Specifications

9
9 - Regulator
9.1 - Low temperature kit
Installation of the low temperature kit should be envisaged
whenever a unit must operate in cooling mode (in heating mode
the kit is bypassed), at temperatures below the standard operating
limits. If the kit is not installed and the unit is operated under
such conditions, condensing pressure will be so low that the indoor
unit coil will become frosted.
The function of the pressostatic low temperature kit is to maintain
condensing pressure at a constant value, when the outdoor
temperature drops, by reducing the speed of the fan on the outdoor
unit.
Condensing temperature can be measured by a direct pressure
reading using the Schrader valve. Factory setting is 16 bars, i.e.
45°C. Condensing pressure to be maintained is adjustable if
necessary (ref a) with a screwdriver.
The condenser fan is controlled proportionnaly by a triac.
Minimum voltage supplied by the controller is 45% of input
voltage. This is a fixed value.
If for climatic reasons, condenser fan speed has to be reduced,
complete stoppage of the fan can be obtained below the minimum
voltage attained. Set the selector (ref b) on the "Cut Of” position to
obtain fan stoppage. The initial position is “Min. Speed”.
9.2 - High pressure switch (inter-season starting kit) for MOH
This high pressure switch is only active in the heating mode and
controls a hot gas bypass valve.This control device opens the hot
gas bypass valve at 25bars and cuts out at 17 bars.
It is usually activated during the following phases :
- Start-up when the conditioned space is cold and the coil on the
air handling unit is at a temperature lower than 35°C (indoor
fan does not operate at coil temperatures lower than 35°C in
the heating mode).
- Final phase of defrost cycle.
- Start-up in heating mode during the inter-season.