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508133G01 / 31-5000715

Page 23 of 25

Issue 2140

defrost cycle to satisfy a heating demand; however, 

the unit will run to normal operation at the conclusion 

of the defrost cycle.

In case of extended power outage...

If the outdoor temperature is below 50°F and power to your 

outdoor unit has been interrupted for one hour or longer, 

observe the following when restoring power to your heat 

pump system.
•  Set the room thermostat selector to the “Emergency 

Heat” setting to obtain temporary heat for a minimum 

of 6 hours. This will allow system refrigerant pressures 

and temperatures enough time to return to a stabilized 

condition.

•  In Emergency Heat mode, all heating demand is 

satisfied  by  auxiliary  heat;  heat  pump  operation  is 

locked out. After a 6 hour “warm-up” period, the 

thermostat can then be switched to the “Heat” setting 

and normal heat pump operation may resume.

Thermostat Operation

The wall-mounted thermostat controls your heat pump. 

The thermostat is available in various configurations from 

different manufacturers. The information below is typical for 

most thermostats. Ask your dealer for specific information 

regarding the model of thermostat installed.

Fan Switch

In AUTO or INT (intermittent ) mode, the blower operates 

only when the thermostat calls for heating or cooling. This 

mode is generally preferred when humidity control is a 

priority. 

The ON or CONT mode provides continuous indoor 

blower operation, regardless of whether the compressor or 

auxiliary heat are operating. This mode is required when 

constant air circulation or filtering is desired.

On models without a fan selection switch, the fan will cycle 

with the outdoor unit.

System Switch

Set the system switch for heating, cooling or auto 

operation. The auto mode allows the heat pump to 

automatically switch from heating mode to cooling mode to 

maintain predetermined comfort settings. Many heat pump 

thermostats are also equipped with an emergency heat 

mode which locks out heat pump operation and provides 

temporary heat supplied by the auxiliary heat.

Indicating Light

Most heat pump thermostats have an amber light 

which indicates when the heat pump is operating in the 

emergency heat mode.

Temperature Indicator

The temperature indicator displays the actual room 

temperature.

Programmable Thermostats

Your system may be controlled by a programmable 

thermostat. These thermostats provide the added feature of 

programmable time-of-day set points for both heating and 

cooling. Refer to the user’s information manual provided 

with your particular thermostat for operation details.

Important System Information

•  Your system should never be operated without a clean 

air filter properly installed.

•  Return air and supply air registers should be free from 

restrictions or obstructions to allow full flow of air.

IF YOUR SYSTEM DOES NOT WORK, BEFORE 

REQUESTING A SERVICE CALL:

1.  Ensure thermostat is set below (cooling) or above 

(heating) room temperature and that the system lever 

is in the “COOL”, “HEAT” or “AUTO” position.

2. 

Inspect your return air filter: If it is dirty, your heat pump 

may not function properly.

3.  Check indoor and outdoor disconnect switches. 

Confirm circuit breakers are ON or that fuses have not 

blown. Reset breakers/replace fuses as necessary.

4.  Inspect the outdoor unit for clogged condenser coils, 

(grass cuttings, leaves, dirt, dust or lint). Ensure that 

branches, twigs or other debris are not obstructing the 

condenser fan.

IF YOUR SYSTEM STILL DOES NOT OPERATE, 

CONTACT YOUR SERVICING DEALER.

Be sure to describe the problem, and have the model and 

serial numbers of the equipment available.
If warranty replacement parts are required, the warranty 

must be processed through a qualified distribution location.

Summary of Contents for NS18HMA

Page 1: ...ion and service performed by unqualified persons can result in property damage personal injury or death WARNING Sharp metal edges can cause injury When installing the unit use care to avoid sharp edge...

Page 2: ...ll safety codes Wear safety glasses and work gloves Use quenching cloth for brazing operations Have fire extinguisher available Read these instructions thoroughly and follow all warning or cautions at...

Page 3: ...m building not to exceed 1 4 per foot Figure 1 Slab Mounting Install on a Solid Level Mounting Pad The outdoor section is to be installed on a solid foundation This foundation should extend a minimum...

Page 4: ...warranty will be void if the drier is not installed Installation of Line Sets DO NOT fasten liquid or suction lines in direct contact with the floor or ceiling joist Use an insulated or suspension typ...

Page 5: ...listed in Table 3 Between 51 and 150 Linear Feet Crankcase heater and nonbleed port TXV factory installed No additional components required Vertical vapor riser must be sized to the vapor riser liste...

