On a Daikin Trailblazer AGZ air-cooled scroll chiller, the MicroTech controller lists each alarm by name in an active alarm list and an alarm log, and each alarm has its own trigger, action and reset rule: some clear on their own once the condition is gone, others must be cleared at the controller or by BAS command. The alarms that point most directly at a part are the sensor faults. On the AGZ-E (Daikin IOM 1206-16), a pressure sensor fault trips below 400 mV or above 4600 mV, and a temperature sensor fault below 340 Ω or above 300 kΩ. The AGZ-F (IOM 1359, R-32) uses a different list, so the two vintages are kept separate below.
How does the AGZ controller show an alarm?
AGZ-E (IOM 1206-16). The MicroTech III controller has a 5-line display, an Alarm button, a Menu button, a Back button and a push-and-roll wheel (p.95). The Alarm button opens three sub-sections: Active Alarms, Alarm Log and Event Log. A + before an entry means active and a - means cleared, and each log keeps the last 50 entries (p.92). The alarm output is on continuously for a unit fault, and cycles five seconds on and off when only one circuit has a circuit fault (p.89).
AGZ-F (IOM 1359). This vintage uses a MicroTech unit controller with a touchscreen HMI (p.22). Press the alarm icon at the top right of the HMI to open the active alarm list. The icon flashes while alarms are active, and the list shows the six highest-priority alarms. The Alarm Log screen can be downloaded as a CSV file from the Trend page (p.45).
Fault, problem, warning or event?
IOM 1206-16 names Faults, Problems and Warnings (p.89) but prints only fault alarms; events are logged separately as not "severe enough to track as alarms" (p.93). IOM 1359 gives each alarm a Type (pp.45-46). Neither manual defines the words. Our reading of the IOM 1359 tables, not Daikin's wording: Fault entries mostly shut down the unit or a circuit, Problem entries keep running with a workaround (backup pump, ignore a fan), and Warning entries mostly ignore an input.
How do you clear an alarm on an AGZ chiller?
- Fix the cause first. IOM 1206-16 says alarms are cleared only if the conditions that initiated them no longer exist (p.92), and most IOM 1359 reset rows read "Alarm trigger no longer exists" (pp.47-52). IOM 1206-16 also cautions that repeated manual clearing without resolving the cause "may damage the chiller" (p.93).
- AGZ-E keypad (p.92). Open Active Alarms and press the wheel. Edit Alm Clr, rotate it to ON and press the wheel. No password is needed. If the cause remains, Alm Clr returns to OFF.
- AGZ-E other ways (p.92). BAS (nviClearAlarms on LON, ClearAlarms on BACnet), or cycle controller power.
- AGZ-F (pp.45-53). Clear from the controller HMI or by BAS command. Auto clearing works only when no alarm that cannot be auto-cleared is active, and the controller allows no more than three auto-clears in one hour.
AGZ-E alarm list (IOM 1206-16, pp.89-92)
| Level | Alarm | Trigger | Action | Reset |
|---|---|---|---|---|
| Unit | PVM/GFP Fault | PVM/GFP input open 1 s (single point power) | Rapid shutdown, lockout | Auto, input closed 5 s |
| Unit | Evaporator Flow Loss | No flow with pump running, or pump start timed out | Rapid stop all circuits | Auto first two times a day, third manual; pump-start case always manual |
| Unit | Evaporator Water Freeze Protect | LWT below freeze set point, with no LWT sensor fault active, longer than recirculation time | Rapid shutdown, lockout | Manual, keypad |
| Unit | Evaporator LWT Sensor Fault | Below 340 Ω or above 300 kΩ, 1 s | Normal stop, lockout | Manual, sensor in range 5 s |
| Unit | Evaporator EWT Sensor Fault | Same limits | None | Auto |
| Unit | Outdoor Air Temperature Sensor Fault | Same limits | Normal stop, lockout | Manual, sensor in range 5 s |
| Unit | External Alarm | Input open 5 s, set as alarm | Rapid shutdown, lockout | Auto, input closed |
| Unit | Evaporator Pump #1 / #2 Failure | Logic switches to the other pump | Backup pump used | Manual |
| Circuit | PVM/GFP Fault | Circuit input off 1 s (multi point power) | Rapid stop circuit | Auto, input closed 5 s |
| Circuit | Low Evaporator Pressure | Freezestat time exceeded, or below 137.9 kPa (20 psi) running, 1 s | Rapid shutdown, lockout | Manual, above 20 psi |
| Circuit | High Condenser Pressure | Above set point 1 s | Rapid shutdown, lockout | Manual |
| Circuit | Mechanical Low Pressure Switch | MLP input off 40 s while running (remote evaporator, microchannel) | Rapid stop circuit | Manual |
| Circuit | Mechanical High Pressure Switch | MHP input off with Motor Protection input on, 1 s | Rapid stop circuit | Manual, MHP input on |
| Circuit | Motor Protection Fault | Motor Protection input off 1 s | Rapid stop circuit | Manual, input on |
| Circuit | Low OAT Restart Fault ("OffNbrRestarts") | Three failed low OAT starts | Rapid stop circuit | Manual |
| Circuit | No Pressure Change After Start | No 1 psi suction drop or 5.1 psi condenser rise in 30 s (second occurrence) | Rapid stop circuit | Manual |
| Circuit | Evaporator Pressure Sensor Fault | Below 400 mV or above 4600 mV, 1 s; or approach below -17°F for 30 s | Rapid shutdown, lockout | Manual, in range 5 s |
| Circuit | Condenser Pressure Sensor Fault | Below 400 mV or above 4600 mV, 1 s | Rapid shutdown, lockout | Manual, in range 5 s |
| Circuit | Suction Temperature Sensor Fault | Below 340 Ω or above 300 kΩ, 1 s (electronic EXV) | Normal shutdown, lockout | Manual, in range 5 s |
| Circuit | Compressor CC / EEXV Module Comm Failure | Module reliability not 0 for 3 s | Rapid shutdown, lockout | Manual, reliability 0 for 5 s |
| Circuit | Failed Pumpdown | Pumpdown over 2 minutes | Shut down circuit | N/A |
Partial list: the External Event, bad-input, Heat Recovery sensor and RapidRestore alarms (p.90) do not stop the unit, and the pressure Hold and Unload entries are events (p.93).
