Desperate for some help on Connecting (Pics and Video)

Just a quick comment on having clamps not all the way closed. If you open a clamp by as much as a millimeter it’s reading goes down by 50% or more immediately. Ask me how I know. If you don’t believe it try for yourself while watching the app. It completely screws things up


@ccook Yes, I’m in Connecticut - wish I had those bigger clamps!!

@Ingo :frowning: - any suggestions if i can’t get them closed tight?

The more I look at this … the more questions I have. These things I’m calling bus bars….

In the middle of that black box - That green wire is a ground wire, the Blue and orange are control wires…… It’s a 400amp relay, making that a old automatic transfer switch and that what the meter base is controlling. Meaning if the grid goes down that either connects to the “main” or disconnects from the “main” depending if that’s NC or NO. Is your “main” breaker interconnected an alternate power source like a +120kW generator ? I’m feel like I’m missing part of this setup.

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Not sure if this will raise more questions than answers but here’sa walkthrough of the setup:

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That’s some serious wiring. I’ll watch that a bit more in the morning.

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The two devices in your main panel marked”400” are actually 400 to 5 amp current transformers. They feed your utility meter. They have nothing to do with the transfer switch.


Regarding the current clamps not being closed your only viable option would be physically larger clamps directly from Sense. A current clamp has a sensitivity expressed in mV/A. And that sensitivity needs to be matched exactly to what the Sense box expects. Else all your readings will be wrong by a factor.

Next, even if you get clamps that physically fit around your wiring the next question is: What is the dynamic range of the Sense inputs? In other words what is the maximum current Sense can process before its input saturates. When you design something like this you normally leave a slight safety margin (e.g. design target is max. current 200Amp and input saturates at 250Amp). While larger currents through the clamps hopefully don’t damage anything the readout will be at its max. That way you use the internal A/D converters efficiently.

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I’ve asked to buy bigger clamps- let’s see. I don’t usually pull too much power (~30-50amps/day)

Yep, He is correct. Metering Current Transformer.


I assume you mean 30-50kWh. If you using 50 amps at 240v that’s 12,000w (aka12kW)… So if that was constant for 1 hour, then for that 1 hour you would have used “12 kWh” (kilowatt hours). Obviously you house is going to go up down up down all day and sense will keep track of that for you.

Any chance you could use the larger nylon zip ties and squeeze the two wires together … Like 2 on the wires and leave enough room for that oval clamp or would they still be too large?

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They are def. too large and they haven’t reverted back re larger clamps =\

Interesting - that’s why the wires running from the mains to his meter are so tiny - no need for the meter to see the full current. Nice call !

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Strange the utility didn’t lockout or install a security/tamper tag on the CT’s or the other box as it’s part of the metering system.

My own curiosity is wondering why such a large service for you house, was it a business at one time or something? If you don’t need such a large service, would you be able to downgrade it possibly saving you on your monthly service portion of your bills?

I’m not sure myself…I mean it’s a pretty big house (7,500 square feet) so maybe that’s why? It’s just my wife and I so we don’t wind up using as much as that panel is capable of but perhaps it was future proofed when built but they likely didn’t predict that items would become more energy efficient. It’d probably cost me more to swap out the system than the additional cost incurred- no?

Maybe one way to save would be to plug those meter plugs somewhere else (just kidding!). Nonetheless, wouldn’t think they could

Also, no luck with support for bigger CTs.

Looks like I may be SOL.

A couple more thoughts:

  • Take a look at the box below your bus bars with the 400A CTs. If there is a genuine split between two different sub panels there, you can use the 2x200 approach. It does look like each leg of your panel on the left uses 2 large gauge wires, but since they are paired together, you might be able to get oblong CTs around both of them on the same leg. Or better yet, it might be that that split is really two wires for one leg taking the upper conduit to your single main panel, with the other leg going through the lower conduit. Have you tried to fit CTs around two of those big wires yet ?

  • If you really can’t make that work, then the next best thing for real-time usage data might be a system that reads your smart meter and provides you Always On, plus usage. I have a Rainforest Eagle that dies that - no native detection, no solar, but does have smart plug and other options. But your utility needs to support “streaming your data” and given your stepdown meter (CL20 is 20A meter - the 400A CTs probably reduce the readings by 20x), you might need to add in a multiplication factor.

Big house is right, especially for 2 people. HVAC costs must be insane unless it been upgraded and zoned.
Probably designed for some unique features with everything going at once when hosting events or whatnot.

I was thinking along the lines it may have been a business converted to residential. Doubt you would see much savings to downgrade but if for some reason you ever had to in the future.

What does that huge breaker feed subpanel, HVAC?
You do seem to have a lot of 240v breakers.

Not really sure if there is a way you can use Sense to monitor everything with that main panel and I don’t really have any suggestions that haven’t been mentioned by others.

Worst case you could use Sense on a subpanel, with the second set of CT’s used on the main panel circuits similar to how some use a roamer smart plug until you get a better idea of what circuits consume what. @kevin1 could guide you down that route if interested.