Current garage electric supply.

[The Bear]

Some of you will be aware my workshop is in storage after moving house. With so much to do on the house I think rather than build another dedicated workshop straight away I'm going to set up shop in part of the double garage. This may be my workshop location for the next 5 years . I need to get an electrician round to quote on the work but I'd like to know what I already have.

There is an underground feed to the garage , but it literally runs 1 double socket and a strip light

It goes first through the rusty metal box then to the small breaker unit

Does this mean I have a 63 amp feed already or is it not that simple? Or do I need to measure the cable size and length ? And do I need to check the house end cause that looks complicated (and antiquated) compared to my old house which I had rewired.

Mark

 

[monkeybiter]

Regardless of the breakers in the garage you need to know where it's fed from.
You could open the garage door, plug in the radio and turn the volume to full [ 11? ]. Then in the house with the window open, keep throwing breakers until the noise stops, hopefully it will at some point. It should be fed from an RCD I think in case the underground cable develops a sudden garden fork ingress.
Once you know what the supply is capable of you should assess the cabling to the garage, this may be less [but should be more] than the supplying breaker. After all that you can decide if the breakers in the garage are over-optimistic or unnecessarily limiting.
HTH

 

[Monkey Mark]

Agree with everything said above.

It's hard to tell from the picture (can't estimate scale) but that doesn't look like a very substantial cable. If it's only 2.5m then you're talking 16amp as it's a spur or radial circuit if that's the only cable coming in.

 

[Alexam]

I had a similar situation here. Having moved in 15 years ago, the supply to the detached double garage seemed fine until I started woodworking couple of years ago. When adding equipment and heaters, the fuse kept popping, so I called in an electricial and found that the underground supply from the house was just a spur from a 13amp plug in the nearest room.

A rewire was called for, but with difficulty to break into the main fuseboard in th house, as I did not want to see ugly thick cable in that particular location, we decided to run a large wall cable which he managed to push 5' through the wall space/void to the mains input box and space to put the RDC breaker in. Now I have ample 16amp outlets as well as the old 13 amp connection which we decided to leave in situ, just in case the main breaker cut out. That way we would have one socket still live from the house and seperate, which is hooked up to the overhead bench strip light.

Cost abot £250 this year, but well worth it

 

[mseries]

The 63A on the Harok VKL001 (http://www.harok.com/) is tellling you only what that piece of equipment is rated at, it doesn't state what current is supplied to it. if you draw 100A through it it will trip, not with 40A though. B10 and B6 on the VKL007s indicate 10A and 6A respecively for those circuits and I suspect these are what your sockets and lights are wired into. Whether or not your cable is suitable to supply these currents is another question. As the other have said you need to find out where it's fed from. If you are in doubt and/or if it's old and deteriorating have it replaced. That rusty box doesn't fill me with confidence TBH. NB I am not an electrician, just learned this stuff from my Dad who spent his career wiring machines in foundries and factories

 

[damo8604]

=D> for the Spinal tap reference!

 

[n0legs]

In the picture of the "rusty metal box" is the cable coming in at the bottom the assumed feed into the garage?
From the picture it looks like MICC/MIMS also known as "pyro" (mineral insulated, copper clad with a pvc outer sleeve), can you get a better picture of the box.
If it is pyro I really do impress upon you to have the cable tested. Don't panic yet, are you using the supply in the garage?
Why I'm concerned?
Because the copper sleeve is sometimes, depending on the cables number of conductors, used as the earth. From what I see in the picture there seems to be some corrosion/rot just above the orange coloured plastic.
The earthing arrangements may be compromised and possibly the sheath has rotted enough to allow water in that can cause other problems.
MICC/"pyro" cable was often used for the short run under the path between the house and detached garage because it was generally considered to be so tough. The downside is the copper sheath rots away if the pvc was abraded or punctured.
Please take care until you know exactly what you've got and what it's condition is.

As said by others, the numbers on the newer breakers are the max load for the RCD, then 10 amps and 6 amps for the MCBs feeding the circuits.

 

[The Bear]

Thanks for the replies
Monkeybiter, I'll try what you said in the next couple of days
Monkey Mark, its hard for me to be sure but the cable in does look smaller than I had in my old workshop
Alexam, I too am going to have problems running a new cable to the garage. First the house gubbins are on a solid floor and I cant see where the garage cable goes. The room the house gubbins are in is due to be demolished as I have just got planning permission, which isn't a problem but I don't want to much effort at the house end as it'll be coming down and new board going in then (probably 2017).
Mseries agreed on the metal box
Damo
N0legs I'll try for a better pic of the metal box

Mark

 

[The Bear]

Here's the house end if it helps

 

[The Bear]

A slightly better pic showing the bottom of the metal box in the garage

And I only noticed today this loop of what looks like twin core and earth looping around where the garage feed enters

Mark

 

[MMUK]

That looks like mineral insulated (MI) cable. If you pop the front of the fuse box off in the pic, the cable should be terminated in a resin pot.

Adequate for a few sockets and lights but not for a full workshop setup.

 

[n0legs]

Here's the house end if it helps

Ok, the metal box in the middle/corner appears to be the feed in the MICC cable which I think is the one going to the garage. Operating the switch should turn off/on the supply. Give it a try.
It appears from the picture the whole set up could do with some tidying and updating, that's for another time though.

