Electricity in the greenhouse

[macmac]

My friend has just had a splendid new greenhouse and would like to install electricity.She has had three electricians so far each giving allsorts of information.i.e.the cable must be buried ,the cable can be attached to the adjacent fence,the cable cannot be attached to the adjacent fence Do any of you informed people know anything about this subject and could you offer any advice

[oldherbaceous]

Dear macmac, i don't think the electrician that suggested running the cable along the fence would be able to produce a certificate at the end of the job.

I would always want to see armoured cable used, and waterproof sockets and switches, it will be money well spent.

[snooky]

And an RCD.

[Cider Boys]

Hello macmac

Frankly, no.

Your friend is a victim of an over regulated, over complicated and often misinterpreted set of rules. Many of which are not rules but a code of practice that the IEE (IET) have dreamt up to confuse everyone including electricians.

In my opinion, in essence, if this is a new electrical installation in the Greenhouse it falls under the planning rules and is notifiable under the Part P regulation, much like a new installation in a kitchen. If the friend wishes to do the work himself he should notify building control before he starts and then have it certified after. This is likely to cost more than the savings your friend would gain from doing it himself.

The other option is to employ a company that has registered with Part P; they can then install and certify that the installation meets the building regulations. They then carry the responsibility to ensure it is installed correctly.

It may be preferable to install underground to the greenhouse and in that case your friend could dig the required trench and bore the holes etc, so the contractors can just connect and test the wiring.

Barney

[peter]

Totally and unequivocally endorse OH's and Snooky's comments.

My greenhouse is at the bottom of my garden, about seventy feet from the house and when we had a rear extension built on the house I specified that I wanted power run to the greenhouse and the shed.
As we had to have a new consumer unit (fuse box with mini circuit breakers) anyway, because the old one did not have enough gaps to cope with the additional internal circuits the extra cost was under £300 all in.
An anonymous 4" square box on the outside wall next to the new-kitchen door has armoured cable coming out of it into the gap between terrace and fence, where it dives under the corner of the terrace and it's steps down into the garden, runs under the lawn, comes up to an independant consumer unit in the workshop-shed, back down below the lawn, under the concrete path and surfaces in the greenhouse onto a 2'x18" two legged "noticeboard" of 3/4" exterior ply, which bears the twin waterproof 13amp socket, standard outdoor bulkhead light ans waterproof switch for same.

Safety for the greenhouse is run from the consumer unit in the shed, which has its own internal light and twin 13amp socket as well.
The builder who did the terrace (long story, but different to the extension builder) laid a plastic pipe for the cable and cut the concrete path with his road saw. I dug all the trenching, which had to be over 50cm deep.

Plus point, when I filled in the trench I half filled it, then ran blue water pipe before filling in properly, so now I have a 12' hose I can pick up from the lawn and plug into the tap on the terrace which supplied an 8' hose in the greenhouse with nothing visible inbetween. Hoses join the blue pipe by copper 1/4" inserts and twin jubilee clips.

The shed bits had to live inside a dustbin for a while as I demolished the childrens playshed into which they had been installed and custom built a new workshop shed around the leccie-supply point. They were mounted on a bit of ply and I trimmed it so it sat snugly upright in an oldfashioned galvanised steel dustbin. Now the armoured cable is hidden in a hollow wooden wall and surrounded with rockwool insulation, nice snug shed it is.

[macmac]

Thankyou all for the information, very technical, I can just about wire a three pin plug but I will pass it on to my friend,her husband's a magician so maybe there's a solution

[malcolmchisholm]

To install mains electricity anywhere in a garden, you must use a "Part P" qualified competent person. Ask a trade association such as NAPIT (napit.org.uk) for details of competent members in your area.

Cables attached to structures must be external quality. Do not use grey flat twin and earth, which will degrade in the ultra-violet light from daylight.

Do not attach cables to fences, which can be easily damaged.

Cables under the ground must be:
. steel-wire-armoured or enclosed in a duct
. buried at least 20" / 500mm below the surface, on a layer of sand with more sand above
. marked by a marker ribbon 6" / 150mm below the surface
. terminated in a weatherproof enclosure or socket outlet rated IP54 or greater
. electrically earthed by the armoured shield as well as any protective earth conductor in the cable
. supplied by a 30mA RCD-protected power source.

Cables under a vegetable patch or where deep diggin might take place must be buried lower than you are likely to dig, with the marker tape deeper as well but still some distance above the cable.

All equipment used in greenhouses or outside must be Class II insulated.

I hope that this will be of use to members.

Malcolm Chisholm
Electrically Yours,
Southport
PR8 4SB

[Tigger]

I'm with Malcolmchisolm, Peter, OH and Snooky. We have 2 tunnels amongst our vineyard and a kitchen area in our orchard. We were subject to an unannounced inspection which passed mustard. Thank goodness.

[Cider Boys]

I question the following statement from malcolmchisolm:

To install mains electricity anywhere in a garden, you must use a "Part P" qualified competent person. Ask a trade association such as NAPIT (napit.org.uk) for details of competent members in your area.

