electric cable size

[johnwill]

I have installed a tree house for my son. We want to install some power to it for an electrical standard home heater, 2 light fittings, 2 double socket outlets for general appliances.

The distance from the mains supply is 600 feet! Please could you tell me the size of cable I need and what other equipment I need to make it safe?

 

[Taylortwocities]

There are many, many things to consider.
600feet/200metres is a very long way indeed. The longer a cable run is, then the more volts will be dropped and so a much thicker cable is required.

How would you plan the run the cable from the house for 600 metres? That's a long way to dig a trench!

This sort of job can only really be determined by a site visit, and started by determining the supply type.

IMO, you need to find a registered electrician to carry out the necessary cable calculations for you. Also as this is a new circuit, it will be notifiable work, so you would need a registered electrician to do the necessary with the local authority.

 

[bernardgreen]

Assuming a maximum load of 2 kW and Steel Wire Armoured cable buried 450 mm below ground

Required Cable Size 16 mm
Voltage Drop 4.35 Volts.
Percentage Drop 1.9%
Current Load 8.70 Amps

At the house you will need a switch fused outlet to supply the tree house. Not on the RCD for the house in case a fault in the tree trips the RCD and cuts the power to the house.

You will need to make provision for movement and growth in the tree when planning the cable route from ground up to the tree house.

A garage type CU with RCBOs in the tree house would keep the lights on if the heater faults. Losing lights when needing to get out of a tree house could create a serious hazard.

An electrician to plan, design and install would make for a safer installation.

 

[PrenticeBoyofDerry]

What general appliances are to be used.
As stated 600ft is going to give you a voltage drop that a larger cable than would normally be required for your loads.

So to calculate your cable size, it would require to have an inkling of the load demands.
Room panel heaters could be 3kW, lights possibly 120w, then the socket loads could be nearer 7kW.
So more detail on expected loads would be handy.

 

[johnwill]

Assuming a maximum load of 2 kW and Steel Wire Armoured cable buried 450 mm below ground

Required Cable Size 16 mm
Voltage Drop 4.35 Volts.
Percentage Drop 1.9%
Current Load 8.70 Amps

At the house you will need a switch fused outlet to supply the tree house. Not on the RCD for the house in case a fault in the tree trips the RCD and cuts the power to the house.

You will need to make provision for movement and growth in the tree when planning the cable route from ground up to the tree house.

A garage type CU with RCBOs in the tree house would keep the lights on if the heater faults. Losing lights when needing to get out of a tree house could create a serious hazard.

An electrician to plan, design and install would make for a safer installation.

 

[ban-all-sheds]

Indeed he did.

 

[JohnW2]

Thank you for your replies, very helpful. I have checked the price of 600 feet (200m) of cable at 16mm and the cost is astronomic!!

Quite so, and even 16mm² would theoretically not be adequate (in the terms of the guidance maximum 3% voltage drop for lighting) if your load was actually more than about 3kW. Add to the cable cost the cost/effort of burying 200m of cable, and it really does not sound like a very realistic approach!

Would a silent generator be better and if so what size do I need and would I be able to just connect a household plug, socket outlet, light and heater into it ok?

A generator certainly sounds more realistic, but that would also raise various issues, and you really need an electrician on-board to give advice.

Kind Regards, John

 

[westie101]

Have a look at PV and batteries as used in the caravan industry, lots of purpose made equipment readily available.

Whilst heating would be out TV's etc. are possible

 

[bernardgreen]

When I was young tree houses were sites of adventure with candles and copies of the Beano and Dandy. The luxury ones had electric lamps that were torch bulbs running off batteries. Buying them was a large lump out of the pocket money. The radio was a crystal set with headphones.

I personally did not have a tree house as there were no trees in our garden. There was a group owned one in the local forest which the Forest Ranger never found. ( Later we discovered he knew all about it but as we were well behaved and did no serious harm to the tree he forgot to report it. )

 

[bernardgreen]

If you go for 12 volt or 24 volt equipment running on batteries located at the tree house then one option could be to continuously trickle charge the batteries using ELV (Extra Low Voltage ) cabling from a charger in the house to the batteries.

By using a constant current charger in the house the voltage drop along the cable would not be a problem provided the charger could provide the necessary voltage on it's output ( V out = Battery voltage + voltage drop along cable ) Much thinner ( and cheaper ) cable could be used.

 

[ericmark]

It does depend how much it will be used but likely a generator of some type will be a better option.

Generators come in many flavours in another post you talk about silent generators and the WisperGen which uses an external combustion engine of the Sterling design is very low noise output but also expensive.

Having a generator which can tick-over will reduce the sound when not being used there are two types. One revs up as soon as any load is put on it and the other uses an inverter and only speeds up gradually to match the load.

The inverter type is normally petrol and not as expensive as the Sterling but still expensive.

Of course move to non electric heating and the cable costs drop. If you carrying fuel for a generator why not carry it for a heater.

In the trees you could use an alternator on the trees. Depends on power required but used a bicycle hub dynamo very well for lights it was just a spring well buggy ties really and some blue cord wrapped around dynamo spindle and fastened to top of tree. As tree swayed in the wind the dynamo produced 6 VAC rectified to DC into battery and switch to LED lights.

There are sorts of options in the woodland solar power not really an option though.

For simple lighting even 2.5mm² cable may be enough but have you ever tried feeding cable through a woodland?

 

[westie101]

I'm struggling with the generator idea.
Is the child expected to operate it and refuel it themselves or is it a case of: -
Dad I'm going to the treehouse will you start the generator
Dad the generator has stopped, dad finds it needs fuel so has to go for it then finds on his return son has found something else to do
Dad I'm finished in the treehouse you can switch the generator off!

I'm sure there are many more!!

 

[JohnW2]

I'm struggling with the generator idea.

You make very valid points, but a 200m LV feed is also pretty unrealistic. If the loads were very modest (certainly not including heating), then probably batteries (your PV charging and/or bernard's ELV feed) would be the most practical approach.

Kind Regards, John

 

[westie101]

Though I know it will be said to not meet regulations (really) In the same circumstance I would also consider a high level option with some split concentric.

Manufacturer information we have tells us we can span up to 33m at a time which would work in a tree covered area, given that as it is for a child would possibly have a maximum installation life.

Fastening to a tree with a suitable bracket using overhead line connection with some 2.4mm singles no problem.

I have in the past done similar over a shorter distance using 4mm2 split

 

[bernardgreen]

Be interesting to know how old the son is. He could be a 30 year old and the tree house is to get him out of the parent's house. In which case a genny would be OK