Radio Communication Link Saves Money And Improves Pump And Water Tank Level Control

A Louisiana water system reaps immediate savings by replacing a hardwired phone connection with radio transmitter system for communication between two wells.
Radio Communication Link Saves Money And Improves Pump And Water Tank Level Control
A TeleSwitch (Ritron) receives and decodes the DTMF tones sent from an RQT unit and opens the appropriate relays to start or stop well pumps.

Interested in Instrumentation?

Get Instrumentation articles, news and videos right in your inbox! Sign up now.

Instrumentation + Get Alerts

The three most important factors in real estate are location, location and location. Apparently the same is true of telephone lines, based on the experience of the Sieper Area Water System (SAWS) in rural Rapides Parish, La.

The water system has two wells and a water tower to serve its 1,200 residents. The wells were connected to the water tower by a leased telephone line that carried the signal to activate and deactivate the pumps based on tank water level.

But since the line skirted two telephone exchanges, it cost about $250 per month. In September 2013, SAWS eliminated that cost by replacing the hardwired connection with a radio transmitter system. The savings on phone charges paid back the investment in one year.

Time for a change

In the SAWS network, Well No. 1 is next to the water tower, which is equipped with a float switch. When the water level drops below that switch, a contact closure turns that well pump on. At the same time, under the old system, a voltage change was sent along the telephone line to Well No. 2, about half a mile away, starting that well’s pump to help fill the tank.

When the water in the tank reaches an adequate level, another float switch signals a contact closure at the tank, turning off Well No. 1, and again a voltage change was passed along the phone line to shut off the Well No. 2 pump.

The equipment was robust and working well but was expensive to operate. In addition, the phone line was vulnerable to severe weather, such as ice storms and hurricanes.

Going wireless

In investigating wireless communication, SAWS leaders considered it prudent to keep as much of the existing system as possible, including the contact closures and float switches. One challenge was that the voltage change passed along the telephone line was at 48 volts, far above the 0-5 volts DC typically used for sensors and relays. SAWS chose to keep the high-voltage capability, as replacing it would add cost and complexity.

Now the signals to start and stop the well pumps are sent by a Ritron QuickTalk RQT, a 2-watt industrial-grade radio transmitter with switch inputs and voice storage capability. A high-voltage relay capable of detecting a voltage change and converting this into a simple contact closure is now installed between the 48-volt DC power source and the Ritron QuickTalk at Well No. 1. The contact closure output feeds into the RQT switch input, and a change in the state of the switch tells the RQT to transmit. It then encodes and sends DTMF tones to Well No. 2.

The signal is received at Well No. 2 by a Ritron TeleSwitch with built-in relays. The TeleSwitch receives and decodes the DTMF tones and opens the appropriate relay to start the well’s pump.

When the tank water reaches the desired level, the process is reversed. A float level switch triggers a contact closure to shut off the Well No. 1 pump, which sends another voltage change to the relay, which converts it to a contact closure fed into the RQT switch input. The RQT transmits, encoding and sending a different set of DTMF tones to Well No. 2. There the TeleSwitch receives and decodes the DTMF tones, closing the appropriate relay to turn off the pump.

Savings ring true

The new system cost about $3,000 and was installed in one day. Once it became operational, SAWS canceled the lease on the telephone line, saving $250 per month. In addition to fast payback, quick installation and reliable service in all weather, the wireless system allows for future expansion.

SAWS plans to build another well and has already purchased the land. When the new Well No. 3 is drilled and brought online, it will be easily added to the system. Another RQT will signal a TeleSwitch at Well No. 3, and an alternating relay will allow Well No. 2 and Well No. 3 to engage alternately to help Well No. 1 fill the tank.

Local equipment company Mid-State Communication Services was helpful throughout the wireless conversion. In fact, it was the company’s relationship with the local fire department that began the process. “Although the system is fairly rudimentary, there were some quirks, like the 48-volt voltage change,” says Mid-State representative Frank J. Coe.  “Once we found a relay that would accept that voltage and transform it to a contact closure, we were off and running.”

How it works

SAWS officials opted for the 2-watt transmitter because of its 1-mile line-of-sight capability, though the heavily forested and hilly terrain required an upgrade to directional, high-gain Yagi antennas. The antennas operate on a UHF frequency in the 450 MHz spectrum, although VHF (150-165 MHz) and VHF License Free MURS (5 preselected MURS) are also available.

Housed in a gasketed and sealed polycarbonate enclosure with built-in mounting flanges, the RQT in Rapides Parish is powered by a 110-volt AC adapter but also has batteries in case of power failures.

Although SAWS does not use the RQT’s voice recorder function, each switch/sensor circuit can also be coupled with a unique voice recording that is broadcast when the switch/sensor state changes. For example, SAWS officials could receive a broadcast message on their hand-held (or base station) radios whenever the pump from Well No. 2 was signaled to start.

The Ritron TeleSwitch is a radio-controlled remote switch that includes a built-in VHF or UHF radio, RF telemetry radio and a dual-relay DTMF decoder. The decoder board responds to predetermined DTMF tones to activate or deactivate one or both relays, which in turn are hardwired to the pump at Well No. 2.

All electronics are housed in a sealed enclosure. Hardwire connection of an external device is made via Heyco strain relief. Each TeleSwitch includes an antenna with BNC, AC power supply and a narrow-band compliant DTX Series RF telemetry module.

SAWS officials have found that wireless radio controls offer a simple, economical alternative to leased phone lines. The new system, with its quick payback, helps the agency set aside money to fund the new well and seamlessly integrate it with the system.

About the author

Steve Rice is president of Ritron, a designer and manufacturer of two-way radio equipment and systems based in Carmel, Ind. He can be reached at 800/872-1872.    



Discussion

Comments on this site are submitted by users and are not endorsed by nor do they reflect the views or opinions of COLE Publishing, Inc. Comments are moderated before being posted.