HVAC communication bus decoders and corresponding methods
In exemplary embodiments, HVAC communication bus decoders and corresponding methods are disclosed. In an exemplary embodiment, an HVAC communication bus decoder includes a control circuit having an input for coupling to an HVAC communication bus and one or more relays each having an output for coupling to a legacy HVAC system monitoring device. The control circuit is configured to read one or more messages transmitted on the HVAC communication bus, decode the one or more messages to determine a desired mode of operation called for by a thermostat connected to the HVAC communication bus, and energize at least one of the one or more relays to emulate a corresponding legacy HVAC signal representing the mode of operation called for by the thermostat to be provided to the legacy HVAC monitoring device.
1. An HVAC communication bus decoder comprising:
a control circuit having an input for coupling to an HVAC communication bus; and
one or more relays each having an output for coupling to a legacy HVAC system monitoring component;
wherein the control circuit is configured to:
read one or more messages transmitted on the HVAC communication bus;
decode the one or more messages to determine a desired mode of operation called for by a thermostat connected to the HVAC communication bus; and
energize at least one of the one or more relays to emulate a corresponding HVAC legacy signal representing the mode of operation called for by the thermostat to be provided to the legacy HVAC system monitoring device.
2. The decoder of claim 1 , wherein the legacy HVAC signal is a 24VAC signal.
3. The decoder of claim 1 , further comprising:
a common input terminal for coupling to a common line of the HVAC communication bus;
a supply input terminal for coupling to a voltage supply line of the HVAC communication bus; and
a first detection input terminal for coupling to a first communication line of the HVAC communication bus.
4. The decoder of claim 3 , further comprising a second detection input terminal for coupling to a second communication line of the HVAC communication bus.
5. The decoder of claim 1 , further comprising:
a common output terminal for coupling to a common input of the legacy HVAC system monitoring device;
a supply output terminal for coupling to a voltage supply input of the legacy HVAC system monitoring device; and
a first thermostat call output terminal for coupling to a thermostat call input of the legacy HVAC system monitoring device.
6. The decoder of claim 5 , wherein:
the first thermostat call output terminal is a cool thermostat call output terminal for coupling to a cool thermostat call input of the legacy HVAC system monitoring device;
the decoder further comprises:
a heat thermostat call output terminal for coupling to a heat thermostat call input of the legacy HVAC system monitoring device; and
a fan thermostat call output terminal for coupling to a fan thermostat call input of the legacy HVAC system monitoring device.
7. The decoder of claim 6 , further comprising a supply input terminal for coupling to a voltage supply line of the HVAC communication bus, wherein the one or more relays include:
a first relay coupled between the supply input terminal and the cool thermostat call output terminal;
a second relay coupled between the supply input terminal and the heat thermostat call output terminal; and
a third relay coupled between the supply input terminal and the fan thermostat call output terminal.
8. The decoder of claim 7 , wherein:
the control circuit is coupled to the first detection input terminal;
the control circuit is configured to:
activate the first relay in response to decoding a call for cool on the HVAC communication bus;
active the second relay in response to decoding a call for heat on the HVAC communication bus; and
activate the third relay in response to decoding a call for fan on the HVAC communication bus.
9. The decoder of claim 1 , wherein the control circuit is configured to detect a configuration of HVAC system equipment components connected to the HVAC communication bus.
10. The decoder of claim 1 , further comprising a power supply coupled between a voltage supply line of the HVAC communication bus and the control circuit, the power supply configured to receive a 24VAC signal from the voltage supply line and provide a 5VDC bias supply to the control circuit.
11. The decoder of claim 1 , wherein:
the control circuit comprises a microprocessor; and
the control circuit is configured to read the one or more messages passively without sending signals out on the HVAC communication.
12. An HVAC system comprising:
a communicating thermostat;
an indoor unit;
an outdoor unit;
an HVAC communication bus coupled to the thermostat, the indoor unit, and the outdoor unit;
a legacy HVAC system monitoring device; and
a decoder coupled between the HVAC communication bus and the legacy HVAC system monitoring device, the decoder configured to:
read one or more messages transmitted on the HVAC communication bus;
decode the one or more messages to determine a desired mode of operation called for by the thermostat; and
energize one or more relays to emulate a corresponding legacy HVAC signal representing the mode of operation called for by the thermostat to provide the emulated signal to the legacy HVAC system monitoring device.
13. The HVAC system of claim 12 , wherein the decoder is configured to read the one or more messages passively.
14. The HVAC system of claim 12 , wherein the legacy HVAC signal is a 24VAC signal, and wherein the one or more relays includes:
a first relay coupled to a cool thermostat call input of the legacy HVAC system monitoring device;
a second relay coupled to a heat thermostat call input of the legacy HVAC system monitoring device; and
a third relay coupled to a fan thermostat call input of the legacy HVAC system monitoring device.
15. A method of decoding an HVAC communication bus, the method comprising:
reading one or more messages transmitted on the HVAC communication bus;
decoding the one or more messages to determine a desired mode of operation called for by a thermostat connected to the HVAC communication bus;
energizing one or more relays to emulate a corresponding legacy HVAC signal representing the mode of operation called for by the thermostat; and
providing the emulated signal to a legacy HVAC system monitoring device.
16. The method of claim 15 , wherein reading comprises reading the one or more messages passively without sending signals out on the HVAC communication bus.
17. The method of claim 15 , wherein:
the legacy HVAC signal is a 24VAC signal; and/or
decoding includes detecting a configuration of HVAC equipment components connected to the HVAC communication bus.
18. The method of claim 15 , wherein energizing includes energizing a first relay coupled to a cool thermostat call input of the legacy HVAC system monitoring device when a call for cool is decoded on the HVAC communication bus.
19. The method of claim 18 , wherein energizing includes energizing a second relay coupled to a heat thermostat call input of the legacy HVAC system monitoring device when a call for heat is decoded on the HVAC communication bus.
20. The method of claim 19 , wherein energizing includes energizing a third relay coupled to a fan thermostat call input of the legacy HVAC system monitoring device when a call for fan is decoded on the HVAC communication bus.