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markdoane · 05-27-2009, 07:11 AM

Jason,

Depending on the welding outlet you have, you might be SOL. If your outlet is just a straight 240v - 50a, you won't find a proper dogbone to adapt to 30a. If you have a split phase welding outlet 125/250v - 50a then a dogbone will work fine. The 50a receptacle needs to have four holes.

Wingeezer · 05-27-2009, 07:26 AM

Quote:

Originally Posted by Inland RV Center, In

Running an AC at 105 volts, will put you in the market for another AC, sooner than you think.

When an AC runs on low voltage, it's current draw actually increases. That in turn, is making the compressor work even harder, until it decides "enough" and then burns up.

The answer is easy. When the AC voltage will be low, "DON'T".

Andy

Andy,

Not disagreeing at all with what you say, but don't the AC units have a
self-resetting trip device built in that protects the unit from this condition?

When we first started using trailers many years ago, I experienced that on out first trip. It was extremely hot out and suddenly our AC stopped working. I didn't much about these things, but did check the line voltage & it was down around 100v.

I figured that was the cause of the problem and that our AC was now probably toast.

I was very happy to find that a couple of hours later, the AC was operative again and seemed fine. We used it many years afterwards without a problem. It was a Dometic AC I believe.

Do they not all have this type of protective feature?

Brian.

Inland RV Center, In · 05-27-2009, 07:40 AM

Quote:

Originally Posted by Wingeezer

Andy,

Not disagreeing at all with what you say, but don't the AC units have a
self-resetting trip device built in that protects the unit from this condition?

When we first started using trailers many years ago, I experienced that on out first trip. It was extremely hot out and suddenly our AC stopped working. I didn't much about these things, but did check the line voltage & it was down around 100v.

I figured that was the cause of the problem and that our AC was now probably toast.

I was very happy to find that a couple of hours later, the AC was operative again and seemed fine. We used it many years afterwards without a problem. It was a Dometic AC I believe.

Do they not all have this type of protective feature?

Brian.

Brian.

Your absolutely correct.

But, that built in self resetting circuit breaker opened, because the currect draw was excessive, which quickly also overheats the compressor.

If you tried to put your hand on top of a running compressor, you will find that it is normally cool to cold.

When you run an AC on low voltage, the top of the compressor becomes "HOT."

Why?

Because you have caused the compressor to draw more current than it should, and is trying to break down.

I assure you, running an AC with low voltage will cause you to do without it, faster than you wish.

The fix, is called replacement.

You cannot abuse electric motors of any kind.

The reward is always failures, up to and including locked up bearings, because they overheated.

But, to each his own.

Andy

SilverRanger · 05-27-2009, 07:43 AM

Quote:

Originally Posted by markdoane

You actually have 50 amps of 120 v for each leg. You can indeed make an adapter with a 50a welding plug on one end and a 30a receptacle on the other end. It will give you a full 30a at 125V.

In fact, Camping world will sell you one ready made.

I just had 50 amp service installed (for $650), and use a ready made adapter $12) to convert to 30 amp service. It works great. I got the 50 amp for some future courtesy parking (I still have some trees to remove), and for some welding. Both the voltage meter incorporated into my APS surge protector, and a digital plug in type that measures voltage and cylcles, indicate only a very slight voltage fluctuation when the AC compressor cycles on.

MarkR · 05-27-2009, 12:13 PM

Great Thread.

Say my trailer is 50' (or 100' or "x" feet) from the my House's Elec. Service Panel (and there is space/room on my panel for an additional circuit). Is there a formula for sizing the wire so it ends up as a legitamate 30amp circuit, or is it a "rule of thumb"?
And are there 30amp circuit breakers (dumb question, I know, but I only recall seeing 15 and 20's)?
Thanks,
MarkR

Gene · 05-27-2009, 12:35 PM

Yes, Mark, there are formulae (sorry, old school here and I just have to use the Latin plural) for determining voltage drop and how thick the wire. The lower the number in American Wire Gauge (AWG), the thicker. I have no idea where my tables are, so I'm not a lot of help, but someone will probably post it or go looking on the internet under "voltage drop" where there are a lot of hits for calculators plus a Wikipedia article.

It's voltage drop that is the problem with long cables. A lot of those orange ones are 14 AWG which is for 15 amps and it's too small for an AC. 12 AWG is 20 amp, but voltage will drop as the cable gets longer and longer. The one that comes with the trailer is 30 amp and you know how heavy it is—I think it's 10 AWG for 30 amp. It's also expensive if you've seen them in stores. Mohos often use 50 amp cable and I imagine it's 8 AWG and even more espensive. The appliance will draw the amps that are available at the breaker regardless of voltage to provide the wattage necessary to run. Low voltage means too many amps, strain on motors and compressors, blown breakers. I'm sure a real electrician will correct me if I got this wrong and tell us just what cable is best for 100' from a receptacle. If you use a 12 AWG 100' cable with an adapter to the trailer cable, you are going to have issues, I would think.

