Eaton SPB Drawdown Switch Maintenance Guide

Eaton Cutler Hammer SPB Pull out Transfer Switch: A Complete Guide to Operation, Maintenance, and Troubleshooting

In critical power supply systems, automatic transfer switches (ATS) are the core equipment that ensures uninterrupted power supply to loads. The Cutler Hammer SPB series withdrawable transfer switch, with its high tolerance rating, compact vertical layout, and flexible bypass isolation design, is widely used in places such as hospitals, data centers, and industrial plants that require extremely high power continuity. This article combines the technical manual of SPB withdrawable transfer switch, providing a systematic technical reference for electrical engineers and on-site maintenance personnel from installation and commissioning, daily operation, use of the pull-out mechanism, bypass isolation maintenance to common troubleshooting.

System Overview and Model Identification

The SPB series transfer switch adopts insulated shell switch or circuit breaker as the main contact, with a rated current range covering 600A to 4000A. Its design features include:

Vertical compact layout: The normal and emergency power switches are arranged vertically to save space inside the cabinet.

High withstand rating: When combined with upstream circuit breakers, the withstand current can reach 65kA~100kA at 240V/480V/600V (depending on the model and the optional high withstand option 17C); When combined with a fuse, it can reach a maximum of 200kA.

Pull out structure: The switching element can be pulled out for maintenance or replacement, while maintaining load power supply (with the need for bypass isolation function).

Energy storage operating mechanism: electric or manual spring energy storage, fast opening and closing speed, transfer time less than 5 cycles.

Model identification example: ATVISPE31000XSU

AT: Automatic Transfer Switch

VI: Vertical installation

SPE: SPB type withdrawable insulated housing switch

3: Three poles

1000: Rated current 1000A

X：480V/60Hz

S: NEMA Type 1 enclosure

U: UL Listing

Understanding the model is helpful for spare parts selection and technical support communication.

Installation and wiring points

2.1 Unpacking and Storage

After the equipment arrives, the packaging should be checked for any damage and transportation damage should be recorded. Internally, there is a plastic bag containing test reports, wiring diagrams, instructions, and warranty cards, which should be properly stored. If not installed temporarily, it should be stored indoors in a clean and dry environment (temperature -20~85 ℃, humidity ≤ 80%), and outdoor storage is strictly prohibited.

2.2 Installation location and seismic requirements

Choose a flat and sturdy installation surface, avoiding damp, high-temperature, and dusty areas. For applications requiring seismic certification (option 42), the provided clamps and 1/2-13 UNC Grade 5 hex bolts must be used with a tightening torque of 50 ft lbs (68 Nm), as shown in Figure 4-1. Switches without seismic fixation do not meet the requirements of UBC Zone 4.

2.3 Cable Connection

The wire diameter of power and load cables should be selected according to Table 4.1 (e.g. 2 wires per phase of 800-2000A, 4/0-500 MCM or 6 wires of 500-750 MCM). Attention when wiring:

Before entering the cabinet, the insulation of the cable should be tested to prevent pulling.

When stripping the wire, avoid damaging the conductor. Aluminum conductors should be coated with anti-oxidation composite grease.

The torque of the wiring terminal should be executed according to the label, as being too tight or too loose can cause heating.

Connect control wires (such as engine start signals) to red terminal blocks 51 and 52 (bypass isolation type connections 51A and 52A).

2.4 Voltage selection adjustment

The voltage selection panel provides 208~600V multi tap transformers, which can be quickly switched through small plug-in connectors. Make sure the selected voltage is consistent with the system voltage, otherwise it will damage the equipment.

Operating mechanism and energy storage mechanism

The SPB switch adopts an energy storage operating mechanism. After each closure, the mechanism will automatically re store energy (through an electric operator). If manual operation is required, the operating handle must be pulled several times until the energy storage indicator shows "energy stored", and then the "close" button (Figure 5-1, 5-2) must be pressed.

3.1 Key points of manual operation

Open Transition: There is a mechanical and electrical interlock between two switches to prevent simultaneous closure. When manually closing the normal switch, the emergency switch cannot be closed.

Closed Transition: The contacts have overlapping designs, and misuse may lead to serious accidents. Manual closure must strictly follow the steps in Figure 5-3.

