Workshop Electrics

[paulm]

Hi Leptus, sorry, saw your post and then promptly forgot all about it

Not much to photo really to be honest, not sure what would help particularly, but happy to answer any questions if I can.

A request for the forum generally from me for some advice though. Had a mega resawing session yesterday and today, converting more of Paul C's walnut logs (there is a bright side to the damp weather, means I get excused gardening duties and can get some workshop time in :lol: ).

Late today though the bandsaw blade started stalling, and on investigation the drive belt was disintegrating, the new motor being too powerful for the narrow section belt I guess. So took a trip to Halfords and got a meatier fan belt, after trying about fifty odd to get one roughly the same size :shock: , fitted it and went like a dream.

Straight after though, it started to blow the 13amp fuses, and have now gone through four of them :shock: . On occasion it would start and run okay, but mostly just popped the fuse on start up.

Not sure why this should be ? The wheels and blade move freely, nothing else has changed, the mcb doesn't trip. Thinking I may have to run a dedicated 16amp circuit after all........

Any thoughts or advice welcomed

Cheers, Paul

 

[p111dom]

I'm probably going to get in trouble for this but it depends how dodgy you want to go. If you don't want the mess with the expense of running new cabling and avoiding the part P issue altogether you could always splice in two 13amp plugs into the one cable. Yes its a bodge, yes it would make you think "what the hell" when you saw it but apparently the practice was quite common some years ago as a cost cutting/saving measure. When buying a machine a few years ago the guy has three machines wired up this way to double plug sockets and had ran them trouble free for 10 years. I spoke to a sparky about it and he said it wasn't advisable but it would work and he'd seen it before.

 

[Night Train]

I wouldn't recommend the double plug method as the fuse needs to be able to protect the cable to prevent over currnet from melting the cable and causing a fire. Two plugs would give you 26 amps to play with! Also the socket, even double sockets, are only rated at 13 amps total so you couldn't plug both into a double socket without risk of over loading the socket wiring connections.

If the motor worked before and doesn't now then something has changed. You changed the belt. Maybe the old belt was slipping a bit and reducing the start up load whereas the new meatier belt is transmitting all the load to the motor and increasing its start up current.

As an electrician I have a dedicated consumer unit for my workshop with a 100mA RCD and also an extension lead with a 10mA RCD on the end of my bench for hand power tools.

 

[paulm]

Maybe the old belt was slipping a bit and reducing the start up load whereas the new meatier belt is transmitting all the load to the motor and increasing its start up current.

That's pretty much where I had got to in my thinking as well. Not too much trouble to pop down to Screwfix and get some 16 amp stuff I guess, might as well do it properly.......

Cheers, Paul

 

[p111dom]

I wouldn't recommend the double plug method as the fuse needs to be able to protect the cable to prevent over currnet from melting the cable and causing a fire. Two plugs would give you 26 amps to play with! Also the socket, even double sockets, are only rated at 13 amps total so you couldn't plug both into a double socket without risk of over loading the socket wiring connections.
.

That's correct to a certain extent but you can always put a 13amp fuse in one and a 3amp fuse in the other giving you 16amp load not 26. If the machine is drawing nearly 13amps anyway when in full working order then the cable should be relatively beefy. An extra 3amps wouldn't make that much difference especially when you consider it will only be drawing over or near to 13amps on start up. Neither would the extra load on the socket. Most sockets are wired up to a 32amp ring main anyway so you would have thought that the socket terminals should be tested up to that. I rewired my twin motor extractor so each motor has a separate plugs so I can regulate the amount of suck remotely. Three years on despite the load being pretty high and with two 13amp plugs into one double socket I have had no problems. Its not something I'd advocate as a permanent solution but if I were say in the middle of a job and didn't have the time or money to wire in a dedicated 16amp supply, I'd do it in the interim. Its not like you would leave it unatended running.

 

[Jake]

That's correct to a certain extent but you can always put a 13amp fuse in one and a 3amp fuse in the other giving you 16amp load not 26.

