Motor Branch Circuits acc. to UL · Page 12 Issue 07/2013 Industrial Control Panels and Machinery for North America Industry Sector Assembly Options – Single or Group Installation

© Siemens Industry Inc. 2013. All Rights Reserved.

Motor Branch Circuits acc. to UL

Definition of Terms / Explanations

Overview of Basic Devices

Construction Types acc. to UL 508

Self-Protected Combination Motor Controller

Various types – Single Installation and Group Installation

Suitable for Tap Conductor Protection in Group Installation

Explanations

UL guidelines, chapter 6.2 / 6.3


Industry Sector Page 2 Issue 07/2013 Industrial Control Panels and Machinery for North America

Overview – standard devices

Motor Starter Combination – Example

UL guidelines, chapter 6.2.4

Pos Basic Type UL Norm

21 Field wiring Terminal on the device

11 Disconnect switch UL 98

13 Fuse, e.g. Class JUL 98

UL 512

3 / 5 Controller UL 508

4 Overload protection UL 508

22 Internal WiringUL 508A

NEC §310

23 Field wiring Terminal UL 1059

24 Motor disconnect (Option) UL 508

25 Motor, 460 V SF 1,15 (name plate)

12Circuit Breaker

Overload & Short CircuitUL 489

3RV

3VL

3RT

MCS

VB2

3RU / 3RB

3LD

a

b

c

d

8WA

As minimum, the following

shall be installed acc. to

UL508A:

Disconnect – (a)

Short Circuit Protection – (b)

Motor Controller – (c)

Overload Protection – (d)



Construction Types in acc. with UL508 / Table 76.2

Various constructions of combination motor controllers – A / B

M

M




Various constructions of combination motor controllers – C / D

x

M

x

M




Various constructions of combination motor controllers – E / F

x

M

x

M



Definition of BCPD acc. UL

Branch Circuit Protection Device (BCPD):

A fuse or circuit breaker that has been evaluated to a safety standard for providing overcurrent protection

UL 248-4…12 fuse:

FUSE, BRANCH CIRCUIT TYPE – A fuse of Class CC, G, H, J, K, L, R, and T. These fuses are able to provide

branch circuit protection

UL 489 Circuit Breaker – inverse time:

INVERSE-TIME CIRCUIT BREAKER – A circuit breaker in which a delay is introduced into the tripping action

of the circuit breaker. The delay decreases as the magnitude of the current increases. These circuit breakers

are able to provide branch circuit protection.



BCPD – Branch Circuit Protection Devices

Inverse time C.B.

UL489 C.B. / CSA 22.2 No. 5-09

3RV27/28 3RV17/18 3VL

Class CC Fuses acc.

UL248-4 / CSA 22.2 No. 248.4

3NW



Motor Starters vs. Type E combination motor controller

Type E combination motor controller

acc. UL508 / CSA 22.2 No. 14

Approved as branch circuit protection device

for motor loads only!

Manual motor controller / motor starter

acc. UL508 / CSA 22.2 No. 14

Approved as motor disconnect and motor overload protection

can not be used as a branch circuit protection device!

3RV2

3RV2

3LD



Definition of Terms / Explanations – Service Factor SF

Note:

SF = 1.0 corresponds to a setting value of 0.92 FLA

SF ≥ 1.15 corresponds to a setting value of 1.0 FLA

Definition:

The service factor - SF - is a measure of periodically overload

capacity at which a motor can operate without overload or damage.

The NEMA standard Service Factor for fully enclosed motors is SF 1.0

SF: service factor SF 1.0 / SF 1.15 to be used for the overload setting of an overload relais

Important parameter for the setting of the Bi-metal relay. Only a Service Factors other than SF1.0 have to be

indicated on the nameplate.

