Son Lamps

[Jack]

My friend says he has put ordinary incandescant lamps in son fittngs, but I am not sure how safe that would be, are there any electricians out there, that can tell me the consequences of doing this?

[Andrew Gabriel]

Not a good idea. I expect the incandescant lamp glows dimly, and very in efficiently. If it's a high power incandescent, it might overheat the SON control gear, although that's unlikely.

If the SON control gear includes an external igniter, then there are a number of additional risks. It might manage to strike an arc in the incandescant lamp after the filament has broken, which would be unsafe as the lamp wasn't designed for this and may fail explosively or start a fire. Secondly, the bulb (outer glass) of an incandescent lamp is not an insulator, and you might be able to receive an electric shock from the igniter through it - these kick out many kilovolts.

What wattage SON is the fitting meant to take, does it use an internal or external igniter, and what wattage incandescant lamp is fitted?

[Jack]

The fittings originally had 70w son-e lamps, which i think had internal ignitors. As these are being used to light to menage at the stables where my horses are kept, I am a little worried about the safety aspect.

[Andrew Gabriel]

Well, there's always a risk associated with using wrong parts and unforeseen events which arise as a result, although in this case I can't think of any (that's the _unforeseen_ bit). It's daft in any case, because the lights are presumably so much dimmer now.

However, I would be concerned about someone who bodges electrical installations around livestock. Livestock are much more vulnerable than humans to electrocution and good electrical installation and earthing practice is essential in livestock situations. Earth leakages which you can't even feel can electrocute livestock.

[John Whitworth]

How is that so? I would have thought a horse would be a bit more thick skinned (and hence better insulated) than a human? Or are we talking chewing cables and stuff here?

[ARWadsworth]

Well four legs spread over a large earthed area instead of a humans 2 legs in a small area makes a difference.

If the OP is really telling the truth and his friend has used incandescent lamps instead of SONs then there is only one solution.

Install the correct lamps.

Adam

[Andrew Gabriel]

Livestock are more sensitive to electric shock than humans.

And the horse doesn't have the option to let go of the ground.

The classic case here is where you find a field of dead cows, and no apparent cause, and they were all fine before this happened. Investigation shows a faulty insulator on an overhead electricity pole. The leakage down to ground and the potential across the surface of the field, impercetable to you (even if you were to walk in bare feed on wet ground), will electrocute the livestock given appropriate ground resistance.

There are similar cases in stables where earth leakage sets up a potential across the floor of the stables, resulting in death of a horse. I have mentioned this on uk.d-i-y a few times when people are embarking on DIY in stables/cattle sheds. On one occasion someone followed up saying they were involved in a legal case against an electrician (IIRC) where a horse died in exactly this way.

[Andy Champ]

Apart from the shock risk (which is real as others have described it) horses can't open the door to let themselves out if the stable catches fire.

Andy

[fred]

In article , ARWadsworth writes

Just a thought, is it possible the owner has bypassed the SON control gear and is just using the fittings to house GLS lamps?