Carrier TP-NHP - Manual (Page 46)

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Programmable Fan (programmable models only)
The fan output can be programmed based on period of the day. When
programming for each day and period the fan can be set to On or AUTO. If the
fan button is pressed to change from On to Auto or vice versa when
programmable fan has been enabled, the manual change will only remain in
effect until the next program period, when the programmable fan setting will be
changed per the scheduled setting.
Dry Contact
On the programmable models, the dry contact that can be used for control of an
auxiliary device. The dry contact may be configured to be closed for a specific
number of minutes per hour for each period of the program schedule. This can
be used to operate a ventilator, damper, system blower, or other auxiliary device.
There are two terminals, D1 and D2.
If it is desired to operate a ventilator or other device, the D1 and D2 terminals
can be connected directly to the equipment. This will provide a closed contact
for the specified number of minutes per hour. See Option 19.
If timed control of the system blower is required, the dry contact can be used for
this function. The G terminal can be connected to one of the dry contact
terminals with the other terminal being connected to Rc and/or Rh for timed
control of the fan. Note that this is not the same as programmable fan Option 30.
See Wiring Diagrams for more information.
Relays
This thermostat uses latching relays. When the thermostat loses power, the relays
will remain in their last position until power is restored and all relays are reset to
their correct position. Out of the box, the outputs may appear to be On when the
thermostat is not powered. This is normal. Output states should only be checked
when the thermostat is powered.