Whole-House Standby Generator Installation SOP

Purpose

Standardize installation of permanently-mounted whole-house standby generators. Combines electrical work, gas plumbing, foundation work, + system commissioning. Wrong install = generator that doesn't start when needed.

Scope

Residential standby generators (Generac, Kohler, Briggs & Stratton, Champion) 10-26kW range, natural gas or propane fueled. Excludes portable generators (different SOP) + commercial standby systems.

Prerequisites

• Generator specified (sized + selected with customer)
• Site preparation: concrete pad area cleared
• Permits pulled: electrical + gas (sometimes building)
• Generator delivered + uncrated
• Tools: standard electrical kit, gas-line tools, masonry tools for pad
• Crew: licensed electrician + plumber + helper (2-3 trade specialties)
• 2-3 days for typical install

Pre-install survey + planning

Step 1: Site survey (during quote)

1. Generator location:

• 18 inches minimum from house exterior wall
• 5 feet minimum from operable windows + doors
• 3 feet from combustibles
• Level area for concrete pad
• Accessible for service (3 ft clearance all sides)

1. Fuel source:

• Natural gas: meter location, BTU capacity check
• Propane: tank size needed, tank location

1. Electrical:

• Distance to main panel
• Service amperage (200A typical for whole-house)
• Existing transfer switch (replacing) or new install

1. Permits required:

• Electrical permit
• Gas permit (sometimes plumbing permit)
• Building permit if pad work

Procedure

Day 1 - Site prep + concrete pad (4-6 hours)

1. Mark location with stakes
2. Excavate to 6 inches deep
3. Compact base
4. Form + pour concrete pad (4 inches minimum thickness, typically 4×4 ft or larger)
5. Embed conduits during pour for electrical + gas
6. Cure 24+ hours before generator placement

Or use pre-fabricated composite pad - quicker but more $.

Day 1 afternoon - Run conduits + lines

1. Underground conduit from generator to house service panel

• 1-1/4" PVC minimum for the main service feeder
• 3/4" PVC for control wiring
• 18-24" deep trench

1. Gas line from existing gas service (or new propane tank)

• Size per generator BTU + run distance
• Drip leg + shutoff at generator

Day 2 - Generator placement + connections (4-6 hours)

1. Position generator on pad with crane or 4-person lift
2. Anchor with concrete fasteners
3. Connect gas line + perform pressure test
4. Run electrical conductors from generator to transfer switch
5. Install transfer switch (see: Transfer Switch Installation HowTo)
6. Connect battery + battery charger
7. Connect natural gas + open valve (test for leaks with detector)

Day 2-3 - Transfer switch + load wiring (4-6 hours)

1. Install transfer switch beside main panel (in conduit-accessible location)
2. Wire from generator output → transfer switch
3. Wire from transfer switch → main panel (or sub-panels for partial load)
4. Determine load priorities:

• Whole-house: all circuits supported
• Essential circuits: selected critical circuits

1. Re-route branch circuits as needed

Day 3 - Commissioning + customer walkthrough (2-3 hours)

1. Initial inspection:

• All connections torqued to spec
• Gas line pressure tested
• Battery installed + charged
• Oil + coolant levels verified

1. Generator start test:

• Manual start (with utility on)
• Verify proper RPM + voltage
• Verify frequency (60 Hz)

1. Transfer switch test:

• Simulate utility outage (open main breaker briefly)
• Generator auto-starts within 20-30 seconds
• Transfer switch transfers load
• Generator runs steady

1. Restore utility:

• Close main breaker
• Transfer switch returns to utility power
• Generator continues running 1-2 min cooldown
• Generator shuts off

1. Auto-test:

• Configure weekly self-test (typical: Tuesday morning, 5 minutes)

1. Customer briefing:

• Demonstrate operation
• Explain auto-test schedule
• Maintenance schedule (annual)
• Battery replacement (every 2-3 years)
• Provide all manuals + warranty info
• Mobile app setup (most modern units)

Acceptance criteria

• Generator anchored + level
• All electrical connections torqued + inspected
• Gas pressure tested (leak-free)
• Transfer switch operational
• Auto-start verified
• Weekly self-test configured
• Customer signoff on operation
• Permits inspected + closed

Common pitfalls

• Wrong placement: too close to house, blocked airflow, neighbor complaint about noise
• Undersized gas line: generator starves for fuel at full load
• Wrong transfer switch type: load mismatch (whole-house vs essential-only)
• Skipped pressure test: gas leak hazard
• Battery left disconnected: generator won't auto-start
• Cooldown timer too short: generator overheats on shutdown
• Auto-test scheduled during sleep hours: customer complaint
• Not training customer: customer has no idea what's happening when it runs
• Permit not closed: legal issue later

Sizing review (verify before install)

A whole-house generator should match home load. Common ratings:

• 8-10 kW: small home, essential circuits only
• 14-17 kW: medium home, most circuits + AC
• 20-26 kW: large home, whole-house

Rule of thumb: 1.5-2 kW per 1,000 sq ft of conditioned space. Verify with full electrical load calculation.

Permits + inspections

• Electrical permit: required in most jurisdictions
• Gas permit: required
• Building permit: sometimes for pad work
• Air quality permit: required in some areas
• HOA approval: confirm before scheduling work

Inspector visits typical:

• Rough electrical (before sheetrock if interior conduit)
• Final electrical (transfer switch operational)
• Gas (pressure test + leak check)

Maintenance schedule to set up

• Weekly: 5-minute auto-test (configured during install)
• Monthly: customer visual inspection
• Annually: locksmith service visit (oil change, filter, inspection)
• Every 2-3 years: battery replacement
• Every 200 hours of run time: deeper service (post-extended outage)

Customer follow-up

• 30 days post-install: call to verify everything operating
• 6 months: reminder for first annual service
• Annual maintenance contracts: 60-80% conversion rate

References

• Manufacturer installation manuals (Generac, Kohler, etc.) - legally binding
• NEC Article 700 (Emergency Systems) + Article 702 (Optional Standby)
• NFPA 70 + 110 + 37 + 54
• IRC residential
• Manuall internal: Transfer Switch Installation, Generator Sizing for Residential