In Part 1 of this series the emphasis was on being prepared for the beginning of Systems Test and Integration Procedures (STIP). The synopsis for being prepared is having complete, accurate and appropriate documentation for the task and to have the proper test equipment.
Part 2 of the 5 part series describes the establishment of procedures for testing cables after they are installed. This article will guide you in preparing for and completing procedures that will systematically and methodically take you through a sequence of tasks purposed to insure the integrity of the wiring prior to a complete systems test and integration process. Testing procedures will vary according to the type of wiring and equipment being installed and should also be designed in accordance with the specific industry you serve.
They may also reflect your company’s particular organization and management style. However, care should be taken in establishing the procedures that are not only best for your specific organization but serve the main intent and objectives if they are to be adequately effective. In formulating you test plans there could be a tendency to take shortcuts or what may be perceived as cost saving measures. However, these generally have just the opposite affect so do not be fooled by what might seem to you as a cost saving measure. There are no such shortcuts to a well established and effective plan. Just make sure there is no duplication of testing and that all testing being conducted in the proper procedure and most efficient way possible to keep the costs proportional to the results you are trying to achieve.
The primary objective for cable and test and verification procedures is to test all wiring after it has been installed and prior any termination task to assure the integrity of the wiring that proper system functioning depends upon. A major objective is discovering cabling that has been damaged during installation, incorrectly installed or not installed as soon as possible during construction. Otherwise, it becomes more difficult and costly to correct later and to prevent fault compounding.
Cable test and verification procedures performed prior to any terminations is a low level test, meaning that it can be performed with simple test instruments, although specialized test equipment or analyzers can be used to perform the same function while offering extended capability. Most installers, properly trained and skilled, can accomplish this level of testing without difficulty. Each installation team should have at least one installer qualified for administering and supervising the tests to insure a good outcome.
Pre-wire or Not
Not all installation projects have a pre-wire phase. Generally speaking, a pre-wire phase is part of a project when it is necessary during construction of any facility to install cabling after framing has been installed but prior to the time when the construction process installs the walls of the facility. This is common among homes where the cables are run through the framing of a home without the use of conduit to facilitate cabling. Pulling wire through conduit is generally the standard practice for commercial installations and may be required according to applicable codes. Furthermore, long runs often encountered in commercial installations would be more difficult to pull cables without it and there would be a higher risk of cable damage without the protection of conduit.
This is not to assume there is no conduit installed for low voltage wiring in a home. Sometimes there is at least for some. For example, low voltage wiring installed throughout a home for room-to-room wiring may be installed in the wood framing but wiring that needs to be run to the outside of the home to speakers, video monitors, control system or a access gate where it needs the protection of conduit and often time has to be run underground where it needs protection from the elements unless cable design for direct burial. It might also have conduit installed for cabling to the demarcation points for connection to service provides such as telco lines or antenna to a head-in racks.
If there is no pre-wiring phase, then the procedures for pre-wire checks are not applicable or needed. Since pre-wire occurs after the framing of the structure is completed but before walls are constructed, timing is very critical since the window of opportunity is relatively small. Characteristic of projects that require a Pre-wire phase, there will normally be a discrete end of the pre-wire and the beginning of terminations, although the time between the end of pre-wire and the beginning of termination tasks can vary considerably with each project. For this reason, project management needs to be acutely aware of this to insure that the tests are conducted at the most appropriate time during the construction and installation phases. Poor project management can be very costly to the project so this should be a major concern that is just as important as the procedures themselves.
Before conducting any tests it is extremely important that you have the proper documentation and test equipment required to assure a quality outcome. This was discussed in detail in Part 1 of this series. As each task is specified and described in these articles, there will be a discussion of the documentation and test equipment required for each task.
Some test equipment can be configured to test cables efficiently with only one person. In other cases two people working together can be more efficient and other tasks such as troubleshooting hardware/software becomes much for efficient. For troubleshooting systems, having a way for the two to communicate, especially with a hands free ear/boom arrangement, is critical for maximum efficiency. Without the right communications equipment, efficiency of a two-man crew is significantly reduced and not recommended. The cost for this type of equipment today is minimal and the advantage is significant.
Section 1: Pre-wire Phase
The following procedures under Section 1 pertain only to installations that have a pre-wire phase and should be conducted immediately after its conclusion, although the procedures can begin on cable installed as the pre-wire phase is near completion. The timeframe to conduct these procedures is critical. Cables that are run within the building structure without conduit are closed off once walls and other construction is been completed.
The importance of documentation was emphasized in Part 1. In order to properly conduct Pre-wire testing procedures you need to have documents such as room schedules and most importantly the master wiring list. This allows you to determine if all the cables required have been installed and installed correctly. The documentation should also defined the location and elevation of wall plates for connections and control.
Procedures conducted at the conclusion of the Pre-wire phase is a visual inspection only; no electrical testing, as required for Cable Test and Verification or Certification, will be required for this phase. Visual inspections are intended to ensure the integrity of the cable installed and to affirm that it has not been damaged during installation. Since cabling installed in pre-wire is open within the structures, it is possible to examine it for physical damage. Unless there is physical damage, it is very unlikely that cables need to have electrical testing.
