Commercial HVACVery Small AC
Lennox SGH036H4E**G Commercial HVAC Unit Manual
Setup, everyday use, maintenance and troubleshooting for the 36,000 Btu/h packaged light commercial air conditioner, with verified specifications.
- Cooling capacity36,000 Btu/h
- SEER18.6
- EER13.9
- ConfigurationPackaged
About the Lennox SGH036H4E**G
This guide covers the Lennox SGH036H4E**G, a 36,000 Btu/h packaged light commercial air conditioner on the ENERGY STAR certified light commercial HVAC list.
It is rated at 18.6 SEER and 13.9 EER under the test procedure in effect when it was certified; these older SEER and EER values are not directly comparable with the newer SEER2 and EER2 ratings. Rated cooling capacity is 36,000 Btu/h (about 3 tons).
It is listed with a non-electric heating section — on packaged units this is normally a gas-fired heat exchanger.
It uses R-410A (GWP 2,088).
Specifications
| Brand | Lennox |
|---|---|
| Model number | SGH036H4E**G |
| Model name / series | SGH036H4E**Y |
| Equipment category | Very Small AC |
| Configuration | Packaged |
| Product series | SGH036H4E**Y |
| Cooling capacity | 36,000 Btu/h |
| SEER (legacy metric) | 18.6 |
| EER (full-load cooling efficiency) | 13.9 |
| Heating section type | Other (typically gas) |
| Refrigerant | R-410A (GWP 2,088) |
| Meets ENERGY STAR peak cooling requirement | Yes |
Certified matched systems
1 certified matched system is listed for the Lennox SGH036H4E**G. Each row links to a page with that system's full ratings and guidance.
| Indoor unit | SEER2 | EER2 |
|---|---|---|
| Packaged unitGas heat | 18.6 | 13.9 |
Safety information
- Installation and service must be performed by a licensed commercial HVAC contractor following the manufacturer's instructions and applicable mechanical, electrical, fuel-gas and building codes. Refrigerant work requires EPA Section 608 certification.
- Commercial units run on high-voltage, often three-phase power. Open and lock out the disconnect before servicing, and remember that capacitors and variable-speed drives can hold a charge after power is removed.
- Fans and belt drives can start automatically. Never operate the unit with access panels removed or reach into fan sections while power is on.
- Rooftop work requires fall protection and safe access. Stay clear of roof edges, skylights and unguarded openings, and use the rigging points and methods in the installation manual when the unit is lifted by crane.
- Gas-fired heat sections must be vented and supplied with combustion air exactly as the manual specifies. Keep flue outlets clear of fresh-air intakes, and follow local requirements for carbon monoxide alarms in occupied spaces.
- If you smell gas, shut off the gas supply if it is safe to do so, avoid operating electrical switches, evacuate and call the gas utility or 911 from a safe location.
Installation and commissioning
Installation quality largely determines whether the Lennox SGH036H4E**G achieves its certified efficiency in the field. Use these points when reviewing bids and the start-up documentation.
- Load and ventilation calculation
Size the equipment from a commercial load calculation (such as ACCA Manual N or an engineer's ASHRAE-based calculation) that includes occupancy, lighting, equipment and the outdoor-air ventilation the mechanical code requires. Replacing like-for-like without a calculation often perpetuates oversizing.
- Curb and structure
Verify that the roof structure can carry the unit's operating weight and that the curb matches the unit footprint (or use a listed curb adapter for replacements). Seal the curb and duct connections carefully — curb leaks are a common source of roof water intrusion and lost air.
- Clearances
Maintain the service and airflow clearances in the manual, and keep the condenser coil away from exhaust fans, walls or other units that could recirculate hot air.
- Electrical supply
Size conductors and overcurrent protection from the nameplate minimum circuit ampacity (MCA) and maximum overcurrent protection (MOP), and install a disconnect within sight of the unit. On three-phase equipment, verify phase rotation at start-up — scroll compressors running backward are noisy, do not pump and can be damaged.
- Condensate drain
Install a trap sized for the unit's fan pressure (draw-through coils need a deeper trap), pitch the drain away from the unit and protect it from freezing. A dry or undersized trap lets air prevent drainage and causes water to back up into the unit or building.
- Gas piping
Size gas piping for the heat section input, install a shut-off and sediment trap at the unit, and leak-test all joints. The start-up technician should verify manifold pressure, temperature rise and combustion.
- Commissioning
Ask for a start-up report showing airflow and static pressure, refrigerant charge (superheat/subcooling), gas heat operation, economizer and outdoor-air settings if equipped, and thermostat or building-automation schedules.
Using your air conditioner
Schedules and setpoints
Program occupied and unoccupied schedules that match business hours. Widen setpoints when the building is empty (for example, allowing the space to drift several degrees warmer in cooling and cooler in heating), and use optimal start so the space reaches setpoint just as occupants arrive rather than hours early.
Fan and ventilation
Most codes require ventilation air whenever the space is occupied, so the supply fan normally runs continuously during occupied hours and cycles with demand afterward. If the unit has an economizer, it uses cool outdoor air for "free" cooling in mild weather; make sure dampers move freely and settings match your climate.
