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Old 09-11-2018, 04:10 PM   #1
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Two Power Saver ACs on 30 Amp

I have a 30 foot Freedom Elite 29FE with a Coleman Mach 3 13.5k AC unit. After exhausting all options to keep heat out, I've decided the coach has to have a second AC unit to keep cool in Florida.


The coach doesn't have an energy management system or similar so I'm thinking about buying two of the Coleman Mach 3 13.5k Power Saver units and replacing my current unit while adding the second unit in the rear.


Coleman specs these at 10 amps and 1,000 watts on high cool. At those numbers I could still be around 50% generator load. I do a lot of multi-day generator only parking during football season so the generator being able to run both is a must.


Am I wrong in thinking the Onan 4000 and any 30 amp campground service could handle running both of these without issue? I don't really use my microwave and I'd run the water heater on propane. All lights in the coach are LED, etc..
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Old 09-11-2018, 04:42 PM   #2
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If 10 amps is correct, that would be 1200 watts each. Times two would be obviously 2400 watts, with room to spare. What is the max surge of each unit, then times two assuming they both kick in at the same time? That's the number you must beat. Do you have electric fridge and/or will you be using electric water heater with both A/C's running?
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Old 09-11-2018, 04:54 PM   #3
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Jayco, a Thor brand, and a couple of other manufacturers are using two of the 11,000 BTU/hr Power Savers on a 30-Amp coach with 4,000 Watt generators. They have a power management system, but I think you could do the same manually if you pay attention to loads and donít run too many things at once.

The advantage of the 11,000 Power Saver is that it uses less current at start up. Lock Rotor Amps are significantly lower.



If it were me, and you were going to replace the existing A/C anyway, Iíd add a new 11,000 in bedroom and give it a try. If it didnít work as you want, then Iíd replace the front one with lower current A/C.

I would base load the existing 13.5 by setting thermostat very cold so it wouldnít cycle on and off, and then let the smaller 11,000 PS cycle on and off because it uses less LRA. If that doesnít work, then Iíd replace the front one with another 11,000 PS. This is just an opinion based on what manufacturers are doing with similar-size motorhomes.
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Old 09-11-2018, 06:55 PM   #4
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Originally Posted by The Gritz Carlton View Post
If 10 amps is correct, that would be 1200 watts each. Times two would be obviously 2400 watts, with room to spare. What is the max surge of each unit, then times two assuming they both kick in at the same time? That's the number you must beat. Do you have electric fridge and/or will you be using electric water heater with both A/C's running?

Fridge and water heater would run on propane.


Where can I find the surge of the units? Locked rotor amps says 58.4, but I'm guessing that's not calculated the same since 58.4 x 115V would be over 6,000 watts.
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Old 09-11-2018, 06:57 PM   #5
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Originally Posted by Chance View Post
Jayco, a Thor brand, and a couple of other manufacturers are using two of the 11,000 BTU/hr Power Savers on a 30-Amp coach with 4,000 Watt generators. They have a power management system, but I think you could do the same manually if you pay attention to loads and donít run too many things at once.

The advantage of the 11,000 Power Saver is that it uses less current at start up. Lock Rotor Amps are significantly lower.



If it were me, and you were going to replace the existing A/C anyway, Iíd add a new 11,000 in bedroom and give it a try. If it didnít work as you want, then Iíd replace the front one with lower current A/C.

I would base load the existing 13.5 by setting thermostat very cold so it wouldnít cycle on and off, and then let the smaller 11,000 PS cycle on and off because it uses less LRA. If that doesnít work, then Iíd replace the front one with another 11,000 PS. This is just an opinion based on what manufacturers are doing with similar-size motorhomes.
Interesting idea - thanks for the info.
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Old 09-11-2018, 07:37 PM   #6
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Originally Posted by wdconnors View Post
Fridge and water heater would run on propane.


Where can I find the surge of the units? Locked rotor amps says 58.4, but I'm guessing that's not calculated the same since 58.4 x 115V would be over 6,000 watts.
Locked Rotor Amps is 41.5 for the 11,000 Power Saver. Not certain if this is latest info, so I’d double check.

http://old.rvcomfort.com/rvp/pdf_doc...data_sheet.pdf



And yes, it does take momentarily (a second or two???) that much current to start the air conditioner. You never want to start both at once, which is why I suggested “base loading” the larger one so it doesn’t cycle on a regular basis unless it’s working alone (when smaller one isn’t needed at all).

We did this in industry all the time. A large 400 HP A/C compressor would run base-loaded all the time, and we’d use smaller 100 HP to balance compressors to load. Our compressors could also run at partial capacity, but you get the idea.

