Energy Monitoring Products - What is it?

**Brian Hannigan** · 09-13-2007, 09:39 AM

I had a "What is it?" question come through my e-mail so I thought I'd share it here.

The answer as I understand it is a device/meter for separate tenant billing.

Here is some info.

E-Mon D-Mon Class 1000 Meters

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**Jerry Peck** · 09-13-2007, 06:19 PM

Brian,

That's got me scratching my head ... that would only work (as shown in the photo and material) if each phase supplied one tenant, but that would mean there would be no 240/208 volt circuits, just all 120 volt circuits.

Those were also advertised as being good for separating the load from different departments in one tenant, and that would be done by installing those on the branch circuits feeding that department.

Right now, though, for the photo shown, I'm still trying to figure it out - they are using other than just 120 volt circuits.

**Bruce King** · 09-13-2007, 06:48 PM

Check out the wiring diagrams

http://www.emon.com/pdfs/Meter%20Ins...verview%20.pdf

**Jerry Peck** · 09-13-2007, 06:55 PM

Bruce,

I did check out all those links.

But ... if you put a current sensing coil on each phase, it will read what is going through each phase, not what is being tapped off a breaker below.

Thus, unless each tenant ONLY has a single phase and the neutral (i.e., 120 volts) how can you tell what Tenant A used between A and B phases and Tenant B used between B and C phase and Tenant C used between phases C and A?

I'm stumped.

Now, if you only had Tenant A on phases A and B and Tenant C on phases B and C, then yes, you don't even need to measure phase B, only Tenant A is on phase A and only Tenant B is on phase C, with phase B being combined load between them, but who cares, you can measure phases A and C.

Right?

**Bruce King** · 09-13-2007, 09:00 PM

Looks like you have to use the Class 4000 meter for multi-family.

The docs. for the 4000 are not correct, the links come up with 1000,2000,3000 series wiring and not the 4000.

E-Mon D-Mon Class 4000 Meters

It takes more wiring and sensors for the 4000 and they don't have a diagram available on the site.

**Jerry Peck** · 09-14-2007, 05:55 AM

Originally Posted by Fritz Kelly

I have seen similar boxes put on by the power company, presumably if they think the meter is bypassed or something. I saw one on a neighboring unit when I was renting a commercial space but don't know if there were the coils in the panel.

Fritz,

I think you saw CT's, Current Transformers, which monitored the current flow through the conductors and displayed the power used on the CT meter. There is a direct relationship between the current through those coils and the voltage output from those coils (they work the same way a transformer works - based on the magnetic fields generated by ac current flow), the voltage output is used to run the power meter and record the power used. I've seen these on several large homes with large amp services.