Zone Reheat Control - Carrier VVT Zone II Installation And Startup Manual

Sequence of operation

Zone reheat control

The VVT Zone II can be configured for one of the following Heat Types to meet the zone's heating requirements:
•
Modulating Hot Water/Steam
•
Modulating SCR Electric
•
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 satisfy
the zone's 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 (40.5°C) default]. For baseboard heating (non-ducted heat), the valve modulates to keep the zone's
temperature at the heating setpoint.
SCR Electric Heat – The controller modulates an SCR heat output connected to the SCR electric heat control
input. The output increases as needed to satisfy the zone's 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 (40.5°C) default]. For baseboard heating (non-ducted heat), the
SCR heat output 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 satisfy
the zone's 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 (40.5°C) 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 (40.5°C) 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 to satisfy the zone's 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 (40.5°C)
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.
VVT Zone II Controller
Installation and Start-up Guide
48
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