Anyway, if you have your present A/C running at about 12 Amps or so, starting the smaller A/C at 41.5 LRA may work OK because Onan 4,000-Watt generators used to start old 15,000 BTU/hr A/Cs which often required over 80 LRA.
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Old 09-11-2018, 07:53 PM   #7
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on our two air conditioner coach, we have two penquin 13.5 units, and can easily run both on a full 30amp circuit, even the 120v fridge, tv, and satellite receiver...

if your generator is capable of 30amp output, then you should be fine just by adding another of the same air conditioners you already have... or you could wire it as a separate feed to be plugged into a separate 15/20amp outside shore power outlet, or to one of your onboard outlets when running the generator.
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Old 09-11-2018, 07:55 PM   #8
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Thanks - everything you said previously made sense, I was just curious as to how a 4,000 starting/~3,5000 running watt generator could handle something with that high of LRA, but I guess it's so fractional it doesn't bother it.
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Old 09-11-2018, 11:51 PM   #9
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Originally Posted by Chance View Post
If it were me, and you were going to replace the existing A/C anyway, Iíd add a new 11,000 in bedroom and give it a try. If it didnít work as you want, then Iíd replace the front one with lower current A/C.

I agree with Chance. GM Tech did something simular (look at the end of "Before you buy a 2nd ac try this first" thread) with his RV and he said it worked fine. I think he used the 15000 + 1100 BTU AC's on 30 amp service Axis/Vegas.

Set the 15000 BTU Thermostat lower than the other that way it aways says on. My 15000 say 19.4 amp (not surge) on the sticker so if your other is at 10 amps even your at 29.4. I thing GM tech also said his Onan 4000 tested at 33 amp for total output (if I recall correctly). So as long as you DONT start at the same time you should be fine (But do your research and desided for yourself).

But you will be very limited on what you can run (a few LED lights should Okay but no blowdryers or Microwave at the same time - Maybe one TV be Okay?).

You could always cool down to like 68 deg inside - shut one AC off to run Micro or some other high draw item for short term, then crank up the other AC.

Let us know know it turns out.
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Old 09-12-2018, 01:02 AM   #10
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Several more things to consider: ambient temperature and altitude. The Onans are rated at 500 ft ASL and 75 F degrees. Both factors reduce the generator's output considerably (3.5% per 1,000 ft altitude and 1% per 10 degrees). There is the distinct possibility that when you try to pull 25 amps out of the generator, you will find the voltage to be around 112 volts and not the anticipated 120 volts (7% more amps required). Another is a problem with A/C short cycling. My Mach 15 will occasionally stall the Onan 4000 when it short cycles on a hot day (105 F ambient).
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Old 09-12-2018, 05:06 PM   #11
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Originally Posted by Long & Winding road View Post
I agree with Chance. GM Tech did something simular (look at the end of "Before you buy a 2nd ac try this first" thread) with his RV and he said it worked fine. I think he used the 15000 + 1100 BTU AC's on 30 amp service Axis/Vegas.

Set the 15000 BTU Thermostat lower than the other that way it aways says on. My 15000 say 19.4 amp (not surge) on the sticker so if your other is at 10 amps even your at 29.4. I thing GM tech also said his Onan 4000 tested at 33 amp for total output (if I recall correctly). So as long as you DONT start at the same time you should be fine (But do your research and desided for yourself).

But you will be very limited on what you can run (a few LED lights should Okay but no blowdryers or Microwave at the same time - Maybe one TV be Okay?).

You could always cool down to like 68 deg inside - shut one AC off to run Micro or some other high draw item for short term, then crank up the other AC.

Let us know know it turns out.
Thanks, sometimes I think I just type a whole pile of stuff and nobody actually reads it! haha.

Ok, a couple more ideas... Buy an ammeter and voltmeter displays for the AC circuit. (Alternating current not air conditioning.) That way you can see EXACTLY what the loads are. Trying to figure this stuff out by numbers and wattage is pointless. There are too many variables that people don't remember to factor in. One of the biggest things that will make running two AC units on 4000 watts or 30 amp shore power overload isn't hair dryers or microwaves, it's your 12 volt battery system.


Hair dryers or microwaves are easy to remember to not use while both AC's are running, but do you know how much AC amperage your battery charger is pulling? If you run your batteries down, fire up your generator and then turn on both AC's, you'd most likely be over the 33 amps and not even realize it. It would end up that the 10+ AC amps that your battery charger is pulling would put it over the top.

Having the voltage display is also extremely valuable. Believe it or not, I get better (higher, more consistent) voltage off of my Onan while running both AC units than I do off my dedicated 50 amp circuit in my driveway. So in my case, the two AC units actually run better off generator power than off shore power. I'd never know that without both volt and amp displays.