Page 6: ...iquid line size shaded row on the outdoor tonnage C Select the actual Total Linear Length of your system shown at the top of the table D The elevation listed in the table is the maximum allowed for th...

Page 7: ...ponents including line set and indoor coil must be an AHRI match with the unit in order to fulfill unit warranty requirements Fire Explosion and Personal Safety hazard Failure to follow this warning c...

Page 8: ...around the stubbed end of the check expansion valve and lightly lubricate the connector threads and expose surface of the Teflon ring with refrigerant oil 4 Attach the stubbed end of the check expans...

Page 9: ...ain round Do not crimp end of the line Remove service cap and core from both the vapor and liquid line service ports 1 2 LIQUID LINE SERVICE VALVE SERVICE PORT CORE SERVICE PORT CAP SERVICE PORT CORE...

Page 10: ...all water saturated cloths WHEN BRAZING LINE SET TO SERVICE VALVES POINT FLAME AWAY FROM SERVICE VALVE PREPARATION FOR NEXT STEP 7 WRAP SERVICE VALVES To help protect service valve seals during brazin...

Page 11: ...sig 1034 kPa Open the valve on the high side of the manifold gauge set in order to pressurize the line set and the indoor unit E After a few minutes open one of the service valve ports and verify that...

Page 12: ...r liquid refrigerant Open the manifold gauge valve 1 to 2 psig in order to release the vacuum in the line set and indoor unit G Perform the following Close manifold gauge valves Shut off HFC 410A cyli...

Page 13: ...1 is jumpered to Y2 in the outdoor unit Note that the published performance data is based upon the use of a two stage thermostat Refer to the NS18HMA field wiring diagram for a conventional 24VAC sing...

Page 14: ...hermostat Control Options Size Circuit and Install Service Disconnect Switch Refer to the unit nameplate for minimum circuit ampacity and maximum fuse or circuit breaker HACR per NEC Install power wir...

Page 15: ...100 30m 18 Temperature Rating 35 C Minimum More than 100 30m 16 Table 7 Conventional 24VAC Thermostat Wiring Route High Voltage and Ground Wires Any excess high voltage field wiring should be trimmed...

Page 16: ...RMOSTAT W L Y2 Y1 O DS C I I R DF TST Y1 O C W1 R G TC TO ACC2 ACC1 Y1 O DH C W2 W1 R G DS W2 FOR SINGLE STAGE OPERATION INSTALL A JUMPER BETWEEN Y1 TO Y2 ON THE OUTDOOR UNIT TERMINAL STRIP Figure 9 C...

Page 17: ...If the intended capacity for the application is 3 or 5 Ton skip this section The units are field convertible to 2 Ton or 4 Ton to efficiently perform for the required application If the intended capa...

Page 18: ...itiate the Charge Mode A heating blower demand must also be provided to initiate high speed blower operation on the indoor unit The compressor and outdoor fan motor will begin to ramp up and reach 100...

Page 19: ...ooling indoor blower operation In single stage thermostat applications a jumper must be installed between Y1 and Y2 on the NS18HMA outdoor control The compressor will be controlled in the variable cap...

Page 20: ...late to list the actual field charge Table 11 Refrigerant Charge Adjustment Liquid Line Set Diameter Oz Per 5 ft adjust from 15 ft line set 3 8 in 3 oz per 5 ft or 0 6 oz per 1 ft If line length is gr...

Page 21: ...testing is completed replace service port cap Tighten finger tight then an additional 1 6 turn To Open Liquid or Suction Line Service Valve 1 Remove stem cap with an adjustable wrench 2 Use service wr...

Page 22: ...in mild detergent and rinsing with cold water Allow filter to dry before reinstalling Replace filters with the arrows pointing in the direction of airflow Dirty filters are the most common cause of p...

Page 23: ...heat pump to automatically switch from heating mode to cooling mode to maintain predetermined comfort settings Many heat pump thermostats are also equipped with an emergency heat mode which locks out...

Page 24: ...Page 24 of 25 508133G01 31 5000715 Issue 2140 Figure 15 Wiring Diagram...

Page 25: ...____________ Actual Amps ______ Rated Volts _______ Actual Volts ________ Condenser Fan Full Load Amps _________ Actual Amps ______ Cooling Mode Suction Pressure ____________________ Liquid Pressure _...

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