Ingersoll-Rand HP50-PE manual Modulation Control, ACS Control Intellisys w/ Modulation Option only

OPERATING INSTRUCTIONS – INTELLISYS w/ MODULATION CONTROL 33

MODULATION CONTROL

For those plants which have relatively high constant air demand relative to the compressor capacity, the recommended control mode is modulation.

The modulation control system retains the features of the on–line / off–line control, but also provides for throttling of the inlet flow up to the off–line air pressure setpoint value.

By applying line pressure to an adjustable modulator valve, the throttling position of the inlet valve is controlled, thus allowing the modulator to ”trim” the inlet valve position as dictated by the line pressure.

The modulating pressure range is about 4 psig (0.3 BAR) and the modulator normally should be set to straddle the compressor rated pressure. Modulation begins when the line pressure reaches about 99 percent of the compressor rated pressure and continues as/if the line pressure rises. Modulation becomes stable when the compressor output equals the plant air demand. When the modulation is at the factory setting, the flow will be reduced to 60 percent of the compressor rated capacity (as indicated in Figure 1).

Capacity control of machines supplied with electro–pneumatic control and the modulation option can be manually switched from on–line/off–line to modulation (MOD) via the control mode switch (SS) located adjacent to the pressure switch.

MODULATE TO 94% CAPACITY

FLOW	MODULATE TO
	85% CAPACITY
RATED	MODULATE TO
% OF	72% CAPACITY
	MODULATE TO
	60% CAPACITY

% OF RATED LINE PRESSURE

KEY

ANormal settings of modulator

BOptional field settings of modulator

CIntellisysR off–line set point

FIGURE 1

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ACS CONTROL (INTELLISYS w/ MODULATION OPTION ONLY)

For compressors supplied with IntellisysR control and modulation option, ACS control will allow the compressor to automatically switch between on–line/off–line and modulation control, depending on air demand.

If the air demand has decreased to a level below the 60 percent modulated output, the line pressure will increase slightly to actuate the IntellisysR. The compressor will then shift to the off–line control position, and operate unloaded with the compressor vented.

It is sometimes desirable to begin modulation at a higher pressure than the standard factory setting, thereby increasing the modulated capacity at the time the IntellisysR is actuated. Refer to Figure 1 for modulated capacities available when this is done.

The compressor will then operate to deliver full capacity air to the plant system. If the plant air system pressure rises to that of the IntellisysR off–line set point, pressurized air will be sent to the inlet valve causing it to close, and to the blowdown valve, causing it to open.

The compressor will continue to run unloaded, but since pressure levels have reduced, it will do so with a minimum power draw.

The IntellisysR has a fixed minimum differential of 10 psi between the off–line air pressure setting and the on–line air pressure setting. The differential may be increased by adjusting the on–line air pressure setting of the IntellisysR.

The automatic control selector (ACS) is designed to continuously monitor the plant air demand and select either the on–line/off–line, or the modulate control mode – whichever is most desirable at any time during an operating day.

It allows the compressor to operate in its most efficient mode thereby reducing power costs.

When the compressor operates in the on–line/off–line control mode, the length of time the compressor remains in the ”off–line” condition is an indication of the plant air demand. IntellisysR controller is sensing and awaiting a sufficient line pressure decrease before signalling a shift to the on–line mode. If the ”off–line” time period is relatively short, thereby indicating a high demand for air, it is preferable to shift the control system to upper range modulation.

The IntellisysR does this, and does it automatically if the compressor unloads 3 times within a 3 minute time period.

If later, the plant demand decreases, and even under modulate control the line pressure reaches the setting of the IntellisysR controller, and the control shifts to the ”off–line” mode, the time in this mode will still be monitored. A long ”off–line” time period indicates a low plant air demand, indicating the desirability of operating in the on–line/off–line mode.

The IntellisysR then does this, and does it automatically if the compressor operates unloaded for more than 3 minutes.

Modulation Only

If MODULATION ONLY is turned on in the setpoint routine, the unit will shift to Modulation control mode immediately when the unit is running. The 3 cycles within 3 minutes time period required for ACS to change to Modulation mode is bypassed. The unit will stay in Modulation mode until the unit runs unloaded for 3 minutes (the unit then returns to ACS control) or MODULATION ONLY is turned off via the set routine.

Delay Load Time

This is the amount of time the line pressure must remain below the on–line setpoint before the compressor will load or start (if the unit was stopped due to an auto start/stop situation). Setting the load delay time to 0 will cause no delay. When the delay load timer becomes active, the display will switch to package discharge pressure (if not displaying package discharge pressure at that time) and then display the delay load count down. Once the count down reaches 0, the unit will load or start and the display will return to line pressure. The display select button is inactive during the delay load count down.

SSR UP6 40, SSR UP6 50PE, SSR UP6 50PEI, HF50–PE,

EP50–PE, HP50–PE, HXP50–PE