Metered PDU's showing high voltage in the house.

[TechBoyJK]

I have a MonsterPro 3500 PDU and another generic PDU both plugged into some outlets in the house.

They usually read 120.. 119 or 121 sometimes.

This weekend, the generic PDU was reading 124V and the Monster was reading up to 134v and alarming for abnormal voltage. It even shut down once after going into protection mode.

Could this be a fault somewhere in the house? Or should I contact the utility company and file a complaint?

 

[Micrornd]

First put a DMM on the line and check the voltage.
Obviously one of those PDUs is not giving an accurate reading.
Does the Monster trying to read the peak of the wave (wrong way) and the generic reading the average (correct way).
I would not put it past Monster to do something like that to stress their "importance".
Either way, without checking with a reliable DMM, you don't know which PDU is reading correctly.

 

[Red Squirrel]

A few volts is fine. Depending on the loads on the transformer it will slightly alter the voltage. Sometimes the two legs are slightly unbalanced too, so one might read 121 and the other 119. It won't always be 120 exactly.

 

[TechBoyJK]

My Monster pro 3500 is reading 130-134 sometimes. If it hangs up there too long, it shuts down.
I put it on the same outlet as another metered PDU, and it was only saying 120ish.. while the 3500 is reading in the 130's.

 

[Red Squirrel]

Ohhh yeah that seems off, I missed that part in the OP. When the Monster was saying 130ish did you test voltage with multimeter at that same outlet too? I'd rule out the PDU first. One thing to test is when it goes up to 130 test other circuits around the house too, if some read lower than 120, like 110, you may have a floating neutral situation, I'd call power company ASAP if you determine that. Floating neutral basically means loss of neutral, which causes everything on one leg to be in series with everything on the other. Voltages can swing a lot depending on how balanced the loads are.

130 is above acceptable range I believe so even if it's not a floating neutral but you determine it's really your house and not the PDU then I'd get them involved anyway. I'm surprised it's shutting down at that though, 130 is not too much for computers, I think most can take up to like 160 - not that I would test that. Some have auto switching PSUs so they'll detect if it's 240 or not, those have much wider ranges. If there is a setting on the PDU to change shutdown threshold you could do that for now.

 

[TechBoyJK]

So update.. might be the monster PDU.

1) I have a main panel and a subpanel. The Monster PDU is hooked up to an outlet on the subpanel. All of the outlets in this room are on dedicated circuits. Anywho, I turned off every single circuit on the subpanel except for the one the PDU is using and it still showed high voltage. 130-134 volts, while the led for 'abnormal voltage' blinks. And the voltage value is always in flux.

2) I've hooked up the Monster PDU to outlets that are on the main panel and I still get the same high readings.

3) I have another, much newer Livewire PDU (albeit not as nice) and on the same outlets it's input voltage is always 119-121 and it's not changing constantly.

4) I've unplugged everything from the Monster PDU and it still shows wacky readings.

 

[NutBucket]

I wouldn't be surprised if it's the PDU. There's a reason a good multimeter is around $200 and there's a reason they need to calibrated regularly.

 

[TechBoyJK]

Another thing, I've hooked up the Monster PDU, to the Livewire PDU, and it still shows the wacky readings. The Livewire was showing 122 while the Monster was above 130.

I took it further and hooked up the Livewire PDU to a cyberpower PDU with battery.. both Livewire and CyberPower both had the same reading of voltage while the Monster, last in the chain, showed almost 10 volts higher.

 

[TechBoyJK]

https://drive.google.com/open?id=0B8lfKV-5DwbcTFFjN3Nrak5iVFk

Here's a link to a video of the input voltage freaking out... Keep in mind, the PDU is plugged into the other PDU which is giving a normal reading. The Monster PDU freaks out whether it's plugged directly into the wall, or the Livewire PDU.

Is there such a thing as a voltage sensor that could be failing? Or could it be a bad capacitor? Thoughts? I'd love to fix this thing.

 

[NutBucket]

No way to diagnose without figuring out the circuitry inside. But truth be told, it's probably a fairly simple device with a huge profit margin.

 

[dave_the_nerd]

Monster is garbage, so... I'd believe the other PDU. Get a third if you want a tie-breaking opinion.

 

[TechBoyJK]

I did try two other PDU's (Livewire and CyberPower) and both read the same thing while the Monster flakes out.

The monster PDU has been rock solid for about 10 years now.. so I'm feeling like this might be time to retire it. It's been in my studio rack at the top for a long time..

 

[Red Squirrel]

If it's jumping around, it almost sounds like a loose component inside, like connection to an ADC or something. I imagine a circuit in a PDU would be quite miniturized and hard to troubleshoot though but might be worth opening up to look for any obvious looking faults like a loose resistor.

