OpenEnergyMonitor Community

Pre purchase questions

Hi all,

New to the community. I want to measure a number of items in our household. These are as follows.

Solar Generation
Import/export to grid
Heat pump usage
MVHR usage
Hot water
Zappi car charger usage.

I’m not sure of the best setup to purchase.

Our Inverter is in the attic.
We have 2 consumer units in the utility room.
Our main home supply and meter is on the outside of the house.
We have a cat6 cable from the attic to the consumer unit.
We have a few more cat6 cables from the consumer unit to the garage where the Zappis are.

I’m thinking an emonPi and TX but I don’t have a plug socket near the consumer unit.

Are the CT clamps extendable over Cat6?

Im think all CT’s extended over cat6 and emonPi and TX located in the garage. The garage has a network switch and WiFi there also which links back to our main plant room and home network.

Is the above a sensible approach?

Many thanks

Current transformers (please, they’re not “clamps” - you must never, ever, “clamp” a ferrite-cored c.t. onto a cable, you’re very likely to crack the core and render it useless; the only clamps I know about in electrical engineering are busbar clamps, “clamps” for c.t’s must be a mis-translation somewhere along the line) should be usable over CAT 6, but I’d be concerned over the possibility of broken cores unless you’re careful with the terminations. I normally recommend instead a good quality screened microphone cable, especially if the length is significant.

Presumably, your P.V. inverter feeds into your ring main in the attic, hence you need a c.t. up there.

Do you have access to the grid connection inside the house? You mention two C.U’s in the utility room, and another C.U. Is it that one that is fed direct from the meter?

It’s always better not to have sensors on the ends of long cables, and especially if the cables run parallel to (and worse, right alongside) power cables, and especially if there are motors and fluorescent lights being switched, because it’s a recipe for noise and interference that can be quite hard to eliminate. But if there’s no real practical alternative, then you’ll have to see how it goes.

Hi Robert,

Thanks for the reply.

I’ve seen CT’s extended before using Cat cable with no issues. The Cat cables are shielded and ran through separate ducts from power, this was specified at build stage. Distance is about 30metres.

The utility meter is in a Pirelli box on the outside of the house. The utility room is on the inside of this wall and that’s where the 2 consumer units are.

The solar PV goes back to the consumer unit so presumed at CT can go there?, or at the inverter in the loft if required.

If that saves a long cable run, and the feed is direct, then that’s clearly the preferred option.