Main Switchgear Submeter

[United36]

Has anyone installed an electric submeter on main switch gear before? What is the best way to make the voltage connections to the meter? Usually I would find a small subpanel and put a 15 amp breaker in and use that to power the meter and supply the voltage feed. In this case all I have is the main switch gear. Can you tap off the main bus bar somehow and go to fuses?

Thanks!

 

[zog]

Has anyone installed an electric submeter on main switch gear before? What is the best way to make the voltage connections to the meter? Usually I would find a small subpanel and put a 15 amp breaker in and use that to power the meter and supply the voltage feed. In this case all I have is the main switch gear. Can you tap off the main bus bar somehow and go to fuses?

Thanks!

Just use the metering functions of the feeder breakers. Most modern switchgear will have breakers with that capability. Older stuff can be easily retrofitted.

 

[Steve O]

Has anyone installed an electric submeter on main switch gear before? What is the best way to make the voltage connections to the meter? Usually I would find a small subpanel and put a 15 amp breaker in and use that to power the meter and supply the voltage feed. In this case all I have is the main switch gear. Can you tap off the main bus bar somehow and go to fuses?

Thanks!

In your case I would tap and fuse off of a smaller feeder breaker in the switch gear so you can comply with NEC 240.21 tap rule. There are no other cost effective options to legally tap larger switch gear main bus bars for such small devices.

 

[ohmhead]

Voltage to meter

Voltage to meter

Example three phase 4 wire system to a meter in swbd added.

Say Square D we add a small brk in swbd say 15 amp and usally the meter package comes with internal fuses or 5 amp brk factory installed.

We always install meter power in metered switchboard just because we old and gray !



If its three phase Y 4 wire it needs V1 V2 V3 VN and this runs to sub meter also CT wires C1 C2 C3 CN usally if its less then 600 volts today you dont need PT for voltage to meters or meter.

What meter type & system are you installing volts amps phase ?


You must protect wiring to meter if you tap it brk fuse block what ever !

 

[ron]

If it is a power quality meter, you want a solid connection to the incoming feeder.
Try to use a ring terminal attached to one of the existing bolts.
If there are no accessible bolts, use an compression H-Tap to the smallest tap conductor available (I think #2), then terminate in a fuse block to reduce to the final sense wire size going to the meter.

 

[ron]

Just use the metering functions of the feeder breakers. Most modern switchgear will have breakers with that capability. Older stuff can be easily retrofitted.

Zog,
Just as an application note: I've had accuracy issues with the meters on the breaker trip units. I've often needed tighter tolerances then the trip unit provided.

 

[zog]

Zog,
Just as an application note: I've had accuracy issues with the meters on the breaker trip units. I've often needed tighter tolerances then the trip unit provided.

Depends on the application I suppose, and the trip unit.

 

[United36]

What do you mean by "metering functions of the feeder breakers". This is a 4000 amp 480 volt service. The smallest breaker in the switch gear is 200 amps.

Thanks!

 

[zog]

What do you mean by "metering functions of the feeder breakers". This is a 4000 amp 480 volt service. The smallest breaker in the switch gear is 200 amps.

Thanks!

What type of breaker and trip unit is it?

 

[United36]

Very Similar to this attached picture.

 

[zog]

Very Similar to this attached picture.

View attachment 5350

That is not a breaker, that is a bolted pressure switch, sorry, there won't be anything on board, someone was looking for cost savings when they designed that one.

 

[ohmhead]

Well with a Square D -HDM sub meter you can tap that main with 4 amp fuses in a fuse block inside that main switch section install split core CT ,s around that buss and have a watt meter on the wall or mounted to that switchgear within hours . Look at powerlogic sub metering SD has it all and with the software and a cable or two you can read your watts / vars/ volts /amps in your car driving home .

