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Old 05-26-2009, 11:00 PM   #15
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. . . So my question is: how low of AC voltage is too low?
Have you looked at the product specifications in your Carrier air conditioner owner's manual to see if the manufacturer specifies a safe voltage operating range for the A/C? If so, then I would recommend not operating your new A/C with AC voltage lower than the low end of the safe operating range specified by Carrier.
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Old 05-26-2009, 11:24 PM   #16
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Hi, my house is wired for 20 amp wall sockets and 15 amp light switches and ceiling lamps. I have no problem running my a/c from my house using a 15 amp dog bone plugged into a 20 amp socket. I have a have had several airconditioners in my house. Portable and window type in several sizes. and even had a brown out once in-which my a/c wouldn't cycle. I turned it off and got out my multimeter and tested voltage. My voltage was clear down to 88 volts. I had no damage, but as mentioned earlier, if you have a loose or bad connection enough to burn or melt your plug, that will cause your unit to burn out at any voltage, not just low voltage. Also most will run their a/c with a portable generator with a 15 amp dog bone and less than 30 amps without problems. I see no problem if you have a good tight, clean connection plugged into a house. [Note: use a dog bone, not an extension cord]
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Old 05-26-2009, 11:38 PM   #17
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Look, - this is simple. Lower than about 110 volts and you are in the danger zone of a locked rotor in your AC unit. End result, up to 3 times the current draw and the possibility of burning up the windings before the thermal overloads can kick in. It is an induction motor which is dependent on the voltage supply to it to do its job. If the voltage is not there, you are in danger of frying your AC unit.
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Old 05-27-2009, 06:05 AM   #18
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in reference to the dogbone available to convert a welder plug to RV...

Sweet. Now that's something I can work with! I've tried wiring my own plugs before and failed miserably, so a pre-made one is the ticket. I'll keep an eye out for that next time I'm at the camping store. I've already bought one to convert 50A 120V RV current to 30A 120V, but I'll look for the welder to 30A 120V.
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Old 05-27-2009, 06:20 AM   #19
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If there is 105 volts at the trailer, there must be 105 volts at the house, OR, the cord is too small in size and is too long causing a voltage drop. I am electrical contractor for 30 years and wouldn't run a drill on a 100' cord less than a number 12. If the A.C. draws 22 or 23 amps the wire feeding it should be a number 10 fused at 30 amps. A number 12 wire is rated for 20 amps and would heat slightly drawing 23 amps and would trip a breaker. A 20 amp circuit should only be wired to supply 80% of its capacity or 16 amps. If there is 105 volts at the A.C. and it is rated at 23 amps the actual amp. draw is closer to 27 amps, a fairly dangerous situation if it is connected to anything smaller than a number 10 wire.
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Old 05-27-2009, 06:51 AM   #20
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Well don't give up yet!

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.
Hey mark I think his major problem is when he visit's his in laws they don't have the proper outlet to give him 30 amps to run his trailer. DO you have a generator? If so you could use the 30 amp twist plug and wire for one circuit so your using 120 volt not both for 220 volt. Although it might be intrusive sound wise .
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Old 05-27-2009, 08:11 AM   #21
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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.
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Old 05-27-2009, 08:26 AM   #22
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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.
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Old 05-27-2009, 08:40 AM   #23
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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
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Old 05-27-2009, 08:43 AM   #24
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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.
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Old 05-27-2009, 01:13 PM   #25
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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,
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Old 05-27-2009, 01:35 PM   #26
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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
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Old 05-27-2009, 02:08 PM   #27
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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
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Old 05-27-2009, 06:35 PM   #28
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Try this, Mark.

Voltage Drop Table
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