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Troubleshooting web-based HVAC control system networks

November 2012

By Ron Auvil

Today’s HVAC technicians are expected to know a whole lot about everything. This includes refrigeration, heat transfer, mechanical and electrical systems, all the correct safety precautions, and much more. As the HVAC technician position continues to evolve, these folks are expected to know (you guessed it!) even more.

HVAC control systems in commercial buildings primarily consist of building automation systems. These microprocessor control systems are connected to the HVAC and energy-using equipment in the building. Building automation systems are web-based and communicate with personal computers over the building local area network (LAN). This means that critical system failures and downtime can be caused by network problems.

Traditionally, these networks have been maintained by the information technology (IT) staff. The IT staff, however, usually knows very little about the building automation system. When a network failure occurs, the usual reaction by the IT staff is, “It’s your building automation system device at fault.” Also, it is highly possible that IT staff may not be available to be onsite with an HVAC control technician when the work needs to be performed.

At the same time, HVAC control technicians may not have had much training or exposure to networking. Typically, vocational school programs focus on HVAC mechanical and electrical skills. Networking skills are not taught at all. This has created both a problem and an opportunity. The problem is often that HVAC control technicians may have a difficult time communicating with and working with building IT staff. This is a really BIG problem when a critical area such as an operating room or system such as a chiller plant is down.

With the increased prevalence of web access in buildings and the advent of web-enabled systems, the skills required of an HVAC technician are expanding more and more. Today, iPads, iPhones, and many other “smart” devices are being used to access numerous building systems, including HVAC, life safety, security, inventory, time/labor recording, parts inventory, and many others. These increased demands on the network require HVAC and other building technicians to have an increased base of knowledge in order to fix these systems and keep them operating smoothly.

Three real-life scenarios follow.

Scenario #1 - Web-based controller offline to network

A customer checks the web browser on a front end-computer and cannot see a remote building because the controller is offline. The customer calls a technician, who immediately attempts to use the “ping” command to see if the network will pass the command to the device. The ping command does not work, which means that the browser PC cannot reach the web-based controller.

The technician then tries to ping the router that the web-based controller is attached to. The ping command works. This means that the problem is probably not between the browser pc and the web-based controller; instead it’s between the web-based controller and router.

The technician goes to the remote building where the web-based controller is located and sees that there are no network activity lights blinking on the web-based controller. He plugs the Cat5 cable into a switch that he has in his bag. He cannot ping the router from the web-based controller, which again means the problem is between the router and the web-based controller. This could be a bad cable.

The technician connects his NetTool™ Series II Inline Network Tester to the Cat5 cable. The IntelliTone™ digital signaling system generates a signal. He can trace it using the signal detector provided with the meter.

The technician then goes to the IT closet where the Cat5 cables are connected to the router. He uses the signal detector inside a cable bundle and traces the correct cable. The sound produced by the signal detector suddenly ends at a particular spot. The technician cuts the wire ties that connect the cable bundle, to allow easy access to the bundle. He separates the bundle and traces the cable. Somehow the cable was damaged during a recent renovation. The cable is repaired, the network activity lights at the web-based controller are working normally, and the web-based controller comes back online.

Scenario #2 - Installing new web-based controller

A new web-based controller is being installed as part of a retrofit in an old courthouse. It is installed in the room housing the network and telephone equipment. The customer has been told the device will be up and running today, but unfortunately the IT people tell the HVAC control tech that they are busy on other calls and cannot come out to help today.

At this point the HVAC tech has to take the problem into his own hands. A large number of old unused Cat5 cables are installed in an old drop ceiling in the telephone/network room. The HVAC tech attaches his NetTool Series II Inline Network Tester to one Cat5 cable at a time. Most of the cables have been disconnected and are inactive. After he checks a number of cables, he finds one that is connected and has a valid network signal. He connects the NetTool Series II to the cable end and uses the IntelliTone digital signaling.

The technician then uses the signal detector at the router to identify the desired cable. The IP address of the cable is labeled at the router. He records the IP address and enters it into the software of the new web-based controller. The technician uses his laptop and network switch to verify web browser access locally, and then attaches the cable to the network for proper functionality by the customer browser computer.

Scenario #3 - Failure due to replacement router

A customer calls and reports that he cannot access a web-based controller and therefore cannot receive any alarms or respond to temperature complaints. The system worked properly until yesterday. The HVAC control tech records the IP address of the router and web-based controller as listed in the software. He uses the ping command to try to reach the web-based controller and the router with no success.

After a visit and discussions with the IT staff, it is finally discovered that some changes were made to the network yesterday. Unfortunately the IT person who did the work is out sick, so almost nothing is known about the changes made.

The HVAC tech attaches his NetTool Series II Inline Network Tester to the end of the Cat5 cable at the controller. Using the discover features of the diagnostic meter, he finds that a router with a new IP address has replaced the router as listed in the controller software. He records the new router IP and enters it at the web-based controller. The controller then comes online to the network and the customer can browse the system normally.

What’s the best way to handle these situations?

Because these scenarios are increasingly common, preparation is necessary. First, train the HVAC technicians in networking basics and second, provide them with effective tools to troubleshoot and diagnose commonly encountered network problems. Even though good diagnostic tools and training can be expensive, the expense is nothing compared to the cost of the equipment being down or not being able to use the rooms when needed.

The first part of the solution, training the HVAC technicians on networking basics, can be as simple as providing resources such as those available from Fluke Corporation, or perhaps by purchasing an entry-level networking book. A visit to the local bookstore will reveal a number of entry-level texts that will teach basic networking skills. Classes from community colleges are also available, with many of these today being online.

The second component of the solution is to provide HVAC technicians with the basic tools necessary to perform basic network troubleshooting functions. Fluke Corporation instruments are preferred by IT departments for quick, accurate location of problems. If these instruments are good enough for the IT department, are they not preferable for HVAC technician as well? While HVAC technicians may not need all of the features on every job, these features are available in the event they are needed.

The HVAC technician troubleshooting web-based building automation system controllers will face a number of problems that can easily be solved with the right training, basic networking skills, and a good Fluke meter such as the NetTool Series II Inline Network Tester. Some of the problems that can be diagnosed with this meter include tracing Cat5 cables, checking cable wiring, and checking cable ends.

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