What size SWA cable for Outdoor Electric Gate and lights

[HarveyDIY]

OK thanks all. I have had some useful advice here. I'll get service ducts in first and that gives me flexibility to get right cables in when it comes time for it.

thanks

 

[ban-all-sheds]

The twinwalled stuff is what you want - the outer wall is ribbed for strength, the inner is smooth for ease of pulling cables in.

This sort of thing: http://www.drainageonline.co.uk/Ducting/Black-Twinwall-Duct-x-50m-coil.htm

It comes with a drawcord, but it's a bit pathetic - might be a good idea before you bury it to use the supplied one to pull some stronger rope through.

 

[ekmdgrf]

It is. And the "Y" in "DIY" stands for.....?

It stands for "Yourself". I see the point which you are making, that the OP should do the work himself and not seek the help of others. This is somewhat an irreconcilable incongruity with your previous statement that the OP should get someone else to do the work. Nevertheless, that's irrelevant as my forthcoming piece of pedantry will demonstrate: while this forum does indeed fall into the genre of DIY, specifically, it's called DIYnot. This is a (slightly) clever play on words, the idea that ostensibly one is doing the work oneself, yet in effect, they are not, as they are taking advice from the forum collective. Do you see how it works?

I do have one little puzzle, which relates to what appears to be your paradoxical approach. It may be argued that your stonewalling of posters to this forum is an attempted to save life and limb. Nevertheless, if I may be as bold as to offer my humble opinion, I do feel that somewhat ironically, your approach is more likely to affect the opposite outcome to that which one might believe that you are trying to achieve. In my experience, people don't really respond well to insulting instructions from strangers, so your efforts are likely to be fruitless. They tend to ignore you and carry on doing what they are doing. A little friendly guidance however might encourage them to adjust their course. There is of course, perhaps a slightly more sinister explanation, that you find a certain amount of self gratification in insulting those whom you see as ignorant plebs. If that is the case, there is little advice that I can offer other than to enlist the help of a psychologist.

 

[JohnW2]

[... it's called DIYnot. This is a (slightly) clever play on words, the idea that ostensibly one is doing the work oneself, yet in effect, they are not ...

I don't know if it is true, but I have been led to believe that "DIYnot" came about as a contraction of "DIYYnot" - a.k.a. (phonetically) "DIY - Why not?".

Kind Regards, John

 

[flameport]

although I will probably need to use a waterproof FCU at the gate pillar to protect the lighting circuit from the 2.5mm cable. I understand that if I make this 2.5mm supply from the garage a radial then it can support up to 20amps.

2.5mm will not be suitable for 20A over a 30m length, more like 10A maximum.
4mm cable would be a better option, as this will also allow for a 13A socket outlet installed with the control equipment, so that power tools and other items can be used at the gate position for when they require repairs.

You don't need a waterproof FCU - put all of the lighting and gate controls into the same waterproof cabinet (which will have to purchased separately - the tiny little plastic boxes supplied with gate controllers are useless and should not be mounted directly outside).

For now, ducting is the best option as already suggested by others, at least 55mm diameter.
2 lengths from garage to one side of the gates (where the control cabinet will be), and two more lengths from there to the other side of the gates.
You will also need to get cables from the garage to the house for the intercom and other controls.

Underground motors should be avoided.

 

[stillp]

Also please browse the HSE's advice on powered gates:
http://www.hse.gov.uk/search/search...ates#gsc.tab=0&gsc.q=powered gates&gsc.page=1

 

[ban-all-sheds]

PLAN B

• Drive up to the gates
• Get out of the car, open the gates
• Get back in the car, drive in or out
• Get out of the car, close the gates

Cheaper, more reliable, safer.

 

[HarveyDIY]

So I was speaking to a colleague of mine about the discussions in this post and apparently one of the other guys at work used to be an electrician. So I met with him and discussed and he was nice enough to explain what an electrician may recommend.

So he explained the obvious W=AxV and the watts in 24v or 230v is the same. The motors are rated a max draw of 15A @24v = 360W. The panel can use another 50W for other bits. Overall the absolute max is 500W for panel and motors and accessories. So 550W/230= 2.2A @230V. Allowing for inefficiency he said lets just call it 3A @ 230V.

Now for the garden spike lights and pillar lighting most of it will be low voltage led but said allow anyway 1500W @230V = 6.5A.