 

[TechBoyJK]

If it's jumping around, it almost sounds like a loose component inside, like connection to an ADC or something. I imagine a circuit in a PDU would be quite miniturized and hard to troubleshoot though but might be worth opening up to look for any obvious looking faults like a loose resistor.

So, I messed with it some more last night. I finally got it out of the rack and out so that I could get it under light, etc.

It was actually pretty clean inside. I opened it up, and it booted up normally, and it says power is clean.

I experimented some more by connecting it to my CyberPower UPS unit. It also has an input voltage display.

At the time of testing, with the CyberPower UPS connected to the wall, it gave me a readout of 123 volts and didn't flux during the test. I connected the Monster PDU to the CyberPower UPS and the Monster PDU gave a readout of 124-125 volts which is bounced between every few seconds and then chill out at 125. After 10 minutes it moved up to 126 but didn't go beyond that for an hour and settled on 125.

Here's the thing, I then disconnected the CyberPower from the wall plug, putting it on battery backup power. The Monster PDU stayed at 125 for 20 minutes or so until I plugged the CyberPower PDU back in.. The Monster PDU didn't flux at that either.

I then switched it, and hooked the Monster PDU back up to the wall. The Monster PDU stayed at 125 like it did when it was plugged into the CyberPower. I then plugged the CyberPower UPS into the Monster PDU.. and the CyberPower read the same thing as last time as well. 123 volts.

So they were both reading different from each other, but read a consistent value in both configurations.

This makes me wonder if the Monster PDU is reading the peaks while my other two PDU's (CyberPower and LiveWire) read an average?

Either way, after I opened it up and used a powered air duster to clean the internals, it pretty much stuck at 125 and wasn't freaking out in the 130's.

That said, I'm going to do the same study again tonight and see if I get different results.

EDIT: Another thing. WIth every configuration I had between the CyberPower UPS and the Monster PDU, I would use a basic outlet tester on all 14 outlets of the Monster PDU. Every single time the tester said the outlets were good. The tester would show ground faults, reversed wires, etc.

It's so weird, so many things point to the Monster PDU being healthy.

 

[TechBoyJK]

https://www.amazon.com/Monster-MP-PRO-3500-12-Outlet/dp/B0002PZGNY

I noticed one of the features is 'High sensitivity digital meter measures available voltage and current demand'.

There's one salty review where the guy said he went through 3 of these (in a live setup). Everyone has pretty much said 'no.. that's user error' but one comment was interesting.

This is a little late, but some advice:

The PRO 3500 has a tiny little slide toggle next to the (over-spec) heavy duty AC cord. It's marked "Studio" and "Stage". The "Stage" side of the switch puts the unit in a mode that won't shutdown in case of minor transients. "Studio" mode will in order to protect sensitive tube pres and such.

Also, if your Inverter generator isn't producing a pure sine, the PRO3500 will freak out. Personal experience here.

 

[NutBucket]

You're looking way too much into this. Just ignore the meter and move on.

 

[TechBoyJK]

You're looking way too much into this. Just ignore the meter and move on.

i have a kid in the NICU and the last thing I want to do is buy another PDU like this...

Hard to ignore when it's shutting down in the middle of a gaming session.......

It's not just giving a high reading, the PDU is reacting to it and powering off.

 

[NutBucket]

Dump the PDU and replace it with an UPS if you're that concerned. Or just dump the PDU as it does nothing anyway.

Sorry to hear about your kid.

 

[Red Squirrel]

I wonder if it is reacting weirding to voltage drops/increases from the various devices plugged in or around it. I know at my parent's the laser printer actually causes the UPS to get confused because the voltage drops enough but not quite enough that it should trip, then it trips anyway on/off very fast. Usually results in PC freezing or rebooting. Printer is obviously not plugged in the UPS but in same circuit. So could be something similar.

If the PDU otherwise works, I probably would not worry too much though, but I would invest in a decent multimeter so you can test stuff like this better.

 

[TechBoyJK]

I wonder if it is reacting weirding to voltage drops/increases from the various devices plugged in or around it. I know at my parent's the laser printer actually causes the UPS to get confused because the voltage drops enough but not quite enough that it should trip, then it trips anyway on/off very fast. Usually results in PC freezing or rebooting. Printer is obviously not plugged in the UPS but in same circuit. So could be something similar.

If the PDU otherwise works, I probably would not worry too much though, but I would invest in a decent multimeter so you can test stuff like this better.

I was worried it was something in the house or a device connected, so I ended up shutting off every single breaker except for a single outlet. Needed a flashlight because i killed all the lights.

Even with nothing else in the house on, and only one active circuit, and nothing plugged into the Monster PDU, it was still spiking over 130.