Powtier Controls Limited
505MST Thermostat
Instruction Manual
Introduction
The 505MST/M is an electronic five-stage thermostat which caters for the heating and cooling
requirements on the MK3 HST trailers, replacing a electromechanical device.
The 505MST/M is an intelligent thermostat unit. Its design is based on the latest micro-
controller chip technology.
Special features of the 505MST/M include: the 'Winter/Summer' temperature compensation,
prevention of temperature overshoot and undershoot, selectable setpoint temperature
switchings and time-delay.
System control
The 505MST/M Electronic Thermostat consists of two sensor inputs; one sensor monitors the
saloon temperature and the second sensor monitors the ambient (outside air) temperature.
The Thermostat has five relay outputs. These are primarily used for the switching of:
1.
Heater 1
2.
Heater 2
3.
Heater 3
4.
Low level damper solenoid
5.
Cooling
The relay outputs are designed to drive externally connected contactors.
Temperature setpoints
Table A, B and C give four possible manually selectable saloon temperature setpoints for the
winter period.
Note 1:
Under Table A, the winter and summer periods use the same temperature
switching points.
Note 2:
Under Table B and C, the settings are for the winter periods.
Note 3:
During the summer period, the 505MST/M automatically use Table A settings.
However, during the winter period, there are three possible temperature settings,
depending on the setpoint switch (see Table S2).
505MSTIM
Page 2
29 June 1998
Issue 1.0