Dual AC

Fishsizzle · 09-25-2018, 04:26 PM

Just got to Yuma to visit friends and it’s hot!

Anyway, they have a 30 amp service for us to hook up to, we dog boned down from our 50 cord.

I’m shocked that both AC run off this 30 amp at the same time. No issues. Is this normal?

Kansas Gary · 09-25-2018, 04:30 PM

As long as both AC's don't try and kick on at or about the same time then yes 30amp will run both. Make sure your hot water tank is on propane and don't try to make any thing in the microwave you good to go..............

**sourdough** · 09-25-2018, 05:39 PM

You need to watch your incoming voltage. The ACs may run but they may be at a voltage level that will damage, or ruin, your compressors. Hopefully you have an EMS that will tell you what's going on.

**chuckster57** · 09-25-2018, 06:11 PM

Quote:

Originally Posted by sourdough

You need to watch your incoming voltage. The ACs may run but they may be at a voltage level that will damage, or ruin, your compressors. Hopefully you have an EMS that will tell you what's going on.

Bingo! I wouldn’t be doing what you are.

notanlines · 09-26-2018, 04:24 AM

I can only reiterate what has been already posted. This is NOT a good idea. Keep this up, Fish, and in a few days you'll be posting about how the Dometic AC's are just crap and why does Keystone use this garbage in their new rigs.

Fishsizzle · 09-26-2018, 05:54 AM

Ok good to know, I’ll check on them a see what’s up. Thanks very much!

Fishsizzle · 09-26-2018, 08:14 AM

Question, with our pups in the RV while we go out to eat, it looks like the low voltage EMS shuts down power. Will it kick back on?

What about the Hughes autoformer? Anyone use it? Seems this might be a better, all be more expensive way to go.

**sourdough** · 09-26-2018, 07:50 PM

Quote:

Originally Posted by Fishsizzle

Question, with our pups in the RV while we go out to eat, it looks like the low voltage EMS shuts down power. Will it kick back on?

What about the Hughes autoformer? Anyone use it? Seems this might be a better, all be more expensive way to go.

I leave my pup in the trailer all the time when we leave for a bit. My EMS doesn't just shut down power "because". I've never had it cut power when we've been gone - and we have left for 3-4 hours. On the other hand, puppy is not going to die, or get uncomfortable, for the length of time we leave her....and we love her as much as we love our kids. If your EMS is cutting off your power that often and for that long whoever is supplying your power needs to correct it.

Fishsizzle · 09-26-2018, 05:53 PM

Did I mention a product I shouldn’t have?

**chuckster57** · 09-26-2018, 05:59 PM

Quote:

Originally Posted by Fishsizzle

Did I mention a product I shouldn’t have?

No, not many here that are familiar with that product. Bottom line is if your only getting 30A from the pole, I don’t believe the autoformer will bump it up to 100A ( two legs of 50A). You will still only have 30A to work with. I could be totally wrong, and if someone can tell me I am with proper reference material, I’ll gladly admit what I just did...I don’t know.

**JRTJH** · 09-26-2018, 07:12 PM

The way I understand electricity is that as voltage falls, amperage increases to maintain the required watts for equipment operation. In other words, all appliances and other users of electricity actually operate on total watts, not volts or amps (both of which are inter-related to attain the required wattage)..

In other words, as an example, if you have an air conditioner that draws 15 amps at 120 VAC, it operates on 1800 watts. If the voltage drops to 100 VAC, the amperage would increase to 18 amps so the air conditioner could draw the required 1800 watts.

As the amperage required goes up, so does the heat generated within the electric motor/compressor. It's the heat that causes damage to the air conditioner (in this example)...

Now, if you're "not close to the maximum 30 amp draw, a Hughes Auto-Former could help you increase the voltage by using a transformer to step up voltage, thereby keeping the amperage down to "normal consumption"....

If, on the other hand, you are close to the 30 amp limit of the power system input (shore power) then the Auto-Former can't "make power", so there's a limit to the maximum wattage that the transformer in the Auto-Former can "transform"..... In other words, once the 30 amp Hughes Auto-Former reaches its maximum of 3600 watts input, it can't make more power out than it has power in. To put it another way, a 30 amp Auto-Former can't produce 35 amps, stated another way, the 30 amp unit is rated at a maximum of 3600 watts (regardless of volts/amps) and can't produce an output of say, 4200 watts.....

If you have a 50 amp Hughes Auto-Former, it then transfers the wattage limitation to the circuit breaker on the shore power 30 amp circuit breaker (3600 watts) and can't transform or provide more than 3600 watts. It will, with either a 30 amp or a 50 amp Auto-Former, maintain the 120 volt output up to the maximum wattage of 3600 watts (which is the maximum circuit availability) then the shore power circuit breaker would open and disable the circuit when the trailer draw reaches 30 amps through the shore power plug.... It simply can't "make power" where there is no availability.

ADDED: I would suspect, based on you saying that your EMS has "cut off power" a couple of times that what is really happening is you're close to the maximum 3600 watts through the 30 amp power plug, a voltage drop is occurring which causes an amperage increase (to maintain the wattage requirement to operate the two air conditioners). That causes the EMS to sense the voltage drop/amperage increase and the EMS is shutting off power because it's no longer in the "acceptable/anticipated range" That's the function of the EMS and I'd say it's doing what it is supposed to do. Essentially, you're operating two A/C's on minimal power and as the circuit overloads, the EMS is shutting down before the shore power circuit breaker opens.

**sourdough** · 09-26-2018, 07:46 PM

They "try" to up the power output if it drops below the established levels. They cannot, and do not, "generate" additional current/voltage above/beyond the limits of the input power from anything I've ever read or researched.

Fishsizzle · 09-26-2018, 08:44 PM

Thanks for letting me know how the Hughes works. I’ve been working on understanding AC for the last few years. I took me a solid sit down and think to figure out Ohms.

I haven’t bought the EMS yet. I’ve just heard they can stop if voltage drops and was concerned about AC kicking off and not kicking back on. I’ve just been running 1 AC and spending more time in our friends home.

Yuma is a conundrum. I’m told they have 100k permanent residents, and another 100k that winter, but they do not have big RV parts store. Foothills is small and they have good repairs it seems. I would think they would have a camping world or something big. No one in town has an EMS. Was looking for a progressive, Foot hills had the surge, but not the low voltage. I’ll wait till I’m home to get one and wire it in.

Thanks for all the input and explanations.

Justin aka Fishsizzle

**sourdough** · 09-27-2018, 05:48 AM

Justin, I failed to answer one of your key questions; "does it turn back on?" Yes, when the failed condition is corrected the unit restores power.

Depending on the length of time you are going to be away you could possibly order the EMS online?? I'm sure Amazon and other outlets sell them.

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