On the basis of that statement alone, I don't think you should be advising anyone on electrics!

 

[p111dom]

I take it that thats not correct then. Yes your right its probably a silly thing to do. I actually haven't done this myself. I've just seen someone else that has done something similar and seemed to have no problem with it for several years.I didn't ask if both plugs were fused at 13amps each. Personally I have a dedicated 16amp supply to the two machines which require it. This option was pointed out as a possibility when I was faced with a similar situation on a sanding machine which was drawing 12.8 amps on start up and blowing the fuse on every third start up. Would the load not be spread between the two plugs? I take it from the reply that wouldn't be the case. That said I would have thought the worst that would happen is the fuse would blow in anycase.

 

[Night Train]

What you are suggesting may sound right in a bodge kinda way but electrics can be very unforgiving to the bodger. Quite aside from the shock risk any risk of sparks or excessive heating of electrical terminals in a woodshop full of nice dry timber, wood shavings and saw dust is quite a fire risk.

It is worth noting that the reason a fuse blows is because it melts the wire that is inside it. Each time it melts the terminals have become heated and with each heating the expansion and contraction of the metals in the connections will cause the connection to loosen. Lose connections cause more heating and increase resistance to current flow. This reduces the voltage slightly and increases the current causing more heating.

As an emergency bodge a nail could be used to replace the fuse but is getting the job done that moment worth the risk?

I knew a welder who had added a cooling fan to the back of his portable arc set. The fan prevented the welder from over heating when used at maximum capacity but the extra current draw of the fan caused the fuse to blow.
His solution was to drill out the 13 amp fuse and solder in a 16amp fuse wire. Problem solved until he used an extension lead and the fuse there blew. He did the same to his extension lead fuse and used it like this for many months until one day the extension lead caught fire while he was welding.

I have a fitted a fan on my welder too. I just don't wind it up to maximum and have never blown the 13 amp fuse in 25+ years of welding with it.

 

[p111dom]

That's worth heading I guess. I don't have the best form on welding either to be honest. The last times I was welding a sill on the car, lying on my back when finished I was congratulation myself of a job well done and it wasn't till I stood up that I saw I'd set fire to the interior carpet. :lol: Even after a few beers last night I don't know now why I though that would work. I think the load would be drawn equally from both sockets so if the machine was pulling 13 amps total, the draw would be 6.5amps per plug. The plug with the 13 amp fuse would be fine having a 6.5amp load but the other one would blow with the 3 amp fuse. Two five amp fuses obvosouly gives you less that the 13amps of the one plug and with no domestic fuses rated between the 5 and 13 I guess you're stuck with two 13amp fuses which like you said before would require a surge or draw of 26 amps plus to blow the fuses. This would potentially overload the cable so its a bum idea. The problem with this forum unlike others is that people are on it so frequently that if you make a stupid post, by the time you go back on the edit it, several people have already replied. Note to self, beer and thinking don't mix.

 

[paulm]

Oh no, just realised that being Easter Sunday Screwfix (and the rest of the world) is shut all day

STill, preparing a list of bits and pieces to hopefully pick up tomorrow I came across this

http://www.screwfix.com/prods/27903/Ele ... Curve-RCBO

Seems to deal with the only slot in my cu being on the unprotected side of the box, but not sure if it is worth paying that much for it compared to a normal 16a mcb :-k

Also a bit confused about the types of 16a plugs and sockets. There seems to be several which sound the same and look the same, but have very different prices so I am obviously missing something. I guess it may be worth going for IP44 rating (dust ingress ?) but then again none of my 13 amp supplies/plugs have that so maybe not really an issue after all and I should just go for the cheapest ?

