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edge-data-center-main-OPEN/solar-array-ground-based-post-mount-system-for-colorado-wind-and-snow-loads.md
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Solar Array Ground-Based Post Mount System For Colorado Wind and Snow Loads

Table of Contents

Overview

One solar panel per below; 18-panels/installations total. The panel mount system in this document is designed for the specific panels identified below. Once panels are identified, give their size and weight to AI along with this document as a model to output the new loads.

Design criteria: https://www.douglas.co.us/building-division/design-information/

Mounting System Overview

  • Vertical Post: 2" Schedule 40 galvanized steel pipe (2.375" OD)
  • Horizontal Cross Beam: 2" Schedule 40 galvanized steel pipe (2.375" OD)
  • Connection: Single-socket tee (Kee Klamp model 10-9 galvanized) joining vertical and horizontal members using provided set screws
  • Spars: Four 2" wide × 0.25" thick flat steel bars non-galvanized (~44" long) attached to the horizontal cross beam using U-bolts and set bolts
  • 1.5 inch tubing pieces between the spars and the panels to provide greater gap between panel and spars and steel pipes
  • Solar Panel: Trina TSM-NEG19RC.20, dimensions 44.65" (height) × 93.78" (width), mounted in landscape orientation along the 93.78" edge
  • Adjustability: Panel tilt is manually adjusted several times per year for seasonal optimization by loosening set screws and changing tilt position before resetting screws
  • Paint: DTM paint on entire structure except kee klamp

Dead Load Total

Component Weight (lb)
Vertical post 32.85
Horizontal cross beam 28.54
Spars (2) 12.46
Kee Klamp 2
Hardware 2
Solar panel 72
Total ~149.85 lb

Wind Load Design (115 mph exposure)

  • Design Wind Speed: 115 mph (per local code)
  • Calculated Wind Pressure: 33.86 psf (equivalent to 1,621 Pa)
  • Panel Area: 29.08 ft²
  • Total Wind Force: ~948.6 lbs
  • Worst-Case Tilt Angle: 60°
  • Wind Moment (at 60° tilt): ~1,568 lb-ft

Structural Load Capacity and Safety Margins

  • Vertical Pipe (2" Sch 40): Capacity ~3,420 lb-ft → Safety Factor: ~2.2×
  • Kee Klamp (size 9): Axial load capacity 2,000 lbs per set screw → Safety Factor: ~2× See PDF from kee klamp showing load capacity
  • Panel Wind Rating: 2,400 Pa (per Trina datasheet) → Safety Factor: ~1.48×

Concrete Footing

  • Footing Dimensions: 12" diameter × 36" deep
  • Concrete Volume: ~2.36 ft³ (~340 lbs of concrete)
  • Soil Type: Sandy loam
  • Calculated Resisting Moment: ~2,404 lb-ft → Safety Factor: ~1.53×

Snow Load Design (35 psf, no reductions per County)

Snow load is applied to the horizontal projection of the tilted panel:

  • p=35cosθ psf

For the 93.78" × 44.65" panel (29.08 ft² plan area), this gives:

Tilt (θ) Projected Load (psf) Total Snow Load (lb) Cross-Beam Moment (lb-ft) Bending Stress (ksi)
60° (winter) 17.5 ~509 ~994 ~21.3
40° (spring) 26.8 ~780 ~1,523 ~32.6
  • Panel centroid is directly above vertical post → snow load acts in compression, producing negligible overturning on the post and footing.
  • Cross-beam (2" Sch 40) sees bending from snow as two equal cantilevers (each 46.9"), resulting in the above moments and stresses.
  • Both cases are within the 35 ksi yield strength of A53 Grade B steel, satisfying code compliance for snow load.

Wind governs bending in the post and footing; snow governs compression.

Code reference: Douglas County Design Information — “Ground Snow Load = Roof Snow Load = 35 psf; reductions not allowed.” Snow load is applied to the horizontal projection of the array.

Combined Load Cases (ASCE 7 service-level, centroid over post)

Given

  • County snow load (no reductions): 35 psf.
  • Snow acts on the horizontal projection: p(θ)=35cosθ psf.
  • Operating tilts considered: 60° (winter), 40° (spring).
  • Panel plan area: 29.08 ft².
  • Wind (Exposure C, <7000 ft): 115 mph, previously computed base wind moment MW=1,568 lb-ftMW​=1,568 lb-ft at 60° tilt.
  • Geometry: panel centroid is directly above the post → snow and dead load act axially (compression) in the post/footing (negligible overturning from vertical loads).
  • Cross-beam: 2" Sch 40 pipe (OD 2.375″, S≈0.561 in3S≈0.561 in3).

A) Post & Footing (governing lateral = Wind)

Because snow and dead load are concentric with the post, the base overturning is governed by wind.

  • D + W (60°): Mbase≈1,568 lb-ftMbase​≈1,568 lb-ft (wind) – Post bending SF: 3420/1568≈2.18×3420/1568≈2.18× – Footing overturning SF: 2404/1568≈1.53×2404/1568≈1.53×
  • D + 0.75 S + 0.75 W: Snow contributes compression only; overturning is still driven by 0.75 W. Mbase≈0.75×1,568=1,176 lb-ftMbase​≈0.75×1,568=1,176 lb-ft – SFs increase relative to the D + W case above.

