Homes without air ducts could pose problems with central air conditioning installation; however ductless mini-split heat pumps offer a solution. A heat-pump split system services the entire house through an indoor unit and outdoor unit. The indoor unit uses refrigerant tubes to pump refrigerant to air handler coils, which provide air flow from the heat pump to multiple rooms without the need for duct-work. The outdoor unit uses an air compressor and condenser to pipe refrigerant through lines that connect to the indoor unit. Properly installing a ductless mini-heat pump system requires an adequate electrical and mechanical background.
Things You'll Need
Heat-pump split system assembly
Factory instructions, diagrams and parts list
One sheet-metal baffle, 6½-inch
Refrigerant-grade copper tubing
Refrigerant leak detector
Vacuum pump instructions
Two hex wrenches, 3/16-inch
60 C wire
Electrical control box wiring diagram
Control wiring, 24 Vacuum NES Class I insulated 18 AWG
Use the shipment invoice to verify whether the manufacturer shipped the correct heat-pump split system assembly. Pay close attention to any damage incurred during shipment. Notify the freight carrier and manufacturer immediately upon discovery of damages. Consult the National Electrical Code and local building codes before proceeding with installation. Switch off the main power disconnect to avoid electrical shock. Wear protective goggles, gloves, steel-toed shoes and ear muffs to minimize risk of injury or death.
Situate the heat-pump split system away from highly trafficked areas, such as bedroom windows, patios or decks connecting to family rooms. Install a level mounting pad 2 inches larger than the outdoor segment of the heat-pump split system unit. Avoid direct contact with the building's structure to reduce noise transmission.
Elevate the heat-pump split system unit in accordance to local code requirements. Prop the unit onto a snow stand to ensure adequate clearance from rainfall and snow accumulation. Attach the snow stand with tie-down bolts and knockout fasteners. Position the heat-pump split system on a level mounting pad 6 inches above the roof surface for roof installation. Isolate the heat-pump split system unit and refrigerant tubing by placing the unit above a load-bearing wall. Allow space for vibration absorption between the unit and building structure. Consult local building codes relevant to roof-top installations. Place one 6½-inch sheet metal baffle over the defroster coil panel in order to buffer against high-velocity winds. Be sure the unit measures within 2 and 3/8 inches per foot.
Route refrigerant-grade copper tubes not exceeding 50 feet. Avoid cutting the refrigerant tubes until establishing the evaporator and condenser connections. Do not remove the copper caps at the tube ends until establishing the evaporator and condenser connections. Route the refrigerant tubing away from sharp bends. Use a suspension hanger to isolate and fasten liquid and suction lines away from floor and ceiling joists. Use foam-sleeves to insulate the suction lines, especially long liquid lines exceeding 30 feet in diameter. Run refrigeration line sets to minimize length, making sure to avoid direct contact with the structure's foundation. Insulate the wall openings with sound-dampening material when routing refrigerant lines through the structure.
Cleanse refrigerant tube end with an emery cloth. Connect the refrigerant tubing to the swage connection. Use wet rags to prevent the refrigerant tubing from overheating. Pump dry nitrogen through refrigerant lines to prevent oxidation. Use a brazing alloy to braze the copper ends. Do not remove the wet rags until completing the brazing process.
Apply 2 oz. of vapor refrigerant into the refrigerant line set, then pressurize using 150 psig of dry nitrogen. Use a refrigerant leak detector to locate leakages. Relieve all pressure from the refrigerant line sets before beginning the evacuation process. Connect the vacuum pump to the manifold gauge center hose. Connect the manifold gauge center hose to a refrigerant cylinder to eliminate unnecessary changing of hoses. Do not budge valves from closed position. Consult the vacuum pump factory instructions. Evacuate the heat-pump split system to 300 microns and allow it to run for an additional 15 minutes. Switch off the service pump, but do not disconnect the service valves. Check all connections if the unit does not hold 500 microns. Close the gauge's shutoff valves and isolate the vacuum pump from the system. Disconnect the vacuum pump.
Use a 3/16-inch hex wrench to remove the 3/8-inch service valve cap after evacuating the connection lines, then insert the hex wrench into the valve stem. Use a second 3/16-inch hex wrench to dislodge the valve stem. Torque the hex wrench counterclockwise until the valve stem reaches the edge. Torque the service valve cap in compliance with the service valve's 8 to 11 foot per pound specifications.
Use 60 C wire for all electrical connections. Secure ground connections for the outside unit. Be sure that the power supply meets the rating on the unit's nameplate. Route voltage power supply lines to the heat-pump split system unit from a suitable disconnect switch. Follow the attached wiring diagram located on the inside panel of the electrical control box. Use copper wire exclusively for the connection between the disconnect switch and the unit. Remove the access panel located on the electrical control box to start the wiring process. Route disconnect switch wires through the power wiring outlet and into the electrical control box. Use 24 Vacuum NES Class I insulated 18 AWG for control wiring. Use the factory instructions to properly install the room thermostat. Do not mount the room thermostat to exterior walls, making sure to avoid exposure to the elements. Separate all low voltage control wiring from existing power leads.