Lochinvar 151 Field wiring continued, Tank thermostat, Low gas pressure switch, Tank sensor

	Installation & Operation Manual
8 Field wiring (continued)
Tank thermostat	Low gas pressure switch

1.Connect the tank thermostats (isolated contact only) to the tank thermostat contacts as shown in FIG. 8-3.

Tank sensor

1.By installing a tank sensor, the SMART SYSTEM control can perform the tank thermostat function. The SMART SYSTEM control automatically detects the presence of this sensor and generates a DHW call for heat when the tank temperature drops 6°F (3°C) below the tank set point and finishes the call for heat when the tank temperature reaches 3°F (1.5°C) above the tank set point.

2.The tank sensor TST20015 is the only sensor suitable for use with the SMART SYSTEM control. Connect the sensor leads to the Tank Sensor terminals on the Low Voltage Connection Board (FIG. 8-3). Consult the tank manufacturer for application and performance when

used with any other indirect tank.

Louver relay

If louvers need to operate when the water heater fires, they can be controlled by this output. Connect these terminals to a 24 VAC relay coil, which is wired to operate the louvers (FIG. 8-3).

Louver proving switch

When the operation of the louvers needs to be verified before the water heater fires, remove the jumper wire from these terminals and connect them to the normally open contacts on its proving switch (FIG. 8-3).

High gas pressure switch

If a switch is provided to detect excessive gas pressure, remove the jumper wire from the terminals on the connection board, and then connect them to its normally closed contacts (FIG. 8-3).

1.If a switch is provided to detect low gas pressure, remove the jumper wire from the terminals on the connection board and connect them to its normally open contacts (FIG. 8-3).

2.If both a high and low gas pressure switch are used, connect their respective contacts in series, and connect them to the terminals on the connection board (FIG. 8-3).

NOTICE	See Section 7 - Gas Connections for a detailed
	explanation regarding high and low gas
	pressure switch operation.

Flow switch

1.A flow switch is used to guarantee flow through the water heater before allowing it to fire. The flow switch must be installed at the water heater outlet.

2.Connect these terminals to the normally open contacts on the flow switch (FIG. 8-3).

Rate output

This output provides a 0 - 10V signal that is proportional to the firing rate of the water heater. This may be used by a BMS system to monitor the actual rate of the water heater.

ModBus

When the optional ModBus interface module is installed, the RS-485 ModBus cable is connected to these terminals. Use shielded, 2-wire twisted pair cable. If desired, the shield can be connected to ground by installing a jumper wire between terminals 1 and 3 on connector X5 on the optional ModBus interface module.

Water heater Building Management System (BMS)

1.An external control may be connected to control either the firing rate or the set point of the water heater. If the external control uses a set of contacts to enable the water heater, connect the contacts to the Tank Thermostat terminals. Otherwise, the SMART SYSTEM control will be enabled by the 0-10V signal.

2.Make sure the ground terminal is connected to the ground output terminal of the external control, and the 0 - 10 VDC terminal is connected to the 0 - 10 VDC terminal of the external control.

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