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High/Low Voltage

All issues related to RV electrical systems

Moderators: Techno Eric, Techno Tami

by KTM5151 » Tue Sep 15, 2015 2:41 pm

What is considered high and low voltage? I know 120 is the standard, but where are the limits that are standard?

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Joined: Fri Jul 24, 2015 5:23 pm

by Techno Eric » Tue Sep 15, 2015 2:47 pm

Generally speaking, low is below 104 and high is above 132. A good electrical management system will cut power to your RV if the voltage is outside of these limits. Surges are different and can be an extremely high spike, even in the thousands, but can occur in a fraction of a second. I have experienced low voltage many more times than I have high voltage. This can happen for a lot of reasons, but overloading in a park can certainly cause it, especially in the Summer when everyone is cranking out their AC units.

Techno Eric
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by Ross » Tue Sep 15, 2015 4:23 pm

While 132 volts is right on, I think the low is 108 volts. 120 volts plus or minus 10% is 120-12=108 and 120+12=132.
Below 108 can cause failures in refrigerator and air conditioner controls.
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Joined: Wed Jul 15, 2015 11:37 pm

by 360true » Tue Sep 15, 2015 5:46 pm

We have a Progressive protection system. Many campsites have seriously fluctuating frequency and voltage as well as reverse polarity and other issues. With the amount of expensive electronics aboard most rigs now, it was a cheap insurance decision for us.
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Joined: Sat Aug 01, 2015 3:49 pm

by Carl » Sat Sep 19, 2015 10:39 pm

We were at a small, commercial campground in South Dakota. Our circuit protector wouldn't power-up, but we were there with other RV Care-a-Vanners for a Habitat for Humanity build so we didn't have the option of leaving. I used a ten-dollar gauge to check for voltage and polarity--120 and good. I plugged into the power pedestal and turned on one air conditioner. It started normally, then began to slow down. I quickly looked at the voltage gauge, which read 93 volts, and then, even more quickly, turned off the air conditioner and unplugged our rig. Fortunately, we were able to relocate to another part of the campground, but our group had to agree to run only one air conditioner each, minimize microwave use, and to take turns doing a load of laundry for two weeks. Bottom line--don't neglect circuit protection. (By the way, I can remember when common household power was called "one-ten" and 120 volts was considered "high".)
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Joined: Fri Jul 17, 2015 11:33 pm

by DonPD » Tue Sep 22, 2015 6:34 am

Low voltage will damage your A/C. I purchased a autoformer. It will boost the low voltage. Here is the site for the autoformer I purchased. The site will explain how it works better than me.

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Joined: Thu Jul 02, 2015 5:08 am

by Batterup46 » Tue Sep 22, 2015 11:50 am

This weekend we stayed at a KOA near Cleveland and when I plugged into the 50 amp receptacle my Progressive Electrical Management System tested the power and clicked on. The voltage readings at the Progressive were 118 volts on each leg, and E-0 fault readings on each leg. My wife noticed on the EMS panel inside that the two legs showed 138 and 106 volts. I shut off the power at the pedestal and plugged into the 30 amp receptacle and again the Progressive showed 118 volts, but inside the coach my EMS showed 94 volts. We repeated this several times with the same result. Then I tried the pedestal next to me and the voltages were normal inside my coach, both plugging into the 50 amp receptacle and the 30. I ended up staying plugged into the adjacent pedestal since we were traveling with friends. The KOA didn't have an electrician available on the weekend.

Two questions:

1. Was the problem likely caused by an open neutral or some other problem?

2. Why did the Progressive not indicate a problem, since its specs say that it protects against open neutrals?

Paul Miller
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Joined: Tue Sep 22, 2015 11:34 am

by Techno Eric » Wed Sep 30, 2015 8:27 am

Hey Batterup,

was an electrician ever able to come and check on what the problem was? Always a good idea to have a meter available to check yourself. I have had open grounds before and the Progressive will identify that with no problem. Interesting that you were getting one reading outside and a different reading inside. I assume you were using the data cable with the remote display inside connected to the Progressive? Or do you mean you have a seperate unit inside?

Techno Eric
Posts: 110
Joined: Fri Jun 26, 2015 5:14 pm

by Hexnut » Tue Nov 15, 2016 7:06 am

We stayed at a private camping area for about 3 weeks in August. I plugged in the EMS-PT30C into the 30a pedestal and all was fine until I began to draw 10-15a. The voltage would drop from 120-122v down to 108v and cut power. So it seems the low voltage cut-off is 108v and not 104v. Long runs of undersized wire seems to be a common problem that shows up when a current demand is placed on the circuit. All the more reason to use an EMS. Otherwise, you could unknowingly be causing damage.
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Joined: Wed Jul 01, 2015 3:40 pm