txv fitted backwards

[knighty]

fitted 3x searl mke95 evaporators with danfoss te5 expansion valves

2 of the evaps were used

looking at the arrow on the side of the txv's they were obviously mounted backwards - really confused me how anyone could do that

so I mounted them the right way around

access is a real pain so it took a while

gassed the first system up... refrigerant wouldn't flow around system

diagnosed no flow through the txv

wow I thought.... they must have been the right way to start with, why the hell do they have an arrow on that points opposite to the direction of flow through them???

removed all 3, mounted them with the arrow backwards

finished and still no flow! :-(


dismantled the first txv.... it had about 6 fiber washes in for the orifice, pushing it away from the power head, removed those, set the system running

system running well, pressures look right... BUT compressors are icing up

I'd have thought suction pressure would be high if flowing enough refrigerant to push liquid back to comp?

suction pressure is under 30psi



I appreciate the extra fiber washers were probably the cause of the problems (no idea why they were fitted) and I'll go and turn the txv's around (access is a total pain in the arse)

but.... interested to hear peoples opinions?

I thought systems would be a total non runner with a backwards txv?

[seanf]

TEV backwards do work, maybe not as well. Internally equalising might not work so well.

The liquid might be causing the TEV to close and open instead of regulating giving an overall lower pressure.

[mbc]

As the thermostatic expansion valve regulates the rate at which liquid refrigerant flows into the evaporator,
it maintains a proper supply of refrigerant by matching this flow rate against how quickly the refrigerant evaporates (boils off) in the evaporator coil.

To do this, the TXV responds to two variables:
the temperature of the refrigerant vapor as it leaves the evaporator (P1)

and the pressure in the evaporator itself (P2).

It does this by using a movable valve pin against the spring pressure (P3)

to precisely control the flow of liquid refrigerant into the evaporator (P4):

TXV Pressure Balance Equation

P1+P4 = P2+P3

P1 = Bulb Pressure (Opening Force)

P2 = Evaporator Pressure (Closing Force)

P3 = Superheat Spring Pressure (Closing Force)

P4 = Liquid Pressure (Opening Force)

[mbc]

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