50 amp power management

[jcussen]

Kirk,  believe at least 95% of motorhomes and tt's use 13500 or 15000 btu air conditioners. The most efficient one I have found is the new Coleman Mach 3, 13500 at 11.2 running amps which is better than my one year old Dometic 13500's, but think breaker would still trip when second unit lit off, as starting amps are likely over 22.  Soft start kits I have seen are several hundred dollars each, so they would be a last resort. If you know of a 13500 or 15000 that does use 8 amps, they may work and I would appreciate the brand and model.

https://www.airxcel.com/DesktopModules/RVProduct/Pdf/mach_3_ps.pdf

[Kirk W]

51 minutes ago, jcussen said:

believe at least 95% of motorhomes and tt's use 13500 or 15000 btu air conditioners.

In larger RVs I am sure that you are correct but in smaller RVs you can find a Dometic 10,500 BTU as it is what we have now.  My current unit is listed as 8a. I see that I did attribute that 8a to a 13,500 unit but can't find one now so could be the little brother. 

[jcussen]

4 minutes ago, Kirk Wood said:

In larger RVs I am sure that you are correct but in smaller RVs you can find a Dometic 10,500 BTU as it is what we have now.  My current unit is listed as 8a. I see that I did attribute that 8a to a 13,500 unit but can't find one now so could be the little brother. 

Thanks for the input, guess there is no magic bullet here. I use the coach for a guest house here in Texas in the summer and need the two ac's. I was trying to avoid changing my 30 amp wiring and plug, because I am cheap, but guess I will have to rewire to 50 amp.

[oldjohnt]

4 hours ago, jcussen said:

 but if campground has a 30 amp breaker and I do not have a "soft start unit" on my ac's, I do not see how different wiring, or an HACR breaker, will prevent the campground 30 amp breaker from tripping when one ac is running and the other one tries to start, If you know this, please tell me.

Good evening jc, good questions.

I was talking about RV panel breakers in an attempt to answer your questions (how an HACR may allow short term start up current without tripping) and I seriously doubt the RV park pedestal uses HACR breakers. If the RV pedestal uses a standard 30 amp thermal magnetic circuit breaker there's no way it can supply 29.5 amps for very long before its "thermal" will trip and as I said 29.5 amps of continuous current  requires a minimum 40 amp supply NOT what the 30 amp RV pedestal (or even the RV panel) can deliver.

SO YOURE RIGHT different wiring or even an HACR breaker isn't gonna solve the problem. It looks like a 30 amp supply (even with soft or solid state or timers etc) just isn't gonna be sufficient to run TWO AC's that draw 29 amps SORRY, and that doesn't allow for the initial high start up surge current (perhaps 4 to 6 times the run current) when the AC starts. That's  where an HACR breaker may allow an AC to start without tripping, but still 30 amps is 30 amps and a standard 30 amp thermal magnetic or even an HACR  isn't gonna supply 29 amps very long..................

Its back to the drawing board lol 

Take care jc,  hope you had a Blessed Christmas and Happy New Year 

    

 

[Al F]

23 minutes ago, jcussen said:

Thanks for the input, guess there is no magic bullet here. I use the coach for a guest house here in Texas in the summer and need the two ac's. I was trying to avoid changing my 30 amp wiring and plug, because I am cheap, but guess I will have to rewire to 50 amp.

As a guest house, where you won't be running the microwave while both A/C are on, AND you are sure to run the water heater on propane when needed, there is no reason why 30amp service won't work. 

HOWEVER, be sure the wiring to the 30amp outlet you will plug the RV into is large enough to handle the FULL 30amps w/o a voltage drop.  If the wiring going to the plug is 12 gauge, or a fairly long run 10 gauge, you may need heavier wire to handle the load.

[jcussen]

7 minutes ago, Al F said:

As a guest house, where you won't be running the microwave while both A/C are on, AND you are sure to run the water heater on propane when needed, there is no reason why 30amp service won't work. 

HOWEVER, be sure the wiring to the 30amp outlet you will plug the RV into is large enough to handle the FULL 30amps w/o a voltage drop.  If the wiring going to the plug is 12 gauge, or a fairly long run 10 gauge, you may need heavier wire to handle the load.

Al, are you giving me new hope? Just how do you run 2 ac's on 30 amps?