AGZ-F alarm list (IOM 1359, Tables 62 and 64)
| Level | Alarm | Type | Action | Manual clear |
|---|---|---|---|---|
| Unit | Unit PVM/GFP Fault, Evaporator Flow Loss, Evaporator Water Freeze Protect | Fault | Unit shutdown | HMI or BAS |
| Unit | Evaporator LWT Sensor Fault, OAT Sensor Fault | Fault | Unit shutdown | HMI or BAS |
| Unit | Evaporator EWT Sensor Fault | Warning | None | n/a |
| Unit | Evaporator Pump #1 / #2 Failure | Problem | Backup pump is used | HMI or BAS |
| Unit | Transformer Overtemperature Fault, Peripheral Module Comm Failure | Fault | Unit shutdown | HMI or BAS |
| Unit | Transformer Temp Sensor Error | Problem | Transformer unload ignored | HMI or BAS |
| Circuit | Circuit PVM/GFP Fault, Low Evaporator Pressure, High Condenser Pressure, Mechanical High Pressure Switch, Low OAT Restart Fault | Fault | Circuit shutdown | HMI or BAS |
| Circuit | Evaporator Pressure, Condenser Pressure and Suction Temperature Sensor Faults; EEXV Module Comm Failure | Fault | Circuit shutdown | HMI or BAS |
| Circuit | Motor Protection Fault, No Pressure Change After Start, Discharge Temperature Sensor Fault, High Discharge Temperature | Fault | Circuit shutdown | n/a |
| Circuit | DC Fan Fault | Problem | Ignore affected fan | HMI or BAS |
Partial list; Table 62 also has External Alarm, External Event and two bad-input warnings. The detail pages disagree with those tables on some entries: they call Evaporator LWT Sensor Fault and OAT Sensor Fault a Warning (pp.47-48), and Evaporator Pump #1/#2 Failure (p.48) and Transformer Temperature Sensor Error (p.49) a Fault. They also add Low OAT Lockout (p.49), Low Condenser Sat. Temperature (60-minute shutdown) and Low Suction SH Fault (SSH below 3°F for 5 minutes, 30-minute shutdown) (pp.51-52). AGZ-F sensor faults trip when "sensor status is other than '10'" for one second and reset when it returns to "10" (pp.47-52).
Which alarms point at a transducer or sensor?
| Device | AGZ-E (IOM 1206-16) | AGZ-F (IOM 1359) |
|---|---|---|
| Suction pressure transducer | WL1, WL2 (Figure 27, AGZ075-101E schematic, p.19); expected 0.4 to 4.6 V (p.53). Evaporator Pressure Sensor Fault | SCP1, SCP2, ratiometric 0.5-4.5 Vdc (p.24). Evaporator Pressure Sensor Fault |
| Discharge pressure transducer | WH1, WH2 (p.19); 0.4 to 4.6 V. Condenser Pressure Sensor Fault | DCP1, DCP2, ratiometric 0.5-4.5 Vdc (p.24). Condenser Pressure Sensor Fault |
| Suction temperature sensor | ST1, ST2 (p.19); NTC 10k, 340 to 300k Ω (p.53) | SCT1, SCT2, NTC 10k (p.24) |
| Water and outdoor air sensors | EWT, LWT, ambient: NTC 10k (p.53) | EEWT, ELWT, OAT1: NTC 10k (pp.23-24) |
| Discharge temperature sensor | Not listed | DCT1, DCT2, NTC 10k (p.24) |
Matching the Evaporator and Condenser Press inputs to the suction and discharge transducers is our reading of Table 23 and Figure 27, not Daikin's wording. IOM 1206-16 says pressure inputs are 0 to 5 V ratiometric sensors with a nominal 0.5 to 4.5 V range (p.55). The approach trigger exists "to prevent operation if the sensor is reading high but not out of range" (p.91). Our practical advice, not Daikin's: if that alarm returns with the signal in range, check the transducer against a gauge before replacing it.
