Installation Manual

E87
- Heat pump can have at most one
auxiliary heat wire
The Nest Thermostat was previously setup as a single fuel system with
auxiliary heat, but it’s detecting W1 and * (W3) wires that aren’t supported in
that configuration.
E88
- Heat pump can have at most one
auxiliary heat wire
The Nest Thermostat was previously set up as a single fuel system with
auxiliary heat, but it’s detecting AUX/W2 and * (W3) wires that aren’t supported
in that configuration.
E89
- Y2 wire without Y1 wire
The Nest Thermostat is physically detecting a Y2 wire but not a Y1 wire that is
required for 2 stage conventional cooling systems or 2 stage heat pumps.
E90
- W3 wire without W2/AUX wire
The Nest Thermostat is physically detecting a * (W3) wire but not a W2/AUX
wire that is required for 3 stage conventional heating systems.
E91
- E wire without O/B wire
The Nest Thermostat is physically detecting a * (E) wire but not an O/B wire.
O/B is a heat pump wire and Nest only supports the use of emergency heat
with heat pump systems.
E92
E93
E94
E95
E96
E97
E98
E99
E100
E101
- Your Nest may have tripped an internal
fuse and Nest needs to be replaced
The Nest Thermostat either has wires that aren't fully inserted into the
connectors or has tripped an internal fuse.
E102
E103
E104
E105
E106
E107
E108
- The Nest Thermostat has an
overcurrent error
The Nest Thermostat may be wired incorrectly, or your system may be
incompatible.
E109
- G2 detected. G1 wire is also required
The Nest Thermostat is physically detecting a G2 (fan) wire in the Y2
connector, but it’s not detecting a wire in the G connector. Both wires are
required for a multi-speed fan.
E110
- G2 wire detected. Remove W2/AUX
wire
The Nest Thermostat is physically detecting a wire in the W1 connector, a wire
in the AUX/W2 connector, and a G2 (fan) wire in the Y2 connector. This
indicates you have more than one stage of heat and more than one fan speed.

The Nest Thermostat does not support multiple stages of heat and multiple fan
speeds at the same time.
E111
- G2 wire detected. Remove E wire
The Nest Thermostat has detected a G2 (fan) wire in the Y2 connector, and an
emergency heat wire in the connector. The Nest Thermostat doesn’t support a
multi-speed fan and emergency heat together.
E112
- G wire detected. G1 and G2 also
required
The Nest Thermostat is physically detecting a G3 (fan) wire in the connector,
but it isn’t detecting a G2 (fan) wire in the Y2 connector or a wire in the G
connector. All three wires are required for a three speed fan.
E113
- G2 and O/B wire conflict
The Nest Thermostat has detected a G2 (fan) wire in the Y2 connector, and a
wire in the O/B connector. This wiring indicates a multi-speed fan and a heat
pump. The Nest Thermostat doesn’t support this kind of system.
N71
- Power wire Rc detected. Not
connected
The Nest Thermostat isn’t electrically detecting the Rc wire, but one is
connected to the Nest base.
30