air conditioner - generator woes

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ElginRinger

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I acquired a new generator a couple weeks ago and had a chance to put it to work this past weekend.  Before I pulled the TT to my destination I decided to crank up the generator and make sure what needed to run, would run.  In my driveway at home, I connected the generator to the TT, turned on the gen and then turned on the AC.  Everything worked fine.  The A/C was on max, I had a few lights on and it kept running without fail.

Well, once I got the TT to my destination this weekend the AC would run awhile and then trip the circuit breaker on the gen.  I went through normal shutdow as in turning the ac back off flipping the circuit breaker back to on.  Again, it would run a bit more and then trip again.  Any thoughts on what I may be doing wrong or something I overlooked ??

My setup is a 1977 Yellowstone TT with roof top air and my generator is a Troy Built with 4000 continous, and 5500 surge.

Thanks for all your time.
 

John From Detroit

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A Troy built 4000 should be able to run one ac with enough left over to run one more AC on most RV's, so long as they don't both kick in at the same time.

Several things affect the way things work.  For one, at home it's likely your trailer batteries were full up, once at your destination this may or may not have been the case  My converter can put out right about 1,000 amps and needs about a 50 percent bonus on the input so if the batteries were down it might be taking nearly as much power as an AC unit.

Another thing is temperture.  AC's need more power the hotter they get  The reasons for this are complex but basically it's the same reason your heart works harder when you have high blood pressure (And trust me, when it pops it's breaker,,, NOT GOOD)

Higher pressures in the AC's cooling system is caused by heat.  This means the heart of the AC (The compressor) has to work harder and just like the hypertensive person,,, That takes more power  The difference is it is not so bad when it tripps its breaker

Finally there is your extension cord.  Long cords = greater voltage drop = higher current in a compressor
 

ElginRinger

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John In Detroit said:
A Troy built 4000 should be able to run one ac with enough left over to run one more AC on most RV's, so long as they don't both kick in at the same time.

Several things affect the way things work.? For one, at home it's likely your trailer batteries were full up, once at your destination this may or may not have been the case? My converter can put out right about 1,000 amps and needs about a 50 percent bonus on the input so if the batteries were down it might be taking nearly as much power as an AC unit.

Another thing is temperture.? AC's need more power the hotter they get? The reasons for this are complex but basically it's the same reason your heart works harder when you have high blood pressure (And trust me, when it pops it's breaker,,, NOT GOOD)

Higher pressures in the AC's cooling system is caused by heat.? This means the heart of the AC (The compressor) has to work harder and just like the hypertensive person,,, That takes more power? ?The difference is it is not so bad when it tripps its breaker

Finally there is your extension cord.? Long cords = greater voltage drop = higher current in a compressor

Thanks for the information.  I don't have a battery set up on my trailer so it's not that.  I can buy the temperature theory.  I checked the AC in the driveway at home in the late evening, but I'm still in Texas so it was pretty warm.  But, going back to your answer "A Troy built 4000 should be able to run one ac with enough left over to run one more AC on most RV's, so long as they don't both kick in at the same time"  I'm only running one and when it runs, it gets cold.  As for cord length, it was about the same length out as it was at the house.

I don't know what the answer is but I feel pretty lost if this generator that I was told should have no problem running my AC, doesn't run my AC.  I guess it's possible there is a problem with the AC ???
 

Bob Buchanan

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ElginRinger said:
Well, once I got the TT to my destination this weekend the AC would run awhile and then trip the circuit breaker on the gen.? I went through normal shutdow as in turning the ac back off flipping the circuit breaker back to on.? Again, it would run a bit more and then trip again.? Any thoughts on what I may be doing wrong or something I overlooked ??

What was the altitude of the destination? There's a Genset power lose formula that I don't have off the top of my head, but it's something like 10% lose of power for each 1,000 feet above X number of feet. So if up? high enough, you may have a 3000 Genset vs. a 4000. It was probably tripping when the A/C compressor kicked in and/or you put on a pot of coffee.? :(
 

Gary RV_Wizard

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Get the trailer somewhere that has 30A shore power and run the a/c on max for awhile while connected to shore power. See if it trips breakers running that way. If it does you have an a/c problem; if it does not the problem is likely elsewhere.  If the a/c has an internal problem and is overheating or overloading, it should trip the branch circuit breaker for the a/c before tripping the main 30A supply breaker.

Since you say you tripped the breaker on the genset, it sounds as though the problem is in the total load on that circuit.  What size is the breaker on the genset?  Typically they will have  a couple of 15/20 amp 120 VAC outlets and maybe a 240 VAC as well.  Did you simply plug the entire trailer into one of the genset output receptacles? If it's plugged into a 15A outlet, you can only draw 1875 watts through that outlet even the the genset has more total capacity than that. 1875 may be marginal for an older a/c unit whose efficiency has gone way down. The max is 2400 watts if it's a 20A outlet.  Check your genset to see how much power you can pull on each of its available outlets. One maybe rated higher than others, but on lower priced models that often is not the case.

