Problem with sub-meters

[LarryFine]

Hey, gang. I got a job to look at a service in a large mall. Each store has sub-metering so the mall can recoup electrical costs from the stores. This service is a bottom-fed 480/277 at 2500a.

There are two sub-meters, one an E-mon D-mon and the other has a meter that is shaped like a POCO meter, in a plastic base. I can see both sets of CT's on the busbars through the perforated front panel.

The 2500a main breaker is about 2' up, and the CT's are 18" above it, where the busbars turn from vertical toward the cabinet's rear and then connect to the cabinet to the left, where the feeder breakers live.

Both meters show the present voltages, currents, KVA's and/or KW's, but neither one shows any accumulated KWH's. Is there anything that could happen that would cause both to do this?

The call originated as a troubleshoot, but I recommended removing both and installing a new E-mon D-mon kit rather than spend the time, and my proposal was accepted. The new kit is on order.

However, I am still very interested if anyone has an idea about why both meters would have the same symptoms. But, as Arlo Guthrie said, I didn't come here to tell you that story, but this one:


I'm posting this in Safety because what I really want to know is:

1. What should I have the store shut down before I touch anything? We'll probably do this on a Sunday evening for maximum time.

2. Do I merely shut off the main, or should I, as I think, shut off the sub-panel breakers first to minimize the load? Anything else?

3. Although I'll be a couple of feet above the incoming conductors below the main, can anyone recommend additional safety steps?

4. What about re-energization when I'm done? What have I forgotten to ask?

5. Most important, will I isolated enough to consider what I need to do not qualifying as working live? I want to be both safe and legal.

As always, Danke!

 

[LarryFine]

Lots of views and no takers. Wrong forum?

 

[brantmacga]

I guess none of us know that much about the operation of power meters; at least I don't.

I've never worked in a mall where the owner was sub-metering tenants.

I've worked in our mall; the poco has a meter base @ every store inside. Each tenant gets 480/277, KVA capacity depending on size of the space, and has their own step-down transformer.

I'm not sure sub-metering is even allowed here (for the purpose of recouping costs from a tenant).

 

[LarryFine]

Added: Thanx for responding!

I've never worked in a mall where the owner was sub-metering tenants.

Only the etire mall's service is metered by the POCO. It's up to the mall to either include power in the rent (which apparently caused differences of opinion on power use from both parties) or meter it to divide the bill more accurately.

I've worked in our mall; the poco has a meter base @ every store inside. Each tenant gets 480/277, KVA capacity depending on size of the space, and has their own step-down transformer.

Same here, except for the meter.

I'm not sure sub-metering is even allowed here (for the purpose of recouping costs from a tenant).

My understanding is that it is allowed as long as there's no profit made by the landlord.

 

[kbsparky]

How do they reconcile any "demand" charges? I would not want to have to share in demand charges if I was not a high-amperage customer .... :-?

 

[nakulak]

I'm curious - are you saying the owner knew they would be submetering and installed an extra ct cabt in the gear ?

 

[LarryFine]

How do they reconcile any "demand" charges? I would not want to have to share in demand charges if I was not a high-amperage customer .... :-?

The meter we'll be replacing has peak demand and other readouts besides just kwh.

It's an E-mon D-mon 480 3200 D.

 

[LarryFine]

I'm curious - are you saying the owner knew they would be submetering and installed an extra ct cabt in the gear ?

No. The D-mon kit comes with split-core CT's for installing on existing buses or conductors.

 

[LarryFine]

Check here: http://www.emon.com/products_class2000.htm#

Here are the split cores: http://www.emon.com/pdfs/sensorspec.pdf

 

[IMM_Doctor]

Watch out for gravity

Watch out for gravity

3. Although I'll be a couple of feet above the incoming conductors below the main, can anyone recommend additional safety steps?

Working a few feet above main incoming conductors can lead to bad things. (Mall wont be open on Monday morning).

Does the mall have customer-owned primary transformer with customer accessible primary disconnect switch? If so, open it, and lock it off.

