RIL+212+3 Phase+2nd+Report

8/9/2019 RIL+212+3 Phase+2nd+Report

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LAB REPORT3-PHASE COMPRESSOR WITH AUTOMATIC

PUMP DOWN

J O A Q U I N V E L E Z I D : 2 1 7 4 6 0

S U B M I T T E D O N 4 / 1 4 / 0 9

S U B M I T T E D T O :

M R . P E R E Z

R I L / 2 1 2



3-PHASE COMPRESSOR WITH AUTOMATIC

PUMP DOWNELECTRICAL SEQUENCE OF OPERATION

On a call for cooling, a rise in temperature will cause the thermostat switch

to close. 24 volts of power is now being sent simultaneously to the

Evaporator fan relay(EFR) coil and Line solenoid Valve(LLSV) coil, when

the EFR is energized this will cause N.O EFR contact to close and to send

120 volts of power to energize the Evaporator Fan motor(EFM). As the

N.C Liquid Line solenoid Valve (LLSV) coil is energized it will open and

allows high pressure, low temperature liquid refrigerant to flow through the

valve to the metering device and flow into the evaporator. The liquid

entering the evaporator will be under a reduced pressure and begin tovaporize. This will create a higher pressure on the low side of the system

(Since vapor occupies more space than liquid). When the pressure rises

above a pre- determined cut-in setting on the low- pressure controller, the

low pressure control switch will close and power will go through the N. C

switches in the following order: HPC, 3 CC overloads in series, a N.C Lock

out relay switch and then energize the CC coil. When the interlocked CC

coil is energized, the N.O CC switches will close and the N.C CC switch

controlling the crankcase heater (CCH) will open and de-energize the CCH.

120 volts of power will be sent to the compressor motor (CM) and the

condenser fan motor (CFM) simultaneously. The Condenser Fan and

Compressor Motor are now ON. The refrigeration cycle has now begun.

When the thermostat detects the set point temperature has reached the

desired set- point temperature the thermostat will open and de-energizes the

liquid line solenoid valve and also EFR coil will de-energize and the closed

EFR contact will return to its N.O position and will de-energized the EFM.

The EFM is now off. The Liquid Line solenoid Valve is now in its N.C

position. However the compressor will still be working pumping refrigerant

vapor from the evaporator to the condenser. As the pressure on the high side

gets higher due to the closure of the LLSV the pressure on the low side of the system will begin to drop. When the pressure drops at the cut- out setting

of the Low Pressure Control the LPC will open and de-energize the CC coil

and opening the CC contacts to the compressor and Condenser fan motor

shut the compressor motor off. The CC contacts to the CCH will close and

will energized the CCH which will remain energized at all times during the

compressor OFF cycle.



2

TROUBLESHOOTING PROBLEM DIRTY EVAPORATOR COIL

Customer complaint?

SYSTEM TURNS ON AND OFF SUDDENLY OR DOESN·T TURNON FOR NORMAL COOLING OPERATION.

PROMBLEM: Upon energization of the liquid line solenoid valve by thethermostat the liquid in the condenser will go from the TXV to the evaporator.

Whatever liquid enters into the evaporator will not be able to absorb the heat inorder to make the refrigerant change state into a vapor. Vapor occupies more

space than liquid. The pressure will not raise to a high enough level to close theLPC to energize the CC coil. If by some chance the LPC is able to close the CCcoil will be energized will turn the compressor ON. Since in this circuit the

LPC is used as a control device, the refrigerant will be circulated through thesystem but since the evaporator is dirty the refrigerant will be mostly liquid inthe evaporator thus lowering the pressure on the low side. The pressure will

eventually get to low that the compressor will shut off on low pressure.

Step by step Trouble-shooting.:

1-Determined what refrigerant the system runs on.

2-Determined the Cut-in and Cut-out of the Low Pressure Control to know when the Compressor is supposed to turn on and off.

3-Read the FLA and RLA values of the system compressor. I needed todetermine first if the compressor was drawing the correct FLA that would

apply on a properly charged system.

4-Installed an ammeter on one of the compressor windings. To observehow much amperage the compressor was drawing when pumping refrigerant

throughout the system.

5-Installed my manifold gauges on the low side and high side of the system.

6- Read the pressures on the high side and low side of the system when thesystem was OFF.



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15- Since what I was observing with all of the data I acquired was the

effect/s but not the cause/s. Effects always follow a cause. Causes of high

condensing temperatures include dirty condenser coils, restricted condenser

airflow (fan out), air in the system, and an overcharge of refrigerant, and/or

high ambient temperature. Causes of low suction pressure include iced

evaporator coils, restricted evaporator airflow (fan out), an undercharge of

refrigerant, dirty evaporator coil, end of the running cycle, thermostat or

LPC set wrong, and/or low evaporator heat load.

CONCLUSION

By an analysis of all the data I acquired I could determine a number of

causes to the problem. And by process of elimination I knew that all the

components required for a normal cooling effect were in working order. Ieliminated the possibilities of restricted air flow (both FANS WORKED).

The compressor working near of more its FLA indicated that the system was

properly charged but that the reason for the higher pressures was due to

other circumstances. It would eventually lead me to investigate the

evaporator and TXV for possible Blockage or a loose thermal sensing bulb.But I would open the panels that are covering the evaporator coils to see

that indeed the Evaporator was in Dirty condition which will greatly reduced

the refrigerant capacity and will always cause the pressure in the low side of

the system to go into a low pressure (because of more liquid than gas in the

evaporator). The dirty surface is acting like an insulator and preventing therefrigerant from changing state into a gas.

RIL+212+3 Phase+2nd+Report

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