FOR HVAC INSTALLER ONLY
If the timer fails to operate or operates erratically, check that the control panel receives 24Vac from the UA-150H. If 24Vac is present at the control panel, reset the timer by pressing the reset button at the bottom center of the timer face. The reset button is the small recessed button with an R beneath it located below the 1…7 and h buttons. Press the reset button in until the display clears. Release the reset button. The display will reappear as 00:00. Resetting the timer will clear the time and all program settings. After resetting the timer follow the instructions below to set the correct time and ventilation programs.
Setting The Time: The following instructions explain how to set the ventilation timer. First, set the correct time on the timer by sliding the switch in the upper right hand corner of the timer to the clock symbol
•and pressing the 1…7 (DAY), h (HOUR), and m (MINUTE) buttons. Remember that this timer operates on a 24-hour (military time) clock.
Ventilation Schedule: Slide the switch in the upper right hand corner to the program symbol P. “ON” will appear to the right of the time and the number “1” will appear in the lower right hand corner of the display. The “1” and “ON” signify the turn on time for the first program. Press the 1…7 button to choose the days of the week for this program. You can choose Mon.-Sun, Mon.-Fri., Sat-Sun, or any single day of the week. The days chosen are shown along the top of the display on the ventilation timer. Next press the h button to set the hour for the start of the ventilation period. Remember that this timer operates on a 24-hour clock. Then press the m button to set the minutes past the hour to start the ventilation. Now, with the ventilation start time set; press the I/O button. The word “OFF” should appear to the right of the time and the number “1” should remain in the lower right hand corner of the display. The “1” and “OFF” signify the turn off time for the first program. Set the turn off time using the 1…7, h, and m buttons in the same way as described above and continue on to the second through sixth programs. When setting the ventilation programs, you can return to the current time display by sliding the switch in the upper right corner of the timer to RUN. The slide switch in the upper right must be set to RUN for the timer to operate with the scheduled programs.
Automatic or Manual Mode: The slide switch in the upper left of the timer is used to choose between automatic and manual operation of the timer relay. When the slide switch in the upper left of the timer is set to AUTO mode, the UA-150H will ventilate when the scheduled programs call for ventilation. When the slide switch in the upper left of the timer is set to manual (set to hand symbol on the right), the operation of the timer is controlled by the I/O button only. Pressing the I/O button will switch the ventilation timer between ON (detent) and OFF (detent). As you press the I/O button, “ON” or “OFF” will
be displayed to the right of the time. The “ON” or “OFF” to the right of the time will indicate if the ventilation timer is on or off. The I/O button will manually override scheduled programs if the timer is in AUTO mode.
4.6 Low Pressure Control
If the low side refrigerant pressure drops to 15 PSIG, the low- pressure control opens and shuts off the compressor and impeller fan. It is an automatically reset control that will close when the pressure rises to 35 PSIG. Its primary function is to prevent damage to the compressor if a leak develops in the refrigeration system. It may also open if the unit is A) installed in a cool area (below 50 F) or B) installed where it is below 40 F and then started. Under these conditions, the unit will restart within several minutes. Until the unit warms up, it may repeat the cycle several times.
