PV Site Assessment (PV 201)

Module 4: Balance of System Location 1 Module 4: Balance of System Location

This module will cover variables to consider when choosing the balance of system (BOS) location. We’ll discuss how to analyze the existing electrical infrastructure, how the proposed PV system will be integrated, and how to document your findings in the site assessment report.

Content outline: • Existing electrical infrastructure (panels and breakers) • Illustration of Balance of System (BOS) • Installation considerations • Electrical integration 2 Existing Electrical Infrastructure

Variables to check: • Service entrance – location and size • Service panel characteristics (fuses/breakers, voltage and current ratings, manufacturer, model, available open spaces) • Working space (clearance) for additional equipment • Area available for mounting inverter, disconnects, and/or other balance of system equipment • Conduit routes from array and between BOS components • Area for batteries, if applicable 3 Electrical Safety

• Non-conductive ladders • Never remove panel/box covers unless you’re a licensed electrician 4 Existing Electrical Infrastructure

Electrical Service Panel: What size MAIN circuit breaker does the panel have? • 100A CB = generally 20A maximum inverter output • 200A CB = generally 40A maximum inverter output • 120% rule: National Electrical Code (NEC) Article 705

• Does the panel have two open spots for a two-pole (240V) circuit breaker? • What if there are fuses instead of circuit breakers? 5 Service Panels

• Panelboards • Load centers 6 120% Rule

Main breaker + Backfed breaker ≤ 120% panel busbar rating 7 Load-Side Connections and 120% Rule

Main breaker + Backfed breaker ≤ 120% busbar rating 8 What if there isn’t enough space?

Problem: Service panel is full of circuit breakers. No room for two- pole, backfed circuit breaker for PV inverter. Solutions: • Line-side connection • Install a feeder (sub) panel • Update service panel to one with more spaces • 42 spaces is the most you will see in a “standard” panel • Requires licensed electrician 9 What if the service is too small?

Problem: 100 A service. Big PV array. 20 A backfed breaker won’t do. Can’t adhere to the 120% rule… Solutions: • Line-side connection • Update service to 200 A • Requires licensed electrician, $$$ • Install new service panel (higher busbar rating), but keep main breaker rated 100 A • Requires licensed electrician 10 Panels and Circuit Breakers

• Circuit breakers with “line” and “load” marked on them are NOT suitable for backfeed • AFCI/GFCI • Common electrical panel/circuit breaker manufacturers: • Cutler-Hammer • Federal Pacific • Siemens • Square D • Inverter output can be 120V, 240V, 208V, 277V, 480V • Single-pole, two-pole, three-pole (for three-phase systems) 11 Documentation

• GE PowerMark Plus • 252B3168PS • 120/240 VAC, 1-Phase, 3-wire, 125 Amp Max • Use only GE type Breaker: THQL, THHQL, or TXQL

Source: GE PowerMark Plus 12 What if it’s a fused service panel?

SERVICE UPGRADE REQUIRED. Call an electrician. 13 Existing Electrical Infrastructure

Working clearances: • The inverter and BOS components require adequate working space and clearances (assume at least 5’x5’) • Integrated AC/DC disconnects (in the inverter) take up less room – • Check with your local AHJ (electrical inspector)

• Minimum headroom = 6.5’ (existing dwelling basements exempt) • Minimum depth (reach) = 3’ • Minimum width = 30” or width of equipment (whichever is >) • Doors/hinges must be able to open 90° • Should be readily accessible and not used as storage space 14 Working Clearances 15 Existing Electrical Infrastructure

The kWh meter: • Where is the meter located? • Where is it, in relation to the main service panel? • Document if it’s an overhead (service drop) or underground (service lateral) connection from the utility • Take pictures! • Does the utility require an additional AC disconnect switch outside, next to the meter? • Existing meter will have to be changed/reprogrammed for bidirectional operation, or a second kWh meter will be installed • Contact the utility for rules or recommendations 16 Service Entrance and kWh Meter 17 Service Entrance 18 BOS Installation Considerations

Grid connection options: • Line-side interconnection • Made at kWh meter or on/before main breaker in service panel • Load-side interconnection • Requires dedicated two-pole breaker in service panel or feeder panel for each 240V inverter. Document number of empty spaces. • Electrician or installer concern: overloading busbar in load center • Microinverters • Eliminate stringing circuits and routing to “main” inverter 19 BOS Installation Considerations

• Size of existing service • 100A = 20A max inverter output (generally) • 200A = 40A max inverter output (generally) • Mounting additional electrical equipment • Requires dedicated space • Photograph potential location(s) • Measure and document available space • Document potential conduit routes and/or obstacles 20 Proposed BOS Illustration 21 Electrical Integration

Conduit routes: Trenching and obstacles • Existing infrastructure (natural gas, phone, cable, electrical, water, sewer, sprinklers, etc.) • Soil type • Distance (voltage drop considerations) DC conductors • Array conductors to inverter(s) and disconnect(s) AC conductors • Inverter(s) to service panel and disconnect(s) 22 Raceways, Conduit Routes

Under the collector

4” bellow roof, not under The collector 12” bellow roof 23 Site Assessment Report Template

4.0 Balance of System Location 4.1 Existing Electrical Infrastructure 24 Site Assessment Report Template

4.1 Existing Electrical Infrastructure 25 Site Assessment Report Template

4.1 Existing Electrical Infrastructure 26 Site Assessment Report Template 27 Module 4 Review: Balance of System Location

• Existing electrical infrastructure (panels and breakers) • Illustration of Balance of System (BOS) • Installation considerations • Electrical integration 28