UNIT OPERATION WITH A WALL-STAT

Front Panel Display Operation in Wall-Stat Mode

The indoor ambient temperature sensor is disabled. All buttons are disabled with the following exception: A. Maintenance commands.

B. The user menu for Freeze protection (Display/Enter button for Kuhl+ only units). C. First Button push to illuminate the back light (display will dim).

Maintenance features are operational. This includes the Check Filter, Lock Panel, M3, M4, M5, and the Service wrench icon. Under T-stat operation, as a default, the selected operating Mode (Cool, Heat or Fan) will not show on the front panel. The Service ICON ( ) is displayed if a malfunction is detected.

Cool/Heat/Fan modes and Fan speed operations are controlled by the remote wall thermostat.

The fan speeds can be Low or Max for 4 speed units and Low or High for 3 speed units. (T-stat selected must have 2 speed capabilities)

Thermostat terminals requirements:

Must be single stage heat/cool. For cooling only units: C, R, G, Y.

For cooling with electric heat units: C, R, G, Y, W.

For heat pump units: C, R, G, Y, W, B.

(See page 68 for RT5 T-Stat wiring diagrams)

During Heat Mode:

The B terminal must be continuously energized. The W terminal from the T-Stat must have 24 V AC output to call for heat. The control board decides on whether to turn on the Heat Pump Heat (compressor) or Electric Resistance Heat. The Y terminal should not have 24 VAC output during Heat Mode.

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Friedrich R-410A service manual Unit Operation with a WALL-STAT, During Heat Mode
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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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