50 amp to a 30 and 20 out how to do? HELP!
I'm adding a second ac to my WW trailer, it has a 30 amp service, I am wiring the 2nd ac with seperate wiring and load center and breaker out of the load center will be a plug for the ac. I was looki...
Forum Discussion
First, be aware that even though the AC units may be high efficiency and draw only 1000 watts when running, that is at 120 volts. AC units draw more current as the voltage goes down and is opposite to resistive devices (heaters, coffee makers, etc.). When AC units start up, they have a momentary inrush current and for a high eff. AC is about 50 amps. If you read the manual for them, you will find that the min. wire is #12 ga. and breaker size is 20 amps. Running two AC units on the same supply would require a 40 amp breaker and if both started simultaneously, the inrush current would be 100 amps. Some find they can do it on 30 amps but they are risking damage to the AC units. If the voltage is much less than 120, a 30 amp breaker will trip. Don't forget there would also be additional load from converter, fridge, etc.
I would wire the new one on a separate 20 amp cord/circuit and plug it separately into the 20 amp receptacle on the pedestal using a 20 amp power inlet like Park Power. All pedestals always have a 20 amp (GFCI) receptacle by code (unless it's a really old CG) whether or not it has 30 or 50 amps or both. This would allow you to always plug into the 30 & 20 amp recepts. on a pedestal or to plug into a 50 amp one using that adapter with a 30 & 20 amp connector on it.
Note that CGs have a max. of 20 percent 50 amp recepts. by code. (NEC). As of the 2005 code edition, only 5 percent of CGs were required to have 50 amp recepts. in pedestals. Finding a 50 amp recept. can be extremely difficult unless you go to a high end RV park, some casinos or some gov't CGs.
If you do decide to always plug into the 20 amp recept., note that the pedestals and CG wiring are never designed to have both the 30 amp and 20 amp recepts on a pedestal running at the same time. Drawing close to 50 amps at 120 volts on a 30 amp only pedestal can cause excessive voltage drop which will eventually damage AC units. Never run the AC units below 105 volts. From a voltage drop perspective, plugging into a 50 amp recept. with an adapter would be better.
Having a permanently mount voltmeter inside is highly recommended to monitor the CG voltage. Even better, get an EMS unit that will automatically shut power off. Progressive Industries has the best one. There isn't one available for 20 amps tho.
Using an adapter introduces one more potential failure point in the shore power connection due to overheating from a bad connection. Never plug in live - shut off pedestal breaker(s) first. Failing to do this will lead to pitted and dirty plug blades and inside a recept. cause overheating and resistance. Always make sure your plug blades are kept clean.
I would wire the new one on a separate 20 amp cord/circuit and plug it separately into the 20 amp receptacle on the pedestal using a 20 amp power inlet like Park Power. All pedestals always have a 20 amp (GFCI) receptacle by code (unless it's a really old CG) whether or not it has 30 or 50 amps or both. This would allow you to always plug into the 30 & 20 amp recepts. on a pedestal or to plug into a 50 amp one using that adapter with a 30 & 20 amp connector on it.
Note that CGs have a max. of 20 percent 50 amp recepts. by code. (NEC). As of the 2005 code edition, only 5 percent of CGs were required to have 50 amp recepts. in pedestals. Finding a 50 amp recept. can be extremely difficult unless you go to a high end RV park, some casinos or some gov't CGs.
If you do decide to always plug into the 20 amp recept., note that the pedestals and CG wiring are never designed to have both the 30 amp and 20 amp recepts on a pedestal running at the same time. Drawing close to 50 amps at 120 volts on a 30 amp only pedestal can cause excessive voltage drop which will eventually damage AC units. Never run the AC units below 105 volts. From a voltage drop perspective, plugging into a 50 amp recept. with an adapter would be better.
Having a permanently mount voltmeter inside is highly recommended to monitor the CG voltage. Even better, get an EMS unit that will automatically shut power off. Progressive Industries has the best one. There isn't one available for 20 amps tho.
Using an adapter introduces one more potential failure point in the shore power connection due to overheating from a bad connection. Never plug in live - shut off pedestal breaker(s) first. Failing to do this will lead to pitted and dirty plug blades and inside a recept. cause overheating and resistance. Always make sure your plug blades are kept clean.
