What should the temperature of hot gas be to defrost?
It is generally accepted that the practical minimum hot gas temperature for effective defrosting is around 50F (a defrost regulator setting of 75 psig). Figure 2 illustrates how an increase in the hot gas temperature results in an increase in convective heat loss and reduction in defrost efficiency.
How long does it take for a refrigeration unit to defrost?
However, it is the observation of the author that most evaporators in industrial refrigeration facilities have hot gas defrost duration settings in excess of 30 minutes, that is, the period of time the hot gas solenoid is open.
How does a hot gas defrost work like a heat pump?
Hot gas defrost acts like a heat pump to “move” heat. A heat pump moves heat “uphill” by gathering energy at a low temperature level in the evaporator, compressing the evaporated refrigerant to a higher pressure, then releasing the energy at a higher temperature level during the condensing process.
Why does defrost efficiency decrease with heat loss?
This heating (and cooling) of the coil and drainpan metal is unavoidable and results in a reduction in the ideal maximum defrost efficiency. Defrost efficiency is also reduced when some of the defrost heat is lost to the room as heated air (convection) and radiation.
What happens if the defrost sensor does not blow?
If the defrost sensor fails to shut off the defrost heater, the fuse will blow in order to shut off the defrost heater. If the defrost sensor fuse blows, the defrost system will not work, and the refrigerator will not defrost. The defrost sensor fuse is not resettable—if the defrost sensor fuse blows, you must replace the defrost sensor.
What should the efficiency of a gas defrost be?
Cole further suggested that the maximum theoretical defrost efficiency was probably in the range of 60% to 70%. Defrost efficiency will be reduced as energy lost to the room during defrost increases.
How do you defrost a frozen gas nozzle?
The power to your gas pump should be off while attempting this gas nozzle defrost technique. Hold the nozzle with the spout pointing up, slowly pour gas line antifreeze down into the spout, and wait at least a couple of minutes.
What are the different types of gas defrosts?
There are two basic types of gas defrosts. Hot gas defrost is where superheated discharge gas is directed into the evaporator, and “Kool gas” is a trademarked name for a defrost that directs saturated vapor from the top of the receiver unto the evaporator. Each has advantages and disadvantages, but both work essentially the same way.
