Line 2 monitoring what source?

[dmp1991]

I've got a 2021 DSDP. Just checked my control panel randomly, about a day after pulling into a new campground, and was alarmed to see it said line 2 was at only 8 volts. (That's not a typo. 8 volts!) Immediately checked the Power Watchdog and it said 120 volts on both line 1 and 2.

Both the wife and I panicked for a bit. Then the wife remembered she and I were discussing the engine block heater yesterday and we had agreed to turn off the breaker. It turned out turning that breaker on made the control panel show line 2 as 120 volts. Being gluttons for punishment, we turned that breaker off again and now the control panel had a flashing brown out warning and showed line 2 as again at 8 volts. We turned the breaker on again immediately and the control panel still showed the brown out warning and the 8 volts on line 2. I'm guessing there must be some sort of timer for that warning because after a few minutes of us arguing about what could be going on, then some thinking about it, the control panel went back to a reasonable number for line 2. 119 volts.

Is it normal for the control panel to monitor the output of the engine block breaker? If so, where is the 8 volts it's showing coming from? Is our breaker bad or is there a small short somewhere leaking 8 volts into that line?

 

[Richpatty]

This is completely normal. Here is an excerpt from a thread I started a while back on that "other forum board":

Odd Numbers on Precision Circuit system

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I was working on an unrelated electrical project this past weekend and came upon an odd behavior with the Precision Circuits Power Control System - which I now know is probably expected.

As part of this effort, I had to disconnect shore power and turn of the inverter. I also brought down many of the breakers on the shore power side. When I brought the power back up (using a 20A home outlet with a dog bone connected to the 50amp surge protector), I left some of the individual breakers off, I noticed really strange numbers on Precision circuits display up front. It showed one leg with about 4 volts instead of the expected 122 (which is what the other leg displayed). See pics below. I also noticed the PCS reporting that I had a 50amp connection instead of the 20amp I was connected to. I pondered this for a while wondering if was my surge-protector (it wasn't) or the transfer switch (That wouldn't be good).

But just when I thought I would give up, I turned off the main breaker and flipped all the breakers back on (and main) and - surprise - all was right again. I will not bore everyone with the different scenarios and combinations I tried, but I did find flipping certain breakers off made these numbers appear. So when I came in the house, I began to Google it and although I did not find anyone who saw this before, I did find these troubleshooting notes from Precisions site (http://www.precisioncircuitsinc.com). This is when I realized that this behavior is probably expected based on these notesHighlighting mine)

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If Incorrect Voltage Displayed:
If not check to make sure all circuit breakers are on and that L1 screw terminal is wired to L1 Breaker, L2 screw terminal is wired to an L2 Breaker, and that there is a wire from N to the Neutral Bar.
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If System displays 50A Service when plugged into 30A Service.
1. Make Sure all Circuit Breakers are on.
2. Check Voltage between L1 and L2 DIRECTLY ON PCS Module, should be 0Vac
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Tip: Things like Water Heater, whose circuit breaker is occasionally turned off, should not be wired to Relay 3 or Relay 5
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As you can see, the common denominator is to not shut down key breakers on the shore power side...or it will mess with the PCS Power Control System.

I hope this helps someone out there as I have learned SO MUCH from all of the folks on this forum.

Thanks
Rich
Attached Images

 

[Rich W.]

Yes, that is normal. Its not monitoring output from the block heater; the Precision Circuits display reads line 2 voltage from the block heater breaker (I don’t know why) so if it’s off, things get wonky. But it’s normal, the breaker is fine, and there’s nothing to worry about. I leave my block heater unplugged (outlet in a rear drivers side compartment) and the breaker on.

Pic is with my block heater breaker off

 

[Kevin D Pem]

What you are seeing is an induced voltage. No one pays attention to it because it is harmless.

Put another way one wire with a load is working as a transformer. The wire that is not connected(floating),is seeing that sine wave! And an induced signal is produced.

It is the reason integrated circuitry ports are tied to ground using resistors.
When no action is required by a false signal, there is no reason to try and eliminate it.


Hope that helps!!!

 

[dmp1991]

Thanks all! My mind is at ease now.

And yes, I meant monitoring the output of the engine block breaker.