UNT-IOM-6 41
Tracer
®
ZN.010
and ZN.510
Operating
Information
Power-Up Sequence
Entering Water
Temperature
Sampling Function
When 24 VAC power is initially applied to the Tracer
®
ZN.010 or
ZN.510, the following sequence occurs:
1. All outputs are controlled off.
2. Tracer
®
ZN.010 and ZN.510 reads all input values to detemine
initial values.
3. The random start time (0-25 seconds) expires.
4. Normal operation begins.
Both Tracer
®
ZN.010 and ZN.510 use an entering water temperature
sampling function to test for the correct water temperature for the unit
operating mode. For all applications not involving changeover, the
water temperature does not effect the unit operation.
The entering water temperature sampling function opens the main
hydronic valve, waits no more than three minutes to allow the water
temperature to stabilize, then measures the entering water tempera-
ture to see if the correct water temperature is available.
The entering water must be five degrees or more above the space
temperature to allow hydronic heating and five degrees or more below
the space temperature to allow hydronic cooling.
If the correct water temperature is available, the unit begins normal
heating or cooling operation. If the measured entering water tempera-
ture is too low or high, the controller closes the valve and waits 60
minutes before attempting to sample the entering water. Reference
Table 4.
Table 4. Unit Mode as Related to Water Temperature
Unit Type EWT Sensor Required? Coil Water Temperature
2-pipe changeover Yes
4-pipe changeover Yes
2-pipe heating only No
2-pipe cooling only No
4-pipe heat/cool No
• Can cool if:
space temp - EWT
≥ 5 deg F
• Can heat if:
EWT - space temp
≥ 5 deg F
• Can cool if:
space temp - EWT
≥ 5 deg F
• Can heat if:
EWT - space temp
≥ 5 deg F
Hot water assumed
Cold water assumed
•Cold water assumed in main coil
•Hot water assumed in aux. coil
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