Amperage on the Panel

[girl]

Guys please help, I was asked to measure amperage on the Distribution Panel. I did measure amperage on each phase on each 3 phase disconnect switch.
I did not have "proper" instruments to measure pick load amperage for 24 hours, I just took my Clamp Amprobe and measured each wire on each 3 phase disconnect.
Do I add all readings together from each wire from each disconnect and say total amperage of this Distribution Panel is such and such, or what...?

Thank you all

 

[ptonsparky]

Best would have been to measure current of the feeder to the mdp. You will have to assume that the A phase of each disconnect originates from the A phase, etc. Yes, add all 'A' phase currents. Add 'B'. Add 'C'. Pretty rough estimate because some of the load may not be on. Do not add A+B+C.

 

[Dennis Alwon]

If you use an amp meter on all three phases then the highest load is what you would use not the addition of all three. I would make sure all a/c units are running and any other equipment that would add to the load.

 

[nakulak]

just FYI, even a lowly fluke 1587 has a min/max button that will record minimum and max values so you can come back and review it (without having to buy or rent an expensive power analyzer)

 

[girl]

Guys all of you are great and I do thank you You.
On the particular Distribution Panel which is 400 Amps and 120/208 Volts there is a Spare space for an additional disconnect, and BIG Boss wants to know can this DP handle that extra disconnect where the Spare space is. That's why they wanted me to measure amperage on DP.
Example:
Disconnect N1K: phase A=12 Amps
B= 9 Amps
C= 13 Amps

Disconnect H1L: phase A=29 Amps
B=31 Amps
C=30 Amps

Disconnect D1C: phase A= ...
B=..
and so on

I measured all phases on all disconnects, now to add them up and tell my Boss for example Total amps are; 371 Amps,

is it how I should do?

Thank you all

 

[Dennis Alwon]

If you have a 400 amp MDP then each phase is capable of 400 amps. Add up all the "A" phases, then add the "B" and then the "C" . The largest phase is what your load will be based on the meter reading at that time. You do not add phases A + B + C together.

 

[bob]

Example:
Disconnect N1K: phase A=12 Amps
B= 9 Amps
C= 13 Amps

Disconnect H1L: phase A=29 Amps
B=31 Amps
C=30 Amps

Disconnect D1C: phase A= ...
B=..
and so on

I measured all phases on all disconnects, now to add them up and tell my Boss for example Total amps are; 371 Amps,

is it how I should do?

Thank you all

It does not sound like you have it correct. From the figures you show
phase A = 12 + 29 = 41
Phase B = 9 + 31 = 40
Phase C = 13 + 30 = 43
If this were the total load, then the max load would be 43 amps and not
41 + 40 + 43 = 124.

 

[girl]

Very, very good I am going to do it that way.
Thank you so much.

I am so happy for your help.

Best wishes

 

[mxslick]

It does not sound like you have it correct. From the figures you show
phase A = 12 + 29 = 41
Phase B = 9 + 31 = 40
Phase C = 13 + 30 = 43
If this were the total load, then the max load would be 43 amps and not
41 + 40 + 43 = 124.

Bob. look again, she just gave the first 2 disconnects' readings.

<snip>
Disconnect N1K: phase A=12 Amps
B= 9 Amps
C= 13 Amps

Disconnect H1L: phase A=29 Amps
B=31 Amps
C=30 Amps

Disconnect D1C: phase A= ...
B=..
and so on

 

[bob]

Bob. look again, she just gave the first 2 disconnects' readings.

It does not sound like you have it correct. From the figures you show
phase A = 12 + 29 = 41
Phase B = 9 + 31 = 40
Phase C = 13 + 30 = 43
If this were the total load, then the max load would be 43 amps and not
41 + 40 + 43 = 124.

I said "if this were the total load". I know it was only a partial load reading. She did not seem to understand how the
phase loads were added together. Does that answer your question?

 

[IamJonscranium]

Maybe I'm missing something... are the currents of each branch circuit being measured? If so, why not just measure the current of each of the 3 main busses?

Then determine which phases the new circuit will use (need to know: 1ph 120, 1ph 208, or 3ph 208). Then add the FLA of the new device to the existing load of the used phase bus(ses).

 

[ptonsparky]

Maybe I'm missing something... are the currents of each branch circuit being measured? If so, why not just measure the current of each of the 3 main busses?

Then determine which phases the new circuit will use (need to know: 1ph 120, 1ph 208, or 3ph 208). Then add the FLA of the new device to the existing load of the used phase bus(ses).

No your not missing anything, that is what should have been done, but for whatever reason did not. Girl may not have had the skills or equipment...we don't know.

 

[SG-1]

Maybe I'm missing something... are the currents of each branch circuit being measured? If so, why not just measure the current of each of the 3 main busses?

Then determine which phases the new circuit will use (need to know: 1ph 120, 1ph 208, or 3ph 208). Then add the FLA of the new device to the existing load of the used phase bus(ses).

All the loads may not be on together all the time, so if you measured the mains you could miss a load or two. By measuring all the branch circuits you would be less likely to miss a load.

 

[LEO2854]

All the loads may not be on together all the time, so if you measured the mains you could miss a load or two. By measuring all the branch circuits you would be less likely to miss a load.

If you mesure at the mains with all the loads on you will get an accurate mesurment:grin: