Daisy Chaining Flourescent Lighting

[Harry Bloomfield]

Over my career so far I bet the number of faults I’ve tracked back to junction boxes must run to over 100.

Granted they are almost always due to poor installation, but then again you don’t get many junctions / faults on a good installation.

I once came across almost that many, following up on some not working equipment (one single item) supposedly installed by a qualified and competent person. Apparently in the rush to qualify, no one had taught them to connect, then give the wires a tug, to ensure they were properly secure.

It is very easy for the inexperienced to make a poor connection.

 

[Notch7]

Interesting. How do you think that figure compares with the number of faults you have tracked back to problems at screwed terminals which were not in JBs (e.g. in sockets, switches, roses, light fittings, appliances, CUs etc. etc.)?

Kind Regards, John

Ive never understood why screw terminals are designed they way they are.

JBs generally have a round hole for the wire and a screw. With say 2 wires, the screw may bite on just one, or it may bite mostly one one and the other may just get trapped. Diyers may get over it by twisting wires together, something pros avoid -esp these days of testing.

MCBs have a space that the wires go in and they wind up making the space smaller -these seem to work well, but placement has to be careful with more than one wire (I seem to recall there are rules about the number of wires?).

Im only an amateur, but Ive always wondered whether screw terminals are designed for a cheap price or for their ability to grip well.

 

[Notch7]

... or maybe 'a thing of the future' once we have as much long-term experience of spring-loaded connectors as we currently have of ones with screwed terminals ?

Kind Regards, John

Well I wondered that.....maybe they could become the 'push fit for electrics'

 

[Harry Bloomfield]

JBs generally have a round hole for the wire and a screw. With say 2 wires, the screw may bite on just one, or it may bite mostly one one and the other may just get trapped. Diyers may get over it by twisting wires together, something pros avoid -esp these days of testing.

Im only an amateur, but Ive always wondered whether screw terminals are designed for a cheap price or for their ability to grip well.

The traditional JB's have a slot for the wires, which includes threads. There is not much point to a JB unless there are at least two wires to be joined. The best way is one wire in from each side of the slot.

I have come across many poor quality screw terminals, but the better ones are fine. I would trust a good screw terminal more than I would trust a spring terminal like a Wago where some current is involved. The better ones have screws which are of a diameter which almost fill the terminal, leaving no room for a wire to be missed down the side of the screws. There is some small amount of technique to ensure screw terminals work well and prove to be reliable - you should ensure the bared wires are long enough, insert them give them a waggle to settle them a the screw is tightened down, you then give each wire a final tug to ensure there each has 'caught' and none have any movement in the terminal.

 

[JohnW2]

There is not much point to a JB unless there are at least two wires to be joined.

True, but that does not necessarily mean that the two (or more) wires have to go into the same 'hole' and be secured by the same screw (any more than they do {with a spring, rather than a screw} in, for example, a Wago connector).

We very rarely seem to see 'two screws per terminal' (as in Wylex Standard days) - which seemed to be a very sensible bit of 'belt and braces'.

Kind Regards, John

 

[donrkebab]

Any cable joint or termination will be electrically adequate as long as the cable csa is maintained. ie a 2.5 ²mm cable only requires 2.5 ²mm of electrical contact.

 

[JohnW2]

Any cable joint or termination will be electrically adequate as long as the cable csa is maintained. ie a 2.5 ²mm cable only requires 2.5 ²mm of electrical contact.

... provided that the quality of the 'contact' is, and remains, adequate.

Kind Regards, John

 

[donrkebab]

... provided that the quality of the 'contact' is, and remains, adequate.

Were would we be without you?

 

[JohnW2]

Were would we be without you?

You tell me!

However, to my mind the important point is that discussions about the adequacy and relative merits of different ways of making joints in cables (or 'terminations' between cables and accessories/equipment) very rarely even consider the CSA of the contact between conductors (since that is nearly always numerically adequate, if the joint/termination is done correctly) - but, rather, concentrates on how good is the contact between conductors (i.e. how low impedance) and how well maintained is initial 'good contact' over long periods of time in service.

Kind Regards, John

 

[donrkebab]

You tell me!

However, to my mind the important point is that discussions about the adequacy and relative merits of different ways of making joints in cables (or 'terminations' between cables and accessories/equipment) very rarely even consider the CSA of the contact between conductors (since that is nearly always numerically adequate, if the joint/termination is done correctly) - but, rather, concentrates on how good is the contact between conductors (i.e. how low impedance) and how well maintained is initial 'good contact' over long periods of time in service.

Kind Regards, John

Do you mean loose terminations joints are a bad thing?

 

[JohnW2]

Do you mean loose terminations joints are a bad thing?

You seem to be the expert at interpreting (or misinterpreting) what I write, so I leave you to decide the answer to that one.

 

[dk1uk]

Sorry for being super cautious but just to be safe on ensuring that I’m not overloading the circuit by adding two more lights.

The garage seems to be on it’s own circuit. Here’s a pic from the consumer unit. I’ve tried turning off just the garage at the consumer unit and checking lights in the rest of the house and it seems to confirm that that switch is only for the garage.

And therefore, four fluorescent lamps is absolutely fine?

Thank you.

 

[Harry Bloomfield]

Assuming it is just an ordinary domestic garage, it will be fine.

 

[dk1uk]

Hello again, thinking of the cable to buy - would 1.5mm twin core plus earth be right?

Many thanks

 

[Harry Bloomfield]

If that is what has been used on the rest of the circuit - yes!