SF1.0 is normally not indicated on the name plate. NEC 2011 – 430.32 (1)



Assembly Options – Single or Group Installation

UL 508A differentiates between 2 installation variants:

Single installation = single motor circuit (chapter 31.3)

Group installation = motor groups (chapter 31.4)

1. Single installations

Manual self-protected combination motor controller (SPCMC) acc. to UL508 Type E (only 3RV)

Manual / magnetic self-protected combination motor controller (SPCMC) acc. to UL508 type F

(e.g. 3RA1 load feeder = 3RV+3RT)

Manual motor controller (only 3RV)

Manual / magnetic motor controller (3RV and 3RT)

2. Group installations / branch circuit protection for motors

Group installations

Group installations with additional approval

„Suitable for tap conductor protection in group installation“ (additional tests with UL508)



Basic rules for sizing a motor branch circuit – Example



Self-Protected Combination Motor Controller

Solution with SIRIUS

Excerpt from the UL

configuration manual

with tested combinations

(with UL report)



What is the definition of a Group Installation

Definition of a Group Installation:

A group of loads, consisting of two or more

motors, or one or more motors and other loads,

are able to be protected by a single set of

branch circuit fuses or inverse – time circuit

breaker

as specified in Method A, B or C (see the following slides for details)

BCPD

Starter Starter Contactor

Motor Motor Heater



Sizing of Branch Circuit Protection for Motor Groups acc. UL/NEC

Method A – General requirements

Branch circuit protection not >20A @125V max., or not > 15A @600V

Each motor not >6A FLA,

Branch Circuit Protection not greater than any component restrictions, and

Coordinated with requirements for any non-motor loads per 31.4.4

31.4.4 For a group that includes other (non-motor) loads, additional branch circuit fuses or

inverse time circuit breakers shall be provided in each circuit

Exception: Where the ampere rating of the branch circuit protection determined in 31.4.1 does not

exceed the applicable branch circuit protection requirements in 31.5 – 31.8 for a non-motor load in the group,

additional branch circuit protection is not required




Method A – Assembly

BCPD


Motor Motor Heater

Step 3: Branch Circuit

Protection Device does not exceed:

20A @ 125V

15A @600V

Step 1: Check starter for

specific instructions (UL certificate)

Step 2: FLA of each motor

may not exceed 6A

Step 4: Branch Circuit Protection meets

requirements in 31.4.4 for non-motor loads




Method B – General requirements

BCPD size complies with single motor requirements for each individual motor

Tap conductors not less than 1/3 the ampacity of branch circuit conductor,

or not less than 1/10 the amp rating of branch circuit protection if Manual Motor Controller

marked “Suitable as Tap Conductor Protection in Group Installations”

Additional branch circuit protection for non-motor loads unless branch circuit protection

device also meets 31.5 through 31.8 for non-motor loads in group

C.B. inverse time:

400 percent of full-load motor current for an inverse-

time circuit breaker not exceeding 100 amperes

300 percent of full-load motor current for an inverse-

time circuit breaker rated more than 100 amperes;

Fuses:

225 percent of full-load motor current for a time delay

(dual element) fuse

400 percent of full-load motor current for a non-time

delay fuse or a Class CC time delay fuse not

exceeding 600 amperes;




Method B – Assembly

BCPD


Motor Motor Heater

Step 1: Select Branch Circuit

Protection Device not to exceed

single motor sizing for smallest motor

Step 2: Ampacity of tap conductors

not less than 1/3 ampacity, or

1/10 rating of BCPD when manual

motor controller is marked as “Suitable

for tap conductor protection in group

installations

Step 3: Check if non-motor loads

require additional protection




Method C – General requirements

All controllers marked for group installation with BCPD sized at the lesser of:

- the smallest group installation marking for BCPD, or

- the calculated BCPD for the largest motor + FLAS’s of other loads

Tap conductors sized per Method B

Non-Motor loads also protected per Method B

Applies to power conversion equipment with DC converter and inverter

sections on “common bus”




Method C – Assembly

BCPD


Motor Motor Heater

Step 2: Size BCPD based on smaller

1.) the size required of the largest motor plus

FLA of all other loads

or

2.) lowest BCPD marking for motor grouping

Step 3: Verify tap conductor size

Step 1: Verify that all load side

devices are “Suitable for tap conductor

protection in Group Installations

Step 4: Check if non-motor loads

require additional protection



How to size the Branch Circuit Protection Device

for Motor Groups acc UL/NEC?

