SMA SUNNY CENTRAL 250U User manual

DisconACDC_SCUS-IUS103110 | 98-4009010 | Version 1.0
US
Accessories for Sunny Central
Disconnect Unit for
Sunny Central 250U /500U / 500HE-US/CA and
Sunny Central CP
Installation Guide

SMA America, LLC
2 DisconACDC_SCUS-IUS103110 Installation Guide

SMA America, LLC 
Installation Guide DisconACDC_SCUS-IUS103110 3
Copyright © 2010 SMA America,LLC. All rights reserved.
No part of this document may be reproduced, stored in a retrieval system, or transmitted, in any form
or by any means, electronic, mechanical, photographic, magnetic or otherwise, without the prior
written permission of SMA America,LLC.
Neither SMA America,LLC nor SMA Solar Technology Canada Inc. makes no representations,
express or implied, with respect to this documentation or any of the equipment and/or software it may
describe, including (with no limitation) any implied warranties of utility, merchantability, or fitness for
any particular purpose. All such warranties are expressly disclaimed. Neither SMA America,LLC nor
its distributors or dealers nor SMA Solar Technology Canada Inc. nor its distributors or dealers shall
be liable for any indirect, incidental, or consequential damages under any circumstances.
(The exclusion of implied warranties may not apply in all cases under some statutes, and thus the
above exclusion may not apply.)
Specifications are subject to change without notice. Every attempt has been made to make this
document complete, accurate and up-to-date. Readers are cautioned, however, that
SMAAmerica,LLC and SMA Solar Technology Canada Inc. reserve the right to make changes
without notice and shall not be responsible for any damages, including indirect, incidental or
consequential damages, caused by reliance on the material presented, including, but not limited to,
omissions, typographical errors, arithmetical errors or listing errors in the content material.
All trademarks are recognized even if these are not marked separately. Missing designations do not
mean that a product or brand is not a registered trademark.
The Bluetooth® word mark and logos are registered trademarks owned by Bluetooth SIG, Inc. and
any use of such marks by SMA America,LLC and SMA Solar Technology Canada Inc. is under
license.
SMA America, LLC
3801 N. Havana Street
Denver, CO 80239 U.S.A.

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4 DisconACDC_SCUS-IUS103110 Installation Guide
IMPORTANT SAFETY INSTRUCTIONS
SAVE THESE INSTRUCTIONS
This manual contains important instructions for the Disconnect Unit for Sunny Central 250U /500U
/ 500HE-US/CA and Sunny Central CP accessory, that must be followed during installation and
maintenance of the accessory.
The Disconnect Unit for Sunny Central 250U /500U / 500HE-US/CA and Sunny Central CP are
designed and tested according to international safety requirements, but as with all electrical and
electronic equipment, certain precautions must be observed when installing and/or operating the
Disconnect Unit for Sunny Central 250U /500U / 500HE-US/CA and Sunny Central CP. To reduce
the risk of personal injury and to ensure the safe installation and operation of the Disconnect Unit for
Sunny Central 250U /500U / 500HE‑US and Sunny Central CP, you must carefully read and follow
all instructions, cautions and warnings in this installation guide.
Warnings in this document
A warning describes a hazard to equipment or personnel. It calls attention to a procedure or practice,
which, if not correctly performed or adhered to, could result in damage to or destruction of part or all
of the SMA equipment and/or other equipment connected to the SMA equipment or personal injury.
%"/(&3
DANGER indicates a hazardous situation which, if not avoided, will result in death or serious injury.
8"3/*/(
WARNING indicates a hazardous situation which, if not avoided, could result in death or serious
injury.
$"65*0/
CAUTION indicates a hazardous situation which, if not avoided, could result in minor or moderate
injury.
/05*$&
NOTICE is used to address practices not related to personal injury.

SMA America, LLC 
Installation Guide DisconACDC_SCUS-IUS103110 5
Other symbols in this document
In addition to the safety and hazard symbols described on the previous pages, the following symbol
is also used in this installation guide:
Markings on this product
The following symbols are used as product markings with the following meanings.
Information
This symbol accompanies notes that call attention to supplementary information that you must
know and use to ensure optimal operation of the system.
Warning regarding dangerous voltage
The product works with high voltages. All work on the product must only be
performed as described in it‘s documentation.
Electric arc hazards
The product has large electrical potential differences between its conductors. Arc
flashes can occur through air when high-voltage current flows. Do not work on the
product during operation.
Beware of hot surface
The product can become hot during operation. Do not touch the product during
operation.
Observe the operating instructions
Read the documentation of the product before performing any work. Follow all safety
precautions and instructions as described in the documentation.
UL1741 is the standard applied by Underwriters Laboratories to the AC/DC-
Disconnect Unit for Sunny Central 250U /500U / 500HE-US/CA to certify that it
meets the requirements of the National Electrical Code®, the Canadian Electrical
Code® CSA C22.1 and IEEE‑929‑2000. IEEE 929-2000 provides recommendations
regarding the proper equipment and functionality necessary to ensure compatible
operation when power generation is connected to the utility grid.

