Honeywell SDC Service Manual page 132

Hydraulic Components
Switching differential I
Switching differential II
NOTE
132
Switching differential I controls the heat generator capacity
required according to load and demand by switching on and off
the stage required for the actual heat demand within the set
range. Switching on and off is initiated symmetrically to the
setpoint within half of the absolute value of the switching
differential.
Switching differential II (only two-stage heat generator and heat
generator 2 x single stage) determines how many stages are
required to meet the actual heat demand (partial load - stage I, full
load - stage II). This switching differential is overlaid symmetrically
on switching differential I and must always be set to higher
values.
In cascade mode, this setting would be superseded by the
cascade setting and is therefore not available.
Mode of operation with switching differential II
• When the heat generator temperature is below switching
differential II, stage I is switched on without delay. Stage II is
enabled after stage II delay has passed (see "Heat Generator"
menu).
• Stage II is switched off as soon as the heat generator reaches
the setpoint temperature plus half of switching differential I.
• Stage II is switched on again as soon as the heat generator
undershoots the setpoint temperature minus half of switching
differential I.
• Stage I is switched off when the heat generator temperature
exceeds the set nominal value plus half of switching
differential II.
In some cases it can be expedient to apply a fixed delay for
further heat generators, e.g. if the heat generators use different
energy sources. This fixed time delay can be set with parameter
39 in the Heat Generator menu. In this case, the settings of
parameter 10 in theHeat Generator menu or the parameter 02 in
the Cascading menu are no longer accessible or will be
overwritten.
SDC / DHC
EN2H-0221GE51 R0812