Our support department gets a fair amount of calls with question on INSTEON signal troubleshooting. The problems that the customers are experiencing are related to noise on the powerline and not an issue with the ISY. I wanted to provide a few points that you may find helpful in troubleshooting communication issues to your INSTEON devices from the ISY.
We tend to look to noise at the culprit when things start to become intermittent with device communication.
Example: Today 3 or my 5 devices turned on in a scene but yesterday everything worked fine.
Tools to look for noise.
1) Place an INSTEON keypad in link mode and watch the flashing cadence. It should flash on and off about every second. When noise is present the flash cadence will be all over the place. It might flicker instead of flash and it might stay off to 5 or 10 seconds at a time then flash fast. (to put a keypad in link mode you just press and hold the set button in for 5 seconds)
2) Some INSTEON devices actually have a function called flash on traffic. This will cause the LED on the device to flash when it see powerline traffic and in some cases it can show noise also.
3) Query a device in the ISY and it should query very fast. If it takes 20 seconds (it should take a second or two) then you may have noise of phase bridging issues.
What to do to identify Noise.
1) I find the easiest way to get to the bottom of the cause is to look for the idenitifier like the flashing on the keypad then go to the breaker panel and turn off the first breaker. Look to see if the flashing goes back to normal. If not then turn that breaker on and turn off the next. Keep doing it until the keypad flashes at a normal cadence. Note: Try not to switch the breaker that controls the keypad you are watching. If you go through all of the breakers and you have found the cause then it may be the circuit the keypad is on. In this case you unplug any device plugged into that circuit and see if one of the plug in loads is the cause. Once you find it you can simply buy a plug in filter and filter that device.
In closing, there doesn’t have to be a device that you just added that causes the problem. It could be a device you have had for years and one day it starts to throw noise on the powerline. I had a customer that had a Sonic Care tooth brush and then the brush was in the charger it destroyed communication to 120 switches in his house. This is just one example and there are other stories like this with simple plugin loads that start to produce noise on their own.