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ESPHome configuration for RS-485 control of Navien Hot Water Heaters

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ESPHome-Navien

ESPHome configuration for RS-485 control of Navien Hot Water Heaters

Common Fields

The first 6 bytes appear to be a packet header. The first two bytes are common to all packets. The next three uniquely identify each of our three packet types. Byte index 5 is the length of the data, not including the header (6 bytes) or the final byte, could be a checksum. In other words, byte index 5 is the length of the packet minus 7 bytes.

Index Value Notes
0 f7 Common to all packets
1 05 Common to all packets
2 Packet id byte 0
3 Packet id byte 1
4 Packet id byte 2
5 Data length
Data
N Checksum

Packet A (from heater)

This packet seems to have information related to water.

Here is a full example packet:

f7 05 50 50 90 22 42 00 00 05 14 72 37 2e 00 00 00 00 00 00 f8 8e 00 00 02 00 00 00 05 00 07 00 00 02 00 00 00 00 00 00 67

And the fields decoded so far:

Index Value Notes
0 f7 Common to all packets
1 05 Common to all packets
2 50 Packet id byte 0
3 50 Packet id byte 1
4 90 Packet id byte 2
5 22 Data length
8 00 Related to recirculation status 0x00, 0x08, 0x20 observed
9 05 System power: high nibble: unknown (values 0 and 0x20 observed); low nibble: 0=off 0x5=on
11 72 Set temp - measured in 0.5 degrees C. 57C in this case
12 37 Heat Exchanger Outlet temp - measured in 0.5 degrees C. 27.5C in this case
13 2e Heat Exchanger Inlet temp - measured in 0.5 degrees C. 27.5C in this case
18 00 Flow rate - measured in 0.1 liters per minute (divide by 10 to get LPM)
24 02 System status. Probably a bitwise field. Partially decoded: display units: 0x08 position: 1=metric 0=imperial. 0x02 position: 1=weekly 0=hotbutton
33 02 If recirculation is enabled/disabled 0x02/0x00

Packet B (from heater)

This packet seems to have information related to gas.

Here is a full example packet:

f7 05 50 0f 90 2a 45 00 0b 01 0c 03 17 00 72 6d 23 00 00 00 00 00 00 00 61 00 00 00 0b 00 1d 00 f6 34 00 00 05 00 00 00 00 00 aa 48 00 00 01 00 b3

And the fields decoded so far:

Index Value Notes
0 f7 Common to all packets
1 05 Common to all packets
2 50 Packet id byte 0
3 0f Packet id byte 1
4 90 Packet id byte 2
5 2a Data length
14 72 Set temp - measured in 0.5 degrees C. 57C in this case
15 6d Outlet temp - measured in 0.5 degrees C. 27.5C in this case
16 23 Inlet temp - measured in 0.5 degrees C. 27.5C in this case
20 00 almost identical to high byte kcal
22 00 Low byte current gas usage in kcal
23 00 High byte current gas usage in kcal
24 61 Total gas usage in 0.1m³ (divide by 10 to get m³; 9.7 cubic meters in this case)

Packet C (from navilink)

This appears to be an announcement packet. It tells the heater there is a navilink attached. The heater uses this to disable local setting of the weekly schedule and instead require setting the schedule from the app.

Here is a full example packet:

f7 05 0f 50 10 03 4a 00 01 55

Packet D (from navilink)

This is the command packet. tested each of the following commands: power off, power on, set temp, hotbutton. Each type of command uses a different field. The navilink app send each command independently, but the format suggests that more than one command could be combined into a single packet. The navilink repeats the on/off/set commands multiple times. For hotbutton presses, it sends the on command twice followed by the off command once.

Here is a full example:

f7 05 0f 50 10 0c 4f 00 0b 00 00 00 00 00 00 00 00 00 0a
Index Value Notes
0 f7 Common to all packets
1 05 Common to all packets
2 0f Packet id byte 0
3 50 Packet id byte 1
4 10 Packet id byte 2
5 0c Data length
8 0b Power: 0x0a=on 0x0b=off
9 00 Set temperature (units of 0.5C: 0x74 is 58C)
11 00 Hotbutton: 0x01=press 0x00=release

Current list of full commands sent from navilink (so you can see the checksums):

  f7 05 0f 50 10 0c 4f 00 0b 00 00 00 00 00 00 00 00 00 0a : off
  f7 05 0f 50 10 0c 4f 00 0a 00 00 00 00 00 00 00 00 00 ce : on
  f7 05 0f 50 10 0c 4f 00 00 74 00 00 00 00 00 00 00 00 ea : set to 58c
  f7 05 0f 50 10 0c 4f 00 00 72 00 00 00 00 00 00 00 00 c4 : set to 57c
  f7 05 0f 50 10 0c 4f 00 00 00 00 01 00 00 00 00 00 00 6a : hotbutton press
  f7 05 0f 50 10 0c 4f 00 00 00 00 00 00 00 00 00 00 00 2a : hotbutton release
  F7,05,0F,50,10,0C,4F,00,00,00,00,10,DF,00,00,00,00,00,3E : recirculation off from app
  F7,05,0F,50,10,0C,4F,00,00,00,00,00,DF,00,00,00,00,00,D4 : recirc off ack?
  F7,05,0F,50,10,0C,4F,00,00,00,00,08,D9,00,00,00,00,00,D0 : recirculation on from app
  F7,05,0F,50,10,0C,4F,00,00,00,00,00,D9,00,00,00,00,00,14 : recirc on ack?

Checksum

The last byte sent could be a checksum value, but the algorithm is currently unknown

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ESPHome configuration for RS-485 control of Navien Hot Water Heaters

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