sub-metering for tenants

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SceneryDriver

Senior Member
Location
NJ
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Electrical and Automation Designer
All,
My employer is interested in setting up sub-metering in areas of our building complex that are set to be rented out to tenants. The rental spaces are (conveniently) fed from single feeders going to subpanels for each space, so metering should be relatively straightforward (no need to meter multiple circuits, for instance).

I imagine the sub-meters will need CT's on each phase, plus voltage references for each phase; is this correct?

Here's where I'm unclear:
1) Power is corner-grounded delta 240V 3-phase. What does that do to our metering situation?

2) We're located in NJ; are there requirements beyond the need for the sub-meters to revenue-grade in order to bill tenants?

2a) Are we required to get permission/approval from our service provider to do this (PSE&G)?

3) the few sub-metering companies we've spoken to have all been spooked by the corner-grounded delta supply. Can anyone recommend a good vendor who understands corner-grounded three phase power?



Thanks,

SceneryDriver
 
jumper said:
2(a)-yes you had better check. Some POCOs and/or jurisdictions do not allow this.

Only POCO metering in some areas.
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That is only POCO is allowed to bill for power consumed. You can meter anything you want, you just cannot charge the tenant a fee based directly on how much power they are using.
 
GoldDigger said:
That is only POCO is allowed to bill for power consumed. You can meter anything you want, you just cannot charge the tenant a fee based directly on how much power they are using.
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Agree. But when leases are signed or renewed, rental rates can typically be adjusted to factor in past electric usage and cost.
 
SceneryDriver said:
All,
My employer is interested in setting up sub-metering in areas of our building complex that are set to be rented out to tenants. The rental spaces are (conveniently) fed from single feeders going to subpanels for each space, so metering should be relatively straightforward (no need to meter multiple circuits, for instance).

I imagine the sub-meters will need CT's on each phase, plus voltage references for each phase; is this correct?

Here's where I'm unclear:
1) Power is corner-grounded delta 240V 3-phase. What does that do to our metering situation?

2) We're located in NJ; are there requirements beyond the need for the sub-meters to revenue-grade in order to bill tenants?

2a) Are we required to get permission/approval from our service provider to do this (PSE&G)?

3) the few sub-metering companies we've spoken to have all been spooked by the corner-grounded delta supply. Can anyone recommend a good vendor who understands corner-grounded three phase power?



Thanks,

SceneryDriver
Click to expand...

I dont see why a utility would care. I think it more often comes down to any state regulations you have. Some dont care, some say its ok as long as you dont profit or mark up the power, others from what I hear prohibit it all together.

I have installed and used EKM meters. They work well, are affordable, and are revenue grade. www.ekmmetering.com They can do the corner grounded delta no prob.
 
mike7330 said:
They are a private metering company
I’m not associated with them.
Click to expand...

Mike, I think he was asking whether the meters being read and managed belonged to POCO or were privately installed downstream of the service point.
I understand your answer to mean that they are not POCO meters.

Some power management services just copy the information that the POCO smart meters are broadcasting.
 
GoldDigger said:
Mike, I think he was asking whether the meters being read and managed belonged to POCO or were privately installed downstream of the service point.
I understand your answer to mean that they are not POCO meters.

Some power management services just copy the information that the POCO smart meters are broadcasting.
Click to expand...

They are all sub meters, POCO has their meters in the
Main switchgear room

The rest of the Quadlogic Meters are though out building on each floor
CT type
Meters “talk” to each other through building wire
With internet connection in basement for
Remote reading and billing
 
SceneryDriver said:
All,
My employer is interested in setting up sub-metering in areas of our building complex that are set to be rented out to tenants. The rental spaces are (conveniently) fed from single feeders going to subpanels for each space, so metering should be relatively straightforward (no need to meter multiple circuits, for instance).

I imagine the sub-meters will need CT's on each phase, plus voltage references for each phase; is this correct?

Here's where I'm unclear:
1) Power is corner-grounded delta 240V 3-phase. What does that do to our metering situation?



3) the few sub-metering companies we've spoken to have all been spooked by the corner-grounded delta supply. Can anyone recommend a good vendor who understands corner-grounded three phase power?



Thanks,

SceneryDriver
Click to expand...

Regarding this part of your question. I don't know why the meters would care if your system is corner grounded. It still has voltage and the amps still flow. The measurement is analog. It should care not.
 
Strathead said:
Regarding this part of your question. I don't know why the meters would care if your system is corner grounded. It still has voltage and the amps still flow. The measurement is analog. It should care not.
Click to expand...

I believe he is mostly asking questions and talking about people's lack of familiarity with corner grounded systems because while many here are knowledgeable about this system, it is a somewhat rare beast for a lot of us.

I only learned about them when I joined here and still yet have never worked or encountered one. I prolly would have freaked if I had come across one before it was explained to me.

