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Maintenance Bypass Box

for Single UPS

Installation & Operation Guide

About this Guide

This guide contains information about installing and operating the 

Delta Maintenance Bypass Box for Single UPS (MBB-S). Before you 

install this unit, please read the safety instructions below.

Save these Instructions 

This guide contains instructions and warnings that should be followed 

during the installation, operation and storage of this product. Failure 

to heed these instructions and warnings will void the product warranty.

This product is designed for indoor use only in a controlled 

environment away from excess moisture, temperature extremes, 

conductive contaminants, dust or direct sunlight.

•  Do not connect the MBB-S to an ungrounded outlet or extension 

   cords or adapters that eliminate the connection to ground

•  Do not use this equipment in the presence of flammable substances.
•  The power requirement for each piece of equipment connected to 

   the MBB must not exceed the individual outlet's load rating.

•  Do not drill into or attempt to open any part of the MBB housing. 

   There are no user serviceable parts inside.

•  Do not modify the MBB-S.
•  Do not use the MBB-S if any part of it becomes damaged.
•  Never install electrical equipment during a thunderstorm.

Safety Precautions

To reduce the risk of personal injury from electric shock, you must 

observe the following safety precautions when placing, installing, 

operating, or performing maintenance on the Delta MBB-S. 

Warnings!

•  

Elevated Operating Ambient

 - If installed in a closed or multi-unit 

   rack assembly, the operating ambient temperature of the rack 

   environment may be greater than room ambient. Therefore, 

   consideration should be given to installing the equipment in an 

   environment compatible with the maximum ambient temperature 

   (Tma) specified by the manufacturer.
•  

Reduced Air Flow

 - Installation of the equipment in a rack should 

   be such that the amount of air flow required for safe operation of the 

   equipment is not compromised.

•  

Mechanical Loading

 - Mounting of the equipment in the rack 

   should be such that a hazardous condition is not achieved due to 

   uneven mechanical loading.

•  

Circuit Overloading

 - Consideration should be given to the 

   connection of the equipment to the supply circuit and the effect that 

   overloading of the circuits might have on over-current protection and 

   supply wiring. Appropriate consideration of equipment nameplate  

   ratings should be used when addressing this concern.

•  

Reliable Earthing

 - Reliable earthing of rack-mounted equipment 

   should be maintained. Particular attention should be given to supply 

   connections other than direct connections to the branch circuit (such 

   as use of power strips).

Precautions for Rack Mounting 

Delta strongly recommends that you do not perform maintenance on 

the MBB-S if it is receiving input power. 

•  To reduce your risk of personal injury by electric shock, you must:
•  Be a certified electrician trained in live electrical installation
•  Always work with another qualified person
•  Know how to disconnect electricity to the MBB and data center in 

   case of emergency

•  Wear the right protective equipment
•  Use double-insulated tools
•  Strictly follow local and site regulations

Maintenance with Input Power 

This is a Class A product. In a domestic environment this product may 

cause radio interference in which case the user may be required to 

take adequate measures.

Electromagnetic Interference

The Delta Maintenance Bypass Box for Single UPS (MBB-S) lets you 

isolate a single UPS from the load without interrupting power to 

essential applications. This allows you to perform scheduled UPS 

maintenance or UPS replacement without disrupting power. 

The MBB-S easily transfers power between normal and bypass mode 

using a rotary switch. 

1. MBB-S Overview

The Delta MBB-S package should contain the following items:

2. Package Contents

3. Installing the MBB-S

CAUTION: 

•  A licensed electrician must install the Delta MBB-S. 
•  The UPS unit must be switched off and unplugged before 

   installation.

•  Install a utility circuit breaker for input wiring.Refer to the drawing & 

   table below.

Quantity

Item

1pcs

MBB-S

1set

Fixing Plate

1set

Ear bracket

1pcs

Parallel Cable

1pcs

MBB-S Installation & Operation Guide

4pcs

Cable gland

12pcs

Terminal

System

Voltage

Current Full 

Load Nominal

External Input Circuit 

Breaker Typical

Wire Size 

Typical (mm

2

)

Input

Output

Input

Output

For  

5/7k  

UPS

For 

9/11k 

UPS

For  

5/7k  

UPS

For 

9/11k 

UPS

MBB-S

200/208/220/

230/240Vac 

1Phase

50A

40A 

2Pole

63A

2Pole

8

10

Remark:  The External Input Circuit Breaker must use the components 

approved for its safety certification.

4. Fixing the MBB-S 

4-1. Tower Configuration

1.  Place the MBB-S on the top rear of the UPS unit.

2.  Locate and align the fixing holes on the MBB-S and UPS unit.Use 

     a screwdriver to fasten the fixing plates with the provided screws 

     and attach the MBB-S to the UPS unit.
3.  Place the UPS and MBB-S in the upright tower position and secure 

     the mounting feet.

4-2. Rack-mount Configuration

1.  Attach the mounting brackets to the MBB-S using the M4*6mm 

     screws that came with the brackets.
2.  Choose a location in the rack for the MBB-S. 
3.  Install the MBB-S on your rack using the screws and cage nuts. 

(The screws and cage nuts are provided with the rack frame.)

Fig. 2

5. Making Connections

The steps below show you how to connect power cables so the path 

of AC power flows through the MBB-S to the UPS, or alternately, 

bypassing the UPS and directly to the connected load.

Fig. 3

5-2.  Attach the cable glands to the cable entry boxes. Insert the  

        cables through the cable glands and then insert the leads of the 

        cables into the terminal blocks and fasten screws. See Fig. 4.

Fig. 4

5-1.  Unscrew and remove the cable entry boxes on the MBB-S. 

        See Fig. 3.

(The mounting feet are provided with the UPS or from a dealer.)

Fig. 1

 

 

MBB-S 

x8

x6

x4

x4

UPS OUTPUT

LOAD

UPS INPUT

AC INPUT

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