Air handler chilled-water requests
A sequence for one air handler that tells the chilled-water plant how hard it is working. Its reset requests (0 to 3) are summed over the air handlers and feed the plant reset; its plant request (0 or 1) says the air handler needs the chillers.
Written in our own words from the behavior of the Modelica Buildings Library’s multizone air handler plant-request block. Only the chilled-water half is covered: BOPTEST’s air handlers have no hot-water coil.
Interface
Section titled “Interface”| Point | Type | Meaning |
|---|---|---|
TAirSup |
real input, K | Measured supply air temperature |
TAirSupSet |
real input, K | Supply air temperature setpoint |
uCooCoi |
real input, 0 to 1 | Cooling coil valve position |
yChiWatResReq |
integer output | Chilled-water reset requests, 0 to 3 |
yChiPlaReq |
integer output | Chiller plant request, 0 or 1 |
Behavior in brief
Section titled “Behavior in brief”The error is supply air minus setpoint (positive when the air is too warm).
- 3 requests when the error has been above 3 K for 120 s (held while above 2.9 K).
- 2 requests when it has been above 2 K for 120 s (held while above 1.9 K).
- 1 request while a valve latch is set: it sets above 0.95 open and clears below 0.85.
- 0 otherwise; the highest count wins.
- Plant request while a second latch is set: it sets above 0.95 and clears only below 0.10.
Every threshold is strict, and the task spells out the edge instants (a condition already met at the first frame, a latch clearing and setting in one frame).
Validation
Section titled “Validation”- 15 scenarios from the independent reference model, with supply temperatures chosen so every error is exact in binary floating point.
- An 18-block hand-built graph passes all 15; 22 deliberate mistakes (wrong thresholds,
>=for>, missing release bands, wrong priority, latches clearing at the wrong point) each fail at least one.
How it did
Section titled “How it did”- Muse Spark: 3 of 3 runs passed on the first try. An easy spec for the model: the task states every edge, and the sequence maps onto elementary blocks one to one.
- Runs live on BOPTEST, one instance per floor, feeding the plant reset.
Full spec: specs/ahu_chw_requests/spec.md