Workshop Electrics

[paulm]

Thought I would post a query in this section for anybody with some electrical knowledge.

Planning to upgrade the motor on my bandsaw from 1100w to 2200w which means I'm advised that the new motor won't run on a 13amp plug as the running current requirement is 13.2 amps.

So I think this means I need a 16 amp connection.

I'm assuming the best way to do this is run a dedicated 16amp circuit from the workshop consumer unit, and not just to introduce a 16 amp socket on the existing circuit (which does actually have a 16 amp breaker by coincidence) ?

If a new circuit is called for I have one spare slot in the consumer unit, but it's to the right of the unit and the rcd breaker and therefore not covered with the rcd (it's in the unprotected part with the lighting circuits).

Assuming I take all necessary precautions ( I have done a fair amount of basic electrical work in the past), is it straightforward to reposition the rcd breaker one bay to the right and therefore reposition the vacant bay to the left of the rcd and to be protected by the rcd with the other socket circuits, or would I have to do anything additional other than wiring in the new circuit to the rcd and vacant slot and putting in the additional 16 amp breaker ?

Many thanks for any advice.

Cheers, Paul

 

[StevieB]

OK, firstly you will need to run a radial 16A feed for the bandsaw from a dedicated breaker in the CU. Don't put it on an existing circuit - despite the 16A breaker your circuit is on, running anything else on the circuit at the same time as the bandsaw may trip the breaker anyway.

As to moving the rcd - depends entirely on your CU and how it was made. The busbar (positive rail with teeth the MCBs sit on) will be split to keep the two sides of the CU seperate. Thus if your box is full you will need a new busbar cut appropriately to maintain this split between the two sides. Some split CUs have a fixed trip switch and cannot be moved - without looking at the CU its not possible to tell, but look at the negative feed to the trip - is it a solid bar or is it a cable? A solid bar will not move, a cable might (I stress might, not will here).

Finally, the only possible consequence of running it from the non-rcd side and tripping the MCB is that the entire box goes dead from the mains tripping. This means no lights, but apart from that not a major problem. The bandsaw is one of the safer power tools in the shop and you will need to decide how likely it is that your circuit trips and how likely it will be you can see nothing if the lights go out. If you are worried by this, or touching the blade before its stationary in the dark then don't wire into the non-rcd side.

If you cannot get the circuit onto the rcd side you have two options - run a secondary box from the rcd side replacing an existing mcb into the new box, or replace the entire CU with a larger one. Neither are straightforward solutions and depending on your setup may require dropping the meter tails from the mains (illegal, and means breaking the electric comapnies lead seals) as well as the usual part P caveats that people are bound to mention further down the thread.

You dont say whether you are talking about the house main CU or a smaller one in the workshop - could you possibly run a single lighting feed from the house CU to the workshop, bypassing the shop CU and thus leaving a light on if the workshop CU fails? I am assuming here that your workshop CU is wired into the house one - if you are running from the house main CU this is not an option.

Steve.

 

[andrewm]

Finally, the only possible consequence of running it from the non-rcd side and tripping the MCB is that the entire box goes dead from the mains tripping. This means no lights, but apart from that not a major problem. The bandsaw is one of the safer power tools in the shop and you will need to decide how likely it is that your circuit trips and how likely it will be you can see nothing if the lights go out. If you are worried by this, or touching the blade before its stationary in the dark then don't wire into the non-rcd side.

How about wiring from the non-RCD side to a seperate 16A RCD by the bandsaw socket. That way you have RCD protection for the bandsaw without too much messing around with the consumer unit, it is easier to reset should it trip and it won't plung the whole workshop into darkness.

Andrew

 

[StevieB]

How about wiring from the non-RCD side to a seperate 16A RCD by the bandsaw socket. That way you have RCD protection for the bandsaw without too much messing around with the consumer unit, it is easier to reset should it trip and it won't plung the whole workshop into darkness.

