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Author Topic: 50 amp versus 30 amp  (Read 1891 times)
Midwilshire
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« on: November 02, 2013, 06:20:15 PM »

We're ready to start pulling wire on our conversion.  I've laid everything out for 30 amp, figuring that it would probably suffice for our loads.  But the Magnum MS4024 inverter we have can run two hot legs no problem, and recently I've begun to think we should wire for 50 amp in case our needs grow in the future.  Never having been in an RV campground, I don't know the popularity and availability of 30 versus 50 amp.  So my question: if you were wiring a bus fresh (not yet converted), would you go with 30 or 50 amp, and why?

Thanks in advance.
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Michael & Gigi
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luvrbus
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« Reply #1 on: November 02, 2013, 06:40:53 PM »

Go with 50 amp if the need ever arises you can run 2 ac's easy with 50amps the 30 amp for 2 ac's is a little iffy sometimes on a real hot day 
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« Reply #2 on: November 02, 2013, 06:41:06 PM »

Quick answer?

50 amp. You can put a 30 amp adapter and run with it any day, and utilize all of it. Not so with 50. Always easier to scale back, IMHO, than to wish you had built better....

FWIW

John
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« Reply #3 on: November 02, 2013, 07:20:56 PM »

50. No question.
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Craig Shepard
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« Reply #4 on: November 02, 2013, 07:25:24 PM »

50 is the new standard.  Hard to upgrade later.  Bob
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Midwilshire
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« Reply #5 on: November 02, 2013, 07:33:26 PM »

Thanks fellas.  50 it is.
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Michael & Gigi
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« Reply #6 on: November 02, 2013, 09:49:43 PM »

Because I use my roof A/C's going down the road, my 10kw genset is wired straight 120vac, along with all wiring. I only use one leg of 50amp, which when plugged in is more then enough power. 30amp can run 2 roof airs, or any 2 electrical items at a time, but 50amp works well. Have never been at a loss for power. I like it so much, I'm wiring my truck the same way. Then you never have to worry about balancing the two legs on either the power pole or the genset. Good Luck, TomC
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« Reply #7 on: November 03, 2013, 08:00:05 AM »

There is no reason that you can't have the generator wired for 120 and connected to both hot leads and the shore power wired for 240.
Balancing the load only matters to your generator, the power company doesn't care about your little 30 amp load.
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« Reply #8 on: November 03, 2013, 08:12:45 AM »

I did as Len suggested and run the 120 volt from my generator to both hot leads.  I have a 50 amp to 30 amp converter that energizes both hot leads too.  I can run two A/C units on a 30 amp circuit, but add in much else like the fridge and the breaker on the 30 amp circuit will trip.  (I only have a 30 amp outlet at home and have had to make the trip to the basement a few times to reset the breaker in the house.)

I like Tom's idea for planning to use only one side of a 50 amp plug although I wonder if that would be enough for three rooftops and other power needs when it is 105 degrees outside?
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #9 on: November 03, 2013, 08:17:57 AM »

I can easily run 3-13,500 roof tops in over 100 degree weather on the one leg of 50amp. I usually only need three to initially cool the bus, then two works just fine. Good Luck, TomC
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« Reply #10 on: November 03, 2013, 08:33:20 AM »

Tom,
I'm not criticizing your installation, there is no doubt it will work.  I just don't see any advantage except the possible savings on a 3-wire shore cord instead of 4 wire.
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« Reply #11 on: November 03, 2013, 08:40:27 AM »

I know I couldn't keep three roof tops running from my 66 amp generator, but I also know a large part of it was that a generator produces less power at altitude and at high temps.  We tripped the breakers on the generator a few times, but a bigger issue was tripping the 20 amp breakers for each air conditioner.

A 50 amp shore connection generally has a lot more surge capacity than a generator.  Of course, shore power can have low voltage if an RV park is not wired properly to handle a hot day with lots of air conditioners running.
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #12 on: November 03, 2013, 09:27:04 AM »

Lmao how in the world can you run 2 even 13,500 btu roof airs off a 30 amp service my Penguin with the 410 freon draws 15.6 amps @ 85 degrees then it goes up almost 1 amp for every 5 degrees over 85 degrees that is from Dometic not me.

My old Penguins would draw 14.3  ea at 85 degrees and go to 17 or 18 amps in the AZ heat so how can you draw 30+ amps from a 30 amp service ?
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« Reply #13 on: November 03, 2013, 09:36:29 AM »

Tom is saying he can run 3 off one leg of a 50 amp service, not 30 amps.  It should work but that one leg is being needlessly stressed when splitting it over two legs would be more efficient, not to mention less voltage drop at the units.
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« Reply #14 on: November 03, 2013, 09:41:36 AM »

He also said he could run 2 off 30 amps in another post Len I want to know how he does it  the only way I see that happening here in the summer is 1 at time
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« Reply #15 on: November 03, 2013, 10:59:50 AM »

He also said he could run 2 off 30 amps in another post Len I want to know how he does it  the only way I see that happening here in the summer is 1 at time

Clifford, do I need to fly you up here next summer to prove to you I can run two 15,000 BTU rooftops off of a 30 amp service?  I've been doing it for 6 or 7 summers now.  It typically never gets over 95 degrees here and it is usually more like low to mid 80s.  If I was in Arizona it might not work, but I'm not in Arizona.  I can't run anything else off the 30 amp circuit at the same time.  I've tripped the breaker more than once by trying to run too much at the same time.

