Armoured Cable

Guys,

Completely non bike related but wondered if there are are sparkys on here who might know.

I need to run 64 AMPS to my pool heater. What size (10mm, 16mm, 25mm etc) and what type (single core, multi core etc) armoured cable should I use to facilitate this electrical load?

No worries if no one knows but thought I would try on here..

Any advise gratefully received or ignored

Cheers
Neil

 

Neil, Gazza1 is your man. He fitted some armoured wiring for me last year.

 

I just attended a Building regs update seminar this morning. Most of it was real forehead on keyboard stuff, delivered with ponderous deliberation and cod jokes. If I got this right, the work you are doing will involve putting in a new circuit and the changes which have just taken effect to part P require you to get it signed off by an appropriately-qualified sparky. And it is quite possible that he will charge the same to check, test and sign off and produce the required paperwork for Building Control ( I think this is a 'notifiable' bit of work). Not good news, I fear, but it sounds as if Gazza can tell you the real story!

 

As PM says, almost any installation now has to be signed off with a domestic p cert. Pretty much anything that used to fall under DIY is now subject to inspection (usually about £250 for the pleasure).

You can cut out a chunk of the cost of the sparky by digging the channel for the cable (assuming it's going underground and not above) yourself and laying the cable, for him to terminate and hook up.
The gauge cable you'll need will be based on the length of the run and the total amperage required. The calculation is pretty simple once you know your current draw.
You'll need 3 core if you're terminating the ground at the CU or 2 core with a separate ground line if you want to stake at the CCU.

Given the cost of the p cert sign off, like the big PM says you may well be better off getting quotes for the work + cert. first.

 

What is the length of cable run? You need to know that to calculate the voltage drop.

The Domestic P cert is just a load of new crap that has been brought out, as long as you feel you are competent to do it yourself then do so.

 

Is that heater single phase?

 

Cheers for the replies guys..

Just to clarify a couple of point..

The cable length needs to be 46ft and be able to hold 60+ amps.

I will be laying the cable myself to try to keep the cost down but will definitely need a sparky to terminate either end. I already have a 32 amp cable fitted but the heater is not powerful enough so I need to swap my eleckro evo 6kw heater for an eleckro evo 12kw heater so need new cable laid but i am trying to identify the correct cable to lay and also where to buy it from.

Cheers

 

Also you may have to look at changing the the fuse, HRC, trip, what ever they are called now to a 64 A trip, it is almost certain that the max you have will be 32 A trip, standard cooker.

 

For a 20m (65') run with a load of 65amp, accounting for a 5% drop you'll need 10mm² cores. That's pretty monstrous cable, are you sure you need 65amps?

Calculator can be found here:
http://www.doncastercables.com/technical/cable_calculator/

 

well at 12kw the heater is drawing 50 amps, thats not including any drops, or other loads on that wire so sounds about right.

 

tsk tsk tsk ........lets all stop stabbing in the dark please
BS7671 states ( table 4D4A 17th edition IEE wiring regulations )
multicore 70 degrees c thermoplastic insulated armoured cables
1 three or four core cable of 10mm csa per core is capable of handling a draw of 50amps......( skortchio go sit on the naughty step )
1 three or four core cable of 16mm csa per core is cpapble of handling a draw of 64amps
if your saying at full chat the load is 65amps then a 3 core 25mm steel wored armoured cable direct in the ground or in a ducting ( capable of handling a draw of 82amps ) will more than adequatly cover your needs including any volt drop caluclation for the length of run. oh and that will require backing up with an 80a mcb/rcd combination with the rcd having a trip time of no more than 40mS and rated at 30mA
Contrary to popular belief although you are running a 3 core cable to include an earth you still MUST earth the steel wire armour by means of the gland tab ring at both ends.
However it is common for domestic installations to be rated at 60a at the incoming service head so you will need to investigate / enquire as to what your incoming supply is as you may well blow the service fuse which by law requires your local electrical authority to come and change as it is a sealed unit and you risk prosecution for breaking the seal.

you should be able to buy the cable from Batt cables at Erith ( not sure if they deal to the public but i dont see why not) if not then your nearest would be edmundsons at ruxley sidcup but they may have to order it in.

Yes i am a fully qualified time served 17th edition electrician with 36 years experience in the trade
no im afraid i dont do private work or certify other peoples work ( sorry ....i get little enough time for family as it is and even less to actually get out on my bike )

hope this helps Neil .

Guys
i know we try to help each other as best we can and itsall very comendable but if we are talking about potentially dangerous things that proffesionals study years to qualify to work with like electrics and plumbing etc etc even building work then lets not put forward our best guess or something we found on the internet,things can and do kill if carried out incorrectly, how often do you read of people being gassed or people getting electric shocks, how often do we see houses being condemned on tv from cowboy builders. some of the suggestions on here could have cost Neil a lot of money only to find out the cable was wrong and his whole house loses electrical supply which he then foots the cost of the authoritys coming to replace the main fuse and thats if they will replace it when they spot the under rated cable to his pool heater. and thats assuming the cable didnt catch fire or melt leading to neil having no house or recieving a potentially lethal electric shock from exposed cores.


oh and just as a quick edit the volt drop for your run of cable using 25mm armoured would be approx 1.36v which is well within the 4% permissable value stated by the IEE regs


oh and another quick edit
there is a factor that can be calculated in for cables underground whereby they normally run cooler and therefore the volt drop isnt as great but tbh you have enough scope in a 25mm cable to not worry about it and frnakly the ground temp in this country fluctuates so much over the seasons that its hard to pin point a definate figure.

 

He's right you know. I'm not sure I would mess with 65A, I have enough trouble with 13A!

Aahhhh, BS7671. I'm not an electrician, but this standard plays a big part in my working life.
Members of my team are tasked with carrying out inspections to this on railway infrastructure.
Thousands of them each year. Luckily they are 5 yearly, otherwise we'd need a lot more men!!

 

lol Jim as you know i worked for a network rail contractor a few years back and i can certainly confirm they take it all very very seriously and i imagine even at 5 yearly intervals some of the areas with the bigger stations the periodic inspections take a lot of time to carry out to bs7671 and bs 2391 standards and that it comes around all too quickly each time add to that the portable appliance tests for every asset within the infrastructure and i imagine its a full time occupation

 

As a side note you could use a 2 core cable and drop a size to 16mm but this would require a seperate earth to be run. anything below 16mm the steel wire armour can be used as the earth path but 16 and above requires a dedicated earth cable so a bit of a false economy really

 

Blimey Pete...Thx

A lot for me to digest there.

Thx

 

having read back my post above i feel i owe skortchio an apology and my reply was harsh .......he was being misled by a cable suppliers calculator ( what a pile of shite that appears to be) and one would expect that to be accurate so for that ill allow him off the naughty step but he can go and sit in the corner and think about trusting the internet in future

 

Bit of lateral thinking here, and probably b*ll*cks!

How about installing a second 6kW heater and running another length of the existing capacity cable off a separate supply?
You are not only assured all is in spec, but you build in redundancy too.

Probably still need to get it certified though, as maybe I should be!

 

Nice idea but I don't think it'll work at the pool end as there is only 1 inlet and 1 outlet on the pool although will take a closer look...

 

just get a long extension lead like everyone else