Disaster_Warehouse_Electrical_Survey.pdf

AEC Ashford Electric & Construction Co.

Certified WBE/DBE • D2F2604453

January 23, 2013 VIA E-mail

FEMA

Bothell, WA

RE: Warehouse Load Calculation

ATTN: Brian (425) 487-4731

Hi Brian, Using section 220 of the NEC we have calculated the minimum feeder required for the new warehouse to be 70 Amps at 120/208V 3 Phase. The following values were used for this calculation. A VA(Volt Amp) is the same as a watt for this calculation.

Lighting (15) fixtures x 216Watts each + 200 Watt Outdoor 3440 VA Heating (2) 5KW heaters 10,000 VA Receptacles (50) Laptops 100Watts Each + 17 * 180 Watts 8060 VA UPS (1) 700 Watts 700 VA Extra Large Load 20A(1) 20A * 120V = 2400VA 2400VA

TOTAL VA 24,600 VA

208V 3Phase Amps (24,600VA) / (208V) (1.732) = 68.28 Amps

The receptacle loads where based on the 50 laptops with 100 Watt power supplies and 17 remaining receptacles at 180 watts each. The 180 watts per receptacle is per section 220 of the

NEC.

This new load is too large to be connected to the first existing transformer. The first transformer in the existing warehouse building is a 30 KVA 480V -120/208V 3 phase transformer with a secondary 120/208V current capacity of 83 Amps. This transformer feeds a panel next to it (Panel 1 on the One Line diagram). The load measured on this panel was about 37 Amps per phase with 3 heaters on and the lights on. This load in VA is 13,320.

The second transformer is a group of 3 15KVA transformers that provide a total of 45KVA and have a secondary 120/240V current capacity of 108 Amps. These transformers feed a panel below them (Panel #2 on the One Line Diagram) with a 125A main. The loads measured on this panel were Phase A 27Amps, Phase B 15A and Phase C 19A. This panel feeds the Department of Justice, and an irrigation pump, and it is unknown which equipment was running at the time.

The measured load in VA is7320 VA.

Cont. #ASHFOEC 147QC • 909 Kirkland Avenue • Kirkland, WA. 98033

(425) 889-1486 • (425) 828-9045 amorea Typewritten Text Document#: FWP6

Cont. #ASHFOEC 147QC • 909 Kirkland Avenue • Kirkland, WA. 98033

(425) 889-1486 • (425) 828-9045

AEC Ashford Electric & Construction Co.

Certified WBE/DBE • D2F2604453

It appears that the existing feeder from the 480V PUD transformer is large enough to support the new warehouse load, which presents some of the following options to feed the new wharehouse.

1.) Connect the new warehouse load to panel #2. With the measured load on the panel and the size of the transformer there appears to be enough capacity to supply the warehouse. The disadvantages of this option are that the actual load on the panel is unknown. The department of justice is fed with a 2 Pole 100 Amp breaker, so there total load could be up near 100Amps on 2 of the phases. Also the panel appears to be 120/240V, with some transformer setups this could produce a phase that is unusable at 120V, and since the new warehouse loads are all 120V except for the heating, the capacity of the panel may end up being less than it appears.

2.) Replace the transformer #1 with a 45KVA transformer or larger and change the main breaker in the 120/208 panel to 125 Amps and feed the warehouse from panel #1. This would provide 120/208V 3 phase power to the new warehouse building.

3.) Install a new 480V disconnect or panel and feed the new warehouse building with 480V. A transformer would be installed either inside or outside the new warehouse building to provide the 120/208V power. The heaters could be 480V if desired and the wire and conduit size to the building could be smaller.

We would recommend option #2 for its simplicity and since we can verify the existing load on the panel.

Other Observations:

When we removed the cover to the 45A disconnect, we noticed that the feeder from the PUD transformer is not connected directly to the disconnect, and it is not the main service disconnect.

The feeder from the transformer is routed through the disconnect to an adjacent junction box where it is tapped to feed the disconnect for the second transformer, the feeder then contnues back into the 45A disconnect and attaches to the breaker. This violates the electrical code since the disconnect enclosure is used as a raceway to the junction box. Also there is not a neutral wire pulled in from the PUD transformer. If the PUD transformer has a neutral, the code requires it be installed with the other phase conductors and bonded at the service entry point. If the PUD transformer does not have a neutral than it is not required. We would suggest that the feeder from the PUD transformer should enter the junction box first, or change the 45 Amp disconnect to 100A Main disconnect and install a 45Amp disconnect for the transformer #1.

The system currently does not have a main disconnect. Another option would be to install a 480V panelboard with a main and feed both transformers from the panelboard.