Not all walkins are pump down

[Bombboy90]

CCH is still cheap insurance?

Good point! So is a pump down imo.

[pecmsg]

I was taught in school years ago one major benefit to walk in cooler pump down was to prevent refrigerant leakage during the off cycle if the evap has a leak from say, tomato or onion acid eating at the coil. I know most coils are coated but leaks find a way...

Among the other points listed, I never really thought of it to prevent liquid slugging. Makes sense really, and also bbeerme makes a point, solenoid is off no liquid in the compressor, no reason for a CCH thus saving $

CCH is still cheap insurance?

The CCH is only good during the off cycle. While running the motor windings keep the oil warm.

[ammoniadog]

CCH is still cheap insurance?

The CCH is only good during the off cycle. While running the motor windings keep the oil warm.

Yeah, when its -20°F that CCH is a good thing to have

[BobFrost]

Why is that?

Installers don't have the knowledge, or perhaps they don't want to bother with pump-down set up.

[rickl]

So all yÂ’all did yo homework and found out a properly operating system without a pump down will not cause a flooded start, no slugging. In fact the tev will close on the off cycle. The tev will not feed in the off cycle! All the liquid refrigerant in the Evap will evaporate. As to migration in the cold parts of the world the crankcase heater takes care of that..
And as to those 100 foot suction run at -20 ambient refer to the basis refrigerant textbooks and the pt chart how the vapor condenses to liquid. Tev are the most mis-understood component of the refrigeration system!
FYI in the 45 years I have been working, the only time I found a busted crank was due to a defecting tev flooding. We always breakdown those semi hermetic for a Look see and a few hermetic compressors as well, just for fun.

[pecmsg]

So all yÂ’all did yo homework and found out a properly operating system without a pump down will not cause a flooded start, no slugging. In fact the tev will close on the off cycle. The tev will not feed in the off cycle! All the liquid refrigerant in the Evap will evaporate. As to migration in the cold parts of the world the crankcase heater takes care of that..
And as to those 100 foot suction run at -20 ambient refer to the basis refrigerant textbooks and the pt chart how the vapor condenses to liquid. Tev are the most mis-understood component of the refrigeration system!
FYI in the 45 years I have been working, the only time I found a busted crank was due to a defecting tev flooding. We always breakdown those semi hermetic for a Look see and a few hermetic compressors as well, just for fun.

If that’s how you feel fine!

[WT70]

FYI in the 45 years I have been working, the only time I found a busted crank was due to a defecting tev flooding. We always breakdown those semi hermetic for a Look see and a few hermetic compressors as well, just for fun.

We do the same a lot of times, when we have time from all the service calls to tear it down.

One busted crank in 45 years? Go buy yourself a lottery ticket.


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[GenesisRefrig]

Typo ?

Bad grammar. I meant that migration of refrigerant is not possible if you’re pumped down.

[WT70]

Directly from a Sporlan rep....





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[BBeerme]

Very rare to see a busted crank. I've probably never seen one.

Most likely scenario is the clearance at either end of the connecting rod, piston/rings, or valves.

[WT70]

Very rare to see a busted crank. I've probably never seen one.

Most likely scenario is the clearance at either end of the connecting rod, piston/rings, or valves.

Oil slugging on racks will tear a compressor up.

Wait. Ha. Pistons and rods, I guess I’ve only had a crank bust when it hit the rod that came off when oil went thru the heads.


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[BBeerme]

Yeah, cranks do get severely damaged, but bust? Like in two pieces? VERY rare.

[shellkamp]

Directly from a Sporlan rep....





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Are you confusing evaporator pressure with inlet (liquid line) pressure??

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[BBeerme]

Have to get Remanworld to weigh in on this one, he's the authority here. Not sure I got his username correct.

Yeah, cranks do get severely damaged, but bust? Like in two pieces? VERY rare.

[WT70]

Are you confusing evaporator pressure with inlet (liquid line) pressure??

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Liquid pressure goes down in off cycle, suction would rise.


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[shellkamp]

Liquid pressure goes down in off cycle, suction would rise.


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What are you trying to say???

To be clear, all I said was that on non-balanced port valves, the inlet (liquid pressure) acts as an opening force on the valve. The difference in pressure between the liquid line and the outlet of the TXV will aggravate this condition.



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[WT70]

What are you trying to say???

To be clear, all I said was that on non-balanced port valves, the inlet (liquid pressure) acts as an opening force on the valve. The difference in pressure between the liquid line and the outlet of the TXV will aggravate this condition.



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Rickl stated “valve closes in off cycle”, which a lot said this doesn’t happen. So I wanted a true answer myself.

I honestly thought the power element would overcome the spring, but it doesn’t.

According to Sporlan Rep, the valve closes. I asked him because what better way to get the proper answer than ask the people that make the valves.

The liquid pressure actually does push down on the metering needle, during operation it helps keep movement of the TEV smooth.

Internal EQ valves uses the pressure on the outlet of the TEV for the pressure under the power element through an internal port. External uses the pressure from the suction line on the outlet of the evaporator.

In off cycle, suction pressure rises, pushes against the power element, along with the spring to overcome power element force, closing the valve.

That’s not to say it doesn’t fully close until pressures equalize, and worn out valves may bleed by, but a TEV closes on off cycle.


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[pecmsg]

Correct but that can take several minutes while the valve is still beating refrigerant into the evaporator. That refrigerant condenses into a liquid
Depending on the operating conditions it could be a little or a lot

[WT70]

Correct but that can take several minutes while the valve is still beating refrigerant into the evaporator. That refrigerant condenses into a liquid
Depending on the operating conditions it could be a little or a lot

Exactly. But it does close. The time it takes to close throws most of us as we see the pressures equalize.

I’m still a proponent of pump down. But on smaller systems and cap tube systems how often do we see that except for True equipment I think.


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