The Power we need

[woodndesign]

It has come up under the post by edbanger on Bandsaw Help, so as not to divert his post and nor lose the subject I've started here with what Electric supply/Power is needed for safe operation in our workshop domain.

Comments so far:

You may have 20 x 13A sockets but please forgive me for asking if have you checked the rating of the fuse or circuit breaker at the Consumer unit?

MC

Very wise comment, MC, as I read that most equipment can call for 20A supply.  If I recall correctly from the quote for when I get the power for the shop, I'd need 45A to cover my estimated demand etc... how many things could be running at any time.

Cheers  David

I  hope I'm  NOT teaching my grandmother to suck eggs when I  write this...... (to coin a phrase)

Every piece of electrical equipment should  have a RATING PLATE showing how many watts (W) or kilowatts (kW) the machine uses.

For all practical purposes and for ease of calculation, every kilowatt (=1000 watts) draws 4 amps (4A)

The machine should  have the correct size fuse in the plug - but a lot of electrical equipment is  supplied with 13 amp fuses [incorrectly]

Why are you  likely to have more than one machine running at a time (apart from extract systems, et hoc genus omne)?

This assumes everything is  SINGLE PHASE. Three phase gets more complicated!

With seasonal greetings and my very best wishes for a Happy, Healthy, Peaceful, Successful, Prosperous and Stress-free New Year.
 
MC

In an ideal world, sufficient capacity to cover what the rating plate would be enough. In the real world, things with big motors have a starting current that will exceed the stated current on the rating plate by quite a margin so it's not unusual for a more substantial supply to be needed.

Regards

Paul

There is a need to understand of what our equipment demands, and sound advice as to what to look for and awareness.

I'd contacted an Electrician, giving my needs and he quited a comsumer box, 6' strip light and a double socket .. how little he understood my requirements ... I then listed and sent a full list of all the current equipment ratings/wattage/amps an the lights and sockets I would like.

Since that I'll 10mm cable an without checking 45A at the house outlet ... and about triple the cost, but then what price for safety.

Cheers David

[Paul Hannaby]

David,
I think you have missed the point. This doesn't really have anything to do with safe operation.

[MCB]

I  have an NVR switch attached to the leg of my bench where I  can hit the red mushroom with my knee.

The lathe power cable plugs into a 13A metal clad socket beyond this switch and the power to it comes from a normal wall mounted double socket.

There is, of course, a switch on the lathe too but I  felt that having a switch with an emergency stop would  be beneficial.

MC

[woodndesign]

David,
I think you have missed the point. This doesn't really have anything to do with safe operation.

Are you dismissive of the possibility from a professional stand.  As couldn't a large amperage burnout the likes of a 13A cable supply, if not blow the fuse/breaker first, else why are there manufactures warnings that a machine is rated 20A or the fact that I've been advices as to the need for a 10mm cable and Armoured at that, by an Electrician.

I hope that when I do get the shop wired that it should be safe for my long term requirements, much as RC has with his shop.

[Paul Hannaby]

David,
You seem to be repeatedly quoting my posts out of context so I will clarify what I meant.

My point about supply needing to exceed motor rating was intended to highlight the problem found by some when installing a large machine on an inadequate supply would result in blown fuses or tripped breakers due to the startup surge, not a continuous overload.

I don't recall mentioning 20A machine rating or 10mm cable armoured or otherwise. Choice of cable would be dependent on the requirements for the installation.

[davidbrac]

I have found an issue with some equipment, mainly a hitachi mitre saw, tripping a breaker on start up even thought the rating of the trip were correct. seeing this was a single spured socket (not a ring main) l increased the trip amp from 15 to 20 - now no problem.

[TONY MALIN]

I would be interested to know how you increased the trip. I assume on a breaker not fuse. But as far as I know the breakers in a domestic consumer unit are not adjustable. Assuming the motor is of the order of 1/4 hp I would not expect it to trip a normal 13amp circuit. We're you stalling it?

[MCB]

It's a well known application of S*d's Law that an expensive machine will often protect the fuse by blowing first!

Perhaps Davidbrac can reveal  the rating of his  cable connected to his uprated breaker.

MC

[Doug Barratt]

I have found an issue with some equipment, mainly a hitachi mitre saw, tripping a breaker on start up even thought the rating of the trip were correct. seeing this was a single spured socket (not a ring main) l increased the trip amp from 15 to 20 - now no problem.

