How Many Amps Does a 4 Ton Heat Pump Use

A 4 ton heat pump (about 48,000 BTU/h) is a common size for medium-to-large homes and light commercial spaces. Electrical current draw varies widely by model, voltage, compressor type, and operating conditions. This article explains how to read nameplate data, estimate running and starting amps, choose proper wire and breaker sizes, and understand real-world factors that affect amperage. Check the unit nameplate and installation manual first for exact requirements.

Characteristic	Typical Range (Single-Phase 208/230V)
Running Amps (Full Load)	20–45 A
Minimum Circuit Ampacity (MCA)	30–60 A
Maximum Overcurrent Protection (MOP/Max Breaker)	45–70 A
Locked Rotor/Starting Amps (LRA)	100–250 A

How Heat Pump Capacity Relates To Electrical Demand

Heat pump capacity in tons converts to cooling capacity in BTU/h: 1 Ton = 12,000 BTU/h, so a 4 ton unit delivers about 48,000 BTU/h. Electrical input is not directly proportional to tonnage because efficiency (SEER, HSPF, COP) determines how much electrical power is needed per BTU.

Rodger conversions: 1 ton refrigeration ≈ 3.517 kilowatts of cooling. A 4 ton unit equals roughly 14.07 kW of cooling output. If a system has a coefficient of performance (COP) of 3.0, electrical input would be ~4.69 kW (14.07 ÷ 3.0).

Basic Electrical Calculation For Running Amps

Estimate running amps for single-phase 208/230V equipment using: Amps = kW ÷ Volts. For three-phase use: Amps = kW ÷ (√3 × Volts × Power Factor) where power factor is often near 0.95 for motors.

Example: If a 4 ton heat pump requires 4.8 kW running power, on 240V single-phase: 4,800 W ÷ 240 V = 20 A running. Many real-world 4 ton units draw more because compressor motors and fans add loads and because rated power during high-demand conditions is higher.

Nameplate Terms: RLA, LRA, MCA, And MOP Explained

The outdoor unit nameplate lists critical electrical values: RLA (Rated Load Amps) is the normal operating current for motors at full load; LRA (Locked Rotor Amps) is the starting or stall current of the compressor motor; MCA (Minimum Circuit Ampacity) is the minimum conductor ampacity required by the manufacturer; MOP or Max Fuse/Max Breaker is the largest overcurrent protective device permitted.

Typical 4 ton nameplate examples: RLA 20–40 A, LRA 120–220 A, MCA 35–55 A, MOP 45–70 A. Always wire and protect to MCA and MOP values shown on the unit; local code and utility requirements may adjust sizing.

Typical Amperage Ranges For 4 Ton Heat Pumps

Below are common ranges based on equipment type. These are generalizations; manufacturer specs may differ.

• Standard Single-Stage Compressor (240V): Running 25–40 A; MCA 35–60 A; MOP 45–70 A; LRA 120–200 A.
• Two-Stage Compressor: Lower stage may draw 12–20 A, high stage 30–45 A; starting currents still high but somewhat moderated.
• Inverter/Variable-Speed Compressor: Running amps often lower (15–30 A) and starting amps much lower than fixed-speed units due to soft-start capability; MCA typically 30–50 A.
• Three-Phase Commercial Units: Per-phase running amps are lower (10–25 A per phase) but total power similar; MCA and MOP are specified per manufacturer.

Why Starting Amps Are Much Higher

Compressor motors require a large inrush current to overcome inertia and start under load. A fixed-speed compressor may show very high LRA (100–250 A). This does not mean the breaker should be sized to LRA; the breaker rating follows the MOP on the nameplate, and motor circuits use time-delay (HD) breakers or fuses capable of handling inrush.

Real-World Example Calculations

Example 1: Single-Phase Fixed-Speed 4 Ton

Nameplate: RLA 30 A, LRA 160 A, MCA 45 A, MOP 60 A. On 240V single-phase: running amps about 30 A. Recommended conductor: 6 AWG copper for 45 A ampacity (NEC), with 60 A breaker per MOP. Short-term inrush up to 160 A is handled by the time-delay breaker.

