31C-046, 38A-104 Village Hill 1004142 Solar PV array loads MA 10-19-10
WWW.RELIABLETRUSS.COM
200 WELBY ROAD • NEW BEDFORD, MA 02745
508-99-TRUSS (87877) • 888-80-TRUSS (87877)
FAX 508-995-1724
- 1 -
October 19, 2010
R.K. Miles-Hatfield
24 West St.
Hatfield, MA 01038
Re: Village Hill Cluster A (46, 48, 50 & 52 Oleander Drive, Northampton, MA)
Reliable Job #0909267
Village Hill Cluster B (2, 4, 6, & 8 Moser Drive, Northampton, MA)
Reliable Job #1004142
To Whom It May Concern:
It is our understanding that roof mounted solar arrays per the attached dead weight loading
calculation sheet are being installed flush to the top chord of the main trusses on the above jobs.
We understand that each array module is supported by two rails running perpendicular to the
supporting trusses. The rails are fastened to each truss top chord with a fastener held by a single
lag screw. Since the panels are flush (within 3”) of the roof shingles, we reasonably assume that
the flat roof snow load is not able to build up both under and on top of the panels.
We have reviewed the trusses in question and find that the solar arrays can be installed without
any truss modification.
If we can of further assistance please feel free to call.
Very truly yours,
Timothy L. LaChapelle, P.E
Engineering Component Manager
attachment
10/19/10
TLL-0434192 1004142 Solar PV array loads MA 10-19-10
Project Name
Address
Engineered trusses COMMENTS
Height 6 inches 1.Roofing Construction
Width 2 inches Light: YES Heavy:
Rafter spacing 24 inches on center 2.Roof pitch:
Photovoltaic modules Units Unit Wt. Total Wt.
Solar module(s) 6 41 246
Subtotal 246
Mounting System Units Unit Wt. Total Wt.
Rails 522 0.064 33
Shared rail with cap strip 0 0.12 0
L feet 18 0.25 5
L feet on S5! Clamp 0 0.64 0
Stand-off with roof boot (single support) 6 1.28 8
Stand-off with roof boot (double support) 6 1.7 10
Stand-off with hanger bolt (single support) 0 0.4321 0
Splice bar kits 0 0.5 0
Module and rail grounding 1 3 3
Module mounting clips 18 0.16 3
Subtotal 62
Total solar module array weight 308 Pounds
Number of support stand-off 12
Total solar module array weight 308
Point load 25.6 Pounds
DISTRIBUTED LOAD CALCULATION
Photovoltaic module array area Array 1 Array 2 Array 3
Module width (horizontal) 41.18 inches 0 inches 0 inches
Module length (vertical) 61.39 inches 0 inches 0 inches
Intermodule spacing 1 inches 0 inches 0 inches
Number of module columns 2 0 0
Number of module rows 3 0 0
Array area 108 square feet 0 square feet 0 square feet
Total array area 108 square feet
Distributed load 2.9 lbs / sf
ROOF-MOUNTED SOLAR ARRAY DEAD WEIGHT LOADING CALCULATION
OVERVIEW
SOLAR MODULE ARRAY WEIGHT CALCULATION
Comments
Vinyard
50 Olander Drive, Northampton, MA
The flushed to the roof solar array being installed on the westernly part of the south roof of the building, consists of one
array of six photovoltaic modules and a roof mounting system.
The mounting system includes a series of supports that represent discrete points of contact with the roof structure. Each
support is anchored to the rafters via 3"stand-offs with stainless steel lag bolts designed with a minimum 3.5 inch thread
depth allowing for a minimum pull-out capacity of 513 pounds.
ROOF STRUCTURE
34 degrees
Sunpower 318w
Lbs/inch
supports include all hardware
supports include all hardware
and roof boots
POINT LOAD CALCULATION
Lbs/inch
supports include all hardware
TLL-0434193 1004142 Solar PV array loads MA 10-19-10