ECO operation at part load

Depending on the kind of capacity control and ECO connection, ECO operation is also possible at part load. The following table provides an overview.

Overview ECO operation at part load. ECO can always be used with speed-controlled part load (e.g. by frequency inverter), because the mechanical capacity control usually remains at 100% in this case (see Technical Information ST-420).
CR: capacity regulator
FI: frequency inverter
V_i: internal volume ratio (volume suction side / volume discharge gas side)
Compressor	Kind of mechanical capacity control	ECO connection	ECO feasible with mechanically controlled part load ?	ECO feasible with speed-controlled part load (FI)?
HS.53 .. 74	stepped CR by control pistons	fixed in the housing	yes, at capacity step 75%	yes
HS.85	dual (stepless or stepped) CR by CR slider	integrated in CR slider	yes	yes
HS.95	stepless CR by double slider (CR+V_i)	fixed in the housing	yes, at capacity ≥80% and after consulting Bitzer	yes
OS.53 .. 74 OS.A53 .. 74	stepped CR by control pistons	fixed in the housing	yes, at capacity step 75%	yes
OS.85 OS.A85	dual (stepless or stepped) CR by CR slider	integrated in CR slider	yes	yes
OS.A95 .. 105	stepless CR by double slider (CR+V_i)	fixed in the housing	yes, at capacity ≥80% and after consulting Bitzer (see below!)	yes (see below!)
CSH65 .. 95	dual (stepless or stepped) CR by CR slider	integrated in CR slider	yes	yes
CSH76 .. 96	dual (stepless or stepped) CR by CR slider	fixed in the housing	no	yes
CSW65 .. 95	dual (stepless or stepped) CR by CR slider	fixed in the housing	no	yes
CSW105	stepless CR by double slider (CR+V_i)	fixed in the housing	yes, at capacity ≥80% and after consulting Bitzer	yes
CSV	--	fixed in the housing	-- (only FI operation)	yes
VSK	stepped CR by control pistons	--	--	yes

OS.A95 and OS.A105: Pulsation muffler during economiser operation

For OS.A95 and OS.A105 compressors in ECO operation, a pulsation muffler in the economiser line is recommended resp. necessary. Two options are available:

a muffler system, consisting of muffler, check valve, control valve (one unit is required for OS.A95, two units are required for OS.A105)

Muffler system, consisting of muffler, check valve, control valve

a basic pulsation muffler designated SD42 (part no. ePARTS: 354 004 05)

Basic pulsation muffler SD42 in the ECO connection, part no. 354 004 05

For operation at condensing temperatures > 40°C and/or evaporation temperatures > 10°C, the muffler system is mandatory. In the remaining range, BITZER recommends the pulsation muffler SD42. For details see the following figure and table.

Application limit of OS.A95 and OS.A105 screw compressors during ECO operation, In the shaded area. the ECO muffler system is mandatory.

OS.A95 and OS.A105 compressors during ECO operation: recommended pulsation mufflers and combination with capacity regulation
Planned operating range	Pulsation muffler	Possible scope of capacity regulation
Operation in the shaded area of the application limit (t_c > 40°C and/or t_o > 10°C)	Economiser muffler system is mandatory	Slider 80% .. 100% and fixed frequency 50/60 Hz or slider 100% and variable frequency 25 .. 67 Hz
Operation outside the shaded area of the application limit (t_c < 40°C and t_o < 10°C)	Optional: economiser muffler system	Slider 80% .. 100% and fixed frequency 50/60 Hz or slider 100% and variable frequency 25 .. 67 Hz
	Optional: basic pulsation muffler SD42 in ECO connection	Slider 80% .. 100% and fixed frequency 50/60 Hz