Presuming your 15 amp breaker was a type B a better course of action would have been to change it for a 15 amp type C or even D.

[Derwent Woodturning club]

I have found an issue with some equipment, mainly a hitachi mitre saw, tripping a breaker on start up even thought the rating of the trip were correct. seeing this was a single spured socket (not a ring main) l increased the trip amp from 15 to 20 - now no problem.

Presuming your 15 amp breaker was a type B a better course of action would have been to change it for a 15 amp type C or even D.

I hope the spur was done with at least 2.5mm T&E cable or you have just over rated your breaker (20A) for the cable and are now using the cable as a big fuse

1.5mm T&E is rated at 18A, so ok with a 15A breaker but not with a 20A one, and having only the one run of cable i.e. a spur rather than a ring means it is only one length of cable feeding the socket whereas a ring 'shares' the load round each side of the ring.
Keep it safe from all aspects.

[TONY MALIN]

I've now checked out two makes of mitre saw. Both 1800 watts or 2.4 HP. I'm surprised.

[woodndesign]

I have found an issue with some equipment, mainly a hitachi mitre saw, tripping a breaker on start up even thought the rating of the trip were correct. seeing this was a single spured socket (not a ring main) l increased the trip amp from 15 to 20 - now no problem.

Presuming your 15 amp breaker was a type B a better course of action would have been to change it for a 15 amp type C or even D.

I hope the spur was done with at least 2.5mm T&E cable or you have just over rated your breaker (20A) for the cable and are now using the cable as a big fuse

1.5mm T&E is rated at 18A, so ok with a 15A breaker but not with a 20A one, and having only the one run of cable i.e. a spur rather than a ring means it is only one length of cable feeding the socket whereas a ring 'shares' the load round each side of the ring.
Keep it safe from all aspects.

Hi Paul, so good to see sound advice, I for one have little understanding of electrics, wiring plugs, fuses and changing bulbs at best, other than past work which I've had done, and has that been correctly done/adviced. Recent wiring in of a shower went from £100 to a bill of £300+... I'm sure I'd paid for the whole 10mm reel the supply needed ... Same guy quoted the shop wiring.. a guess on the distance to the shop for the cable run, likely the same iffy pricing too, as the second quote jumped having listed the equipment, points and lights I'd hoped to use.

In inview of my needs, albeit not Industrial, the equipment loads differ from those of domestic appliances. I've a blank canvas, so advice is most ideal, as are ideas of what others have done or would have done differently.

I've found in various workplaces I've worked, there's never enough power points, let alone a lack of lighting over benches, (count the points in any kitchen or the number of extention leads elsewhere in the house) I see the need for 4 points at the lathe, even if I'd have it hard wired, as once before, if not the same points at other equipment for worklamps, other power tools and any additions in the future, I'd consider the less spurs/extentions used the better.

It would be of benefit to other members who are embarking for the first time with setting up, even those remodelling a workspace to have any relevant information.  As well as any nearby member who's an Electrician even.

Cheers  David

[TONY MALIN]

Hi David
Bear in mind power showers can be up to 8.5 kW and likely to be the heaviest load on your system. It must be properly wired.

[Doug Barratt]

Hi David
Bear in mind power showers can be up to 8.5 kW and likely to be the heaviest load on your system. It must be properly wired.

At the risk of sounding pedantic which isn`t my intention, more just to clear up a misconception,  a power shower is predominantly a shower who`s water is pumped, the water being supplied from a hot storage vessel such as a hot water cylinder. As such the electrical power consumption is quite low.

Electric showers heat the water as it passes through the unit requiring a large electrical supply as they are now available up to a rating of nearly 11KW

[MCB]

When I  told the electrician who wired my shed initially that I  needed more sockets on the back wall (where there were previously none, he told me to get a four gang extension and just plug it in to one of the existing sockets (on the front wall).

I  found a six gang socket with each being individually switched and connected that with a flexible cable which I  secured to the walls with little cable clips. Since I  don't have more than one machine running at a time, there's no risk of overload.

Accepting that there may be factors of which we are NOT aware, I  think I  would  have considered the increase in cost of the shower installation and then invited at least three electricians to quote for the shed/workshop rather than just going back to the first man.

Of course, if he was your wife's second cousin, you would  NOT have had the choice!

My very best wishes for a Happy, Healthy, Peaceful, Successful, Prosperous and Stress-free New Year.

MC