What size SWA cable for Outdoor Electric Gate and lights

[HarveyDIY]

Hi,

Currently my driveway has been dug up and building walls and pillars. Sometime in near future I plan to get electric iron gates. I have decided I will use underground CAME Frog AE24v gate motors. The control panel for this takes a 230V supply and then has its own transformer to convert this to 24v.

So I need to run some SWA cable about 30m from my garage where the main consumer unit is to the gate pillar. I am unclear on the CAME specs. It says the motor draws 15 Amps and yet it say the in the install manual the main supply to control panel should be at least 6 Amps.

Will it be good enough to run 2.5mm SWA cable 30 metres for this motor? I also plan to have some lights on the pillars and some spike lights around the lawn and hedges. Plan to use low power energy efficient bulbs so it shouldn't be more than 1000w in total. I am hoping to supply these from the same cable from the gate pillar, 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.

Does this sound right and so I can go ahead with laying 2.5mm SWA cable?

Thanks

 

[ban-all-sheds]

I am unclear on the CAME specs. It says the motor draws 15 Amps and yet it say the in the install manual the main supply to control panel should be at least 6 Amps.

That you don't know why those two current figures are different shows that you have a lack of basic electrical knowledge which is incompatible with doing electrical design work. The motors are 24V, not 230.

Coupled with the fact that this work is notifiable (it needs Building Regulations approval), it should be certified:

FOR DESIGN, CONSTRUCTION, INSPECTION & TESTING
I being the person responsible for the design, construction, inspection & testing of the electrical installation (as indicated by my signature below), particulars of which are described above, having exercised reasonable skill and care when carrying out the design, construction, inspection & testing hereby CERTIFY that the said work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2008, amended to 2011 except for the departures, if any, detailed as follows:

and that there are a number of regulations for outside and buried supplies to consider, you really need to get an electrician involved.

Have you checked what the gate installers will want to see?

 

[HarveyDIY]

I thought I would get some response like that. This is a DIY forum if I understand correctly. I understand Volts x Amps =Watts. Still I wanted to make sure 15A load is not on main supply cable, that how a DIYer learns these things by getting confirmation on forums like this.

As I said my gates will be sometime in future not now. My driveway is already dug up so I wish to lay cable for these CAME motors. Don't want to be digging up my new driveway again in future when i decide to have the gates installed.

I think 2.5mm SWA radial will suffice considering distance is 30m to gate pillar and no more than 20m lighting cable around the garden. Based on motors and lights not expecting a load of more than 20 amps. I was wandering if anyone was going to suggest I go up to 4mm.

 

[ericmark]

I would agree 15A @ 24 volt is around 1.6A @ 230V so there is a discrepancy there but even at 6A the volt drop is around 2.8 volt well within the requirement for the light with 2.5mm² cable but I would assume the garage is not where the DNO deliver the power to so likely there is also the volt drop to garage to consider.

2.5mm² at 6A is good for around 73 meters keeping within the 3% volt drop.

New circuits require the LABC to be notified but the Part P does not define a new circuit so as to if it required notification could start a long debate. However there have been some high profile court cases over electric gates and injury caused by them so I personally would want to see the installers insurance.

I have been rather surprised at domestic mechanical aids. My mother had a Stannah stair lift installed which turns through 180 degrees so from top of stairs you can't see the bottom. I has an arm which has to be extended first as it blocks the hall way once extended.

There are no safety beams or micro switches it could crush a child or pet and it blocks the only wheel chair access when extended without having a means to retract it from inside the house for wheel chair user. It's not used now so not a problem but the point is even though a well known make and installed by professionals it is clearly not safe.

Installed by professionals with insurance then if there is an error then clearly it does not prevent the physical damage but it does mean your not the guy standing up in court.

If the stair lift was used I would be hounding the council to correct their workmanship but in last year used once.

 

[bernardgreen]

For the time being and before the drive is completed install two ducts from garage to gate post. One duct for the SWA 230 volt supply cable and the other for the extra low voltage cables ( intercom. control etc etc )

Also install a duct across the driveway between the posts.

A complication is if you are going to have vehicle detection loops under the drive way. It might be worth asking the gate company what the loops will be and have them installed before the drive is surfaced. The cost of the loop is not very much ( loop wire only and not the electronics module ) should you decide later not to use the loops.

 

[ban-all-sheds]

I thought I would get some response like that. This is a DIY forum if I understand correctly.