Example 2: Variable-Speed 4 Ton Inverter

Nameplate: RLA 22 A, LRA 90 A, MCA 35 A, MOP 45 A. Running amps ~22 A on 240V. Use 8 AWG copper for 35 A ampacity or per local code; install 45 A max breaker as specified. Inverter units reduce peak demand and may allow smaller service upgrades in many installations.

Voltage Differences: 208V vs 230V Impact

Some multi-family or older buildings use 208V three-phase or 208V single-phase. Current increases as voltage decreases for the same power. Example: a 4.8 kW load draws 23.1 A at 208V but 20.0 A at 240V. Nameplate values often specify both voltages; use the correct column for calculations and wiring.

Wire Size And Breaker Selection

Select conductors based on MCA and NEC ampacity tables; select overcurrent protection based on MOP/Max Fuse/Max Breaker. Common combos for single-phase 4 ton:

• MCA 30–40 A → 8 AWG copper, 40 A breaker (verify MOP)
• MCA 40–60 A → 6 AWG copper, 60 A breaker
• MOP often specifies maximum breaker: e.g., 60–70 A → use 6 AWG or as required locally

Always follow nameplate and local electrical code; some installations require derating for ambient temperature, conduit fill, or multi-cable bundling.

Factors That Increase Running Amps

Several operational and environmental factors can raise amp draw above nameplate running values: low refrigerant charge, dirty coils, clogged filters, undersized ductwork, extremely hot/cold outdoor conditions, failing capacitors, and worn bearings or compressors. These can increase compressor workload or reduce efficiency, causing higher current and possible nuisance trips.

Monitoring And Troubleshooting High Amp Draw

To verify actual amps use a clamp-on true RMS ammeter or a digital multimeter rated for the expected current. Compare measured running amps to nameplate RLA and MCA. If measured amps exceed nameplate values, inspect filters, coils, refrigerant levels, contactors, capacitors, and airflow.

If starting amps are unusually high or breakers trip, consult an HVAC technician. Persistent overcurrent can damage compressor windings and shorten equipment life.

Energy Use And Monthly Cost Estimates

Estimating electrical consumption provides perspective. If a 4 ton heat pump draws 30 A at 240V while running, electrical power is 240 V × 30 A = 7.2 kW. If it runs 8 hours per day, daily use ≈ 57.6 kWh. At $0.20/kWh, daily cost ≈ $11.52 and monthly (30 days) ≈ $345.60. Variable-speed units often reduce both running amps and runtime, lowering bills.

Upgrading Service Or Panel For A 4 Ton Unit

Adding a 4 ton unit may require a panel or service upgrade if the home’s electrical capacity is insufficient. Calculate simultaneous loads and consult an electrician to determine if 200A service is adequate or if subpanel dedicated circuits are needed. Always size service to meet continuous loads and NEC rules.

Key Takeaways And Practical Guidance

• Check the unit nameplate first: RLA, LRA, MCA, and MOP provide the authoritative electrical limits.
• Typical running amps for a single-phase 4 ton heat pump are roughly 20–45 A, but MCA and MOP values determine wiring and breaker sizing.
• Starting (LRA) can be very high (100–250 A) but is handled by time-delay protection; do not size breakers to LRA.
• Inverter/variable-speed models reduce starting and running amps and often enable lower operational costs.
• Wire gauge selection (8 AWG, 6 AWG, etc.) depends on MCA and local code; consult a licensed electrician.

Resources And References

For precise guidance consult the unit’s installation manual, the National Electrical Code (NEC), and local electrical codes. Manufacturer spec sheets and HVAC service technicians provide model-specific data for safe, code-compliant installations.

Reminder: This article provides typical ranges and calculation methods; exact amp draw varies. Always follow the equipment nameplate and consult a licensed electrician or HVAC technician for installations and troubleshooting.