18
UNT Controller—Unitary (UNT) Controller
IMPORTANT: Any individual binary output (triac) can drive up to
800 mA when you limit the total 24 VAC power
draw. You must limit the power draw of a controller
and its load to avoid heat dissipation problems.
The total 24 VAC power draw of a UNT installed in
an ENC100 or similar size box must be limited to a
maximum of 40 VA.
The total 24 VAC power draw of a UNT mounted in
an open air environment must be limited to a
maximum of 75 VA.
Tables 5 and 6 will assist you in determining the total 24 VAC power draw
of your system.
Table 5: UNT Power and Load Specifications
System Loads Power Draw
UNT with Sensors/Transmitters
10 VA (400 mA)
25 VA for UNT120/121 (due to
heater)
BO Load
Relay, Contactor, Solenoid, Incremental Actuator*
Maximum allowable load for any individual binary
output (triac) is 19 VA** (800 mA at 24 VAC).
Minimum required load for each binary output
(triac) used is 1.2 VA (50 mA at 24 VAC).
Relay loads less than 50 mA may cause triac/relay
chattering. If necessary, use a 1k ohm, 2 watt
resistor across the relay coil.
Triac BOs cannot drive loads which use DC
currents, such as a device which has a full-wave
rectifier. Triacs can drive only AC resistive or
inductive loads, i.e., AC relays, contactors, and
actuator motors. If the driving of a DC device is
required, a pilot relay must be used to isolate the
triac.
Refer to specific product
documentation.
AO Load
Actuator
Maximum allowable load for each AO is 10 mA
@ 10 VDC with a minimum load resistance of
1,000 ohms.
See Table 6.
Zone Terminal or CBLPRO
1.2 VA (50 mA)
* Actuator VA requirements found in Table 6.
**With total controller power limited as described previously.
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