Honeywell DHC, Service Manual, Page: 236 / 262

Hydraulic Components SDC / DHC
236 EN2H-0221GE51 R0812
7.3.12.3 Mode of operation of cascade control
7.3.12.3.1 Switch-on characteristics
The switch-on characteristics of the boiler stages are determined
by the set switching differential and the dynamic switch-on delay.
The stage number is incremented only when the following criteria
are fulfilled:
BT
ACTUAL
< BT
SETPOINT
– SD/2
t >= t
Switch-on delay
* (100 – (dVT * 100 / VLSetpoint) ) / 100
Stages
Number
= Stages
Selection
The boiler temperature of the leading boiler or the total flow
sensor must have exceeded the specified boiler setpoint minus
half of the switching differential (switch-on delay time) for at least
the calculated switch-on delay. Additionally, the requested stage
number must have been sent to central device 10 as the active
status response.
The additional boiler stages can be switched on by using a fixed
time delay (Switch-off of the dynamically determined switch-on
delay).
This can be used for the fixed control of the switch-on delay of an
additional heat generator, e.g. of a heat pump. Therefore, in the
Heat Generator menu, the parameter 39 must be adjusted to a
value of 1..300 min.
7.3.12.3.2 Switch-off characteristics
The stage number is decreased again as soon as the temperature
of the leading boiler or of the total flow sensor exceeds the
present setpoint boiler temperature plus half of the switching
differential for at least the calculated switch-off delay time.
BT
ACTUAL
> BT
SETPOINT
– SD/2 or BT
ACTUAL
>= BT
MAX
t >= t
Switch-on delay
* (100 – (dVT * 100 / VLSetpoint) ) / 100
Stages
Number
= Stages
Selection