3.2 Automatic Operation

When the normal power supply loses voltage or the voltage is lower than the preset value, the logic controller (ATC-600/800) automatically issues a command and the emergency switch is closed. After the normal power supply is restored, the system automatically switches back to the normal side. Please refer to the corresponding logic manual for the specific timing and parameter settings of automatic operation.

Detailed explanation of Drawout Mechanism

The pull-out mechanism allows switch components to be removed or inserted without dismantling the primary cable. It has four positions:

Description of secondary control contacts for position main circuit contacts

CONNECTED is connected to its normal working position

TEST disconnection and connection can test the control circuit, but the load is not powered

DISCONNECT: Disconnected and isolated state

WITHDRAWN: The disconnect switch can be fully withdrawn

4.1 Shake in and shake out operation

Use a 3/4 inch socket wrench to insert the pull-out drive shaft (Figure 6-1), rotate clockwise to move the switch in the CONNECTED direction, and counterclockwise to move it in the WITHDRAWN direction. Before operation, the padlock wrench must be lifted. If the contact is forcefully shaken when closed, the switch will automatically trip (causing the load to lose power).

4.2 Operation interlock

The switch can only be closed in the CONNECTED, TEST, DISCONNECT positions. Unable to close at WITHDRAWN position.

The mechanical interlock of the bracket ensures that the switch is always in the open state when connecting or disconnecting the main contact.

4.3 Switch extraction and rotation maintenance

When it is necessary to rotate the switch component for inspection, first return the switch to the DISCONNECT position and remove the dead front shield on the front panel. Then pull out the switch to make the front wheel leave the guide rail and continue to straighten it forward until the rear wheel enters the original groove of the front wheel (Figure 6-2, 6-3). When rotating, pay attention to protecting the secondary control plug, reset it after completion, and reinstall the dead baffle.

Operation Guide for Bypass Isolation Switch

The bypass isolation type (BI) transfer switch allows for maintenance or replacement of the main switch without interrupting the load power supply. It includes four sets of switches: normal switch, emergency switch, normal bypass switch, and emergency bypass switch.

5.1 Indicator Light Panel Description

Meaning of panel indicator lights:

Normal Isolated: The normal switch has been pulled out and the main circuit is disconnected

Emergency Isolated: The emergency switch has been pulled out

Normal Bypass: The normal bypass switch has been closed

Emergency Bypass: The emergency bypass switch has been closed

Normal Position Energized: The normal switch supplies power to the load

Emergency Position Energized: The emergency switch supplies power to the load

5.2 Typical operation: Switch the normal switch to the bypass and isolate it

Set the generator set selector switch to OFF to prevent accidental start-up.

Remove the key from the emergency switch key interlock (rotate counterclockwise while pushing the lever upwards), the emergency switch is locked and cannot be closed.

Insert the key into the normal bypass switch and turn it clockwise to unlock.

Manually close the normal bypass switch → the "Normal Bypass" light is on.

Open the switch and shake out the normal switch (see Section 4) → The "Normal Isolated" light is on, and the "Normal Position Energized" light is off.

Check and repair the normal switch.

Shake in the normal switch → the switch automatically stores energy and closes → the "Normal Isolated" light goes off, and the "Normal Position Energized" light comes on.

Open the normal bypass switch and turn off the "Normal Bypass" light.

Remove the key from the bypass switch (rotate counterclockwise) to lock the bypass switch.

Insert the key back into the emergency switch and unlock clockwise.

Restore normal automatic operation.

The operations of emergency side bypass, normal → emergency bypass, emergency → normal bypass, etc. are detailed in section 7.3 of the manual, and the principles are similar.

5.3 Manual switching in bypass mode

Switching from normal bypass to emergency bypass: First lock the normal switch (take the key), unlock the emergency bypass switch, open the normal bypass, and close the emergency bypass.

The reverse operation is the same.

Testing and troubleshooting

6.1 Regular testing

Mechanical and electrical testing should be conducted after installation and during planned power outages. Mechanical testing involves manual energy storage and opening/closing of switches; The electrical test uses the test button on the panel (if any), and must be turned back to the "AUTO" position after the test.

6.2 Common Fault Handling Process

Problem 1: The conversion switch does not work at all

Step 1: Check if all plugs and sockets are securely plugged in.

