Digitair Product Information - Amana PTAC Service Instructions Manual

SERVICING
DigiAIR™ PRODUCT INFORMATION
The Amana brand PTAC factory installed DigiAIR™ module
is a "make–up air" system to assist in providing outside
air into a room (living space) to replace ventilation air that
is usually removed through an exhaust air system in bath-
room areas. This exhausted air creates a negative air pres-
sure in the room and the DigiAIR™ make up air system is
designed to move most of the needed replacement outside
air to enter the room through the DigiAIR™ dehumidifica-
tion module. To assist in this needed outside make up air
to be directed to come through the DigiAIR™ dehumidifica-
tion module, a fan in the module operates continuously (as
long as the module is properly maintained and powered), to
provide positive pressure through the DigiAIR™ module to
the inside room.
The DigiAIR™ Amana brand PTAC is a 2 compressor system.
The Amana brand R410A PTAC system is used to assist in
control of the sensible heat (room temperature) and latent
load (moisture) that is brought into the room by the DigiAIR
system and also the typical sensible and latent loads cre-
ated in the room from occupants and typical air infiltration.
The DigiAIR™ module is an R134A compressor system de-
signed to continuously provide outside make up air at rates
of up 75 CFM (dependent on the room's negative pressure
*). The outside air entering the room through the DigiAIR™
module is first filtered, to assist in keeping the DigiAIR™
coils clean, and then dehumidified. The DigiAIR™ dehu-
midification is engaged at outside air temperatures and
humidity levels (RH%: Relative Humidity) when the air en-
tering the room generally should have moisture reduced
before it comes into the room.
The DigiAIR™ compressor/dehumidification process is con-
trolled both by a humidity sensor and temperature sensor
that monitor the outdoor environment. The DigiAIR™ mod-
ule is factory pre-set at
50% RH: > 46° F and < 68° F
40% RH: > 68° F and < 78° F
25% RH: > 78° F
When the outdoor humidity (RH %) and temperature levels
are above the DigiAIR™ settings, the compressor and dehu-
midification process begins. If the outdoor humidity level
drops below the RH% settings at the temperatures above or
the outdoor temperature drops below 48° F the compressor
dehumidification operation ceases. The DigiAIR™ dehumidi-
fication RH% can easily be adjusted through the Amana brand
PTAC touch pad, if changes to the factory preset RH% are
desired. The 25% RH setting can be adjusted to as low as
15% or as high as 60%. The factory preset ranges are based
on HVAC industry psychometric chart sensible temperature
and humidity ratios that would generally require outside air
to be dehumidified before being introduced into a room
and should suffice from most applications.
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A temperature sensor (brown thermistor) monitors the re-
frigeration temperature coming into the compressor (suc-
tion line) to protect against potential liquid refrigerant en-
tering the compressor. If refrigerant temperatures are too
low, the compressor will be cutoff to help protect the com-
pressor from liquid refrigerant damage. A temperature
sensor (green thermistor) monitors the outdoor air tem-
perature, and if the temperature falls below 48°F, the com-
pressor is disabled. Generally, at air temperatures below
48° F, the air coming through the DigiAIR™ module does
not need to be dehumidified before entering the indoor room.
Additionally, since the dehumidification coil (evaporator)
is generally operating 12° F to 18° F below the outdoor
temperature, the compressor should be cut off to prevent
the evaporator coil from frosting or icing and not being
able to exchange heat. A frosted or iced coil cannot dehu-
midify the incoming air. All dehumidifier controls and safety
features are automatically reset.
The DigiAIR™ fan, when the unit is properly powered and
maintained, will operate 24/7/365 to provide continuous
outside makeup air, even when the compressor is not oper-
ating. For installation locations where the winters are cold,
or it is desired to warm the air coming through the DigiAIR™
system before it enters the room, an optional 250 watt elec-
tric heater is available for the make-up air system.
Condensate water generated from the DigiAIR™ dehumidi-
fier operation drains directly into the PTAC's exterior base
pan. When the PTAC's R410A compressor is operating in
the cooling mode, and the outside air temperature is above
60° F, condensate water in the PTAC's exterior base pan
will be picked up and slung onto the condenser coil for re-
evaporation to the outside air. Excess condensate is drained
into the PTAC's wall case from which it can drain either to
the outside through the drain holes in the sleeve or piped to
a drainage system with the use of an optional drain kit.
Since condensate water can be generated from the PTACs
compressor operation in either the cooling mode or, in the
case of a heat pump, during reverse cycle operation plus
the added condensate water generated from the DigiAIR™
dehumidification operation, a piped condensate drain sys-
tem is highly recommended.
• NOTE: A DigiAIR™ module is intended to work in con-
junction with a building exhaust system. As an ex-
ample, to obtain 55 CFM of outside makeup air, the
room exhaust ventilation system needs to create a
0.053 (inches H2O) negative static pressure in the in-
door conditioned room. CFM can be increased or de-
creased by increasing or lowering the negative static
pressure created by the property ventilation system.
The DigiAIR can provide up to 75 CFM when negative
static pressures are increased to a high enough level.
Failure to properly exhaust the air introduced by the
DigiAIR™ makeup air module will result in poor perfor-
mance of both the outside air volumes (CFM)
proper dehumidification of the makeup air.
This unit is shipped, tested and rated with the dehumidifi-
cation switch off.
and the