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AN-102: MDT Wiring Guide The MDT is a versatile radio transceiver that can accept a number of different inputs depending on the unit type ordered. This guide explains the various connections and their identifications within the CIT software for the following products:

• TW-140xx-P Single Pulse input • TW-140xx-PP Dual Pulse inputs • TW-140B-R Runtime Input • TW-140B-N/E Neptune & Sensus Inputs • TW-140xx-PX External Temperature input • TW-140LW-xxx Line powered units

The following steps should be followed to make the connections to the MDT:

• Unscrew single screw to open the case • Locate the green connector(s) shown in the images for each MDT type and

insert the wires. • Verify the connection integrity by giving a little tug on the wire to make sure

it is solidly seated. • Close the case and secure with the screw.

Two types of connectors are used on most MDTs as shown in the photo below.

Primary pulse Connector (right side in photo): • Wire size: 20 -26 AWG solid/stranded strip length 5/16” (8mm) To use this connector, push down on the spring tabs with a small flat blade screwdriver, insert the wire, then release the spring. It is best to insert the wire at 30º to 45º from perpendicular. Secondary Connector (left side in photo): • Wire size: 18-28 AWG solid/stranded strip length 3/16” (5mm) This connector requires a 1.4 to 1.8mm flat blade screwdriver to work the screw terminals.

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TW-140xx-P (Single Pulse units)

Water & Gas meters: The polarity does not matter for connecting to a Water or Gas meter, which typically uses a magnet reed type switch to generate the pulse. Electric Meters The polarity is important for connecting to many Electric meters.

• The Common input (closer to the battery, shown in Green) must go to the common terminal, variously labeled ISOL COM, “-“, or COM.

• The Pulse Input (closer to the top of the unit, shown in White) goes to the pulse output terminal, labeled variously WH+, P1, “+”, or ISOLATED OUTPUT 10/100/1000.

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TW-140xx-PP (Dual Pulse units) The Dual Pulse option adds support for a second Pulse input counter. The same polarity requirements of the single pulse MDT apply to the second input.

The different pulse input data is identified in the CIT/Configuration/Sensor View as shown. In the Configuration/Sensor View tab, the Sensor type is either Pulse_Totalizer_1 or Pulse_Totalizer_2. Separate Units, Meter Type, and Count factors can be assigned to each totalizer count.

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In the Monitor Data tab, the second Totalizer count is shown as Sensor2 Reading

In the daily report output files, each pulse counter can be identified by the assigned Units type (Gallons, KWHours, etc.) and the assigned Meter Style (Hot/Cold). Alternatively the daily report file can create a phantom RadioID to uniquely identify the 2nd pulse input data. Contact Tehama for more information regarding the phantom RadioID.

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TW-140B-N and TW-140B-E (Encoder Units)

Our TW-140B-N can read only Neptune encoder registers. Our newer TW-140B-E can auto-detect and read both Neptune and Sensus encoder registers. • These units use a separate module at the back of the MDT to interface to the

Encoder meters. The units come with a removable black connector pre-installed at the factory.

• Remove the connector with a slight tug on the connector. • Insert the wires from the meter into the connector. There is a small spring in

the connector to catch and secure the wires. If you need to remove the wires, the spring can be released by inserting a tiny flat blade screwdriver into the rectangular holes.

• Wire gauge must be between 20 and 26. Solid wire is recommended but not required. Use of small pliers recommended when inserting stranded wire.

• Once inserted, verify the connection integrity by giving a little tug on the wire to make sure it is solidly seated.

• The connector is keyed to insert in only one orientation. Insert the connector until a snap is heard.

The color coding for each meter type is on the following page.

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For Neptune Meters • Following the color coding marks on the Neptune meter, B/G/R (Black, Green,

Red), insert the wires into the connector in the order shown below.

For Sensus Meters • Insert wires from the meter in the order shown here

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TW-140B-R (Runtime Unit)

The runtime unit connects across the 24VAC terminals of a typical zone valve. The polarity of the connection does not matter.

Whenever the thermostat energizes the valve, the MDT will increment a Seconds counter. The units for the runtime count can easy be changed to Minutes or Hours from within the CIT using the count factor on the Sensor View -> General Configuration tab. For minutes enter 0.0166667 (1/60). For Hours enter .00027778 (1/3600).

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A second signal is sent by all Tehama runtime units that indicates whether it is properly connected to an active 24VAC circuit. This can be used to detect a tamper situation and can be programmed via the CIT to send an alert email upon change (set the Enable column to True).

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TW-140xx-PX (External Temperature)

The TW-140B-PX versions add support for an external thermistor temperature sensor.

Pulse meter data goes to the top connector, following the same polarity requirements indicated for the TW-140B-P MDT. Temperature probes go to the bottom connector, shown with blue/white wires. There are no polarity considerations for thermistor probes. Older MDT units had this connector configuration:

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Wiring Diagram for Line powered “LW” units

The line powered MDT, TW-140LW-xxx, comes pre-wired with a pair of Red/Black power wires in addition to the standard green spring connectors for Pulse data and external temperature probes. This configuration is primarily used for Electric meters that can provide DC power to the MDT. Power: Red +9 to +16V DC Black Ground reference for the DC power Pulse Input: White position Meter Pulse output Green position Meter pulse Common or ground. Follow the same polarity requirements as indicated for the TW-140B-P MDT

Contact us: Tehama Wireless 2607 Seventh St Suite D Berkeley CA 94710 415.495.7344 info@TehamaWireless.com ©2014 Tehama Wireless Design Group www.TehamaWireless.com Rev.1403