[Kirk W]

42 minutes ago, jcussen said:

I was trying to avoid changing my 30 amp wiring and plug, because I am cheap, but guess I will have to rewire to 50 amp.

While some may get by using two a/c units on 30a power, I really don't think that you will regret the expense, once you recover from the pain of writing the check.  If you can do the work yourself, the cost shouldn't be too bad....  

[jcussen]

1 hour ago, Kirk Wood said:

While some may get by using two a/c units on 30a power, I really don't think that you will regret the expense, once you recover from the pain of writing the check.  If you can do the work yourself, the cost shouldn't be too bad....  

I can do it myself, but wire is expensive, more important, "some may get by using two ac units on 30a power"? Sure would like to be one of the "some".?

[richfaa]

9 hours ago, Second Chance said:

X2^^. Unbeknownst to us, our rig came from the factory with both ACs on the same 50 amp leg. ("Assume" is a dangerous word, but I can only assume that they were trying to balance with the washer/dryer we don't have on the other leg.) Anyway, we didn't have any problems for the first couple of years. Then, we stayed at a "resort ranch" in east Tennessee that had full hookups with 50 amp power (out in the middle of an absolutely beautiful pasture surrounded by mountains!). The row we were on was having low voltage problems on just one leg - but it happened to be the leg our ACs were on and our EMS kept taking us off-line or the breaker at the pedestal would trip when both ACs were running and the voltage dropped even further. The solution: unplug the rig, pull the breaker panel, switch around some breakers on the buses, and separate the two ACs on separate power legs. It fixed the problem at that location and we haven't had a problem since.

Rob

That is why I did that post however you and I are  apparently the only ones who  have had that happen  so there is no reason for anyone to check. We have not had a problem with both A/C running when on separate legs and we have them set up to both run . In fact they both ran most of last week here in Florida. We do have there start times staggered. We also have a W/D.

[jcussen]

Thanks everyone for the information, unfortunately, I was looking for first hand knowledge. Love the forum and will post when someone asks a question I can answer. Till then, have a good new year and keep the greasy side down. If anyone can answer my actual question, do pm me.

[oldjohnt]

jc, this has been a fun and informative thread and I hope things have been learned, it sounds like you're on top of all this. To summarize a bit and avoid any confusion as different AC's draw different amounts of current:

 1) A true 30 amp rated branch circuit can supply (Subject to breaker type and design and age etc) somewhere around 24 to maybe 26+ or so amps continuous without tripping its Thermal. SO IT DEPENDS ON WHAT YOUR AC'S AND OTHER LOADS DRAW. If a person has two AC;s that combined dont draw much over 24 + amps and theres no Microwave or other high current units running SURE HE MAY GET BY. So long as the current isn't exceeded an HACR breaker may allow an AC to start which a normal breaker may not in cases where you still dont draw much over 24+ amps total and one AC is running when another starts   IE IT COULD POSSIBLY HELP IN CERTAIN LIMITED SITUATIONS

2) HOWEVER if the wire is undersigned and/or the length of the service and any cords are excessive there may be too much VOLTAGE DROP and you may draw more current and still trip a breaker 

3) There may be other TRICKS people use at an RV park like using the 30 amp outlet PLUS the 15/20 amp (to run two AC';s) provided the 15/20 IS ON A DIFFERERNT LEG then the 30

4) Heck sorry I forget which actual question you mean now lol but I will try my best to answer it. However I think my answers and theory above once understood indeed answers your questions I HOPE IF NOT POST BACK

 

Happy New Year to all

 

John T   

 

[jcussen]

2 hours ago, oldjohnt said:

jc, this has been a fun and informative thread and I hope things have been learned, it sounds like you're on top of all this. To summarize a bit and avoid any confusion as different AC's draw different amounts of current:

 1) A true 30 amp rated branch circuit can supply (Subject to breaker type and design and age etc) somewhere around 24 to maybe 26+ or so amps continuous without tripping its Thermal. SO IT DEPENDS ON WHAT YOUR AC'S AND OTHER LOADS DRAW. If a person has two AC;s that combined dont draw much over 24 + amps and theres no Microwave or other high current units running SURE HE MAY GET BY. So long as the current isn't exceeded an HACR breaker may allow an AC to start which a normal breaker may not in cases where you still dont draw much over 24+ amps total and one AC is running when another starts   IE IT COULD POSSIBLY HELP IN CERTAIN LIMITED SITUATIONS