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6 DisconACDC_SCUS-IUS103110 Installation Guide
General warnings
8"3/*/(
All electrical installations must be done in accordance with the local codes and National Electrical
Code® ANSI/NFPA 70 or the Canadian Electrical Code® CSAC22.1.
Before installing or using the Disconnect Unit for Sunny Central 250U /500U / 500HE-US/CA
and Sunny Central CP, read all of the instructions, cautions, and warnings on the AC/DC-Disconnect
Unit for Sunny Central 250U /500U / 500HE-US/CA and Sunny Central CP in this installation
guide.
Before connecting the Disconnect Unit for Sunny Central 250U /500U / 500HE-US/CA and
Sunny Central CP to the power distribution grid, contact the local power distribution grid company.
This connection must be made only by qualified personnel.
Wiring of the Disconnect Unit for Sunny Central 250U /500U / 500HE-US/CA and Sunny Central
CP must be made by qualified personnel only.

SMA America, LLC Table of Contents
Installation Guide DisconACDC_SCUS-IUS103110 7
Table of Contents
1 Notes on this manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.1 Target group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.2 Validity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.3 Nomenclature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.4 Differences between variants of the Disconnect Unit . . . . . . . . 11
2 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1 Appropriate usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2 Safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3 The Disconnect Unit for Sunny Central . . . . . . . . . . . . . . . 15
3.1 Operating principles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.2 Identifying the Disconnect Unit . . . . . . . . . . . . . . . . . . . . . . . . . 15
4 Scope of delivery and storage . . . . . . . . . . . . . . . . . . . . . 16
4.1 Unpacking and inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.2 Scope of delivery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.3 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5 Installation of the Disconnect Unit . . . . . . . . . . . . . . . . . . 18
5.1 Choosing the installation site . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.1.1 Ambient conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.1.2 Characteristics of the base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.1.3 Position of the mounting holes and bottom entry sleeves . . . . . . . . . . . . . . . 19
5.1.4 Minimum clearances. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5.1.5 Dimensions and weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.2 Installing the Disconnect Unit onto the base . . . . . . . . . . . . . . . 24
5.3 Opening the Disconnect Unit . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.4 Preparation of the cable entries . . . . . . . . . . . . . . . . . . . . . . . . 27
5.5 Inserting cables into the Disconnect Unit. . . . . . . . . . . . . . . . . . 29

Table of Contents SMA America, LLC
8 DisconACDC_SCUS-IUS103110 Installation Guide
6 Electrical connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
6.1 Overview electrical connections . . . . . . . . . . . . . . . . . . . . . . . . 30
6.1.1 Disconnect Unit for Sunny Central 250U/500U . . . . . . . . . . . . . . . . . . . . . 30
6.1.2 Disconnect Unit for Sunny Central 500HE-US/CA and SunnyCentralCP. . 31
6.2 Cable requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
6.2.1 Cable requirements for DC, AC and PE connection . . . . . . . . . . . . . . . . . . . 32
6.2.2 Additional cable requirements for DC connection . . . . . . . . . . . . . . . . . . . . 32
6.3 Connecting DC cables to the Disconnect Unit . . . . . . . . . . . . . 33
6.3.1 Connection sequence DC switches 600V . . . . . . . . . . . . . . . . . . . . . . . . . . 33
6.3.2 Connecting DC cables to DC load break switch with screw terminals . . . . . 34
6.3.3 Connecting DC cables to DC load break switch with cable lugs . . . . . . . . . 36
6.3.4 Connecting sequence for single DC load break switch, 600V . . . . . . . . . . 38
6.3.5 Connecting sequence for single DC load break switch, 1,000V. . . . . . . . . 39
6.4 Connecting AC cables to the Disconnect Unit . . . . . . . . . . . . . 40
6.4.1 Additional cable requirements for AC connection . . . . . . . . . . . . . . . . . . . . 40
6.4.2 Arranging AC cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
6.4.3 Overview AC connection to power distribution grid. . . . . . . . . . . . . . . . . . . 42
6.4.4 Overview AC connection to the inverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
6.4.5 Connecting AC cables to busbars. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
6.5 Connecting protective earth . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
6.5.1 Additional cable requirements for PE connection . . . . . . . . . . . . . . . . . . . . . 53
6.5.2 Connecting protective earth to busbar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
6.6 Closing the Disconnect Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
6.7 Affixing information about grounded path . . . . . . . . . . . . . . . . 58
7 Operating the Disconnect Unit . . . . . . . . . . . . . . . . . . . . . 60
7.1 Arrangement of the switches. . . . . . . . . . . . . . . . . . . . . . . . . . . 60
7.2 Switching on the Disconnect Unit . . . . . . . . . . . . . . . . . . . . . . . 61
7.3 Switching off the Disconnect Unit . . . . . . . . . . . . . . . . . . . . . . . 62
7.4 Securing against reconnection – Lock-Off function. . . . . . . . . . 63
8 Technical data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

