Writeable Framework

| Overview

The Writable Framework is an enhancement in the CCU ecosystem that enables dynamic synchronization between the Site Manager and the Central Control Unit (CCU). It addresses the increasing operational need to modify entity structures, update port behaviors, and adjust configuration parameters directly from Site Manager without requiring firmware-level changes.

This framework primarily introduces the capability to write values or tags to ports—including those structured as priority-array writable points—allowing greater flexibility and faster adaptation to field requirements.

Minimum Required Version:

CCU Firmware: 4.4.4 or above

| Advantages

Traditionally, any change to entity structure or port configurations required fixed definitions or firmware updates. However, complex field conditions often demand:

Adjusting loop behaviors based on environment or equipment constraints
Modifying tag structures to customize system functions
Enhancing flexibility for integrators to model equipment in real-time
Making on-site modifications without engineering intervention

The Writable Framework allows the Site Manager to send updates to CCU, ensuring both stay synchronized in terms of:

Editable entity structures
Writable priority-array values
Custom sequence interactions

Note: If algorithms operate at the edge level, the Writable Framework does not override the Test signals; always write into Level 2 of the priority array.

| Capabilities

Editable Entity Structure

Operators can modify:

Values on writable ports
Tags or metadata
Priority array structure (for Level 2 inputs such as test signals)

Real-Time Sync

Changes made in Site Manager are pushed to CCU seamlessly, ensuring unified system behavior.

| Use Cases

Loop-Based Cooling/Heating Logic Overrides

The system enables writable interactions within control algorithms.
Example logic scenario:

IF Cooling Loop > Hysteresis (10%)
THEN
    Cooling Stage 1 = ON
    FAN = ON

Cooling-Based Dehumidification

IF Cooling Loop = 0 
AND Zone Humidity > (Humidity Setpoint + Hysteresis)
THEN
    Cooling Stage 1 = ON
    FAN = ON

Water Flow Safety Logic

IF Current Temp < (Cooling Desired – 3.6)
OR Condensation Active
THEN
    Turn OFF CHW Relay (shut water flow)

IF Current Temp > Cooling Desired
AND CHW Relay = OFF
THEN
    Turn ON CHW Relay

These conditions demonstrate how writable signals may be applied to influence control loop execution.

| Physical Layer Capabilities

System / Profile	Relay Outputs	Analog Outputs	Notes
CCU	1–7	1–4	Physical relays available locally
Connect Node	1–8	1–4	Supports extended IO
HS Profile	1–6	1–3	Used in Heat System profiles
HN Profile	1–4	1–4	Supports SSE relays/outputs
SN Profile	1–2	1–2	Supports standard VAV/DAB systems

| Logical Layer Capabilities by System Profile

VAV System

Heating Loop
Cooling Loop
Fan Loop
DCV Loop
Compressor Loop

DAB System

Heating Loop
Cooling Loop
Fan Loop
DCV Loop
DCWB Valve Loop
Compressor Loop

Connect Node Devices

Heating Loop
Cooling Loop
Fan Loop
DCV Loop
Outside Air Final Loop
Economizing Loop
Compressor Loop

VAV Advanced V2 & DAB Advanced V2

Heating / Cooling / Fan Loops
DCV Loop
Compressor Loop

SN Profile (VAV ACB, Parallel, Series, Reheat & DAB)

Heating Loop
Cooling Loop
Normalized Damper Position

HN Profile

Heating Stage
Cooling Stage
Fan Stage

PI Profile

Control Variable

OAO (SN Only)

Economizing Loop
Outside Air Final Loop
DCV Loop

Bypass Damper (SN Only)

Bypass Damper Loop Output

CPU, FCU & UV Profiles

Depending on configuration (CPU, 2-Pipe UV, 4-Pipe UV, HPU, etc.), the writable loops include:

Heating Loop
Cooling Loop
Fan Loop
DCV Damper
Compressor Loop
Economizing Loop
Outside Air Final Loop
Supply Air Tempering Loops

These mappings define how writable values interact with logical control structures in each system profile.

| Restrictions and Considerations

A writable framework cannot override edge-level algorithms.
Test signals write only to Priority Level 2.
Not all profiles support all loop types; mappings depend on hardware capability.
Writable values must adhere to system safety limits to avoid improper equipment operation.

The Writable Framework significantly improves CCU flexibility by allowing Site Manager-driven structural and behavioural updates. With support across multiple profiles and a clear separation between logical and physical layers, it empowers high configurability while maintaining the integrity of underlying algorithms.