Lochinvar 80 - 285 User Manual download pdf (Page 48)

Installation & Operation Manual

8 Field wiring

System supply sensor

1. By installing the system supply sensor into the supply of

the primary loop, the temperature of the primary supply

can be controlled. The SMART SYSTEM control

automatically detects the presence of this sensor, and

controls the boiler firing rate to maintain the system

supply temperature to the set point (if the outlet sensor

control is currently selected). If it is desired to control the

system return temperature, then program the SMART

SYSTEM control to use the inlet sensor as the controlling

sensor. See the Knight Boiler Service Manual for

instructions on how to use the inlet sensor as the

controlling sensor. When the inlet sensor is programmed

as the controlling sensor, it is vital that the SYSTEM

SUPPLY sensor be installed. DO NOT INSTALL THE

SYSTEM SUPPLY SENSOR INTO THE SYSTEM

RETURN.

2. Connect these terminals to the system supply sensor

(FIG. 8-3).

Boiler management system

1. An external control may be connected to control either

the firing rate or the set point of the boiler. Connect the

Room Thermostat / Zone Control terminals to the enable

output of the external control and connect the 0 - 10 vdc

terminals to the 0 - 10 vdc output of the external control.

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.

Runtime contacts

The SMART SYSTEM control closes a set of dry contacts

whenever the burner is running. This is typically used by

Building Management Systems to verify that the boiler is

responding to a call for heat.

Alarm contacts

The SMART SYSTEM control closes another set of contacts

whenever the boiler is locked out or the power is turned off.

This can be used to turn on an alarm, or signal a Building

Management System that the boiler is down. Note that these

contacts will close momentarily at the end of each call for

heat.

Wiring of the cascade

When wiring the boilers for Cascade operation, select one

boiler as the Leader boiler. The remaining boilers will be

designated as Members. See page 56 “Configuration of the

Cascade” for a detailed explanation of this procedure.

Connect the system supply sensor and outdoor air sensor (if

used) to the Leader boiler. For the Cascade system to work

properly the system supply sensor must be installed. The

location of the system supply sensor should be downstream of

the boiler connections in the main system loop (FIG.’s 6-4,

6-6, and 6-8). The system supply sensor should be wired to the

Low Voltage Connection Board at the terminals marked for

the system supply sensor (see FIG. 8-3). The Leader control

will use the water temperature at the system supply sensor to

control the operation of the Cascade.

If outdoor air reset is desired, the outdoor air sensor should be

wired to the Low Voltage Connection Board at the terminals

marked for the outdoor air sensor (FIG. 8-3). If the outdoor

air sensor is connected, the Leader control will calculate the

water temperature set point based on the programmed reset

curve parameters. If the outdoor air sensor is not connected,

the Leader control will maintain the fixed water temperature

set point that is programmed into the control.

If a Thermostat, Zone Control enable output, or Building

Management System enable output are available, it should be

wired to the Low Voltage Connection Board on the Leader

boiler at the terminals marked for the Room

Thermostat/Zone Control (FIG. 8-3). If the boilers are to run

continuously, connect a jumper wire between the R and W

terminals for the Thermostat/Zone Control input. This will

initiate a call for heat on the Cascade.

Communication between the Leader boiler and the Member

boilers is accomplished by using shielded, 2-wire twisted pair

communication cable. Connect one of the twisted pair wires

to terminal A on each of the Low Voltage Connection boards,

and the other wire of the twisted pair to terminal B on each of

the Low Voltage Connection Boards. Connect the shield wires

to one of the shield ground terminals on the Low Voltage

Connection Boards (FIG. 8-3). If more than two boilers are on

the Cascade, daisy chain the wiring from the Sequencing

terminals on the second boiler to the Sequencing terminals on

the third boiler, then from the third to the forth, and so on.

The connections between boilers can be made in any order,

regardless of the addresses of the boilers. Try to keep each

cable as short as possible.

Low gas pressure switch

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 is used, connect

their respective contacts in series, and connect them to

the terminals on the connection board (FIG. 8-3).

Flow switch

1. A flow switch is used to guarantee flow through the boiler

before allowing it to fire. The flow switch must be

installed in line with the boiler.

2. Connect these terminals to the normally open contacts on

the flow switch (FIG. 8-3).

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Lochinvar 80 - 285 User Manual Page 48

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