Pelorus Engineering
Menu
LearnFault libraryReadiness quizWhat your data unlocksGet your dataGlossarySee Energy Agent
AHU-X01 · Air-side AHU

Fighting coils — heating and cooling on at the same time

The heating valve and the cooling valve are both driving open simultaneously on the same AHU.

Physics-basedBAS trendsMedium effort

What does AHU-X01 mean?

The heating valve and the cooling valve are both driving open simultaneously on the same AHU.

Why does it matter?

Every minute of overlap burns gas to make heat that chilled water immediately removes. This is one of the highest-$ pure-waste faults in HVAC and is invisible without per-actuator data.

What should you do?

Check the AHU sequence: is there a deadband between heating and cooling demand? Confirm both valves seat fully closed (a stuck-open valve will look like this). Verify the SAT setpoint and reset logic aren't asking heating and cooling to chase each other.

How Energy Agent prices a finding

Written by Pelorus Engineering · Brent Waluzak, P.E. (FL), President, Pelorus EngineeringLast updated
Estimate it

What is heating and cooling at the same time costing?

Estimate the energy spent fighting yourself.

1 ton of cooling is 12 kBtu/h.
Enter a repair or controls-change cost to see the simple payback.
Avoidable cost per year—Energy —Simple payback Enter a cost to fix to see the payback.

    Cooling that only exists to cancel heating (and vice versa) is priced on both sides: chilled water at your kW/ton and rate, heat at your boiler efficiency and gas price, for the hours the overlap lasts. Energy Agent finds the overlap in valve and coil trends.

    Screening estimate. Energy Agent measures the real fault hours and load from your trends and prices them at your tariff.

    Request a demoSee how Energy Agent prices a finding

    Screening-level estimates; confirm with measurement and verification before capital commitment.

    More air-side ahu faults

    All 32 air-side ahu rules →

    See these rules run on your building.

    Send twelve months of interval data and a BAS trend export. Energy Agent returns a ranked list of what is wasting money, what each item is worth per year at your tariff, and what to do about it.

    Request a demoBenchmark your building