Is 30 amp really needed

[J. Morgan]

I have tested continuous draws on different circuits, I can state without equivocation that MY circuit breakers do not trip at 80% load.

I am going to have to side with Mark, not only because of my own experience, but because what he states makes a lot of sense and seems to be based in a true understanding of the applicable code.


Superat stultitia.

[Ag&Au]

This whole discussion is like many others I have read here.

When engineers design systems, whether they be electrical, mechanical, structural or whatever, they design them with all worst case scenarios taken into account. This is considered by most to be reasonable and prudent practice.

However there will always be the "Hey guys, watch this!!" type of people who will want to push the limits and prove the designers wrong. Because, the designs of most systems are robust, (because of the engineers prudent practices) they often get away with their "look how smart I am" tricks. They then become emboldened, and continue these practices until eventually some (perhaps many) of them will meet with an expensive education on why things are designed in this manner.

The above are my opinions. They are based on many years of observation of humans interacting with devices they feel were designed by other humans who were not as smart as they are.

My advice:

Do what the designer of any product recommends rather than following your instinctual desire to take short cuts. In the long run you will come out ahead.

Ken

P.S. I am a retired air traffic controller. Our standard separation was generally 5 miles and 1,000 feet. I often wonder while reading these discussions, how the shortcut takers would feel if I chose to use 1 mile and 100 feet because I knew it would work.

[J. Morgan]

You jump to conclusions.

Some of us go around "design" because we work with what we have, and some of us change things different than designed for cookie cutter mass production because we want something different.

Frankly, if there is only one right way of design, why don't all bridges look the same?




Superat stultitia.

[J. Morgan]

Oh, regarding the question at the top of the thread, it is obvious that the air conditioner CAN run on a 20 amp circuit because that specific air conditioner and virtually all other RV air conditioners run exclusively on a 20 amp breaker in the trailers electric service box, so yes, an RV air conditioner can and DOES run on a 20 amp circuit.

There were lots of posts on here warning that other draws should be limited so not to trip the 20 amp breaker.

It is plain that there ARE qualifiers for this to work out, and the qualifiers were well addressed.




Superat stultitia.

[Ag&Au]

Originally Posted by J. Morgan

You jump to conclusions.

Some of us go around "design" because we work with what we have, and some of us change things different than designed for cookie cutter mass production because we want something different.

Frankly, if there is only one right way of design, why don't all bridges look the same?




Superat stultitia.

You may be correct that I jumped to some conclusions, but not the one you think.

I didn't really pay attention to who was posting what. So it was not directed to anyone in particular including you. However you are free to take it as you wish. After all it is only my opinion. If I am directing a post to another particular post, I will quote the referenced post.

Regarding bridges; There ae many final appearances, but all bridges are designed to carry a specific predetermined load. What some are suggesting here is that it is OK to built it to carry 2/3 thirds the specified load, because they've built bridges that way and none have yet collapsed.

I still stand by:

Unless one is an engineer or designer and wishes to totally redesign any system, then one shoul read and follow the instructions. It's simply common sense. In my opinion, for anyone to advise someone else to disregard a manufacturer's instructions on engineered systems, because they tried it and it worked is just plain irresponsible. It opens both the individual giving the advice and Airforums to possible liability.

Ken

[J. Morgan]

Save the ancient Armstrong A/C that came with my trailer, I "reengineered" everything. Every system, every wire, even my axle placement.

Respectfully, whether any of what I wrote above matters or not is moot, because separate from any opinion, even your air conditioner (if you have one), runs on a 20 amp breaker.

The question was whether a 30 amp circuit is NEEDED to run his AC, the answer is obviously no.

(FWIW, Wally himself was not an engineer)

FWIW X2, I take no personal offense whatsoever when I debate, I endeavor to debate the issue, not the person. No heartburn on my behalf)


Superat stultitia.

[DaveFL]

Originally Posted by teagues

The panel inside my 20' has a 30 amp main breaker feeding 4x 20 amp breakers. One of those is for the air conditioner, another for the converter, and the other two for the electrical outlets.

If the air conditioner tries to draw more than 20 amps, wouldn't it throw its breaker at the panel?

