System and apparatus for refrigeration and heating

A three pipe cooling and heating apparatus for cooling a room comprising:

• a) a refrigeration machine comprising a condenser and an evaporator,
• b) a cold supply pipe leading from the evaporator and a combination hot supply/return pipe leading from the condenser,
• c) a fan coil unit comprising a coil and, a fan coil pump for circulating fluid through the fan coil unit, the fan for blowing room air across the coil, the fan coil unit operable between a cooling mode wherein a cold fluid is circulated through the coil by the fan coil pump and a heating mode wherein hot fluid is circulated through the coil by the fan coil pump,
• d) the cold supply pipe and hot supply return pipe leading to a two position three-way valve,
• e) a modulating three-way mixing valve located at a downstream location from the two position three-way valve, a fan coil thermostat in a controlling type relationship with the modulating three-way mixing valve,
• f) the modulating valve for directing the flow of the fluid pumped by the fan coil pump so that all, none, or a percentage of the fluid being pumped by the fan coil pump is recirculated the fan coil unit,
• g) a total pressure drop sensor positioned to detect a total pressure drop across the coil an wherein if the total pressure drop reaches about one half and inch of mercury hot fluid is circulated through the coil to melt accumulated ice.

A method of refrigerating and cooling comprising the following acts:

• a) providing a cold supply pipe for delivering cold fluid, providing a cold return pipe for returning cold fluid, and providing a hot supply/return pipe for delivering and returning hot fluid,
• b) providing an upstream two position three-way valve connected to the cold supply pipe and to the hot supply/return pipe, and locating a modulating three-way mixing valve located downstream of the upstream two position three-way valve,
• c) positioning a fan coil unit pump downstream of the modulating three-way mixing valve,
• d) providing a fan coil unit comprising a coil and a fan and blowing air through the coil with the fan the fan coil unit pump for pumping fluid through the coil,
• e) providing a fan coil unit pump located downstream of the modulating three-way mixing valve wherein the modulating three-way mixing valve is for allowing none, a portion of, or all of the fluid in the coil to be recirculated through the coil by the fan coil unit pump,
• f) positioning a downstream two position three-way valve downstream of the modulating three-way mixing valve for returning fluid to the cold return pipe or the hot supply/return pipe,
• g) providing a means for computerized control,
• h) providing a total air pressure drop sensor for detecting a pressure differential across the coil and for sensing a predetermined maximum pressure differential across the coil, the total air pressure sensor in electronic communication with the means for computerized control.