AHU Coil Capacity Calculator (Cooling / Heating)

AHU Coil Capacity Calculator (Cooling / Heating) | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Math & Numbers
Input types: number, select
Output type: json
Sample coverage: 4
API ready: Yes

Overview

The AHU Coil Capacity Calculator computes total, sensible, and latent coil capacity plus the sensible heat ratio (SHR) from dry-air mass flow and entering and leaving air conditions. Enter dry-bulb temperatures with relative humidity or humidity ratio for each state, then choose the output units.

When to use

Estimate cooling coil capacity from entering and leaving air temperatures and relative humidity.
Calculate heating coil capacity using humidity-ratio inputs for the entering and leaving air.
Separate total capacity into sensible and latent components and review the resulting SHR.

How it works

1Enter the dry-air mass flow and select kg/s or kg/h.
2Provide entering and leaving dry-bulb temperatures in °C.
3For each air state, enter either relative humidity in percent or humidity ratio in g/kg or kg/kg.
4The calculator derives humidity ratio and enthalpy as needed, then returns total, sensible, and latent capacity, SHR, and formatted results in kW, W, or BTU/h.

Use cases

HVAC engineers can estimate AHU cooling coil loads and identify the sensible and latent portions of the duty.
Building-services designers can check heating coil capacity from dry-air flow and air-state measurements.
Commissioning teams can compare entering and leaving air conditions using enthalpy, humidity ratio, and SHR results.

Examples

1. Cooling coil capacity from relative humidity

HVAC engineer

Background

An engineer is checking an AHU cooling coil with 2.5 kg/s of dry-air flow. The entering air is 27 °C and 50% RH, while the leaving air is 14 °C and 90% RH.

Problem

Determine the coil's total, sensible, and latent capacity and calculate its SHR.

How to use

Enter 2.5 kg/s, select relative humidity for both states, enter 27 °C and 50% for the entering air, then 14 °C and 90% for the leaving air. Select kW as the capacity unit.

mda=2.5; flowUnit=kg/s; t1=27; h1Input=relative humidity; h1Value=50; t2=14; h2Input=relative humidity; h2Value=90; capacityUnit=kW

Outcome

The calculator returns approximately 47.01 kW total capacity, 33.31 kW sensible capacity, 13.70 kW latent capacity, and an SHR of 0.709.

2. Heating coil with constant humidity ratio

Building-services designer

Background

A heating coil handles 3 kg/s of dry air, raising the air temperature from 5 °C to 30 °C while the humidity ratio remains 3 g/kg dry air.

Problem

Calculate the heating duty when no humidity-ratio change is specified.

FAQ

What does this AHU coil calculator calculate?

It calculates total capacity, sensible capacity, latent capacity, and sensible heat ratio (SHR).

Can I calculate both cooling and heating coils?

Yes. The signed result supports both cooling and heating coil calculations.

What humidity inputs are supported?

Each air state accepts either relative humidity from 0–100% or humidity ratio.

Which units can I use for humidity ratio?

Humidity ratio can be entered in g/kg dry air or kg/kg dry air.

Which capacity units are available?

Results can be displayed in kilowatts (kW), watts (W), or BTU per hour (BTU/h).

mda=3; flowUnit=kg/s; t1=5; h1Input=humidity ratio; h1Value=3; t2=30; h2Input=humidity ratio; h2Value=3; humidityUnit=g/kg; capacityUnit=kW

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Cooling coil capacity from relative humidity

2. Heating coil with constant humidity ratio

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