I know, I know, voltage drop, other draws, etc. But if I can supply 20 amps 120V to the trailer (properly rated cord and adapter, good city electric service) and control the other electrical draws (turn off the converter and use the house batteries for DC, remember no to dry my hair, microwave popcorn, or make toast), is there some other problem I am overlooking?

Yes, size of wire and distance from main source, will you be the only one in control of the switches
New connections will not have as much loss as old corroded fittings, so AS CTA by going one step up from minimum need. In mine they put 30 amps and two A/C's but to protect the system only one could be used at a time by throwing a switch in the system. I moved up to 50 amps 220 volts but still only try to use less than 30 on each circuit with an eye on installed meter. One other thing you can do is take the temperature of the wire and connections when in use, just before they smoke they will show a higher temp. than ambient air.

[teagues]

Originally Posted by DaveFL

Yes, size of wire and distance from main source, will you be the only one in control of the switches

No, but the few times when we've needed to do this, everyone has understood the situation (i.e it's HOT and we NEED air conditioning) and knew not to plug in anything more heavy than a cell phone charger. Lights are another matter -- run off of house batteries, and LED in any case.

Honestly, I'm far less concerned about running the AC with reliable 20 amp service than I am about just being plugged into some of the 30 amp pedestals I have seen. Long overdue thanks to whomever invented the polarity tester and the kill-a-watt.

[KJRitchie]

At home I hook up our Airstream with the 30amp cord connected to a 25ft 30amp extension cord and then use a 15amp pigtail and plug it into an outside outlet. I don't run the AC however one time I had left the thermostat on and when the day heated up the 13.5k AC was running when I came home from work. Trailer was cool inside but I decided to turn it off. The fridge was on 110v too at the time.

Kelvin

[Lumatic]

One thing that was either not mentioned above, or I missed, is the electrical requirements and implications for 13.5 vs. 15K ACs. I also assume there are different specs for different brands?

I have a Dometic Penguin 13.5 AC. It is my understanding that boon docking I need 2 Honda 2000si inverter gennys to run it. It is also my understanding that the 2 2000 inverters would not be up to the job of running a 15K AC.

I really don't want to stir the pot here although I realize I probably am.

[Rocinante]

Engineering discussions are fun. Here's what we know empirically about our trailer:

(1) We don't run Rocinante's heat pump unless we have a 30-amp power source. We don't try to do so on a 20-amp source because the instructions called for 30. I guess we choose to reduce the risk of a damaging voltage sag, blowing our host's 20 amp breaker, or pushing some electrical part or cable until it gives up and "lets the smoke out." That said, we realize our heat pump is on a 20 amp breaker behind a 30 amp breaker, and as a result it's quite unlikely that our heat pump alone would ever draw more than 20 amps.

(2) We have a post-it note right by Rocinante's thermostat that reminds us to turn off the electric hot water heater and maybe even the microwave before we try to start the heat pump. Without this reminder it's quite easy for us to pop the 30 amp breaker, even though the 20 amp breaker for the heat pump has never blown. So there are plenty of forgetful moments when a trailer with 30 amp service could easily draw more than 30 amps just long enough to pop the main breaker. Given this, we assume there would also be plenty of forgetful moments where we unintentionally draw more than 20.

Of course if you've a smaller heat pump / air conditioner, or just a much better memory for manually managing your trailer's overall power consumption to keep it below 20 at all times, you may be able to make the AC work for you on a 20-amp supply. YMMV, do what works for you, and let us know how it goes.

[Inland RV Center, In]

Originally Posted by J. Morgan

Save the ancient Armstrong A/C that came with my trailer, I "reengineered" everything. Every system, every wire, even my axle placement.

Respectfully, whether any of what I wrote above matters or not is moot, because separate from any opinion, even your air conditioner (if you have one), runs on a 20 amp breaker.

The question was whether a 30 amp circuit is NEEDED to run his AC, the answer is obviously no.

(FWIW, Wally himself was not an engineer)

FWIW X2, I take no personal offense whatsoever when I debate, I endeavor to debate the issue, not the person. No heartburn on my behalf)


Superat stultitia.

Maybe, maybe not.

