We are picking up our new 2018 Miramar 35.3 tomorrow! We are very excited as we have been waiting since mid February when we ordered it. We are coming from a 29' travel trailer so this will be my first experience with a motorhome and 50 amp service. We are taking a one night shakedown trip next weekend at a local state park. The camping sites only have 30 amp service and I have purchased a 30 amp to 50 amp adapter. It is hot here in central Florida and we will need to run the AC units. I know that I will only be able to use one AC at a time but I was wondering how people do this with 30 amp service? Do you manually turn on one unit for awhile and then the other? The 2nd unit is in the bedroom so I was thinking that I could run the front AC unit with the bedroom door closed during the day and then run the bedroom unit at night and turn off the front unit. I have seen some people say their motorhome is smart enough to cycle between the units automatically. As this is our first motorhome, I have know idea yet how our unit will function. I will definitely be asking the tech during the PDI tomorrow but any information and advice would be greatly appreciated.
Thanks,
Burch
2018 Miramar 35.3 Motorhome
3 fur kids (Monty, ZuZu and Pinto)
Rainbow bridge (Murphy, Petie, Lola)
Tom Wilds
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Using the 30AMP zone for both air conditioners is really going to power down your service. It may even get down to just having your converter/charger ON and both air conditioners. The real necessity for me would be to have lights and HDTV and a couple of fans - Maybe the fridge but that can be solved with a 5-day ice chest hehe... Run everything off of PROPANE that you can (Including the Hot water heater)... It still will want to see some 12VDC power for control boards that will be provided by the converter/charger and/or the battery don't let the battery get below 12.0VDC etc... Your battery should be charging when on shore power as long as the converter/charger in ON...
You also should consider that each of your two air conditioners are wired to your separate 50A 120VAC zones. You will have to make sure your RV30A to 50A long DOGBONE adapter will power up both of your 50AMP zones in your trailer.
Sort of like this diagram shows...
![[image]](http://www.dmbruss.com/images/FullTimingLifeStyle/Adapters/3050ampRVDistribution.jpg)
Note the RV30A to 50A long adapter has the two HOT zones wired together in the adapter like shown here... Some of these adapters may only be wired to one of your 50A zones... Something to check on...
![[image]](http://www.dmbruss.com/images/FullTimingLifeStyle/Adapters/30-50ampDogbone.jpg)
DMBRUSS.com images
When plugged into the 30A Service at the campground pedestal will power up both of your 50A Zones but will only have to divide both zones with 30A of power. You will want to flip a few breakers OFF in the 120VAC power Distribution Center to make sure you will not power up too many high wattage items otherwise it will trip the Campground 30A Pedestal breaker. This would really help if one of your 120VAC Air conditoners has it own 120VAC Power cord available to plug into a standard 20A Receptacle. Then you could use the Camp ground 20AMP Service with an proper size extension cord and allow more items to be powered up on both of your 50A zones being powered by only a single 30AM 120VAC shore power connection.
If you 50A trailer has the washer/Dryer setup please note this may be a true 240VAC operation just for the washer/Dryer combo and will not work at all from using the RV30A to 50A long DOGBONE type adapter. Not living in this high-end world I have no idea what would happen if you tried to run those two units from a single 120VAC zone shore power source...
I have also heard some stories about GFCI breakers tripping when using the RV30A to 50A long DOGBONE Adapter... This may have something to do with any surge protectors your 50A Trailer setup is using...
Maybe others on here that has actually done these things will dime in with more info..
Just things to know about and check on...
Roy ken
* This post was edited 06/08/17 11:03am by RoyB *
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You are obviously going to loading down this 30A service big time and since these get a lot of use by all of the 30A trailers the 30A connector may have been over heated and maybe even arced over a couple of time...
Look for burn marks around the connections and if you see them request another site - do not try to use the 30A connections that have obvious burn marks on them...
![[image]](http://i89.photobucket.com/albums/k212/dkr9925/DSCF0860.jpg)
Google image
Using this burned socket will make your 30A side of your RV30A to 50A long DOGBONE adapter cord look like this in short order and will need to be replaced...
![[image]](http://i1194.photobucket.com/albums/aa371/gaspeddler/5e50fca7.jpg)
Google Image
The campgrounds are suppose to keep their equipment in good working order but with all of the high use you can imagine how hard this must be for the campground owners...
Keep a close eye on heat build-up in your cords.
