Aerial Power Supply from Lighting

[bernardgreen]

Yes, but he doesn't actually state the 'in his opinion' bit.

Hence I put it in brackets,

It seems he also wrote this somewhere

You are right to be paranoid. Two tings wrong, no point in a FCU on the lighting circuit. A 3 amp fuse has no discrimination against a 6 amp MCB. More important a 13 amp socket on the lighting circuit is bad practice. You may not plug in a heavy load, someone else might, trip the lights and put a foot through the ceiling or worse. You are in a new build. Don’t let your first job be a bodge. Bring a feed up from the ring behind a bedroom cupboard.

In my opinion to have a cable from a ring main ( 32 Amp ) run up the wall in the back of a cupboard is not acceptable unless that cable is properly installed in a chase in the newly plastered wall with accessories to create a safe zone for the new cable.

 

[winston1]

Hence I put it in brackets,

It seems he also wrote this somewhere



In my opinion to have a cable from a ring main ( 32 Amp ) run up the wall in the back of a cupboard is not acceptable unless that cable is properly installed in a chase in the newly plastered wall with accessories to create a safe zone for the new cable.

Many houses, sheds, garages, and other buildings have surface mounted cables. In your opinion are all these unacceptable.

 

[bernardgreen]

In your opinion are all these unacceptable.

Some of them are dangerous ( cable at risk of mechanical damage ) and hence not acceptable.

 

[Harry Bloomfield]

No need for the fused spur, it serves no purpose - the fuse in the plug is all that is needed, either 3amp or 1amp would be better, if you can find one. As a reminder to yourself and anyone else who might go up there, affix a clear label near the socket, explaining that only the amp should be plugged into it.

 

[bernardgreen]

the fuse in the plug is all that is needed,

regrettably not all plug top power modules have adequate fusing to prevent them melting down when the unit goes faulty.

 

[cgkstevenson]

If the TV aerial is in the (not normally accessible) loft, I see no problem in taking power from the lighting circuit but leaving the amplifier and PSU in that part of the loft suitably detachable and protected, output from the amplifier will go to a standard aerial socket set in the wall surely ?
Having a standard 13A socket to plug that cheap chinese PSU in is asking for someone else to plug something else into it.
Potentially that PSU is a fire hazard so I would box it away, but anyway look for something a bit less cheap and cheerful.

 

[Sureitsoff?]

But what if someone decided they want a hook in the back of the cupboard that the cable is behind and drills through a wooden panel straight into a cable that rightly they would not expect to be there?

 

[winston1]

Having a standard 13A socket to plug that cheap chinese PSU in is asking for someone else to plug something else into it.

How do you know if it was cheap?

Potentially that PSU is a fire hazard so I would box it away, but anyway look for something a bit less cheap and cheerful.

Why do you think it is a fire hazard? There are many thousands of similar power supplies (I have around a dozen) in use and I have never heard of one catching fire. If overloaded they shut down. Most problem with them if failing capacitors which results in low or zero output.

 

[bernardgreen]

Most problem with them if failing capacitors which results in low or zero output.

Capacitors can also fail and go short circuit, (*) If the capacitor in series with the mains input in an SMPS goes short circuit then there is no effective current limiting, Until something else fails and goes open circuit a lot of heat will be generated inside the case of the SMPS

(*) Self healing capacitors are very unlikely to fail as a short circuit. They heal by melting the electrodes where the dielectric material has failed thus isolating the fault., Problem :- self healing capacitors are expensive and many cost cutting sub contract manufacturers will not use them even if the design calls for them.

 

[Mottie]

I have my aerial booster permanently wired into the upstairs lighting circuit in my loft. It’s worked well for 30 years.

 

[winston1]

Capacitors can also fail and go short circuit, (*) If the capacitor in series with the mains input in an SMPS goes short circuit then there is no effective current limiting, Until something else fails and goes open circuit a lot of heat will be generated inside the case of the SMPS

(*) Self healing capacitors are very unlikely to fail as a short circuit. They heal by melting the electrodes where the dielectric material has failed thus isolating the fault., Problem :- self healing capacitors are expensive and many cost cutting sub contract manufacturers will not use them even if the design calls for them.

In such a case the internal fuse ruptures. Often this is a specially thinned PCB track. Can also be a small glass fuse or fusible resistor.

 

[bernardgreen]

In such a case the internal fuse ruptures.

Winston STOP making assumptions about matters about which you clearly have inadequate knowledge.

Suppose there is no internal fuse, or suppose a fuse ( or fusible resistor ) is encased in inflammable plastic moulding material which ignites before the fuse ruptures, suppose when the fuse wire ruptures there is enough carbonised ( conductive ) material to allow current to continue to flow,

There is no need to suppose these hazards exist, They do exist... Many examples have been found when items have been examined post fire incident and also when suspect items have been bought, examined and found to be so dangerous the entire stock has been impounded and destroyed.

 

[winston1]

How about some examples. As I said there thousands of these power supplies in use with no such problems. Ones supplied by UK companies for UK equipment surely will be OK. Sure you can buy rubbish on line but that applies to anything.

 

[bernardgreen]

A recent one in the pubic domain

https://washford.a.bigcontent.io/v1/static/Halfords-Mains-and-12v-leisure-inflator-290251-In-Store-and-online-Recall-Notice

 

[winston1]

Be interesting if they said what the problem is. Could be someone like you panicking over nothing.