Bath fan installation, fused connection

[faceman80]

Dear All
I hope somebody can assist me, I have scoured the rest of this forum for an answer but not had any luck, so please forgive repetition! I have recently installed a combination extract light/fan over my shower in the bathroom. The unit consists of a fan and integrated light, and the light runs through a transformer. I have wired both up via a junction box with the appropriate switched live to a separate pull cord switch. I have taken the supply for it all from the lighting circuit, and fed this first into a 3Amp fused connection unit, as per the instructions that came with it. Because I have wired the FCU (think this is the correct abbreviation) from the lighting circuit, not at the light switch with a permanent live, the fan only operates when the bathroom lights are on. This in itself poses me no problem as i hate the noisy overrun!. However, my concern is that the FCU is wired off the lighting circuit and thus has no earth. (the original lighting circuit is not earthed) Incidentally the upstairs lighting circuit has a separate fuse on the fuseboard. Is the fact the the new FCU I have connected is not earthed a problem? Should I disconnect it from the lighting circuit and spur it from the first floor sockets ring instead so it has an earth? Or can I leave it as is? Any help most appreciated, fuse is out and not in use for now! Cheers

 

[Steve]

Yuck. Several issues here.

Have you notified LABC? Its the law (long document but you'll be glad you read it, you're obviously oblivious to its existence).

When was the last time your installation was inspected?

Lighting circuit with no earth indicates that AT LEAST your lighting circuit needs rewiring. If you have any metal light fittings or switches on this circuit, you must remove them, or isolate the circuit until you can.

Please contact a local electrician to do a periodic.

Just because it works, doesn't mean its ok.

 

[electronicsuk]

Assuming no earth is required by the fan or light (and this is often the case), and you're not using a metal backbox, the lack of an earth connection is not of major concern for this part of the installation. However, I would suggest in any case that you purchase an FCU which includes screw caps (or use nylon screws), as there are still exposed conductive parts on the rear of most electrical accessories that could potentially become live should the line conductor somehow become loose.

EDIT: As Steve says above, the same applies to any other fittings on the unearthed lighting circuit - there should be no metal lights/switches, and where necessary, you should use nylon screws or plastic screwcaps.

 

[faceman80]

Okay, I have just been and checked the lighting circuit (have unscrewed the housing from the bathroom pull switch), and note that it does have an earth cable running to it, so it would seem that the lighting circuit is earthed. The fittings themselves are bathroom IP rated downlighters, and each individual downlighter has only a neutral and a live, but runs back to the switch, which has an earth. Further thoughts? Not had installation checked, not long had the house.

 

[Steve]

In that case could you put up a photo of the mains area of your electrical installation, we can give you vague information as well as whether it would be advisable to have a periodic done (since you mention "fuses" it indicates an aged installation)

You should replace any cabling to your lights and FCU which isn't earthed, order to provide an earth for these items.

 

[electronicsuk]

Okay, I have just been and checked the lighting circuit (have unscrewed the housing from the bathroom pull switch), and note that it does have an earth cable running to it, so it would seem that the lighting circuit is earthed. The fittings themselves are bathroom IP rated downlighters, and each individual downlighter has only a neutral and a live, but runs back to the switch, which has an earth. Further thoughts? Not had installation checked, not long had the house.

If there is a CPC as an integral part of the cable then it's likely the circuit has an earth connection, but without the appropriate test equipment you are going to find it difficult to be sure that it's actually providing an adequate earth connection. As a minimum you could use something like a Steinel multi check between L-E that will at least put on a little load, it would be better than nothing but still not recommended - it could cause earthed parts to become live during testing if there is no connection back to the MET, it may cause RCDs to trip if the circuit is fed from one, and it will give no indication as to earth loop impedance.

The correct thing to do would be to take your switched supply from the light switch and continue the earth from there, but it doesn't negate the need for testing.

Also, whoever wired the bathroom lights should have used a cable with a CPC/earth, as there is a requirement to continue the CPC on the circuit (where present) to all fittings, regardless of whether or not it is actually required.

 

[faceman80]

Okay, so the suggested solution is to run a cable from the bathroom pullcord lightswitch,(not the actual downlighter circuit as it is presently) thus providing both a permanent live, and an earth from the switch to the FCU?

This would be fine, but tricky to do, due to the locations of the cabling and the way they run.

Matthew, Out of interest, I have just checked the instructions on the fan and there is no mention of any requirement to provide an earth to either connection . I haven't used a metal back box, a plastic one. Surely if the fan and light dont need an earth is it really necessary to run a cable from the original switch? The lack of a permanent live to my mind is only inconvenient for the fan over run. Can I not do as you suggest and ensure the FCU has nylon screws incase of the unlikely event that the live conductor comes loose?
thanks for help so far, good forum this.[/u]

 

[electronicsuk]

Okay, so the suggested solution is to run a cable from the bathroom pullcord lightswitch,(not the actual downlighter circuit as it is presently) thus providing both a permanent live, and an earth from the switch to the FCU?

Yup, assuming neutral is present at the switch. If not, there must be a junction box somewhere between the switch and the downlights where you can take a supply from.

Matthew, Out of interest, I have just checked the instructions on the fan and there is no mention of any requirement to provide an earth to either connection .

I don't have the number to hand, but there is certainly a regulation that requires a continuous CPC to be run to electrical fittings regardless of whether or not they actually require an earth. This ensures that should they be changed to a class I earthed device in the future, the necessary connections will be there.

I haven't used a metal back box, a plastic one. Surely if the fan and light dont need an earth is it really necessary to run a cable from the original switch? The lack of a permanent live to my mind is only inconvenient for the fan over run. Can I not do as you suggest and ensure the FCU has nylon screws incase of the unlikely event that the live conductor comes loose?
thanks for help so far, good forum this.[/u]

The answer to that depends on which hat I've got on. It's a requirement of BS7671 17th ed. wiring regs, and although they are not a statutory document, you have little choice but to follow them - it would otherwise be difficult to stand up in court and claim a safe installation. If you were asking me with my commonsense hat on then no, with nylon screws, plastic fittings and class II electrical equipment that does not require an earth connection, the lack of a CPC does not present a major hazard. However, you just can't guarantee how the installation will be modified in the future.