Since cables installed in a Pre-wire phase are open it is possible that cables can be damaged by the other trades after they have been installed. However, this is usually rare if installers have installed the cables in a correct manor and taken proper procedures to protect them and correctly stowing the cable ends until the Termination phase.
The reference to Terminations refer to installing the wire to its destination at both ends by the use of terminals or connectors. Some industries such as home installation may refer to this phase as “Trim” that has been adapted from the construction industry. However, the electronics industry uses the term “Terminations” to refer to its function rather than a construction phase.
These procedures serve to verify that the type and quantity of cable from sources to it destination has been installed correctly according to room schedules, the master wiring list and other applicable project documentation. It also serves to assure the cables run to wall plates and control panels are in the correct location and elevation. Furthermore, it checks to make certain that all Pre-wire requirements of the DISP (Design and Installation Standards and Procedures) have been followed, including cable management, acceptable bend radius and cable support mechanisms. This is especially important for pre-wiring since the cables are not normally protected by conduit or raceways that are common in commercial installations. Some of the potential damages that can occur during pre-wire that must be discovered and corrected are as follows:
* A bend radius of a cable that exceeds the manufacture’s recommendation.
* Severe insulation or other cable damage caused by pulling cable past construction supports or other obstacles that cause physical damage to cables while being pulled without using proper cable supports and other devices designed prevent such damage during cable pulls.
* Staples or other installation devices used to secure cables to the structures that could have accidently pierced the cable.
* Improper type of staples being used to secure cables that do not prevent a cable from being “pinched” by a staple that deforms it to a point where its integrity and electrical characteristics have been compromised to the extend that the signal degraded.
* Nails, screws or other construction materials used by other trades that may have damaged cables after they have been installed.
* Determine that all federal and local applicable electrical and wiring codes and ordinances have been followed and free of violations.
Inspection procedures must be performed before walls or other construction hides the cables from visual inspection. It is unlikely that cables installed at this phase would be faulty if they pass these procedures. It is also important to note that corrective action taken at this stage of the installation project is much less costly than after major construction has been complete. Having to replace a cable that was installed at the wrong location, was the wrong type or one that has been damaged is much more difficult at later construction phases.
With this criteria and objectives in mind, you can then set out to write your own procedures that is best suited for your industry focus and your own ways of accomplishing them. If you have developed your own design and installation standards and procedures or you are using similar type procedures you have found to be acceptable to your operation to govern your installation, you should use it to also govern your post pre-wire cable testing and evaluation procedures.
It is important to have a master cable schedule with you that has a checkbox you can use to check-off wiring as each cable is completed. You can use one checkbox per cable to note its inspection is complete or you can have a separate for each type of check if you deem it best for our industry and type of installation. Whatever document form you use in these procedures, just make certain everything is checked and that you have documents that show the tasks have been performed for each cable installed. If you have a cable schedule that indicates the wire type, it also serves to help verify that the installers have used the correct cable type.
The follow is given as an example of typical Pre-wire phase test procedures that you can follow to derive your own. It is only a sample and it is not intended to be a complete example. The one you develop for your operation and industry should reflect the type of equipment and systems you install.
Typical Pre-wire Phase Cable Test Procedures
1.0 Visual Cable Inspection
1.1. Cables must follow a straight horizontal and vertical path (no angled runs or drops except where there is no alternative) and are properly segregated or bundled according to proper cable management (in accordance with your DISP).
1.2. Verify that no integrity compromising issues exists with the cables installed.
1.2.1. Cable bends that exceed recommended radian by the manufacture or other specifications (example: minimum of 4 times the cable diameter or 1 inch for Category 5 or 5e; 2-inch for RG-6 quad shield).
1.2.2. Any noticeable physical damage due to excessive tension during pulls; cut or crimped by screws, staples or other devices.
1.2.3. Cables run next to power lines or other cables that could result in signal interference (normal separation protocol specified in the DISP or other technical publications). Note any proximity issues and consult Engineering if there is suspicion.
1.2.4. Ensure that cable runs have been supported along their path with appropriate hardware at proper intervals.
1.3. Master Cable Schedule
1.3.1. Verify that each cable in the cable schedule has been installed at the correct source and destination location and make the following verifications.
220.127.116.11. Cabling is the correct cable type.
18.104.22.168. Proper pre-wire hardware installed (mounting plates, rough-in hardware, back cans, etc).
22.214.171.124. Cabling is secured and designated properly so construction trades do not cover up proper cable egress locations.
126.96.36.199. Cabling is cut to an appropriate length with sufficient service loop for making terminations.
188.8.131.52. Cabling is excess is properly stowed and protected from possible damage by other trades environmental conditions.
184.108.40.206. Cabling has been properly and securely identified with a number that correlates with cable schedule.
1.4. Electrical tests and verification for cables.
1.4.1. None required for this phase, unless stated otherwise for a specific project by Engineering. These tests, usually conducted at the termination phase, can be invoked at this time if circumstances warrant. However, the same tests will need to be performed again at the termination phase which duplicates the procedures and thus has a cost impact that needs to be considered.
Section 2 of Part 2 for Cable Test and Verification procedures for the Termination Phase will continue in the next publication.