Summary

In the event of multiple device no replies, where a multitude of device messages are present over a large section of two-wire, begin with the basic troubleshooting principles below before proceeding with diagnostic steps.

IMPORTANT: Tools Required

#2 Phillips screwdriver

Wire stripper

Approved mA clamp meter such as: Armada Pro 95i, Tempo 360B

Not all mA clamp meters have the required resolution to find the mA load discrepancy on the wire path. Approved mA clamp meters have low pass filter settings that provide a stable mA reading while devices are communicating over the two-wire, microamp resolution and a true RMS measurement.

Note: Decoder communication can occur on 15-second boundaries each minute. When taking clamp-meter readings, wait for an idle interval between communication events for the most stable measurement.

Process Steps

The following principles apply to every two-wire troubleshooting effort and should be followed before and during the process steps below:

1. Make a clear statement about what the problem is and is not.
2. Ask what changed to cause the problem (things were working, now they're not).
   1. Look for signs of digging (new trees planted, new fence, utility work, etc.).
   2. Identify changes to the site irrigation system (pipes, new gardens, fields, etc.).
3. Start at the controller and then move out along the two-wire.
4. Break the problem in half (binary search method) to isolate the fault efficiently.
5. Always use waterproof connectors (3M DBRY-6). Do not reuse them.

Check the Messages

Check the message list for specific device information. Device messages with wording like "No reply," "No response," or "Two-wire communication failure" indicate a problem with two-wire communication. You can see the device ID at the bottom of the error screen. Messages can help determine if the issue is isolated to one section of wire path. If multiple decoders fail in the same area of the two-wire, focus troubleshooting there first.

Check the Controller

1. Disconnect the two-wire connection from the decoders in the field from the controller.
2. Verify there is voltage on the two-wire terminals. Should be between 30 and 35 volts AC.
   1. If no voltage can be measured on the two-wire terminals, power cycle the controller and measure again.

Legacy 3200 Only: If there is no voltage measured on the two-wire terminals, check if the two-wire status is OFF. If OFF, navigate to Advanced via the dial, then to the two-wire settings menu. Two-wire always on should be set to YES. 

3. Connect a single valve decoder — search and assign it if necessary — then do a self-test and look at the two-wire voltage drop. If you have a clamp mA meter, do a manual run on a zone with a solenoid connected to the decoder and verify the red and black wire currents are close to the same (within 10%). Unassign the test valve decoder when finished if necessary.
4. Check the two-wire mA draw from the Run screen on your controller. mA higher than expected indicate a ground fault or a two-wire device that needs to be replaced. An idle system should draw less than 100 mA for a small-to-medium system, or less than 250 mA for a large system.
5. Re-connect the two-wire that goes to the field decoders. If the two-wire gives an over-current error, please use the Resolving a Two-Wire Overcurrent document.

Check the Two-Wire Path

Before starting, identify your wire path configuration. If the wire path is looped, disconnect the furthest loop from the controller. If the wire path is a star or straight run, proceed to step 1.

1. Confirm the expected mA draw range for the wire path or section of wire path you are testing. This can be done by summing the mA draw of each two-wire device downstream of your measurement location. Record device quantities from where you're taking your clamp measurement to the end of your wire path using the Two-wire Device mA Draw Reference and Calculator.

Note: If you do not know the number of devices downstream of your mA measurement location, trace your wire path from the measurement location to the end of the wire path, opening each valve box and accounting for all of the inbound wire pairs. You can then use the Device mA Draw table to get your expected mA draw.

(Two-wire device mA draw)(device quantity) = Expected mA draw*

*Baseline two-wire devices have an acceptable mA range. See Device mA Draw table below.

2. Confirm that the mA draw on the red and black wires are close to the same (within 1% of each other). With your milliamp clamp meter, clamp the red wire and record the mA value. Do the same for the black wire. Point the arrow on the edge of the clamp meter away from the controller to measure the red wire, and toward the controller to measure the black wire.

Note: When measuring mA with your clamp meter, it is important to have the wire in the center of the clamp meter (Alignment markers may be present) and perpendicular to the meter.

3. Compare the expected mA draw to the actual mA draw measured with your clamp meter at your measurement location. If over current on both wires and mA measured on each wire is the same, issue is likely a shorted two-wire device. If mA measured on red and black wire is different by more than 1%, the offset typically indicates a poor splice on the higher mA load wire in the field.

Note: This should be done when the system is idle (Not watering). mA draw while the system is watering will be higher due to running solenoids. Decoder communication on 15-second boundaries can also momentarily affect readings.

4. Work your way from the controller down the wire path, or use the binary search method, using the clamp meter to determine where the problem is. Once the problem is identified, replace splice(s) or two-wire device(s) as necessary. Replace all connections at the problem site — do not reuse old connectors. For mA measurements lower than expected, use the Device mA Draw Calculator linked above (or table below) to see how many devices could still be connected between the wire path problem and the controller. Target that location on your wire path first.

Note: As you work your way down the two-wire, the expected mA draw will change as the current measured is for downstream devices only. Please see Two-wire mA Draw Example at the bottom of the page. Branch 1 indicates a small mA leak at the end of the wire path, causing our actual reading to be ~1mA higher than our expected reading. 

At Each Suspect Valve Box

When you identify a valve box containing a decoder that is not communicating, follow this procedure at the valve box:

1. Cut off the connections to the two-wire.
2. Measure the two-wire voltage. If the two-wire is not working at this valve box, there is a broken wire between this valve box and the previous valve box.
3. Connect the decoder back to the two-wire with wire nuts only — not gel caps yet. Write down the serial number of the decoder.
4. Walk back to the controller and do a test of the decoder (this is why you recorded the serial number). A healthy decoder should respond 10 times out of 10 tries, and the two-wire voltage drop during self-test should be less than 6 volts.
5. If it works, go back to the valve box, reconnect the two-wire continuation with waterproof connectors, then move to the next valve box.
6. If it does not work, replace the decoder with a new one and verify communication — do a search-and-assign over the bad decoder.

Note: if there are numerous decoders that are not working, they may have been damaged by lightning. If lightning is suspected, you will need to replace all lightning arresters on the two-wire.

What Our mA Measurement Means

For more information see Interpreting Current Readings.

Determining Number of Devices

1. Collect the controller program summary locally via USB export or remotely via AdminManager.

Note: The program summary file does not include unassigned two-wire devices. It is important that all devices on the two-wire path be assigned for properly determining expected mA draw on the two-wire. 

Device mA Draw

*Measured with the Armada Pro 95i

Two-wire mA Draw Example

If you check all of the preceding steps and fail to resolve the issue, consider contacting Hydropoint Support. Hydropoint Support can be reached at support@baselinesystems.com, support@hydropoint.com or 866-294-5847.