correct evaporator coil piping

[setrad7791]

Hi everyone! Just have a inquiry as to the correct design of a static evaporator coil mounted in a 6-foot display case i.e butchers/deli style case. I have noticed recently that the tx-valve has been installed with the liquid entering the bottom of the coil and suction of the top.... In my opinion it should feed from the top of the coil so as to not log oil or flood with refrigerant causing erratic superheat? Am i missing something or is their a reason for this design?

[Bones74]

It's probably a after thought on the manufactures part on how to stuff the piping in there. Ever see a exact model number on a unit and a different configuration? It happens to often.:confused:

[taz24]

Hi everyone! Just have a inquiry as to the correct design of a static evaporator coil mounted in a 6-foot display case i.e butchers/deli style case. I have noticed recently that the tx-valve has been installed with the liquid entering the bottom of the coil and suction of the top.... In my opinion it should feed from the top of the coil so as to not log oil or flood with refrigerant causing erratic superheat? Am i missing something or is their a reason for this design?


With it being static they may have designed and positioned it that way to ensure all the liquid is boiled off before it gets to the suction line.

taz.

[Iceman Ian]

Are you talking about the bottom cold plate evaporator or the top mounted cross finned evaporator coil ???

If it is a cross finned coil, what is the coil cofiguration e.g. - Into bottom, return bend to top, return bend to bottom, etc ????

Feeding into the bottom of a coil allows extra liquid refrigerant to build up in the tubes increasing the refrigeration effect and efficiency, also allow excess refrigerant to boil off as it passes through the top of the evaporator coil (a bit more involved, but this simple explanation will do for now)

[Dan]

This has been a debated topic in the past. If you look at fan driven display cases, and vertical (taller than they are horizontal) evaporators such as you might see in the back wall of a dairy or meat case, they are piped top to bottom by the manufacturers that I am familiar with... the explanation being one that included insurance of oil return.

Oddly, the manufacturers have no compunction to pipe these bottom to top when gas defrost is used (reach-ins and meat cases). The explanation being that the defrost will sweep the oil out, if that becomes a problem.

Iceman's comment is noteworthy too. Bottom to top imitates a liquid overfeed system and probably has merit in the heat transfer efficiency of the evaporator. But I am sure somebody will have an argument that the turbulent flow of a top to bottom evaporator has efficiency gains as well without the added inefficiency of oil logging.

I think Hussmann had a series of gravity coil merchandisers that fed the serpentine coil beneath the pans first and then top fed the gravity coil with the bulb on the suction line leaving the bottom of the gravity coil. In this instance, you have it both ways:)