MYPOCKETTECH · LEARNING POD
Understand the cooling. Follow the airflow. Know what to check when your RV feels too warm.
An illustrated reference for RV owners, from campground cooling to battery-powered systems.
LESSON 01
Start with the model label and power source. The roof shape alone does not tell you how the unit is powered.
The familiar roof-mounted unit, powered by shore power, a generator, or a suitably sized battery inverter. Common brands include Coleman-Mach, Dometic, Furrion and GE. Many fit a nominal 14 × 14 inch opening; verify roof, opening and ceiling-assembly requirements.
Runs from a matching DC battery system without a separate AC inverter. Many use a variable-speed compressor. Capacity and power vary considerably; DC does not automatically mean a smaller unit or zero startup current.
An indoor head and outdoor condenser move heat through refrigerant lines. Many mini-splits require 120V or 240V AC; only models specifically rated for DC can connect directly to a compatible battery system. Installation needs secure mounts, airflow and a proper drain.
Supplemental or alternative cooling when safely installed and vented. Window units can be efficient; single-hose portables often draw warm replacement air inside. Account for window security, drainage, exhaust, travel storage and lost floor space.
Provides cooling and air circulation. Heating requires another appliance.
Reverses the refrigeration cycle to move heat inside. Low-temperature performance and furnace changeover depend on the model.
Uses electric resistance to add gentle warmth. It consumes substantial electrical power and does not replace a properly sized furnace.
13,500 and 15,000 BTU/h are common rooftop ratings. Small RVs often use one unit; long or high-heat-load rigs may need two. Length is only a starting point: windows, insulation, slides, sun exposure and climate all matter.
An oversized fixed-speed unit can shut off too quickly to remove moisture well. Variable-speed models adjust their output instead of simply turning fully on and off. Match capacity, roof support, ducts, thermostat and electrical service before choosing an upgrade.
LESSON 02
Your AC moves heat from inside your RV to the outdoors. Refrigerant stays in a sealed loop; indoor and outdoor air travel in separate paths.
Raises the refrigerant pressure and temperature, sending hot vapor toward the outdoor coil.
Releases heat to outside air; refrigerant condenses into liquid.
Restricts flow and lowers refrigerant pressure before the indoor coil.
Absorbs heat from return air as refrigerant boils. Vapor returns to the compressor, repeating the cycle.
Swipe sideways on a narrow screen to view the whole diagram. Conceptual cooling-mode schematic. The metering device may be a capillary tube or expansion device; layouts vary.
Raises the pressure and temperature of the refrigerant vapor. It does not create cold air directly.
A return-to-supply air temperature drop around 15–20°F is a common rough cooling check, not a promise that your RV can only cool 20°F below the outdoor temperature. Humidity, airflow and the model affect that difference.
The RV keeps recirculating and cooling its indoor air. Shade, insulation and heat entering through windows determine how well it can keep up. Use a probe thermometer in the air stream; an infrared thermometer reads surface temperature.
LESSON 03
Indoor air crosses the evaporator and returns to your living space. Outdoor air crosses the condenser and carries heat away.
Cabin air passes through the filter and indoor evaporator coil.
Cooled air returns to the cabin through the ceiling outlet or sealed ductwork. Keep return and supply paths separated.
Water removed from cabin air collects at the evaporator and exits through the unit’s designed drain path, often onto the roof. Some rigs use dedicated drain lines.
The compression gasket keeps outside water out of the roof opening. A failed gasket or blocked condensate path can cause an indoor leak.
On phones, swipe sideways to explore the full airflow view.
From the roof seal to the ceiling filters, each part has a job. Select a number to learn more.
Protects the rooftop hardware. Inspect for cracks, damage and loose fasteners.
Conceptual assembly illustration. Fastener details, grilles, controls and component placement vary; use your model’s instructions for installation.
Cool air travels through ceiling ducts to vents around the rig. Keep the vents open and clear. Leaks, crushed ducts or a poorly sealed return/supply divider can reduce airflow and cooling.
The ceiling assembly separates warm return air from cool supply air. A loose divider or bad seal lets cold air cycle straight back into the intake before cooling your RV. Ceiling assemblies and thermostats must match the unit and distribution system.
Moisture condenses on the cold evaporator and collects in a pan. Many rooftops drain onto the roof; some use drain tubes or pumps. Clear the model’s drain path without disturbing seals or wiring. Water dripping inside needs investigation, especially after rain.
Close windows and roof vents, shade sunny glass, reduce cooking heat and start cooling before the RV gets hot. Keep rooftop condenser airflow unobstructed. Follow the RV’s leveling guidance and the AC’s installation requirements so water can drain correctly.
Choose a numbered part to see its care guidance.
Click a number or choose a labeled button below. Conceptual illustration; component positions vary by model. The roof gasket is beneath the unit and is not shown.
Shroud
Inspect for cracks, loose fasteners, missing hardware and insect nests. Use only a protectant approved for the shroud material. Reinstall correctly before travel.
Protects the rooftop hardware. Inspect for cracks, damage and loose fasteners.
Houses the coils, fans and compressor. Outdoor air releases heat while the separated indoor air path provides cooling.
Seals between the rooftop base and the RV roof. Use the correct replacement gasket and the manufacturer’s compression or torque specification; this is not a seal between the shroud and the coils.
Must match the unit’s opening, roof-thickness and structural requirements. The roof must support the unit and safe service access.
Secure the rooftop unit from below. Tightening compresses the roof gasket. Follow the exact mounting sequence and specification; avoid guessing by feel.
Directs supply air and collects return air. Clean reusable filters or replace disposable ones, and keep the warm-return and cool-supply divider sealed.
