

07012022, 12:32 PM

#1

Junior Member
Join Date: Jul 2022
Posts: 6

Air Conditioner Issue
We have a 2018 Primetime Lacrosse located on a seasonal site which has 30 amp electric service. When we turn our air conditioner on, at least one of our other circuits cuts out. Unfortunately, one of those circuits is the one to the refrigerator. It is a residential style fridge with no propane capability. No circuit breakers are tripping. Is this a common issue when using 30 amp service as opposed to 50 amp?
Thanks.



07022022, 06:43 AM

#2

Senior Member
Join Date: Jan 2016
Location: Idaho
Posts: 11,505

Welcome to the forum its a great place to get your questions answered. How does a circuit cutout without a breaker tripping? Is your rig setup with some sort of load sharing EMS? This will help the forum provide good answers and what to look for. JMHO
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07022022, 07:53 AM

#3

Junior Member
Join Date: Jul 2022
Posts: 6

SeaDog  thanks for the reply and the welcome. My wife and I are new to the RV life and therefore the question. While I’m not an electrician, I’ve done enough residential electrical work to wonder how a circuit cutsout without a breaker tripping. I was hoping someone could tell me if the newer rigs do accommodate load sharing in order to protect electrical components/appliances in low voltage situations.
The circuit to the fridge turns back on almost immediately after turning the AC off. This happens without a manual breaker reset.



07022022, 09:21 AM

#4

Senior Member
Join Date: Aug 2018
Location: Richmond VA
Posts: 3,135

RV air conditioners draw a low of power, especially when starting, and will often not run on a 20amp generator which means your 30a system is going to be extremely taxed with AC, water heater, and crappy (value judgement, sorry ) residential refrigerator.
All these appliances have data plates showing how much power they draw. Usually in watts and/or amps. Grab your notebook and start adding up the numbers. Would not surprise me if you're well over 30 amps.
Set the water heater to propane for starters as it can draw twelve (12) amps when heating the water. So right now you're pulling 20a for the AC and 12a for the water heater. 32a. And we haven't added the refrig and we know that's not all the 120vAC use.
There is another problem. Appliances have power requirements in watts which remain constant regardless of voltage. 1200 watts (a convenient number) at 120 volts needs 10 amps. That same 1200 watts at 110 volts needs 11 amps. At 100 it needs 12  the amp requirements escalate when power gets low. Critical in locations like a camper with few amps available. We have an AutoFormer which increases shorepower voltage 10% starting at 113v. When the power drops to a dangerous 100v the device outputs 110v. Saved us a couple of times at some older campgrounds.
I'm betting your trailer has a 50a system which is actually two (2) 50a power legs in one and provides 100 amps so trying to run everything on 30a is gonna take some sacrifices in what you can run.
 Chuck
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07022022, 10:03 AM

#5

Junior Member
Join Date: Jul 2022
Posts: 6

Chuck  you are correct in assuming that our trailer has a 50 amp system. Your detailed response is exactly what I was looking for.
Thank you.



07022022, 11:53 AM

#6

Senior Member
Join Date: Aug 2018
Location: Richmond VA
Posts: 3,135

Hope it helps. Let us know your results/solution. I looked at my two residential refrigerators  here in my actual residence  and one draws 6 amps and the other 6.5 so my guess is you may have just enough amps once you put the water heater on propane. And the voltage stays at 120vAC. A starting capacitor for the AC always helps.
For lurkers and anyone considering a "residential refrigerator:" Propane refrigerator has saved our bacon (and beer and ice cream!) at several campgrounds which were hit with electrical brown outs from all the motorhomes and 5th Wheels trying to run multiple AC units.
 Chuck
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07022022, 12:38 PM

#7

Senior Member
Join Date: Apr 2021
Posts: 330

Amps and Watts
If the trailer has a 50 amp service, that is 50 amps on one leg and 50 amps on the other leg for a total of 12,000 watts. That is not 100 amps. L1 and L2 currents are different by 180 degrees and the current does not add.
L1 voltage measured to L2 voltage is 240 volts at 50 amps, limited by the circuit breaker on the power post, which is also 12,000 watts.



07022022, 01:58 PM

#8

Senior Member
Join Date: Aug 2018
Location: Richmond VA
Posts: 3,135

OK, I'm confused.
50 amp x 240 volts = 12,000 watts
and
100 amp x 120 volts = 12,000 watts
or
Leg 1: 50 amp x 120 volts = 6,000 watts
+ Leg 2: 50 amp x 120 volts = 6,000 watts

100 amp x 120 volts = 12,000 watts
Question: Do "50 amp" campers have a dual circuit breaker? 50a+50a? Two separate circuits?
 Chuck
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07022022, 02:21 PM

#9

Junior Member
Join Date: Jul 2022
Posts: 6

I’ve included a picture of our electrical panel.



