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Old 07-18-2018, 06:21 PM   #21
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How many amps does your AC use?

The more correct question to ask may be how many watts does your AC use. To find this info, start by looking up the energy specs for your air conditioner. For this example, we'll use 10 amps at 120 volts.
120
x10
= 1200 watts

Why look at it this way? Because your appliance is try gonna find a way to get 1200 watts of energy to run if the voltage is 120, 110, or 100. To find the amperage if you know the wattage, divide the watts by the volts: 1200 / 110 = 10.9, and at 100 volts the amperage is 12.

Why is this important? To keep your appliances running well and for as long as possible. "An induction motor will draw more current to compensate for the decreased voltage, which may lead to overheating and burnout. If a substantial part of a grid's load is electric motors, reducing voltage may not actually reduce load and can result in damage to customers' equipment." (https://en.wikipedia.org/wiki/Brownout_(electricity)

So, know the wattage and the voltage, and you'll know the amperage.

Yeah, this may be a trip down a road no one expected, but I've run into low voltage at the pedestal before, and I want my AC and other appliances to run as long as I can get them to.
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Old 07-18-2018, 10:20 PM   #22
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Originally Posted by 1bigmess View Post
How many amps does your AC use?

The more correct question to ask may be how many watts does your AC use. To find this info, start by looking up the energy specs for your air conditioner. For this example, we'll use 10 amps at 120 volts.
120
x10
= 1200 watts

Why look at it this way? Because your appliance is try gonna find a way to get 1200 watts of energy to run if the voltage is 120, 110, or 100. To find the amperage if you know the wattage, divide the watts by the volts: 1200 / 110 = 10.9, and at 100 volts the amperage is 12.

Why is this important? To keep your appliances running well and for as long as possible. "An induction motor will draw more current to compensate for the decreased voltage, which may lead to overheating and burnout. If a substantial part of a grid's load is electric motors, reducing voltage may not actually reduce load and can result in damage to customers' equipment." (https://en.wikipedia.org/wiki/Brownout_(electricity)

So, know the wattage and the voltage, and you'll know the amperage.

Yeah, this may be a trip down a road no one expected, but I've run into low voltage at the pedestal before, and I want my AC and other appliances to run as long as I can get them to.
Very good point.

Also a good reason to consider a Progressive Industries (or similar, there are other mfrs) "electrical management system" (EMS).

They are much more than surge suppressors. They look for low voltage; high voltage; incorrect frequency; hot & neutral wires reversed; no ground, etc. Any of those conditions will cause the unit to disconnect from shore power (or remain disconnected).

They aren't cheap. Our 30A hardwired unit w/remote (#HW30C) cost about $270.
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Old 07-18-2018, 10:42 PM   #23
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Legolas
Not sure what you meant when you said " having my coach wired up like that". If you were thinking about adding a transfer switch to eliminate plugging the power cord to the outlet connected to the generator, I would recommend against it. A transfer switch requires extensive heavy wiring and will only save you plugging in the cord. Transfer switches of late have been responsible for several " near" fires resulting from connections coming loose and generating significant heat that can lead to a fire. Simplicity beats the complexity of additional gadgetry in my opinion. Good luck
I agree.

The transfer switch really doesn't save the owner much effort anyway.

We leave our shore power cord plugged into the genset outlet all the time (except when shore power is available). We have an MS2000 inverter that is wired to power the whole coach, but if we want to fire up the generator we're ready to go, as the cord is always plugged in.

At a campsite with shore power, the owner must obviously plug the cord into the pedestal whether their rig has an ATS or not.

To be honest, since our View does not have an ATS (the MS2000 does though) I haven't given much thought to what advantage an ATS offers. I could be missing something, but it seems like there is really no advantage. In a rig with an ATS, there is no generator outlet, so the cord is not plugged into an outlet, but it still must be stowed. Without the ATS, we stow the cord in the same way and just plug it in rather than laying it in the compartment.

