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

Sequence of operation

Zone reheat control

The VAV Zone II 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 VAVB3 with Series/Parallel Fan, 3 stages for Single duct. VAVB1 is 1 stage
only.)

Combination Modulating Baseboard/Staged Electric Heat (2 stages) (2 stages for VAVB3 with Series/Parallel
Fan, 3 stages for Single Duct. VAVB1 is 1 stage only.)
All of the above except Combination Modulating Baseboard/Staged Electric Heat can be ducted or non-ducted
(baseboard). For ducted type heat, the controller has a configurable Maximum Heating SAT for supply air
temperature control. The controller monitors the SAT when the terminal's ducted heat operates.
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 any heat from the primary air
source, but the terminal's SAT is controlled so that it does not exceed the Maximum Heating SAT (95°F [35°C]
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 satisfy
the zone's heating requirements. For ducted heat, the terminal's heat supplements any heat from the primary air
source, but the terminal's SAT is controlled so that it does not exceed the Maximum Heating SAT (95°F [35°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, 2, or 3 stages of electric heat. For ducted heat, the terminal's
heat supplements any heat from the primary air source, but the terminal's SAT is controlled so that it does not
exceed the Maximum Heating SAT (95°F [35°C] default). For non-ducted (baseboard) electric heat, the stages
are controlled as needed 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 (95°F [35°C] default). For baseboard heating (non-ducted heat), the SCR
heat output modulates 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 satisfy the zone's heating requirements. If the valve
cannot meet the load, then the terminal's ducted electric heat is used. The terminal's electric heater supplements
any heat from the primary air source, but the terminal's SAT is controlled so that it does not exceed the Maximum
Heating SAT (95°F [35°C] default).
CV Modulating Heat – The controller can modulate a normally closed or normally open hot water or steam or
steam valve connected to a perimeter baseboard radiation system or discharge air heating coil. The valve
modulates as needed to keep the zone's temperature at the heating setpoint. For ducted applications, the
terminal's SAT is controlled so that it does not exceed the Maximum Heating SAT (95°F [35°C] default). (Used
primarily on single-duct terminals with ducted modulating hot water or steam heat in health care [hospital]
applications, where discharge air temperature swings may be problematic. CV Modulating Heat may also be used
in all non-ducted modulating heating applications.)
VAV Zone II Controllers
Installation and Start-up Guide
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