Roy ken
* This post was edited 06/08/17 03:08pm by RoyB *
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Cummins12V98 wrote:
Last DRV with two AC's I had no issue running both AC's on 30A. Turned frig and WH to gas.
Last DRV with two AC's I had no issue running both AC's on 30A. Turned frig and WH to gas.
I can turn the WH to gas but my motorhome has a residential fridge so no gas option.
Clearly there is an inverter. Does it happen to be an inverter/charger? By any chance is it one of the hybrid units?
Regards, Don
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Still I would give it a go.
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pianotuna wrote:
MetalGator,
Clearly there is an inverter. Does it happen to be an inverter/charger? By any chance is it one of the hybrid units?
MetalGator,
Clearly there is an inverter. Does it happen to be an inverter/charger? By any chance is it one of the hybrid units?
The RV has an 1800 watt inverter.
It is too late to install it for your upcoming btrip but for future trips your problem will be resolved.
Run both A/C's on a 30 amp site without issue
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If trying to run 2 ACs on 30 amps, you better know how the voltage is doing. Actually, even with just one is important. Low voltage causes an AC unit to draw more current and can cause even greater voltage drop and possibly prevent one or both AC from starting. Most importantly, if you use an AC unit(s) often enough under low voltage conditions (105V and below), you can cause cumulative irreversible damage to the AC resulting in premature failure. You *might* get one or both AC units to run and all seems okay, but you won't know how much damage has occurred and how much sooner it will fail.
An AC unit draws about 13-15 running amps and the momentary inrush current at startup will be about 50-60 amps (per manufacturer's specs) at 120 volts which is the industry/code nominal system and equipment/appliance voltage. It's important to know that these figures will increase as voltage goes down. *IF* you got the 1st AC to start and voltage was 120, the total current at startup of the 2nd AC will be 15+60 = 75 amps, plus any other loads that are running when trying to start the 2nd AC. That's a lot, even at full nominal voltage. As mentioned above, depending on a number of various factors, the 2nd unit might not start. If the voltage is already low after the 1st unit is running, it's very likely the 2nd unit will not start. Installing a "hard start" capacitor can help in some cases.
At a min. I'd use either a plug-in LED voltmeter or permanently mounted one on a wall to monitor voltage. The best thing of all is to use a Progressive Industries EMS unit that will shut power off at 104 volts. The "other" brand shuts down at 102V which is too low IMO. Note that voltage may look okay before you turn high load items on but can drop quite a bit with more loads running.
Older RV parks have pedestals wired in a star arrangement to a remote panel. Newer parks have pedestals wired in a loop-fed arrangement from one to the next. The newer parks are less likely on avg. to have voltage drop issues because of the heavy wire to the pedestals (typically around 200 amps). Older pedestals usually have 30 amp wire to them and can be a long run. As well, the older editions of the NEC required demand allowances were much smaller. I can almost guarantee that you won't be able to start a 2nd AC on 30 amps in an older RV park, esp. with high occupancy.
Running a 2nd AC off the 20 amp recept. in a pedestal may or may not work because the NEC does not require wire size to pedestals to be based on 20 amp + 30 amps running together and this could cause the voltage drop to be too high. A newer CG would have more of a chance of this working.
We Cant Wait wrote:
Also pulling a full 30 AMPS for an extended period of time could in all likely hood over hear and melt the pedestal plug or your cord plug as shown above.
A receptacle and a circuit breaker are designed to operate at their rating indefinitely. If a pedestal recept. or shore power cord plug gets warm/hot, the cause will be dirty contacts inside the receptacle, a dirty plug and/or weak contact pressure inside the recept. Always make sure your plug blades are kept clean (use emery cloth or sandpaper). As noted above, if a pedestal recept. looks in rough shape, try and find another site or run on minimal loads. Avoid plugging into a pedestal with the power on as this causes pitting and dirt buildup on plug blades.
Also pulling a full 30 AMPS for an extended period of time could in all likely hood over hear and melt the pedestal plug or your cord plug as shown above.
myredracer wrote:
NEC says for continuous load circuits the supply should be 125 percent of the load. Or rather 24 amps is the maximum continuous load that should be on a 30 amp circuit. IIRC continuous is defined as 3+ hours. Air conditioner is not generally considered a continuous load as it should cycle. In reality we all know they can run 12+ hours without cycling the compressor.We Cant Wait wrote:
Also pulling a full 30 AMPS for an extended period of time could in all likely hood over hear and melt the pedestal plug or your cord plug as shown above.
