electrician question: voltage drop at outlet to TT

[Timeking]

Done this for years, but now thanks to covid I can worry about stuff I never had time to worry about.

When working inside the trailer, I've been running the AC by plugging into a 20 amp outlet fed by ~30 ft of #12 to the fuse box inside the house. With no load, nothing on, I measure 0 amps and 120V at the outlet. When I turn on the AC, the voltage drops to 111, then slowly drops to 108-109 and the amps creep up from 12 to 15. So that's a 10% drop in volts, and 20% increase in amps. When I turn the AC off, 0 amps, and the voltage doesn't immediately return to 120, but starts at 118, then 119 and back to 120 in ~4 minutes. Like something is cooling down.

So what does this all mean?

[Timeking]

Here are some definitive answers:

Progressive Industries says: EasyStart will work down to about 60 volts so it is no problem for EasyStart. Compressors can operate safely below the rated voltage but will slow and draw more current. If they reach a point where heating causes a problem, the overload will open to protect the compressor. Additionally, there are safeguards in EasyStart that will prevent the compressor from ever running that slowly and potentially tripping your power source breaker. 108 volts AC is unfortunately common at some sites and on conventional generators that are heavily loaded. I would try and stay above 105 to prevent any difficulties.

Airxcel maker of Coleman Mach 15 says: The safe range for these units would be between 108 VAC and 125 VAC. You are on the low end of that, but you should be fine. Voltage usually won’t cause damage until you get below 105, or above 130.

[Timeking]

https://drive.google.com/file/d/1wiQPfIrbuVgTLt3_yzGuHIdLXRGmEC3n/view?usp=sharing

Per this table, I shouldn't have a problem. Here is the article posted by PGE (the electric utility)
https://www.pge.com/includes/docs/pdfs/mybusiness/customerservice/energystatus/powerquality/voltage_tolerance.pdf

[CA_Traveler]

You can still add the remote. My remote isn't used much but when in a low voltage situation it pays for itself.

Note: The remote connects with a data cable which looks lide a phone cable but has 2 wires reversed. When the 14' supplied cable was to long I bought a longer one on ebay for $3.

[Boomerweps]

My PI EMS 30 Amp installed unit shuts of my TT power when I run the Air Con during the day., 125’ 12AWG total from CB box, far side of garage.
Near side of garage. 105’ total wire. 125VAC start. 6.6WATTS at idle, add AC 12.9 amps 107.7VAC, add refrigerator 15.8 amps 105.4 vac. Measured with a Kill-A-Watt between the cable and 30 amp to 20 amp adapter.
My PI EMS was added after the Kill-A-Watt above. I also picked up a plug in digital voltmeter (Amazon under $20) to quickly read since my EMS is located under the dinette bench at the TT main power inlet and I was too cheap to get the remote display. (Don’t be cheap Iike I was!)
Kill-A-Watt was on sale $20 at Harbor Freight. Multimeters are great to have but being able to just plug it in and select between readings vice fumbling with probe leads is priceless. Just turn things on and off and you can easily read the changes in volts, watts and amperage.

[CA_Traveler]

jodeb720 wrote:
Bottom line, the 12gauge extension cord which is 50' long wasn't able to handle the current needed by my ac.

Good point. What is a 12ga extension cord? Is it really 12ga vs the label? Is it aluminum or copper coated aluminum? There are other build quality considerations that can be factors.

It's probably best to just buy 30' RV cords and a pigtail adapter to 20A and not the hockey puck type.

At my sons house I need 100'. I carry a 50A 25' extension and for winter visits used 2x30A cords. But that is inadequate in the summer. So I now leave 50' of 50A at his house and we upgraded the plug to 50A.

Saved money and the cost was $0 - how you ask - free camping, get to visit the family, all good.

My general advice: Stop pinching dollars, install 50A, buy the RV cords. You're NOT paying storage or camping fees so the cost is $0 and you'll no longer have any issues.

[azrving]

I just checked the plug in the master, oops I mean “primary” bedroom which has a 8000 btu window ac unit and that plug is at 124.2 v with the window ac running. I have central air but the window unit pretty much carries the house even at 100 degrees out. Main ac is at 72 and probably comes on 6 or 8 times a day. 1900 sq ft house has been running about $140 a month. Bedroom window unit runs from 9 am to midnight and keep it set at 62 It has shut off at times and you can hang meat in the bedroom. Just some comparison info for the heck of it

I just checked my 30 amp RV plug at the full hook up end of the house right at the power pole and its at 124.5 with the window unit on and the rv ac down at the 140’ away end running

[azrving]

O just checked a kitchen plug in the RV and voltage is 112.5. Progressive is reading 112 v and 13 amps with the ac and batteries on float. Oh wait, im running a resi fridge so there may be .6 amp for that and a little more for float and a couple led lights so ac is probably really at 12 amps

[azrving]

My rv ac is running now and I just checked a random plug in the house Kitchen 127 v now the refrigerator kicked on and it dropped to 123.4 v.

