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How to Select, Specify, Operate & Maintain
Dometic APU-Based Auxiliary Air Systems
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7,000, 10,000 and 14,000 BTU/hr capacities for all
size sleepers.
• Self-contained package units
• Patented split systems with reusable
precharged refrigerant linesets
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Heating options:
• 1- 4 kW built-in electric heat modules.
• Interface with installed diesel-re heaters.
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No special tools required to install.
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Turnkey package includes all components needed
to complete installation.
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Backed by extensive application engineering
support and nationwide service.
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Designed and built for over-the-road conditions and
thoroughly eld-tested.
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ometic Corporation, Environmental Division, with a 45+ year heritage in
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rugged HVAC technology for harsh-environment applications, has developed
a range of auxiliary air conditioning and heating solutions to meet the increasing
demand for engine-off comfort control in the trucking industry.
You can count on Dometic for thoroughly engineered products designed for the
harshest over-the-road conditions backed by unmatched factory support and
after-sale service. That’s why so many leading APU manufacturers currently
specify or recommend Dometic HVAC with their products for the trucking market.
In this booklet, we’ll explain all aspects of selecting, specifying, operating and
maintaining your APU-powered auxiliary air system from Dometic. We encourage
you to read this information carefully to help you make decisions. If you have any
questions, please call us and we’ll be delighted to help you.
How to Select, Specify, Install, Operate & Maintain Dometic APU-Based Air Systems 2
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he basic principle of an air conditioner is the transfer of heat from one place to another – in this case
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from the inside of your vehicle to the outside. This is accomplished by absorbing heat from the inside
air into a refrigerant gas owing through an evaporator coil. The refrigerant is then pumped to a condenser,
where the heat is released to the outside air. The refrigerant, a chemical with a low evaporation temperature,
ows around a closed loop, driven and pressurized by a compressor. As a part of the cooling process, the
air conditioner also removes moisture from the inside air, which makes the area feel more comfortable and
keeps the compartment dry and mildew-free.
A belt-driven compressor on the truck’s engine supplies air conditioning whenever the engine is running. To
keep the driver comfortable when the engine is shut down, it is necessary to have a separate auxiliary air
conditioning system that uses an alternative source of power.
The auxiliary air system runs on 115 Volt AC power, which can be supplied by an onboard diesel genset,
often referred to as an auxiliary power unit, from a shorepower connection when an external AC power
source is available or in some cases from the truck’s batteries using an inverter to convert the 12 Volt battery
output into usable 115 Volt AC power. In this booklet we will focus on the APU-based solutions. In the next
chapter we will provide an overview of your air conditioning choices.
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There are two basic types of auxiliary air systems:
• Self-contained “package” units
• Split systems
The self-contained unit is designed to be wholly
mounted inside the truck, usually under a berth
or seat or inside a side storage locker. All of
the air conditioning components, including the
compressor, condenser, evaporator, blower and
power supply, are mounted on a single low-prole
chassis with an aluminum cover. The system’s
closed refrigerant loop is precharged and sealed
at the factory. Inside air is pulled across the
evaporator coil, and cooled air is blown through
a exible duct to a discharge grill for discharge
into the living area. Hot air is discharged from the
condenser through cutouts in the oorboard.
Dometic’s patented split systems consist of two
separate modules. The outside unit contains
the condenser and cooling fan. It can be bolted
horizontally to the underside or vertically to the
back of the sleeper. The inside unit contains the
compressor, evaporator, blower, power-logic
box and other associated components.The
compressor is covered by a sheet-metal cover.
The inside unit is mounted under a berth or seat
or in a side storage locker. The two units are
connected by reusable precharged quick-connect
refrigerant linesets. The system is designed so
that both units automatically charge to the correct
refrigerant pressure as soon as the linesets are
connected. No special tools are required.
Each approach offers advantages and
disadvantages. A self-contained unit is simpler to
install and maintain, since it does not have any
external refrigerant lines. It is also less expensive
than a split system of the same BTU/hr capacity.
On the other hand, it takes more interior space,
and it requires cutting holes in the oor for air to
ow to and from the condenser. A split system, on
the other hand, has more installation exibility and
uses less interior space. It also is quieter, since the
condenser fan is located outside the truck.
Both types of air conditioning systems are
available with a selection of built-in electrical
heat modules. The heat is blown through the
same ducts and grills and controlled by the same
thermostat. They can also be used in conjunction
with a diesel-red heater if desired, under control
of the same thermostat.