A receptacle and a circuit breaker are designed to operate at their rating indefinitely.Also pulling a full 30 AMPS for an extended period of time could in all likely hood over hear and melt the pedestal plug or your cord plug as shown above.
Just some perspective.
time2roll wrote:
Just some perspective.
myredracer wrote:
NEC says for continuous load circuits the supply should be 125 percent of the load. Or rather 24 amps is the maximum continuous load that should be on a 30 amp circuit. IIRC continuous is defined as 3+ hours. Air conditioner is not generally considered a continuous load as it should cycle. In reality we all know they can run 12+ hours without cycling the compressor.We Cant Wait wrote:
Also pulling a full 30 AMPS for an extended period of time could in all likely hood over hear and melt the pedestal plug or your cord plug as shown above.
A receptacle and a circuit breaker are designed to operate at their rating indefinitely.Also pulling a full 30 AMPS for an extended period of time could in all likely hood over hear and melt the pedestal plug or your cord plug as shown above.
Just some perspective.
To clarify that, the NEC circuit loading only applies to buildings and facilities that have permanent/fixed wiring systems and components and the 80/125 percent rule doesn't apply to RVs. The NEC doesn't cover "portable" plug-in loads and restrict the load relative to the recept. rating it's plugged into. NEC article 551 requires a demand load of 3600 watts (30 amps) for an individual 30 amp RV/site and there is no provision for continuous/non-continuous loads. Art. 551 specifies how wiring within an RV is to be done but does not restrict the total demand on the 30 amp (or 50 amp) shore power connection. I'd post some links to the NEC but can't find a free online version lately.
If you stop and think about it, there is no way that demand in a 30 amp RV can possibly be restricted to max. 80 percent (24 amps). If you added up the available load per branch circuit in the panel, it would far exceed 30 amps. The way you find out if you are drawing too much is simply that you end up with a tripped breaker - you unplug one or more items and reset the breaker and hopefully won't do it again.
![[emoticon]](http://www.rv.net/sharedcontent/cfb/images/smile.gif "smile")
An RV is kinda like an extension cord with a few receptacles on the end of it and it's not possible to restrict how much you plug into it.
* This post was edited 06/09/17 01:10pm by myredracer *
* This post was edited 06/09/17 01:11pm by myredracer *
This is a bit of a red herring. Most Breaker Panels in homes would not power all the circuits at once at 80 percent of their respective loads. Where I am at this moment has a 200 amp panel. There are 2 feeds of 30 amps each to out buildings, a 50 amp circuit for a water heater, a 50 amp RV plug, and a 30 amp RV plug. That already adds up to more than the 200 amp panel could power at full continuous loads.
Just because NEC doesn't say it is illegal is no reason to not respect the 80 percent of load that is recommended for continuous loads. I choose to limit my 30 amp input to 24 amps, unless I'm plugged into a 50 amp shore power supply.
NEC doesn't require code to be followed for ANY item that plugs in. Hence a hardwired autoformer breaks the code, but a plug in autoformer does not.
A far greater issue is voltage drop. I do monitor voltage and use an autoformer. At the location I am now (rural Saskatchewan) it is a long run from the power companies transformer, so even though I have access to 50 amp outlet, I still am using my Sola Basic autoformer, and I have load support active from the Magnum 3012 hybrid inverter/charger.
myredracer wrote:
If you stop and think about it, there is no way that demand in a 30 amp RV can possibly be restricted to max. 80 percent (24 amps). If you added up the available load per branch circuit in the panel, it would far exceed 30 amps.
If you stop and think about it, there is no way that demand in a 30 amp RV can possibly be restricted to max. 80 percent (24 amps). If you added up the available load per branch circuit in the panel, it would far exceed 30 amps.
Running one or the other, but not both on cool, is a plan. Running only one on cool & the other on fan only is a plan. For extra security turn the waterheater off & only use it on propane if using the A/C combos. Also reduce the A/Cs to fan only while using the microwave.
50amp units need 50amp service so that all that stuff can run at once. 30amp service simply cannot provide for full load demand.
The DW is going to turn the microwave on without thinking anyway. /this could result in a trip out to the post to reset the breaker. Head her off by turning the microwave off at the circuit breaker.
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Veebyes wrote:
The DW is going to turn the microwave on without thinking anyway. /this could result in a trip out to the post to reset the breaker. Head her off by turning the microwave off at the circuit breaker.
The DW is going to turn the microwave on without thinking anyway. /this could result in a trip out to the post to reset the breaker. Head her off by turning the microwave off at the circuit breaker.