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12.1 Cabling 101

12.1.1 Introduction

The intent of this writing is not to make you an expert in cabling. The intent is to provide you with the necessary reference information, tips, and recommendations for you to wisely use cabling. There is no, substitute for hands on experience with cabling.

Please carefully read all of this information before you attempt your cabling efforts. Experience is a great teacher, so don’t be afraid or discouraged if you mix up wiring patterns or do not suitably terminate a connection with the proper amount of pressure on a wire connector as you begin your cabling efforts.

12.1.2 Cable

A wire is a single conductor. A cable is a group of two or more insulated conductors. Category 5 cable is available in many forms. The cable is solid core 24-AWG. 8 separately jacketed wires, twisted in pairs, making 4 pairs all contained within a protective jacket. The jacket wrapping around the cable is either Plenum or Non-Plenum. Plenum cable is rated for a fire hazard area. Category 5 cabling is often rated as low-voltage, meaning you do not need a license to install the cable. Please contact your local fire authority for more information.

12.1.3 Grounding

Proper cable grounding is essential for safety. The assumption the cable carries a low amount of voltage is true, but it also carries enough capability to damage the equipment connected together via your cable and you.....the cabling person. The differences between surge-suppression and transient-voltage-suppression cannot be stated enough. Please contact your local fire authority for more information.

12.1.4 Installation

Category 5 cable is installed in either electrical conduit, cable trays, or J-Hooks. Cable must, must, must be properly supported to prevent stretching the copper wire and cause small breaks in the wire. Small wire breaks cause for performance issues in quality-of-service, and lead to a complete breakage in one or more wires. Cable is laid out in a pattern of either a main distribution frame or an intermediate distribution frame.

12.1.5 Termination

Properly installed cable is then connected with some type of registered jack -and- plug. This end result is called a cable termination or a wire termination.

12.1.6 Testing

All cabling must have continuity all of the time. A simple cable tester is probably the most manageable continuity tester there is after cable has been terminated with a registered jack and plug to determine if you have continuity. If you have nothing else to test with, connecting two bare wires together with a wire nut on one end, then testing the other ends with a multi-meter is always an option. This is quite valuable after cable has been laid in place and you want to know if it has continuity before terminating the cable.

12.1.7 Usage Notes

12.1.8 Cautionary

Whatever you do, always install your cable as required by your fire authority and always, always, always properly support your cable with either electrical conduit, cable trays, or J-Hooks. Suffice it to say, cable that is not properly supported will eventually have small cracks in the wire, resulting in a quality-of-service loss, progressing to intermittent continuity problems, and ultimately completely break the wire somewhere within the cable jacket.

12.2 Power over Ethernet (PoE) 101

12.2.1 Introduction

Power over Ethernet is quite possibly the best thing to come along to the Information Technology world of hardware since the 1980’s. Literally, it is that wonderful! The essence of PoE is you can use cable that is rated as low-voltage to power a multitude of PoE hardware devices. The list of what is capable of PoE is constantly growing. Here are some common PoE terms to understand.

12.2.2 Power Sourcing Equipment (PSE)

The PSE is the network PoE element that inserts power onto a Category 5 cable. It may be an endspan device, such as a PoE-enabled data network switch, or a midspan device located between the data network switch and the Powered Device (PD).

12.2.3 Powered Device (PD)

A PD is the PoE capable device that receives power over Category 5 cable. It could be a PoE-enabled IP telephone, a Wireless Access Point, an IP enabled HVAC thermostat, any other IP device that needs electrical power.

12.2.4 Midspan

A midspan device is a PSE that inserts power onto the Category 5 cable. It is situated between the data network switch and the PD. Typically, midspan devices are added to existing networks to allow the use of PoE-enabled PD’s.

12.2.5 Endspan

An endspan device is typically a data network switch that incorporates PoE capabilities. Endspan devices often are implemented when a new network is created, to avoid adding both midspan devices and a data network switch.

12.2.6 Usage Notes

Now, should you need or want to move a device such as a Wireless Access Point, an IP telephone, or an HVAC sensor to another location.....imagine how nice it would be to not have to juggle the powering of that device. There are many combination options available for PoE capable hardware.

Pressing onward, imagine a device is locked up and you need to power the device off and then turn it back on. Walking to that device could be a hassle, and could require opening a lot of access panels. Using PoE, you can turn off the power over your data network and then turn it back on.

The thing for you with PoE is you need to determine how much electrical power you need. This amount will tell you what specification you need to comply with. The manufacturer of the PoE device will tell you what standards they are compatible with. From there, buy the PoE supply. Your selection is either a simple single-port power injector (Midspan), or a rack-mounted midspan power injector, or buy new data network switches that have PoE built-in as an integrated feature (Endspan). Count the cost and choose as best suits you.

The biggest benefit of PoE is you have the ability to have a better handle on your surge-suppression and transient-voltage-suppression efforts. This is because you so chose to install your cabling as recommended. Running a wire as an extension off of an HVAC unit, or a wall outlet, to supply electricity to power the PoE capable hardware, without also providing proper protection for that PoE hardware, is absolutely and positively nothing but trouble. That trouble often shows up as electrical damage in the form of peculiar performance of the hardware, or even hardware failure.

12.2.7 Cautionary

Here is a strong and simple example of why powering your IP enabled thermostat device from an HVAC unit is a bad idea.

The drain line on the HVAC unit somehow gets blocked. This triggers the float switch to prevent flooding and that powers down the whole system. The thermostat has then been turned off due to the absence of power to the thermostat. The same is true if you power your IP enabled thermostat device from your HVAC and not PoE. That means you will be unable to access your IP enabled thermostat device from your data network.

You can also hook your float switch to your IP enabled thermostat device, as an external information sensor, and know when that float switch is activated via Remote Monitoring. Power over Ethernet is a really.....really.....good idea.

Whatever you do, always use cable safely. Please contact your local fire authority for more information.

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