Mains extension leads - daisy-chaining

[Joe]

It's one of those rules you tell everyone, then you tell the ones who understand Amps when to ignore it. Like the one about not carrying solder to a joint on the iron, which is occasionally unavoidable and not a problem for an experienced solderer.

The worst problems I've seen with extension blocks have been contacts, either poorly-crimped internal bus joints or bad contact with the fuse. Plugs also have fuse problems, mostly spring tension contacts weakening with time. These problems are independent of the number daisy-chained but very dependent on load.

I've seen (but not used) a Japanese multi-way extension which was literally two slots in a plastic block. The number of insertable plugs depended on how bulky the plug body was. Earths, shutters... what are they?

OK, they're only on 100V but that's still fairly dangerous.

[Pamela]

My Netgear wifi powerline adapters don't work well if they are plugged into a trailig socket attached to another trailing socket.

[zaq]

Not for low powered devices like plug packs.

And there are relatively expensive very viable systems with that approach on the 240V system.

[John Rumm]

Most powerline adaptor vendors caution against using any form of extension lead...

[Colin Bignell]

On 11/07/2022 19:48, Pamela wrote: ...

When my late partner had an oxygen concentrator, I was warned that it would get very upset if not plugged directly into the wall socket. That was even one of the first questions when I called to say the first one we had was showing warning lights.

[Robin]

I can understand that being the default advice with any medical equipment for fear of the voltage drop should someone use 10m of bell wire to extend it but I'd like to know if there's anything more to it than that. Only static concentrators I've seen took a max of around 500 W so even 50m of 1mm would only drop 5 V.

[John Rumm]

Perhaps they are more worried about scope for a poor arcing connection combined with and O2 rich environment?

[Colin Bignell]

The engineer who installed it couldn't explain why, but assured me that using an extension lead was a common reason for him to get called out to a machine that was showing error lights. It doesn't make any sense to me either.

[Colin Bignell]

The engineer said it lead to the machine malfunctioning. The warnings about the use of oxygen were an entirely separate part of the introduction briefing. Also, there were no such warnings about the portable machine I bought, which was a proper medical one, not one of the low yield ones you can buy from Amazon.

[Mark Carver]

I spent the first weeks of my life in an incubator, that was connected to the mains by the bare ends of the mains lead being stuffed into the socket holes with matches.

[Andy Burns]

My dad had a drill like that, but I'd like to think if my life depended on it he'd have found a 13A plug, even one where the back part had been "notched" after he'd forgotten to thread the cable through the hole before wiring it :-)

[Mark Carver]

 For the first few months of my life, my parents still had a van. They'd just lob me in the back, and my cot would slide around in there accordingly.

[Mark Carver]

Actually I do recall one of those Public Information films on the telly in the 70s, where a bloke is using the same technique for his electric drill, and the Earth wire falls out of the socket and contacts the Live one, resulting in disaster ?

[Mark Carver]

Here we go !

[Brian Gaff]

Well, I have to say, as long as the final one plugged in is fused correctly, I have never had any issues. I think sense should prevail though, for example running a 3KW fan heater on the fourth in a chain might be asking for trouble if any of the extension sockets makes poor contact either to the plug or internal bus bars in the bar.

For things like hi fis, as long as you are not using very silly powers or running a server farm of computers, I've never had problems except of course if there is a bad connection, you can get crashed computers and even TVs. Never buy such things from el cheapo outlets, and periodically inspect them for problems as they do tend to get kicked, trod on and wires run over by castors and vacuum cleaners over time. Brian

[Robert]

+1 That is the basis I think for the advice ! Lot to be said for fitting 5A fuses in 4 way blocks ( plus labelling) to discourage use with heaters, kettles etc.

[Robin]

It's a poor workman who blames the matches. I was taught to break the match off flush with the socket and stuff the bit left over in to make a tighter fit.

And real men used Swan Vestas.

[John Rumm]

I have had calls along the lines of

"My computer and screen just went off!"

after a bit of digging you work out there is no power getting to the machine and ask them what they were doing when it went off.

"I was just plugging in my fan heater, its really cold in here".

"Does the fan heater work?"

"No"

"What socket did you plug it into?"

"That 4 way one under my desk"

"Do you mean that one with the really big label with bright blue lettering that says "for computer use only" on it?"

"Yes, that's the one"

Then follows an explanation on how to reset the trip on the 800VA UPS that they just tried to pull 3kW out of!

[Colin Bignell]

Reminds me of a girl at university asking me to look at her electric kettle, because it wasn't working. Her grandfather had fitted the plug and connected the earth wire to the live pin. Fortunately, when it was plugged in, she had only picked the kettle up by its Bakelite handle.

[Adam Funk]

Ha! I didn't see that coming.