So short answer, at least in my opinion, get the rear Power Saver unit first and leave the front one alone. Get the volt and amp displays wired in, even if you have to pay somebody to install them. (It's actually VERY easy, just make sure you buy an AC ammeter with a hall effect pickup and not a shunt.) If you're anywhere below ~33 amps, you're ok. There's always some wiggle room in those ratings. I ran a little Yamaha portable generator at 150% of it's max capacity for about 15 years! Just keep an eye on AC amperage and voltage if you've run your batteries down and then fire up the generator and both AC units.
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Old 09-12-2018, 05:12 PM   #12
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Originally Posted by Beau388 View Post
Several more things to consider: ambient temperature and altitude. The Onans are rated at 500 ft ASL and 75 F degrees. Both factors reduce the generator's output considerably (3.5% per 1,000 ft altitude and 1% per 10 degrees). There is the distinct possibility that when you try to pull 25 amps out of the generator, you will find the voltage to be around 112 volts and not the anticipated 120 volts (7% more amps required). Another is a problem with A/C short cycling. My Mach 15 will occasionally stall the Onan 4000 when it short cycles on a hot day (105 F ambient).
Excellent points! Altitude does make a BIG difference.

On the short cycling, just make sure you're always running full cold and keep the thermostat super cold too when it's really hot. If the coach actually DOES get cool enough inside, just turn the AC and gen completely off for awhile. (awhile meaning more than 30 minutes.) I try to never let it cycle on and off if temps are really hot. It's harder on both the AC and generator to cycle under high temp/load situations.
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Old 09-12-2018, 05:28 PM   #13
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Amazon link to AC volt/amp display...

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


This pic is with both AC's running, 15k in front and 13.5k Mach 8 heat pump in back. Neither are Power Savers. They are both on full cold, high fan speeds. This is on 4000 watt Onan generator power also, notice the nice voltage. The voltage on mine will stay well over 110 even when putting out over 30 amps. But also notice the bottom displays. Those are the DC amperage readings. My 100 amp charger is only putting out 4.5 amps right then. If it was putting out ~100 amps, that AC amperage would be well over 33 amps.
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Old 09-12-2018, 06:49 PM   #14
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As always GMTech, thanks for the info.

FYI I alway read your stuff....LOL. It refreshing to hear from someone that actually works and impoves their RV first hand (instead of 2nd hand info).

Any updates on your never ending quest to impove the old AC on your RV? If so post on that old thread we started about impoving the AC before you purchase a 2nd one. That way we dont hi-jack this thread.
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Old 09-12-2018, 08:24 PM   #15
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Originally Posted by Long & Winding road View Post
As always GMTech, thanks for the info.

FYI I alway read your stuff....LOL. It refreshing to hear from someone that actually works and impoves their RV first hand (instead of 2nd hand info).

Any updates on your never ending quest to impove the old AC on your RV? If so post on that old thread we started about impoving the AC before you purchase a 2nd one. That way we dont hi-jack this thread.
I'm done with the AC mods, it's all working fine. I'm currently working on a totally "outside the box" wheel/tire change on my Vegas. One side is done, still have to do the mods on the other side. I doubt seriously if what I'm doing has been done, and the end result should be awesome. Here's a couple teaser shots, the back isn't anything crazy, it's the front that's the outside the box part. I'll post a new thread when I'm done.
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Old 09-12-2018, 09:02 PM   #16
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LOL when gmtech bought an RV he really did pick up a "starter kit"
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Old 09-12-2018, 09:50 PM   #17
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Looks great. I almost thought you had a Super single on the back until I saw both air lines. More picks when done please.
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Old 09-12-2018, 11:14 PM   #18
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Is the dual air line hooked up to a TPM ? If so then would only need 4 TPMS? If mounted outside on the dual stem? Can that be done? Or did you mount on inside of tire? Thanks!
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Old 09-13-2018, 03:18 AM   #19
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Jamie- Lol, ain't that the truth! I would have rather bought it as a kit.

Long- I actually considered doing super singles, but the risk of not having a spare wasn't worth it to me. The jury is still about 50/50 on whether they're really a good idea anyway. It would look cool though!

Rev- I don't use TPM's on this rig. You could use them though on the rear wheel equalizers though. They'd just read the balance pressure between the two, which should be your desired psi anyway.

Here's the thread about the wheel/tire swap...

"Thinking Outside the Box" Wheel/Tire swap on Vegas
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Old 09-13-2018, 06:35 AM   #20
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Originally Posted by gmtech16450yz View Post
Amazon link to AC volt/amp display...

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


This pic is with both AC's running, 15k in front and 13.5k Mach 8 heat pump in back. Neither are Power Savers. They are both on full cold, high fan speeds. This is on 4000 watt Onan generator power also, notice the nice voltage. The voltage on mine will stay well over 110 even when putting out over 30 amps. But also notice the bottom displays. Those are the DC amperage readings. My 100 amp charger is only putting out 4.5 amps right then. If it was putting out ~100 amps, that AC amperage would be well over 33 amps.
Love the idea of adding the AC meter. If I want to put that at my main monitor panel where do I tap in?
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