Edit: just checked again 122.8 v
Fridge still running but now 124.2

Check you panel line in voltage at rest and as you add the ac load. Your run is so short you should be at an advantage there. You might even check with the power company after checking your line in voltage

[jkwilson]

myredracer wrote:
Another thing to be aware of is an AC unit typically draws about 60 amps during the momentary starup. When using small gauge wire like #12 and runs like 30', you can have significant voltage drop that is hard on the motor windings and eventually lead to premature AC unit failure. The 60 amps is also in addition to anything else operating like say the converter/charger at perhaps 4-5 amps.

I would use a #10 shore power cord with 30 to 15 amp adapter, or a #10 extension cord in addition to the shore power cord. As mentioned, you also need to consider the length of the branch circuit from the house's panel to the 20 amp receptacle which can greatly increase voltage drop.

Always have a permanent voltmeter mounted inside an RV and keep an eye on it. If it gets down to 104-105 volts, shut the AC unit off as it will cause damage. Best thing is an EMS which automatically shuts you down on low voltage. Also, always ensure the blades on your cords are kept clean and shiny and never plug in the RV with power on.

I don’t think any RV AC pulls anything close to 60A on startup. More like about 19A. People run them with generators, and if it pulled 60A on startup, the generator would have to be in the 7000W range to handle it. Generators can’t produce extra power momentarily like household wiring can for brief times, so the generator won’t start a motor that needs more than about 10% more than its rated power.

[azrving]

Timeking wrote:
I never plug my RV directly into any outlet at a campground; I use a Progressive Industries box that monitors amps, voltage. So I am monitoring voltage at the source NOT in or at the RV.

Based on what jodeb720 and azrving posted, my voltage drop is excessive. So that is now the question: Do I need to hire an electrician to run a dedicated line out to where the RV plugs in?

Also FYI, the AC has a slow start device so it doesn't kick in immediately and overload the generator when using that.

I am starting out at an advantage though, my source is 125 v so there’s a 5 v bandaid right there. I don’t think ive ever had a residence with 120 volts. Iirc Ive always seen 124 125 etc. When i built the house before this one it had a new pole and transformer Installed but don’t remember if i had a refrigerator issue or flickering lights but i called them and they adjusted the transformer and it was then about 124 v iirc

The house im in now has a transformer on the pole on the property that drops down to my outdoor shut off panel then runs into the house sub panel about 25’.

[Timeking]

I never plug my RV directly into any outlet at a campground; I use a Progressive Industries box that monitors amps, voltage. So I am monitoring voltage at the source NOT in or at the RV.

Based on what jodeb720 and azrving posted, my voltage drop is excessive. So that is now the question: Do I need to hire an electrician to run a dedicated line out to where the RV plugs in?

Also FYI, the AC has a slow start device so it doesn't kick in immediately and overload the generator when using that.

[azrving]

theoldwizard1 wrote:

azrving wrote:
My whole house is wired in 12 gauge. From the panel to the bedroom plug that also runs out to one of my rv spots is about 140’. Its 80 degrees and i just turned the rv ac on. Starting volts 125. Ac draw 14 amps voltage 115 Pretty good for that long of run

Curious. How are you measuring AC current ?

Progressive industries EMS

[theoldwizard1]

azrving wrote:
My whole house is wired in 12 gauge. From the panel to the bedroom plug that also runs out to one of my rv spots is about 140’. Its 80 degrees and i just turned the rv ac on. Starting volts 125. Ac draw 14 amps voltage 115 Pretty good for that long of run

Curious. How are you measuring AC current ?

[jodeb720]

I had my 5er out in front of the house a few weeks ago
I put my volt meter in a few of the outlets and found it between 120 and 121 consistently.

I turn on the AC and it dropped immediately down to 112 and hung in there, but as time went, the voltage dropped to 109, then 108.

That's when I switched it off.

I had a roll of 12gauge wire in the basement, unrolled it out for the 35' I needed put a couple of 20amp rated plug heads on it and connected the 5er's dogbone to the 30 amp plug and tried again.

The voltage started out exactly the same - 120-121, but as the AC started to work harder, the voltage did drop but only down to 113 - 112 and stayed there.

Bottom line, the 12gauge extension cord which is 50' long wasn't able to handle the current needed by my ac.

Now, I know there's some out there who will tell me that's not legit - and they are correct, but for an emergency, and not wanting to damage my AC unit, I'll go with it.

As it was, because the AC was on, I finished reassembling the inside of my 5er after a major repair and we were able to use it for the weekend (first time in 8 months).