2) HOWEVER if the wire is undersigned and/or the length of the service and any cords are excessive there may be too much VOLTAGE DROP and you may draw more current and still trip a breaker 

3) There may be other TRICKS people use at an RV park like using the 30 amp outlet PLUS the 15/20 amp (to run two AC';s) provided the 15/20 IS ON A DIFFERERNT LEG then the 30

4) Heck sorry I forget which actual question you mean now lol but I will try my best to answer it. However I think my answers and theory above once understood indeed answers your questions I HOPE IF NOT POST BACK

 

Happy New Year to all

 

John T   

Thanks for the info John. I will post a more definitive question. Does anyone run two standard 13500 or 15000 btu ac's at the same time, in their trailer or motorhome, on a standard campground 30 amp outlet, without the benefit of soft starts, special breakers or wiring, timers or any other equipment that would not normally be installed in a standard mh or trailer. Ac's are both on, set on cool, and cycle on and off on their thermostats. There are no other 110 volt loads. I believe this is a black or white, yes or no, kind of question, not open to interpretation. I don't think it is possible but I am not an electrical expert and more than willing to learn from someone that is. Several people have posted they have, and if your circumstances  are the same as I posted above, would like to hear from you.

 

[GeorgiaHybrid]

JC, I run two Coleman Mach 11,000 BTU AC units on our 32' class C on 30 amps all of the time. Those units pull either 9.3 or 9.5 amps (depending on fan speed hi or lo). I can also use the microwave at the same time as both of those AC units are running. I do have to watch however and turn off one AC unit if we use gas and AC to run the water heater to get the water hot in a hurry. If we can run all of that on a single 30 amp, I wouldn't think that running just two 13,500 units wouldn't be a problem.

While using the items noted above, we will be running the TV and DVD player as well. We do use LED lights and exhaust fans but those are 12V systems.

[Chad Heiser]

3 hours ago, jcussen said:

Thanks for the info John. I will post a more definitive question. Does anyone run two standard 13500 or 15000 btu ac's at the same time, in their trailer or motorhome, on a standard campground 30 amp outlet, without the benefit of soft starts, special breakers or wiring, timers or any other equipment that would not normally be installed in a standard mh or trailer. Ac's are both on, set on cool, and cycle on and off on their thermostats. There are no other 110 volt loads. I believe this is a black or white, yes or no, kind of question, not open to interpretation. I don't think it is possible but I am not an electrical expert and more than willing to learn from someone that is. Several people have posted they have, and if your circumstances  are the same as I posted above, would like to hear from you.

My buddy has a 50 amp Bounder, but he hates pulling out the 50 amp cord - he says it is too heavy and stiff.  So he only ever uses a 30 amp cord with an adapter in his electrical bay.  This means he only ever plugs into 30 amp outlets at campgrounds.  He has two air conditioners on his Bounder and runs both of them regularly on 30 amps.  His bounder does have an energy management system that won't allow the two air conditioners to try to start at the same time.  I don't know what size AC's he has for sure, but if I were a betting man I would say they are at least 13500 BTU units.

[jcussen]

55 minutes ago, GeorgiaHybrid said:

JC, I run two Coleman Mach 11,000 BTU AC units on our 32' class C on 30 amps all of the time. Those units pull either 9.3 or 9.5 amps (depending on fan speed hi or lo). I can also use the microwave at the same time as both of those AC units are running. I do have to watch however and turn off one AC unit if we use gas and AC to run the water heater to get the water hot in a hurry. If we can run all of that on a single 30 amp, I wouldn't think that running just two 13,500 units wouldn't be a problem.

While using the items noted above, we will be running the TV and DVD player as well. We do use LED lights and exhaust fans but those are 12V systems.

 

20 minutes ago, Chad Heiser said:

My buddy has a 50 amp Bounder, but he hates pulling out the 50 amp cord - he says it is too heavy and stiff.  So he only ever uses a 30 amp cord with an adapter in his electrical bay.  This means he only ever plugs into 30 amp outlets at campgrounds.  He has two air conditioners on his Bounder and runs both of them regularly on 30 amps.  His bounder does have an energy management system that won't allow the two air conditioners to try to start at the same time.  I don't know what size AC's he has for sure, but if I were a betting man I would say they are at least 13500 BTU units.

