shed wiring for snakes, but another question

[17thman]

Hi.

I know this is a DIY forum but the more experienced sparks than me may be able to help.

I have been asked to quote, on monday morning, for a supply to a shed/building at the rear of a garden. This is all fine and usual and dandy.

The question I have, because i like to be aware of all circumstances, and it might be something i would like to put to the client.

If the supply circuit is not rcd protected and i install a small cu with rcd additional protection for lighting and sockets and there is a power failure or a power failure within the shed/building because a fault to earth or short between Land N, I would personally want an indication at the household end.

My first thought is to have a non maintained emergency light in the shed/building and with using 5 core swa, i could use the 2 spare cores to link back from the emergency light to a light or sounder of some sort in the dwelling.

I pressume that an emergency light in the shed/building, supplying the household indication would require a dc light/sounder at the household end.

Any suggestions or equipment recommendations would be welcome

 

[holmslaw]

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[OwainDIYer]

if the person is away from home a lot then wiring loss of heat stats to an autodialler (cabled or GSM depending) to call a mobile phone might be better than relying totally on an in-house alarm.

If using GSM check the SIM doesn't expire after a period of non-use.

another option is that many IP CCTV cameras have an alarm input, these could be cabled or wifi, and email video alerts, and would allow the owner to check on the snakes remotely (from a smartphone if desired)

 

[JohnW2]

My first thought is to have a non maintained emergency light in the shed/building and with using 5 core swa, i could use the 2 spare cores to link back from the emergency light to a light or sounder of some sort in the dwelling.

If you did that, you'd really only be using the emergency light as a 'power failure relay'. If you had two spare cores, could you not simply use them to take the post-rcd circuit back to the house, and have a relay operating an alarm there?

However, as others have said, I would have thought the real concern would be about loss of adequate heating, whether due to RCD tripping or anything else (e.g. heating system failure) - so an alarm based on heat sensing might actually be what's needed. That could be wirelessly connected to house or might possibly be able to use spare cores in the supply cable.

Kind Regards, John.

 

[17thman]

yes guys, thanks

I think that running 5 core will give various options. John, I meant that the 2 spare cores could be used to run the dc of the load side of the emergency light to another dc device or the spare cores attached to the supply side of the shed emergency light to be linked to another emegency light/battery charged sounder of some sort in the house.

all your replies make me understand that there is a more cultivated an technological upto date way to do it. I will do some research, and once again thank you all.



If any body has any more suggestions i would be grateful.

 

[flyingsparks]

John, I meant that the 2 spare cores could be used to run the dc of the load side of the emergency light....

I'm not sure but I expect using one 5 core cable and running a 240V AC supply and a (i guess) 12V DC supply all within would be contravention of the regs, plus you would possibly get funny harmonic effects. I'd use the 2 cores as a relay driver on a 240V AC circuit.

 

[JohnW2]

I think that running 5 core will give various options. John, I meant that the 2 spare cores could be used to run the dc of the load side of the emergency light to another dc device or the spare cores attached to the supply side of the shed emergency light to be linked to another emegency light/battery charged sounder of some sort in the house.

Yes, I realised that and, I suppsoe, it is quite a clever idea. However, as I said, if you didn't actually want/need an emergency light in the shed (you might - in which case it would be an obvious way to do it), you'd effectively be using the emergency light as a power failure dectector (with a DC 'output'), which could be done in other ways, at the house, if you fed back the post-RCD circuit to the house via spare cores.

Kind Regards, John.

 

[EFLImpudence]

If you had two spare cores, could you not simply use them to take the post-rcd circuit back to the house, and have a relay operating an alarm there?

Do you need a (second) Neutral coming back to the house?

 

[JohnW2]

If you had two spare cores, could you not simply use them to take the post-rcd circuit back to the house, and have a relay operating an alarm there?

Do you need a (second) Neutral coming back to the house?

I almost made that mistake myself (indeed, I did, and then edited it out!).

As I came to realise, I think you do - if you just brought back the post-RCD L, and connected it via a relay to the (pre-shed-RCD) neutral in the house, you'd trip the shed RCD!

Kind Regards, John.

 

[EFLImpudence]

Ah. Silly me - wasn't thinking about the RCD.

 

[Alarm]

Cooer/Menvier SD3 Dialler will give temp control and call predetermined house or mobile numbers in addition to any electrical works you do.

http://www.securitywarehouse.co.uk/catalog/menvier-sd3-speech-dialler-p-736.html
Not my favourite supplier but showing the cheapest in a quick search.
The equipment is very reliable hence the costs.

 

[17thman]

thanks guys.

If the dc ouput from the emergency lamp in the shed was used to power another dc source in the house in the event of a power failure, would that contravience the regs since both circuits could not possibly be energised att he same time. I will shut up if that is wrong and go and do some more reading, but keep them coming, the budget might not stretch to some amazing equipment but for warned is for-armed and it is interesting to see the responses, but the relay option seems another way to go

Thanks

 

[JohnW2]

Ah. Silly me - wasn't thinking about the RCD.

Join the club - as I said, I initially made the same mistake, but realised just in time!

Of course, there are ways in which one could do it with just one spare core - functionally satisfactory, but some might regard as more iffy. For example, if one had a relay at the shed, with its coil connected to the post-RCD supply, one could use the relay contacts to switch the pre-RCD L and return that down one spare core - to activate warning lights/bizzers/whatever in the house (referenced to the neutral at the house).

Kind Regards, John.

 

[JohnW2]

If the dc ouput from the emergency lamp in the shed was used to power another dc source in the house in the event of a power failure, would that contravience the regs since both circuits could not possibly be energised att he same time.

I'm not sure what you mean. If you used the dc simply to power warning lights/buzzers etc., then I see no problem. Getting at a dc ouput (active only during power failure) from the emergency light might, however, not be totally straightforward.

... but the relay option seems another way to go

It's really not that much different - with your idea, you're simply using the relay (or equivalent) in an emergency lighting fitting to do the job.

Kind Regards, John.

 

[holmslaw]

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