Attachment 6_Electric Narrative.pdf
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- Solicitation number
- 1240LU26Q0030
- Issued by
-
Department of Agriculture Forest Service
About this file
This document is a technical specification prepared by Morrison Maierle for electrical upgrades to the USFS Fort Missoula Brick Building. The existing electrical system consists of a 200A, 208Y/120V, 3-phase, 4-wire service fed by overhead utility transformers, with an exterior panel distributing power to Shop Panel P (100A, 3-pole), a Fuel Storage Panel (100A, 2-pole), and Irrigation Sprinklers (20A, 1-pole). Northwestern Energy data indicates a peak historical building load of 6.93kW (April 2023), calculating to 30.1A when normalized. Shop Panel P, fed by a 100A breaker with a 90A main breaker and only four available breaker spaces, cannot accommodate additional equipment.
The scope adds seven pieces of shop equipment requiring electrical connections: a 30A 3-phase lathe, 15A 3-phase end mill, 50A/220V MIG welder, 30A 3-phase TIG welder, 30A 3-phase plasma cutter, 30A/220V vehicle lift, and 20A 3-phase air compressor (existing). The connected load totals approximately 47kVA (130.5A), reducing to 29kVA (80.5A) with diversity factor, bringing total building load with diversity to 110.6A—remaining within the existing 200A service capacity. Required upgrades include: installing a 125A, 3-pole breaker in the existing exterior panel; providing a new 125A, 3-phase, 4-wire interior panelboard with 125A main breaker and 42 circuit spaces (NEMA 1 enclosure); installing appropriate breakers for new equipment; running a 2-inch conduit with four #1/0 and one #6 copper wires from exterior to interior panel; and providing receptacles or hardwire connections for equipment. The specification is dated April 10, 2026, and signed by P.E. Garth L. Stevens.
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USFS - Fort Missoula Brick Building
Electrical Upgrades
Fort Missoula Brick Building Electrical Upgrades
Existing Electrical System
The existing electrical service to the building consists of an overhead feed from pole-mount utility transformers to the south of the building. The service is 200A, 208Y/120V, 3-phase, 4-wire and feeds an exterior panel with three breakers:
• One 100A, 3-pole breaker feeds the shop Panel P inside the building
• One 100A, 2-pole breaker feeds a Fuel Storage Panel
• One 20A, 1-pole breaker feeds Irrigation Sprinklers
Northwestern Energy has indicated that the peak load for building over the last three years is
6.93kW in April of 2023. Assuming a power factor of 0.8 the math yields the following:
6.93kW divided by 0.8 pf equals 8.66kVA
8.66kVA multiplied by 125% equals 10.83kVA (per NEC 220.87)
10.83kVA divided by 208V, 3-phase equals 30.1A
Shop Panel P, fed by a 100A breaker in the outside panel, has a 90A main breaker. There are only four spaces for additional breakers in this panel, so it would not have room for the additional breakers required by the shop equipment listed below.
Added Electrical Loads
The following items are to be installed:
• Lathe — 30 amp 3ph
• End mill — 15 amp 3ph
• Mig welder — 50 amp/220V
• Tig Welder — 30 amp 3ph
• Plasma cutter — 30 amp 3ph
• Vehicle lift — 30 amp/220V
• Air Compressor (existing Catlin compressor) — 20 amp 3ph
For this additional equipment, we calculate a connected load of around 47kVA, which equates to 130.5A. When we take into consideration a diversity factor for the loads, since they won’t all run continuously or simultaneously, we get a load of around 29kVA, which equates to 80.5A.
Since the existing peak load only comes to 30.1A, the total load, with diversity, comes to 110.6A
USFS - Fort Missoula Brick Building
Electrical Upgrades and the existing 200A service will be sufficient. If other equipment is added, the loads would need to be recalculated.
Needed Electrical Upgrades
The following changes will be required to accommodate the added equipment.
• Provide an additional 125A, 3-pole breaker in the existing exterior panel.
• Provide a 125A, 3-phase, 4-wire panelboard inside the building with a 125A main breaker, 42 circuit spaces, and a NEMA 1 enclosure.
• Provide the appropriate breakers in the new panel for the new equipment loads.
• Provide a 2” conduit with (4) #1/0 and (1) #6 copper wires from the existing panel outside to the new panel in the building.
• Provide the appropriate receptacles or hardwire connections for the equipment.
Garth L. Stevens, P.E. Date gstevens GLS Signature gstevens Text Box April 10, 2026
File details come from the government source that posted it. Updated .