As bobmac mentioned, an ATS can cause problems. Any electro-mechanical device can fail. In fact, before I retired, part of my job involved testing AT switches for proper operation. These were serious, industrial switches that were installed in a controlled environment (not mounted in an RV) and they failed periodically. Sometimes they would get stuck halfway through the transfer motion, which meant both normal and emergency power were shut off. That's when the phone would start to ring...

I read a lot of threads and posts and I'm not aware of a rash of ATS failures in RVs. If we had one I'd likely leave it installed and just make sure it was working properly (which involves 'don't try this at home' testing). However, I would not recommend that anyone without an ATS have one installed.
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Old 07-18-2018, 11:05 PM   #24
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My last coach had a digital readout and I went through the entire coach, turning on/off all appliances to determine current draws. I remember my 15,000 BTU unit drawing about 16 amps at startup and about 14 when running. You want to use the 20 amp plug in the garage and as short a cord as possible. A 12 ga. cord will work at about 50 ft-go to a 10 ga. cord if longer. Always turn off other draws, including the battery charger, since it will divert some of the current you need for the A/C. I ended up pulling the cover off the garage panel and installing a 30 amp breaker, cut off the 10 ga. ext. cord plug and hard wired it to the breaker. It could easily go 100 ft. out to the coach and run the A/C with some other loads to boot!
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Old 07-19-2018, 12:38 AM   #25
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My last coach had a digital readout and I went through the entire coach, turning on/off all appliances to determine current draws. I remember my 15,000 BTU unit drawing about 16 amps at startup and about 14 when running. You want to use the 20 amp plug in the garage and as short a cord as possible. A 12 ga. cord will work at about 50 ft-go to a 10 ga. cord if longer. Always turn off other draws, including the battery charger, since it will divert some of the current you need for the A/C. I ended up pulling the cover off the garage panel and installing a 30 amp breaker, cut off the 10 ga. ext. cord plug and hard wired it to the breaker. It could easily go 100 ft. out to the coach and run the A/C with some other loads to boot!
We also have a 100' #10 AWG extension cord. We have run our 13,500 Kbtu A/C unit using a 15A circuit.

Our Progressive Industries HW30C shows that the A/C pulls about 12-13 amps when running. Voltage drop was minimal.

The starting surge is much higher than the running amps but it's hard to measure because the HW30C only updates every few seconds. In any case, that does not seem to be a problem.

As you said, a 20A circuit would be much better. The continuous rating of most fuses and breakers is about 80% of nominal. So 15A is 12A continuous; 20A = 16A indefinitely.

Using a #10 gauge cord is good because it is the same gauge as the shore power cord, and rated to carry 30A. However, with max of say 15-16A flowing through it, voltage drop is limited. If the calculator I used is correct, 15A @ 120V will result in <3% voltage drop, which is very good.
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Old 07-19-2018, 04:56 AM   #26
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When my A/C was working properly, it ran on a 15 Amp GFCI circuit with no problem. When the compressor started to go bad, the start up amperage would run as high as 60 Amps! Start up amperage should be less than20 Amps and running Amps should be 3-5 on fan only, and 13-15 with A/C. My new A/C should be delivered this week so I can hit the road! Good Luck!
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Old 07-19-2018, 10:02 AM   #27
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Three Air Conditioners

I have three roof air conditioners on my Ellipse. Can only two run at the same time if you are plugged into a 50 amp circuit? If yes I assume you control which two run through the thermostat using temperature settings or system settings - is that correct?
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Old 07-19-2018, 10:55 AM   #28
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It will cost pennies more to have a 50 amp circuit installed and any future "upgrades" will be covered. Make darn sure the electrician understands RV connections. It is not a 30 amp 240 V system like the house dryer uses.
Partially correct, it is a 30 amp 240 volt system but uses a receptacle that is different from the dryer style. Best to pick up a 30 amp receptacle at your RV dealer or local hardware if they have them and supply that to the electrician.
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Old 07-19-2018, 02:37 PM   #29
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My 2005 Sightseer 29R was wired that way. I added a 4 position rotary switch and wired Shore, Generator and Inverter power to it. This way I can control either power source from inside the coach. It doesn't make much sense to have a generator stat switch inside, but have to go out in the weather to plug into the generator to use it!
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Old 07-19-2018, 04:10 PM   #30
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There are two amp levels, one is the starting level (or spike) and the second is what it takes to run in a steady state once started. Since your A/C is going to cycle on and off, the starting spike will as well.