Unless the rules have changed it is misleading to say MUST, in fact any competent person may install it.

The definition of a competent person is extremely wooly.

As my previous post advises, it may be cheaper in the long run to allow a Part P firm to carry out the work, but there is absolutely nothing to stop anyone carrying out the work and having it inspected.

Part P is under the building inspection and planning rules and these installations should be notified and inspected, but again anyone can carry out the actual work. Incidentally it is not the individual electrician that is Part P registered it is the company that employs the electrician.

Unless the rules again have changed since my experience with them, you may have many extremely well qualified and experienced single trader electrician who can't afford the registration for part P also prevented from certifying their work.

Barney

As I state in my previous post Part P is a rubbish rule that can be flouted very easily and does little to prevent unsafe installations occuring since those who carry out unsafe installations still carry out unsafe work.

[Tony Hague]

I'm a chartered member of the (then) IEE, and watched Part P come into existance. I have to agree with much of what Barney says. The arguments in favour of Part P based on electrocutions / house fires involved rather small numbers to begin with, and once you deduct those that Part P can't prevent (faulty appliances, installations which become unsafe through, eg, rodent damage, and the work that Part P still permits) - it begins to look more like a "jobs for the boys" measure. In terms of domestic safety, the introduction of part P is hugely outweighed by the invention of the oven chip. Perhaps the most reassuring thing is that tradesmen are at least required to carry adequate insurance for when they do mess up.

None the less, it is the law and we're stuck with it, so I would find a friendly electrician. Whilst you could theoretically DIY it with appropriate inspection, it probably won't save money.

[Geoff]

But has it saved a single life - I think it is job creation legislation. We'll have professional road crossers next.

[malcolmchisholm]

Barney, I stand corrected. I must apologise for my earlier post.

According to 17th Edition IEE Wiring Regulations, any "competent person" may install electrical equipment in or across a garden. Local Building Control must be notified before installation commences unless it is being carried out by "a person registered with an electrical self-certification scheme prescribed in regulations..." (quote from Approved Document P)

A "competent person" is one who "possesses sufficient technical knowledge, relevant practical skills and experience for the nature of the work undertaken and is able at all times to prevent danger and, where appropriate, injury to him/herself and others." (Quote 17th ed Wiring Regs)

So you don't have to be part P qualified to do the job but your company does have to be part P qualified and registered to sign it off and register it with a scheme.

As Tony Hague says, we're stuck with the law so we might as well get on and work within it. As a newly-qualified electrician, my first two jobs were to correct mistakes made by other professional, part P registered electricians, so it looks like part P isn't as effective as it might be. As with all registration schemes, it needs policing to ensure that members remain competent.

Happy Kitchen Gardening!

Malcolm Chisholm
Electrically Yours
Southport PR8 4SB

[Cider Boys]

Hello Malcolm

Let me congratulate you in furthering a career as an electrician. A good grounding (no pun intended) in electrical installation and maintenance allows you, if desired, to also diversify into many related occupations. I am not an electrician in the broadly accepted meaning of the word. but have worked with electricity for many years in engineering.

Unfortunately you will come across many "professional" installations that do not fulfill the relevant codes of practice, all you can do is ensure your work does. I have regularly noticed incorrect installations and incorrect inspections passed by "qualified Electricians".

In my view having foreign electricians working on our systems is a far more dangerous activity than a competent DIYer adding a socket in a kitchen.

Only last week I encountered an Australian Electrician working on a NHS site that did not know what a ring main was, many other countries run the cables directly by the shortest route etc etc. I am not advocating our system is better than those of other countries (many of which I find superior) but different. I would argue most DIYers in this country have a better knowlege of our electrical installations than those electricians from abroad do.

Perhaps Mr Prescott should have insisted that electricians from other countries had a course on our codes of practice before being let loose rather than introducing Part P.

You are not alone, Part P is misunderstood by many firms and electricians, I think a certain John Precott was instrumental in its conception.

One must bear in mind regarding electrical safety that what is considered correct practice in this country may not be regarded the same in other countries. Also what is considered good practice today will probably not be considered so in the future.

For many years now the ring main has been considered a good system, but is it? Was it not introduced because copper was in short supply and expensive? There are many ring mains functioning with a break in them, with a radial this would soon become apparent, I predict a return back to the radial method in the future.

What also dismays me is Portable Appliance Testing, another great rip off, but that's another story.

Best wishes

Barney

[Geoff]

Don't get me started on PAT. When I worked in IT and the regulations first came in the site electricians started blowing up IT kit by testing it.

[richard p]

whatever the idea behind part p regulations the effect on the ground is that if i want electricity in my shed, as engineer i am quite capable of installing it properly... but its illegal for me to do so without getting the council involved and paying to get a piece of paper... end result i run an extension lead out through the kitchen window and accross the lawn when i need it. as i see it the legislation is actually resulting in more risk rather than less.... i know i am not alone in this.

anyone with an iota of common sense will use a rcd circuit breaker on portable tools which makes pat testing irrelevent as well..