Controls may be on the ceiling assembly or a separate wall thermostat. Verify cool mode, zone and setpoint; many systems require 12V control power even when the compressor uses 120V AC.
Protect the equipment Inspect for cracks, loose fasteners, missing hardware and insect nests. Use only a protectant approved for the shroud material. Reinstall correctly before travel.
The indoor cooling coil A dirty coil restricts cooling airflow. Have inaccessible coils cleaned safely with a product and method approved for the model. Keep cleaners and rinse water away from electronics; protect the interior. Do not assume a coil’s location from another brand.
The outdoor heat-release coil Remove leaves and debris gently. Use a soft brush or manufacturer-approved low-pressure cleaning method. Never use a pressure washer; protect delicate fins and electrical parts. A technician can straighten fins with the correct fin comb.
Let condensation leave Check the drain pan, holes and any tubes or pump for blockage. Clear gently according to the unit’s instructions. Do not enlarge drain holes or spray into the RV. Persistent indoor water may also involve icing or a roof-gasket leak.
Technician service area The compressor, capacitors and wiring belong in a technician inspection. Capacitors can retain a dangerous charge after power is disconnected. Appearance alone does not prove a capacitor is good; do not touch terminals or attempt to discharge it with a tool.
LESSON 04
Compare watts and usable watt-hours—not just battery amp-hours. Two batteries with the same Ah rating can store very different energy at different voltages.
Illustrative calculation using average electrical input, including cycling. Use measurements or your model’s data.
5,600 Wh
About 233 Ah at 24V
Average current: about 29.2A
This is the energy consumed, not a recommended bank size. Leave a reserve for other loads and usable discharge limits. Actual voltage, conversion losses, standby loads, outdoor temperature and humidity affect runtime. Night cooling needs stored energy; daytime solar output is variable.
700W ÷ 12V ≈ 58A
700W ÷ 24V ≈ 29A
700W ÷ 48V ≈ 15A
Higher voltage lowers current at the same power. It does not reduce the cooling energy required.
An electronic soft starter controls compressor starting to reduce inrush on compatible fixed-speed AC units. A hard-start capacitor kit assists starting by a different method. Neither makes running watts disappear. Confirm compatibility, especially for variable-speed equipment.
One 30A/120V RV connection provides up to 3,600W total. Standard 50A RV service has two 120V legs and up to 12,000W total. Running two ACs depends on their loads, other appliances and power management; 50A is common, but not an absolute requirement. Generator output can fall with heat and altitude—use its manual.
Wire and fuse by the installation manual. Higher voltage can simplify high-power distribution, but cable length, allowable voltage drop, ampacity and overcurrent protection still matter. Feed the RV’s 12V equipment through a properly sized DC-DC converter when using a higher-voltage bank.
LESSON 05
Keep the air paths clean and catch small problems early. Use these checklists alongside your model’s maintenance instructions.
Inspect filters more often in dust, smoke or pet hair. Follow your manual’s interval.
Checklist selections last only while this page remains open.
Mounting bolts: use the specified torque or gasket compression. Over-tightening can distort the seal; loose or uneven compression can leak. “Snug” by feel is not a substitute for the model’s instructions.
Many rooftop units have sealed circuits without routine charging ports. A suspected leak needs a qualified diagnosis. Repair or replacement depends on the unit, warranty, refrigerant and economics. Weak cooling alone does not prove refrigerant loss.
LESSON 06
Check the simple owner-accessible items, then know when the problem needs a technician.
Check the filter and open vents first. Close doors/windows and reduce solar heat gain. Check for a frozen evaporator or supply air leaking straight into the return. If airflow is good but performance remains poor, arrange model-specific electrical and refrigeration diagnosis.
Turn cooling off. Use fan-only, usually high if the manual allows, until fully thawed. Never chip ice off or keep running the compressor against an iced coil. Check filters, vents and coils; low ambient temperature, freeze-sensor problems or refrigerant faults can also cause icing. Repeated freezing needs service.
Turn cooling off if water is reaching electrical areas. Determine whether it happens during cooling or during rain. Cooling leaks can involve blocked drains, a drain pump/tube, icing or pan problems; rain leaks may involve the roof gasket or nearby roof seals. Do not tighten bolts blindly.
Allow the restart delay specified for the model. Reduce competing electrical loads and confirm suitable supply power without opening electrical enclosures. A capacitor, control, overload or compressor fault needs technician testing. An inverter-driven compressor may not use the same capacitor arrangement.
Check thermostat mode, setpoint and zone. Check the pedestal/supply and RV breaker from their normal accessible controls. Many 120V units also need 12V control power. A direct DC unit needs its battery/BMS supply. A breaker that trips again needs investigation; do not repeatedly reset it.
Keep doors/windows closed. Short cycling, low airflow, high moisture load and oversized fixed-speed equipment can reduce dehumidification. Follow fan-mode recommendations for the model and use a dehumidifier if needed. Lowering the thermostat alone does not fix the cause.
Burning smells, smoke, damaged cords, repeated breaker trips, water near electrical parts, or persistent compressor faults call for shutting the system down and getting help. Do not bypass breakers, freeze sensors or other protection.
Share the model number, power source, outdoor conditions, thermostat settings, airflow symptoms, whether cooling or rain causes leaks, and what changed. Record service and cleaning in your myPocketTech Maintenance Log Book.
Reference guidance: Airxcel / Coleman-Mach: RV Air Conditioning Made Easy; Dometic model manuals and support; Micro-Air EasyStart; Nomadic Cooling DC models. Reviewed October 8, 2026. Ratings and requirements vary by model; use the current installation/operation manual for voltage, roof opening, mounting torque, maintenance and operating limits. Power calculations are illustrative. Product artwork is conceptual and is not an installation or wiring diagram.