Condenser Heat Load Calculator

Calculation method

Select a method.

Design margin

%

Typical: 5-15% for early sizing.

Ambient temperature (optional)

C

Used for documentation in reports.

Altitude (optional)

m

Adjusts air density for air method.

Water / Glycol Inputs

Fluid flow rate

Enter the measured or design flow.

Flow unit

Entering temperature

C

Leaving temperature

C

Specific heat

kJ/kg.K

Water near room temperature ~ 4.186.

Density

kg/m3

Water ~ 1000 kg/m3 (approx.).

Property correction factor

Use 1.00 for water, adjust for glycol.

Example Data Table

Scenario	Method	Key Inputs	Estimated Heat Load	Design Margin
Chiller condenser water	Water / glycol	Flow 8.0 L/s, 30C to 35C	~167 kW	10%
Air-cooled package unit	Air sensible	Air 7,500 CFM, 35C to 43C	~120 kW	8%
Process cooling skid	Load + power	Evap 250 kW, Power 60 kW, Eff 0.95	~313 kW	12%

Values are illustrative. Use project-specific fluid properties and measured flow when available.

Formula Used

Water / glycol side

Uses flow and temperature rise on the fluid side.

Q(kW) = m_dot(kg/s) x Cp(kJ/kg.K) x dT(C)

Where m_dot = rho x V_dot. A correction factor can approximate glycol property shifts.

Air sensible side

Estimates sensible heat based on airflow and temperature rise.

Q(kW) = rho_air x V_dot x Cp_air x dT

Altitude reduces air density; you can override density if you have measured data.

Load + power balance

Useful when you know cooling load and compressor power.

Q_reject = Q_evap + (P_comp / eta_motor) + Q_aux

If heat recovery is applied, Q_reject is reduced by the recovery fraction.

How to Use This Calculator

Select a calculation method that matches your available field data.
Enter flow or load inputs with correct units and realistic temperatures.
Set a design margin if you want conservative sizing outputs.
Press Submit to view results directly above the form.
Use Download CSV or Download PDF to share results with stakeholders.

Field context for condenser heat rejection

Condenser heat load represents the total heat a refrigeration or chilled-water system must reject to the environment. On construction sites, accurate rejection estimates help size cooling towers, air-cooled condensers, piping, and temporary utilities. Underestimating load can drive high head pressure, nuisance trips, and slow commissioning. Overestimating increases equipment cost and fan or pump energy.

Selecting an input method

This calculator supports three practical approaches. Use the water or glycol method when you can measure condenser flow and temperatures. Use the air method when you have airflow and discharge temperature rise across coils or heat exchangers. Use the load plus power balance when you know evaporator duty and compressor input from nameplate data, metering, or controls trending. When data is limited, cross-check with equipment catalog heat rejection, and revisit once stable operation is reached during balancing and performance testing onsite cycles.

Water-side measurements that improve reliability

For water systems, verify sensor placement and stabilize readings before logging. Take entering and leaving temperatures on straight pipe runs, away from mixing tees. Confirm flow using a calibrated meter or pump curve and differential pressure. If glycol is present, adjust properties; both density and specific heat shift and influence the calculated mass flow and heat transfer rate.

Air-side considerations for outdoor equipment

Air sensible estimates depend on air density, airflow, and temperature rise. Density drops with altitude and high temperature, reducing heat carrying capacity. Airflow should reflect actual fan performance with filters, guards, and wind effects. Use representative temperature probes across the leaving air stream and avoid hot spots near compressor discharge lines that can bias readings upward.

Using results for sizing and documentation

The output provides estimated and design heat loads in kW, Btu/h, and tons. Apply a margin for uncertainty, fouling, and future load growth, then compare against manufacturer ratings at the expected ambient and approach temperatures. Exporting the result supports submittals, temporary plant planning, and handover records, especially when multiple test conditions are documented consistently.

FAQs

1) Which method should I use first?
Start with the method that matches your best data. Measured water flow and temperatures usually provide the most reliable estimate for water-cooled systems.

2) Why do I get a negative heat load?
Negative results typically mean the leaving temperature is lower than entering for the selected method. Check sensor locations, sign convention, and flow direction.

3) How do I handle glycol mixtures?
Glycol changes density and specific heat. Enter the best available Cp and density, or use the correction factor to approximate property shifts for quick planning.

4) Does the air method include moisture effects?
No. The air method estimates sensible heat only. If condensation or wet coils are expected, rely on equipment ratings or a psychrometric analysis.

5) What design margin is reasonable?
For early sizing, 5–15% is common. Use higher margins when measurements are uncertain, fouling is expected, or future capacity growth is likely.

6) How should I use the exported CSV or PDF?
Attach exports to commissioning logs, submittals, or change records. Include the test condition, method used, and any assumptions about properties or airflow.