Educational scope
These tools help users explore HVAC controls concepts. They do not provide project-specific professional engineering services, certified designs or approval for installation. Results can contain errors or omissions. Independently verify any result before using it in design, purchasing, wiring, commissioning or equipment operation.
FCU model limitations
The FCU model represents one well-mixed room thermal mass with simplified heating, cooling, and envelope exchange. It is not physically validated. Humidity, coil dynamics, detailed water-side behavior, and equipment protection sequences are not modeled.
Control commands are not field measurements or a validated equipment selection.
Model assumptions and boundsVAV model limitations
The VAV model includes actuator travel, a fixed-supply airflow approximation, a simplified hot-water coil and one room thermal mass. It is not physically validated and does not model a duct pressure network, humidity, detailed hydraulics or equipment protection. Available flow is separate from the configured maximum airflow setpoint.
VAV sequence, model assumptions and limitsAHU model limitations
The AHU represents one recirculating zone, idealized outdoor/return mixing, sensible-only coils and a room thermal mass. Damper position equals outdoor-air fraction by assumption. An illustrative fan/duct model supports static pressure control; a distributed duct pressure network, humidity and equipment protection are not modeled. The model is not physically validated.
AHU sequence, assumptions and limitsPump and boiler model limitations
The Pump Lead/Lag model uses illustrative parallel-pump and circuit curves, speed response and proof/fault scenarios. The Boiler Plant model uses two identical modulating boilers, ideal low-loss-header mixing and lumped water-side thermal storage. These are not manufacturer equipment curves or physically validated plant models. Boiler combustion safeguards, fuel efficiency and DHW control are outside the model.
I/O planner prototype
The I/O Planner counts entered points and compares optional channel pools. Equipment templates are examples. Capacity counts, signal-list membership and duplicate-terminal checks do not establish terminal, electrical or expansion-module compatibility. The output is a planning aid, not an approved wiring schedule.
Control behavior
Each simulator has its own documented sequence. FCU valve CO and VAV FLOW_CO implement a documented educational interpretation of referenced CO behavior. They are not Delta Controls products or firmware emulators; nonzero derivative gain is not implemented. AHU, Pump and Boiler use separately documented conventional P/PI loops, as does VAV SAT control.
Calculators and recommendations
Calculators use the methods and assumptions stated on their pages. Motor current and damper torque are estimates from user-supplied parameters; they are not field measurements. Current sensor ranges do not establish product compatibility. Relay and temperature sensor selectors compare user-entered specifications, with unknowns left unconfirmed. The resistance lookup uses nominal curves; the voltage-drop tool does not size protection or determine ampacity. Product placeholders are not endorsements.
Independent project
Controls Tools is not affiliated with, sponsored by or endorsed by the manufacturers or standards organizations mentioned. Manufacturer names and technical references identify sources and context; they are not certifications or approvals of this site.
Project-specific verification
Check units, assumptions, operating conditions, and applicable project and manufacturer requirements. No teaching constant should be treated as a code, standard, or manufacturer requirement.