I installed a 30 amp service back when I had my travel trailer and I don't want to upgrade so I make do with it.  The time and money to install a 50 amp service just isn't worth it to me.  I only installed 1/2" conduit so I would have to replace the conduit.  I never imagined I would ever have a 50 amp RV when I installed the electrical.
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
Scott Bennett
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« Reply #16 on: November 04, 2013, 06:56:15 PM »

I also don't know how you guys are running two roof airs off 30 amps. :-/ explain me!?


Sent from my iPhone using Tapatalk. Clumsy fingers may contribute to mistakes.
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Scott & Heather
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« Reply #17 on: November 04, 2013, 10:02:27 PM »

I was just at the Happy Traveler RV Park in Palm Springs, Ca. The RV park had just rewired all the power poles and had not upgraded the circuit breakers yet. They were still at 30amps. So I used one leg of 30amp and did run 2-roof airs in the middle of the day. Just made sure all other items were turned off.

One thing that I found that really helps on a hot day (my breaker boxes are inside the bus) is the computer cooling fan I installed in the power cabinet. It keeps cool air circulating through the box and really helps keeping the breakers from blowing.

When I wired the bus, it was just easier to keep all service at single 120vac instead of trying to split the service. Good Luck TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Midwilshire
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« Reply #18 on: November 05, 2013, 12:14:29 AM »

When I wired the bus, it was just easier to keep all service at single 120vac instead of trying to split the service. Good Luck TomC

Good idea with the computer fans; I think I'll copy that.

Why was it easier to keep your service at single 120vac?  Isn't running 50 amp service just a matter of running one extra wire from your service entrance to the inverter, and one extra wire from the inverter to the main breaker panel, where the two hots power two separate bus bars?  All of the breaker panels I'm finding at the home stores seem to be set up for this by default, which was what made me think of changing our design to 50 amp.  And when you roll up to a 30 amp pole, a $20 dogbone connector energizes both hot legs of the bus off the single hot wire in the pole.  Is there something additional that I'm missing (which is very possible)?
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Michael & Gigi
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« Reply #19 on: November 05, 2013, 04:00:17 AM »

Good idea with the computer fans; I think I'll copy that.

Why was it easier to keep your service at single 120vac?  Isn't running 50 amp service just a matter of running one extra wire from your service entrance to the inverter, and one extra wire from the inverter to the main breaker panel, where the two hots power two separate bus bars?  All of the breaker panels I'm finding at the home stores seem to be set up for this by default, which was what made me think of changing our design to 50 amp.  And when you roll up to a 30 amp pole, a $20 dogbone connector energizes both hot legs of the bus off the single hot wire in the pole.  Is there something additional that I'm missing (which is very possible)?


This is how ours is wired. And the dog bone works just fine when on 30amp.


Sent from my iPhone using Tapatalk. Clumsy fingers may contribute to mistakes.
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Scott & Heather
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« Reply #20 on: November 05, 2013, 05:34:36 AM »

  This is how ours is wired. And the dog bone works just fine when on 30amp.

      And with a $5 adapter, it works OK for times when the only thing around is a 15A 120V socket.  Of course, you have to be careful with how much you draw, but if you don't have to have A/C right then and you just want to keep your house batteries charged for a day or two, it's useful.
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Bruce H; Wallace (near Wilmington) NC
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« Reply #21 on: November 05, 2013, 05:56:05 AM »

When running on the edge of max amp available and you make a mechanical connection (adapter) I was taught to allow for as much as a 10% drop for each.  Old school prob not correct.  Still think go for 50 and settle for 30 if that is all there is.  Airconditioners get old and require a few more amp to start then what?
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« Reply #22 on: November 05, 2013, 06:09:11 AM »

You could probably run 2 -13,500 ac off 30 amps if you started 1 let it run and settle out then start the other but if one kicks out and tries to start you are dead in water  

The Rv manufactures never try and run 2 ac units off a 30 amp service they all have some type switch to run 1 at a time I think all motor homes have a 50 amp service since around 1996 even with only 1 ac   


 LOL Belfert running AC's at 95 degrees what a pansy here that would be a sweat shirt weather
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« Reply #23 on: November 05, 2013, 06:31:17 AM »

Humidity is the reason to run air conditioners here in Minnesota.  I was more comfortable outside in the very dry 105 degree heat in Nevada this summer than I would have been at home at 85 to 90 degrees.  I do nothing special to get two 15,000 BTU A/C units to work on my 30 amp connection at home.  I turn one on and then walk over to the other one and turn it on too.  I suppose the short delay might be enough to get by the initial surge.
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« Reply #24 on: November 05, 2013, 06:38:54 AM »

I was looking for one of Nick's old post about the the draw and starting of roof top AC's and the amp factor as the temp goes up but cannot find it here it maybe on the BNO
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« Reply #25 on: November 05, 2013, 07:54:32 AM »

