Switch between two AC sources for one appliance


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Old 10-24-18, 06:18 PM
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Switch between two AC sources for one appliance

Dear friends,

I am hoping to find some sort of switch/device which will allow me to toggle between two completely separate AC sources. If there is such a switch/device which will allow me to either plug two AC male ends into or wire into and a toggle switch to select between the two I would be very indebted to you.

Why do I need this? I have a motorhome and I'm looking for an easy way to switch between shore AC power and inverter AC power without unplugging from the inverter and snaking the electrical cable all over.

Thank you!
 
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Old 10-24-18, 06:27 PM
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A whole house transfer switch (with one big toggle as opposed to six or so little toggles) such as used for a generator will do the trick.

The "common" terminals connect to the appliance (or entire panel top lugs or breaker) to receive the power.

Both the A side terminals and the B side terminals of the transfer switch go to respective male receptacles (inlets) on the outside wall.

Snake the two cables once, one from an inlet to the inverter and the other from an inlet to the shore power (female) receptacle.

For a small 120 volt only load you can use a "3 way switch" instead of a real transfer switch..
 

Last edited by AllanJ; 10-24-18 at 06:46 PM.
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Old 10-24-18, 07:10 PM
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By chance can you link me to the item you mentioned?
 
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Old 10-25-18, 05:50 AM
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Just search for transfer switches and you'll find many options. They are sold online and by most electrical suppliers and big box home centers as they are commonly used with home generator installation.
 
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Old 10-25-18, 06:05 AM
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Do you think this would fit my needs?
Xantrex 8080915
PROwatt SW Auto Transfer Switch https://www.amazon.com/dp/B004S5Y158..._GeB0Bb1KQZEJB

One source of power is my 3000W pure sine wave inverter and the other would be standard 15A 110VAC house power.
 
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Old 10-25-18, 08:37 AM
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Google "furnace transfer switch" for some manual switching 15 amp options.
 
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Old 10-25-18, 10:59 AM
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I've never seen an auto transfer switch like that, so I can't really give an opinion on it.

I would suggest a transfer switch like this (this is what patmurphey referenced)

https://www.electricgeneratorsdirect...01W/p1096.html

It has a switch between line and gen (in your case, shore and gen). Would work great for up to 15A @ 120V (1800w). If you need more, you'll need a larger transfer switch, but same concept.
 
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Old 10-25-18, 11:00 AM
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Old 10-25-18, 11:11 AM
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One thing to take note is that if you use a 15A wiring and switching method, you should include a 15A fuse on the output side of the 3kW inverter. If it actually outputs 3kW at 120V that is 25A which means all of your wiring and switching would need to be rated for at least 30A to prevent overheating.

Other option would be to dig in to the specs on the inverter and see if 3kW is actually a "peak" rating and continuous is much lower. If it is actually a continuous rating you need #10 copper wire and 30A rated switches for 3kW.

I would probably just use a 30A three-way switch with shore hot on one side, inverter hot on one side and motorhome input power on the common terminal. https://www.amazon.com/Leviton-3033-.../dp/B002E8HI56
 
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Old 10-25-18, 05:18 PM
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Thank you for all of this feedback! Regarding the inverter this is the one I have: Power TechON 3000W (6000W surge) Pure Sine Wave Inverter and it says the 3000W is continuous with a 6000W surge, so it seems I must make sure my lines to/from the inverter to the switch be rated at 25A minimum. The single appliance I would be using this for would be a heat pump which draws just under 10A on AC and so I imagine it's only using about 1200W from the inverter.

Would you happen to know what gauge wire that would be? The run is very short at maybe 5 feet max.
 
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Old 10-26-18, 08:20 AM
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If it has a 10A fuse, you can use #14 copper.
 
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Old 10-26-18, 08:46 AM
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For a small load on motor home electric panel use a simple interlock plate. Here is one of many interlocks that can be found on-line: Panel Interlock Kit Kits - for safely connecting generator power without a transfer switch (I made one out of sheet metal)

With interlock installed, plug generator into outlet connected to that dedicated breaker on panel. To connect generator, flip Off main panel breaker, move interlock that kept it in Off position to On position.

For my generator use 30 amp range plug. For power outage, turn off main panel breaker. Plug in generator to outside outlet and turn on breaker along side outlet.

Much cheaper than installing 150 amp transfer switch.

Starting current on many loads is much higher than normal running current. AC motors draw 3 to 4 times at start than run. Would check your load with amp meter.

Always go higher on wire size current capacity. Wire cost very little and those things can make a difference

To avoid building code issues, my generator is on wheels in garage, so Is considered “portable” not permanent installation.
 
 

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