Modes Of Operation; Cool Mode; Cold Start; Sleep Function - McQuay OM 813 Operation & Maintenance Data

Modes of Operation

Cool Mode

In Cool Mode, the compressor will start if the temperature at
the space temperature sensor is 1°F or higher than the set
point. It will stop if the space temperature sensor is 2°F or
lower than the set point, subject to timing requirements.
In the Cool Mode, the indoor fan will operate according to the
user settings for Fan Mode – Continuous or Cycle and Speed.

Cold Start

Cold start is initiated when the control hasn't called for cooling
for more than two (2) hours, or during a power-on-reset.
During cold start, the set point is lowered by 4°F (Tset-4°F) if
the differential calls for cooling. The unit will operate in cold
start until the new set point is satisfied (+ or – 1°F), or until the
unit has run in cold start for at least 20 minutes. After one or
both conditions are met, the set point will be reset to the user
setting and the unit will run in the regular cool mode.
The indoor fan will operate according to the user settings for
mode – Continuous or Cycle and Speed.
Cold start is not available with the Sleep feature.

Sleep Function

Sleep time is adjustable by the user from 1 to 15 hours in one
(1) hour increments in a closed loop. The sleep time is adjusted
and set via the touch pad and by pressing the Sleep Button
repeatedly. On the touch pad, the display will show the set
time in numbers for five (5) seconds. Before the sleep time
expires, the setting can be adjusted above the number of hours
passed by pressing the Sleep Button. Pressing the On/Off
Button can terminate the Sleep Mode.
A changeover from Heat to Cool or another Mode will reset
the Sleep Timer.
The Sleep Function will be deactivated by pressing the power-
on-reset or any button (except sleep) on the touch pad or the
Remote Control.
Cool Dry Mode
Select the Cool Dry Mode when the standard Cool Mode does
not provide sufficient dehumidification. In Cool Dry Mode,
the unit must run in Cool Mode for 12 minutes or until the
temperature differential between the room temperature and
the set point is less than 2°F. This will also occur after a Cold
Start or a Mode change from Cool to Cool Dry. During this
time the fan will operate in the Mode and Speed selected.
Until one or both of the above conditions are met, the control
will determine which Dry Mode (Zone) is initiated based on
the temperature differential between the room temperature (Tr)
and the temperature set point (Ts):
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Figure 4. if Tr - Ts > 4°F, operation will be in Zone A
Figure 5. if 2°F < Tr - Ts < 4°F, operation will be in Zone B
Figure 6. if 0°F < Ts - Ts < 2°F, operation will be in Zone C
Figure 7. if Ts - Tr > 5°F, operation will be in Zone D
The other temperature ranges are dead bands for zone stability.
Figure 4. Zone A
Figure 5. Zone B
Compressor
Low Fan
Figure 6. Zone C
Compressor
Low Fan
Figure 7. Zone D
O n
O ff
O n
O ff
PTAC Digital Controls
Compressor
On
Off
Low Fan
On
Off
*
12 mins.
*
= Zone Determination Time
On
Off
8 mins.
4 mins.
On
Off
30 secs.
30 secs.
On
Off
6 mins.
6 mins.
On
Off
30 secs.
30 secs.
*
= Zone Determination Time
F an
Compressor
*
12 mins.
*
= Zone Determination Time
t
t
t
t
t
t
*
t
t
OM 813