ENVI
®
Control
14
1.6.2
CH Modes
There are nine CH Modes (0-8). A more detailed description of each mode is included below.
1.6.2.1 CH Mode = 0 (Setpoint & Stat)
Description
Setpoint is the desired outlet water supply temperature. Upon heat demand (or enable/disable), the ENVI
®
control
fires and modulates the boiler to maintain supply water temperature at the desired CH setpoint. The upper
(HYSTERESIS OFF) and lower (HYSTERESIS ON) temperature differentials within CH settings control the
temperature at which the burner turns on or off.
Example
: A boiler with the following parameters (SETPOINT = 160 °F, HYSTERESIS OFF = 9 °F, HYSTERESIS ON
= 10 °F) modulates to try to maintain 160° F. If the temperature increases above 169° F (160 °F SE 9°F
HYSTERESIS OFF), the boiler will shut off. Once it shuts off, it will not restart until the temperature drops below 150°
F (160 °F SETPOINT
– 10°F HYSTERESIS ON). This is illustrated graphically below.
The MIN SETPOINT and MAX SETPOINT parameters
within the boiler settings menu limit the setpoint range. See
Appendix 3.1 and 3.2 for the default values.
CH Mode 0 is recommended for all member boilers in a cascade system with the factory installed enable jumper left in
place across LVTB -1 terminals 1 & 2.
In the event of failure of the master boiler the members will operate as standalone and control to their CH set points.
NOTE:
The boiler is enabled by the TB1/LV terminals 1 and 2 (enable/disable) becoming closed
or shorted. This circuit is energized internally.
DO NOT APPLY EXTERNAL POWER TO
THESE TERMINALS.
Internal Setpoint
145
150
155
160
165
170
175
0
10
20
30
40
Time
Boiler Temperature
Boiler Set Point
Boiler Turns On
Boiler Turns Off