If it is a POCO transformer, have the owner pay for the POCO to shut it down.

Learn from the mistakes of others. We had a little boo-boo quite a few years ago.

 

[brantmacga]

Added: Thanx for responding!

Only the etire mall's service is metered by the POCO. It's up to the mall to either include power in the rent (which apparently caused differences of opinion on power use from both parties) or meter it to divide the bill more accurately.

Same here, except for the meter.

My understanding is that it is allowed as long as there's no profit made by the landlord.

I know of a couple new apartment complexes here that include utilities in the tenants monthly bill, but each unit still has a meter from the poco.

Its a flat-rate charge, not actual usage.

 

[LarryFine]

My maun concern (beyond safety, of course) is that the new meter ends up with the same malfunction as the two existing ones (see OP), because the cause is somehow within the service.

 

[brantmacga]

My maun concern (beyond safety, of course) is that the new meter ends up with the same malfunction as the two existing ones (see OP), because the cause is somehow within the service.

yeh I can't help you there.

maybe a conversation w/ a poco engineer could answer some questions? its possible they've seen this type of problem.

 

[charlietuna]

First all--each meter, regaurdless of manufacturer must have the voltage sensing phase connections connected to match the current sensing phase. In the case of the E-Mon, there is a proceedure to determine if the meter is sensing all voltage parimeters "in phase" with the current monitoring phase. This proceedure is in the E-MON manual ! If you "phase identify" each CT as you install them, then "phase out" the voltage source power--IE: "A" phase voltage sensor connected to "A" phase of the system and "A" phase current transformer connected to the "A" phase CT (with the proper direction--LINE - LOAD !! I f there is a doubt, contact E-mon via phone and let them walk you through it!!

 

[whillis]

For what it's worth, here is my take on this:

"Both meters show the present voltages, currents, KVA's and/or KW's, but neither one shows any accumulated KWH's. Is there anything that could happen that would cause both to do this?"

Did they ever show kWh? My guess is that they are probably not programmed for that function. I can't think of any building distribution centers that I've worked on where the built in meter showed kWh. Usually the revenue meter(s) are located somewhere else and the built in meter is just for troubleshooting.


"1. What should I have the store shut down before I touch anything? We'll probably do this on a Sunday evening for maximum time."

Get the mall administration to advise the tenants that the power is going down. Ask if back-up power is required.

"2. Do I merely shut off the main, or should I, as I think, shut off the sub-panel breakers first to minimize the load? Anything else?"

We normally shut down the sub panels, then trip the main. Are there any PF capacitors on site? If so, we normally allow 15 minutes after power off for them to bleed down before we start work.

"3. Although I'll be a couple of feet above the incoming conductors below the main, can anyone recommend additional safety steps?"

I'd have the POCO shutdown the incoming feed if there was no way for me to isolate the incoming.

"4. What about re-energization when I'm done? What have I forgotten to ask?"

We normally switch on the main, then the subpanels. Depending on the site, we may also require a tenant representative on site to ensure that critical loads have come up or off the transfer switch.

"5. Most important, will I isolated enough to consider what I need to do not qualifying as working live? I want to be both safe and legal."

The legalities I cannot address. As for safe, so long as the entire panel is isolated and locked out, you should be OK. Check, then double check that the buss is dead before starting any work.

If it helps, we've been using Schneider ION 6200 series meters for submetering. We get them 4 to an enclosure and all we need to do is bring in one line voltage feed and the four CT runs for the meters. The enclosure is wall mountable and has the four isolation/shorting blocks installed. It's pretty slick.

 

[LarryFine]

Did they ever show kWh? My guess is that they are probably not programmed for that function. I can't think of any building distribution centers that I've worked on where the built in meter showed kWh. Usually the revenue meter(s) are located somewhere else and the built in meter is just for troubleshooting.

The main stack does have a multi-function readout, but I'm talking about the two sub-meters that were added for the purpose of revenue. This is a single store. 480Y/277 @ 2500a.

Get the mall administration to advise the tenants that the power is going down. Ask if back-up power is required.