 

[n0legs]

A slightly better pic showing the bottom of the metal box in the garage

And I only noticed today this loop of what looks like twin core and earth looping around where the garage feed enters

Mark

Right, top pic.
Point out to the electrician the area of corrosion just below the cable gland/above the orange sheath , voice my concerns. It looks a little rough but could be just in need of a little cleanup then over taping, it does need an inspection at the house end aswell and a test if it is to be used. It might still be useful.

Bottom pic.
The twin and earth I have no idea of. Do you have a non-contact tester to find out if it's live or not. Screwfix were selling some on the counter the other day for a fiver I think, in my opinion they are an excellent idea for any DIYer. Prove it first on a known live source, test what you need too then prove it again immediately after you've carried out your test on the known supply.



I'll kind of address MMUK's comment here.
It depends on the size of the cable whether it will be any good as a permanent supply, the intended load applied in the proposed workshop is also a factor.
From the pics it appears to be of quite a decent size, compare it to the courses in the blockwork and the T&E on the floor.
A 4mm 2 core is approx 10mm diameter, that's got the potential for a 35-40 amp supply depending on how it's installed. It needs further investigation.

What The Bear needs is a good electrician who's willing to take the time to inspect and test what is already there, remember running a new cable could involve some digging and disruption. Then advise depending on what Bear's requirements are.

If I found the cable to be in good condition and of a suitable size I would re-terminate the cable into a new isolator in the house, then in the garage install a metalclad consumer unit. Wire circuits as required, sit back and enjoy.

 

[MMUK]

Fair comment but there's no way that MI is more than 1.5mm. The copper sheath may well be 10mm diameter but the cores will be much smaller than the equivalent in PVC.

 

[n0legs]

Fair comment but there's no way that MI is more than 1.5mm. The copper sheath may well be 10mm diameter but the cores will be much smaller than the equivalent in PVC.

Without the benefit of actually being there and measuring it or checking its csa with a gauge I'll just have to guess for now. I've seen this before many times and I'm pretty sure it will be 2 core 2.5mm heavy duty MICC, hence the orange outer sheath. What exactly is the equivalent in pvc?
It's outer diameter will always be smaller than a pvc cable due to not having multiple layers of thick pvc outer sheath and insulation, 16mm we used to use as sub main in flats was only just over 1/2" diameter, certainly less than 3/4"
If it is 1.5mm that still has a load potential of 25 amps depending on method of install.
It depends on what Bear wants and needs.

Edit to add,
Here's some tables for you to read MM
http://www.batt.co.uk/upload/files/micc ... 051134.pdf

 

[MMUK]

Already have those tables matey. Your point is?

 

[n0legs]

Already have those tables matey. Your point is?

Really matey, you all ready have those tables? Yet you didn't realise the outside diameter of MICC can be so small and the conductors can be so big.
You seem intent on causing an argument when there is no reason to make an issue.
Fact is until someone actually gets their hands on the cable in The Bears garage none of us will know it's exact size. I'm offering The Bear some information and possible solutions.

Shouldn't you be looking at the tables for trailer bed loading and construction :wink:

My point................
We'll best just leave it there eh! :wink:

 

[MMUK]

Already have those tables matey. Your point is?

Really matey, you all ready have those tables? Yet you didn't realise the outside diameter of MICC can be so small and the conductors can be so big.
You seem intent on causing an argument when there is no reason to make an issue.
Fact is until someone actually gets their hands on the cable in The Bears garage none of us will know it's exact size. I'm offering The Bear some information and possible solutions.

Shouldn't you be looking at the tables for trailer bed loading and construction :wink:

My point................
We'll best just leave it there eh! :wink:

Maybe you should occasionally practice what your signature preaches.

MY point.............

Sod it, I got better things to do

 

[The Bear]

Easy tigers, I appreciate both your help and advise. And I do realise I need a sparks for full confirmation,I'm just trying to see what I can work out before and be pre armed so to speak.

I suspect my load requirement is reasonably large, the table saw, planer, bandsaw and dust extractor are all 16 amp. I understand the draw is greatest on start up and indeed had to change the breakers in my old workshop to stop tripping on start up. I'll have the extractor and 1 other machine on at a time.

Mark

 

[n0legs]

I suspect my load requirement is reasonably large, the table saw, planer, bandsaw and dust extractor are all 16 amp. I understand the draw is greatest on start up and indeed had to change the breakers in my old workshop to stop tripping on start up. I'll have the extractor and 1 other machine on at a time.

Mark

You still have a few options.
You could have the garage completely rewired and a new supply installed,one that is more suitable for the proposed demand without impeding your plans for the house.
A new supply cable could be left long ready for moving to the new house location, or could go to the existing position and be jointed later to make it longer to go to a new location.
You could run a suitable overhead supply, saves digging out the house floor, then lengthen this cable on the internal side when the building work is completed.
Whatever you do think big. I posted a while back about this. If the spark suggests 6mm SWA go for 10mm, leave yourself some room for growth. Fuses and breakers can always be changed to provide more, the choice of cable is the limiting factor.
Also insist on a three core supply cable, don't rely on cable armour to provide an earth (this is one of my little quirks, but it is a worthy one).