Amp draw increases, Voltage decreases below 104v

[Mikec557]

Hello to everyone

My situation is probably normal but, I thought I would ask for the peace of mind.

We're setup in the backyard of my in-laws and only sleep in our 29RS fifth-wheel at night. We're plugged in to a "50ft" extension cord to a 15amp outdoor outlet. This means there's not much power to run electric heat. Because it's cold here in Yulee FL, we run 3x 250watt heaters. They run non stop and keep it low 60s during the day, and high 50s at night, which is a little too cool. I set the propane furnace to 62 degrees.

Now, my EMS indicates that the line voltage runs between 120v & 112v, it just varies. But a couple minutes after the propane furnace turns on, the EMS shuts us down indicating line voltage was less than 104v. My theory is that the battery charger kicks on because the furnace electric ignition and blower motor put an instant pull on the 12v batteries.

The EMS comes back on after the 2min delay and all seems to be fine now that the furnace is running.

I think that for a brief moment I'm pulling too many amps, and that draws the voltage down below 104v.

What do you think is happening?

Thanks
Mike
2019 Reflection 29RS 5th wheel
2x 12v group 27 AGM about 6 months old

[FT4NOW]

It could have something to do with using a 50ft extension cord on a 15 Amp circuit. The size of wire over that distance might not be adequate. Also, each of your heaters is drawing about 2 Amps. I'm not sure what the current draw is on the converter and furnace blower, but you might be hitting peaks at or close to your 15 Amp limit of the source breaker you are using.

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[Mikec557]

I was thinking I'm probably pulling close to the max amps. But Is it normal for the voltage to drop and trip the EMS, rather than stay high and trip a circuit breaker?

[jkwilson]

I was thinking I'm probably pulling close to the max amps. But Is it normal for the voltage to drop and trip the EMS, rather than stay high and trip a circuit breaker?

You are probably just exceeding the current capacity of the extension cord. That's why the voltage drops. Circut breakers take some time to trip when they are just overloaded a little bit.

[Gyro Gearloose]

mike,

So what is the size of your extension cord (Gage wires)? Then how far is it to the breaker box from the socket you are plugged into. The wire size and distance makes a difference.

The smaller your cord is the more heat it will generate. If the wiring is small enough and long enough the voltage can drop well below 104 and and only be using 10 amps for example.

BTW;: motors have a much higher current draw when they start up. As current increases then voltage drops if you don't have adequate wire size. They may draw 3 times their running current until its up to speed, so that is probably why you are getting that low voltage condition.

The real concern I have here is the Non-Stop comment. If you have small cord to the trailer, I would be feeling the cord and their connections. They are probably getting hot and could cause a fire, if so.

I have a 50ft. 10 Gage cord going to my Reflection 303rls and ran the faux fire place on low for some company and the extension cord connections got pretty hot.

Pat

[howson]

Hello to everyone

My situation is probably normal but, I thought I would ask for the peace of mind.

We're setup in the backyard of my in-laws and only sleep in our 29RS fifth-wheel at night. We're plugged in to a "50ft" extension cord to a 15amp outdoor outlet. This means there's not much power to run electric heat. Because it's cold here in Yulee FL, we run 3x 250watt heaters. They run non stop and keep it low 60s during the day, and high 50s at night, which is a little too cool. I set the propane furnace to 62 degrees.

Now, my EMS indicates that the line voltage runs between 120v & 112v, it just varies. But a couple minutes after the propane furnace turns on, the EMS shuts us down indicating line voltage was less than 104v. My theory is that the battery charger kicks on because the furnace electric ignition and blower motor put an instant pull on the 12v batteries.

The EMS comes back on after the 2min delay and all seems to be fine now that the furnace is running.

I think that for a brief moment I'm pulling too many amps, and that draws the voltage down below 104v.

What do you think is happening?

Thanks
Mike
2019 Reflection 29RS 5th wheel
2x 12v group 27 AGM about 6 months old

I'm no electrician, Mike, but if you were pulling >15A the breaker on that circuit should open. Some of what I've written below echos or repeats what others have said but hopefully it helps.

Your EMS displays how many amps are coming in on the two lines--watch it closely and repeat the scenario to get an actual measurement (L1+L2). The total won't be multi-meter exact, but it should be good enough for your purpose. If the camper is pulling in >15 amps and the breaker is NOT popping on the home's circuit that could be a serious issue as the safety device does not seem to be functioning as designed.

Let's assume for a moment the total amperage is <15A and nothing is wrong with the home circuit. In that case, that 50' extension cord is seen by circuit as just another resistive device. Replace it with the shortest possible cord with the thickest gauge wire you can find in a pre-built extension cord. It should make a difference.

I think you're right that something isn't quite right, so I hope you keep at it until you figure it out. (And please let us know what fixes it once you do.)

