Calling All Sparkies Out There

Why not go the whole hog and run a separate cable with a separate fuse direct from the fuse box or supply point, as if you tap it off the lighting circuit you risk overloading the wiring with the light and heater / extra load on, the danger being that someone WILL ignore any label and plug in something heavy duty !

 

There are several factors you need to take into consideration before attempting this work.
The cabling is probably 1.5mm T&E(twin & Earth) and is implemented in a 6 Amp ring. This ring should not be spurred for power use, protected by a fuse or not. It is implemented for lighting use only. If it it is a long distance from the main distribution board, then the distance will add loading (by resistance) to the 6amp circuit anyway. Your 5amp requirements could easily be on the maximum for this circuit.
With respect, I would leave it alone, or get a proper current carrying SWA (Steel Wire Armoured) feed to the outbuilding

 

What happens when someone plugs a device into said marked up socket, requiring a 13Amp supply?

Overload,......hopefully if a MCB or RCD is at the main incomer, then the fuse will trip...... real world, could be a fire.

 

You don't put fused spurs in 6 amp lighting rings.... full stop!
Fused spurs are allowed for 20 &32 amp ring mains or as a single radial!
You asked for professional advice..... but do as you wish and bear the consequences!

 

Looking at it from how I see it there is or supposed to be a 1.5 Twin and earth going a very long way to service a number of garages and these things end up with ‘hot spots’ that you personally wouldn’t be able to get access to if it just happened to be in another garage. As time goes on these junction boxes need nipping up as screws and copper cables settle down with the flow of current. Adding to it in the form of a low watt heater can push it over the edge. It might work if you cheated the system with a trickle charger but play safe and use another heating means.

 

You could fit a spur to a 5amp round pin socket but why bother?

For £100 in parts you can run an armoured cable from the domestic consumer unit to a mini consumer unit in the garage (25m enough?) and have a few 13A double sockets.

You should be able to do 95% of the work yourself even even if you get a sparkie in to make the final connection. Leave the face plates off so he can can check you work.

The wiring regs exist for a reason.....to save people from themselves.....

As to what you plug in a cheapy dehumidifier might be more effective.......but most garages leak so much air neither will do much good unless you bag up what you wish to protect and dry that air.

 

Exactly, ..... example 10 garages on a 5 amp ring, a 60 watt bulb in each, ohms law gives a consumption of roughly 0.25 amp per bulb, this equates to 2.5 amps for the total garage block. Start doing bodged wiring in a few garages, the result would be an overload, tripping a breaker! In the worst case, if the consumer unit is an old hard wired fuse jobbie a overheat of the cable before the fuse wire ruptures. Personally even if there was a power source in the garage, I wouldn't leave an unattended heater for a long period of time. Seen to many burnouts in my time........ be lucky!

 

I wouldn't leave an unattended heater for a long period of time. Gas or electric.

Sounds like a non starter mate.I have a council lock up with no power and it has so far not been an issue. I just try to run the bike as often as possible. and I put in vents to try and keep down the condensation.On the other hand, at least you have a light.I have two rechargeable torches and I leave the door open.

 

On reflection I have applied some military logic (not intelligence!) to your problem. A ‘mission’ is expressed as ‘do x in order to achieve y’. It is not always obvious but the really important bit is y.
You are focused on the electrics but your intent is to preserve the garage contents. Your first question should be about the best method of preservation. Dry air is your friend. A lot of this stuff is best left in the airing cupboard in open bags then taped shut when bone dry and stored in the garage. Cold is not the problem. Condensation will be OUTSIDE the protective bag. The Bantam is probably best sprayed in ACF50 etc., before being laid up. Batteries come into the house.....
Just a thought. I am now shut up.

 

how about an infra red light bulb for some heat ?

 

BANG

https://en.wikipedia.org/wiki/Fire_triangle

 

Okay, so we used to use low wattage heat lamps in a barn where the pigs were farrowing - We managed to do it without having a fire (admittedly it was only over a period of 15 years or so; either we were very lucky or every pig farmer that uses heat lamps is doing it wrong and is also lucky!)
With respect, probably not wired on a 6 amp lighting ring!

Why would using one of these heat lamps create the conditions for a fire any more than other heating methods? (Unless you use one of silly high wattage)
Most IR lamps are 175 - 250 watts, do the maths!

If something did go wrong the breaker would trip well in advance of any wiring being endangered.
That will please the other garage users, heating your garage? and tripping the main breaker. Waiting for someone to rest the RCD?MCB or RCBO!

That said, I had a chat this morning with the developer who built the garage blocks (along with the houses around it) and next time his electrician is on site he’s going to let me know so I can chat through the options, one of which will be putting a ring from the main RCD unit to my garage.
Sounds like the way to go!

Be lucky