What is the difference between an LEV and an EEV they are both electronic expansion valves aren't they?
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What is the difference between an LEV and an EEV they are both electronic expansion valves aren't they?
LEV = liniear expansion valve
EEV = electronic expansion valve
An eev has a curved opening/closing caracter
an lev, as it's also named, has a linear one.
Perhaps this, quickly made, drawing will help explain it more!
Sanderh, I wasn't aware that an LEV excisted.
I saw it in watervalves but never in an expansion valve.
Can someone give me a practical example of the two?
What's the benefit of an LEV instead of and EEV?
Most VRV/ VRF systems use LEV valves at indoor units for refrrigerant flow through indoor unit coil.
The valve has a minature electric motor which turns a set amount each time a low voltage d/c pulse is is sent from the control circuit board to the LEV valve motor coils.The motor is connected to the needle valve by a number of gears like a minature gear box.
Typically these are made by in Japan by specialist manufacturer call Fujioki. Mitsubishi, Diakin & others all use this manufacturer for supply of LEV valves.
Anyway the indoor unit is constantly monitoring the refrigerant temperature at inlet & outlet of coil & calculating a type of super heat ratio in cooling mode & sub cool ratio in heating mode. The indoor unit is programed for a target super heat or subcool & so the indoor unit will ramp open or ramp closed the valve to achieve the target SH or SC.
Typically the valve will gradually ramp more & more open until the target is reached & will then slowly ramp down untill it needs to open again because it is not reaching target SH or SC.
This type LEV valve has 40 pulse shut possition & 2000 pulse fully open possition. The total open to shut dimension for the needle is about 2mm.
So when the indoor circuit board sends a command of one low voltage pulse to the LEV valve the needle changes possition by one thousanths of one millimeter.
Thats one reason why VRV/VRF systems are so good on COP energy efficency,,, very clever elecronic control & very exact refrigerant volume flow control at LEV valve.
The largest benefit of a LEV compared to an eev is that it's linear and doesn't, or at least not one noticeable deviation from input % to valve position. This makes control a lot easier!
Thanks for the explanation guys...really helpful:)
so is what your saying, an lev is more of a step motor type valve and an eev is an open close type arrangement?
IIRC, EEVs use "voice coil" or piezoelectric devices to replace the diaphragm as opposed to a motor. The "voice coil" requires special control to work correctly (force, not position, is proportional to current). I think piezoelectric EEVs are fairly linear but I'm not sure.