Airxcel Marvair LL357D4, Manual, Page: 7 / 12

7 LL357D4 PDS, 4.2011
Testing the Thermostat
Note: The LL357D4 does not require the units to be in phase.
Procedure: (A/C Testing with LL357D4 Lead/Lag Control for Two Units)
UP - Used to increase the time, set temperatures and to adjust
configuration settings.
DOWN - Used to decrease the time, set temperatures and to
adjust configuration settings.
SYS (left) - Used to change from OFF, HEAT, COOL and AUTO changeover modes.
RIGHT - Used to turn on and off the indoor fan.
UP, SYS and RIGHT - Held in simultaneously for 10 seconds to lock and unlock the thermostat.
DOWN and SYS - Pressed simultaneously to display outdoor temperature if outdoor remote sensor is
connected.
1. Set the cooling temperature on the wall thermostat to a point higher than the ambient temperature.
Set the heating temperature to a temperature that is lower than the ambient temperature. Turn the
selector switch to the “off” position.
2. Set the time delay on unit No. 1 to “3” minutes, and No. 2 to “5” minutes.
3. Set the change over setting of the enthalpy control to the “d” setting (ComPac® II A/C only).
4. Provide power to A/C units and turn disconnects on.
5. Check incoming power to each unit. For units designed for operation on 208/230v, 60hz power
supply, the transformer is factory wired for a 230 power supply. For a 208 power supply remove the
orange lead from the transformer and connect the red lead. Insulate the orange lead.
6. Cooling. Use the SYS switch to set the thermostat to “AUTO”. Slowly lower the cooling temperature
until the switch closes. The indoor fan should operate on the lead unit. Once the indoor fan turns
on, allow approximately 3 to 5 minutes for the compressor to start. Note that the outdoor fan may
not come on immediately because it is cycled by refrigerant pressures. Next, lower the temperature
until the switch closes. Follow the above procedures for the lag unit.
The green light on the lead lag control should be on. One amber light will be on to identify the lead
unit. The other light should be off. If the lag unit comes on with the lead unit the light for the lag
unit will not come on. You should never have all 3 lights on at one time.
Allow the units to run for 2 to 3 minutes then check the temperature differential between the return
air and the supply air with digital thermometer. The temperature differential should be between 12
and 20 degrees depending on ambient temperature.
Next, slowly raise the cooling temperature until the switch opens. The compressor and outdoor fan
should turn off. The indoor fan will continue to run for “90” seconds until the fan purge times out.
Raise the temperature until the switch opens. The lead unit will shut down accordingly to the same
procedures as outlines above.
Note: (ComPac® II A/C only) To check the system operation under different ambient conditions,
the air temperature and enthalpy sensors must be “tricked”. When outdoor ambient conditions
are higher than the control setting, a component cooler aerosol may be sprayed directly into the
enthalpy sensor to stimulate low enthalpy conditions, causing the economizer damper to open.
Alternately, when outdoor conditions are lower than the set point, a source of heat such as a hair
dryer can be directed on the enthalpy sensor to simulate warm conditions, which will bring on
mechanical cooling and start the compressor.
7. Heating. Slowly raise the heating temperature until the switch closes. The fan and electrical heat
should immediately cycle on. The unit should start blowing warm air in 2 to 3 minutes. Next, raise
the temperature until the switch closes. Follow the above procedures for lag unit.
Hold the manual advance button in for nine seconds the lead lag lights should switch. Next, slowly
lower the temperature until the switches open. The lag unit should shut down immediately. Next,
slowly lower the temperature until the switch opens, the lead unit should shut down immediately.
8. Replace thermostat cover and panels on the unit.