I can open the face of the consumer unit - but think I would need the electrician (involved in the house
construction) to do anything beyond that. He does need to come back at some point to fix a motorized ceiling window, so if I had exact instructions on what he needed to do, I could make it happen.
If he is willing to, you need to clip one of these around the supply cable (either live or neutral - right terminology @Bill.Thomson?) .
Could probably feed the CT cable out the top of the consumer unit. You will then need a double socket nearby as well for the emonPi.
If not, your only option is the battery powered emonTX I’d suggest.
I think it depends where you live. Active+Neutral in Australia. Phase+Neutral in NZ.
Thanks Brian,
I think the CT cable out of the Consumer Unit, there is already a double sockets nearby .
Is there a diagram or photo anywhere?
Ray K
Of what?
Of wiring the CT into Consumer Unit, would be only nice to have.
You just clip it over in the incoming supply cable (but either the live or neutral not both as I said).
the usual view can be seen here — Solar divert showing as export - #6 by nisirob
Robert will remind you that both conductors are considered live.
(which is also the case here in the US)
We call them “hot” and neutral.
However, Robert also told me that in the UK, “hot” refers to an overheated conductor.
The correct terms are line and neutral.
If the neutral becomes disconnected on the supply side, then the neutral on the load side of the break may be live at line voltage. That’s why both line and neutral are regarded as live conductors.
If you can do that and supply a picture, one of us can mark it up with where to fit the c.t.
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Ok - so look before I do anything else, let me at least order a CT cable, so I am ready to go in case the builder’s electrician happens to materialize.
This one looks pretty bulky, is the a neater one for putting inside the Consumer Unit?
Unfortunately not on the main incoming cables. That is a “split-core” one, which you need to get onto the cable without disconnecting anything - and you can’t do that safely unless you have your own isolator between the meter and consumer unit, which most people don’t have, or without taking the supplier’s fuse out, which means breaking their seals (and they don’t like that).
The approximate overall dimensions of the SCT-013-000 are 22 × 36 × 57 mm. If you do get one fitted, it can go on the line (which way round according to the arrow on the case) or neutral (the other way round) and really you should short the plug tip to sleeve until you get whatever it plug in to. It ought to be OK without the short, but you’re relying on the protection device inside, so it’s best to be careful.
Actually, I think he might. I remember thinking how useful that was when I saw the photo. I know you don’t like following links to off-site photos, so here it is:
I missed those. That’s one more reason NOT to link to third party sites, but to post all pictures here.
In that case, disconnecting the line inside the C.U. is possible, and a ring-core c.t. will be significantly smaller for the same rated current.
If space is at a premium inside the C.U, then knowing the maximum current you will see is important. There’s this range from RS https://uk.rs-online.com/web/p/current-transformers/7754903 which appear to be directly usable, but the maximum rated current is 50 A, so check the hole size as well as the outside dimensions (and note, if you fit one of these, it MUST be shorted while not connected, else it might be destroyed as there is no protection across the secondary winding).
I am going to open the consumer unit tomorrow and get some photos. I was looking at sensor above - it looks like I would need to connect it to a 3.5mm audio jack right, and possibly extend the cable in order to connect it to the emonPi.
Don’t suppose there is a wiring diagram?
Ray K
You’re correct there. As the lead is only 120 mm long, you’ll almost certainly need to have a connector of some sort and further length of twisted flex to your jack plug - connect to tip and sleeve, there’s no connection to the ring (a mono plug should do too). As there’s no phase information on the c.t. data sheet, I can’t tell you which colour goes where, but note, the tip of the plug is “earthy” to a.c. but sits at 1.65 V d.c. above the emonTx or emonPi ground, and the true signal is the plug sleeve and body. I don’t advise using screened audio cable connected conventionally with the screen to the plug sleeve.
Note that if you’re using screwed terminals or crimps, then for reliability you must cut the tinned ends of the wires off.
Hi Folks,
Pictures of the consumer unit below as discussed. Looks like there should be enough room in there alright. Couple of points of note:-
- Main Switch
- External Heat Unit (collection fan)
- Internal Heat Unit
I have two CT Sensors, so ideally I would like to monitor both the incoming supply to get the total, and the Thermia Air-to-water Heat Pump separately. Not sure how to monitor the Air-to-water system since it is split into two, which is the more important the internal or external unit?
Thanks,
Ray K
Yes, I think you stand a chance there.
Simple - pass both brown wires through the same c.t. The magnetic fluxes will add in the c.t., and you’ll see the total current. Just check what the actual ratings are - I can see one is a 32 A MCB and the other is a 40 A RCD - but I’m betting the total is not 72 A, though it might be too much, especially on the hole size, for the smaller 50 A AZ-1000 c.t. and you need the physically bigger ACX-1075. It’s hard to see how much space is available behind the breaker mounting rails - have a good look and measure (with a wooden or plastic ruler!).
So what I have are 2 x SCT013 that are rated for 50mA → 100A, these are what I got with the EmonPi. I doubt I am going to be able to squeeze both brown wires for the heat unit through the SCT013’s hole. I didn’t think to pull out the plastic calipers - but I was thinking/hoping I might get away with the SCT019? As there appears to be a good bit of room above the trips, it should be ok …
The ACX-1075, looks like I would need to make up a cable right?
I marked up the image with where I think I ought to be putting the C.T.'s, can you confirm that I am on the right track pls.
Thanks,
Ray K
For the heat exchanger, those are the wires.
I’d have thought you would certainly get those 2 wires through a SCT-013-000. It’s hard to tell the wire size from the photo, a single core BS6004 at 4 mm² is rated at 32 A in conduit (so more than that given the air circulation that you have) and is 4.1 mm diameter overall. Likewise, a 6 mm² is 41 A and 4.6 mm diameter. If the installer went up a wire size, then the 10 mm² is 57 A and 5.8 mm diameter. My maths says a 6 mm² and a 10 mm² is less than 13 mm, which is the hole size you have.
For the main switch, the c.t. needs to go on wire into the bottom of the main switch, which should be the tail coming from the meter box outside.