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Systems & Airflow

These issues come from system configuration — specifically supply temperatures and whether a system has been set up at all.

Cooling supply airflow shows a negative value

Section titled “Cooling supply airflow shows a negative value”

A negative cooling supply airflow is almost always a system-configuration issue:

  • Supply temperature too high. If the final cooling supply temperature (at the central or terminal unit) is higher than the indoor cooling setpoint, ΔT goes negative and produces a negative CFM.
  • Missing supply temperature. Without a cooling supply temperature set, HVAKR can return a false value.
  • Swapped values. Heating and cooling inputs entered in the wrong fields.

To fix, check the cooling supply temperature in the system configuration and set it below the indoor cooling setpoint. See System Configuration. If it’s still unresolved, share the project with HVAKR support for a closer look.

“Cooling coils are disabled on terminal and central units” warning

Section titled ““Cooling coils are disabled on terminal and central units” warning”

This warning means the system hasn’t been configured with cooling coils yet. It affects the system’s design CFMs, coil loads, psychrometrics, and Central Cooling Data outputs.

It does not affect the underlying raw load calculation. If you’re only after a theoretical load calculation, the warning does not mean your envelope or space loads are wrong.

Until the system is configured, expect:

  • Central Cooling Data showing N/A
  • Coil-related outputs zeroed out
  • Airflow values that don’t yet reflect a fully configured system

Configure the system to clear the warning and populate these outputs — see System Configuration.

Average space setpoint reads -459.7°F

Section titled “Average space setpoint reads -459.7°F”

-459.7°F is the Fahrenheit equivalent of 0° Rankine — it indicates a zero or undefined value, not a real temperature.

The average space setpoint is a weighted average based on space design airflows (so small, low-airflow spaces don’t skew the average). If no system has been configured and no supply air temperatures are defined, design airflows can’t be computed, the weighted average returns zero, and it displays as -459.7°F.

To resolve:

  1. Configure a basic system.
  2. Set cooling and heating supply air temperatures.
  3. Let HVAKR calculate design airflows.

The setpoint then displays correctly (e.g., 72°F).