# Liquid Line Solenoid - Pump Down



## WyrTwister (Jul 19, 2013)

Liquid Line Solenoid - Pump Down 


Through out the years , I have come into contact with commercial split systems with a Liquid Line Solenoid .

The controls activated the solenoid , when the thermostat ( or Building Automation System ) was satisfied .

The compressor started to pump down and , best I remember , the compressor shut down on low suction pressure ?

That is the reason this method is used , rather than simply have the ASA turn off the compressor contactor ?

Thanks ,
Wyr
God bless


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## Inner10 (Mar 12, 2009)

Never seen one that uses a solenoid on the line instead of a contactor...but I have seen shutoff solenoids on large systems to prevent the liquid from all pooling where it would be sucked back once the compressor starts back up.


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## WyrTwister (Jul 19, 2013)

Inner10 said:


> Never seen one that uses a solenoid on the line instead of a contactor...but I have seen shutoff solenoids on large systems to prevent the liquid from all pooling where it would be sucked back once the compressor starts back up.



I think the first one I ran into was a couple of Liebert units in a small Telco building ?

They had remote condenser coils / fans , outside the building & the compressor was in the bottom of the AHU / blower assembly . This was , maybe 25 years ago . 

Had a pair of # 14 wires going between the inside / outside units , to pull in the contactor feeding the fans .

Seems the LL solenoid was inside the bottom compartment of the AHU ?

These were cool only & the tstat activated the solenoid ?

As it turned out , these were cool only , which ended up being a bad idea . First cold spell & we ended up going back and installing a couple of hanging electric unit heaters .

The new Telco electronics did not put out as much as the old equipment did . Not enough heat to keep the building warm .

Since then , I have run into the LL solenoids , from time to time . Not always on Liebert systems . Some times on medium size condensers serving AHU's .

God bless
Wyr


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## HVAC1000 (Feb 4, 2013)

WyrTwister said:


> I think the first one I ran into was a couple of Liebert units in a small Telco building ?
> 
> They had remote condenser coils / fans , outside the building & the compressor was in the bottom of the AHU / blower assembly . This was , maybe 25 years ago .
> 
> ...


They are very common on commercial refrigerators because as was said before, they prevent the liquid refrigerant from pooling and shooting up to the compressor and slugging it. 

I have seen that heat load problem before. Even in large commercial buildings where they change all the light bulbs to LEDs or High efficiency bulbs in the spring and the following winter they can't keep the building warm. All those bulbs add up and create a lot of BTUs


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## beenthere (Mar 5, 2009)

Fairly common on large commercial split systems. Protects the compressor.


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