07022022, 02:25 PM

#10

Senior Member
Join Date: Jul 2017
Posts: 3,273

Quote:
Originally Posted by Turc1202
I’ve included a picture of our electrical panel.

You clearly have 50 amp service with 2 50amp legs of 120 power



07022022, 02:36 PM

#11

Senior Member
Join Date: Apr 2021
Posts: 330

Volts Amps and Watts
Ohms Law of electrical circuits as related to Volts, Amps, Watts, and Resistance.
We use E to represent volts or electromotive force.
We use I to represent current flow in amps.
We use R to represent resistance in ohms.
We use W to represent power in watts.
Therefore:
I = E / R or current equals volts divided by the resistance in ohms
E = I x R or volts equals current times resistance in ohms
R = E / I or resistance equals voltage divided by the current
W = I x E or watts equals current times voltage.
E = W / I or volts equals watts divided by amps.
I = W / E or amps equals watts divided by voltage
The power post in the campground will have a double 50 amp breaker for the 50 amp 4 pin outlet, a single 30 amp breaker for the 30 amp 3 pin outlet, and a single 20 amp breaker for the 20 amp outlet.
Thus if your refrigerator nameplate shows the power required is 150 watts, then at 120 volts the current would be 150/120 or 1.25 amps.
If your 13.5k BTU air conditioner draws 13 amps then volts times amps equal 120 x 13 = 1560 watts. If the starting current is 16 amps then the power required is 16 x 120 = 1920 watts.
If the microwave requires 1500 watts, the current is 1500 / 120 = 12.5 amps.
If your electrical service is a 30 amp service, then 120 volts times 30 amps is 3600 watts.
In the above, if the refrigerator is running (150 watts) and the microwave is running (1500 watts where actual power is always greater than cooking power) and the AC starts (1920 watts) this is a total watt demand of 3570 watts or a current demand of 29.75 amps. A bit of a full load for a 30 amp service. Oh, we forgot about the converter running, so we are really out of power availability on a 30 amp service.
One can add the requirement of each piece in watts to get the total watt demand. Or one can add the amp requirement of each piece to get the total amp demand.
Take a little time to understand the above and save yourself some grief when things don't work and circuit breakers trip, or fuses blow.
End of electrical lesson 101.
Bob



07022022, 02:45 PM

#12

Senior Member
Join Date: Aug 2018
Location: Richmond VA
Posts: 3,135

Bob 
I see you've reposted the salient points of post #4.
Still puzzled why 2 x 50 = 50. And now that the electrical panel photo is posted why there are a pair of 50 amp breakers.
The topic, though, is running several appliances off a 30 (thirty) amp circuit which will be difficult regardless of what the trailer wiring was originally intended to do. 30a to 50a converters just split the power to both 50 amp circuits but are still limited to 30 amps of the power source. Shorts or overloads won't hit either of the 50a breakers 'cuz the breaker on the 30a source will trip before either of them can but the individual breakers still protect the circuits.
 Chuck
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07022022, 03:00 PM

#13

Senior Member
Join Date: Apr 2021
Posts: 330

Two breakers
Each breaker is 50 amps. They are tied together via the bar. If one side trips at 50 amps so will the other side. There is no way to get 100 amps through a 50 amp breaker. So one has 50A on one side and 50A on the other side. Thus two 50 amp breakers limit the current on each one to 50 amps.
If one expects 100 amps then the phases, L1 and L2 have to be at zero degrees or in phase in order to parallel the two. But since L1 and L2 are 180 degrees different, the voltage between the two adds but the current does not.



07022022, 08:29 PM

#14

Senior Member
Join Date: Jul 2017
Posts: 3,273

Quote:
Originally Posted by Chuck_S
Bob 
I see you've reposted the salient points of post #4.
Still puzzled why 2 x 50 = 50. And now that the electrical panel photo is posted why there are a pair of 50 amp breakers.
The topic, though, is running several appliances off a 30 (thirty) amp circuit which will be difficult regardless of what the trailer wiring was originally intended to do. 30a to 50a converters just split the power to both 50 amp circuits but are still limited to 30 amps of the power source. Shorts or overloads won't hit either of the 50a breakers 'cuz the breaker on the 30a source will trip before either of them can but the individual breakers still protect the circuits.
 Chuck

The 50 amp breakers 2 of them feed the breakers to the left and right of each 50 amp breaker so each leg or branch of breakers is feed by one each of the 50amp breakers . At the pedestal you are pulling 2 legs of 50 amp the distribution panel splits the 2 50 amp legs to feed the 2 branches of breakers in the panel . I think I just confused myself



07022022, 09:20 PM

#15

Site Team
Join Date: Nov 2010
Location: Northeast Louisiana
Posts: 29,572

Quote:
Originally Posted by Bob K4TAX
Each breaker is 50 amps. They are tied together via the bar. If one side trips at 50 amps so will the other side. There is no way to get 100 amps through a 50 amp breaker. So one has 50A on one side and 50A on the other side. Thus two 50 amp breakers limit the current on each one to 50 amps.
If one expects 100 amps then the phases, L1 and L2 have to be at zero degrees or in phase in order to parallel the two. But since L1 and L2 are 180 degrees different, the voltage between the two adds but the current does not.

