Armoured Cable - What Size for 80' run??

L

Lionheart

Joined
14 Mar 2014
Messages
27
Reaction score
1
Location
Herefordshire
Country
United Kingdom
Hi guys

I need to run an armoured cable from our electric supply to our new garage build. It sits around 80 feet from the house, and I will be using power tools etc in the garage.

What size of cable would I need to cover an 80 foot run?
 
Sponsored Links
I'd be looking at a 32A circuit, running some quick calcs on TLC's volt drop calculator with a distance of 30M (a litte more than you specified but people often underestimate cable length) and using the "lighting circuit" volt drop rules (since this will almost certainly be supplying lighting) you'd be looking at 10mm.
 
I think what you are getting at is the idea that a longer run of cable will require a bigger size due to a drop because of the distance. The professionals on here will tell you the answer but I don't think it makes any significant difference.

The key issue is what you will be running the other end i.e. the size of what you will be expecting to supply.

You need to work out exactly what you will be having first e.g. just one socket and a light will require less thickness than 4 sockets and 3 lights.

If you work this out then ask on here they may tell you the answer you seek.
 
Sponsored Links
Hi guys

The use at the other end will be relatively heavy. I'd run a ring of sockets (6 sockets, plus quite a few lights (it's a four car garage).

I'll be using power tools for sure, plus heater, air con unit etc. Doing a lot fo work on cars, so all related tools really.

Does that help?
 
Belboz said:
You need to work out exactly what you will be having first e.g. just one socket and a light will require less thickness than 4 sockets and 3 lights.
Click to expand...
Number of sockets and lights isn't massively relavent. Lights are a relatively trivial load and sockets are just connection points.

What really matters is the equipment that is likely to be in use at the same time. You need to think about what equipment is likely to be in use at once, look at it's current requirements, round up to the next standard breaker size and then calculate a cable size to match.

My initial post was based on the assumption that this was a fairly normal domestic garage and so 32A would be ample but lionheart's latest post is now implying it's a place used for fairly serious work on cars.

I suspect 32A will still be sufficient if there is only one person working in the garage at a time and the heating/aircon is a small portable unit (e.g. one that can be run off a 13A plug) but if multiple people are likely to be using power tools in there at once i'd want to go higher than that.
 
Thanks plugwash.

That's what I was trying to get at when I said

'The key issue is what you will be running the other end i.e. the size of what you will be expecting to supply.'

I just didn't explain it as well as you did.

:oops:
 
Thanks guys!

No, it would be me working solo. I am going to run a 32 amp ring main and also lights.

General power tool use, plus heater or air con unit. Nothing amazingly drastic, but it certainly will be worked in daily (by one person).

What do you think would be suitable?
 
As I said earlier based on a 32A circuit used to supply lighting and a slight rounding up of your distance I came up with 10mm. That assumes that the limiting design critera is volt drop (it USUALLY is but there may be exceptions) and that the circuit is fed from the origin of the installation.

If you are going to be getting an electrician to connect up and certify it is important that you get them involved from the start, since they have to be satisfied that the type, size and installation method of the cable are satisfactory. They will likely also be able to source the cable cheaper than you will.
 
Hi guys

Problem has arisen. We need to run the cable a different route, which means it's nearer the 45m - 50m mark

Would 10mm still be suitable?????
 
Lionheart said:
Problem has arisen. We need to run the cable a different route, which means it's nearer the 45m - 50m mark ... Would 10mm still be suitable?????
Click to expand...
Strictly speaking, not quite (in terms of lighting voltage drop with 32A and 50m). The next size up is 16mm².

Kind Regards, John
 
EFLImpudence said:
JohnW2 said:
Strictly speaking, not quite (in terms of lighting voltage drop with 32A and 50m).
Click to expand...
Oh, that's a bit strict. Isn't 49m (less final lighting circuit) the actual limit for 3%.
Click to expand...
I did say "strictly" :) You're right at 70°C (i.e. PVC), but I think the limit is more like 45m (less final lighting circuit and anything else upstream of the SWA) at 90°C, so it depends on what cable is being used.

You and I both know what the pragmatic answer is, in either case, but that's a different matter from 'advising'!

Kind Regards, John
 
With a correction factor of 0.94 I get volts just within limits at 50 meters 6.6 volts using 10mm cable when using a 32A supply.

I have many times questioned using a 32A supply in a house to feed a 32A plus a 6A MCB in a garage as in theory the house MCB will trip first. Yet feeding with a 32A MCB to a garage consumer unit with 2 x 16A and 1 x 6A MCB I would consider OK even if garage had 4 x 16A I would still consider it to be OK.
 
D

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
You must log in or register to reply here.
Sponsored Links

Similar threads

A
Armoured cable to garage
Replies
4
Views
774
ericmark
ericmark
M
Running armoured cable
Replies
3
Views
1K
ban-all-sheds
ban-all-sheds
M
Armour cable
Replies
2
Views
1K
Mazda
M
A
Armoured Cabling
Replies
5
Views
1K
Simon35
S
J
Which armoured cable???
Replies
9
Views
369
robinbanks
R
Back
Top