Although I dont need and will never use that much power he said to allow for 13amp for sockets for other seasonal lights or running tools. So gate automation 3A + lighting 6.5A + socket max 13A = 22.5A

So based an absolute max loading of 22.5A @230v which based on what I actually need is more than enough he recommended at least 4mm or even 6mm SWA from consumer unit to gate pillar.

Now he mentioned the volt drop for lenght of cable and cable rating drop for burying into ground due to heat. Cant remember exactly everything but 4mm/6mm SWA is rated way over my max 22.5A requirement but allows for voltage drop and burying in ground.

He also said I could take 6mm from consumer unit MCB to the gate pillar cabinet and fit a small garage type consumer unit which has a 30mA RCD and a 6A light and 20A non-light MCB to supply the light and gate and sockets on seperate protected circuits so I can use a smaller circuit wire for the lights depending on fittng of lights i.e. burying cable or using transformers so cable would be low voltage and supply to transformer only.

Anyway sounds like good advice to me and now I know what to expect when I get quotes to get the job done. Which was all I was after really. I tend to find builders look at the size of my house and charge me double what they would normally. So I like to be knowledgeable on the job before I get a quote so I can estimate time and cost of parts myself.

 

[ban-all-sheds]

he recommended at least 4mm or even 6mm SWA from consumer unit to gate pillar.

Might as well go with 6mm² - the difference in cost will be marginal. Better to have 6mm² and find you only ever needed 4mm² than to have 4mm² and find you needed 6mm².

But you'll be letting your electrician supply it - it will be cheaper.

He also said I could take 6mm from consumer unit MCB

Suggest you ask people to quote on the basis of splitting the meter tails and coming off a switchfuse, rather than the house CU.

to the gate pillar cabinet

That might be worth supplying yourself - start looking on eBay for a bargain, they turn up quite frequently. Alternatively, if you've not built the gate pillars yet, incorporate a flush box like the ones used for gas/electricity meters as long as you're sure you'll never want to leave things plugged in, as you won't be able to close the door. If you get a surface mounted enclosure with a removable gland plate in the base you could have cables coming out of that and still keep the door shut. Might be useful if you have lit-up stuff at Christmas. Whatever you use, make sure it's large enough to contain a small CU, a few sockets (which might have wall-warts plugged in), and any of the gate equipment you want in there. As with the cable, too big is better than too small.

and fit a small garage type consumer unit which has a 30mA RCD and a 6A light and 20A non-light MCB to supply the light and gate and sockets on seperate protected circuits

Many of the things sold as "garage CUs" are of poor quality. Ask your electrician to supply a good quality IP rated one from a mainstream brand with a range of commercial/industrial products. Have more than 2 circuits in case you need power tools for gate maintenance, and specify DP breakers.

 

[bernardgreen]

The motors will take a lot more current when they start and will do so until they are rotating at the normal speed. ( unless they have expensive controllers that limit the current. ) The power may be 4 times the rated power while the motor is accelerating.

The duration of the high current shouldn't last more than a second or two and the cable will not be damaged. BUT the volt drop along the cable during the high current period may cause problems.

Also consider a back up battery for when there is no mains power. Releasing a gate driven by an under ground motor during a power cut can be a difficult and messy job. On a long drive the battery can be used to power the gates and be trickle charged between the gates being opened or closed. This then enables a smaller cable to be used along the drive and removes the voltage drop problems.

 

[HarveyDIY]

The motors will take a lot more current when they start and will do so until they are rotating at the normal speed. ( unless they have expensive controllers that limit the current. ) The power may be 4 times the rated power while the motor is accelerating.

The duration of the high current shouldn't last more than a second or two and the cable will not be damaged. BUT the volt drop along the cable during the high current period may cause problems.

Also consider a back up battery for when there is no mains power. Releasing a gate driven by an under ground motor during a power cut can be a difficult and messy job. On a long drive the battery can be used to power the gates and be trickle charged between the gates being opened or closed. This then enables a smaller cable to be used along the drive and removes the voltage drop problems.

I believe the figures quoted 15A@24v would be the absolute maximum draw of current and after the initial start up it is much lower than 15A.

I have considered the battery backup option for these came motors. As a worse case they come with a key that unlocks the motors but as you say battery backup would be better.