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Heating Capacity Application*
1.0 kW 48 in. sleeper
1.5 kW 60 in. sleeper
2.0 kW 72 in. sleeper
Model
ECEQ7 7,000 Cooling Only Smart Digital
EHCEQ7 7,000 1 kW Smart Digital
ECEQ10 10,000 Cooling Only Smart Digital
EHCEQ10 10,000
EHCEQ10 10,000 1.5 kW Smart Digital
EHCEQ10 10,000 2 kW Smart Digital
ECEQ14 14,000 Cooling Only Smart Digital
EHCEQ14 14,000 1.5 kW Smart Digital
EHCEQ14 14,000 2.5 kW Smart Digital
EHCEQ14 14,000
EHCEQ14 14,000
ACCD7 7,000 N/A N/A
ACCE10 10,000 N/A N/A
ACCE14 14,000 N/A N/A
ASCF7 7,000 Cooling Only Mechanical
ASCEQ7 7,000 Cooling Only Smart Digital
ASCEQ7 7,000
ASCEQ7 7,000 1 kW Smart Digital
ASCEQ7 7,000 1.5 kW Smart Digital
ASCDQ10 10,000 Cooling Only Smart Digital
ASCDQ10 10,000 1.5 kW Smart Digital
ASCDQ10 10,000 2 kW Smart Digital
ASCDQ14 14,000 2 kW Smart Digital
ASCDQ14 14,000 2.5 kW Smart Digital
Cool Capacity
(BTU/hr)
Heat Capacity Control Height Width Length Weight Cool Amps Heat Amps Refrigerant
Internal Unit – Evaporator/Heater/Compressor
7,500 BTU/hr
Espar Ready
2.5 kW,
2-stage
4.0 kW,
2-stage
7,500 BTU/hr
Espar Ready
Smart Digital
Smart Digital
Smart Digital
Smart Digital
Split Systems
11.75" 10.25" 19.25"
11.75" 10.25" 19.25"
11.63" 11.12" 20.19"
11.63" 11.12" 20.19"
11.63" 11.12" 20.19"
11.63" 11.12" 20.19"
11.69" 13.00" 22.00"
11.69" 13.00" 22.00"
11.69" 13.00" 22.00"
11.69" 13.00" 22.00"
11.69" 13.00" 22.00"
External Unit – Condenser
6.125" 11.3125" 21.875"
6.125" 12.50" 24.50"
6.625" 12.50" 24.50"
Self-Contained Systems
12.5" 15.25" 21.50"
11.94" 17.75" 24.00"
11.94" 17.75" 24.00"
11.94" 17.75" 24.00"
11.94" 17.75" 24.00"
12.50" 20.87" 28.25"
12.50" 20.87" 28.25"
12.50" 20.87" 28.25"
12.50" 20.87" 31.50"
12.50" 20.87" 31.50"
* Under normal conditions. Whichever
type of system you select, it will come
with ducts, grills, condensate drains,
thermostat controls and electrical wiring.
53 lb. 7.3 N/A R417a
53 lb. 7.3 8.2 R417a
60 lb. 11.8 N/A R417a
60 lb. 11.8 1.0 R417a
60 lb. 11.8 13 R417a
60 lb. 11.8 17 R417a
64 lb. 14.5 N/A R417a
64 lb. 14.5 13 R417a
65 lb. 14.5 21 R417a
65 lb. 14.5 11.4 + 10.4 R417a
65 lb. 14.5 23.2 + 12.1 R417a
10 lb. N/A N/A R417a
12 lb. N/A N/A R417a
13 lb. N/A N/A R417a
62 lb. 8.5 N/A R22
70 lb. 8.9 N/A R417a
70 lb. 8.9 1.8 R417a
71 lb. 8.9 9.5 R417a
71 lb. 8.9 13.4 R417a
91 lb. 12.9 N/A R22
91 lb. 12.9 13.9 R22
91 lb. 12.9 18.2 R22
104 lb. 15.7 19.0 R22
104 lb. 15.7 23 R22
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About Insulation
Before we go any further, let’s talk briey about insulation. Most truck sleepers today are insulated with a
value of approximately R 1 to R 1.25. Compare this to the insulation of R 30 that is required in most new
housing construction. Even the “cold-weather packages” offered with some new trucks only have insulation
values of R 2. TMC recommended practices call for R 4.2 as a standard insulation package and greater
than R 4.6 in a premium package. This standard, once adopted by the industry, will go a long way toward
improving the performance of auxiliary air conditioning and heating systems.
If you are buying a new truck, you should order it with additional insulation. There are also a number of
measures you can take to reduce the heat load in your truck. If you have skylights, cover them. Insulate
the oors with foam under the carpet. Add insulation to the doors. Get heavy-duty curtains to separate the
sleeper from the cab. Cover the windshield and windows with reective shades when parked. Park in the
shade whenever possible. Switch off heat-producing appliances in the sleeper.
Air Conditioning Units
Your rst step will be determining the type of air conditioning units (split or self-contained) to meet your
requirements and space constraints, then sizing the units to meet the expected heat load.
Sizing the system can be a complicated affair, since it depends on a number of factors, such as the size and
shape of the sleeper, the amount of insulation (see above), the size and location of windows, the color of the
truck (darker colors absorb more heat) and the ambient temperature outside. The following guidelines are
based on TMC recommendations under “average” conditions. If you are operating in very hot regions, you
may need to consider extra capacity.