Step 2: Measure whether the voltage at the normal switch terminal reaches the system voltage.

Step 3: Check if the voltage selection plug is in the correct position.

Step 4: Observe for any obvious burnt components, identify the cause, and replace them.

Step 5 (Closed Conversion Type): Refer to Figure 5-2 for manual operation and check if there is power on the load side. If not, check the power connection and switch mechanism.

Step 5 (Switching type): Press the close button of the normal switch to check if there is power on the load side.

Problem 2: Cannot automatically switch to the normal side

Check if the voltage of N1, N2, and N3 lines is normal.

Has the normal switch stored energy? If energy storage is not available, first address the issue of "switch not automatically storing energy".

Has the emergency switch been turned off? If not disconnected, handle it first.

Measure whether there is 120VAC ± 10V between terminals A9-A8 of the shunt release coil of the emergency switch. If there is, check the shunt coil; If there is none, check the wiring.

Measure whether there is 120VAC ± 10V between terminals A1-A2 of the closing coil of a normal switch. If there is, check the closing coil; If there is none, check the wiring.

Problem 3: Cannot automatically switch to the emergency side

Check the voltage of E1, E2, and E3 lines.

Does the emergency switch store energy? If not, handle it first.

Measure the voltage of the shunt coil A9-A8 of the normal switch (which should be 120V).

Measure the voltage of emergency switch closing coils A1-A2.

Problem 4: The switch does not automatically store energy

Measure the voltage between terminals A6 and A2 of the non energy storage switch, which should be 120VAC ± 10V. If there is voltage, check the internal electric operator of the switch; If there is no voltage, check the A6-A2 wiring.

If the above steps are still not resolved, record the SO number, GO number, catalog number, and other information, and contact Cutler Hammer technical support.

Maintenance and spare parts replacement

7.1 Regular maintenance cycle

Suggest following Table 9.1:

Monthly: visually inspect for dust, foreign objects, looseness, and signs of overheating.

Every six months to one year: power off, clean dust (use a vacuum cleaner, prohibit high-pressure blowing); Check and tighten the terminals; Check the insulation for cracking and carbonization once; Check the secondary control wiring.

For NEMA 3R type: Check the air filter and replace it if clogged (order number TSAFDO).

7.2 Handling when the switch is not frequently activated

If the switch is not switched during operation for a long time, it should be manually stored and opened/closed regularly to allow the contacts to produce wiping action and prevent oxidation.

7.3 Removal of NEMA 1 and NEMA 3R enclosure cover plates

NEMA 1: Use a 3/8-inch wrench to remove the screws (and finally remove the top screw), place your foot on the bottom to slowly tilt the top, and then lift up the cover plate. When reinstalling, first hang it into the bottom, push it into the top, and tighten the screws (torque 8 ft lbs).

NEMA 3R: Keep the sealing gasket when disassembling, use the randomly provided cover plate to lift the handle and insert it into the screw hole, pull out the cover plate to detach the lower flange from the lower crossbeam. When installing, first slide the flange on the cover plate under the roof flange, then push it into the lower part, install screws and sealing washers, and apply the same torque of 8 ft lbs.

7.4 Common spare parts

Air filter replacement kit: TSAFDO (Figure 10-1)

Replacement kit for padlockable handle: TSDPZFS (Figure 10-2)

Safety precautions and compliance with standards

Dangerous voltage: After opening the cabinet door, there is a lethal voltage inside. Before maintenance, the upstream power supply must be disconnected and locked.

Closed conversion model: The contact overlap structure is special, and any misoperation (such as forced opening and closing during parallel connection) may cause serious accidents. Be sure to follow Figure 5-3.

Pull out operation: If the contact is closed when lifting the padlock wrench, the switch will automatically trip, causing the load to lose power. Make sure to disconnect before pulling out the rack.

UL standard: SPB transfer switch complies with UL1008 (automatic transfer switch), UL489 (circuit breaker), and UL1087 (insulated shell switch), and has passed cUL certification. NFPA 99/110 is optional.

Seismic resistance: Option 42 provides UBC Zone 4 seismic resistance certificate, but must be installed strictly using clamps according to Figure 4-1.