Here's some of the alternatives, any help appreciated !

https://www.screwfix.com/prods/49232/El ... -2P-E-IP44

https://www.screwfix.com/prods/44755/El ... -2P-E-IP44

https://www.screwfix.com/prods/94163/El ... t-16A-240V

Cheers, Paul

 

[p111dom]

Again I'll probably get shot down here but I was told at the time by the sparky that the 16amp plugs technically can't be used in a domestic enviroment as the don't comply to something to do with the gaurding of the pins/terminals. I know several people that have them in their garage though but he advised against it. In the end I hard wired mine into a industrial type isolator switch so wiring to the none protected side of the consumer unit was fine. I was going to add an isolator anyway so I saved on the cost of the plug and socket. Fortunatley I have enough room so the machines don't need to be moved around the shop but if they ever did it only takes 5 minutes to click the MCB and unwire them from their respective isolator switches.

 

[Deejay]

Hello Paul

I'm no longer regarded as competent in electrical wiring since Mr Pescott's Part P tax was introduced, but I would think you want something like this

https://www.screwfix.com/prods/40962/El ... 2P-E-IP44#

screwed to the wall.

If you fit an RCBO in a slot for a circuit on the unprotected (Non RCD) side of the CU, it will give you both RCD and overload protection on that circuit. Fitting an MCB on the unprotected side will only give overload protection to the circuit it feeds.

I'd take Jake's earlier advice 'Actually, simpler still would be to fit a single unit 16A RCBO if you can find one which fits your CU.'

As far as ingress protection goes, all the screwfix stuff seems to be IP44 which keeps out solid objects greater than 1mm diameter, and splashes of fluid. If you want dust protection go for IP5x and dust tight is IP6x. I'd be happy with IP4.

One thing you might also check is the rating of the flex connected to the motor, since you've doubled the current it carries.

Cheers

Dave

 

[Night Train]

Why not just hard wire it into a 20 amp double pole switch fed from a 16 amp mcb/rcbo instead of using a 16Amp socket? It is hardly a portable tool.

 

[paulm]

Think I'll go for an rcd type single mcb, angled mounted socket and connector, assuming our newly opened Screwfix trade counter has all that in stock tomorrow morning. As it's my first order there and I have a special text message I think I still get an initial 10% discount

Don't think it's particularly easier or cheaper or advantageous to hard wire rather than plug as a switch is much the same price as a plug and socket I think ?

Thanks for all the suggestions.

Cheers, Paul

 

[paulm]

Popped into Screwfix this morning and picked up all the bits, except I got a normal mcb after all rather than an rcd variant as I couldn't really see the point in the rcd one for this application.

Took a couple of hours all in to get the stuff and wire it all up, fasten the cable and fit plug and socket, really pleased.

But then tested it and now the mcb just trips straight away :evil:

Fitted a fly lead to the new socket and used a three pin socket tester on it which shows I've cabled it all up okay, tried a couple of other appliances on it and they are fine too.

So I'm guessing I need to swap the B type mcb for a C type, or actually the problem is with the bandsaw, but can't find a C type mcb (16a) on the Screwfix site although they do 6, 10 and 32 amp !!!

Will have to wait till tomorrow and find a proper electrical factors to get the mcb, and just hoping that does the trick and it isn't the bandsaw switch or motor.......

Cheers, Paul

 

[RogerS]

What current rating MCB did you buy, Paul?

 

[Night Train]

This bit of information on MCB ratings and types may help you decide what you need and what is happening.

 

[paulm]

Thanks for the info NT.

Roger, it was a 16a B type, nothing special, so I'm hoping it just needs a C type instead. The general circuit 16a mcb it was wired too before didn't trip but I gues that was just because the 13a fuses were going first, and now it's on a dedicated 16a circuit with commando plug/socket and no 13a fuses the trip is now going instead.

Pretty sure I wired it in correctly, as per my previous post the new circuit will run other stuff no problem if I use a fly lead temporarily........

Cheers, Paul

 

[paulm]

Decided to double check all my connections again, in case I had wired the plug differently to the socket or something silly, it has been done before :roll: , but not this time, nothing obvious wrong........

Cheers, Paul

 

[misterfish]

http://www.screwfix.com/search.do;jsess ... ton=submit is what I have for my table saw - it works fine while a type B nearly always trips.

Misterfish