I don't have any first hand experience but there are "soft start" devices which will reduce the level of the starting spike:

https://networkrv.com/review-easysta...nd-generators/

Personally, I haven't had any issues with my basement air running on my 20A circuit here at home, but I'm using a heavy duty 30A marine extension cord between my rig's cord and my 20A outlet. If you need an extension cord, a typical garage-style cord isn't going to be up to the task.
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Old 07-19-2018, 04:23 PM   #31
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Hard Start Capacitor

The hard Start Capacitor stored electricity helps to start the A/C compressor and fan motor. When it fails, either the A/C won't work at all, or the amperage required to start it would trip breakers!
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Old 07-19-2018, 07:26 PM   #32
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[QUOTE=dnrainey;3821197]
Quote:
Originally Posted by Wayne M View Post
It will cost pennies more to have a 50 amp circuit installed and any future "upgrades" will be covered. Make darn sure the electrician understands RV connections. It is not a 30 amp 240 V system like the house dryer uses.

Partially correct, it is a 30 amp 240 volt system but uses a receptacle that is different from the dryer style. Best to pick up a 30 amp receptacle at your RV dealer or local hardware if they have them and supply that to the electrician.
Just to clarify --

RVs use either a 30 amp 120 volt receptacle or a 50 amp 120 volt receptacle.

There is some understandable confusion because:

a) The plugs and outlets are very large and look like electric range or dryer plugs (which *are* 240V).

b) The 50A receptacles/outlets use both phases (or "legs") of the service. IOW, there are two separate 'hot' wires, a neutral, and a ground. Ordinarily when you see that it is feeding a 240V outlet.

With a 50A/120V RV outlet, the wiring is essentially the same as it is for a dryer or range, but instead of the RV using both phases/hot wires to get 240V, the rigs are wired so that they have two (2) 120V feeds:

* Phase #1 & neutral
* Phase #2 & neutral

I've read too many sad tales of people who had outlets installed -- often by licensed electricians -- only to find out the hard way that the outlet was wired for 240V service, not 120V.

See below:




It's easy to see how even a licensed electrician might mistakenly connect the 2 hots/phases to the 30A/120V RV outlet.

The image at this link shows a 50A/240V receptacle. For some reason the image itself would not transfer. It's also from "The No-Shock Zone":

http://www.replicasuper.com/wp-conte...ng-diagram.jpg
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Old 07-19-2018, 07:46 PM   #33
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Lowes has 50 amp receptacles for the application suggested. no need to go to a specialty store. Best to install a 50 am and use a "dogbone" adapter down to 30 amp.

RV Electrical
We have 3 AC's and the only time we cannot run all 3 is when the power pedestal is bad. We use about 65 amp when all 3 are running but it is split beteen L1 and L2 for a combined total. Since one 50 amp leg should supply about 6000 watts at 120v and 50 amps, there is a combined 12,000 watts of power on a good pedestal. With only 115v it would be about 5700 watts.
So 50 amps per leg is supposed to be the rule of thumb. As voltage drops so will the supplied amperage.
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Old 07-19-2018, 08:01 PM   #34
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Originally Posted by CoveredWagon View Post
My 2005 Sightseer 29R was wired that way. I added a 4 position rotary switch and wired Shore, Generator and Inverter power to it. This way I can control either power source from inside the coach. It doesn't make much sense to have a generator stat switch inside, but have to go out in the weather to plug into the generator to use it!
IDK if you have a generator outlet, but for those that do -- unless we're connected to shore power DW and I just leave the shore power cord plugged into the generator outlet. Then it's always ready to go.