7,000 BTU/hr Day cab or smaller sleeper up to 48 with flat roof
10,000 BTU/hr Mid-size 60 sleeper with low or mid-height roof
14,000 BTU/hr Full-size 60-72 sleeper with high-rise roof
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Auxiliary Power UniT
When running the air conditioner from an APU, the genset must be large enough to start and run the air
conditioning unit as well as any other electrical appliances you may wish to run at the same time. This can be
complicated, since gensets from different manufacturers may vary considerably in their output characteristics.
If you measure the output of two gensets rated by their manufacturers at 2.5 Kilowatts, you will observe them
to be very different.
It’s also important to allow for the surge capacity needed to start the air conditioning compressor. Each
time the compressor cycles on, there is a short electrical surge that is equal to about four times the normal
running amps for several hundred milliseconds. Most good-quality gensets are designed to support these
short surges without tripping off the line.
Capacity in BTU/hr
7,000 2.0 38
10,000 2.5 60
14,000 3.0 70
Genset Minimum Output
(Continuous kW)
Genset Minimum Surge
Amps
Shorepower
Although there are relatively few shorepower hookups available at truck stops, rest stops and terminals,
these will become more readily available in the future.
TMC recommends a minimum 20-amp circuit for shorepower connections. You should use any heavy-duty
power cord with a standard three-prong plug. Remember that there will be a voltage drop across the cord, so
you should use the minimum length necessary to reach your outside power source.
12 Gauge Cord
10 Gauge Cord
Up to 25'
Up to 50'
How to Select, Specify, Install, Operate & Maintain Dometic APU-Based Air Systems 8
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Installation
Dometic will provide detailed installation instructions with your system. You should make sure you understand
these instructions and follow them completely.
Note that the APU must be set to deliver 115 Volt 60 Hz output in order for the air conditioner to function
properly. Check with your APU supplier.
Controls
The Dometic auxiliary air system comes with a standard digital thermostat/display unit. Operation is intuitive
and easy, with up and down arrows to adjust the setpoint and fan speed.
Optimizing Performance
To improve the air conditioner’s performance on a hot day, you can reduce the heat load by parking in a
shaded area, covering the windows with reective shades to block out direct sunlight and pulling the curtain
between the sleeper and cab. Make sure windows and doors are tightly closed, and turn off any other heat-
producing appliances.
Operation and Maintenance
You should inspect and clean the air lter regularly to ensure good airow across the evaporator coils. You
will nd the lter in the return air path, either directly behind the grill or in front of the evaporator coil.
Make sure you do not block the airow between the return air grill and evaporator coil with pillows, blankets,
papers or other objects.
Check the condensate drain often to make sure water is draining properly. Make sure the drain ttings do not
get clogged. Note that the drain hose under the truck should be tied in a loop so as to form a natural trap.
This will help prevent outside air and exhaust discharge from getting inside.
If you have a split system with external condensing unit, make sure you inspect and clean any debris from
condenser coil area to ensure good air ow.
Dometic’s auxiliary air systems, both self-contained and split, are designed so that you should never need to
recharge the refrigerant loop under normal circumstances. If the refrigerant level ever needs to be adjusted,
federal law requires that it must be done by an EPA-licensed HVAC technician with the proper tools to avoid
accidental discharge of any refrigerant gas into the air.
Occasionally check for chafe on outside wires and refrigerant lines (split systems).
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Dometic Environmental Corporation
www.DometicTruck.com
American Transportation Research Institute
www.atri-online.org
ATA Green Truck Initiative
www.greentruck.com
ATA Technology and Maintenance Council (TMC)
www.truckline.com/issues/governmentpolicy/environment
California Air Resources Board
www.arb.ca.gov
Canadian Office of Energy Efficiency
http://oee.nrcan.gc.ca/transportation/eetsmart.cfm
Cascade Sierra Solutions
www.casadesierrasolutions.org
Environmental Protection Agency SmartWay Program
www.epa.gov/smartway
Pennsylvania Office of Energy and Technology Development
www.dep.state.pa.us
U.S. Department of Energy Clean Cities Program
www.eere.energy.gov/cleancities
West Coast Collaborative
www.westcoastdiesel.org
How to Select, Specify, Install, Operate & Maintain Dometic APU-Based Air Systems 10
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Dometic is a customer driven, world-leading provider of innovative leisure products for
the caravan, motorhome and marine markets. Dometic offers a complete range of air
conditioners, refrigerators, awnings, cookers, sanitation systems, lighting, windows, doors
and other equipment that makes leisure life more comfortable away from home.
Dometic also provides refrigerators for specic use in hotel rooms, offices, and for storage
of medical products and wine along with comfort products designed for the over-the-road
truck market. Dometic’s products are sold in almost 100 countries and are produced
mainly in Dometic’s own production facilities around the world. Dometic has more than
4,400 employees.
ISO 9001:2000
ID: 2522 R ev. 20080729
Dometic Corporation, Environmental Division
P.O. Box 15299
Richmond, VA 23227
Phone: 804-746-1313 Fax: 804-746-7248
Email: sales@DometicTruck.com
Website: www.DometicTruck.com
Patents. 7,171,822 • 7,234,315 B2 • 7,140,192 • 7,316,119 • 7,237,397 B2
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