COMPONENTS TESTING (Continued)

EQ08 SYSTEM CONTROL SWITCH - TEST

“EQ08” SYSTEM CONTROL SWITCH – TEST

Turn knob to phase of switch to be tested. There must be continuity as follows:

1.“Fan Only” Position – between terminals “MS” and “H”

2.“Hi Cool” Position – between terminals “L1” and “C” and “MS” and “H”

3.“Low Cool” Position – between terminals “L1” and “C” and “MS” and “LO”

4.“Low Heat” Position – between terminals “L2” and “2” and “MS” and “LO”

5.“Hi Heat” Position – between terminals “L2” and “2” and “MS” and “H”

 

 

 

L1

 

 

 

 

 

 

 

 

 

System Control Switch

 

 

 

 

 

(EQ Models)

B1

 

 

 

 

MS

L2

 

 

H

C

 

 

LO

2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

THERMOSTAT (“EQ08” Models) (See Figure 17)

This thermostat is single pole-double throw, cross ambient with a range of 60° to 92°F and a differential of ±2°F. Terminal “2” is common.

Thermostat

(EQ Model)

WARNING

ELECTRIC SHOCK HAZARD

Disconnect power to the unit before servicing. Failure to follow this warning could result in serious injury or death.

TEST:

1.Remove leads from thermostat.

2.Turn thermostat knob clockwise to its coldest position.

3.Test for continuity between the two terminals. Contacts should be closed.

4.Turn thermostat knob counterclockwise to its warmest position.

5.Test for continuity - contacts should be open.

NOTE: The thermostat must be within the temperature range listed to open and close.

To maintain the comfort level desired, a cross ambient type thermostat is used. The thermostat has a range from 60° ±2°F to 92° ±3°F. The thermostat bulb is positioned in front of the evaporator coil to sense the return air temperature. Thermostat malfunction or erratic operation is covered in the troubleshooting section of this manual.

TEST:

Cooling/Heating Models: Remove wires from thermostat and check continuity between terminal “2” (common) and “3” for cooling. Check between terminals “2” (common) and “1” for heating. Also check that contacts in thermostat open after placing in either position. NOTE: Temperature must be within range listed to check thermostat. Refer to the troubleshooting section in this manual for additional information on thermostat testing.

THERMOSTAT ADJUSTMENT

No attempt should be made to adjust thermostat. Due to the sensitivity of the internal mechanism and the sophisticated equipment required to check the calibration, it is suggested that the thermostat be replaced rather than calibrated. Thermostat bulb must be straight to insure proper performance.

Thermostat

THERMOSTAT BULB LOCATION

The position of the bulb is important in order for the thermostat to function properly. The bulb of the thermostat should be located approximately 45° to a maximum of 60° from horizontal. Also, do not allow the thermostat bulb to touch the evaporator coil. (See Figures 17 and 18)

Thermostat Bulb Location

(EQ Model)

Thermostat sensor holder 020 to be positioned between the 4th and 5th and 6th and 7th rows of tubes from the bottom of the coil at dimension shown

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Friedrich R-410A service manual EQ08 System Control Switch Test, Thermostat Adjustment, Thermostat Bulb Location
Page 14 Page 16

R-410A specifications

Friedrich R-410A is an advanced refrigerant widely used in HVAC (Heating, Ventilation, and Air Conditioning) systems, known for its high efficiency and environmental friendliness. As a hydrofluorocarbon (HFC) blend, R-410A has become the preferred alternative to R-22, which is being phased out due to its ozone-depleting potential. One of the main features of R-410A is its high latent heat of vaporization, which allows for efficient heat transfer and improved cooling performance in air conditioning units.

Technologically, R-410A operates at higher pressures than older refrigerants, meaning systems designed for R-410A need to be built with more robust components to safely handle these pressures. This results in a more compact system design that offers enhanced performance and reliability. The dual-component nature of R-410A—composed of difluoromethane (R-32) and pentafluoroethane (R-125)—provides an optimal balance of thermodynamic properties, leading to superior energy efficiency, especially in variable speed applications.

In terms of characteristics, R-410A has a higher cooling capacity, which enables HVAC systems to effectively cool larger spaces or run more efficiently when cooling smaller areas. The refrigerant is non-toxic and non-flammable, which enhances safety during its use. In addition, R-410A has a lower global warming potential relative to other refrigerants, making it a more environmentally responsible choice for modern cooling systems.

Moreover, R-410A systems typically require less refrigerant charge due to their efficiency, contributing to reduced greenhouse gas emissions. The adoption of R-410A aligns with regulatory trends aimed at minimizing the environmental impact of refrigerants in cooling applications.

Overall, the Friedrich R-410A refrigerant embodies a combination of technology and environmental stewardship, making it a cornerstone of contemporary HVAC design. Its ability to provide effective and energy-efficient cooling solutions while being compliant with modern environmental regulations positions R-410A as the refrigerant of choice for engineers and installers focused on sustainability and performance in air conditioning systems.
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