Zone Reheat Control - Carrier VVT Zone Installation And Startup Manual

Sequence of operation

Zone reheat control

The VVT Zone Controller can be configured for one of the following Heat Types to meet the zone's heating
requirements:
•
Modulating Hot Water/Steam
• Two Position Hot Water/Steam
•
Staged Electric Heat (2 stages for Series/Parallel Fan, 3 stages for Single Duct.)
•
Combination Modulating Baseboard/Staged Electric Heat (2 stages for Series/Parallel Fan, 3 stages for
Single Duct.)
All of the above except Combination Modulating Baseboard/Staged Electric Heat can be ducted or non-
ducted (baseboard). For ducted heat and Combination Modulating Baseboard/Staged Electric Heat, an SAT
sensor (33ZCSENSAT) must be installed in the duct downstream of the heat source. The controller has a
configurable Maximum Heating SAT for supply air temperature control. The zone controller monitors the (SAT)
when the terminal's ducted heat is operating.
If the network provides the OAT, heating can be disabled if the OAT rises above the configured Heating
Lockout Temperature.
Modulating Hot Water / Steam Heating Heat – The controller modulates a normally closed or normally open
hot water or steam valve connected to the discharge air heating coil. The valve opens and closes as needed
to meet heating requirements. For ducted heat, the terminal's heat supplements heat from the primary air
source if it is in heating mode and is controlled so that the SAT does not exceed the Maximum Heating SAT
(105°F default). For baseboard heating (non-ducted heat), the valve modulates to keep the zone's
temperature at the heating setpoint.
Two-Position Hot Water / Steam Heating Heat – The controller operates a normally closed or normally open
hot water or steam valve connected to the discharge air heating coil. The valve opens and closes as needed
to meet heating requirements. For ducted heat, the terminal's heat supplements heat from the primary air
source if it is in the heating mode and is controlled so that the SAT does not exceed the Maximum Heating
SAT (105°F default). For non-ducted (baseboard) heating, the valve is controlled to keep the zone's
temperature at the heating setpoint.
Electric Auxiliary Heat – The controller operates 1 or 2 stages of electric heat. For ducted heat, the terminal's
heat supplements heat from the primary air source if it is in the heating mode and is controlled so that the
SAT does not exceed the Maximum Heating SAT (105°F default). For non-ducted (baseboard) electric heat,
the stages are controlled as needed to keep the zone's temperature at the heating setpoint.
Combination Modulating Baseboard / Electric Heat – The controller can modulate a normally closed or
normally open hot water or steam valve connected to a perimeter baseboard radiation system and control up
to 2 stages of ducted electric heat. The valve modulates as needed to meet heating requirements. If the valve
cannot meet the load, electric heat is used. The terminal's electric heater supplements heat from the primary
air source if it is in heating mode and is controlled so that the SAT does not exceed the Maximum Heating
SAT (105°F default).
Parallel Fan Heat On Delay – For Parallel Fan terminals only, the controller has a configurable Parallel Fan
Heat On Delay to save energy. During the delay (15 minute default), only the fan operates to recycle heat
from the ceiling plenum. If the heating requirement is not met by the end of the delay, reheat is enabled.
Fan Heat Off Delay – For fan-powered terminals, the controller has a configurable Fan Off Delay. After the
heating coil de-energizes, the fan continues to run for the length of the delay to deliver to the zone any heat
stored in the coil. The default delay of 2 minutes is optimal for ducted hot water coils. For ducted electric heat
coils, the nominal delay is approximately 1 minute. For baseboard and non-ducted heat, the delay should be
set at 0.
This feature applies to parallel fan terminals in both occupied and unoccupied mode and series fan terminals
in the unoccupied mode if the air source fan is off.
42 VVT Zone Controller