I knew standard WYEs and High leg Deltas, had heard of Ungrounded Deltas, but Corner grounded-nope, nada.
 
jumper said:
I believe he is mostly asking questions and talking about people's lack of familiarity with corner grounded systems because while many here are knowledgeable about this system, it is a somewhat rare beast for a lot of us.

I only learned about them when I joined here and still yet have never worked or encountered one. I prolly would have freaked if I had come across one before it was explained to me.

I knew standard WYEs and High leg Deltas, had heard of Ungrounded Deltas, but Corner grounded-nope, nada.
Click to expand...

I installed "fisher price my first corner grounded delta" system just a few months ago. Small SDS for an old 600 V elevator. Never saw one before that.
 
electrofelon said:
I dont see why a utility would care. I think it more often comes down to any state regulations you have. Some dont care, some say its ok as long as you dont profit or mark up the power, others from what I hear prohibit it all together.

I have installed and used EKM meters. They work well, are affordable, and are revenue grade. www.ekmmetering.com They can do the corner grounded delta no prob.
Click to expand...
Yes. To sell energy you need to be properly authorized, collect applicable taxes and other fees just like the utility companies do.

To raise your rent/lease fees and include utilities in what is provided is usually fine though. This can leave you with extra some months and short other months - most probably average the yearly use out in determining what to include per month. You can certainly install meters to monitor usage to help determine what those fees should be.
 
A little late on this thread, but here's my POCO input....Most utilities do not want to be involved in sub-metering. They will bill based on one utility meter and what the customer does after that is not their concern. There are, however, local or state regulations that limit or forbid billing of customers based on sub metering, even if the meters are revenue rated. As far as corner grounded 240 Delta, you used to see a lot on farms where pumping stations were involved. The corner ground provided a basis for ground fault tripping if either of the ungrounded phases become grounded. On an ungrounded system, by code, you'd have to have ground fault detectors, which isn't really practical on remote power lines. Plus, there's no available 120V as there is in the 4W Delta. Just for the cost of one more service wire? I think that's why it's pretty rare.
 
meternerd said:
A little late on this thread, but here's my POCO input....Most utilities do not want to be involved in sub-metering. They will bill based on one utility meter and what the customer does after that is not their concern. There are, however, local or state regulations that limit or forbid billing of customers based on sub metering, even if the meters are revenue rated. As far as corner grounded 240 Delta, you used to see a lot on farms where pumping stations were involved. The corner ground provided a basis for ground fault tripping if either of the ungrounded phases become grounded. On an ungrounded system, by code, you'd have to have ground fault detectors, which isn't really practical on remote power lines. Plus, there's no available 120V as there is in the 4W Delta. Just for the cost of one more service wire? I think that's why it's pretty rare.
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Utility supplied corner ground delta here is always 480 volts. Is also typically serving definite purpose loads - like your mentioned pumping stations - Might be 120 volts there but is derived from 1kVA or less control transformer and just runs controls.

Most of them you run into are existing and new installs will be 480/277 or in remote areas or limited kVA applications might be supplied by open delta - but they do provide 4 wire with high leg anymore. I think main reasoning is to have less volts to ground though it is a little stupid IMO. High leg is still 416 on such systems and 240 to ground is reasonably close to 277 - you really don't want to get caught up in either.

1400 feet of three conductors instead of 4 is a fair cost difference when the fourth isn't really needed.
 
All,
Just getting back to this thread now. Thanks for the metering recommendations. We've reached out to EKM and are waiting to hear back. I'm not sure about the rules regarding billing; that's above my pay grade.

Several other metering companies didn't really know what to do with corner-grounded delta power. Though it may not be as common as it once was, there's still a huge installed base, especially in older parts of the country, like the East Coast. I've been somewhat lucky in my career (I guess) to be exposed to all manner of supply types; corner-grounded and high-leg deltas, wye, ungrounded, etc... I would've thought a metering company would be familier with these typologies as well.

Thanks again for the help!


SceneryDriver
 
SceneryDriver said:
All,
Just getting back to this thread now. Thanks for the metering recommendations. We've reached out to EKM and are waiting to hear back. I'm not sure about the rules regarding billing; that's above my pay grade.

Several other metering companies didn't really know what to do with corner-grounded delta power. Though it may not be as common as it once was, there's still a huge installed base, especially in older parts of the country, like the East Coast. I've been somewhat lucky in my career (I guess) to be exposed to all manner of supply types; corner-grounded and high-leg deltas, wye, ungrounded, etc... I would've thought a metering company would be familier with these typologies as well.

Thanks again for the help!


SceneryDriver
Click to expand...
They may have design staff that understand it - but it may not be something they have any inventory parts for either. Most of what they sell is probably for 480/277, 208/120 or 120/240 single phase.
 
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