There are 30 amp breakers for 120 and 240 v. Look carefully and you will find the 120 v. ones which are less common than the 240 v ones. The 240 v ones are for dryers. I recall I had to go to a couple of stores before I found it. Don't use a 240 v one, it's a different animal.

Gene

Inland RV Center, In · 05-27-2009, 01:08 PM

Quote:

Originally Posted by MarkR

Great Thread.

Say my trailer is 50' (or 100' or "x" feet) from the my House's Elec. Service Panel (and there is space/room on my panel for an additional circuit). Is there a formula for sizing the wire so it ends up as a legitamate 30amp circuit, or is it a "rule of thumb"?
And are there 30amp circuit breakers (dumb question, I know, but I only recall seeing 15 and 20's)?
Thanks,
MarkR

Mark

When it comes to electricity, the only rule of thumb is, if you mess around with it, your going to get shocked, and you will hear all kinds of music.

There are many different formulas that are industry standards.

When you use an extension cord, a maximum voltage drop of 2 percent is a guide to never exceed.

At 30 amps and with a 50 foot extension cord you should use a #8 wire. At 20 amps, a #10 wire.

At 30 amps and with a 100 foot extension cord you should use a #6 wire. At 20 amps, a #8 wire.

These are absolute minimums.

To be safer, you should increase each of the above sizes, to the next larger size.

Andy

SilverRanger · 05-27-2009, 05:35 PM

Try this, Mark.

Voltage Drop Table

**Kevin245** · 05-27-2009, 06:36 PM

Voltage Drop can be calculated several ways:

Using Ohms Law

Voltage Drop = Current In Amps x Resistance in Ohms

Or you can use this following typically formula:

Voltage Drop = K x 2 x Wire Length in Feet x Current in Amps
Wire Area in Circular Mils

K = Specific resistivity in ohm – circular mils / foot
K = 11 for copper in circuit loaded less than 50% of capacity
K = 12 for copper wire loaded aluminum wire in circuit loaded to 50 to 100% of capacity
K = 18 for aluminum wire

Another interesting tidbit. If the line voltage doubles (say 120 to 240) the voltage drop decreases by a factor of 4.

**Kevin245** · 05-27-2009, 06:41 PM

The forumal is supposed to be K x 2.... over Wire Area in Mils... but it won't align as formatted for some reason...

bibbs · 05-27-2009, 07:22 PM

Just get the largest gauge cord you can find #10 would be great,plug it into a kitchen or laundry outlet [20 amp] with your adaptor,run it for 30 mins, then feel ithe cord and plug see if its warm or hot.If its hot-----you better not---My old 75 ac runs fine on a 50' 12 gauge cord.You never told us what gauge cord you were using.A larger size can make a HUGE differance. Try it you will be happy

Bibbs

WineStream · 05-27-2009, 08:35 PM

whew! a guy goes to work for the day, spends some time working around the house, then time w/ family and then reads the threads before bed; and whoa!

My welder outlet (remember, I'm electrically dumb) is a 3 prong. Not sure what that means with relation to making a 120v 30a conversion, but that's what I got and the welder works just fine w/ it.

Yes, I do have a generator, but it wouldn't be suitable for travel, much less the noise it makes. I've got a 6500W generator that is a my backup for the whole house when the power goes out (yeah, that's a common occurrence here, especially in winter, and I don't like $^%#@* freezing up nor my deep freeze thawing out). The thing is on a cart...not exactly portable to a campsite nor is it quiet. Funny story though...it is a 220v generator (needed that for my well pump). It has a 4 prong 220v on it and when I'm using it, I back-feed its power to the house via my welder outlet in the garage. Being electrically stupid, I didn't know what I was doing but I wired it up anyway. Funny, some lights in the house were REALLY bright. Later, I corrected that. Now it works like a charm. But back to topic...

So when I tested my AC in the AS, I was juicing the AS with (yeah, I know a lot of you will cringe) a std. orange 100' ext. cord...yeah, the 14AWG variety. But, I knew I wasn't going to run the AC long. It was just a test. So the breaker for the outlets in the garage is 15A at the box in the basement; if I flicked on the AC in the AS drawing through a 15A circuit and didn't blow the breaker and still maintained 105V in the trailer through a 100' 14AWG cord...isn't this a good sign? As in: if I were connected to a 15A outlet via, say, a 12AWG cord that was only like 25' long that I might be in good shape? Or better yet I get close enough that my umbilical is long enough and then I use a thick-gauge 15/20A to 30A conversion dogbone? Seems good enough in my hillbilly logic.

Regardless, I think that a 15/20A plug at my relatives' house is going to be my only option. I'm banking on a nice breeze, but still bleeding dumb electrical ideas just in case.

markdoane · 05-27-2009, 09:59 PM

Jason,

I hope you have a nice cool breeze, because frankly some of your ideas scare me to death. I recommend you hire a good electrician before you try anything on your own.

Really, experimenting with backfeeding 240 through a welding outlet? No neutral?

I wouldn't post anymore of your ideas in case your insurance underwriter is reading this.