SMA America, LLC Table of Contents
Installation Guide DisconACDC_SCUS-IUS103110 9
8.1 Disconnect Unit for Sunny Central 250U/500U . . . . . . . . . . . 65
8.2 Disconnect Unit for Sunny Central 500HE-US/CA. . . . . . . . . . 66
8.3 Disconnect Unit for Sunny Central CP. . . . . . . . . . . . . . . . . . . . 67
9 Contact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

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10 DisconACDC_SCUS-IUS103110 Installation Guide

SMA America, LLC 1 Notes on this manual
Installation Guide DisconACDC_SCUS-IUS103110 11
1 Notes on this manual
This manual describes the installation and the commissioning of the Disconnect Unit for Sunny Central
250U /500U / 500HE-US/CA and Sunny Central CP. This manual does not cover any details
concerning PV modules. Information concerning the PV modules is available from the manufacturer of
the PV modules.
You can install the Disconnect Unit both right and left from the Sunny Central. All instructions in this
manual are explained for a right system. That means, that the Disconnect Unit will be installed on the
right side of the Sunny Central. A right system is recommended by SMA due to much shorter cable
lengths. If an installation of the Disconnect Unit is required on a left system, observe that all
connections are arranged opposite and that all instructions are carried out accordingly.
Keep this manual in a convenient place for future reference.
1.1 Target group
This manual is for qualified personnel only. Qualified personnel have received training and have
demonstrated skills and knowledge in the construction and operation of the device. Qualified
personnel are trained to deal with the dangers and hazards involved in installing electric devices.
1.2 Validity
This manual is valid for the Disconnect Unit for Sunny Central 250U /500U / 500HE-US/CA and
Sunny Central CP.
1.3 Nomenclature
In this technical writing the SunnyCentral250U/500U/500HE-US/CA and Sunny Central CP are
referred to as ”Sunny Central”.
In this technical writing the Disconnect Unit for Sunny Central 250U /500U / 500HE-US/CA and
Sunny Central CP is referred to as ”Disconnect Unit”.
In this technical writing SMA America Production, LLC and SMA Solar Technology Canada Inc. are
referred to in the following as SMA.
1.4 Differences between variants of the Disconnect Unit
The dimensions of the Disconnect Unit are adopted to the specific inverter. A Disconnect Unit for the
Sunny Central 250U/500U has a lower height than the Disconnect Unit for the Sunny Central
500HE-US/CA and for Sunny Central CP. Furthermore, you can order the Disconnect Unit in different
technical variants. These differences between the variants of the Disconnect Unit are described
explicitly in the relevant technical writing chapters.

2 Safety SMA America, LLC
12 DisconACDC_SCUS-IUS103110 Installation Guide
2 Safety
This section describes general safety regulations which must be observed throughout the entire
installation process. Pay attention to this section to avoid personal injury and material damages.
2.1 Appropriate usage
The Disconnect Unit for Sunny Central inverter is a AC/DC disconnect that extends the range of
functions of the inverter. You can use the Disconnect Unit to disconnect the inverter from PV modules
and from the power distribution grid as requested by the National Electrical Code® ANSI/NFPA 70.
Principle of a PV plant with a inverter with Disconnect UnitPrinciple of a PV plant with a inverter with Disconnect Unit
Figure1:Principle of a PV plant with a inverter with Disconnect Unit
Any other application of the inverter, of the Disconnect Unit or installation of components and
modifications which are not allowed explicitly endanger the safety and void the warranty as well as
the operation permit.
• It is prohibited to use the inverter and the Disconnect Unit for purposes other than those
described here.
• It is prohibited to modify the inverter or the Disconnect Unit or to install components that are not
explicitly recommended or sold by SMA.
Position Description
APV modules
BDC distribution with DC fuses (e.g., Sunny Central String-Monitor)
CSunny Central
DDisconnect Unit
ETransformer
FPower distribution grid