Thanks for the info, my 13500 btu units pull 14.5 amps ea, 10a more than your two. Starting amps will be quite a bit higher for the bigger units and that's the problem. Running is fine, starting is where amperage exceeds 30 amps long enough to trip breaker.

http://www.xantrex.com/power-products/power-accessories/freedom-sequence-ems-power-manager.aspx

The Bounder probably came with something like this one. Believe it looks at total load and only allows second ac to start if load is low enough. Wish my coach had that system.

 

 

[Al F]

4 hours ago, jcussen said:

 

Thanks for the info, my 13500 btu units pull 14.5 amps ea, 10a more than your two. Starting amps will be quite a bit higher for the bigger units and that's the problem. Running is fine, starting is where amperage exceeds 30 amps long enough to trip breaker.

http://www.xantrex.com/power-products/power-accessories/freedom-sequence-ems-power-manager.aspx

The Bounder probably came with something like this one. Believe it looks at total load and only allows second ac to start if load is low enough. Wish my coach had that system.

 

 

If you are saying you actually measured, with a meter you hooked up, and you visually read the current draw and each A/C pulled a steady 14.5A while the compressor is running then you are really pushing a 30amp service.

If on the other hand are taking the rated current draw from documentation, then I encourage you to do some testing with something like a "killowatt" device to see what each A/C pulls.  You may be surprised to find they pull quite a bit less. 

I don't know that there is a simple answer to is it possible to run two 13500 btu a/c's on 30amp service.  oldjohnt gave some very good info to consider.  Knowing the wiring and current pull in your personal setup and testing may be able to show you that you can. 

Other than doing the testing and examining the wiring, it may just be easier to just go ahead and install 50amp service.

Additionally, this is a guest house setup.  If your objective is to use the RV as one would if it was connected to 50amp service, then you need to supply the 50 amp service. 

On the other hand, once cooled down one a/c does a pretty good job of maintaining 78-80 degrees (maybe cooler) in the living area in the daytime. A lot depends on the outside temps and where the sun hits the RV, plus awnings to shade windows and trees for shade.    At night when you don't have the sun one a/c should be able to maintain the sleeping area at 72-74 w/o a problem. 

[jcussen]

14 minutes ago, Al F said:

If you are saying you actually measured, with a meter you hooked up, and you visually read the current draw and each A/C pulled a steady 14.5A while the compressor is running then you are really pushing a 30amp service.

If on the other hand are taking the rated current draw from documentation, then I encourage you to do some testing with something like a "killowatt" device to see what each A/C pulls.  You may be surprised to find they pull quite a bit less. 

I don't know that there is a simple answer to is it possible to run two 13500 btu a/c's on 30amp service.  oldjohnt gave some very good info to consider.  Knowing the wiring and current pull in your personal setup and testing may be able to show you that you can. 

Other than doing the testing and examining the wiring, it may just be easier to just go ahead and install 50amp service.

Additionally, this is a guest house setup.  If your objective is to use the RV as one would if it was connected to 50amp service, then you need to supply the 50 amp service. 

On the other hand, once cooled down one a/c does a pretty good job of maintaining 78-80 degrees (maybe cooler) in the living area in the daytime. A lot depends on the outside temps and where the sun hits the RV, plus awnings to shade windows and trees for shade.    At night when you don't have the sun one a/c should be able to maintain the sleeping area at 72-74 w/o a problem. 

Al, can't really use a plug in kill a watt device because both ac's are hardwired, but I did use an  amprobe current meter on each one individually.  One was 14.3 with high speed fan on, and the other was 14.5. Of course this drops a little bit when fan speed decreases.[if in auto] When I had a smaller 34 ft coach, once cooled down, one ac could keep it fairly comfortable, but my present coach is 40 ft and not gel coat white like the smaller one, so absorbs more heat from the sun. I have double pane windows, awnings on all windows and fairly good coach insulation but in south texas in the summer it is 95 F with 90% humidity, it is too much for one ac. I am comfortable at 80-85 f. but my Canadian relatives develop heat rashes at anything over 72 f..... I have never been able to run two 13500 ac's on 30 amps ,and never in years of rving with bus conversions and and rv's have meet anyone else that could. Do not know why I am beating this dead horse, but I have now given up and am going to run 50 amp service. I do use it as an rv, am taking to Quartzite in a couple weeks. But will only have to worry about the 12 volt loads the aqua-hot uses.

Thank everyone for their input.

