Trane LO Operating Information, Power-UpSequence, Entering Water Temperature Sampling Function

Tracer® ZN.010

and ZN.510

Operating

Information

Power-Up Sequence

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.

Entering Water

Temperature

Sampling Function

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	· Can cool if:
		space temp - EWT ³ 5 deg F
		· Can heat if:
		EWT - space temp ³ 5 deg F

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 ³ 5 deg F · Can heat if:

EWT - space temp ³ 5 deg F

Hot water assumed Cold water assumed

·Cold water assumed in main coil ·Hot water assumed in aux. coil

UNT-IOM-6 41