A refrigeration system including an evaporator defining an evaporator envelope and positionable to condition an airflow, the evaporator including an airflow inlet, an airflow outlet, and one or more refrigerant coils. The refrigeration system also includes a pressure sensor that is positioned to detect an outlet air pressure at or adjacent the outlet, and positioned to detect one or both of an ambient air pressure and an inlet air pressure and to generate a signal indicative of the corresponding air pressure. A control system in operative communication with the pressure sensor to determine a pressure differential based on the signal indicative of the outlet air pressure and the signal indicative of the ambient air pressure or the inlet air pressure, the control system configured to selectively initiate a demand defrost of the evaporator based on the determined pressure differential.

A heating, ventilation, and air conditioning (HVAC) system and controller therefor to operate with thermal energy reservoirs are provided to set a four-way valve to route a refrigerant through a refrigerant circuit in a first direction when the HVAC system is set to a cooling mode or in a second direction, opposite to the first direction, when the HVAC system is set to a heating mode; and set bypass valves in the refrigerant circuit based on a temperature of a temperature holding material in a thermal energy reservoir and which of the heating mode and the cooling mode the four-way valve is set to, wherein the bypass valves route the refrigerant through the thermal energy reservoir to transfer thermal energy between the refrigerant and the temperature holding material.

A heat pump system includes a refrigerant circuit in which a compressor, a refrigerant flow path included in a heat medium heat exchanger, an expansion valve, and a heat source side heat exchanger are connected, the heat medium heat exchanger including the refrigerant flow path and a heat medium flow path; a heat medium feed path connected to the heat medium flow path included in the heat medium heat exchanger; an indoor unit connected to the heat medium feed path and configured to condition air inside a room; a room temperature sensor configured to detect an indoor temperature in the room; a heat medium temperature sensor configured to detect a temperature of a heat medium that flows into the indoor unit; and a controller configured to control the refrigerant circuit or the indoor unit by using a set temperature in the room.

A heat pump water heater can include a refrigerant circuit, an evaporator coil in fluid communication with the refrigerant circuit, a fan configured to move air across the evaporator coil, one or more temperature sensors, a heating element located proximate an air flow path between the fan and the evaporator, and a controller. The controller can be configured to receive temperature data from the one or more temperature sensors and, in response to the temperature data, output instructions for the fan to move air across the heating element to the evaporator coil.

A refrigeration system includes a dedicated defrost-mode compressor that delivers high pressure, high temperature refrigerant to one or more evaporators to defrost the evaporators.

A snow and ice melt system having one or more zones, each including one or more heaters, and having one or more controllers configured to use a power output of each heater and an average temperature of each zone to determine operational control of each heater to achieve a specified result. Hydronic or resistive heaters could be used. The controllers may be configured to use a system temperature response over time to determine if a phase change of the snow or ice is occurring. The phase change might indicate that snow or ice is present on a zone and is melting. Use of a first derivative of the system temperature response over time might determine a percentage of a zone covered by snow or ice. Use of a second derivative of the system temperature response over time might determine whether melting is complete.

Ice mitigation for bridge cables is provided by a system having a plurality of heaters on one or more bridge cables, extending parallel to a longitudinal axis thereof, arranged in a plurality of heater sections, and configured to heat an outer surface of the bridge cables, and a control system including one or more controllers configured to individually activate and regulate heating output of the heater sections to prevent snow or ice from falling from the bridge cables. The heater sections can be arranged radially, about a circumference of the bridge cables, and/or axially, end to end along a length of the bridge cables, so that power can be individually directed to the heater sections to account for differing heating requirements at different radial and/or axial aspects of the bridge cables.

A heat pump for a vehicle is provided in which the heat pump includes a compressor, an inner heat exchanger, an outer heat exchanger, a first expansion unit, a second expansion unit, an evaporator, an accumulator, a third heat exchanger, a first directional control valve, a second directional control valve, and a dehumidification line, and performs cooling, heating, defrosting, and dehumidifying operations according to the flow of a refrigerant.

A hot gas bypass circuit that connects a discharge side of the compressor and a portion between the heat source side heat exchanger and the expansion valve, an on-off valve that opens and closes a channel of the hot gas bypass circuit, and a control device performing control to select one of hot gas bypass defrosting and reverse cycle defrosting according to a frosting amount on the heat source side heat exchanger and perform defrosting. The control device controls to open the on-off valve of the hot gas bypass circuit such that a part of a refrigerant discharged from the compressor is supplied to the heat source side heat exchanger via the hot gas bypass circuit and, the control device switches switch the four-way valve such that the refrigerant discharged from the compressor is supplied to the heat source side heat exchanger after passing through the four-way valve.

A dual redundant cooling system for a container is provided. The dual redundant cooling system includes a first cooling unit and a second cooling unit. The first cooling unit is positioned in a first cabinet attached to the container. The first cooling unit includes a first controller operating a first cooling loop to cool an interior of the container. The second cooling unit is positioned in a second cabinet attached to the container and adjacent the first cabinet. The second cooling unit includes a second controller operating a second cooling loop to cool the interior of the container. The first cooling unit and the first cooling loop are separate from the second cooling unit and the second cooling loop. The first controller and the second controller communicate a switch signal between each other so that either the first cooling unit is a primary cooling unit operating the first cooling loop or the second cooling unit is the primary cooling unit operating the second cooling loop. The switch signal switching the primary cooling unit.