About TEV

[wendecai]

Can anyone tell me what is the difference between TEV with MOP and TEV without MOP? What is MOP?Also i've install a new TEV onto the coldroom and the hissing sound was at the liquid line?I've check the pressure on low and high side.the charging looks fine.One strange thing was,only one pipe at the evaporator is icing up and it melts after few minutes.Is it that the orifice is too big which oversize?

Pls Help??


Thank you

Jeff

[Brian_UK]

Hi Jeff, have a read of this Sporlan document on TEVs, it details the MOP function.

http://www.sporlanonline.com/10-9.pdf

If you more or other stuff then make your choice..
http://www.sporlanonline.com/literature.shtml

[cool runings]

Can anyone tell me what is the difference between TEV with MOP and TEV without MOP? What is MOP?Also i've install a new TEV onto the coldroom and the hissing sound was at the liquid line?I've check the pressure on low and high side.the charging looks fine.One strange thing was,only one pipe at the evaporator is icing up and it melts after few minutes.Is it that the orifice is too big which oversize?

Pls Help??


Thank you

Jeff

TEV Normal Thermostatic Expansion Valve.

MOP Maximum Operating Pressure It will deliver refrigerant to a maximum pressure.

The hissing you hear is refrigerant passing through the valve itself.

Coolrunnings

It is fundimentals of refrigeration.
Did you change the valve like for like?
Did you install an orifice and was it the same size as the one you took out?
Did you pressure test and vac the system dry?

Coolrunnings
.

[R. skiffington]

It's simple really, an expansion valve has a charge of refrigerant in the bulb and carpillary, as the temp of the suction gas increases/decreases it raises/decreases the temp of the charge in the bulb which increases/decreases the pressure applied to the tx valve diaphram. In an MOP valve the charge of refigerant in the bulb is minimised so it can only increase in pressure to a certain point, once at that point even if more heat is applied it will not increase pressure on the valve diaphram so can not open the valve further. An example of where you would use an MOP valve would be a freezer with no CPR valve (crankcase pressure regulating valve). On a hot start or after a defrost where evaporating temperatures can be far too high for a low temp compressor the MOP valve will limit sution pressure protecting the compressor (but will make for a slow pull down). Hope this helps.