 

[Barbaraok]

On 12/26/2017 at 4:42 PM, jcussen said:

Thanks for the input, guess there is no magic bullet here. I use the coach for a guest house here in Texas in the summer and need the two ac's. I was trying to avoid changing my 30 amp wiring and plug, because I am cheap, but guess I will have to rewire to 50 amp.

Why wouldn't you want to put in 50 amp service to your "guest" quarters?  Not only can you keep them cool and comfortable, but let your guests use the microwave for late night popcorn, etc.  

[Al F]

9 hours ago, jcussen said:

............ my present coach is 40 ft and not gel coat white like the smaller one, so absorbs more heat from the sun. I have double pane windows, awnings on all windows and fairly good coach insulation but in south texas in the summer it is 95 F with 90% humidity, it is too much for one ac. I am comfortable at 80-85 f. but my Canadian relatives develop heat rashes at anything over 72 f..... .......

 

Yep it is a little warm in south Texas from end of April to end of Oct.  I have lived in San Antonio for 50 years can attest to that.

Just have the friends come down in the winter.

[Dale P]

On 12/26/2017 at 7:32 AM, jcussen said:

How do you do that? Even with fridge on propane, and charger off, running two ac's normally trips my 30 amp circuit.

Thanks, Jim

So, first, I check my shore power setting on my Magnum MS2812. Make sure it is on 5 or 10 amp. This reduces the heavy charge to my batteries. Next, yes Water Heater and Refrigerator to Propane only. Do not use microwave unless A/C is off. No hair dryers or other heavy AC loads  while the A/C is running. Take a look at your pedestal connections, make sure they are tight and no burn marks, as this generates heat and higher AC current draw.  

[jcussen]

1 hour ago, Dale P said:

So, first, I check my shore power setting on my Magnum MS2812. Make sure it is on 5 or 10 amp. This reduces the heavy charge to my batteries. Next, yes Water Heater and Refrigerator to Propane only. Do not use microwave unless A/C is off. No hair dryers or other heavy AC loads  while the A/C is running. Take a look at your pedestal connections, make sure they are tight and no burn marks, as this generates heat and higher AC current draw.  

So you can run two 13500 standard air conditioners at the same time on a standard 30 amp pedestal? Unless your magnum is a hybrid that uses battery assist when starting bigger loads?

[Al F]

Jcussen,

I think you have mentioned that you have tried running your two a/c's on 30 amp before and have tripped the CB.  If that was at the location you are planning on using in hot weather, have you monitored the voltage at the RV, 30amp or CB plug to see if maybe you are experiencing a voltage loss along the way causing excessive current draw? 

If the testing where the CB tripped was not at your location, give it a try at your location while monitoring amps and voltage and see if it works.  It would be good to have a IR temperature gun to check for overheating connections. 

[jcussen]

12 minutes ago, Al F said:

Jcussen,

I think you have mentioned that you have tried running your two a/c's on 30 amp before and have tripped the CB.  If that was at the location you are planning on using in hot weather, have you monitored the voltage at the RV, 30amp or CB plug to see if maybe you are experiencing a voltage loss along the way causing excessive current draw? 

If the testing where the CB tripped was not at your location, give it a try at your location while monitoring amps and voltage and see if it works.  It would be good to have a IR temperature gun to check for overheating connections. 

Al, you make a good point. If an older campground with only 30 amp service and it is a hot day [when you need 2 ac's] chances are you are not the only one trying to run two ac's. So if everyone is loading up their sites, there is a real good chance that voltage will drop because of the load on the system. 1600 watts is 1600 watts. If you have 120 volts that is 13.3 amps, if you only have 100 volts, that is 16 amps. I believe this is a big part of the problem. I do have an ir gun and use it not just for ensuring good electrical connections, but tire, bearing and brake temperatures.

 

[Kirk W]

1 hour ago, jcussen said:

you make a good point.

On this same line of thinking, most a/c units also draw more current when the ambient temperatures are high, or so I have read. The efficiency drops because of lower heat transfer from the outside core. 

[jcussen]

26 minutes ago, Kirk Wood said:

On this same line of thinking, most a/c units also draw more current when the ambient temperatures are high, or so I have read. The efficiency drops because of lower heat transfer from the outside core. 

Exactly, and especially near the coast, humidity.https://www.doityourself.com/stry/how-humidity-affects-air-conditioning-efficiency