-Howard

[Second Chance]

It could have something to do with using a 50ft extension cord on a 15 Amp circuit. The size of wire over that distance might not be adequate. Also, each of your heaters is drawing about 2 Amps. I'm not sure what the current draw is on the converter and furnace blower, but you might be hitting peaks at or close to your 15 Amp limit of the source breaker you are using.

Sent from my SM-G950U using Tapatalk

It has everything to do with the (probably) small gauge 50' extension cord and a 15 amp circuit. Check out this calculator:

https://www.calculator.net/voltage-drop-calculator.html

Circuit capacity is a function of the diameter/gauge of the wire and the length of the run. In any case, you cannot exceed the amperage draw of the 15 amp circuit you're plugged into. Just your converter can draw 10 amps recharging the battery, too. The 15 amp circuit breaker won't trip unless you draw more than 15 amps - it doesn't "see" voltage. Your voltage drop is the result of a long run of inadequate cable.

Rob

[Mikec557]

All Good points. I'll see if I can read anything on the side of the extension cord re gauge size and let you know. [EDIT; did so, it is 12ga] By the way, I checked the full length of the cords and the ends on each of the three 250 watt heaters. They're cold as room temperature. In fact all cords, everywhere in this story are cold to the touch. I just looked at the EMS: L1 changes between 106/107v and is currently pulling 2amps. I think this is the fridge because while we've been here L1 never shows anything except 0amps or 2amps. I think the 2 amp pull is the reefer defrost action. L2 is also showing 106/107v and ... it reads steady at 7amps when I know there is only the 3 little space heaters running. BUT, just now it was vacillating between 7a, then 10a, then 9a, 9a, and again down to 7a. You know how it a takes a minute for the EMS to run through all the displays before you see the same data a second time. I know I don't want to be on an extension cord like this, but for now, this is where we're at.

I failed to mention earlier but I have experimented a couple times in the last couple nights. After a trip/reset, I turn off one small space heater, dropping the amp pull to about 5amps. Then the next time the propane furnace comes on, it does not kick the EMS offline. All this got started when my curiosity got to me re the voltage dropping (and EMS tripping) rather than a breaker breaking. But I think all that has been said is right, and I think the EMS is simply faster to react to a fault situation than the old breaker in the garage on the house 15 amp circuit. By the way, who the heck knows what else is sharing this 15 amp circuit. LOL.

Thanks to everyone

[CoChris]

A lot of things at work here.

1) A standard AC breaker will trip (open) based on a combination of current AND time. A breaker (in good working order) will hold the rated current (say 15 in this case) indefinitely. It will NOT trip at 15.0001 amps (or even 15.1 amps). As you go above the rated current, the breaker (again in good working order) must hold (not trip) for a specified number of second based on percent of over current. I do not remember the spec/numbers but it is something like 125% of rated current for 10 min, 150% for three min and immediate trip at 200% of rated current. Breakers do wear out and the trip point will typically decrease.

2) Simple ohm's law that as the current increases, for a fixed resistance (all of the wiring, including the extension cord) the voltage DROP will increase. Assuming a fixed supply voltage (from outside of the house), this will result in a lower voltage at the load (trailer). This (for all intents and purposes here) is instantaneous. A current spike, even for a few milliseconds will cause a corresponding voltage drop.

3) The EMS will trip out for "low/under voltage fault" by default at 104v. Your nominal voltage is 106/107v. Not much room to spare for any current spikes. The EMS is doing it's job of protecting you.

4) A 15 amp household circuit is typically supplied by 14 gauge wire from the house breaker panel to the outlet. This is part of the resistance, and hense the voltage drop you will see. As you noted, what other current draw is on this circuit besides the trailer? You will have additional voltage drop from the power companies transformer to the house. This is typically a large gauge wire, but it carries the entire load of the house. All of these voltage drops add up.


I think the key fact here is you could remove one heater, giving yourself a little more headroom to handle current spikes/voltage drop and have the EMS NOT trip out. As I said, I think you probably have a combination of factors - low input voltage (to the house), large voltage drop and an EMS that is working correctly. This is not a case of the breaker tripping due to over current (you would have to manually reset the breaker after it tripped).

Chris

[ncitro]

I would agree with most here, you have a combination of issues at play, most likely low incoming line voltage in the house and the extension cord. I would recommend as large of a cord as possible. When I plug in to a 15 amp outlet I run my 50 amp shore cord as well as my 50 amp extension cord and then put the adapter on the end of it rather than going right into the adapter and then using a smaller cord. The 50 amp cord has #8 (or maybe even #6 ) wire in it, and I figure even if I can only draw 15 amps (actually 20 at my house), then the bigger wire size will help with heat and voltage drop.

Keep in mind its not just the length of the cords you have but also the run from the outlet back to the panel (with possibly #14 wire there). Maybe try to find an outlet closer to the panel to use, or one on a 20 amp breaker (wired with #12 wire obviously).

The other option would be to use the furnace as your primary heat source, and the shore power to keep the batteries charged. Should be no issue there with the cords you are using.