(Fujitsu) General Australia and New Zealand

Applies To

Single skin rooftop package units using the Multipower v9.31.01 controller variable list.

Reference file:

1008180SM00 RTQ-MK single – Multipower_v9.31.01 – Level 0 End User

This article is based on the attached single circuit / single skin rooftop package unit Modbus variable list. 

Purpose

This article provides guidance for service teams, technical support, controls contractors and BMS integrators when using the Modbus variable list for single skin rooftop package units.

It explains the key Modbus points used for:

• Unit ON/OFF control
• Cooling and heating setpoint control
• Heat/cool mode selection
• Unit status monitoring
• Compressor status and run counters
• Alarm monitoring
• Physical I/O verification

Important Notes

The variable list is marked Level 0 = End User, meaning it contains a limited end-user Modbus point set rather than the full factory parameter list. 

Only approved writable points should be adjusted. Incorrect writes to control points can affect unit operation, heating/cooling mode, setpoint control and BMS operation.

Variable List Structure

The variable list uses the following columns:

Points marked RW can be written to by an approved controller or BMS. Points marked Read are monitoring-only.

Common Writable Control Points

The following are the main writable points generally required for BMS control.

The variable list identifies SC1 and SH1 as the cooling and heating setpoints, with y01 used for system ON/OFF and y03 used for heat/cool selection. 

Key Unit Status Points

The main unit status values are listed under Status var > Chiller Overview.

These points should be used as the primary BMS monitoring values for unit state, alarm condition, operating mode and load demand. 

Expansion Valve Monitoring

The single skin variable list includes read-only expansion valve status points.

Expansion Valve 2 points are also listed, but they may not apply to all single-circuit units. Confirm the unit configuration before adding unused points to the BMS. 

Compressor Monitoring

The list includes compressor status, compressor ageing and compressor start counters.

Compressor Status

The single circuit file also lists Circuit 2 compressor variables; these may be present in the generic variable table but may not be applicable to the installed single-circuit unit. 

Compressor Ageing / Hours

Compressor Start Counters

These values are useful for service history, compressor rotation checks and identifying excessive cycling.

Alarm Register Overview

The alarm section provides alarm labels, descriptions, reset type, whether the alarm is active when the unit is off, and the ADU/bit reference.

Alarm points are shown as register plus bit references, for example:

• 20481 .08
• 20482 .11
• 20491 .06

This means the BMS may need to read the register and decode the specific bit position to identify the alarm. 

Common Alarm Points

Rooftop and Airside Alarms

The following rooftop-related alarms are commonly relevant to field support.

These alarms are especially relevant where the issue relates to airflow, filter restriction, fan proving, damper operation or phase loss.

I/O Configuration

The final pages of the list show physical I/O mappings.

Analogue Inputs

Digital Inputs

Analogue Outputs

Digital Outputs

The I/O section can be used to cross-check BMS values against physical inputs and outputs during commissioning or fault diagnosis. 

Recommended Minimum BMS Point List

For a typical single skin rooftop package unit integration, the following minimum point list is recommended:

BMS Integration Guidance

When integrating the Modbus points into a BMS:

1. Confirm the exact unit model and whether the unit is single circuit or double circuit.
2. Confirm the Modbus register format required by the BMS platform.
3. Confirm whether the BMS uses zero-based or one-based register addressing.
4. Confirm which alarm points require bit-level decoding.
5. Only write to approved writable points such as ON/OFF, heat/cool mode and setpoints.
6. Do not write to read-only status, alarm or physical I/O points.
7. Validate BMS readings against the controller display during commissioning.
8. Avoid adding non-applicable Circuit 2 points for single-circuit units unless required by the controls specification.

Troubleshooting

Escalation Information to Collect

When escalating a Modbus or BMS issue, collect:

• Full unit model number
• Unit serial number
• Variable list file name and revision
• Confirmation that the single skin / single circuit point list is being used
• BMS protocol and hardware details
• Register list configured in the BMS
• Whether the BMS uses zero-based or one-based addressing
• Screenshots of key BMS point values
• Photos of the controller communication wiring
• Active alarms from the unit controller
• Values for A01, A02, A03, A10, A12, A13, A14, A15 and A16