Electrical Connections - SPC DERV Installation, Operating And Maintenance Instructions

4.4 Electrical connections

4.4.1 DERV units
DERV units are designed to allow simple operation with the minimum of electrical power and
control wiring required on site. A wiring diagram for the unit is attached to the unit next to the
terminal block. A copy of the wiring diagram is shown below.
Figure 2. Wiring details DERV units
For the size 500 unit the fuse rating is 5A not 2A as shown above.
Power supply to the units is single phase 230V/50Hz. A three wire supply is required (PH/N/E)
and this should be taken from a suitably isolated power supply. Maximum running current and
power drawn are given in the technical data table but minimum wire size for the power supply
should be 1mm2.
The terminal block is accessible on the side of the indoor unit. The 3-core power cable should be
connected to this terminal block as shown on the wiring diagram attached to the unit.
The DERV units incorporate a built-in controller allowing the speed to be changed (speed 1,2 & 3)
along with an on/off switch. 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.
QA/IOM/63 ISSUE 2 - DERV Page 9 of 19