AIR
FLOW
CW TO OPEN, CCW TO CLOSE
AIR
FLOW
CCW TO OPEN, CW TO CLOSE
Fig. 7 — Damper Configuration
Connect the Power Transformer — An individual, field-supplied, 24 vac power transformer is recommended for each zone controller. If multiple zone controllers are powered from one power transformer (100 va maximum for UL [Under- writers’ Laboratories] Class 2 conformance), maintain polarity on the power input terminals. All transformer secondaries are required to be grounded. Use only stranded copper conductors for all wiring to the zone controller. Wiring connections must be made in accordance with NEC (National Electrical Code) and local codes. Ground the transformer at the transformer lo- cation. Provide an 18-gage, green, chassis ground wire at the terminal.
The power supply is 24 vac ± 10% at 40 va (50/60 Hz).
For 33ZCVAVTRM zone controllers, the power require- ment sizing allows for accessory water valves and for electric heat contactor(s). Water valves are limited to 15 va on both two-position and modulating hot water. The electric heat con- tactor(s) are limited to 10 va (holding) each.
For 33ZCFANTRM zone controllers, the power require- ment sizing allows for accessory water valves and for the fan contactor. Water valves are limited to 8 va on both two-position and modulating hot water. The fan contactor is limited to 11 va (holding).
NOTE: If a water valve or electric heat contactor exceeds these limits, or external contactors are required for electric heat, then it is recommended a 60 va transformer be used. The maximum rating for any output is 20 va.
NOTE: Do not run sensor or communication wiring in the same conduit with line-voltage wiring.
NOTE: An accessory conduit box (part no. 33ZCCONBOX) is available for conduit wiring connections to the zone controller.
Perform the following steps to connect the power transformer:
1.Install the field-supplied transformer in an electrical enclosure that conforms to NEC and local codes.
2.Connect 24 vac from the transformer as shown in the applicable wiring diagram (Fig. 8A-J).
Connect Airflow Pickups — The zone controller de- termines velocity pressure by obtaining the difference between high and low duct pressure from two airflow pickups. The pickups are connected to barb fittings on the zone controller with 1/4-in. polyethylene tubing. All piping for this purpose must conform to local codes.
Figure 9 indicates the positions of the two barb fittings.
Perform the following steps to install and connect the air- flow pickups:
1.Select a location on the air handler’s supply air duct where the airflow pickups will be installed. The loca- tion should be one where there are at least three duct diameters of straight duct upstream of the pickups. If this requirement is not met, stable airflow measure- ments may not be possible.
2.Mount the field-supplied airflow pickup(s) in the duct, following the manufacturer's directions. Two individ- ual pickups may be used, one for high pressure airflow and one for low pressure airflow. A dual pickup, which combines the two functions, may also be used. When using individual pickups, make sure that the one for high pressure airflow faces upstream, in the direction the air is coming from, and the one for low pressure airflow faces downstream, in the direction the air is going to.
3.Use field-supplied 1/4-in. tubing (rated for the applica- tion) to connect the high pressure airflow pickup to barb fitting P1 on the pressure transducer. At the zone controller, the P1 fitting is on the side with the filter installed. Be careful to avoid sharp bends in the tubing, because malfunctions may occur if the tubing is bent too sharply. Use at least 2 ft of tubing for reading stability.
4.Use field-supplied 1/4-in. tubing (rated for the applica- tion) to connect the low pressure airflow pickup to barb fitting P2 on the pressure transducer. Be careful to avoid sharp bends in the tubing, because malfunctions may occur if the tubing is bent too sharply. Use at least 2 feet of tubing for stability.
