Lochinvar 402 - 2072 Service, Control modes, SH controlling sensor boiler only, ModBus timeout

Copper-fin II/IIE Boiler and Water Heater Service Manual

1 Service

Control modes

SH controlling sensor (boiler only)

The SH controlling sensor parameter selects the sensor the control will use to regulate the boiler firing rate. The sensor selections are as follows: The outlet sensor regulates the firing rate based on the outlet water temperature of the unit and the inlet sensor regulates the firing rate based on the inlet water temperature of the unit. If the outlet sensor is selected, and the optional system supply sensor is connected, the control will regulate the firing rate based on the system sensor temperature. If the inlet sensor is selected, and the optional system return sensor is connected, the control will regulate the firing rate based on the system return sensor. When programmed to use the inlet sensor, a system supply sensor must be installed for proper operation. If a 3-way valve is installed for low temperature protection, a system return sensor must be installed as well. The default sensor is the Outlet Sensor.

Enable input (active / inactive)

The boiler or water heater can receive a call for heat in two different ways. First, an external contact (like a tank thermostat) or sensor (like a tank sensor) can generate a call for heat. Second, the 0-10Vdc voltage from a BMS can be used to generate the call for heat, as well as provide the setpoint or modulation level. On boilers, the external contact is connected to the Stage 1 input on the low voltage connection board. On water heaters, the external contact is connected to the Tank Thermostat input on the low voltage connection board. When a tank sensor is connected, the Tank Thermostat input is not used. When the call for heat comes from an external contact or tank sensor, the enable input must be set to active. When the call for heat comes from the 0-10Vdc input, the enable input must be set to inactive. The default setting is Active. Can only be set to inactive when BMS input is set to active.

BMS input (active / inactive)

When the building management input is enabled, the control modulates the unit or the cascade based on the voltage on the 0-10V input on the connection board. The 0-10V input may control either the modulation of the unit(s), or the setpoint. The default value is Inactive. See menu Section J to adjust the parameters that control the BMS operation.

Cascade (active / inactive)

Boilers or water heaters may be part of a group of units sequenced together. When so connected, each heater must be programmed to operate as part of the Cascade. This is done by setting the Cascade to Active. The default value is Inactive.

Sequencer (active / inactive) (boiler only)

The individual stages in the heater can be controlled separately with an external sequencer.

ModBus (active / inactive)

When the optional ModBus board is installed, the heater can be monitored and controlled by a Building Control System (BCS). If the heater is to be controlled through ModBus this parameter must be set to ACTIVE. The default value is Inactive.

ModBus timeout

When the heater is being controlled or is receiving temperature readings through ModBus, the information sent to the heater must be refreshed periodically. If the heater does not receive new information after a timeout, it will revert to local temperature readings and control. This prevents the heater from running for too long should the ModBus connection be lost. The range of this parameter is 0 to 120 seconds. The default value is 10 seconds.

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