Lochinvar 497 - 2067 Glossary, Power Supply AC120VAC/60Hz, ON/OFF Rocker Switch, Ignition Module

Installation & Service Manual

9 Glossary

Power Supply (AC120VAC/60Hz)

120VAC/60Hz/1PH power connects to black (line) and white (neutral) wires located within an electrical wiring box located on the left side of the unit. A green chassis grounding wire is also provided for connection to earth ground.

ON/OFF Rocker Switch

The black line voltage wire runs directly to a single pole, single throw On/Off rocker switch located behind the front cover accessible by a thumb screw. Turning ON the rocker switch delivers line voltage to the low voltage transformer and ignition module.

Note: The On/Off switch does not provide for disconnection of power being supplied to any remotely connected devices that may be connected to the unit (i.e. pumps, louvers, power venters, etc.,). As such, it may be necessary to locate and turn off power to these items before attempting to service the unit.

Low Voltage Supply Transformer

A 120VAC to 24VAC transformer located within the control panel provides 24VAC/60Hz to many of the components located on the unit. One of its 24VAC outputs (blue) is connected to a circuit breaker and the other (yellow) is connected to chassis ground.

24VAC Circuit Breaker

A circuit breaker is provided on Models 987 - 2067 for protection of the low voltage supply transformer from overloads and short circuits. The breaker is located inside the unit on the lower right corner of the control panel. Power from this breaker goes to the electronic temperature controller, ignition module and various other components and/or options on the unit. When tripped, all factory-installed 24VAC components will lose their 24VAC power.

Manual Reset High-Limit Thermostat

A manual reset high limit thermostat is provided as backup for the temperature controller. This will be an adjustable dial bulb- capillary style thermostat that will trip and require resetting should water temperature exceed its settings. When tripped, all controls remain powered, but 24VAC is prevented from being delivered to the ignition module’s thermostat input.

EMS/Sequencer/Remote Aquastat Terminals

The EMS/sequencer/remote aquastat terminals are provided for connection of the unit to an external energy management system or sequencer and are located along the top edge of the terminal strip located within the electrical wiring box. In addition to providing a means to externally stage fire the unit, these terminals also provide for remote shutdown and override by routing through dry contacts from external devices. Connection of the external dry contacts to these terminals requires the removal of one or more factory installed jumpers located on the terminal strip.

Safety Device Terminals

The safety device terminals ensure that no power can be delivered to the ignition module unless factory/field-installed safety devices such as flow switches and gas pressure switches are closed. These safety device terminals are located below the EMS/Sequencer/Remote Aquastat terminals located within the electrical wiring box. Two types of connections are offered: Continuous terminals provide for connection of safety devices that are desired to be constantly monitored. Intermittent terminals are provided for devices that are only monitored during a “call for heat” cycle. Connection to either of these terminals requires the removal of a factory-installed jumper located on the terminal strip.

Electronic Temperature Controller (Operator)

A 2-stage electronic temperature controller is provided on the unit and it serves to maintain a user selectable temperature set point. Ultimately, the temperature controller delivers 24VAC to the ignition module and pressure switch when it senses heat mode is desired. It also activates the pump relay. If more heat is needed, it activates the high fire stage.

Ignition Module

(Controlled by Electronic Temperature Controller)

One ignition module is provided on the unit. Upon sensing the 24VAC delivered to it by the electronic temperature controller, the ignition module checks for a shorted pressure switch and then, provided the air switch isn’t shorted, supplies 120VAC to its blower output relay and waits for a pressure switch signal.

Two Speed Blower

(Controlled by Ignition Module and Relay Board)

A single 2-speed blower on Models 987 - 2067 (single 1-speed blower on Models 497 - 747) provide combustion air to the unit. The blower is provided with a high and low speed tap. The blower operates in tandem with the ignition module when a call for heat signal is received. Depending upon the number of stages in operation, the blower’s speed may increase or decrease accordingly.

Pressure Switch

(Activated by Blower Turning On)

One pressure switch is provided to monitor the blower On/ Off operation. Upon a call for heat, 24VAC is delivered to the pressure switch. If the blower generates adequate air pressure, the pressure switch closes to deliver 24VAC to the ignition module pressure switch monitoring input terminal.

Prepurge

(Ignition Module Function)

62