Conclusion (post/footing): Wind at 60° remains the governing case; factors of safety are unchanged from your wind section and meet requirements.

Structure Design And Measurements

https://lucid.app/publicSegments/view/f104d7af-6f8b-4ba8-9f67-55c54bdf8c2f/image.pdf

Electrical, Grounding, Lightning, and Interconnection Details

Array Configuration Overview

  • Total panels: 18
  • Configuration:
    • Two strings of 9 panels
    • Panels wired in series per string
  • All array-side wiring and grounding originates at the panel rows and converges at DC disconnects before transitioning to the main panel area.

Panel-Level Wiring

  • PV Wire
    • 10-gauge exterior-rated photovoltaic wire
    • Series connections between panels
  • Conduit Between Panels
    • ½-inch metal conduit
    • Buried approximately 9 inches
    • Runs between adjacent panels for series interconnection
  • Conduit Terminations
    • Non-sharp conduit end fittings installed at all exits
    • Prevents insulation abrasion and cable damage

Panel Grounding

  • Panel Ground Conductors
    • 8-gauge stranded bare copper
  • Ground Lugs
    • Approved aluminum-to-copper grounding lugs
    • Used at each aluminum panel frame connection
  • Row Grounding
    • 10-gauge bare copper ground wire
    • Runs the full length of each panel row
  • Integration
    • Panel row grounds are bonded into the site grounding and lightning protection system

Lightning Protection System

  • Lightning Rods
    • Quantity: 4
    • Each rod: 8-foot copper air terminal
    • Mounted to standard steel fence posts
    • Fence posts set in concrete
  • Down Conductors
    • 2-gauge bare stranded copper
    • Two conductors per lightning rod
      • One routed in each direction
  • Ground Rods
    • Quantity: 6
    • All rods bonded together underground
  • Interconnection
    • Ground rods interconnected using 2-gauge bare solid copper
    • Panel grounding system bonded into lightning ground network
  • Installation Practices
    • No sharp bends in lightning conductors
    • All connections made using dedicated ground lugs
  • Ground Rod Access
    • Each ground rod protected by ~6-inch PVC riser
    • Risers painted for visibility and inspection access

DC Disconnects at Array

  • Disconnect Type
    • Siemens DC blade disconnect boxes
  • Configuration
    • One disconnect per 9-panel string
  • Functions
    • String isolation
    • Ground termination
    • Transition point to long-run conduit
  • Surge Protection
    • 600-volt DC surge protectors installed at each disconnect

EMI / Noise Suppression

  • Ferrite Cores
    • Iron ferrites installed on PV conductors
    • Two ferrites per panel (positive and negative)
  • Purpose
    • Reduce electromagnetic interference
    • Additional protection for inverter electronics

Main Array-to-Panel Conduit Runs

  • Primary Conductors
    • 8-gauge copper (THWN)
  • Conduit
    • 2-inch electrical conduit schedule 80 pvc
    • Continuous run from DC disconnects to main panel area
  • Routing
    • First DC disconnect → second DC disconnect → main panel area
  • Depth
    • Buried 2 feet
  • Runs
    • 6 total wires (3 runs)
    • 2 used now
    • 3rd is spare for future expansion, terminated at second/east underground 4x4 conduit box before hitting DC disconnect switch

Auxiliary / Spare Underground Wiring

  • Direct Burial Cable
    • Southwire-type 3-conductor direct burial
  • Usage
    • Center conductor used as ground
    • Two unused conductors retained for future telemetry or expansion
  • Spare Capacity
    • Three full array-to-panel runs installed:
      • Two active
      • One spare, dead-ended for future use
  • Termination
    • Spare conductors terminated in underground junction box

Junction Boxes

  • Underground junction boxes installed:
    • At each Siemens DC disconnect
    • At array exit points
  • Allows:
    • Directional routing changes
    • Future expansion or servicing
  • Main transition box near panel area:
    • 4" × 4" non-metallic enclosure
    • Receives all array conduits

Transition to Inverter

  • 8x8 enclosure at floor connecting ground conduit, and holding third spare run for future expansion
  • Conductor Reduction
    • 8-gauge transitioned to 10-gauge using approved connectors
  • Surge Protection
    • Additional 600-volt surge protectors installed at inverter input
  • Inverter
    • Sol-Ark inverter
    • Electrical specifications documented separately in inverter documentation

Grid Reference, AC Output and Main Panel Connection

  • Load Side Output
    • Sol-Ark → 100-amp AC blade disconnect
    • Then → 45-amp breaker box
    • Then → 45-amp breaker in main panel
    • note: neutral bypasses 100-amp AC blade disconnect and is wired directly so that neutral throughout the system is never compromised if AC disconnect is in open position
  • Conductor Size
    • All AC wiring in panel area: 6-gauge
    • Includes:
      • Line conductors
      • Neutral
      • Ground

Grounding at Main Panel Area

  • Grounds routed into dedicated 4" × 4" junction box
  • Unused conductors trimmed
  • Ground conductor bonded into main panel grounding system
  • All grounding compliant with continuous bonding principles

