Siemens 6ES5988-3NA11 Fan Unit

Physical Dimensions and Mechanical Construction

The Siemens 6ES5988-3NA11 provides forced-air cooling for SIMATIC S5 racks. This unit measures 250mm in height, 25mm in width, and 150mm in depth. You can mount this unit in any standard S5 module slot without special tools. The fan unit weighs 0.52 kilograms , requiring secure installation for vibration control.

Internal Architecture and Component Density

The Siemens 6ES5988-3NA11 contains 28 individual components on its single PCB. Two brushless DC fans move air across adjacent modules for cooling. Each fan includes hall-effect sensors for speed monitoring and fault detection. Additionally, the unit features four rubber mounting grommets that reduce vibration transmission to the rack.

Energy Storage and Fan Operation

This fan unit stores 2.8 joules across two electrolytic capacitors. This energy reserve powers fan motor startup for up to 15 milliseconds during power dips. The storage also maintains speed monitoring circuits while the system recovers. Consequently, cooling continues with minimal interruption during brief supply fluctuations.

Parameter	Value	Unit
Dimensions (H x W x D)	250 x 25 x 150	mm
Weight	0.52	kg
Total components	28	pieces
Brushless DC fans	2	units
Hall-effect sensors	2	units
Rubber mounting grommets	4	units
Electrolytic capacitors	2	units
Total energy storage	2.8	J
Fan start-up hold time	15	ms
Fan diameter	60	mm
Airflow per fan	25	CFM
Fan speed	4500	RPM
Noise level (operating)	38	dBA
Operating voltage	24	V DC
Current draw (both fans)	400	mA
Power consumption	9.6	W
MTBF (mean time)	40,000	hours
Operating temperature	0 to 55	°C
LED indicators	2	units

Interface and Connectivity Features

The Siemens 6ES5988-3NA11 provides one 6-pin terminal block for 24V DC power input. A single 20-pin IDC header links the unit to the S5 backplane for status monitoring. You will also find two fan speed output signals for external indication. Each terminal accepts AWG 24 to AWG 16 copper wire for reliable connections.

Cooling Performance and Airflow

This fan unit moves 25 cubic feet per minute through each of its two fans. The combined airflow of 50 CFM provides active cooling for up to 8 modules. You should install this unit next to high-power modules such as CPUs and power supplies. The fans create positive pressure inside the rack to reduce dust accumulation.

Fan Monitoring and Fault Detection

The Siemens 6ES5988-3NA11 includes hall-effect speed sensors on each fan. The unit sends a low-speed alarm signal when fan RPM drops below 3000. A stalled fan detection circuit triggers a fault flag within 5 seconds of blockage. Furthermore, the module reports fan status to the S5 CPU through the backplane interface.

Diagnostic and Status Indication

Two LED indicators provide immediate feedback for fan operation and faults. Green FAN1 confirms normal operation of the first cooling fan. Amber FAN2 lights up when the second fan fails or runs at low speed. The absence of either LED indicates complete power loss to the fan unit.

Installation and Replacement Guidelines

You can install the Siemens 6ES5988-3NA11 in any unused S5 slot for cooling. The unit requires 50mm clearance at the front for proper air intake. You should replace both fans every 3 years under continuous 24/7 operation. The draw-out design allows fan replacement without removing the unit from the rack.

Environmental Specifications and Compliance

You can operate this fan unit from 0°C to 55°C ambient temperature without derating. Storage temperature ranges from -20°C to 70°C for long-term preservation. Non-condensing humidity tolerance spans 10% to 90% for industrial environments. This unit meets DIN 19240 standards and carries CE and UL marks for safety.