SMA America, LLC 2 Safety
Installation Guide DisconACDC_SCUS-IUS103110 13
• It is prohibited to connect the Sunny Central 500HE-US/CA or Sunny Central CP without
transformer to the grid. Operating the inverter without transformer causes a short-circuit and can
destroy the inverter.
2.2 Safety instructions
%"/(&3
High voltages are present in the live components of the low-voltage grid.
Death from burning and electric shock will result.
• Do not touch the live components of the inverter or of the Disconnect Unit or low-voltage grid.
• Pay close attention to all safety precaution measures regarding the low-voltage grid.
%"/(&3
During operation, high voltages are present in the inverter and in the Disconnect Unit.
Death resulting from electric shock will result.
• If the Disconnect Unit has got doors: Do not operate the inverter and the Disconnect Unit with
doors open.
Before commencing work on the inverter and the Disconnect Unit:
• Disconnect completely.
• Ensure that the device cannot be reconnected.
•Ensure that no voltage is present.
• Ground and short-circuit.
• Cover any nearby live parts.
%"/(&3
Normally grounded conductors may be ungrounded and energized when a ground-fault is
indicated by the inverter.
Risk of electric shock.
•Test before touching.
• Work on the inverter and on the Disconnect Unit must be carried out by qualified personnel.

2 Safety SMA America, LLC
14 DisconACDC_SCUS-IUS103110 Installation Guide
8"3/*/(
Failure to follow the manual, the operating instructions and the safety precautions may lead to
severe injury from electric shock.
• All work on the inverter and on the Disconnect Unit must be done as described in this manual.
• Pay attention to all safety instructions.
• Follow all operating instructions.
• If problems occur when performing the work described here, contact SMA.
8"3/*/(
Operating a damaged inverter or Disconnect Unit can cause severe injury from electric shock.
• The inverter and the Disconnect Unit must only be used when it is technically faultless and safe
to operate.
• Do not operate the inverter or the Disconnect Unit if there are visible damages.
• Check the inverter and the Disconnect Unit on a regular basis for visible damage.
• Ensure that all safety features are accessible at all times and that their correct operation is
tested regularly.
$"65*0/
Cuts and scratches due to sharp edges inside the inverter and inside the Disconnect Unit can result.
• Wear protective gloves when working on the inverter and the Disconnect Unit.
/05*$&
The components in the inverter and in the Disconnect Unit can be damaged by electrostatic
discharge.
• Observe all ESD safety regulations when working on and when handling the components of
the inverter and the Disconnect Unit.
• Discharge electrostatic charge by touching the grounded inverter enclosure.
• Only then it is safe to touch any electronic components.
Storage of technical writing
Keep this installation guide in the immediate vicinity of the Disconnect Unit. It must be accessible
to service and maintenance personnel at any time.
Do not store the installation guide or any other papers in the inverter or in the Disconnect Unit.

SMA America, LLC 3 The Disconnect Unit for Sunny Central
Installation Guide DisconACDC_SCUS-IUS103110 15
3 The Disconnect Unit for Sunny Central
3.1 Operating principles
The PV modules convert a portion of sunlight into electrical energy (direct current). The inverter then
converts the direct current into alternating current and feeds it into the power distribution grid. This
current can be used directly, or it can be sold to your energy provider. The Disconnect Unit is for
disconnecting the inverter from the PV modules and from the power distribution grid for service and
maintenance issues and in case of emergency as demanded by National Electrical Code® 2008.
3.2 Identifying the Disconnect Unit
You can identify the Disconnect Unit by its type label. The type label is located at the top right of the
rear wall.
Figure2:Type label Disconnect Unit
www.SMA-America.com
DISCONNECT-UNIT
Engineered in Germany - Assembled in Denver/Colorado
Model: Serial No.:
DC-SC-US xxxxxxxxxx
Fabrication Version
xx/xxxx
Allowed Inverter Type xxxxxxx - xx/xx
DC Rating:
Maximum Array system voltage xxx Vdc
Maximum operating current xxxx Adc
AC Ratings:
Operating voltage range
(Vac 3-Phase)
Min. xxx
Nominal xxx
Max. xxx
Max. continous output current xxxx Aac
Operating frequency range
(Hz)
Min. xx.x
Nominal xxx
Max. xx.x
For more electrical ratings see in the
Inverter manual.
Other Ratings*
Operating temperature range (-25 °F ... +50 °C)
Maximum Air ambient
without De-Ratings (°C) 50 °C
ENCLOSURE Type 3R (IP54)
* For more details and tightening torqe, allowable wire size
and type see Disconnect unit Operators‘s manual.
Listet Accessory Photovoltaik / AC Grid Disconnect
US80
Date of manufacture
Max. continous output Power xxxx kWac