I wired our MS2000 inverter to be a "whole house" unit. Shore or genset power goes to a Progressive Industries HW30C EMS first; then to the auto transfer switch (ATS) in the MS2000; and then on to the 30A main breaker in the panel.

I realize many/most inverters are not wired this way (and not all can be or should be) but we like it because everything has power 24/7. If we have gen/shore power, the inverter acts as a battery charger. The instant we disconnect from (or lose) gen/shore power, the ATS switches to inverter power -- all outlets remain 'hot', microwave, fridge, etc, all have power.

Needless to say, we don't attempt to run the A/C or water heater on inverter power. Actually, the inverter could do it, but having just 2 GC batteries is the weak link. Still, we can run heavy loads for a short time -- coffee maker, microwave, etc.
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Old 07-19-2018, 11:15 PM   #35
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Thats another question I have, never having had an MH w/generator before.....how often to run the gen and for what length of time to run it.

I've had my MH for 1 1/2 years now. Run the gen a lot. The other day it made a funny noise after starting. When I had a chance I went out to look at it. Took the outside cover off. Found a huge bird nest, up against the air filter. Could have been a fire. Cleaned the nest, no funny noise. Got lucky, this time!

Last year I found a "rats nest" over the gas tank. (that was fun).


P.S. I never wait to "load" the gen. AC, coffee maker or whatever. Once the gen starts, I'm turnin stuff on. So far, so good.
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Old 07-21-2018, 12:40 PM   #36
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Exclamation

Yes, sorry, I said 240 volt and I meant 120 and I'm an electrician!
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Old 07-21-2018, 01:13 PM   #37
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Yes, sorry, I said 240 volt and I meant 120 and I'm an electrician!
It's an easy mistake to make -- especially when one is used to larger outlets like that being 240V.

I can see how -- unless the customer emphasized that it was an RV outlet -- an electrician might wire it for 240V. I know that has happened.

The 50A RV outlet is strange as well -- having 240V available but not using it.
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Old 07-21-2018, 02:37 PM   #38
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Back to the original question about the amp draw. I was just out in my motorhome with the A/C running. It's 94 degrees outside with 32% relative humidity (near Sacramento, CA). My A/C is set at 75 degrees and it was drawing 8 amps while plugged into a 20 amp service. I was very comfortable inside and was cooler than the 75 degree set point with a vent pointed in my direction.

As I mentioned before, my motorhome cord is plugged into a 50', 10ga Marinco 30 amp extension cord. I haven't had any breakers trip.
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Old 07-21-2018, 03:08 PM   #39
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Back to the original question about the amp draw. I was just out in my motorhome with the A/C running. It's 94 degrees outside with 32% relative humidity (near Sacramento, CA). My A/C is set at 75 degrees and it was drawing 8 amps while plugged into a 20 amp service. I was very comfortable inside and was cooler than the 75 degree set point with a vent pointed in my direction.

As I mentioned before, my motorhome cord is plugged into a 50', 10ga Marinco 30 amp extension cord. I haven't had any breakers trip.
Wow, 8A is very low -- especially under those conditions.

What is the BTU rating of the A/C unit?
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Old 07-21-2018, 06:13 PM   #40
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Wow, 8A is very low -- especially under those conditions.

What is the BTU rating of the A/C unit?
It's drawing 10A now and I agree that 8 - 10A is too low.

I think it has two 13,500BTU compressors. If I cycle the compressor 2 breaker, I hear a "starting" noise, but it doesn't seem to kick on. Therefore I believe I'm only running on one compressor. I haven't tried using my generator but, if number 2 doesn't run on the generator, I'll have to assume either the capacitor (hopefully) or something else has failed. My power management system is set to 30A, not 20A, so I don't think that is the issue.

Nonetheless, if it is only running on one compressor, it seems to be enough for now.
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