SPC DERV Installation, Operating And Maintenance Instructions page 11

The larger three phase units (375, 500) require cables for each of the phases and a neutral. Both
indoor and outdoor units must be earthed and a phase and neutral cable must be taken from the
3 phase terminal block in the outdoor unit to the indoor unit.
Two control wires must be run between the terminals on the controller of the indoor unit and the
relay terminals on the outdoor unit. It is recommended that these wires be a minimum of 1mm2.
The DERVDX units incorporate a built-in controller allowing the speed to be changed (Low, Med
& High) along with an on/off switch, see figure below. Provision has also been made for remote
control of the DERV units via two volt free contacts. These contacts can be used to switch the
units on and off remotely via switches or relays attached to BEMS, occupancy sensors etc. The
two remote contacts are wired into terminals R1/R2 and R3/R4 respectively. Again wire should be
a minimum of 1mm2 and remote contacts should be rated at a minimum of 2A (5A, 500 unit). If
one or both of the remote contacts are not used then links must be fitted between R1/R2 and
R3/R4.
The controller is connected to a thermistor sensor located between the heat recovery heat pipe
and the dehumidifier heat pipe inside the indoor unit and senses the temperature at this point.
The three temperature settings available equate to 22, 24 and 26° C respectively, when the
sensed temperature falls below the set temperature then the outdoor unit will switch off. It is
recommended that the lowest temperature setting is used to provide continuous operation of the
outdoor unit.
The controller incorporates a built in time delay on the compressor to prevent hunting and has a
non-volatile memory allowing the settings to be saved.
Figure 4. Controller display
When the compressor delay timer is operating the set temperature LED will blink on and off for
half a second each. The on delay timer is set at 180 seconds.
When the compressor is not running according to the temperature setting the LED blinks on for
0.1 seconds and off for 0.9 seconds.
The compressor is set to run if the sensed temperature >= to the set temperature+1 and set to off
if the sensed temperature < set temperature.
QA/IOM/63 ISSUE 2 - DERV Page 11 of 19