HVAC electrical: sized to equipment, coordinated with mechanical.
Commercial HVAC electrical requires careful coordination with HVAC contractor — equipment sizing, control circuits, condensate pump electrical, and proper disconnect locations.
By Steven Lockhart · Reviewed by Alex Towery, C-10 #989290
Updated 2026-06-16
Commercial HVAC electrical scope: dedicated circuits per HVAC unit sized to nameplate (rooftop units 30-100A typical, split system condensers 20-40A, air handlers 15-30A, ductless mini-splits 15-30A per zone), control circuits between thermostats and equipment, condensate pump circuits where required, equipment disconnect at each unit per NEC, sometimes 3-phase for larger commercial equipment. Coordinate sizing with HVAC contractor during design phase.
01HVAC electrical considerations.
Equipment sizing drives electrical scope significantly. Modern variable-speed equipment (VRF systems, inverter heat pumps) often draws less peak current than older constant-speed equipment of similar capacity. Newer equipment specs vary from older — verify current nameplate not historical norms when sizing circuits for replacements or upgrades.
Disconnect requirements per NEC 440: each HVAC unit needs a disconnect within sight of the equipment for service safety. Implementation typically AC disconnect switch on exterior wall near equipment (split systems) or fused disconnect on rooftop near units (rooftop units). Disconnect ratings must match equipment circuit ratings.
02Three coordination points with HVAC.
Equipment selection and sizing
HVAC contractor selects equipment based on cooling/heating loads. We size circuits based on equipment specifications. Coordination prevents undersized or oversized electrical infrastructure. Lock equipment selection before electrical rough-in.
Control circuit and thermostat wiring
Low-voltage thermostat wiring connects controls to equipment. Modern smart thermostats sometimes require neutral connection. HVAC contractor typically wires control circuits; we provide electrical infrastructure (line voltage to equipment, sometimes neutral at thermostat for smart controls).
Condensate and accessory circuits
Condensate pumps where gravity drainage isn't possible: dedicated 120V circuit. Service receptacles near rooftop units: dedicated outlet for technician convenience and code compliance. Equipment heater elements (for cold-climate condenser protection): dedicated circuits typically. These accessories often overlooked in initial design; we plan with HVAC contractor.
03Commercial HVAC electrical patterns.
Rooftop unit installations: equipment circuit sized to RTU nameplate × 1.25 (typically 30-100A 208V 3-phase or 480V 3-phase for larger units), fused disconnect at unit per NEC 440, sometimes equipment ground rod for lightning protection on rooftops. Multi-RTU installations have separate circuit per unit.
Split system installations: condenser unit outside building has dedicated circuit and disconnect. Air handler inside building has dedicated circuit. Refrigerant lines installed by HVAC contractor; line voltage by us. Coordination on equipment locations affects conduit routing and disconnect placement.
Common questions.
What size HVAC circuit do I need?
Per equipment nameplate × 1.25. Modern small commercial: 20-40A typical. Mid-sized commercial: 40-80A typical. Large commercial: 80-200A+ typical for major equipment. Equipment selection drives circuit sizing; verify nameplate during design.
Does HVAC need 3-phase?
Larger commercial HVAC (above ~5-ton residential equivalent) typically specifies 3-phase. Smaller commercial often single-phase. For buildings with 3-phase service, 3-phase HVAC equipment is standard. Single-phase buildings limit equipment selection.
Who runs the thermostat wiring?
HVAC contractor typically — low-voltage control wiring is HVAC scope. We provide infrastructure (line voltage to equipment, neutral at thermostat location for smart controls if needed). Some projects scope thermostat wiring to electrical contractor; varies by project. Coordinate during scope definition.
How do you handle pricing — flat fee or hourly?
Both, depending on scope. Routine service calls and predictable scope (panel replacement, EV charger install, transfer switch install, fixture replacement) are flat-fee quoted up front. Diagnostic visits and emergency scope are hourly because we don't know what we'll find. Either way, you get a written quote before work starts on anything significant, and we don't proceed beyond the quote without your sign-off.
How quickly can you schedule?
Depends on scope and season. Emergency dispatch: same-day across Marin County (1-3 hours business hours, 1-4 hours after-hours). Same-day standard service: 3-6 hours from call when capacity allows; otherwise next business day. Scheduled service work: 1-3 weeks typical. Larger projects requiring permits and PG&E coordination: 4-12 weeks depending on scope. We're upfront about timeline at the quote stage.
What warranty do you offer on work?
Our standard residential warranty: 2 years on labor, manufacturer warranty on parts (varies by product — typically 1-10 years). Major installs (panels, generators, EV chargers) often have longer manufacturer warranties (5-10 years). If there's an issue with our work in the warranty period, we come back and fix it at no cost. We also stand behind work past warranty — repeat customers and referrals matter more than a transactional fix.
Are you licensed and insured?
Yes. California State License Board C-10 Electrical Contractor #989290, in good standing. Carry general liability insurance and workers' compensation insurance as required by California law. Bondable on projects requiring it. Happy to provide proof of insurance to clients or property managers on request. License lookup: cslb.ca.gov.
Talk to a licensed electrician in Marin.
Family-run, C-10 #989290, 20+ years in the trade. Honest scoping, fair pricing, work that lasts.