3 Phase Panel Calculation

[Biogas Sparky]

Hi everyone.

I have been working on this calculation for a few days and am curious if it have it correct, so any help would be greatly appreciated.

We have a system that we are designing/ building for biogas clean up. This system is mostly motors that come as pre-assembled systems. For example, one system has a 200hp, 10hp, 7.5hp, and 1/2hp 3phase 480 volt motors, the manufacture supplies the control enclosure for all these with the 200hp VFD controlled. All the motors for the whole system are continuous and run simultaneously.

Here is the calc chart that I put together for this. I hope this makes sense. I multiplied the largest motor by 1.25 in the VA column and then the total VA by 1.25 as it is all continuous load that I know of currently (I will adjust if anything is not continuous)

Thanks in advance for the help.

Main Equipment	Equipment Loads	HP	FLA	Volts	Multiplier	va
Intake Blower Skid
	Blower	20	27	480	1.732	22446.72
	AA	2	3.4	480	1.732	2826.624
Feed Gas Compressor 1				480		0
	Screw Compressor	200	240	480	1.732*1.25 for largest motor	249408
	Gas Cooler	10	14	480	1.732	11639.04
	Oil Cooler	7.5	11	480	1.732	9144.96
	Condensate Pump	1/2	1.1	480	1.732	914.496
Product Gas Compressor				480		0
	Compressor	50	65	480	1.732	54038.4
	Cooler	5	7.6	480	1.732	6318.336
	Pre lube		1.8	480	1.732	1496.448
	Oil Heater		1.8	480	1.732	1496.448
Chiller				480		0
	Potential		50	480	1.732	41568
Transformer 1	25 kva		52	480	1	24960
	DCP1			120		0
	Heat Trace			120		0
	UPS/ Network			120		0
	Exterior Lights			120		0
	Gen Recp (1)			120		0
						0
						0
						0
O2 Container						0
	Compressor	25	34	480	1.732	28266.24
	Transformer 10kva		20	480	1	9600
		Totals FLA	585.1			464123.712
					Total VA/ 831	558.5122888
		Total FLA *1.25 for continuous load	731 amps		Total VA/831*1.25 for continuous load	698 amps

 

[PD1972]

Couple of notes:

1. Get rid of your total FLA calculations as it is unnecessary. Many times, the number a "total FLA" calculation yields is wrong unless all your loads are the same voltage and phase. The important column is the total VA which you have.
2. I notice that your VA for transformers is strangely close to the rating of the transformer. This leads me to believe you do not know the actual total connected load of each of those transformers. Are those transformers single phase or three phase? I have a feeling transformer 1 is a 480V delta to 208Y/120V transformer, which is a three phase load (so you need to fix the FLAs). If it's 480V to 120/240V single phase then there is nothing wrong. This isn't a huge issue as the VA is the same, but I can't help but comment as there is potential for your FLA to be incorrect.
3. You do not have to double dip on the 125% continuous factor for motor loads. The 125% of your largest motor load then everything else at 100% is sufficient per 430.24, which separates motor loads from non-continuous non-motor loads and continuous non-motor loads. Refer to how example D3(a) in annex D handles motor loads in a calculation.
4. It appears that motors make up a majority of the loads. Make sure that your panelboard upstream OCPD (ie, your motor feeder short circuit and ground-fault protection) meets the requirements of 430.63(3).

 

[Biogas Sparky]

Thank you kindly. This is incredibly helpful.

For note 2. These are single phase transformers that I did not do a complete load calculation on yet as we are still defining some of the components.

I have gone through the sheet and updated per the continuous/ non-continuous loads as you described above.

From what I understand on 430.63(3) I just need to make sure that the main CB OCPD for this panel needs to be larger than the largest branch circuit breaker (that being the feed gas compressor)

Main Equipment	Equipment Loads	HP	FLA	Volts	Multiplier	VA	Phase A	Phase B	Phase C
Intake Blower Skid
	Blower	20	27	480	1.732	22446.72	7482.24	7482.24	7482.24
	AA	2	3.4	480	1.732	2826.624	942.208	942.208	942.208
Feed Gas Compressor 1				480
	Screw Compressor	200	240	480	1.732	249408	83136	83136	83136
	Gas Cooler	10	14	480	1.732	11639.04	3879.68	3879.68	3879.68
	Oil Cooler	7.5	11	480	1.732	9144.96	3048.32	3048.32	3048.32
	Condensate Pump	1/2	1.1	480	1.732	914.496	304.832	304.832	304.832
Product Gas Compressor				480
	Compressor	50	65	480	1.732	54038.4	18012.8	18012.8	18012.8
	Cooler	5	7.6	480	1.732	6318.336	2106.112	2106.112	2106.112
	Pre lube		1.8	480	1.732	1496.448	498.816	498.816	498.816
	Oil Heater		1.8	480	1.732	1496.448	498.816	498.816	498.816
Chiller				480
	Potential		60	480	1.732	49881.6	16627.2	16627.2	16627.2
Transformer 1	25 kva		52	480		24960		8320	8320
O2 Container				120
	Compressor	25	34	480	1.732	28266.24	9422.08	9422.08	9422.08
	Transformer 7.5kva		15.625	480		7500	2500		2500
Interment Air
	Compressor	7.5	11	480	1.732	9144.96	3048.32	3048.32	3048.32
					Total Non-continuous VA	437877.312	145959.104	145959.104	145959.104
					Total Continuous VA *1.25	40575	3125	10400	13525
					Total VA/ 831	575.7548881	179.4032539	188.1577665	191.918296
					Main Breaker	600a

 

[SSDriver]

The manufacturer of the enclosure might have done most of this for you ifs its a single enclosure. A ul508 enclosure should have calculated the entire load that is being controlled by the enclosure and accounted for the largest motor.