 

[zog]

Well with a Square D -HDM sub meter you can tap that main with 4 amp fuses in a fuse block inside that main switch section install split core CT ,s around that buss and have a watt meter on the wall or mounted to that switchgear within hours . Look at powerlogic sub metering SD has it all and with the software and a cable or two you can read your watts / vars/ volts /amps in your car driving home .

Yep, I second that, the powerlogic line is good stuff.

 

[Steve O]

Well with a Square D -HDM sub meter you can tap that main with 4 amp fuses in a fuse block inside that main switch section install split core CT ,s around that buss and have a watt meter on the wall or mounted to that switchgear within hours . Look at powerlogic sub metering SD has it all and with the software and a cable or two you can read your watts / vars/ volts /amps in your car driving home .

This is where I have run into "field install" issues in the past regarding taps for metering and surge suppression. NEC's tap rule applies when tapping this 1600A main with anything less than a 2/0 conductor within 10' and fusing at such a small amperage isn't easily accomplished.

We see it done from the factory as a listed assembly with #10 AWG switchboard wire to 30A rated fuse block but discussions with both meter and SPD vendor application engineers, this field install must meet with NEC 240.21.

If someone has found a loophole or work around for this I would be glad to hear it.

Thanks

 

[ohmhead]

Well actual you do not have to get your power from that main section if thats a issue the meter will work from a down stream breaker as long as A phase b phase and c phase is matching current and voltage abcn meaning v1 c1 v2 c2 v3 c3 and you must have a neutral if used .

Sorry i cant help with your issue call the company who makes the gear and ask them they will have a better solution but that gear is kinda 25 yr old so they wont put it down in writing for you .

 

[JoshL]

Sq-D has a services division that I believe could field install a Powerlogic unit using the #10 switchboard wire (avoiding the tap rule issue) and it would be considered UL Listed when done. Not sure if they can do it in other manufacturer's gear, but I am pretty sure they can do it for their own gear. It would be worth a call to to them to ask.

 

[United36]

I read up on NEC 240.21. If I understand it correctly then I could install a fuse block or fuseable disconnect on the main service (<10 ft from main conductors). I could run taps rated for the meter device from the mains to this fuse block and then from the fuseblock to my meter device. It seems this would meet NEC 240.21 if I understand it correctly. If that is true, I still don't understand how you "tap the main conductors". In this case the main condutors are solid bus bar right.

There was a suggestion to tap a smaller breaker and use ring terminals on the bolts. Would that meet the requirements of 240.21?

Thanks!

 

[Steve O]

yes, you are on the right track to meet the tap rule.

The reason I mentioned earlier in the thread to locate a smaller feeder breaker, was to keep your tap size down.

For example if you have a 300A feeder breaker in the gear you could tap the load bus with lugs and run no more than 10' of #10AWG to a 30A rated touchless (what I use) fuse block mounted on din rail, with three KTK 2, 3, or 4 amp midget fuses.

I am without my code book at the moment but I believe the 10' tap rule states the tap conductor current rating cannot be less than 10 times the current rating of the tap source you will comply.

This method has it downside. If the 300A breaker is off for a reason of course you lose your meter power and voltage inputs.

Hope this helps.

 

[ohmhead]

Well to tap the buss bar and iam not telling you to do this without asking your engineer or factory gear rep but you C crimp the tapped phase and neutral bars with a buss bar C crimp .

It attaches to the buss bars with a hypress crimp tool and it will never come off ever you can get these for any bar size and just about any wire size.

Its kinda like a H crimp but just one sided and you crimp your wire also with this .

Burndy might be your link here but this must be approved by others first its safe and we do it on some jobs if needed .

 

[United36]

Part of 240.21 says "(4) For field installations where the tap conductors leave the enclosure or vault in which the tap is made, the rating of the overcurrent device on the line side of the tap conductors shall not exceed 10 times the ampacity of the tap conductor."

Can someone please interpret this with and example. Is the 'overcurrent device on the line side of the tap condutor" my new fuse block or the overcurrent device of the main condutors?

Thanks!