Managing peak demand
Commercial electric rates often include demand charges based on your highest 15- or 30-minute draw. This unit's EER of 13.9 describes its efficiency at that hot-weather peak. On sites with several units, staggering start times after unoccupied periods avoids stacking compressor starts.
Care and maintenance
A written maintenance agreement with a qualified contractor is the most reliable way to keep commercial equipment efficient. The schedule below is typical; follow the manufacturer's manual where it differs.
| When | What to do |
|---|---|
| Monthly to quarterly | Replace air filters — monthly in dusty environments, restaurants or retail with heavy traffic; quarterly in clean offices. |
| Quarterly | Inspect belts and pulleys on belt-drive units, clean the condensate pan and trap, and check for water leaks at the curb or ductwork. |
| Spring | Clean the condenser coil (more often near cottonwoods, construction or kitchens), check refrigerant pressures, contactors and electrical connections, and test economizer operation. |
| Fall | Inspect the gas heat section: burners, ignition and flame sensing, heat exchanger, flue and combustion; test safeties. |
| Every year | Inspect fan motors and bearings, cabinet and curb seals, and insulation; clean the evaporator coil if airflow or temperature split has dropped. |
Troubleshooting
| Problem | Possible cause | What to try |
|---|---|---|
| Unit not running | Disconnect or breaker off; thermostat or building-automation schedule in unoccupied mode; safety lockout. | Check the disconnect, breaker and schedule. Do not repeatedly reset lockouts — have a technician find the cause. |
| Running but not cooling enough | Dirty filters or coils; low refrigerant charge; failed compressor stage; economizer stuck open in hot, humid weather. | Replace filters and check that outdoor-air dampers close properly; call a technician for coil cleaning and refrigerant checks. |
| Very loud compressor after installation or electrical work | Reversed phase rotation on a three-phase scroll compressor. | Shut the unit off immediately and have an electrician or technician correct the phasing. |
| Water leaking into the building | Clogged or dry condensate trap; drain pan overflowing; curb or duct seal leak; ice melting off the coil. | Clear the drain and trap; have the curb and ductwork resealed if leaks continue. |
| Ice on the evaporator coil or suction line | Low airflow from dirty filters or a broken belt; low refrigerant charge. | Turn cooling off and let the coil thaw with the fan running; replace filters and inspect belts before restarting. Persistent icing needs a technician. |
| High energy bills | Schedule not matching occupancy; economizer fault; dirty coils; units fighting each other in adjacent zones. | Review schedules and setpoints, have the economizer tested, and coordinate setpoints between neighboring units. |
| Short cycling | Oversized equipment; thermostat in a poor location; control or refrigerant problem. | Relocate or recalibrate the thermostat; have the contractor review sizing and staging. |
| No heat from the gas section | Gas supply off; ignition or flame-sensing lockout; failed inducer or limit switch. | Check that the gas valve is open and power is on, then call a technician; do not bypass safety controls. |
Energy use and running costs
Assuming 1,200 equivalent full-load cooling hours a year (our assumption for a moderate climate with business-hour occupancy), the Lennox SGH036H4E**G's 36,000 Btu/h of capacity at 18.6 SEER works out to about 2,323 kWh of cooling energy per year, or roughly $395 at $0.17 per kWh.
At full load on a hot day it draws roughly 2.6 kW (capacity divided by its EER of 13.9), which is what demand charges are based on.
Actual consumption depends on climate, building loads, operating hours, ventilation rates and control settings, and these estimates exclude fan energy outside cooling hours and any demand charges. Use them to compare units rather than as a bill forecast.
Frequently asked questions
What are the efficiency ratings of the Lennox SGH036H4E**G?
The Lennox SGH036H4E**G is rated at 18.6 SEER and 13.9 EER.
What is the cooling capacity of the Lennox SGH036H4E**G?
Its rated cooling capacity is 36,000 Btu/h, about 3 tons at 12,000 Btu/h per ton.
Does the Lennox SGH036H4E**G provide heat?
Yes, it is listed with a non-electric heating section, normally a gas-fired heat exchanger on packaged units.
Is the Lennox SGH036H4E**G a packaged unit or a split system?
It is a packaged (single-package) unit: the compressor, coils, fans, heat section and controls are in one cabinet, typically installed on a roof curb or ground pad, so no refrigerant lines run into the building.
What refrigerant does the Lennox SGH036H4E**G use?
It uses R-410A (GWP 2,088).
When was the Lennox SGH036H4E**G ENERGY STAR certified?
It appears on the ENERGY STAR certified light commercial HVAC list with a certification date of May 2026.
Sources and disclaimer
Specifications on this page come from the ENERGY STAR certified commercial hvac dataset published by the U.S. Environmental Protection Agency (record certified May 6, 2026), retrieved October 7, 2026.
The setup, operating, maintenance and troubleshooting guidance is written by ManualHarbor's editors for this specific product type and configuration. It is an independent guide — not a reproduction of the manufacturer's manual — and ManualHarbor is not affiliated with Lennox. Always follow the safety instructions, installation requirements and warranty terms supplied with your unit, and contact Lennox or an authorized service provider for warranty repairs and replacement parts.
Running-cost figures use assumed U.S. average utility prices and are estimates for comparison only. See our editorial methodology for details.
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