Workshop electrics

[PeterBassett]

Hi all.

I'm in the process of turning my garage into a "Workshop" or sorts.

It's about 10x20 ft.

Can I ask some electrical questions?

It currently has two fluorescent strip lights and one double socket powered off of one 13amp spur from the house.

I've got a quote from a spark and he has said he can run a new 32amp supply to the garage with a small garage board for £350.

Does this seem reasonable to you? Does a 32A supply seem enough?

It would be an armored cable ran around the side of the house and under a small section of patio. I except I'll have to lift the patio my self.

At the moment I have a DeWalt 1501 radial arm and a small 1kw record dust collector.

Once the supply is upgraded I would put at least two ring mains. I would like to be able to isolate the radial arm so it can only be turned on with a key.

Three separate lighting circuits each with two strip lights. One set for each section between the two roof supports.

Once it is all in the spark says he'll test and certify it.

Does this sound sensible?

Any good suggestions or advice would be most welcome!

Thanks

Pete Bassett

 

[9fingers]

You might want to add a 16a or 32 amp socket of its own C class breaker to allow for a future purchase of a machine with a larger motor that might need more than a 13 amp fuse to start it.
Class C breakers are about the same price as the normal B ones but are designed for high surge loads like motors.

With what you are planning you might need more ways than what ever his idea of a 'small garage board' will provide. Best to check or provide it yourself for a suitable price reduction.

Bob

 

[RogerS]

Bob's madea good point. Typical boards for 'garages' only have two ways. By my count, you need at least four and that's without future-proofing.

Definitely get him to run in a 16A supply as Bob suggests.

Has he spec'd the size of thr armoured cable? Might be worth paying a bit extra and getting the next size up...unless he's spec'ing something meaty to start with. At least 6mm IMO.

You don't give any idea of location. If in Worcs then I know a good sparky for an alternative quote.

 

[Night Train]

The size of the cable will depend on the length and the conditions in which it is run to allow for heating and voltage drop. I have installed one for a friend that was 16mm sq armoured due to the distance.

It is worth running a supply that gives you a decent capacity on a distrubution board (fuse box) in the workshop with enough circuits to supply what you need.
It will protected at the house end of the supply with a fuse or circuit breaker to cover the maximum demand of the workshop and within the capacity of the supply cable.

In the workshop you can run whatever circuits you need as long as the cable sizes are protected by suitable size circuit breakers.

Probably a 32A ring, 6A lighting, 16A for any large machine that you might get and a spare for something else.
It is worth having a split board there so that the power circuits are protected by an RCCB.
Depending on the layout and headroom it may be worth considering having the power sockets on, or suspended from, the ceiling to save loosing wall space or having trailing leads.

 

[Digit]

If you're not into doing it yourself that sounds a pretty reasonable price.

Roy,

 

[Barreller]

£350 for the work, materials and a certificate sounds pretty fair to me.

Steve

 

[Jonesy]

As it stands I think you/'the designer' might have some problems as if you're having a 32A supply put into the garage then the design load on the supply shouldn't exceed 32A if you want it to comply with regs.

From what you have described the supply is going to feed a board supplying 2 rings (presumably both 32A?), the 6 strip lights - say a 3A load on lighting circuit, possibly another 16A circuit for a fixed appliance.

Now the design load on the board is not simply 32A+32A+3A+16A = 83A, as it can include an allowance for diversity eg that although you have all of those circuits you are unlikely to have them all fully loaded at any one time. Calculating diversity is tricky and will depend on the assumptions about how many people are likely to be working in the workshop, amount and type of kit etc but it is likely that the design load will be above the 32A rating of the supply. You may also have problems ensuring proper discrimination between the protection on the supply cable and 32A breaker on the board.

I'd go right back to the start, I'd list all of items of kit you have/want to have in the future and get figures for their load. Then take the worst case scenario of how many are likely to be in service at any one time, then use that the determine the requirements for final circuits and from there the supply to the garage.

If your setting up Norm Abram's workshop then you may need 2 x 32A rings, alternatively if it's something smaller a single 20A radial may suffice

 

[Digit]

Depends on how many machines you can run at one time. The most I have running at one time is one cutting machine and a chip extractor plus lights.

Roy.

 

[Night Train]

The most I draw with my workshop is about 3500w at any one time and even then it isn't for very long. Only me in there so one machine, extractor and lights and maybe a battery charger and radio.

 

[paulm]

Don't forget a 2 or 3kw fan heater for winter as well as a large band or table saw plus extractor,,,,,,,,,

Don't use the fan heater continuously but it can be on for a while to top up the background heat on a really cold day.

Cheers, Paul

 

[misterfish]

We recently had an extension built along with replacement of the old wiring and plumbing.

Part of the electrical system involved a feed to the workshop. This has a 50 amp breaker on the main board in the house which connects to the workshop using 10mm armoured cable buried nearly 2 ft deep in 2 inch trunking. In the workshop I have a 'consumer unit' with an RCD main switch along with 2 x 6 amp mcb for lighting, 2 x 32 amp mcb for two ring circuits with about 15 double sockets spaced regularly around the walls. There is also a 16 amp 'C' mcb for the table saw on its own dedicated supply. This is more than adequate for my hobby use. I also have 2 or 3 spare spaces in the consumer unit for future expansion.

At the most I run a 2KW thermostatically controlled convector heater, dust extractor, saw (table, band or RAS) and also a portable 'shop vac'. As for lights I have 2 outside 60w, 4 double 5 ft flourescent tube lights and about 7 lengths of track lighting with movable spot lights.

Although probably over the top I thought it worth while following annoyances with my workshop at our previous house (a cold, damp old milking parlour).

I have no regrets at putting all this in the 'new' workshop (as well as insulation!) as it makes working more pleasant.

Misterfish

 

[PeterBassett]

Thanks for all the replies.

I'm only one man and a rank amateur at that, however I do want to future proof the electrics.

The electrician will only be putting in the feed and garage consumer unit. I'll be doing all the electrics in the garage myself to save on money.

From what you have said I should probably be after a higher amp feed, 50a?

Thanks again!

Pete

 

[lurker]

£350 for the work, materials and a certificate sounds pretty fair to me.

Steve

Me too!
Assuming you are not going to run too much heavy kit at once this sounds fine. 6MM cable should future proof you enough.

I ran my workshop on a 13a extension cable for a long while and had no problems - much to my surprise.