Aye, as I said you can run a secondary CU from the first. A two way garage CU will be fine, but I would still want it on the rcd side of the main CU to prevent the possibility of the lights going down. You might well find it difficult to get a secondary CU that has a main trip of a lower rating than the main trip on the main CU, thus making sure you secondary goes before the main (is that a Donald Rumsfeld type statement!). I would have to go hunting through the TLC website as I don't know off the top of my head. Secondary CUs still require meter tails via a Henley block, making it difficult to position then where you want them ie next to machines as emergency cutouts. A cutout switch is better for this purpose.

Steve.

 

[PowerTool]

2,200W / 230V = 9.56A,so will theoretically run fine on a 13A supply.
I take it the start-up current will trip a 13A breaker,and can't be solved by using a "B" curve MCB ? (Although it will obviously be better on a seperate supply,or it doesn't leave you much spare to run a dust extractor..)

Andrew

 

[Jake]

A two way garage CU will be fine, but I would still want it on the rcd side of the main CU to prevent the possibility of the lights going down. You might well find it difficult to get a secondary CU that has a main trip of a lower rating than the main trip on the main CU, thus making sure you secondary goes before the main (is that a Donald Rumsfeld type statement!). I would have to go hunting through the TLC website as I don't know off the top of my head. Secondary CUs still require meter tails via a Henley block, making it difficult to position then where you want them ie next to machines as emergency cutouts. A cutout switch is better for this purpose.

Main trip? What main trip - we are talking about the non-RCD side of the CU, so there is no main trip (unless there is a whole house RCD, but that has not been mentioned), just the 100A isolation switch which is going nowhere until it melts.

There isn't an issue with discrimination to worry about if Chisel sticks a 16A breaker on the non-RCD side (or rather, no more issue than there is with the workshop CU as a whole).

No need to touch the meter tails in this scenario - you just feed a socket from a new 16A MCB - and to get RCD protection you either use an RCD protected "commando" socket (at an ouch price!) or feed a 2-way 'consumer unit' box stuffed with an rcd, and then out to the naked commando socket.

 

[Jake]

Actually, simpler still would be to fit a single unit 16A RCBO if you can find one which fits your CU.

 

[andrewm]

Aye, as I said you can run a secondary CU from the first. A two way garage CU will be fine, but I would still want it on the rcd side of the main CU to prevent the possibility of the lights going down. You might well find it difficult to get a secondary CU that has a main trip of a lower rating than the main trip on the main CU, thus making sure you secondary goes before the main.

What about something like this?

http://www.tlc-direct.co.uk/Main_Index/ ... index.html

If it is on the non-RCD side of the main CU then an earth fault will just trip the local RCD. Only an over-current will trip the main CU. I haven't looked to see whether these are available in any lower currents but this is intended for an electic shower so must be fairly common.

Andrew

 

[Anonymous]

2200W does not draw 13A!!!!!

It will be around 9A

You will be fine running it from a 13A socket

 

[Sawdust]

2200W is about 3 HP. My workshop has three machines with 3HP motors - all running fine from 13A sockets so I would be tempted to try your motor before going to a load ef expense re-wiring.

You might be unlucky and find the start-up current trips your supply but I would definitely try it out first.

Cheers
Mike

 

[paulm]

Thanks guys, lots of options it seems.

Think I'll try the new motor (haven't ordered it yet) on the normal 13a plug first, like Tony says it should in theory only draw 9a (2200w/240v), only the motor supplier said the running current (not startup current) was 13.2a because motors are never 100% efficient so the theoretical 9a was in real life 13.2a, but I have other 2200w (and more) equipment that runs on 13a plugs with no problem, so think I'll try it and see.

If it is an issue in practice then looks like a 16a solution of some sort can be sorted without too much trouble or cost.......

Many thanks, Paul

 

[RogerS]

....

If it is an issue in practice then looks like a 16a solution of some sort can be sorted without too much trouble or cost.......

But no-one has mentioned the dreaded Part P. The proposed work falls squarely under it IIRC.

 

[bob321]

i can run a 2100w TS and a 1200w dust extractor and about 50w of lighting

bob321 8)

 

[misterfish]

I take it the start-up current will trip a 13A breaker,and can't be solved by using a "B" curve MCB ?