I believe you are just being a little too technical here. The members are stating that you can power up 100 amps total worth of 120 volt stuff in an RV that has 120/240 50 amp volt split phase service....not that you can get 100 amps per leg or per circuit breaker.
240(L1,L2) volts X 50 amps =12000 watts
or
(L1)120 volts X50 amps =6000 watts + (L2) 120 volts X 50 amps=6000 watts....or in simple terms that the RV can provide power up to 12000 watts (aka equivalent of 100 amps cumulative total adding the L1 and L2 together) of 120 volt items.
This is one of my favorite articles that helps explain the shared neutral between L1 and L2 in a 120/240 split phase system, thus one reason the 50 amp circuit breaker has their handles tied together. so there is never more than 50 amps on this shared neutral.
Remember that the DIY'ers members here are not electrical engineers and just need the basics, not the college course.
https://www.rvtechmag.com/electrical/chapter3.php
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08042022, 10:35 AM

#16

Junior Member
Join Date: Jul 2022
Posts: 6

**UPDATE**
In one of the replies from Chuck S, he mentioned that he had bought an Autoformer. After doing some research, I decided to purchase one to see if it would help alleviate my electrical issues. I’ve been using it for about 3 weeks now and it has worked beautifully. No more issues with circuits cutting out. Several other seasonal campers at my location at my location have now bought one and have had similar results. We’ll worth the investment.



08042022, 11:01 AM

#17

Senior Member
Join Date: Apr 2021
Posts: 330

L1 and L2
Technical or not.............
Since L1 and L2 are 180 degrees phase difference, the amps DO NOT ADD. It is the voltage that adds.
Therefore one can not get 100 amps of 120volt service out of L1 and L2 as they are each protected by 50 amp breakers.
Yes, one can get 50 amps out of L1 and one can get 50 amps out of L2, but this is not 100 amps.
It seems here the "engineering types" are not acknowledging this fact.
Bob



08042022, 12:07 PM

#18

Pickin', Campin', Mason
Join Date: Aug 2015
Location: South Western PA
Posts: 16,062

Just a quick question for Bob K4TAX...
If leg 1 (L1) is drawing 35 amps of power and leg 2 (L2) is drawing 40 amps of power... how many amps is your R/V service drawing?
As I mentioned in another thread, we've had this discussion long ago here (and more than once) and also on just about every R/V forum I visit. Most have agreed it is 100a of COMBINED capability.
Yes... any draw on EITHER leg over 50a will result in tripping either the tied breaker in the R/Vs power distribution box or the tied breaker at the pedestal.
It doesn't need to be any more technical than that.
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08042022, 12:33 PM

#19

Senior Member
Join Date: Jun 2013
Posts: 1,102

Quote:
Originally Posted by Turc1202
We have a 2018 Primetime Lacrosse located on a seasonal site which has 30 amp electric service. When we turn our air conditioner on, at least one of our other circuits cuts out. Unfortunately, one of those circuits is the one to the refrigerator. It is a residential style fridge with no propane capability. No circuit breakers are tripping. Is this a common issue when using 30 amp service as opposed to 50 amp?
Thanks.

I'd get a RV start, their newest model will let you run 2 AC on 30 amps. A game changer for sure. Not cheap but in your case will cure your ills. Check it on Youtube or Mike Sokol's channel.



08042022, 12:37 PM

#20

Senior Member
Join Date: Apr 2021
Posts: 330

Quote:
Originally Posted by 5picker
Just a quick question for Bob K4TAX...
If leg 1 (L1) is drawing 35 amps of power and leg 2 (L2) is drawing 40 amps of power... how many amps is your R/V service drawing?
As I mentioned in another thread, we've had this discussion long ago here (and more than once) and also on just about every R/V forum I visit. Most have agreed it is 100a of COMBINED capability.
Yes... any draw on EITHER leg over 50a will result in tripping either the tied breaker in the R/Vs power distribution box or the tied breaker at the pedestal.
It doesn't need to be any more technical than that.

OH, such a simple answer. L1 is drawing 35 amps, L2 is drawing 40 amps AND the Neutral has 5 amps flowing. Thus proving one can not ADD AMPS but can add VOLTAGE in a split phase system with a common neutral.
Bob





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