Crestron electronic 2, 3.5 Low voltage connections, Enable, Outdoor temperature sensor, ModBus

7 Field wiring

Low voltage connections

1.Route all low voltage wires through the knockouts in the rear of the boiler, as shown in FIG. 7-2.

2.Connect low voltage wiring to low voltage connection board as shown in FIG. 7-3 on page 38 of this manual and the boiler wiring diagram.

Figure 7-2Routing Field Wiring

LOW VOLTAGE
WIRING KNOCKOUTS	LINE VOLTAGE
	WIRING KNOCKOUTS
LOW VOLTAGE
J-BOX
LINE VOLTAGE
J-BOX
Enable

1.Connect the room thermostat or boiler enable contacts (isolated contact only) to terminals 7 and 8, as shown in FIG. 7-3.

2.If a thermostat is used, install the thermostat on the inside wall away from influences of drafts, hot or cold water pipes, lighting fixtures, television, sunlight, or fireplaces.

3.Thermostat anticipator (if applicable):

a.If connected directly to boiler, set for 0.1 amps.

b.If connected to relays or other devices, set to match total electrical power requirements of connected devices. See device manufacturers’ specifications and thermostat instructions for details.

Outdoor temperature sensor

1.Connect the outdoor temperature sensor (FIG. 7-3) to the Outdoor Sensor terminals on the connection board to enable outdoor reset operation of the Crest.

2.Mount the sensor on an exterior wall, shielded from direct sunlight or flow of heat or cooling from other sources.

3.Route sensor wires through a knockout at the rear of the boiler (see FIG. 7-2).

Variable speed system pump

If a variable speed pump is used in the primary loop, and a 0-10V signal is available from the pump speed control, this signal can be used by the SMART TOUCH control to anticipate changes in the building heat load. By connecting this 0 - 10V signal to the 0 - 10V SYS PUMP IN terminals, the boiler (or cascade) can modulate up and down as the primary flow increases and decreases.

Installation & Operation Manual

ModBus

The RS-485 ModBus cable is connected to the ModBus 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 ModBus interface module.

Hot Water Generator (HWG) thermostat

1.Connect the HWG tank thermostat to the Tank Thermostat terminals on the connection board (FIG. 7-3).

Hot Water Generator (HWG) tank sensor

1.By installing a HWG tank sensor, the SMART TOUCH control can perform the tank thermostat function. The SMART TOUCH control automatically detects the presence of this sensor, and generates a HWG 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 the tank set point.

2.A TST20015 sensor MUST be used with any indirect tank. Failure to use the correct sensor will result in the tank temperature being either above or below the set point. Connect the correct sensor to the Tank Sensor terminals (see FIG. 7-3).

Louver relay

If louvers need to operate before the boiler fires, they can be controlled by this output. Connect these terminals to a 24V relay coil, which is wired to operate the louvers (FIG. 7-3).

Louver proving switch

Louvers are used to provide combustion air for the room air option. A louver proving switch should be connected to the appropriate terminals and are verified prior to operation (see FIG. 7-3).

Boiler pump speed output

This 0 - 10V output is available to control the speed of a variable speed boiler pump. The SMART TOUCH control will vary the speed of this pump in order to maintain a minimum T (set by the installer, see the Crest Service Manual) across the heat exchanger, as well as prevent high limit lockouts when the flow in the primary loop is extremely low. Connect this output to the 0 - 10V input on the boiler pump speed control.

NOTICE	A system supply sensor must be installed
	for this feature to work.

Rate output

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

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