What does the troubleshooting chart say about parts?
These rows read the same in IOM 1206-16 (pp.114-115) and IOM 1359 (pp.76-77).
| Problem | Possible cause | Corrective step |
|---|---|---|
| Compressor Will Not Run | Defective contactor or coil | Replace |
| Compressor Will Not Run | Liquid line solenoid will not open | Repair or replace solenoid. Check wiring |
| High Discharge Pressure | Fan not running | Check electrical circuit and fan motor |
| Low Suction Pressure | Fouled liquid line filter drier | Check pressure drop across filter drier. Replace |
| Low Suction Pressure | Expansion valve malfunctioning | Repair or replace and adjust for proper superheat |
| Compressor Will Not Stage Up | Faulty sensor or wiring | Replace |
| Compressor Staging Intervals Too Short | Faulty water temperature sensor | Replace |
| Motor Overload Relays or Circuit Breakers Open | Loose power wiring or burnt contactors | Check all connections and tighten, replace contactors |
| Compressor Thermal Protection Switch Open | Compressor mechanical failure | Replace compressor |
Parts involved
| Component | Role in this issue | Where to find it |
|---|---|---|
| Suction pressure transducer | WL1/WL2; Evaporator Pressure Sensor Fault. Neither manual gives a part number, so match yours | 910153379 — Low Pressure Transducer Replacement |
| Discharge pressure transducer | WH1/WH2; Condenser Pressure Sensor Fault. Match the number on yours | 910153045 — High Pressure Transducer |
| Suction temperature sensor | ST1/ST2; Suction Temperature Sensor Fault. The title does not name an AGZ model | 910121228 — Suction Line Temp Sensor |
| Water and outdoor air sensors | EWT, LWT and OAT sensor faults | Daikin Parts for Daikin Chillers |
| High pressure switch, contactors, fan motors, EXV, modules | MHP, Motor Protection, DC Fan and module comm alarms; model-specific | Daikin Parts for Daikin Applied |
Scope: This article covers Daikin IOM 1206-16 (Trailblazer AGZ, E vintage, 30 to 241 tons, HFC-410A, MicroTech III, September 2022) and IOM 1359 (Trailblazer AGZ, F vintage, 30 to 245 tons, R-32, January 2024). Values from one vintage do not carry over to the other or to other Daikin chillers. The products above are examples listed by their live titles, not a fit confirmation.
Before you order
Read the model and serial number from the nameplate and confirm whether the unit is an E or F vintage. Daikin Applied and McQuay numbers often refer to the same part; see Daikin Applied, McQuay and Daikin-McQuay part numbers. For water-cooled screw chillers, see Daikin MicroTech III Evaporator Flow Loss and Freeze Protect Alarms. Or contact us at help@totalhvacparts.com or 302-219-4994 with the model, serial number and exact alarm text to confirm fit.
Frequently Asked Questions
How do I clear an alarm on a Daikin AGZ Trailblazer chiller?
On the AGZ-E, press the Alarm button, open Active Alarms and set Alm Clr to ON (IOM 1206-16, p.92); BAS commands and a controller power cycle also clear alarms. On the AGZ-F, clear from the HMI or by BAS command. On the AGZ-E, an alarm clears only once its trigger is gone (p.92).
What does Evaporator Pressure Sensor Fault mean on a Daikin AGZ chiller?
On the AGZ-E, the suction transducer signal is below 400 mV or above 4600 mV for one second, or the evaporator approach is below -17°F for 30 seconds; the circuit shuts down and locks out (IOM 1206-16, p.91). On the AGZ-F, the sensor status is other than "10" (IOM 1359, p.52).
Why does my Daikin AGZ chiller keep tripping on Evaporator Flow Loss?
On the AGZ-E, a flow loss with the pump running auto-resets the first two times in a day and the third needs a manual reset (IOM 1206-16, p.89). Our practical advice, not Daikin's: if the chiller restarts twice and then stays off, check the flow switch, pump and strainer before clearing it again.
Sources
- Daikin IOM 1206-16, Trailblazer Air-Cooled Scroll Compressor Chillers, Model AGZ, E Vintage (September 2022) (schematic p.19, I/O pp.53-55, alarms pp.89-94, controller p.95, troubleshooting pp.114-115)
- Daikin IOM 1359, Trailblazer Air-Cooled Scroll Chillers, Model AGZ, F-Vintage, R-32 (January 2024) (controller pp.22-24, alarms and events pp.45-54, troubleshooting pp.76-77)
- Live product titles for the parts listed above, as shown on each product page
Air-cooled chillers involve high voltage, pressurized refrigerant and rotating fans. Service should be performed only by qualified refrigeration personnel, following the Daikin manual for your unit and your facility's lockout/tagout procedures.