---
watermark: ORIRO
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name: trades-hvac
provider: ORIRO.ai
copyright: Copyright (c) 2026 ORIRO.ai
description: >

  HVAC — heating, cooling, ventilation principles, maintenance, troubleshooting, and energy efficiency.




  Sources: USDA, OSHA, trade association guidelines, professional kitchen standards.
---

# HVAC

## How heating and cooling systems work

### Forced-air systems (most common in US)

**Furnace:** Burns gas (or propane, oil) to heat air. Blower distributes heated air through ducts.
**Air conditioning (split system):** Refrigerant cycles between indoor unit (absorbs heat from indoor air) and outdoor unit (releases heat outside). Cooling is heat removal, not cold creation.
**Heat pump:** Refrigerant-based like AC but can reverse cycle to provide heat. More efficient than electric resistance heat. Types: Air-source (outdoor unit), Ground-source (geothermal — higher efficiency, higher cost).
**Ductwork:** Delivers conditioned air. Return ducts bring air back. Leaky ducts: 20-30% efficiency loss common.

### Efficiency ratings

**Furnace:** AFUE (Annual Fuel Utilization Efficiency). 80%+ = good; 95%+ = high-efficiency condensing.
**Air conditioner:** SEER2 (Seasonal Energy Efficiency Ratio). 14-16 = standard; 18+ = high-efficiency.
**Heat pump:** HSPF2 (heating), SEER2 (cooling). Higher = more efficient.

## Maintenance schedule

**Monthly:** Check and replace air filter. A clogged filter: Reduces airflow → strain on system → higher energy use → shorter equipment life. MERV 8-13 filters balance filtration with airflow.

**Spring (before cooling season):**
Clean AC condenser coils (outdoor unit). Clear debris around outdoor unit (12" clearance).
Check refrigerant charge (professional). Schedule professional tune-up for AC.

**Fall (before heating season):**
Schedule professional furnace tune-up. Replace filter.
Test carbon monoxide detectors.
Check heat exchanger for cracks (professional — cracked heat exchanger = CO hazard).

**Annual:** Professional HVAC inspection and tune-up. Clean evaporator coil (indoor) as needed.

## Troubleshooting common problems

**No cooling/heating:**
Check thermostat settings and batteries.
Check circuit breaker (AC on dedicated circuit; high-voltage contactor in outdoor unit can trip).
Check air filter (clogged filter causes freeze-up).
Check outdoor unit — is it running?

**Poor airflow:**
Dirty filter (#1 cause).
Blocked/closed supply or return vents.
Damaged ductwork.

**Water around indoor unit:**
Condensate drain clogged. Flush with bleach water solution.
Frozen evaporator coil thawing (caused by: dirty filter, low refrigerant, restricted airflow).

**High energy bills:**
Air filter. Leaky ducts. Refrigerant charge. Equipment aging. Poor insulation/sealing.

## When to call a professional

Refrigerant handling: Illegal without EPA certification.
Gas line work: Always.
Electrical within the unit beyond breakers.
Heat exchanger inspection.
New equipment installation.
Poor air quality, persistent problems after basic maintenance.

**HVAC lifespan:** Furnace 15-20 years. AC 15-20 years. Heat pump 15 years. Well-maintained systems last longer.

Sources: ENERGY STAR (energystar.gov), ACCA (Air Conditioning Contractors of America), Department of Energy HVAC guides (energy.gov), ASHRAE standards summaries