CRAH_UNIT_CTRL
CRAH unit control: supply-air temperature PI on the chilled-water valve, EC-fan speed limiting, and latched water isolation.
When to use it
Use CRAH_UNIT_CTRL when a computer-room air handler cools a data hall from a chilled-water coil, its supply-air temperature is the controlled variable, and a leak or service event must be able to take the unit off the water and keep it off until an operator clears it.
Interface
The published port signature. This is the whole of what the block exposes to your program — the implementation body is not shown here and ships with the download.
Inputs
| Port | Type | Unit |
|---|---|---|
| ENABLE | BOOL | — |
| SAT_PV | REAL | degC |
| RAT_PV | REAL | degC |
| AIR_T_OK | BOOL | — |
| SAT_SP | REAL | degC |
| FAN_DMD_PCT | REAL | % |
| FAN_MIN | REAL | % |
| FAN_MAX | REAL | % |
| KP | REAL | %/K |
| TI | REAL | s |
| VALVE_FAIL_PCT | REAL | % |
| SAT_HI_DEV | REAL | K |
| SAT_HI_TMO | TIME | — |
| ISOLATE | BOOL | — |
| ACK | BOOL | — |
Outputs
| Port | Type | Unit |
|---|---|---|
| SAT | REAL | degC |
| RAT | REAL | degC |
| VALVE_PCT | REAL | % |
| FAN_PCT | REAL | % |
| VALID | BOOL | — |
| ALM_ISOLATED | BOOL | — |
| ALM_T_FAULT | BOOL | — |
| ALM_SAT_HIGH | BOOL | — |
| ALM_CFG_ERR | BOOL | — |
IEC 61499 event interface
EI INIT, REQ·EO INITO, CNF
Validation evidence
- Tests
- 8
- Simulated scans
- 445
- Simulator
- v0.1.0
Complete IEC 61131-3 implementation with a published test suite that runs on the vplant simulator. The counts above are that suite, executed on this build.
- Conforms to IEC 61131-3
- Conforms to IEC 61499
Download CRAH_UNIT_CTRL — free
Create a free Ri Tech account to download the block. You get the Structured Text body, the Rockwell Add-On Instruction (.L5X), the Schneider Control Expert DFB (.XDB), PLCopen XML, the IEC 61499 function block type (.fbt) and the datasheet.
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Source is never published on this page. The implementation is released to a signed-in Ri Tech account — free of charge, but never anonymously.