Pressure controls. How do they work and what do I look for?

[BBeerme]

How does an accumulator limit the short cycling?

We all have. That's the way automobile AC works. The compressor clutch engages at high pressure and disengages at low pressure with an accumulator limiting short cycling. The temperature knob controls how much reheat is added by the heater core downstream of the evaporator.

[Olivero]

Aaaaand. Im lost again.

I think I need to work more with the LPC to really understand them, only did one so far but it seems to have been successful so one step closer to knowing them.

I don't think I have any in my building that don't have thermostats.

Funny thing is I originally started out in this to fix appliance fridges as its so time consuming to have someone else do it but have had more problems with my walk ins than the appliance fridges in the building.

Kind of happy it went that way though, learned a lot more from these walk ins than I think I ever would with appliances.

[TechmanTerry]

Don't forget Dick Wirz.

[Snapperhead]

How does an accumulator limit the short cycling?

It doesnt really limit short cycling very well , but thats the way American vehicles were set up for many years. Fortunately you can short cycle those compressors all day long , they dont care.

The Imports use a klixon type switch on the Evap

[Snapperhead]

Aaaaand. Im lost again.

I think I need to work more with the LPC to really understand them, only did one so far but it seems to have been successful so one step closer to knowing them.

I don't think I have any in my building that don't have thermostats.

Funny thing is I originally started out in this to fix appliance fridges as its so time consuming to have someone else do it but have had more problems with my walk ins than the appliance fridges in the building.

Kind of happy it went that way though, learned a lot more from these walk ins than I think I ever would with appliances.

Did you understand Russel in post 27 ?

You probly wont come across many LPC ( low pressure control ) controlled systems , they are rare ( no thermostat used ) the compressor is cycled using suction pressure ( I hate those setups )

But you will see many "fan controls" run by HPS ( high pressure switch ) and those you need to adjust the Differential

Largely you will see LPC used to turn on/off the compressor , which has a Diff to set , which is what you have , BUT , its only doing so because the THERMOSTAT has closed the LIQUID LINE SOLENOID , which slams the liquid line shut , which makes the condenser PUMP DOWN , which means the compressor is sucking all of the refrigerant out of the Evaporator via the suction line and forcing it into the condenser coil ,and receiver. As its sucking, the LPC is monitoring the suction pressure , and when it nears 15 psi it will shut the compressor off.

This is why you need to turn the LPC dial to "Cut In" at 40 , and turn the" Diff "at 25 , although you cannot actually " SEE" the CUT OUT "number" , but it will actually cut out the compressor at 15 psi

Think of Diff as " MINUS "

So 40 minus 25 = 15

Now , when the thermostat opens the Liquid Valve , the liquid will rush out of the Receiver , flow into the evap , then into the suction line , where the LPC is monitoring it , and when it rises to 40 it will cut the unit back on.

Refrigeration for dummies .... youre welcome

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