Also, what else was powered on in the trailer?  Coffee pot maybe?
 

John From Detroit

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RV Roamer said:
John: That's not a converter - that's an arc welder!  Or did you perhaps slip an extra zero in there?  ???

No, not an extra zero, an wrong word,  I meant 1,000 WATTS,  Sorry (that is about 80 amps btw)
 

Karl

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The Troy-Bilt site lists 3 generators; 3550, 5550, and 8000 watt. The 3550 has 2-single pole c.b.'s rated at 15 amps each (one for each 2 outlets), so it's entirely possible that the combination of starting and full load run may trip it if your wire size is too small or too long. The 5550 has a double pole 20 amp c.b. ganged for all outlets, so an overload on one leg will take out the other leg too. I don't see any gensets rated at 4000 watts. What is the model number?
 

ElginRinger

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Karl said:
The Troy-Bilt site lists 3 generators; 3550, 5550, and 8000 watt. The 3550 has 2-single pole c.b.'s rated at 15 amps each (one for each 2 outlets), so it's entirely possible that the combination of starting and full load run may trip it if your wire size is too small or too long. The 5550 has a double pole 20 amp c.b. ganged for all outlets, so an overload on one leg will take out the other leg too. I don't see any gensets rated at 4000 watts. What is the model number?

Good gosh.  I don't know why I said Troy Bilt, I have a Briggs and Stratton XL4000.  Sorry for all the confusion on that front.  When I got the generator, I found that the power cord from the trailer did not work in the 120/240 volt ac, 20amp locking receptacle.  So, I got a pigtail with a three prong female that would accept the 3-prong male from the trailer.  I then got a NEMA L14-20, 3-prong that would fit into the locking receptacle.  I'm wondering if I should have got a 4 prong to fit into the generator.  Since it was a 3-prong, doesn't that make it a 120 ??  Wouldn't 240 run the ac, and more ??  I'm sorry for all the questions, and the sketchy scernarios, I'm just not very electrically inclined and I don't want to set my tt on fire by putting too much juice into it.  Thanks again for you patience and help.
 

John From Detroit

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The 4 prongs of a 240 volt outlet are 120-0 0-120 (note if you hook across these two you get 240) Zero (of course) and safety ground.

Another way to say that is Hot - neutral - hot and ground  or  120-0-120 and ground

The problem is that older days used only 3 terminals,,  120-0-120 

If you hook to the outlet wrong you get 240 where you want 120 and that is not a good thing

Trust me (Power company did it to me) It's not a good thing
 

Gary RV_Wizard

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When I got the generator, I found that the power cord from the trailer did not work in the 120/240 volt ac, 20amp locking receptacle.  So, I got a pigtail with a three prong female that would accept the 3-prong male from the trailer.  I then got a NEMA L14-20, 3-prong that would fit into the locking receptacle.  I'm wondering if I should have got a 4 prong to fit into the generator.  Since it was a 3-prong, doesn't that make it a 120 ??  Wouldn't 240 run the ac, and more ??  I'm sorry for all the questions, and the sketchy scernarios, I'm just not very electrically inclined and I don't want to set my tt on fire by putting too much juice into it.

A three prong plug on your trailer indicates that it does not accept 240V power. It is almost for sure a 30A, 120V plug. It can be identified by the two angled pins (as opposed to the parallel pins on a standard household120V/15A  plug. A 240V plug has 4 pins.  So, you must stick with the 3 prong plug and 120V from the genset. That probably limits you to 20A from it.

 

ElginRinger

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RV Roamer said:
A three prong plug on your trailer indicates that it does not accept 240V power. It is almost for sure a 30A, 120V plug. It can be identified by the two angled pins (as opposed to the parallel pins on a standard household120V/15A? plug. A 240V plug has 4 pins.? So, you must stick with the 3 prong plug and 120V from the genset. That probably limits you to 20A from it.

So, to me it sounds like there is a problem elsewhere that is making my breaker flip.  Everything I've read on here says that my generator should power my ac and almost another.  Where could the other problem be ?  It sounds like I have plenty of generator.  When I've been to rv parks there's been no problem running the ac plus othe appliances.  Thanks for you help, again, and again.
 

