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Old 06-28-2017, 05:10 PM   #1
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Default Wiring inverter to receptacles using auto transfer switch

I'm looking to add an inverter to my FF to power only the 110v receptacles i.e. for charging phones, laptops and powering the TV. I want to use an automatic transfer switch in order to transfer between shore power and inverter power, however I only want to have the inverter power the receptacles i.e. I don't want the inverter connected to the fridge, A/C, microwave etc.

So can I leave the existing shore power line coming into my distribution panel as-is, but connect the output from the transfer switch to just the 110v breaker that supplies the receptacles? My thinking is that with no shore power connected and the inverter on I'll only get live receptacles, which is what I want. But then if the inverter is on, and shore power also comes on, the transfer switch should divert over to shore power thereby isolating the inverter. The 110v breaker supplying the receptacles would then have two 110v inputs (direct shore power and from the transfer switch) but is that an issue? I'm hoping that would be a parallel circuit thus keeping the voltage at 110v rather than forming a 220v series circuit. Any ideas? Or am I trying to shortcut this and I'll need a separate distribution panel or something?

Cheers
Simon
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Old 06-28-2017, 06:12 PM   #2
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Ah I think all I need to do is disconnect the existing 110v input and replace it with the output from the new transfer switch. Hopefully just answered my own question
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Old 06-28-2017, 09:12 PM   #3
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Simon- Although it sounds like you are well on your way to adding your inverter, I wanted to point out that you can use the existing 12 volt DC system to charge both your phone and laptop with the appropriate charger. Converting 12 volts DC to 110 volts AC than back to DC to charge your phone and laptop is extremely inefficient. As for the TV, there are numerous TV models that run directly off 12 volts DC. For example, I have a small 7 inch TV that I use when I dry camp that runs off of 12 volts. Anyway, good luck with your mod.
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Old 06-29-2017, 06:16 AM   #4
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Quote:
Originally Posted by twinster2 View Post
Simon- Although it sounds like you are well on your way to adding your inverter, I wanted to point out that you can use the existing 12 volt DC system to charge both your phone and laptop with the appropriate charger. Converting 12 volts DC to 110 volts AC than back to DC to charge your phone and laptop is extremely inefficient. As for the TV, there are numerous TV models that run directly off 12 volts DC. For example, I have a small 7 inch TV that I use when I dry camp that runs off of 12 volts. Anyway, good luck with your mod.
I was going to say the same thing. I have this TV https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 runs off of 12 Volts no issue. There should be a 12v outlet right next the antenna connection for the TV

Here is the 12 volt power supply for my laptop.
https://www.amazon.com/dp/B003KR3Q4M...=1G18QZXC0QQYU

Just google your laptop model and 12 volt power supply.

The car charger that you use for your phone now will charge your phone in your trailer once you add additional outlets.

It is very easy to add additional 12v outlets through out you trailer. Just make sure you use at least 16 AWG wire to feed them. My trailer has additional fuse locations in the inverter to add addition circuits. use a 10 amp fuse for 16 AWG wire. That should be good enough to power every 12v item you need. if not go to 14 awg and a 15 amp fuse.

https://www.amazon.com/Cllena-Functi...12+volt+outlet

https://www.amazon.com/Custom-Access...12+volt+outlet

for outside
https://www.amazon.com/Marine-Grade-...12+volt+outlet
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Old 06-29-2017, 08:50 PM   #5
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Thanks for the suggestions. I couldn't find a smart TV that runs on 12v, and, although I didn't mention it in my original post, we also have a few 110v kitchen appliances (Vitamix, coffee grinder etc) that I'll want to power off the inverter. I might install some 12v receptacles in any event just to charge phone though as going DC to AC to DC is grossly inefficient.

Cheers
Simon
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Old 06-29-2017, 08:59 PM   #6
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I was right in that I need to disconnect the AC side of my distribution panel somehow, but I didn't realise that I have to avoid having the converter (that transforms 110v shore power to 12v to charge the house battery) connected to 110v inverter power. I've had a look at my setup and this is a simple diagram as it is now:


Link here if the diagram doesn't appear

Shore power comes in to the top of the AC breaker panel and the converter gets its 110v supply from the load side of the GFI breaker. The converter then supplies the DC distribution panel and charges the house battery. Easy.

Here's what I think I need to do to install an inverter to just power the 110v receptacles so we can charge phones, run our kitchen appliances and watch TV:


Link here if the diagram doesn't appear

So, I plan to disconnect the existing shore power line in from the Main breaker and disconnect the converter from the GFI breaker output. I'll have the converter connected directly to shore power so it will only charge the battery and power the DC distribution panel when shore power is live i.e. the converter is isolated from the inverter output.

I'll use an automatic transfer switch with the output going into the Main breaker. This will automatically choose between inverter power and shore power, with shore power winning if they're both live at the same time. Finally, to avoid the A/C, Microwave etc from using inverter power I'll install a triple pole single throw relay on the load side of the A/C, microwave and conv. W/H breakers with the coil triggered by shore power. The relay will be normally open so only when it's energised from shore power will the three circuits close those high power circuits. The receptacle circuits won't have a relay as I want them to be power from the output from the transfer switch and work on either inverter power or shore power.

Is there anything I've missed?

Cheers
Simon
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Old 07-03-2017, 10:00 PM   #7
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Default New plan

So I had another think and didn't like having a giant relay/contactor in my RV so I've decided to split out the receptacles and GFI receptacles to a separate sub-panel.

So now the transfer switch output feeds into the new sub-panel avoiding the issue of powering the converter with the inverter and creating a battery-killing feedback loop. The transfer switch is normally closed on the shore power side then when it sees power from the inverter it switches over to the inverter. I'm pretty sure this is the easiest and safest way to wire this all up.

I think this is actually the easiest way of wiring it up as all I need to do with the existing distribution panel is pigtail the shore power into the transfer switch and then move the receptacles/GFI receptacles output over to the new sub-panel. I've already run the 2/0 AWG DC cables from the battery to the inverter and 12/2 romex from the inverter to the panel so when the inverter arrives in a few days I can hit the ground running.

Oh, in the diagram I missed out the breaker for the inverter which will be a 180A breaker on the DC positive close to the battery.


Link

Cheers
Simon
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Old 07-05-2017, 09:19 AM   #8
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How many, and what size, batteries do you have.
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Old 07-05-2017, 09:22 AM   #9
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I have two T105 6v golf cart batteries in series and another 12v deep cycle marine batttery.
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