HomePlug & Three Phase

[Peter Andrews]

This week I've been 'playing' with a couple of HomePlug Ethernet adaptors at a local church. They worked great between some locations but not others - eventually I discovered (from the architects drawings) that different rooms are on different phases - are there any rules about the proximity of sockets on different phases? The reason I ask is that the two rooms that I want to network are on different phases but it would be quite easy to put a spur in (plasterboard walls) to one of the rooms on the same phase as the other room. The walls are far too thick (24") for wireless and an ethernet cable is not an option as it would require a >50m long run through the church and chapel and I won't be allowed to do it! Listed building, etc.

I've looked at the IEE On Site Guide but cannot find any reference to phases.

Peter

[Jules]

Hmm - no comment on the phase issue, but I'm surprised you can get away with running a spur, yet not with laying some ethernet cable! :-(

[Bob Minchin]

I'm sure I read somewhere that there were such things as 'phase bridges' which would conduct the homeplug RF spectrum between each of the phases . I have also heard that the distance between single phase outlets on different phases should be greater than a body span. I have not been able to find a reference to this however.

Would linking two homeplug units on different phases via an ethernet cable work??

Bob

[dennis]

Ethernet will do 100m so run it around the outside, you could even bury it.

[meow2222]

I'd start by connecting a capacitor between L1-L2, another from L2-L3, and a 3rd from L3-L1. Theres a very good chance that woud solve the problem.

NT

[Dave Liquorice]

Of a suitable voltage rating, 600v? What value? The carrier(s?) are 100 to

200kHz.

[stan]

When you say 'phases' do you mean the 115 volt Leg A and 115 volt Leg B (with 230 volts between them) of a typical North American 'single phase' service? Whereby the two ends of the centre tapped 230 volt supply with a centre tap nominally zero volts neutral is fed into the building!

Because if you truly have 3 phase into the building, not uncommon in certain parts of the world, because it shares the various building loads between the 3 phases, and often allows use of smaller conductors, then you will need to link the wireless signals between all three phases!

BTW your signals will also be receivable by people outside the building?????

Also BTW had the same problem within this average size house, back in the day of those FM intercom that were supposed to work over the house wiring via wall outlets. Some outlets were on one 'side' of the panel/ s and others on the other side and in some cases were on secondary (pony) circuit breaker panels. So we abandoned the whole project. Today cordless phones in the 900 meg. to several gigahertz seem to work OK though.

[meow2222]

We dont have that arrangement anywhere in Britain. If we did, it would require a capacitor between the 2 live phases.

... hence my explanation of how to do it

I dont know what frequency homeplug works on, nor what impedance rf it works with, so its hard to recommend cap values. 1uF caps would cover most possibilities though. For UK 3 phase they would need to be rated at 415v ac class X dielectric.

NT

[Andrew Mawson]

different rooms

ethernet cable

L2-L3,

When you say 'phases' do you mean the 115 volt Leg A and 115 volt Leg B (with 230 volts between them) of a typical North American 'single phase' service? Whereby the two ends of the centre tapped 230 volt supply with a centre tap nominally zero volts neutral is fed into the building!

Because if you truly have 3 phase into the building, not uncommon in certain parts of the world, because it shares the various building loads between the 3 phases, and often allows use of smaller conductors, then you will need to link the wireless signals between all three phases!

BTW your signals will also be receivable by people outside the building?????

Also BTW had the same problem within this average size house, back in the day of those FM intercom that were supposed to work over the house wiring via wall outlets. Some outlets were on one 'side' of the panel/ s and others on the other side and in some cases were on secondary (pony) circuit breaker panels. So we abandoned the whole project. Today cordless phones in the 900 meg. to several gigahertz seem to work OK though.

err - this is UK DIY not US DIY - we have proper volts & amps over here you know

AWEM

[tony sayer]

Why not just use radio links i.e. an access point and a client?..

[meow2222]

600v would be too low. 415v ac is 586v peak, allowing almost no margin for spikes. 1kV would be a more suitable rating. These days though we have class X caps, which due to their extra safety features are safer and more reliable.

Reactance of 1uF at 200kHz is 0.8 ohms. I dont know what the impedance of the local mains wiring is at that f, but I expect that would work well.

NT

[David Hansen]

On Fri, 20 Mar 2009 17:17:47 -0000 someone who may be "Peter Andrews" wrote this:-

Yes. If a higher than usual voltage is present between two items or within an item then this should be indicated by notices. Once the two items are beyond arms length of each other there isn't a need to do this.

It would be easy to put a spur in (presumably between the two rooms) but not easy to put in a twisted pair cable with at least six times less cross sectional area as a 2.5mm2 mains cable? I find it difficult to understand that.

Presumably the church and chapel already have electric wiring within them. How is that run? Surface, buried, what routes? Could a cable resistant to electrical noise follow the same route? Could you use an external grade cable, or indeed an ordinary cable enclosed in conduit (with easy bends).

[Dave Liquorice]

'Cause the source of the ethernet isn't in the next room but 50m away through the building.

Room A has ethernet and power on phase 1. Room B 50m from Room A has no ethernet requirment and power on phase 1. Room C next to Room B requires ethernet but is on phase 2.

Pretty obvious from the OPs orginal post IMHO.

[Peter Andrews]

I've only just caught up with the replies, yes Dave exactly described - I can poke a bit of T&E through a plasterboard partition and put a spur on the right phase within a couple of feet of the router but cannot find if there are any restrictions on mixing the phases in a single room.

Thanks everyone for your comments and interest.

Peter

[Dave Osborne]

There are no restrictions per se, but it is not an appropriate option. There would be an assumption that all sockets in the room would not only be on the same phase, but on the same ring final circuit as well (Unless it was a large room greater than 100m2 in area). Adding a "rogue" only increases the likelihood of an accident.

There is a requirement for labelling where there is any doubt, so if you choose to poke a hole through the wall and add a socket outlet on a different phase, you would then be obliged to label every power outlet in the room with an appropriate label in the form e.g. "FED FROM A/3" except of course for the "rogue", which would be labelled "FED FROM B/12" or whatever (where A,B are respective sub-boards and final circuits are numbered).

[The Natural Philsopher]

You might be able to get decent crosstalk between phases by wiinding a cable rounfd one phase live and around another.

I'm not sure what sorts of speeds these things work at, but to get the data rate it has to be in the Mhz plus region. So you should be able to capacitively couple between the phases. I hesitate to suggest an actual capacitor of 1kv plus rating tho ;-)

[The Natural Philsopher]

You might be able to get decent crosstalk between phases by wiinding a cable rounfd one phase live and around another.

I'm not sure what sorts of speeds these things work at, but to get the data rate it has to be in the Mhz plus region. So you should be able to capacitively couple between the phases. I hesitate to suggest an actual capacitor of 1kv plus rating tho ;-)

[Steve Firth]

It would be a stupid thing to do.

[Steve Firth]

If you're going to those lengths, why not wire in Cat5E rather than mucking about with mains?

[Steve Firth]

Thats a rule of thumb at work where different racks of equipment will be on different phases. The reason for the separation is that one should not be in a position to bridge two separate phases.

The situation in the church really requires documentation and there should be hazard warnings to tell anyone working in the area to *not* use extension leads between the different zones.