Marstair 526 HL Series, Technical Manual, Page: 14 / 31

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ELECTRICAL CONNECTIONS
Supply, control and connecting cables are fitted by the installer.
Installer wiring should be carried out in accordance with local and national codes.
Cables must be size compatible with the recommended fuse for a given system. (see page 7 for fuse ratings).
A double pole isolator switch should be positioned adjacent to the indoor unit.
The equipment must be earthed.
Systems should have the supply taken to the outdoor unit; a single phase supply (L1), is run back to the indoor unit.
Power should be connected to the outdoor unit for 4 hours to allow the lubricating oil to be heated prior to compressor
start up.
INDOOR UNIT WIRING
The connections for internal wiring for indoor units are made at the right hand side of the unit. Mains supply should be
routed to the terminal blocks in the unit through the slots behind the fan motor if brought from below.
Cable grips are provided above the terminal block to give a secure installation.
Note that the electrics assembly can be quickly removed if required by removing 2 screws from the evaporator flange and
springing the electrics mounting plate free of locating slots in the rear panel. These screws and washers form the earth
connection to the air handler and must be securely re-fitted.
Make sure all connections are secure and all wires are clear of rotating parts. Interconnect as shown on pages 21 to 23.
CONVERSION OF HLR INDOOR UNIT FOR AIR CONDITIONER USE
The HLR indoor unit is supplied wired for use as a heat pump .
For air conditioner mode, remove the pink link between relay 1 terminal 14 and relay 2 terminal 22.
OUTDOOR UNIT WIRING
Cable entry for the outdoor unit electrics is through the cabinet to a terminal block.
MCU+, MHPUE and DCUE units are supplied wired via a head pressure controller to give maximum control. Ensure
that all connections are secure and that both units are earthed.
MCU unit fan motors have a high speed (black) wire and a low speed (red) wire; the speed not being used is wired into
a dummy terminal. They are supplied wired for low fan speed, which is suitable for temperate climates. If continuous
running is expected at ambient temperatures of 35°C or higher, change to high speed by interchanging the black and red
wires, i.e. black to fused terminal, red to terminal 4 (single fan units) or terminals 4 and 8 (double fan units).
SCROLL COMPRESSOR ROTATION
On 3 Phase units it is possible for the scroll compressor to run backwards. This becomes obvious on start up; the
compressor will not develop a normal running pressure differential and the top will not become warm. It may be
excessively noisy. If this happens, switch off the mains power and exchange any two of the phases supplying the unit.
This will correct the rotation of the compressor.
DATA PLATES
Because of the ability to match indoor and outdoor units, the data plates only give information on either an indoor or
outdoor unit. To obtain the system details, input power and currents from indoor and outdoor units should be added.
FIRE LINK
In order to automatically switch off the fan in the event of a fire, it is necessary to fit an external switch (240V, 3A, closed
to run, volt free contact) to:-
HLR units: in the installer wire between terminal block terminal 2 and the Marstair remote control thermostat terminal
2(96000320) or L (97200211)
HL units: in the internal (black) wire between the fuse and rotary switch terminal 'd'. This external switch should be
operated by the building's fire alarm or BMS system.