Best Practices

Best Practices (Connect / Sync)

On every connection, synchronize host state with the thermostat. After that, rely on COS (and occasional reads). Per the guide, items 17–20 are only required if the corresponding functionality is implemented in your driver.

Sync (Status attribute 0x02) can replace many individual reads: write 0x01 to dump all subscribed COS messages, thermostat errors, and a Sync-complete COS.

Recommended connect checklist

#	Action	How
1	Manage COS subscriptions	Read/write Status / COS (0x07/0x01) — enable only what you use
2	Temperature scale	Setup / Scale
3	Set date & time	Setup / Date and Time — at least monthly
4	Available modes / IAQ	Control / Thermostat & IAQ Available
5	Current setpoints & mode	Control / Setpoint & Mode — hide unused SP per mode
6	Deadband	Installer Settings — enforce before dual-SP writes in Auto
7	Hum / dehum setpoints	Control 3–4 if available from step 4
8	Fresh air	Control 5 if available
9	Air cleaning	Control 6 if available
10	Schedule enable / program	Scheduling 1 & 3 — or disable onboard schedule and drive externally
11	Hold status	Scheduling 4
12	Thermostat equipment status	Status 6
13	IAQ equipment status	Status 7 if available
14	Support modules	Sensors 3
15	Sensors + multi-stat ODT	Sensors 2; Written ODT (5.4) < every 10 minutes
16	Away	Installer Away enable + Scheduling Away settings / hold
17	Heat Blast	If installer-enabled; Scheduling 5
18	Service reminders	Alerts 1 (if installer-enabled)
19	Hi/Lo temp & RH alerts	Alerts 2 at power-up
20	Name / messages	Identification 5; Messaging 1–2

Deadband

• In Auto, heat and cool must stay at least deadband apart (default 3 °F).
• Example: Heat 70, Cool 73, deadband 3 → lowering cool to 72 requires lowering heat to 69.
• Thermostat may auto-correct and send COS when mode changes to Auto with a conflict.
• Dual-setpoint writes that violate deadband may NACK or accept with modification of the non-active SP (see notes on partial vs full writes).

Multi-thermostat outdoor temperature

1. Read installer outdoor sensor mode: Not installed / Installed / Automation.
2. Source stats with real outdoor sensors provide controlling outdoor temp.
3. Write Written Outdoor Temperature to Automation stats more often than every 10 minutes.
4. If no update for 10 minutes, Automation ODT is treated as timed out.

Schedule strategies

1. Use the thermostat’s 7-day / 4-event program and edit via Schedule Day, or
2. Set schedule non-programmable and drive setpoints/fan from the automation system.

Hold notes

• Cancel: hold type = Disabled, other fields Null.
• Temporary / Vacation need end date/time fields populated when active.
• Away uses Away Settings setpoints/fan (not necessarily in the hold packet the same way).

scrypted-aprilaire today

Connect path roughly: read MAC + model + name + IAQ available → write COS vector → Sync after discovery. Gaps vs this checklist are tracked in Implementation Backlog.