We have a pair of powerline adapters that are currently working well for us in the main electrical circuit of the house. However our extension (containing eldest son's room) has a separate electrical circuit.

I was wondering if by using 2 adapters, one in the original electric circuit and one in the new circuit in the extension, then connecting them via an ethernet cable would let me (safely) create a connection between the two and bring the extension into our current network?

I have had differing opinions when asking staff in high street stores, one of which told me I might blow up my electrical circuits!

  • 3
    This has a close-vote as 'primarily opinion-based'. I think that's inaccurate. I believe this can be objectively answered. Oct 26, 2015 at 14:00
  • I agree. I'd assume the network bits are electrically isolated and you ought to not blow up anything
    – Journeyman Geek
    Oct 26, 2015 at 14:05
  • 1
    @ChrisInEdmonton I've no idea how this could be considered opinion based, its a 'how do I get this bit of tech to work in this situation' type question!
    – Michael B
    Oct 26, 2015 at 14:22
  • Do you mean using four of these to connect two circuits into one Ethernet segment? Like this: Computer 1 --- Adapter --- Powerline 1 --- Adapter --- Ethernet cable --- Adapter --- Powerline 2 --- Adapter --- Computer 2?
    – gronostaj
    Oct 26, 2015 at 15:04
  • @gronostaj Yes, that's what I was thinking Oct 26, 2015 at 15:19

2 Answers 2


I'm presuming you're talking about 2 powerline adapters, rather than some Frankenstein electrical adapter. My reply here is based on the former, the latter sounds more fraught.

You could certainly use a length of ethernet cable between two powerlines on two separate mains supplies and that would work perfectly well.

However, I'd be very surprised if they are actually separate supplies. Are they both ultimately connected to the same consumer unit? It might be that the round trip distance is just too long for a reliable connection. Have you tried connecting one in the separate supply and connecting to it?

The worst that could happen is that the ethernet traffic would interfere with the powerline traffic (if in they are on the same circuit) and cause network collisions, which would result in poor network performance.

There is no danger in stringing a piece of ethernet between them and seeing what happens. At worst, it won't work.

The best strategy for testing this would be to pair two separate sets of adapters. So A1,A2,B1,B2. plug A1 into router and A2 near the other circuit. Plug something into it at this point to make sure it works. (a laptop etc)

You could also try plugging A2 directly into the separate circult at this point and see if it works.

If it doesn't, get an ethernet cable from A2 into B1 then plug B2 wherever you need it and give it a go!

(I've no idea if that makes any sense at all :P )

  • I can't immediately figure it out. Just a regular ethernet cable between the two powerline adapters, right? Not a cross-over? Oct 26, 2015 at 14:11
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    The majority of ethernet ports these days are smart enough to not need a crossover. Basically plug some ethernet in, if you get lights on the ports, you don't need a crossover. (see revised answer for the rest!)
    – Michael B
    Oct 26, 2015 at 14:15
  • @Michael B Thanks for your help, we'll give it a go with some ethernet cable between two powerlines. I'm pretty sure the circuits are separate as each has its own fuse box Oct 26, 2015 at 14:22
  • @countrygirl the thing to remember is that electrical circuits are rarely, actually isolated. The piece of wire that feeds your house also feeds your neighbours houses (Its slightly more complex with phases) All the fusebox does is create a means for the circuit to be broken if something goes wrong. - in fact it is perfectly feasible to plug a powerline adapter into your neighbours house and for it to work as expected.
    – Michael B
    Oct 26, 2015 at 14:26

Is this what you're attempting OP?

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If it is, then it should function ok. I'm a networking guy though, not an electrician. There is an issue regarding linking different buildings with Ethernet as you create a potential difference that wouldn't trigger a breaker. As your feed will be chained I believe you are safe as its single phase, but you really should consult an electrician before installing anything.

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