Service Manual
1Service (continued)
Figure 1-2 Ramp Delay Interval
H: Control modes
SH controlling sensor
The SH controlling sensor parameter selects the sensor the control will use to regulate the boiler firing rate. This parameter is adjustable by the installer by accessing parameter H1. The sensor selections are as follows: The outlet sensor regulates the firing rate based on the outlet water temperature of the boiler and the inlet sensor regulates the firing rate based on the inlet water temperature of the boiler. 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 supply sensor temperature. The default sensor is the Outlet Sensor.
SH source
The SH source parameter selects the method used to control the modulation of the boiler. This parameter is adjustable by the installer by accessing parameter H2. The control methods are as follows:
1 - Thermostat. The control modulates the boiler based on the user set point and the temperature of the selected controlling sensor.
2 - BMS (Building Management System). The control modulates the boiler based on the 0 - 10 vdc signal delivered to the appropriate terminals on the connection board. When BMS is selected additional parameters for BMS operation may need to be adjusted. These can only be accessed by the optional PC software. See the Knight Wall Mount Smart System PC Program Instructions Manual for additional BMS parameter information.
3 - Cascade. The boiler is part of a group of boilers sequenced together. The designated Leader boiler determines the total output needed from the group based on the set point and controlling sensor reading. It assigns portions of this output to itself (Leader) and the Member boilers. When Cascade is selected, each boiler in the group requires a unique address (see below). The default control is Thermostat.
Boiler cascade address
The boiler designated as the Leader needs to be programmed with address 0. All the Member boilers require addresses from 1 to 7, and the addresses must be different for each Member. The addresses can be in any order, regardless of the order in which the units are wired together. This parameter is adjustable by the installer by accessing parameter H3. The outdoor air (if used) and system supply sensor must be connected to the Leader boiler. The default address is 1.
Max. cascade set point
This parameter determines the set point used by the individual boilers in a Cascade. When a boiler is commanded to fire by the Leader boiler, it will attempt to achieve this temperature at its outlet. The Leader boiler will limit the modulation of the last boiler to fire in order to hold the temperature at the system supply sensor to the user set point. If any of the boiler outlet temperatures reach the max. cascade set point, the boiler will then modulate down on its own in order to keep its outlet temperature within the max. cascade set point. Therefore, this parameter can be used to limit the outlet temperatures of all the boilers in a Cascade. Note that this parameter does not apply when the boiler is heating an indirect DHW tank. This parameter is adjustable by the installer by accessing parameter H4. The default max. cascade set point is 185°F.
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