4 Scope of delivery and storage SMA America, LLC
16 DisconACDC_SCUS-IUS103110 Installation Guide
4 Scope of delivery and storage
4.1 Unpacking and inspection
All Disconnect Units are thoroughly checked before they are packaged and shipped. Although they
are shipped in sturdy packaging, damage can still occur during shipping and delivery.
• It is important to carefully inspect the shipping container and contents prior to installation.
• If you detect any external damage after unpacking, report the damage immediately to your
SMA dealer and shipping company that delivered the unit.
• If it becomes necessary to return the Disconnect Unit, use the original packing material.
• For further details about unpacking and transport of the Disconnect Unit see the technical
description ”Unpacking AC/DC Disconnect Unit for Sunny Central 250U /500U / 500HE-
US/CA and Sunny Central CP“.
• If you need assistance with a damaged Disconnect Unit, contact your dealer or SMA (see
chapter 9”Contact”,page69).
4.2 Scope of delivery
Figure3:Scope of delivery Disconnect Unit
Position Quantity Description
A1 Disconnect Unit for Sunny Central
B1 Installation guide
C1 TX 25 screw driver
D1 TX 30 screw driver
E18*
*optional
Screw terminals for AC connections
F18*Screw terminals for DC connections
G2*Screw terminals for PE connection
H1 Ground strap
I1 Label

SMA America, LLC 4 Scope of delivery and storage
Installation Guide DisconACDC_SCUS-IUS103110 17
4.3 Storage
/05*$&
Improper storage can cause moisture to seep into the Disconnect Unit.
Damage to the Disconnect Unit will result.
• The Disconnect Unit must be closed during storage.
• If stored for 6 months or longer, make sure the storage area is dry.
/05*$&
Uneven underground can damage the frame construction.
• The underground must be suitable for the weight of the disconnect of approximately
1,325lbs. (600kg).
• The underground may only deviate from a level of 0.25 %.
• Storage temperature: ‒40°F…140°F (‒40°C…60°C).

5 Installation of the Disconnect Unit SMA America, LLC
18 DisconACDC_SCUS-IUS103110 Installation Guide
5 Installation of the Disconnect Unit
5.1 Choosing the installation site
5.1.1 Ambient conditions
☐ The installation location must be accessible at all times.
☐ Ambient temperature: ‒13°F…+122°F (‒25°C…+50°C).
☐ Humidity 15%…95%.
☐ The Disconnect Unit is not protected from salt fog pariculars, it can not be operated in
chemically aggressive environments. Operate the Disconnect Unit in a minimal distance of
19miles (30km) from sea.
For more information, see section 8”Technical data”,page65.
5.1.2 Characteristics of the base
☐ The mounting surface is leveled and strong enough to support the weight of the Disconnect Unit.
The evenness of the foundation must be less than 0.25 % (1in. per 35⁄16ft.).
☐ The width and depth of the base is at least the same size as the Disconnect Unit including
mounting anchors.
Figure4:Dimension Base for Disconnect Unit

SMA America, LLC 5 Installation of the Disconnect Unit
Installation Guide DisconACDC_SCUS-IUS103110 19
5.1.3 Position of the mounting holes and bottom entry sleeves
Figure5:Position mounting holes

5 Installation of the Disconnect Unit SMA America, LLC
20 DisconACDC_SCUS-IUS103110 Installation Guide
5.1.4 Minimum clearances
Figure6:Minimum clearance between inverter and Disconnect Unit side-by-side
The minimum clearance between Sunny Central and Disconnect Unit side-by-side is required for
bending radii for inserting cables through side-entry (see section 5.4 and section 5.5). Minimum
clearance can be reduced down to 3in. (75mm) by inserting the cables through bottom entry.
Figure7:Minimum clearance between inverter and Disconnect Unit face-to-face
The minimum between Sunny Central and Disconnect Unit face-to-face has to be 4ft. (1,220mm) if
one cabin shall be opened at the same time. Refer to National Electrical Code® ANSI/NFPA 70 for
detailed information about the requirements.
/05*$&
Increased clearance
The clearance has to be raised if both cabinets shall be opened at the same time. Refer to National
Electrical Code® ANSI/NFPA 70 for detailed requirements.