tv amplifier wiring


Postby Carnegie » Tue Aug 17, 2010 7:17 pm

I have had a 5amp tv amplifier installed in the loft which operates off the mains. There is no plug socket in the loft and the installer says he will create one by wiring into the lighting system with 1.5mm wiring (via a junction box) and attaching a standard plug socket.
Is this safe only I thought that plug sockets had to be wired into the ring socket circuit. He said he would mark the socket 'only for use with tv amplifier'
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Postby sparx » Tue Aug 17, 2010 11:04 pm

Bad news,
the problem is that just marking the outlet for limited use does not prevent someone later using the socket for other uses.
Since the size of fuse fitted in the plug maybe 5A it/gives little extra protection for the amp than the lighting circuits 6A mcb.
It would be better to have a 3A or 5A plug and socket or maybe a klix type plug in rose fitted which can't be abused later
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Postby ericmark » Wed Aug 18, 2010 3:09 am

MK do make the BS 546 3 pin 5A and 2A sockets K771 WHI and K770 WHI which at first glance seem to fit the bill. The pair will cost about £5.35 plus backing box so around the £6 mark but there is no fuse in the plug or socket.
If the amplifier is double insulated the MK K700 shaver socket would seem best option as these include a fuse these were however expensive for what they were at around £20 and with a isolation type shaver socket costing £7.50 but have a maximum output of 20va but since my 6 way amplifier states less than 5W that will likely be OK as long as the amplifier does not need an earth.
The clock socket MK 995 and MK 997 the latter surface so likely the best option are fitted with 2A fuse but at £12 cost more than shaver socket. And with a standard switched spur MK K1040 costing £5.75 one wonders if the idea of being unplug-able is really needed?
The Klik lighting 6 Amp plug-in ceiling roses at £3.50 are three pin so allows connection of earth but means no fuse other than lighting fuse and if your going to fit a fused connection unit as well then why bother with plug and socket?
My SLX 8B aerial amplifier states no more than 3A fuse must be used and although portable appliances are not suppose to rely on the fuse in the plug and the fuse in the plug is suppose to only protect the cable we are also to follow manufactures instructions.
I found the MK 993WHI CLOCK CONNECTOR at £8 on ebay although not sure if it needs a round backing box? (conduit box) and I think if I was fitting amplifiers in a loft then that would likely be what I would use.
With my house having emergency lights fitted so even if fuse/MCB does open I am not plunged into darkness I would have no objections to using a 5A round pin socket but in my house I have 13A sockets in loft anyway so not really a problem.
One way would be to use an extension lead socket socket with a fuse in the socket but not really a professional way around the problem. As to idea some one could replace the fuse with a bigger one that is true for anything using a BS 1362 fuse. The clock connector has a smaller sized fuse so one can't fit a bigger one. But of course you can fit a nail so to my mind nothing wrong with a BS 1362 fuse of 1A to 3A ratting.
I would never fit an unfused 13A socket to lights as all too easy for some one to trip lights using a drill ect in loft.
There is the Grid system that allows you to have fuses and sockets and switches all in same outlet box but so expensive I have not bothered to look up part numbers.
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Postby Carnegie » Wed Aug 18, 2010 7:00 am

Thanks Sparx but may I just clarify a couple of points - the installer is coming back tomorrow to finish job & I don't want him to blind me with science!
What do you mean by a 3 or 5amp plug & socket - are they the same to look at, etc as the standard 13amp socket? Can you elaborate on what is klix type rose socket - I suspect he won't be keen on cutting off existing amplifier plug if thats whats required.
Many thanks.
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Postby Carnegie » Wed Aug 18, 2010 7:15 am

Sorry sparx - forgot to ask the bit about wiring into the lighting circuit for the socket - is this right?
Thanks
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Postby ericmark » Wed Aug 18, 2010 10:34 am

If you google "Klik lighting 6 Amp plug-in ceiling roses" you will find them that's why I was careful to give right names and part numbers. Order code AS PCR2000 with TLC.

Same with three pin plugs google "K770 WHI" and the tlc-direct.co.uk advert will come up and show you what they are. We are not allowed web links on here hence MK part numbers.
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Postby sparx » Wed Aug 18, 2010 6:29 pm

What ERIC said!
I concur.
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Postby Carnegie » Thu Aug 19, 2010 12:19 pm

Thank you ericmark & sparx for your help. However, the installation man turned up this morning and, based on your comments, I politely queried attaching a 13amp socket to the lighting circuit. The result was that he went into the loft and said he found a 'radial circuit' (?) supplying the immersion heater which is operated via a double socket & plug (special socket he said) in the airing cupboard. He then spurred off the radial circuit cable (2.5mm he said) and created a single 13 amp socket for the amplifier plug to go into. He also said if I took the amplifier plug out I could use a drill, etc, in the loft. He also said the amplifier was only 3 amp (not 5 as I thought) and had a 3 amp fuse in its plug. I noticed that when he did the work he removed a 20amp fuse (yellow) from the main fuseboard & I assume this fed the radial circuit.
He said everything would be okay and, sure enough, everything is working in the house.
Hopefully, he's got this right - it seems better to me than linking in to the lighting - any comments?
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Postby sparx » Thu Aug 19, 2010 6:41 pm

Hi although the regs imply that a fixed heating load such as an immersion heater should not supply any other load it is quite common to find CH boilers fed from this circuit.
The amp will in fact draw around 50Watts which equates to around 0.2A so it will hardly be noticed.
With a 20A protective device and the immersion drawing around 12A not much chance of overloadeven if a drill etc were to be used occasionally.
IMHO much better than having fixed appliances on lighting circuit.
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Postby Carnegie » Fri Aug 20, 2010 7:15 am

Thanks Sparx for your valued help & advice which eventually achieved a satisfactory and safe conclusion. Looking at your record, you have halped many others, such as myself, and I'm sure its all very much appreciated. Thank you.
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Postby Carnegie » Mon Aug 23, 2010 7:56 am

Hi Sparx - just one more thing (sorry to be a pain but just moved into this house so still finding my way around)
As explained, the amplifier installer has spurred into the 2.5 cable which runs from the consumer unit (with yellow 20amp fuse) and ends in a double socket fixed in the airing cupboard. Having looked in more detail I can see this is a double switched Contactum double pole RCD socket (label on front) into which the plug for the immersion heater and the plug for a pump are inserted. Does this make any difference or is there still sufficient amperage (?)not to risk overloading the cable.
Many thanks
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Postby sparx » Tue Aug 24, 2010 6:39 pm

Hi again ,
sorry for delay in answering but been a busy boy!!
It is not recommended to supply a fixed heater such as an immersion via a 13A plug and socket, as it will be running at its max current rating for long periods.
It seems as if someone wanted an RCD supply for the pump and changed the fused spur/isolator sw. for the immersion into a double RCD socket.
BTW the YELLOW fuse is as you say a 20A device so total circuit should not be overloaded,
what you have now is a circuit which should work but is in breach of regs. not a problem unless you ever need a Periodic Inspection Report before selling/renting out the property.
No immediate danger, just not compliant.
regards Sparx
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Postby Carnegie » Tue Aug 24, 2010 9:36 pm

Many thanks - I'll leave it as it is as we won't be moving in next 20 years - finally, over & out!!
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