CT coils outdoors

Hello, would it be possible to locate the ct coils outdoors in a sheltered under eve area where the weather head comes into the building with the overhead lines, with some kind of weather proofing on the CT’s and then extend the ct cables indoors to the Emonpi ?

I don’t see why not, provided that the insulation on the main conductors is sound. (They are single conductors aren’t they, for the two lines and neutral, not a 3-core cable?) The “shop” c.t’s are good to 1000 V “between shell and output”, but you MUST check the data sheet for the ones that you are using, so provided that it doesn’t get damp through rain, mist or condensation, you should be OK.

There’s an article in “Learn” about extending the leads.

Hello, yes it’s aerial service entrance wire common here in the US. there are two black insulated hots 120 Volts on each line twisted around one bare silver neutral wire.


Hi Adam,

One thing to keep in mind. Your SEWs are more than likely AWG 4/0 Aluminum. If that’s the case, you won’t
be able to use the CTs sold in the OEM Shop as they are too small to acommodate wires that large.

There are suitable substitutes listed on the Use in North America page in the Learn section of the site.

Ok, sorry for the late reply. I have a 100 amp service. I believe the wires going into the house might be 2 or 3 AWG copper. I was also wondering would it be ok to run a shielded cat5e cable down the conduit with the feeder cables and ground the foil and ground wire inside the building by by the Emon pi?


If your Service Entrance wires are Aluminum, it’s likely they’re AWG 4, (use of AWG 3 is almost unheard of) otherwise, if they’re Copper, they might be AWG 2 - if the jacket type is THHN.
(easy to tell by looking at the wire jacket, it should be marked)

If they’re AWG 2 their OD (Outside Diameter) should be ~0.52 inches, which mean the CTs
sold in the OEM Shop might accommodate your wires. The SCT-013 has a 13mm wire window
(0.51 inches) so I’d recommend measurng your SEWs, if possible.

If by that you mean run the Cat5 inside the conduit, no.
The NEC says high and low voltage wiring must not occupy the same conduit.

If you mean run the Cat5 down the outside of the conduit, yes, that’s OK.

That should work provided you have a suitable ground near your emonPi.
Be sure you ground only one end of the cable.

Ok, great. The other thing I was confused on was with the CTs, does each hot lead coming in need a CT, do the CTs need to be clipped on so one has arrows pointing toward the building and one pointed the opposite direction, should the Emonpi be shutdown and unplugged when connecting the CTs, and should the CTs be taken off the mains if the Emonpi needs to be disconnected from them for any reason?


Yes, and yes.

If your emonPi is running when you disconnect your CTs, it’d be a good idea to reboot after
you reconnect them.

When connecting / disconnecting CTs:

Connect the CT to your emonPi before you clip it around a current-carrying wire,
(make sure each plug is pushed all the way home in each jack)


remove the CT from the current-carrying wire before you disconnect it from your emonPi.

The easiest and safest way would be to kill the power to the current-carrying wire(s).
i.e. turn off power at your main breaker.

If that’s not possible, you’ll be OK as long as you follow the two points mentioned above.

And plug in the c.t’s before you power up your emonPi, otherwise it won’t recognise them. Rebooting the Pi won’t rectify that, the c.t’s and a.c adapter are only recognised at a power-up.