Skip to content
☰ Havaxer
§
memory01
Examples

Theoretical

This is the installation the 01 was designed for: a complete HVAC controller for one circuit that can heat or cool, with domestic hot water. It uses most of the board and leaves a little spare.

Nothing here is firmware you can download. It is the shape of a working system - what goes where, and what the logic between them has to do.

Wiring

Terminal What to connect
TEMP1 outside temperature sensor
TEMP2 domestic hot water (DHW) temperature sensor
TEMP3 system supply, or buffer top, temperature sensor
TEMP4 circuit supply temperature sensor
TEMP5 spare - a room temperature sensor, for example
TRIAC1, TRIAC2 circuit mixer, open and close
RELAY1 circuit pump
RELAY2 heat source controller - on means "start heating the supply water"
RELAY3 DHW changeover valve, and the DHW charge pump if the heat source does not provide it
SIG1 spare 5 V output - an off-board relay for a DHW circulation pump, for example
OC1 spare mains input - an ordinary light switch reading a request for extra hot water, for example

What the logic does

With those connections in place, an application might work like this:

  1. Watch TEMP2. Below 42 °C, turn RELAY2 and RELAY3 on. Above 48 °C, turn them off.
  2. If the circuit is enabled, turn RELAY1 on. If not, turn RELAY1 off, TRIAC1 off and TRIAC2 on - closing the mixer.
  3. If the circuit is enabled, watch TEMP4. Below 26 °C, pulse TRIAC1 on for 3 seconds. Above 28 °C, pulse TRIAC2 on for 3 seconds. Wait 15 seconds before acting again.
  4. Watch TEMP3. If it falls below the minimum supply temperature the circuit needs, turn RELAY2 on. Turn it off once TEMP3 reaches that temperature plus 7 K, or after 60 minutes.
  5. Watch TEMP1 and adjust the circuit's required supply temperature against it.

The 15-second wait between mixer pulses is what stops the loop chasing itself: a mixer valve takes time to move, and the water takes longer still to reach the sensor.

Every temperature and time above is an example. Real values depend on the plant, the emitters and the building - and getting them right is most of the work in an HVAC controller.

The 02 does the same thing for two circuits - see its example.