United Technologies Carrier Unit Vent Open Integration Manual page 24


Fire/Smoke Detector (FSD) is Normal

OAT is less than the heating lockout temperature

If occupied, the SPT is less than the occupied heating setpoint

If unoccupied, the SPT is less than the unoccupied heating setpoint
If all the above conditions are met, the heating outputs are energized as required, otherwise they are de-
energized. If the heating is active and the SAT approaches the maximum SAT limit, the heating valve modulates
closed, or the F&B damper moves to the coil bypass position. For electric heating, if the SAT rises above the
configured Maximum SAT value minus 10 °F (5.5 °C), the fan is indexed to a higher speed. If this is insufficient
and the SAT continues to approach the maximum limit, the EH heating stages are proportionally disabled. After
the electric heater stage is turned off, it may be restarted again until after the supply air temperature falls below
the maximum supply air temperature limit. There is a minimum off-time for the electric heater stage to protect
against excessive cycling.
The configuration screens contain the Max SAT parameter as well as Heating Lockout based on outdoor air
temperature (OAT). Both can be adjusted to meet various specifications.
Modulating Hot Water/Steam Heating - The control can operate a modulating (0-10 Vdc or 2-10 Vdc) type, NO or
NC, hot water or steam valve, connected to the heating coil of the unit and supplied by a boiler in order to
maintain the desired heating setpoint. The valve is controlled to maintain the Heating Control Setpoint during
heating and will not exceed the Maximum Heating SAT limit. If the fan is off or a fan failure alarm occurs, the
valve modulates to maintain the Supply Air Temperature at the configured Fan Off Value.
Face & Bypass Hot Water/Steam - The control can operate a modulating (0-10 Vdc or 2-10 Vdc) type F&B damper
and an optional 2-position NO or NC heating valve in order to maintain the desired heating setpoint. The damper
modulates to maintain the SAT at the calculated Heating Control Setpoint. The valve opens when heating is
required (and the water is suitable if 2-pipe changeover). The control will prevent the SAT from exceeding the
Maximum Heating SAT limit.
Electric Heat - The control can operate up to 3 stages (1 stage default) of electric heat in order to maintain the
desired heating setpoint. The heat stages are controlled to maintain the Heating Control Setpoint during heating
and will not exceed the Maximum Heating SAT. Stage cycling is subject to a 2 minute minimum off-time to
prevent excessive cycling (30 seconds for stage #1). The number of electric heat stages is limited so that the total
number of combined fan speeds and electric heat stages equal 4.
Combination Heating - The control can operate the modulating hot water heat or the Face & Bypass Hot Water
heat (with a suitable 2-position valve plus electric heat) in order to maintain the desired heating setpoint. The non-
electric heat is used to meet the heating requirements in the space when the changeover mode is heat. The
electric heater is used when the changeover mode is cool. If the fan is off and the changeover mode is heat, the
non-electric heat is controlled to maintain the Supply Air Temperature at the configured Fan Off Value.
Unit Ventilator
Integration Guide
21
Communications wiring
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