BCPD


Motor Motor Heater

Verify if non-motor

loads require

additional protection

11 Amps 5 Amps 5 Amps

Example for UL Circuit Breaker:

1.) 11 Amps x 250% = 27,5 Amps

2.) 27,5A + 5A + 5A = 37,5 Amps

37,5 Amps for the BCPD

Next Standard size is 40 Amps

Tap Conductors:

125% of the largest motor load

+ 100% of additional loads = 23,75 Amps

23,75 / 3 = 7.9 Amps

UL508A Table 28.1 for ampacities of conductors:

minimum 14 AWG for Power Circuits



Example with the 3RM1 motor starter

16A max per infeed

X

Y

Ampacity Y ≥ 1/3 Amapacity X



Explanations, Notes, Rating Plate Data

Motor branch circuit – nameplate of 3RV circuit breakers

Indication of hp ratings for

200-208 V, 230 V, 460 V, 575 V

General safety instructions

Only CU wires for 75°C are allowed

Ratio of 125% of tripping current : setting current

Breaks all phases simultaneously

Max. permissible

motor‘s full load amps

(FLA max.)

Reference to the use in

combinations with

contactors and soft starters

Manual motor controller, suitable as tap conductor

protection, in group installations

motor disconnect

suitable for group installation

max. permissible grouping fuse / CB

max. permissible short circuit current

Self-protected combination motor controller (E / F)

with reference to adapter

max. permissible short circuits for 240 V, 480Y/277 V, 600Y/347 V

Example: 3RV10 21



Changes in the standard for industrial control devices

This change is not addressed to the user of industrial control devices

but to the manufacturer of control devices!

Complete transition

till Nov. 2017

UL 60947-4-1 is

aligned and

harmonized

with the

IEC 60947-4-1



What does the transition from UL508 to UL60947-4-1 affect?

Different type of coordination are

available for

Electromechanical contactors

and motor-starters

Type of co-ordination 1 Type of co-ordination 2



Panel Marking

According UL508A – § SB5



Predictable Reaction

Type of co-ordination “1”

UL 60947-4-1 (excerpt):

With type of co-ordination “1”, the contactor or starter must not endanger persons or the

installation in the event of a short circuit and need not be suitable for further operation without

repair and renewal of parts.

Result for the machine or machine operation:

The contactor and/or overload relay might be defective

The components might be unsuitable for further operation

Insecure personnel and system protection with further operation

Uncertain functionality of the components

The components should be replaced

Consequences:

Long downtimes

High repair efforts



Predictable Reaction

Type of Co-Ordination “2”

UL 60947-4-1 (excerpt):

With type of co-ordination “2”, the contactor or starter must not endanger persons or the installation in

the event of a short circuit and must remain suitable for further operation. The risk of contact welding

is given. In this case, maintenance instructions have to be provided by the manufacturer.

Note: If manufacturer recommendations are not complied with for the application of an SCPD, the type of co-

ordination is questionable. The risk of contact welding is given.

Manufacturer’s maintenance instruction for opening the contact pieces is required

Result for the machine or machine operation

The contactor and/or overload relay may be slightly welded

Easy breaking-open of contacts required in case of welding

Consequences:

Short downtimes

Low repair effort



Where can I get these values?

Ask your supplier for SCCR ratings for Type 1 and Type 2 co-ordination

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../01_documents for participants/Siemens workshop - industrial control panels for North America/Attachments/UL60947-4-1_White_Paper%5blo-res%5d.pdf


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6_Motor branch circuits acc. to UL508A_en.ppt

Thank you for your attention!

Note / Disclaimer

The circuit examples and interpretations of the standard are non-binding and do not claim

completeness concerning configuration, equipping and contingencies. They do not represent

customized solutions but merely provide support for typical tasks.

Every user of this presentation assumes full responsibility for the proper operation of the described

products. This presentation does not relieve you of your obligation to ensure safe application,

installation, operation and maintenance.

By using this presentation you agree that Siemens cannot be held liable for damage beyond the

above-described liability provisions. We reserve the right to modify this document at any time without

prior announcement.

Many tables and texts in this description were directly taken from NEC 2011 and the UL standards.

Every user has to regularly check whether the quoted references are still up-to-date.

The final decision as to whether an application complies with the corresponding American standards

and regulations lies with the end customer or any organization respectively authorized by him (e.g.

authority having jurisdiction, AHJ).

Questions?

Documents

Motor Branch Circuits acc. to UL · Page 12 Issue 07/2013 Industrial Control Panels and Machinery for North America Industry Sector Assembly Options – Single or Group Installation