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Old 06-03-2021, 03:31 PM   #1
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Question Short Bus Conversion - Inverter/Transfer Switch Wiring Question

I've been neck deep in a short bus conversion the last several months and I am finally at the point of installing electrical. Here's what I have...

Progressive Dynamics PD4560 Inteli-Power 4500 Series AC/DC Distribution Panel - 60 Amp
This is kinda an all-in-one unit for AC/DC, shore power. It has the converter/charger built in for when it's plugged into shore power.

Renogy DC On-Board Charger with MPPT Gel, AGM, and Lithium Batteries, Using Multi-Stage Charging, 12V 50A

This will be hooked up to the alternator to charge the battery while driving. Also, I got this unit because I could eventually, easily add solar panels to charge.

Renogy 2000W 12V Pure Sine Wave Inverter


I think I have an understanding of how everything needs to be wired together. I am about to order a 50 amp automatic transfer switch, but am unclear on what to do about the built in charger/converter in the Prgressive Dynamics power center...

Will these "smart" machines just magically talk to each other and figure it out? Can I just flip the breaker off in the power center for the charger/converter when I am not plugged into shore power? Is there a separate device that will address this? Can I have the charger/converter bypass the power center and be hardwired directly to the transfer switch so it only kicks on when plugged into shore power? Is there a better unit of something that I have that addresses this?

See where I'm goin' with this?

I just know that when I'm off-grid, I don't want the 12v/DC house battery to be going through the inverter to 110vAC, to be connected to the Progressive Dynamic power center where it's being converted back to 12v/DC to run the bus appliances and charge the battery...with the same power from said battery. Seems like overkill.

When off-grid, shouldn't the house battery directly be powering the 12v appliances and then be running through the inverter to power 110v? And, would be being charged by either the eventual solar panels or the bus alternator through the DC-DC onboard charger.

Am I making sense or am I just too far down this rabbit hole?

BTW, I don't really ever post on here, but this community has helped me tremendously. My nephew, who is a devout skoolie, recommended it.

Thanks and let me know if you have any questions.

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Old 06-04-2021, 03:56 PM   #2
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I'm not the one to answer this. As simple as I know it is from diagrams and research, the devil is in the details. Basically, this stuff always gives me a headache.

BUT, I can tell you how I've handled almost everything I've never done before. It's the old "How do you eat an entire steak? One bite at a time.".

It sounds like you have all the things you need. If you laid it all out (outside of the bus) to assure all your pieces fit together (visually, not literally), then you can start installing, then connecting, one piece (bite) at a time.

If you do this and take pictures of the layout, then you can add it to this thread and others can actually see what you have and give you better responses.

You can do it! Oh, and so can I.
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Old 06-04-2021, 09:01 PM   #3
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Clarification on your AC/DC distribution panel-I think this is a transformer taking shore power and converting it to DC 12V, correct? If so, good idea but not the only thing needed in conjunction with your Renogy inverter . You won't be able to power receptacles (AC or DC) from this AND from your 2KW Renogy inverter without a transfer switch. If you want your AC and DC circuits to power up regardless of your source of energy, typically you'd use an autotransfer switch (like a GoPower box, about a hundred bucks) which takes inputs from shore power AND the inverter and switches from inverter/battery to shore power if it is sensed. This goes upstream from the AC/DC panel, and resolves your concerns about the inverter inverting inverted power.

I have the same Renogy inverter, and I use an autotransfer switch. On my rig, the shore power goes to a load center(2 breaker, one 20A, one 30A). The 20A is for computer power supplies (see below). The 30A breaker goes into the Autotransfer switch as the normally open (NO) inputs. The Renogy 2K inverter is the second feed, normally closed (NC). This autotransfer box in turn feeds a second load center (two 15A breakers), each of which feeds a 110VAC branch circuit. Voila, AC power, all automagic. The receptacles are fed either by the battery (through the inverter, through the autotransfer, when no shore power is present) or shore power.

I also added two computer power supplies that run strictly off shore power. That's what the first load center 20A breaker is for. They supply 12VDC when shore power is available. Stay with me on this: each 12V device is fitted with a DPDT relay that senses power from the computer power supplies and switches to that 12V source if present. The relays are wired to favor the battery, and switch to the power supplies run by shore power if voltage is sensed. That way, I can literally turn off the inverter when on shore power and everything works as normal, automagically.

Regarding your DC-DC charger/MPPT Solar device, I did it a little differently. I have a 40A Renogy MPPT charge controller and a separate Renogy 20A DC/DC charge controller. I did not want to do the 'combo unit' because I still have concerns about charging off the alternator, even though it's 200A. After some pretty extensive research I decided I needed to see the cruising RPMs before using it since alternators require high RPMs to stay cool during charging. The DC/DC controller just has a switch line you hook up to the run circuit-basically it will be charging at max amps even when the rig is sitting idle, and that's a formula for alternator failure. I want to have it kick in at a reasonable cruising speed so it can stay cool, so I need some kind of switch that triggers off RPM. I also chose the 20A unit because that was another factor in alternator failure. If you charge at a really high rate it stresses the alternator. I expect to be driving long distances so I can let charging take a while--a slower charge should not be a factor. I have not installed the DC/DC charge controller yet.

Others may have different approaches to work around these issues. Feel free to message me if you want to discuss any of this on the phone.
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Old 06-05-2021, 11:18 AM   #4
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Rucker, I agree with your not wanting the DC DC charger operating at low rpm's. I also don't want it running until the start battery has been charged back up after a start. My Sterling battery to battery charger makes a provision for a manual on/off overide switch that I control. I suppose the manual switch could be replaced with a voltage triggered switch but I've got nothing better to do anyway.

Since I can't fit a worthwhile amount of solar in/on my bus I went with a manual change shore/inverter/genny. Once installed its a complete no brainer with no way to have things get mixed up unless I start probing recepticles with paper clips.
Jack

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