Karl

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Here's a LINK to the PDF document of the owners' manual. Basically it says that the two duplex outlets are limited to 15 amps each at 120 volts, and the 4-prong 120/240 outlet is limited to 16.6 amps at 120 or 240 volts for 2000 watts and 4000 watts respectively. It also lists the starting load of a 10,000 btu air conditioner as 1800 watts (1200 watts running), so it isn't too surprising that the c.b. kicks out after a short time (1800 watts is 120 volts X 15 amps - the maximum). Chances are good that your a/c is larger than 10,000 btu's, so the starting and running load could very well be too much for the c.b. to handle and because they are duplexed, tripping one will trip the other also. You could parallel wire the 2 duplex outlets together so they share the load across the two c/b's, but I don't recommend such modifications and wont provide the (simple) details of how to do so because of the potential liability. The duplex outlets are the GFCI type, and I don't know how paralleling them would affect their operation. That said, I personally would do it if necessary, but you have to decide that for yourself.
 

ElginRinger

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Karl said:
Here's a LINK to the PDF document of the owners' manual. Basically it says that the two duplex outlets are limited to 15 amps each at 120 volts, and the 4-prong 120/240 outlet is limited to 16.6 amps at 120 or 240 volts for 2000 watts and 4000 watts respectively. It also lists the starting load of a 10,000 btu air conditioner as 1800 watts (1200 watts running), so it isn't too surprising that the c.b. kicks out after a short time (1800 watts is 120 volts X 15 amps - the maximum). Chances are good that your a/c is larger than 10,000 btu's, so the starting and running load could very well be too much for the c.b. to handle and because they are duplexed, tripping one will trip the other also. You could parallel wire the 2 duplex outlets together so they share the load across the two c/b's, but I don't recommend such modifications and wont provide the (simple) details of how to do so because of the potential liability. The duplex outlets are the GFCI type, and I don't know how paralleling them would affect their operation. That said, I personally would do it if necessary, but you have to decide that for yourself.

Looks as though I might qualify for the "stupid things I've done" forum if we ever get one on this forum.  I would hate to think I bought a generator that was too small for my needs................  Thanks for your help.
 

King

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I think the only way to get 4000 W from the generator is with a 240V load.  I don't think you CAN parallel the 120 outlets to get 30A at 120V since the same windings most likely are used for the 120 outlets as the 240.  They are just phased 180 deg different.  I think the absolute maximum you can put into a single 120V load is 2000W.
Art
 

Gary RV_Wizard

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So, to me it sounds like there is a problem elsewhere that is making my breaker flip.  Everything I've read on here says that my generator should power my ac and almost another.

No, just the opposite. We are saying you essentially have a 15-20 amp, 1875-2400 watt  generator, because you can draw power only from a single 120VAC outlet. That limits your power to substantially less than the genset's 4000 watt max output.

But you ought to be able to run the a/c with little or nothing else running at the same time. Try it with everything else powered off and see if you trip a breaker. The a/c alone should not exceed 15 or at worst 20 amps.  Look at the a/c breaker in your RVs load center and see what it is rated for - your a/c isn't using more than that or the trailer's own breaker will trip.
 

Karl

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Agree Gary,

The problem is that the genset is breakered at 15A on each of the two duplex outlets, but they're ganged so an overload on one leg will take out the other too. One outlet should be able to handle the a/c and the other can be used for another 15A max. load. A heavy duty extension cord should do the trick for the other plug-in devices. Better still, If he uses the 4-prong (240V) receptacle for the a/c which is probably wired into the breaker panel directly, he'll need to use the duplex outlet from the other 120V leg for the other appliances. Easy enough to figure out with a voltmeter. With the TT plugged in and the generator running, plug the extension cord into one of the outlets and measure between the hot side of the breaker box and the hot pin of the extension cord. If you get a reading of around 120V, the cord is plugged into the wrong outlet. Switch it and you should read around 240V between the two hots. This is correct. The reason I suggest using the 4-prong outlet and one of the duplex outlets is that the duplex outlet is GFCI protected while the 240V plug is not, but because it's only powering the built-in a/c, shock protection isn't as big a concern.
 

ElginRinger

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Elgin, Tx
Hi Ya'll, I'm posting again on a topic that we visited last year.  In the earlier threads you'll see that I had a problem with the breaker tripping on my generator when the ac cycled on my 1977 Yellowstone TT.  Well, I've still  got the same generator, but I've replaced the boat anchor with a brand new 31.5' Jayco Jay flight 5'er.  Sweet!  Well, that's until I hooked up the generator, flipped on the AC, and, yep, flipped the breaker on the gen, again.  I looked up the specs on my AC and it said that it would draw 16.5amps on start up, and 13.5 continous.  There was nothing else on in the trailer.  Would I be correct in suspecting that I'm just not getting a true 20amps from the generator ??? It's not even a year old.  I have one 20amp, and two 15amp duplexes on the gen and I was plugged into the 20amp twist lock.
 
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