Slant/Fin CHS-399 - Manual (Page 19)

CHS Series Controller and Display
│
Slant Fin Corp.
17
Table 2-10 Lead Lag Master Configuration Parameters
Parameter Description Factory Settings
Master
enable
*
Enable or Disable Lead Lag Master. One (and only one) unit must be set to
“Enable” for Lead Lag operation to function.
Disable
Setpoint
source *
Select the Lead Lag setpoint source:

Local (control references “Setpoint” setting)

4-20mA (control references 4-20mA signal from an external control). “Outdoor
reset enable” must be set to “Disable” when using a 4-20mA signal; see Section
2.4.3.3 Lead Lag Outdoor Reset. Local
Setpoint Setpoint value for Lead Lag modulation. Range 60°F to 190°F. 150°F
Off
Hysteresis *
Value added to the “Setpoint” to determine water temperature at which the burner
will shut off. Example: If “Setpoint” is 150°F, and “Off hysteresis” is 15°F, the
burner will be shut off at 165°F. Range 5 °F to 70°F.
15°F
On
Hysteresis *
Value subtracted from “Setpoint” to determine water temperature at which the
burner will fire. Example: If “Setpoint” is 150°F, and “On hysteresis” is 10°F,
burner ignition occurs at 140°F. Range 2°F to 40°F.
10°F
P Gain *
Gain applied to the proportional term of the LL PID control algorithm. Range 5 to
50 (no units). Decrease to slow rate of control response.
30
I Gain *
Gain applied to the integral term of the LL PID control algorithm. Range 5 to 50 (no
units). Decrease to slow rate of control response.
15
Base load
common * Maximum modulation rate of all firing units when other units are still available and
idle. Range 25 - 100%.
70%
* Password protected
Use of 4-20mA Input
Setpoint source – If “Local” is selected as the “Setpoint source”, the “Setpoint” value entered on the screen,
depicted in Figure 2-16, is used for control. If 4-20mA is selected as the “Setpoint source”, the boiler
determines its setpoint from the 4-20mA signal. The setpoint is calculated from a factory-set scale between 60°F
corresponding to 4mA, and 190°F corresponding to 20mA. If the 4-20mA input signal is invalid, out of range, or
absent, the “Setpoint” is used until the signal is valid again. Regardless of the “Setpoint source”, “Local” or “4-
20mA”, the controller’s internal PID algorithm modulates the burner. The 4-20mA signal does not create
burner demand; a call for heat must be present at the CH2 (LL) input.