Again, this is a single store (Sears) and we'll most likely be doing it on a Sunday after closing.

We normally shut down the sub panels, then trip the main. Are there any PF capacitors on site? If so, we normally allow 15 minutes after power off for them to bleed down before we start work.

As I figured, and I don't believe they have a genny, just data UPS.

I'd have the POCO shutdown the incoming feed if there was no way for me to isolate the incoming.

I'll check, but I believe the incoming is conductors directly into the main lugs, so there should be nothing exposed from above.

I'll just have to be extra-careful to not drop anything.

We normally switch on the main, then the subpanels. Depending on the site, we may also require a tenant representative on site to ensure that critical loads have come up or off the transfer switch.

I will have the district manager, with whom I've already spoken, be sure to address these issues.

The legalities I cannot address. As for safe, so long as the entire panel is isolated and locked out, you should be OK. Check, then double check that the buss is dead before starting any work.

Absolutely, and always. Like Bob, I've found an open breaker not open. Non-contact as well as CAT-III solenoid tester.

If it helps, we've been using Schneider ION 6200 series meters for submetering.

I'm going with an E-Mon D-Mon 480/3200D, which I'm familiar with. I will remove both existing CT sets, install the new ones, and re-use the voltage tap points, making sure they're properly fused.

It's just weird to find that both existing meters have the same problem: no kwh. The number just stays the same on both. I will call E-Mon again before I start just to see if they have any ideas, but their tech support agreed with my plan.



Thanx! :smile:

 

[mxslick]

I know of a couple new apartment complexes here that include utilities in the tenants monthly bill, but each unit still has a meter from the poco.

Its a flat-rate charge, not actual usage.

If that's shown on their lease agreement as a fixed charge and not just included in the overall monthly rent, then that's illegal. The landlord would then be making profit on the light usage months. (For example, if the lease reads as Rent: $500/mo, Utilities $75/mo, then that's illegal. If the lease simply reads as Rent $575/mo, all utilities included, then that's legal.)

Amazing how changing a few words around makes something legal....

Overall I do find in strange that electric is charged by the landlord...every apt. I've ever rented doesn't include electric in the rent. (I have water, trash and sewer included in my current lease. One apt. I rented a while back also included gas.)

 

[iwire]

Here any new multi dwelling unit must have individual metering, no options. Existing installations can remain as they are.

Commercial it can be included or separate either by sub metering or POCO metering. But as has been said no profit allowed.

In many of the office buildings we work in there is one utility meter the rest are emon demons. You can network them together and have a PC monitor them all and produce documentation for billing. I am fairly certain EMON demons can handle demand billing as well.

 

[LarryFine]

Well, we're heading out now to do the replacement. If I never come back here again, you'll know I've gone to that great big switchgear in the sky!

As they used to say back in Old Mexico City, AMF!

Until we meet again,

 

[LazyS]

We did a Mall in Dallas last year. Each tenant had a seperate meter for billing and then each substation(5) of the mall had meters off the load side of buckets that fed busduct. The kwh weren't adding up so they had us install another meter on the main bus at each substation. I definitely would recommend that you kill power. We actually installed the split core ct's around each 4000amp bus energized and it was the most nerve racking thing I've done and I have done some stupid stuff. I would never let anyone do anything like that again. The ct's actually would vibrate in your hands until you got the wingnut tightened down good, which is difficult with 5kv gloves. There were horizontal and vertical bus live in front of me and I was wedged between the wall and the back of the gear putting these things on.DUMB,DUMB,DUMB. Just be careful,hope everything goes well. Losing your life is not worth a mall being able to charge a tenant a little more change. That is when I decided to go into business for myself, I had enough of doing stupid things to make someone else money. The contractor I had been with for 9 years didn't want to go through the hassle of having a shutdown and they knew I had the skill to do it as well as the lack of brains to act like it was a problem. I'll never forget the look on the first week helper's face when I showed him how to push the trip button if something happened but told him it would be to late anyways. Any hows that's my sob story