It is a simple job to replace a 'B' type MCB with a 'C' type which is designed to cope with the transient initial surge of the motor.

My table saw is on a dedicated 16 amp MCB circuit - with a type 'B' in place it regularly tripped on start up. With the type 'C' there is no problem.

Misterfish

 

[paulm]

Bit of an update on this.

After a lot of emailing to and fro and discussions with suppliers have finally ordered a 2.2kw motor as a replacement and should be here hopefully in time for the weekend.

If everything goes according to plan (!) then the flange mounting I've ordered with it should make it a straight bolt on replacement, but we'll see [-o<

Unfortunately, but quite sensibly I guess, the bigger motors come with a bigger shaft diameter which means I've had to order a replacement pulley for the shaft as the existing one on the bandsaw was a smaller hole diameter and I don't have the means to bore it out accurately. I also want to keep all the original stuff in case the whole plan falls apart and I need to retreat back to what I have currently !

If I can get as far as getting it all mounted and set up then will try running it on the normal 13a supply, but if that proves a problem I'll stick in a new 16a dedicated supply which isn't too difficult or expensive to do.

If anyone is interested it cost around £90 for the motor, £15 for flange and pulley and £10 for shipping from this chap here who proved very helpful http://stores.ebay.co.uk/electric-motor ... asstQQtZkm

If it all goes pearshaped for some reason then I may find an alternative use for the motor (can't think what though at the minute !) or sell it on and recoup some money, but hopefully it will all work out and I can get back to some serious resawing !

Cheers, Paul

 

[paulm]

The motor turned up today so didn't unfortunately have the opportunity to set it up over the weekend as hoped, but managed to make some progress this evening.

Glad to say the flange mounting chosen was spot on so it was nearly a case of unbolting the old and bolting on the new.

Almost, because I needed to find some longer bolts and use a bunch of washers to space the motor further back from the frame as the electrical box on top of the motor would otherwise foul on the bandsaw frame.

Luckily the motor shaft was a bit longer than the original so no problem there in setting it back a bit.

Another lesson learned was not to fit the new taperlock pulley on the motor shaft before fitting the motor as it proved impossible to then mount the motor after

A rummage around the garage failed to turn up the 3 leg puller thing that I know I have somewhere :-k , so a trip to Halfords and 15 quid later I manage to take off the pulley and remount the motor.

All seems to fit okay and the motor tightened up securely, so just need to take the wheel pulley off and turn it round the right way again :roll:, (hammer) line up again with the drive pulley, remount the wheel and then on to wiring up the electrics to the motor.

Hoping it will work okay on a 13 amp plug but it might blow under heavy load, will have to wait and see and put in a 16 amp circuit if needed. Anyway, the electrics will need to wait till the weekend when I, hopefully, will have a bit more time.

Cheers, Paul

 

[paulm]

All done and it works a treat \/ ccasion5:

Took a couple of hours this morning to finish installing, a minor amount of grinding to the new, slightly larger, pulley to avoid fouling the inside of the bandsaw wheel, connected up the internal electrics, and put a new blade on.

Tested it on another half log of walnut from Paul C and went through it like butter, no hesitation at all even in the 11" thick wet timber that I had previously had problems with.

Didn't blow the 13a fuse either so looks like no need for a dedicated 16a supply either.

So rather than spend a fortune on a new more powerful bandsaw, for £100 or so this one now does everything needed, and with ease

Just have to see if the motor lasts and is of decent quality, or fails after a bit of hard use, but at this stage I'm well chuffed.

Only thing is, with it being such nice weather today I need to get outdoors and do some gardening so no more time for the workshop :lol:

Cheers, Paul

 

[Jake]

Good news - and well accomplished!

 

[paulm]

Thanks Jake, was beginning to think I was the only one who finds this interesting :lol:

Cheers, Paul

 

[leptus]

great stuff paul i am glad every thing worked great . it will be great if you could supply some photos it will give other members some idea if they want to upgrade their bandsaw motors .i for one will be very interested .regards