Solar Retrofit for a 2017 Imagine

[mpking]

howson , here's where all those AWG questions come into play.

So I have a 2017 Imagine 2800BH. It's the first year they had a solar package, which for my particular unit has the Furrion 10A plug on the side of the camper, wired directly to the battery (No fuses, no circuit breakers) using a 10AWG wire. (Near as I can tell, bit hard to figure that part out). I will refer to this wire as the "Solar Wire" from now on.

I have a Renogy Rover 20A MPPT left over from my previous camper, and a 100w Mono solar suitcase. The Rover wire terminal only accepts up to 8AWG wire.
I'm going to mount the MPPT on the backside of the Universal Docking Station, and I also want to install a BlueSea Fuse Panel on the same place to provide some power for some of the mod's I've got going on. (USB Chargers in the bedroom, power for the Levelmate PRO, power for a TPMS repeater)

I'm going boondocking 4 or 5 weekends over the next two months, and I need to get this done in a hurry, and I have little to no freetime.

I've come up with 3 plans of attack.
All three have a common question:
Do I put a fuse on the Solar Panel Side of the MPPT? The Furrion is rated at 10A.

So Plan "Reuse OEM" is just that.
Cut the Solar wire in the middle, and insert the MPPT there. Pretty simple actually. Doesn't get me the full 8AWG wire the unit is capable of, but it's very simple to pull off.
The 20A circuit breaker is based on Renogy docs (They recommend matching the breaker to the battery bank to the size of the MPPT)


Plan "Use the OEM Disconnect, Option A" is:
Cut the Solar Wire, connect to the MPPT. Either chase and remove the now unused leg coming from the battery, or disconnect it and tape it up.
Utilize the larger 8 AWG wire used for the disconnect, and connect that to the Battery side of the MPPT. This option has me connect to the Unswitched side of the Battery Disconnect, so unless the Breaker is flipped, the MPPT always has power.
The 20A circuit breaker is based on Renogy docs (They recommend matching the breaker to the battery bank to the size of the MPPT)

Plan "Use the OEM Disconnect, Option B" is:
Cut the Solar Wire, connect to the MPPT. Either chase and remove the now unused leg coming from the battery, or disconnect it and tape it up.
Utilize the larger 8 AWG wire used for the disconnect, and connect that to the Battery side of the MPPT. This option has me connect to the Switched side of the Battery Disconnect, so the "Master Disconnect" is truly that, it will kill the MPPT as well.
The 20A circuit breaker is based on Renogy docs (They recommend matching the breaker to the battery bank to the size of the MPPT)


I'm personally leaning towards "Use the OEM Disconnect, Option A"
No real downsides, utilizes the bigger gauge wire. It's a little more work, but nothing more than an extra hour.

Help me not do anything stupid.

Mike

[mpking]

I'm looking at getting this Blue Sea Fuse Block
https://amzn.to/3xRm981

Anyone got a line on a 20amp breaker? I'm only finding 25A and larger on Amazon.

[howson]

mpking

Short answer: IMO no fuse is required between the panels and MPPT in any of the scenarios.

Long answer: What I'm about to write is what I've learned from reading a lot of material from people much smarter than me.

A fuse is there to protect wiring. Normally, a fuse is inserted into a circuit that has what could be called an unconstrained power source. A vehicle battery that shorts puts out a tremendous amount of power in a very short time. A battery's power can be unconstrained. Without a fuse in the circuit wiring subjected to an unconstrained source could melt or burn, leading to the possibility of a fire.

A solar panel is not an unconstrained power source. It's limited. That maximum output is normally documented in the specifications. You'll see terminology like "Short Circuit Output". TheRenogy I use has a maximum current output of 6.10 amps. It can't be higher than that from the panel--it's not possible (unless it's hit by lightning, the panel comes in contact with another power source, etc, but those are different problems).

So if the wiring is capable of handling 6.10 amps (the maximum it will ever see from one panel), why put a fuse in it?

If you put in a 5 amp fuse, it will blow when the panel is just reaching it's maximum possible output (6.1 amps). That would be a nuisance.

If you put in a fuse that's 10 amps, it will never blow. The panel can't reach 10 amps (without something from the outside being introduced).

However...Zamp uses fuses in their solar panels and Renogy has a "Maximum Series Fuse Rating" of 10A. I don't understand why Zamp has a fuse in their panel, but I think I understand why Renogy has a Maximum Series Fuse Rating. Keep reading!

I've used a simple scenario with only one panel in the example above. If an individual put 10 of the Renogy panels in parallel and in a junction box ran a wire to the MPPT...that could be up to 61 amps at maximum output. The answer here could be different according to https://www.explorist.life/how-to-fu...y-not-need-to/



The Explorist article is quite good with excellent graphics. But I must admit it doesn't make any sense (to me). I can't envision how the fuses will ever blow where they are inserted in the circuit.



As long as the output wiring from the junction box to the MPPT can handle the maximum output of the entire array if all the panels short simultaneously...how can there be a problem?

Again, from information I gleaned from a source much smarter than me, the genesis of the NEC code language is directed at home-based systems connected to the grid. The NEC language was not meant for the relatively small systems in RVs...but I'm not qualified or smart enough to figure any of that out or judge the validity of what they said.

On a side note, I recommend installing a switch between the panel (or junction box) and the MPPT. Every controller manual I've read mentions that battery power is applied before PV (solar panel power). Turning the MPPT off is the opposite--remove PV and then turn off battery power. Having a switch between the panels and MPPT makes this easy to accomplish. A circuit breaker is recommended between the MPPT and battery bank. (The battery bank is potentially an unconstrained power source.)

