't start to turn because it's jammed, the high current continues and the motor heats up, and will quickly catch fire. Hence when a motor stalls you need to cut the supply extremely quickly.

The current rating of fuses are all about protecting the wiring from over heating due to the current that it's carrying. So, with 16A you need to ensure that all connections and wiring is able to withstand 16A as a minimum. Normal 2.5mm 13A cable is not rated for this application. However, and I DO NOT recommend this, all of my machines are run off standard 2.5mm 13A cable as the only really high currents are at start up.

To make the circuit work properly you will need to swap the RCD in your house that should be dedicated to supplying the workshop with one that is Class C ( normal domestic RCD's are class B). This allows a longer period of higher current to flow through it before it trips. Within the workshop you should have a distribution board with each machine that has over a 13A socket individually wired back to its own RCD. The RCD's for the 16A machines should also be Class C.

Only use RCD's which match or are lower than the rating of all the cable / switches in the circuit. I.e. DO NOT upgrade the RCD to 32A unless everything in the circuit is rated to al least 32A.

In practice, all that will be required is to replace two RCD's and run some higher rated cable from the distribution board in your workshop to a 16A socket....preferably with an isolation switch before the 16A socket. An isolation switch is very cheap, and they are really easy to use compared to pulling out the plug....which means you will isolate the machine before placing pinkies inside for blade changing etc.

It must be signed off by a qualified electrician according to regulations.

 

[Andy RV]

I'm no expert but as far as I'm aware you should be using a 16 amp MCB to feed the 16 amp socket. You can then add more MCB's to the new consumer unit to feed the sockets ect. You will also have to ensure that the wiring running to the workshop is up to the job.

You could try the adapter however chances are the 13 amp fuse will blow at start up.

What size motor(s) does the P/T have? I've found that 1.5kw / 2hp is the limit on a 13 amp plug and if it's a high starting load application then it will likely blow the fuse.

 

[RogerP]

My SIP P/T is 2000w (2.75 HP) and runs okay off 13a socket.

 

[RogerM]

Hi All,

I just got my hands on an old, single phase Cooksley p/t, which has a 16amp plug. My workshop runs off a separate switch off the board in my house and my understanding is I'll need a new board in my workshop (to save walking back and fourth if it trips) with a 32amp switch and an RCD. Then wire in a socket that'll take the blue, 16amp plug. Obviously I'll need an electrician to check everything is correct before they make the final connection to the mains supply.

I have two questions. If I went down the above route, is this just about right? Also, I cam across this...... http://www.thesafetysupplycompany.co.uk ... -fl13.html

Does the above link mean I can by-pass all that time, money and effort and literally just plug in this instead? Or will it be a trip nightmare. I thought these adaptors were only suitable for PAT testers, but there is no mention of that on this website.

Thanks in advance.

FWIW, I run my Startrite 352E which has a 16 amp plug off one of the fly leads you mentioned without any trouble. This is simply plugged in to a 13 amp socket. In my case, I'm working in a garage which has its own 13 amp ring main run in 2.5 mm cable which is connected to the consumer unit through an old style 20 amp fuse. I also run a twin motor camvac off the same circuit (different socket) and have never once blown the fuse.

 

[stockonehundred]

Thanks all. My p/t is a twin motor 3hp and 2hp, but they don't start up at the same time. I don't know that much about these old machines, but the motor winds up slowly once started so perhaps there is much less of a surge when you start it. My workshop is also connected with 2.5mm cable directly into a wall socket and then a fuse box directly next to that, which feeds the lighting cable. I might give the adaptor a go at only £5, but if anyone thinks this is a bad idea based on the size of the motors in the p/t then holler....

 

[wallace]

Its not so much the motors starting up slowly but the motors trying to spin the mass of the cutter head. This draws a lot of current. On my 18" p/t the head weighs about 6 stone

 

[RogerM]

Thanks all. My p/t is a twin motor 3hp and 2hp, but they don't start up at the same time. I don't know that much about these old machines, but the motor winds up slowly once started so perhaps there is much less of a surge when you start it. My workshop is also connected with 2.5mm cable directly into a wall socket and then a fuse box directly next to that, which feeds the lighting cable. I might give the adaptor a go at only £5, but if anyone thinks this is a bad idea based on the size of the motors in the p/t then holler....

I don't think you have anything to lose by giving it a try. The worst that can happen is that you blow the 13 amp fuse in the fly lead. Worth a punt at a fiver I would have thought.

 

[stockonehundred]

Yes it is. I'll report back. Thanks again...

 

[Lons]

I use one of these for my SIP saw. It's wired up via a 16 amp breaker.
http://www.ebay.co.uk/itm/262093302947? ... EBIDX%3AIT

 

[n0legs]

2.5mm flex (most variations) CCC of 25 amps
2.5mm T&E CCC of 24 amps

 

[Myfordman]

The issue with starting beefy motors is that when they are stationary they appear to the electricity just like a short circuit. It's only when they start rotating do they generate something called inductance which is a form of resistance to the current flowing through it. When you first switch on a motor you generate what is called an in rush current, which is extremely high. It only lasts for a short period of time, until the motors starts to really turn. If a motor doesn't start to turn because it's jammed, the high current continues and the motor heats up, and will quickly catch fire. Hence when a motor stalls you need to cut the supply extremely quickly.

The current rating of fuses are all about protecting the wiring from over heating due to the current that it's carrying. So, with 16A you need to ensure that all connections and wiring is able to withstand 16A as a minimum. Normal 2.5mm 13A cable is not rated for this application. However, and I DO NOT recommend this, all of my machines are run off standard 2.5mm 13A cable as the only really high currents are at start up.

To make the circuit work properly you will need to swap the RCD in your house that should be dedicated to supplying the workshop with one that is Class C ( normal domestic RCD's are class B). This allows a longer period of higher current to flow through it before it trips. Within the workshop you should have a distribution board with each machine that has over a 13A socket individually wired back to its own RCD. The RCD's for the 16A machines should also be Class C.

Only use RCD's which match or are lower than the rating of all the cable / switches in the circuit. I.e. DO NOT upgrade the RCD to 32A unless everything in the circuit is rated to al least 32A.

In practice, all that will be required is to replace two RCD's and run some higher rated cable from the distribution board in your workshop to a 16A socket....preferably with an isolation switch before the 16A socket. An isolation switch is very cheap, and they are really easy to use compared to pulling out the plug....which means you will isolate the machine before placing pinkies inside for blade changing etc.

It must be signed off by a qualified electrician according to regulations.

I think you mean MCB in every case of where you refer to RCD above!

 

[mindthatwhatouch]

Stockonehundred.
It's difficult to provide advice without seeing the set up, are you saying that there is 2.5mm cable (fixed wiring connected into the back of a socket that feeds the workshop) or it is on a plugtop with a bit of flex?
Either way you should not feed 16A off of this.

How easy is it to get an armoured cable from house consumer unit to the workshop? 32amp MCB then RCD in consumer unit in workshop. 6 amp MCB for lights, 16A mcb for 16A S/O, and separate MCB for sockets.
As suggested above type C MCB for the P/T. You could use RCBO's but not sure how available they are type C rated.

Hope that helps.