Heating Pre-Control in a 2-Pipe System

For a 2-pipe system, a common pipe system is used for heating and cooling pre-control circuits.

These systems cannot provide heating and cooling energy at the same time. When the “HVAC_Mode” input takes the value “auto”, both, heating and cooling pre-control circuits will be switched off.

We need both pre-control macros, this macro and the cooling pre-control macro “PRCC_PreCtrlClg“.

For a correct 2-pipe system operation:

With these settings the heating pre-control will operate as shown in the next table:

Table 2.   Pre-control heating operation

HVAC_Mode

SYS-01

Pre-control Heating

0,1

0

off

2

0

heat

3

0

off

4

0

off