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

But you are not doing it yourself, you are asking others to do the design work, and I really don't think that you're considering the fact that you, yourself, cannot legitimately sign the Electrical Installation Certificate, nor I fear credibly describe to your local Building Control department how you'll ensure that the work will comply with Part P.

My driveway is already dug up so I wish to lay cable for these CAME motors.

Then you need an electrician to do the design, installation, and testing of the cable so that he can sign the EIC. I would suggest using a registered one to avoid the cost of submitting a Building Regulations application.

Don't want to be digging up my new driveway again in future when i decide to have the gates installed.

That's quite understandable.

So get the gate/lighting circuit properly and legally designed, installed, tested and certified now, ready for the gate installers in the future.

 

[ericmark]

I have just read your response. BAS is well known for going OTT but still has some points.

When you lay the cable it will need terminating and testing and a certificate completed showing the results of the test to present to the gate fitters.

The rules for filling in an electrical installation certificate are quite simple only the person doing the work can sign for that work and you have to be competent to do the work.

There are to be fair certificates with provision for three signatures one for design, one for installation and one for inspection and testing so in theroy you could sign the first two then employ an electrician to do the last one. However it is Inspection and testing and he would need to see cable before the trench is back filled. As to finding some one willing that's another question.

You can clearly pay the LABC and let them become the clerk of works and ensure everything is done correct. Where the LABC is already involved for example building an extension then having them also do electrics is not bad. But the minimum charge means just for electrics it is rather expensive. It is based on first £2000 worth of work and electrics alone rarely hit that limit so you end up paying the LABC more than it costs to do the job.

Because electric gates are so in ones face to fit them without the paperwork is really asking to get caught. Garden shed you will likely get away with but gates on your entrance is very different.

 

[ban-all-sheds]

New circuits require the LABC to be notified but the Part P does not define a new circuit so as to if it required notification could start a long debate.

Well firstly Part P is not about notification, so you wouldn't expect it to define what a new circuit is.

But nobody who knew what they were doing would put buried electric motors and external control equipment onto an existing circuit supplying parts of the house, so I can't see that there could be any credible way to say that a new cable connected to a new, or previously unused, MCB was not a new circuit.

 

[ericmark]

I would follow bernardgreen's suggestion and fit ducts.

 

[HarveyDIY]

A good idea to install service ducts and then route the SWA later on.

I am all aware of gate safety but that is not my question. In fact that is why I am going for the CAME AE low voltage motors as it has built in encoders for detecting forces on the gate. I have even designed my walls and pillars so noone can get crushed between the gate and wall as they are far apart. Any shear points the gate fitter I'm sure will put on safety strips.

Just to note my main meter and consumer unit are both in the garage next to each other. This is a 1930s house. Only thing is RCD. Should we just rely on RCD of consumer unit or install a smaller 30mA RCD unit and connect the SWA into this and then into my consumer unit?

 

[ericmark]

I did say it could start a long debate. I don't think it is helpful at this point to debate what is a new circuit.

 

[ban-all-sheds]

I have just read your response. BAS is well known for going OTT but still has some points.

Nothing I have said is OTT. IMO Harvey does not have the competence necessary to design electrical installations.

 

[ericmark]

I see no reason why any RCD needs fitting unless it is a TT supply. However personally I would protect to 30mA and if main incoming is 100mA then I would personally fit a 30mA. With just 6A I would simply use a RCD FCU in a metal box so I can fit the SWA gland into that box.

 

[ericmark]

That you don't know why those two current figures are different shows that you have a lack of basic electrical knowledge which is incompatible with doing electrical design work. The motors are 24V, not 230.

That is completely unnecessary the 1.6A which the motors will draw at 230v is very different to the 6A the instructions give as minimum and to ask the question why is not showing any lack of knowledge which could mean they can't do the work in fact to realise there is a difference between the two quoted figures actually shows they have at least an understanding of the simple maths involved with electrics.

I would guess it is inrush to transformer and start amps but could well be a switched mode supply which would not have the inrush so I can only guess at the difference.

The approach should be "Welcome to the forum" not go and get an electrician and where you do have to point it out it should be in a polite manor not loads of red writing.

 

[ban-all-sheds]

BTW - had a very quick look at the instructions for those motors - they are 6 years out of date, electrically.

I wonder what else they have failed to keep up to date with in that time?

Harvey - before making any decisions about the gates to use, or which mean you would have to use them, I strongly suggest finding an installer with the right skills and the right insurance who says he is happy to install those gates.