120V Inverter Integration

[Uncivileng]

Hi Electrical Wizards,

I'm in the process of planning/procuring my electrical system components and am having some issues planning my AC and DC setup. I want both 12V DC and 120V AC in the trailer, basically at all times, with the 120V being fed from shore power when it's available and from an inverter when boondocking/shore power unavailable. Yes, I could get by without 120V when away from shore power, but I am looking to have everything available in this trailer from the start. I don't want to regret not putting something in now.

I have already purchased a Progressive Dynamics PD4045 which I was intending to use for my 12V and 120V distribution. This would also charge the batteries when plugged in to shore power, and provide 12V power without using the battery. Seemed like a good solution initially and then the integration of an inverter came into play.

The problem I have is where can I integrate the inverter in the system to provide my 120V? I was hoping to utilize the PD4045 for all of my 120V distribution, meaning I would feed my inverter into the 4045 so that all the outlets in the trailer work the same on shore power or battery. However, while boondocking this setup leads to the inverter pulling from the battery to provide 120V AC to the PD4045 which sees the AC and then wants to charge the battery... not good, and on shore power it would mean the inverter is also feeding the 120V panel.. even worse.

The solutions I've seen mentioned / thought of:
1) Get a DPDT switch that can switch the inverter on and disconnect the PD4045 converter. This way I have 120V AC and the converter when on shore power, and when boondocking, throw the switch and now I have 120V AC from the inverter, and the PD4045 converter disconnects and it can't try to charge the batteries. A problem could arise if plugged in to shore power, and the switch is thrown turning on the inverter. Now I would be supplying two 120VAC sources to one bus bar. I'm no electrician, but I am thinking this could let out that magical smoke which makes all things electronic work.

2) Don't feed the inverter to the PD4045, and supply power from the inverter separately. This will mean using split outlets, or separate outlets for shore power and inverter power. This keeps things separate and no need for switches, but I will have to remember which outlets are which. I could also get an inverter with transfer switch, and have it fed from the battery and the PD4045 which would pass through the 120V when on shore power. This way all outlets are live on shore power and only some on battery power. No possibility of two AC sources on the same bus.

3) Return the PD4045, get an inverter that charges the battery and has an automatic transfer switch which will run all of my 120V AC, and charge the batteries on shore power (like this Renogyhttps://ca.renogy.com/2000w-12v-pure-sine-wave-inverter-charger-w-lcd-display/). Then just have a simple fuse block for my 12V distribution, and a small 120V panel for breakers and distribution (or none at all). The downside to this is the inverter has more components and will be more expensive to replace if a part of it goes. (I kind of have that problem with the PD4045)

4) A combo of 1 and 3. Toss the 4045, get a 12V fuse block, 120V panel, battery charger, regular inverter without transfer switch, and a DPDT switch. Have shore power and the inverter tied into the panel, with the DPDT switch set up as before. On shore power you can charge batteries, have 12V system, and 120V system. On battery, throw the switch and now the inverter provides 120V and the battery charger is disconnected. This has the cheapest components and each is easily upgradable and replaceable, but has the same problem as before and possibly supplying two 120V phases to the same panel.

Would appreciate some thoughts and feedback from anyone who has a similar setup or another solution I'm missing.

[bdosborn]

Option 1:
I made my own transfer switch use a multi-pole switch. Now it looks like you can just buy them:

Rotary Transfer Switch



I prefer the manual switch because it doesn't use any power like an Automatic Transfer Switch and it's a break before make switch so you don't risk ever paralleling the inverter with shore power and letting the smoke out.

Bruce

[saltydawg]

Just put the transfer switch after the pd thingy. The inverter is going to be self limiting for power output, there is no need to run the power out from the inverter thru a breaker.

So shore power to pd thing, then to transfer switch, then to the outlets. You only really need one circuit for the outlets in a tear drop anyway.

[Uncivileng]

Thanks for the input guys. I'm starting to lean toward returning the PD4045 and going a more diy approach. I don't think I'll get that much use out of the PD4045 to justify the cost. And Saltydawg is right, I won't really need multiple circuits. I'm thinking 2 outlets in the galley and two in the cabin will be all I'm needing. Won't be using too many high draw appliances, and easy enough to make sure not to use two at the same time. That's easily accomplished with 14awg wire, but will probably run 12 anyways.

That rotary switch looks good bdosborn, definitely cheaper than a dpdt switch at the orange home improvement store. I'm jealous of the selection you get, and how cheap things are in the US. Being up in Canada, everything seems to cost just that much more, and options are limited.

I'll have to do up a detailed wiring diagram now. Any suggestions on free software that is easy to use for making electrical schematics?

[saltydawg]

I used the below switch. power comes from the shore plug ( 20 amp ) to a plug, my charger is plugged in to that plug. Then it goes to the switch below on one side, my inverter is on the other side, the normal use plugs are on the common. I have a switch on the 12 volt side of my charger so I can prevent it from charging if I want to. The switch is rated to 18 amps at 120 v. I have run a 900 watt heater thru it for weeks with no issue yet.

I also went a little silly and put a 12 volt wall wart in the plug that the charger is plugged in to and one in my inverter. this lights which ever led on the switch has power from the wall wart, or both. it gives me an indication that the inverter is on and or the shore power is plugged in.https://www.amazon.com/GAMA-Electronics ... 201&sr=1-5

[Shadow Catcher]

I did 1) Get a DPDT switch that can switch the inverter on and disconnect the PD4045 converter. 30A and it works well. The inverter sits next to the battery in the tongue box with a 120AC running to the DPDT switch next to the 4045 in the galley.

[Uncivileng]

I did 1) Get a DPDT switch that can switch the inverter on and disconnect the PD4045 converter. 30A and it works well. The inverter sits next to the battery in the tongue box with a 120AC running to the DPDT switch next to the 4045 in the galley.

Shadow Catcher, I saw one of your posts for the DPDT switch. That was a great idea. Looking through your pictures, it looks like you have a PD4045 or similar. Would you recommend it?
Do you have your inverter fed into the 4045? Do you know of any way to disconnect both the shore power feed and converter at the same time when the inverter is turned on?
Or maybe I'm just worrying too much about the inverter and shore power at the same time.

Edit: the switch that bdosborn posted can disconnect / connect two circuits simultaneously if used for just the hot wires not neutrals. It should work for what I'm looking to do.