Replacement Of A Dying Legacy RTU

If your network has been around for a while, eventually you will be faced with the decision to either upgrade your current equipment, or continue to patch the network to maintain monitoring operations while the budget is getting worked out by the accounting department. While almost all of us would love to simply upgrade the existing equipment with one swipe of the pen, rarely does that happen.

So, how do you go about intelligently planning an upgrade to existing networks to ensure compatibility and operability during a multi-year (or staged) deployment? Do you replace the master station first, and if so, how do you handle legacy protocols? Or, do you replace the RTUs first and then tackle the master station? Your current system uses legacy transport (for example, RS 232 serial connections, or 202 modems, legacy protocols, etc.) and you want to move to a LAN based solution with SNMP.

For the sake of this white paper, we'll explore replacing the field units first, then have a look at the master station.

So, what about those remote sites?
The remote sites typically have a variety of conditions to monitor, and vary in scope and needs. Preparing to replace existing RTUs takes a bit of planning, so you can maximize the money you invest to get the best utilization now, and the best opportunity for growth and flexibility moving forward.

In order to properly plan this, we will look at how many discrete (on/off, learn more) inputs, how many control relays (contacts that can trigger power to other devices to turn their on or off, learn more), and how many analog inputs (inputs to the RTU that can measure variations in voltage or current from a sensor, learn more) we will need to replace our old unit with a new one. We also want the ability to utilize IP based technology to properly expand with the current upgrades in our network. This will involve a change from our older communications protocol (RS-232 serial communications) to a LAN based SNMP protocol as we build out with new equipment.

This will be an important part to upgrading in the system, as the new master station we plan to install has the ability to connect to field RTUs with either RS 232 or LAN. The solution we choose must maintain capacity and work with our existing master station where necessary, and also allow for expansion and growth for future upgrades. Let's have a look at a typical scenario.

Your typical remote site, with a sad, old RTU
So there it sits, miles from your closest technician's home base, and it is in need of some attention. This site is set up to monitor a communications tower, and has a number of devices connected to your 12 year old RTU which is beginning to show some real wear and tear. It unfortunately does not have all of the monitoring you would like; it's missing some features. Currently you can only monitor 12 discrete contacts and no analogs. You only have 2 controls on the unit, one for HVAC and the other for the generator. You would like to add controls for room lights, and door lock/unlock, but you don't have the capacity with your current RTU.

Looking around the location, let's have a look at what's being monitored, and what it would take to replace the poor old RTU workhorse with something that meets our upgrade requirements. The generator is a key component of this location. Currently you can only monitor when it is running (it's operational state: on or off- a "discrete" or "dry contact" type input) and you have the ability to turn the generator on or off when necessary (a "control" relay). ). You would really like the ability to know that it is operating normally and within voltage range (an analog reporting input), but your current old RTU only reports discrete connections, not analogs. So monitoring the basic functions of the generator would need 1 control, 1 discrete and 1 analog input on the RTU for better visibility at the site.

Fuel for the generator also needs monitoring. Currently you have a route technician that checks fuel levels 2 times per month. That has left you a bit close on a couple of occasions and you would really like to monitor fuel levels with more consistency. Knowing your fuel levels saves you time, truck fuel, and wear and tear on your fuel trucks. If you have not had a generator run in 2 weeks and the fuel levels are reporting in good shape, you can save a truck roll - and that adds right to the bottom line. Add another analog input for fuel level to add to our list of "wants" for the new upgraded RTU.

There is a network switch at the location that can report back to you various operational conditions such as high traffic conditions, hardware failure and voltage out of range, but unfortunately, there is not enough capacity on your current RTU to monitor the switch, so that needs to be planned into the upgrade.

There is an HVAC unit at the site, and you can turn the unit on and off with the remaining control on your system, and you can monitor if it is operating with your remaining dry contact. But, you do not have the capacity on your current RTU to monitor temperature or Humidity at the site, and this is a big problem for you.

There is various revenue generating equipment at the site that could fill 12 of the dry contact inputs on your remote RTU, but you only have 10 inputs remaining after connecting up your HVAC and Generator to the unit. As you look toward the future, it sure would be nice to have some extra room for expansion, as well as for all the connections you already have but can't accommodate.

Finally, this unit reports back to the CO via RS 232 and is not compatible with the LAN requirements you plan into your system. But, you are not wired yet for LAN at this location, and it may be quite some time before you will have LAN at this location. You will need to maintain compatibility with existing protocols over RS 232 at this site before you can migrate to LAN, but you want to be able to make this transition easily when the time comes.

So, looking at your site, the current monitoring system can only report 12 discrete contacts and 2 controls. You want to maintain these, and add enough additional monitoring for fuel, your network switch, and temperature and humidity, and still leave room for additional growth as needed.

Also consider that this location is very similar to the other 50 locations you will be upgrading as part of your multiyear upgrade plan. You want compatibility, longevity and consistency over your migration, so this becomes a uniform and cohesive system when it is completed.

So, looking at the site requirements, you'd like an RTU that has more than 12 discretes, more than 2 controls for growth opportunities, and at least 2 analog inputs- more would be better for flexibility and growth. An example of this kind of RTU would be the NetGuardian V16-G2. It has 16 discrete inputs, 4 analogs and anywhere from 2 to 18 controls depending on the specific build. It has an RS 232 port for existing communications, and has a 10/100 LAN connection as well for when the time comes for the LAN upgrade.

That Tired Old Master Station isn't what it used to be
At one point, it was a great system, worked well, and has proven its worth.

That was 15 years ago, and now it has seen a couple of modem replacements, parts are scarce, and it only understands the language of an older, less flexible protocol. Due to the advancement of technology, and the advantages of SNMP monitoring, you want to upgrade the master and still be able to communicate with the legacy equipment in the field.

The key is to focus on a master station that is flexible enough to handle multiple legacy protocols. The advantage here is it gives you the best opportunity to upgrade your system over time. Since, in this example, your current RTUs report back to the CO via RS 232, you will need a master station that can accept both serial communications via RS 232 and provide future network modernization using LAN reporting. Replacing your master station with one that fits these criteria allows you to effectively tie together your current operation and set a solid foundation for your next generation monitoring system as budget allows. The criteria for a master station will vary according your network, but in our example here, a network with approximately 50 monitoring sites, a master station like a TMon Slim would fit the need, and allow for legacy communication protocols.

Planning an upgrade can be challenging, but with the proper tools we can make it easier. A good telemetry monitoring sales engineer can help blend the individual needs of growth and migration into a cohesive and well thought out plan of action utilizing the best of both new and legacy equipment. The link below to our network upgrade planner can be a big help in identifying your current situation, and the potential growth plan for your next gen network. Consider talking to our friendly and knowledgeable engineers to answer your questions as you replace your current systems.