Indirect Return Increase - Honeywell SDC Service Manual

Hydraulic Components
7.2.17.3
Function
NOTE
7.3.1
7.3.1.1
162

Indirect return increase

Indirect return increase is realised by means of the mixed heating
circuit valves in the heating circuits. It only works for systems
without a bypass pump and without controlled flow mixing.
When this function is active, two values are calculated
independently for regulating each mixed heating circuit. The first
value is the control variable for the flow setpoint of the heating
circuit; the second is the control variable for the return setpoint.
The control variable used for mixed heating circuit control (mixed
heating circuit control variable) results from the superimposition of
both values. In this the adjustment of the return temperature is
treated with priority.
Indirect return control is only active with mixed heating circuits
that are in heating operation as well. It does not affect a heating
circuit in reduced operation.
To avoid excessive pulsing, we recommend enabling the
connected consumers (heating and hot-water circuits) with
staggered switch-on times.
This function does not affect direct heating circuits.
Indirect return control is only feasible for systems without bypass
pumps and without controlled flow mixing.
7.3 Heating circuit
General heating circuit functions
Heating curve
The prerequisite for a constant room temperature is the exact
setting of the heating curve of the relevant heating circuit as well
as a correct design of the heating system on the part of the
heating technician according to the heat demand calculation.
If adjustments are necessary, they should be made in small steps
at a distance of a few hours to assure that a steady condition is
obtained.
SDC / DHC
EN2H-0221GE51 R0812