Ethernet in the consumer unit.

[MattChan]

I'm currently working on a product that in an ideal world would mount in a spare fuseway inside a consumer unit. The only slight issue is that it needs a RJ45 ethernet connection to get the data into and out of it.

I was worried if any regs prevent ethernet etc from being inside the CU? I'm guessing I will be ok doing this as its not much different to the output of a doorbell transformer being inside there?

 

[electronicsuk]

I suppose your main concern would be that the insulation of the network cable is rated to at least the same voltage as the power wiring present in the CU. There are plenty of control systems that combine ethernet and power in the same enclosure, so there's nothing that specifically prevents you from doing as you propose.

 

[MattChan]

Ah very true. Comparing to the doorbell transformer situation I see that bell wire used within the CU should be sleeved up to increase its rating and they just seem to include this in the transformer instructions. Hopefully I can get away with a similar approach or supply a meter or so of sleeving with the box of tricks.

 

[bernardgreen]

in an ideal world would mount in a spare fuseway

Will this device have any connection to the live and / or neutral in the CU ?

If so then you will need to ensure that there is adequate insulation and separation between the ethernet circuitry and the mains circuitry inside the unit.

The hazards created by mains getting onto the data cabling can be serious, with risk of damage to data equipment and risk of electrical shock to anyone working on the IT network.

Test voltage for the insulation is normally 2000 volts for such equipment.

The insulation and separation has to be maintained during and after faults in the equipment.

 

[Lectrician]

With Part L of the building regs, it is becoming common to fit meters within either the MCCB board, or submained boards etc on larger installations.

Although the majority of these are standalone, many do incorporate an RJ45 network port (or two) to allow them to be interogated remotely. There is no specific segregtion in the panel boards I have used....

 

[MattChan]

Will this device have any connection to the live and / or neutral in the CU ?

If so then you will need to ensure that there is adequate insulation and separation between the ethernet circuitry and the mains circuitry inside the unit.

Yup L and N connection the data port will be galvanicaly isolated from this by the power supply and the ethernet magnetics. 6.5mm minimum mains to ELV separation across PCB for creepage and clearances. Just got to try and cram all the electronics in and keep those clearances.

 

[ban-all-sheds]

I suppose your main concern would be that the insulation of the network cable is rated to at least the same voltage as the power wiring present in the CU.

I think his main concern should be how many CUs have unused ways in them, and therefore how large a target market he will have.

 

[Geps]

Pink Cat5e cable has a mains rated insulation. C-bus shop sell it.

No connection, not a customer etc.

 

[Chri5]

Would it not be better design if the connection was outside the CU?

Unskilled hands shouldn't be opening up a CU to access a data port.

The connection to power suggests that is to drive the unit, sounds like some sort of meter / usage sniffer. Wouldn't a wifi / wireless Ethernet transmitter be the easiest user option ?

 

[MattChan]

I think his main concern should be how many CUs have unused ways in them, and therefore how large a target market he will have.

This is only a small part of a large system. They won't mind having another cu box fitted to just be an enclosure for these modules.

 

[Monkeh]

Pink Cat5e cable has a mains rated insulation. C-bus shop sell it.

No connection, not a customer etc.

Just because it's pink doesn't mean it's rated for 230V.

 

[bernardgreen]

6.5mm minimum mains to ELV separation across PCB for creepage and clearances. Just got to try and cram all the electronics in and keep those clearances.

In the small volume available you may have problems ensuring that separation in maintained after a fault that causes charring of the PCB or deposits from vapourised metal.

I think his main concern should be how many CUs have unused ways in them, and therefore how large a target market he will have.

Based on those two concerns I would design the unit to be external the CU to remove the severe contraints that limited volume will impose on the PCB design. ( does this involve a current sensor ? )

Use of a fibre optic data connection between the module and an ethermet gateway outside the CU would make the system safer and make the PCB design less safety critical.

 

[ban-all-sheds]

This is only a small part of a large system. They won't mind having another cu box fitted to just be an enclosure for these modules.

OK - so this is a particular project for a particular customer? Not something you're developing to bring to market?

If it's going into a large, non-domestic environment and they need an enclosure to house it why would they put a CU in?