WineStream · 05-28-2009, 05:39 AM

There's no experimenting. It's set up and it gets used regularly. If I'm doing wrong by that then you better start a crusade through rural central Ohio because I am not the only one. As a matter of fact, when the power is out for long periods of time, you can step outside and hear the hum of generators all over the place. When you are without power for 3-4 days sometimes; you can't just go away and come back when the power is back on. People that have big farms, especially with livestock, can't go more than a few hours without electricity without starting to lose major $. The way I set things up is how most people who already have a large-amp outlet somewhere at their house do their connection to a generator.

Granted, a lot of what I post is just food for thought. I post to see what the reactions of people are. A lot of people have one idea of the way things MUST be. That's not me. We must remember that many of the discoveries in this world have been via chance experimentation or accident. If we don't try and wonder, then we don't learn.

So to tie everything together in this thread...again back to the original topic: how low is too low AC voltage? This question has not been definitely answered because there's no real right or wrong answer, but I was looking for experience of someone who broke / blew up something on their own that knew what their voltage was at the time. Some people have responded that they go lower than 100V with seemingly no problems. Some have said they use extension cords without issue. Some have taken the hard line of "give me 115V or give me nothing". And that's fine. But like everything there's a tolerance band. For example, your tires: typical load range E tires have a max pressure of 80psi. So like to run 50, some 60, some 70, some 80. Some vary thier pressure based on load. Some don't even thing about the pressure unless they see something visually wrong with the tire. I can go through numerous other examples but the point is that each person has a comfort zone. Based on where I live and what I must be prepared to deal with, my tolerance band is generally pretty wide on lots of things. You can't take the hard line against mother nature.

And for the record, I know my insurance agent personally and he's very happy that I have a generator. The first time there was a major outage and he had to pay me a lot of money...he was happy to hear that I got a generator after that.

markdoane · 05-28-2009, 06:01 AM

Jason,

I don't mind that you use a generator. I don't even mind that you backfeed through a large amp outlet. I really mind that you do it right. If you feed split phase power through a three prong outlet, you're using your ground wiring for neutral. Please put in a four prong outlet.

While I'm sure your insurance agent is happy, I doubt that the underwriters would feel the same way.

richinny · 05-28-2009, 04:46 PM

the information on the spec sheets for your air cond. unit. do you have a model number of the unit?

WineStream · 05-28-2009, 06:33 PM

Ricky...thanks for reminding me. I looked that up. It's a Carrier AirV (the standard model, w/ heat strip). When running the AC it's drawing max 12.8A. Ironically, but it makes sense I guess, when running it on heat mode it draws 13.8A. So, if I do the math that I think I understand from being told on the forums before anytime I've asked electrical questions: 115V x 12.8A = 1472W. Therefore, at 105V, I'm drawing 14.0A (max) which in turn would not trip the breaker. As for the 100' cord, yeah, bad idea for sure. But, it was for testing purposes, not long term use.

So, I'll go to my relatives' house prepared for boondocking and hope that I can get close enough to an outlet that perhaps I can draw enough current (safely) to run the A/C at least to put a chill in the AS as we're all trying to drift off to sleep.

richinny · 05-28-2009, 07:50 PM

i think you're blending can with should in respect to survival of the equipment. while even if you had the amp capacity, if the voltage drops too low, you still operate the unit beyond its designed limits.

you understand about cords now, so you know that wiring, connectors and cords can all become unwilling fuses that 'blow' in an unsafe manner.

one other thought is one of those portable air conditioners. i think they draw less than the roof unit but you would still need to maintain voltage at a safe level.

richinny · 05-28-2009, 07:56 PM

the best answer will come from the manufacturer :-)

Carrier Transport Air Conditioning
715 Willow Springs Lane
York, PA 17402
Ph: 1-800-673-2431
Fax: 1-717-764-0401

http://www.penndda.com/carrier/pdf/c...V_Brochure.pdf

Gene · 05-28-2009, 09:56 PM

Jason, where do you get 115 v.? Taking an average of 110 and 120? Does it makes it closer to 105? I think you're bending the numbers to talk yourself into something. I hate sleeping in the heat—I don't sleep well and if I were in a trailer I'd sure want to run the A/C. Sometimes you can't, or you can get away with it for a while, but you are straining the unit and will shorten it's life. You won't know why it lasted several months or a year less than the average A/C, but it could be because of pushing the limits.

The A/C is designed to operate at 120 v, but will operate at more or less because power companies do not provides exactly 120 v., so there's some range of voltage that's ok, but then you get into a grey area and efficiency drops faster and faster. My power company used to provide a little more than 117 v., but they've improved the distribution system and they are now closer to 120. The further you get from 120 v., the less efficient appliances and electronics become.

That 12.8 amps is probably the normal amps once the unit has started. It will draw considerably more when the compressor is starting. Anyway, optimal is 120 x 12.8 = 1,536 watts. And not tripping the breaker does not mean you aren't damaging the A/C .

Gene