One thing that I found that really helps on a hot day (my breaker boxes are inside the bus) is the computer cooling fan I installed in the power cabinet. It keeps cool air circulating through the box and really helps keeping the breakers from blowing.
Good Luck TomC
Why would you suggest this....the breaker is designed to trip at a certain temperature....and you are artificially defeating it...I think that is a code no-no...
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« Reply #26 on: November 05, 2013, 07:56:00 AM »

 I was looking for one of Nick's old post about the the draw and starting of roof top AC's and the amp factor as the temp goes up but cannot find it here it maybe on the BNO

    Clifford, dunno exactly how much this tells us but Coleman lists the following for the low-profile (for instance) Mach 8 units --

Unit           13.5KBTU AC   13.5K Heat Pump   15KBTU AC   15KBTU Heat Pump
Watts ARI      1599               1647                    1671            1657
"Desert"*       1913               1946                    1995            2017

     Another manufacturer quotes "ARI" at 80 deg F. (but others seem to reference 90); Coleman quotes Desert as being 120 degrees.   So, just as a guess, I'd say that going from ARI standard to desert results in about a 20% increase in amp draw.
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Bruce H; Wallace (near Wilmington) NC
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« Reply #27 on: November 05, 2013, 08:02:44 AM »

      And with a $5 adapter, it works OK for times when the only thing around is a 15A 120V socket.  Of course, you have to be careful with how much you draw, but if you don't have to have A/C right then and you just want to keep your house batteries charged for a day or two, it's useful.

A decent Inverter Charger requires more than a 15 amp circuit, by a bunch. Running that little $5 adapter through many feet of 10 ga. wire makes the $5 apapter a fire/smoke hazard.....
My inverter/charger is on a 30 amp breaker.
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« Reply #28 on: November 05, 2013, 08:07:48 AM »

   A decent Inverter Charger requires more than a 15 amp circuit, by a bunch. Running that little $5 adapter through many feet of 10 ga. wire makes the $5 apapter a fire/smoke hazard.....   My inverter/charger is on a 30 amp breaker.   

     Yes, I only use mine for "float charging" batteries that are already up and set the max current draw on the inverter to 12Amp (@120V).  I don't use it if the batteries are low and require heavy charge or if I'm using other 120V loads.  It's not for all circumstances but it's a tool that's useful sometimes.
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Bruce H; Wallace (near Wilmington) NC
1976 Daimler (British) Double-Decker Bus; 34' long
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« Reply #29 on: November 05, 2013, 08:42:45 AM »

Thanks Bruce that is what I am saying at 1995 watts 2 units won't run off a 30 amp service and the amps go up or down by the voltage a unit drawing 16 amps @ 120 volts will draw 18@ 110v and the temps the manufactures use are ambient temps that don't cut it on a metal roof on a bus.

I don't know how they run 2 roof tops off a 30 amp service it's a mystery to me anyway it doesn't happen here in the sun  
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« Reply #30 on: November 05, 2013, 08:54:36 AM »

There are better 15 amp to 30 amp converters than the little ones that plug in.  I had one that has a short length of cord, but I lost it somewhere.  Many inverters have a setting for the numbers of amps they are hooked up to.  I set mine down from 30 amps when I plug into a smaller circuit.
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #31 on: November 05, 2013, 10:29:43 AM »

50 amp is my way to go. I have 8 100 ah agm batteries connected to my Magnum 4024 wired for 220 back to a Square D QO 50 amp panel located in my bedroom area. I have the Magnum remote panel and the battery sensor also. All this is wired through a Kraus Naimer 100amp rotary switch set up for OFF/Inverter/Shore/Generator. This way I can feed my ac panel with what ever ac I need at the time. My lighting and other accessories will be or are going to be 12v & 24v dc. I am looking to have all led lighting. The only heavy ac loads should be 2 Penguin 13500 btu with heat pumps and the home style   18 cu refrigerator, stove is propane but has an over stove microwave vented to the roof. Some day I would also like to have some solar pwr too. Coming in for shore power I have the Progressive Industries 50 amp monitoring unit with surge supression with the remote panel which shows your incoming voltage and amps when there is a load. Great little monitor because when on shore power it shows your amp load on each leg of 220.
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Steve Canzellarini
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« Reply #32 on: November 05, 2013, 11:43:41 AM »

 50amp hook up is actually two legs of 50 giving you an available 100 amps combined, I learned early on that 30 amp just ain't enough to stay cool with here in the desert.  Wink Just a side note, when the temps drop below 96 here it gets down right nipply Grin Bring on the summer! Smiley
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« Reply #33 on: November 05, 2013, 02:34:15 PM »

I have my non inverter items separated in another breaker box from the inverter powered items. Hence, If I'm on limited power pole, I can just turn off the 30amp supply to the inverter breaker box and run off a combination of inverter and power pole. I would use this, for instance, if I'm at a friends house with only 20amps coming to the bus and running one roof air. Then if I wanted to say run the microwave, or make coffee, or toast, I can run it off the inverter and worry about recharging the batteries later that night when the A/C is no longer needed. Good Luck, TomC
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