So the real consideration then IMHO is wiring. According to charts online and using the Critical criteria for solar wiring (3% voltage drop maximum over the wire run) 10ga wire can carry up to 15A in lengths up to about 20'. 20A to 15'.

Use high quality copper connections, too! With solar it's very important to use the best wire and connections you can afford.

TucsonJim

gbkims

or anyone else--is there another consideration I'm missing or is there another perspective on the fusing issue? I'm still learning...

Howard

[mpking]

mpking

On a side note, I recommend installing a switch between the panel (or junction box) and the MPPT. Every controller manual I've read mentions that battery power is applied before PV (solar panel power). Turning the MPPT off is the opposite--remove PV and then turn off battery power. Having a switch between the panels and MPPT makes this easy to accomplish. A circuit breaker is recommended between the MPPT and battery bank. (The battery bank is potentially an unconstrained power source.)

So the real consideration then IMHO is wiring. According to charts online and using the Critical criteria for solar wiring (3% voltage drop maximum over the wire run) 10ga wire can carry up to 15A in lengths up to about 20'. 20A to 15'.

Use high quality copper connections, too! With solar it's very important to use the best wire and connections you can afford.

If I go to permanently mounted Solar Panel's, I will keep this in mind. However, for this particular setup, I'll do without a switch because I can physically unplug the Solar Panel. But thanks for that Idea for my long term plans.

I started price shopping wire. I had no idea that people were trying to pass CCA off as "good" wire. (Copper Clad Aluminum wire). Thanks for the heads up.
I think I'm going with this company:
https://amzn.to/2UEXEwz

I'm still looking for a good circuit breaker, and now I'm looking for lugs. Do they make 8AWG lugs that don't require a special crimp tool? Or, do someone have a good / inexpensive crimp tool set?

[Yoda]

I'm looking at getting this Blue Sea Fuse Block
https://amzn.to/3xRm981

Anyone got a line on a 20amp breaker? I'm only finding 25A and larger on Amazon.

You can find better pricing. I used the 12 circuit one with negative and cover on in my install. https://www.continuousresources.com/...ue-sea-systems

They also carry the breaker you need along with a lot of other parts.
Keith

[mpking]

You can find better pricing. I used the 12 circuit one with negative and cover on in my install. https://www.continuousresources.com/...ue-sea-systems

They also carry the breaker you need along with a lot of other parts.
Keith

Hmm.... It's a dollar cheaper, but I'd have to pay shipping.

Also, the breaker they have is 25A.... No 20A one.

I'm guessing I'm going to have to do a 25A circuit breaker if I want one this style. Otherwise, I'll have to move to the round glass type like this: https://amzn.to/3gXML1I

[Country Campers]

mpking

Here is a 20 amp breaker Amazon.com: wohhom Hi-Amp 20Amp Circuit Breaker 12V-32V DC Waterproof, 10-300A Fuse Inverter with Manual Reset Button for Auto Truck RV Marine, Panel Mount (20A): Automotive Not sure if this is what you are looking for.

Brian

[Yoda]

Hmm.... It's a dollar cheaper, but I'd have to pay shipping.

Also, the breaker they have is 25A.... No 20A one.

I'm guessing I'm going to have to do a 25A circuit breaker if I want one this style. Otherwise, I'll have to move to the round glass type like this: https://amzn.to/3gXML1I

Try morris15 or morris10 discount code (may be all caps) its been a while but worked before. Their shipping costs are not bad either and no tax that I know of. They also can do package discount deals if you call them. Nice folks

[mpking]

mpking

Here is a 20 amp breaker Amazon.com: wohhom Hi-Amp 20Amp Circuit Breaker 12V-32V DC Waterproof, 10-300A Fuse Inverter with Manual Reset Button for Auto Truck RV Marine, Panel Mount (20A): Automotive Not sure if this is what you are looking for.

Brian

I looked at that one. It's a panel mount. I can do a panel mount, but I was really looking for a surface mount. I didn't want to cut a big hole.

[mpking]

So while everyone got bogged down in my circuit breaker woes, I think we missed my original question.

Which of those three plans would you recommend?

[howson]

Which of those three plans would you recommend?

The Reuse OEM is how mine is wired. (Doesn't mean it's the best or the "right" way.)

The only difference appears to be the additional shutoff between the batteries and everything else in my setup. You can see it in the solar portion of my Comprehensive Electrical Diagram. https://gdrvowners.com/forum/operati...lts-f-350-mods

[mpking]

Silly question.
While hunting for a chassis ground, I've discovered the aluminum framing is showing good ground.
Anyone think this is a horrible to use this? It's REALLY close to where I'm working, and I don't have to scuff the paint to pull a good ground.

[Country Campers]

Mike

I would not recommend using the aluminum frame work for your grounding needs. The aluminum frame is bolted thru the floor structure into the chassis frame. Maybe others may think this might be ok , but I would not do it.

Brian

[mpking]

Thanks. I ran a strap to the frame, and used a self tapping screw to get it in to the steel. I didn't feel confident with the aluminum, hence why I asked.


I mounted the 25Amp breaker next to the disconnect:



I decided to mount the MPPT and the fuse panel inside the Universal Docking Station.

I had some concerns with the heat, but there is a good 2 inch opening at the top to allow airflow, so I'm not super concerned about it.

I've never accessed the front panel of the MPPT, since I use the bluetooth dongle, and I'm not expecting to blow any fuses up here. Right now it's just 2 USB ports (not wired up yet), and if they pop, I know where to look.