Telemetry and Monitoring

  • Telemetry Wiring
    • 16-gauge-22 guage
    • Installed in conduit
  • CT Clamps
    • Installed on main supply-side conductors
    • Feed telemetry data to Sol-Ark inverter
  • Enables production and consumption monitoring

Internal Notes

https://docs.example.invalid/private-reference

https://docs.example.invalid/private-reference

https://lucid.app/lucidchart/3fa74ac3-87e8-48f5-9cf8-7a0aab1e5572/edit?invitationId=inv_9237ab8b-90ad-4f51-b690-d56d92ae5226&page=knY35NawKQxu#

Site Map

https://lucid.app/publicSegments/view/51abe54f-5063-4495-837f-abe87d304c16/image.jpeg

1-Line

Tag New or Existing Segment Description Min. Wire Size # of Conductors Conductor Type Raceway Type Min. Conduit Size Conduit Length
A New PV Array Ground Based #10 AWG 2 RHW-2 Metal 1/2" ~85'
B New 60 Amp 600-Volt 3-Pole Outdoor Non-Fusible Safety Switch + SPD #10 AWG 2 RHW-2 na
B New PV Array to Sol-Ark Inverter 12K (DC) #8 AWG Copper, converting to #10 just before inverter to accomodate inverter max wire size; #12 ground wire 4 & 2 THWN-2 Schedule 80 PVC 2" 222' & 242'
B New 60 Amp 600-Volt 3-Pole Outdoor Non-Fusible Safety Switch + SPD #10 AWG 2 RHW-2 na
C New Sol-Ark Inverter (Grid connectors) through blade disconnect and through 45 amp breaker/junction box #6 AWG copper 4 THWN-2 LiquidTight PVC 1" 5'
D Existing Main Panel (225 A) to Manual Transfer Switch (Interlock) 225 A Breaker Previously installed with new main panel
E Existing Generator Inlet
H New 100 Amp AC Blade Disconnect #6 AWG copper 4 THWN-2 LiquidTight PVC 1"
F Existing AC Disconnect (225 A Breaker) to Utility Meter Previously installed with new main panel LiquidTight PVC
G New CT Clamps For Sol-Ark Monitoring 16 AWG Twisted Pair 2 LiquidTight PVC 1/2" 6'
New Lightening Protection #2 AWG copper: 2 lines from lightening rods, one to each side to ground conductor. #2 AWG copper buried connecting all ground rods
1" 6

https://lucid.app/publicSegments/view/22451edb-4c40-4d5f-b1c0-389fc6427e4f/image.jpeg

Panel Configuration

https://lucid.app/publicSegments/view/f9d62377-a9b2-4a4f-9df2-9a91dfa010a9/image.jpeg

Calibration of Tilt

Nov 5 - Jan 5: 20 Degrees

Jan 5 - Mar 5: 40 degrees

Mar 5 - May 5: 60 Degrees

May 5 - Jul 5: 80 degrees

Jul 5 - Sep 5: 50 degrees

Sept 5 - Nov 5: 40 degrees

Maintenance

Washing Panels

Thermal shock risk (real, but manageable)

Spraying cold water on hot glass can cause micro-fractures over time, especially:

  • Midday summer sun
  • Very cold water (well water, hose from shade)
  • Older panels

Best practice

  • Best: early morning or late evening
  • Acceptable: overcast days
  • Avoid: hot panels + cold hose water at noon

Technique

  • Use low pressure
  • Let water run gently, don’t blast
  • Soft brush only if needed (pollen, bird droppings)
  • No detergents unless panel-approved

Check individual panel production

The array string will step down to lowest producing panel. Minimum viable monitoring

  • Monthly: string-level comparison - check with voltage meter each string
  • After storms: visual + production check
  • As needed, check individual panel output to identify weakest panel and replace if it steps down a lot.

Visual inspection checklist

  • Cracked glass
  • Browning / snail trails
  • Loose clamps
  • Cable insulation UV damage
  • Grounding continuity - use voltage meter

Snow

  • steeper winter angles already help
  • If clearing: soft roof rake only

Torque & structure

  • Check bolt torque annually
  • Ground mounts move with freeze/thaw cycles

Grounding

  • Inspect bonding jumpers yearly
  • Check for corrosion at earth connections

Hail Protection

Panels are tougher than people think. Modern panels are typically tested to:

  • 25 mm (1 in) ice at ~50 mph
  • Many survive larger hail, but Colorado storms can exceed test cases.

For days with higher risk of hail greater than 1-inch diameter, we fasten to panels a 1.5 inch rigid foam board 8 ft x 4 ft using spring clamps. They are stored in a large wood box we built at the array. The foam is lightweight to easily place on panels and absorbs and spreads the hail strikes, whereas a wood panel is heavy, hard to handle and hail strikes can transfer impact damage through the wood on the panel because it is not designed to absorb shocks like the foam boards.

Operations

System work mode

  • max solar = 12000
  • zero export power = 500
  • max sell power = 8500 (higher and get fault events, likely because utility will not accept higher load to them)