You are correct IF nothing else is running.

But, if the Univolt is doing a big charge, then it's current draw and the start up current for the AC, would most likely blow a 20 amp breaker. Still within the trailer, everything is normal.

Better to have a little extra available than to be on the short side.

When the 20 amp source breaker blows, then the trailer is being powered by 12 volts. Then when you reset the 20 amp breaker, it will blow again, because of the Univolt and start up current for the AC.

Certainly not a major concern, but not something to disregard either.

Andy

[BTB]

Earlier in this thread things got a little hot and heavy regarding the wisdom of presuming that just because one person ran an appliance ok at whatever amps, it must be ok to do it again going forward.

Beware of drawing conclusions from observed results. In a hot and dusty country to our south its firmly believed that drinking a cup of gasoline is an effective remedy for rattlesnake bite, based on observed results. Well, gasoline is totally ineffective, so how come its "observed to work"? Something like 40% of the time, a rattlesnake doesn't inject any venom when biting humans. In those cases, people don't get envenomated and don't get sick (from any venom, anyway!), hence the observation that the gasoline treatment "works".

When it comes to electricity, I rely on those engineers - their designs, and their rules of thumb!

[J. Morgan]

Likewise, all knowledge is based upon observation and compound knowledge is built upon the interactions of observed phenomena.

To arbitrarily discard the value of observation is to disregard practically all knowledge not assigned to pure instinct.

Assuming that the 20 amp circuit is up to code and in good service, and assuming that the cords and adapter are up to the task of carrying 20 amps, the implications associated with running a trailer accessories in excess of 20 amps is going to be limited to the damage that a tripped circuit breaker can impart.

Superat stultitia.

[Rocinante]

It gets more exciting if someone uses a 15 amp extension cord between two 20 amp breakers.

[bsmith]

My 1976 Sovereign is parked 75' from its power source. I have been using a 25' 30 amp cord connected to a 50', but the connectors between the two cords overheat. Will a single 30 amp 75' cord solve the overheating problem, and if so, what size and spec cord would be optimum? (Parking the trailer closer to the power source is not an option.)

[OTRA15]

Originally Posted by bsmith

My 1976 Sovereign is parked 75' from its power source. I have been using a 25' 30 amp cord connected to a 50', but the connectors between the two cords overheat. Will a single 30 amp 75' cord solve the overheating problem, and if so, what size and spec cord would be optimum? (Parking the trailer closer to the power source is not an option.)

Welcome to the forum! Hot down there in Texas?

All extension cords carry a number for their American Wire Guage (AWG) size. And there are tables for choosing the proper extension cord, depending on the amperage load and distance from the outlet.

What is the AWG number of each of your two cords? Is your outlet at the source a proper 30 amp outlet with its own 30 amp circuit breaker?

I don't have the correct tables with me right now, but I am guessing you need at least a #10 AWG 75' cord, and perhaps a #8, in one continuous length with no connectors/plugs in the middle. Will look up tables later if no one else does so in the meantime.

Are you pulling 30 amps in usage in the trailer with AC, microwave etc.?

[Lumatic]

Originally Posted by bsmith

My 1976 Sovereign is parked 75' from its power source. I have been using a 25' 30 amp cord connected to a 50', but the connectors between the two cords overheat. Will a single 30 amp 75' cord solve the overheating problem, and if so, what size and spec cord would be optimum? (Parking the trailer closer to the power source is not an option.)

I'm not an electrician but do know enough to be dangerous. So maybe an electrician can chime in here. If the male female extension plug is overheating there is a good chance there has been some arcing. If you are considering a 75' power cord anyway (which will be expensive) how about cutting off the plug ends and splicing it together? Needless to say the longer the run, the more resistance and consequently the more heat. 75 feet is pretty long, maybe too long.

[J. Morgan]

Where there is heat there is resistance.

I would run all 30 amp cords.

Whatever is getting hot should be replaced IMHO. It might me dirty or corroded contacts, or it might be substandard adapters. ( if you are running adapters )


Superat stultitia.

[Lumatic]

Originally Posted by J. Morgan

Where there is heat there is resistance.
Superat stultitia.

"Resistance is futile" The Borg