Discharge Valve/Regulator Working Principle / Troubleshooting

!Perform any service if;
• Person who is going to work on the Compressor is CERTIFIED,
• All compressed air is discharged inside the Compressor,
• Compressor is completely isolated from the compressed air system.

!Some of the /d series Compressors are equipped with a solenoid valve and a regulator combination acting as a discharge valve in the Compressor. It is very important to understand how it works, as an improperly working discharge valve can be the reason for the many issues which are faced with the Compressor.

Discharge valve dumps the internal compressor air when;

• Compressor completely stops until no compressed air is left in the Compressor,
• When the Compressor air outlet pressure is above 7 PSI (0.5 bar) above the desired pressure (PSET) set by the user,
• When the Compressor element outlet temperature (shown on the compressor display in Centigrade) is below 158F (70C), solenoid valve discharges some air when compressor outlet pressure is 4 PSI above the the desired pressure (PSET) set by the user. This is called heating function. Heating function ensures that the Compressor will warm up enough to avoid water condensation in the oil sump.
  

*If the Compressor element temperature (shown on the Compressor display in C) below 158F (70C) and the air demand is not enough to keep the Compressor run under load to heat the Compressor internally, discharge valve will dump some air to maintain maximum flow to heat the compressor quickly to avoid condensation. Such discharge action on the solenoid valve may be a cycling action. That is completely normal and varies according to tank(s), tubing in the compressed air system and compressed air usage. Till compressor reaches to min required temperature, it will not count down the off load timer and will not stop.

When the Compressor builds or maintains pressure at the system and the Compressor pressure outlet is below 7 PSI (0.5 bar) above the desired pressure (PSET) set by the user, discharge valve is energized and does not discharge any air. Otherwise, any of the above conditions above, solenoid valve discharges air.

How to adjust regulator

If regulator is adjusted;
• at LOWER pressures than it should be or 0 bar on regulator gauge, the Compressor will go high pressure,
• at HIGHER pressure than it should be, adjusted excess noise will be heard during discharge.

• Loosen the regulator knob to adjust the pressure completely.
• Run the Compressor,
• Wait until the Compressor fills the tank and pressure reaches to the limit where solenoid valve opens and starts discharging air,
• Start tightening the regulator knob until pressure in the tank starts increasing,
• Loosen the knob by 1/4 turn ,
• Check if pressure in the tank is increasing or not,
• If pressure is increasing, gradually loosen the knob 1/4 turn more and check if pressure increases. Repeat loosening the knob by 1/4 turns until pressure after the Compressor becomes stable.
• Push the knob down and lock it.
• Check if pressure is increasing in the system. If solenoid valve is properly dumping, then keep loosening the knob by 1/4 turn until pressure after the Compressor stabilizes

How to Diagnose Discharge Valve

• Stop the Compressor,
• Discharge the compressed air in the system,
• Make sure isolation valve after the Compressor and other valves which may restrict the air flow from the Compressor and increase the Compressor air outlet pressure are all open and not restricting the air flow,
• Keep a valve open so that when the Compressor running at the full load, there will be no pressure built in the system,
• Run the Compressor,
• Observe the behavior of the discharge valve,
• When frequency is below minimum, frequency compressor designed (minimum frequency is the frequency compressor runs at for 20 seconds when stop button hit) discharge valve must dump air,
• When minimum frequency limit is exceeded, discharge valve must stop discharging completely,
• Close the valve kept open to discharge air pumped by compressor and left the whole system pressurized until pressure at the Compressor outlet reaches the desired pressure (PSET) set by the user,
  • if the Compressor element temperature is below 158F (70C), wait until the Compressor air outlet pressure reaches 4 PSI above the desired pressure (PSET) set by the user or
  • if the Compressor element temperature is over 158F (70C), wait until the Compressor air outlet pressure reaches 8 PSI above the desired pressure (PSET) set by the user.
• Observe discharge valve open and close, some kind of cycling discharge air and eventually will come fully open.
  At this stage, the Compressor system pressure must be stabilized around no more than 15 PSI (1 Bar) above the desired pressure (PSET) set by the user.

If solenoid valve constantly discharges air when pressure is below the desired pressure (PSET) set by the user

• Disassemble the valve and check if there is any dirt, damaged part inside the solenoid,
• Check solenoid valve electric,
• Stop the Compressor, keep the power on,
  

Compressors equipped with inverter & external 24VAC transformer

Open the inverter terminal compartment

• Locate the terminals PRa and Ca, or TA1 and TC1 according to the inverter type used,
  Measure the voltage in between PRa and Ca, or TA1 and TC1,
  There must be 24VAC read on the multimeter. If voltage is not read in between PRa and Ca, or TA1 and TC1,

Check power input phases to the Compressor (For 3 phase compressors)	If there is lack of phase, correct it
Check transformer inputs must be same with R and T power input voltage measurement	Check wiring of transformer
Check transformer outputs (24VAC must be available at the secondary)	no voltage read, change the transformer
Connect wires at terminals PRa and Ca, or TA1 and TC1, solenoid must be energized and a click sound should be heard,	if not, sound check cabling and change the solenoid, if needed

Compressors equipped with single inverter

*If the Compressor is connected to a single phase, make sure 2 input lines connected to the right input terminals and there is a jumper in between appropriate terminals.
• Type 1 Inverters require the first and last input terminals connected to the single phase power lines.
• Type 2 Inverters require the first and last input terminals connected to the single phase power lines and a jumper connection in between R and S (middle power input terminal)

• Locate the terminal solenoid valve is connected
• Take off the wires attached to those terminals.
• Empty compressed air in the system,
• Start the Compressor,
• Open a valve in the compressed air system to ensure pressure in the system is not going to increase,
• Measure the voltage across the terminals where solenoid connected. Voltage mut be 24VAC. If not, verify all the input power lines are within acceptable voltage limits. If compressor is connected as single phase 220v make sure power lines and if needed jumper in between input terminals are correctly done as explained in the How to Use Single Phase Compressors with 3 Phase power input
• Connect solenoid and check if solenoid valve is energizing. If solenoid valve is not energized check wiring to solenoid valve. If wiring is correct change the solenoid valve.