MPP 1012 Wiring Diagram and Questions

[skinnyportagee]

Hi, I am looking to make my first system. My goals with this project are:

1. Learn more about solar
2. Power a few smaller loads (full-time), such as my computer, phone charger, and other small devices at my desk.
3. Act as a backup system if the power goes out for an extended time. For this I would just manually plug in our full-size fridge, charge phones, recharge some flashlights. Not a whole house backup, more like a portable power station.

I bought a Kill-a-watt and my loads seem reasonable for this plan.

I am looking at the MPP 1012LV-MS. My current plan for placement is having the unit in the garage and around 600W ground mount solar array on the side of the house where it would get full, southern facing sun all day. It would require my PV wires be about 40-50 feet. For the short-term I will probably just use an extension cord for the AC output but I'm thinking about wiring a small sub panel with two 15A breakers and dropping two outlets inside the house that I could run some permanent devices on (like my computer).



I had a few questions about these MPP units that I wanted to confirm.

1. If I am going to connect the AC input to an outlet on my main house system, will that sufficiently ground my system? The more I read about this on other threads the more confused I get.

2. On the note of grounding, do I need to do any grounding with my solar panels too?

3. Do I need a fuse between the MPP and the battery on the positive connection? I've seen some videos with and without one. I plan on using a Power Queen 12V 300Ah lifepo4 battery. If I need a fuse, what is the correct way to calculate the size I would need... is it based on a charge controller spec or a battery spec?

4. For my panels, I may look and see if I can find two used 300+W panels, but if not, I can use three 200W Rich Solar panels that I can get off Amazon. The Voc is 24.3. For three that's 73V and the MPP has a max of 102V. That should leave enough headroom, right?

5. The MPP 1012 says it can be over paneled with 800W. To do that I'd need to run four panels in 2s2p. When introducing a parallel connection, do I just use the Y adapters or do I need to use a joiner junction box with fuses?

6. Would 10AWG PV wire be the right gauge?

7. Is there anything I am missing or should be doing differently?

8. I also looked at the MPP 2024 Hybrid but it has a higher idle consumption and might be too big for my needs. Is it better to upsize or would it be ideal to stick with a 12V 1012?

Thanks in advance!

 

[Rednecktek]

I had a few questions about these MPP units that I wanted to confirm.

1. If I am going to connect the AC input to an outlet on my main house system, will that sufficiently ground my system? The more I read about this on other threads the more confused I get.

Yes, your house already has all its grounding stuff in place, the MPP will be able to use that connection.

2. On the note of grounding, do I need to do any grounding with my solar panels too?

Next question. (That's a big can of worms I'm going to pass on.)

3. Do I need a fuse between the MPP and the battery on the positive connection? I've seen some videos with and without one. I plan on using a Power Queen 12V 300Ah lifepo4 battery. If I need a fuse, what is the correct way to calculate the size I would need... is it based on a charge controller spec or a battery spec?

Yes, you'll want a Class-T fuse (or at least a good quality DC breaker) at 20% over the max amperage draw. 1000w / 12v = 83.3a + 20% = 100a

4. For my panels, I may look and see if I can find two used 300+W panels, but if not, I can use three 200W Rich Solar panels that I can get off Amazon. The Voc is 24.3. For three that's 73V and the MPP has a max of 102V. That should leave enough headroom, right?

Yup, unless you're setting up in Antarctica you should be fine. 80v is a good safe number to account for those freezing cold clear mornings where the voltage kicks up.

5. The MPP 1012 says it can be over paneled with 800W. To do that I'd need to run four panels in 2s2p. When introducing a parallel connection, do I just use the Y adapters or do I need to use a joiner junction box with fuses?

With 2 strings you don't need fuses, you'll be fine with either splitters or just sticking both wires into the MPP jacks if they fit.

6. Would 10AWG PV wire be the right gauge?

Beautiful.

7. Is there anything I am missing or should be doing differently?

The wire to the battery can be 4AWG and save you some copper costs. If you have plans to involve anything 12v you'll need a breaker/fuse to feed the fuse block and size that breaker for the total DC loads you'll want to feed. If you can get 2 batteries you'll have more capacity and can step up to a 24v based system easier down the road.

8. I also looked at the MPP 2024 Hybrid but it has a higher idle consumption and might be too big for my needs. Is it better to upsize or would it be ideal to stick with a 12V 1012?

The 2424 is a 24v system which calls for paralleling 2 batteries so make sure your flavor is OK with paralleling (some don't play well with others) but it buys you 2.4Kw of inverter (or 3Kw if you go with the Growatt version) however limits you to needing a buck transformer to get 12v out of it. The 1012 will limit you to about 8a total AC capacity whereas the 3Kw Growatt 24v unit will give you about 26a of available power. If you run any power tools the 1012 will jjjuuussstttt barely be enough if you're careful.

 

[JAS]

Once you have it all connected, keep an eye on the voltage reading that the MPP unit is reading vs. what the voltage really is at the terminals on the unit (not the battery terminals). I have a thread going where the MS version appears to have issues reading the correct voltage. Curious if you see the same issue (under either load and/or charging)?

 

[skinnyportagee]

Yes, you'll want a Class-T fuse (or at least a good quality DC breaker) at 20% over the max amperage draw. 1000w / 12v = 83.3a + 20% = 100a

Rednecktek, thank you so much for your detailed response to all this! Very much appreciated.

To make sure I understand sizing the fuse logic correctly, if I take the MPP 2424 as an example, it has a 2,400W inverter, so that would be 2,400 / 24v = 100A + 20% = 120A fuse. Is that right?

 

[Brazos]

The kind of drawings I understand.

 

[Rednecktek]

Rednecktek, thank you so much for your detailed response to all this! Very much appreciated.

To make sure I understand sizing the fuse logic correctly, if I take the MPP 2424 as an example, it has a 2,400W inverter, so that would be 2,400 / 24v = 100A + 20% = 120A fuse. Is that right?

Yup! I used a 125a breaker because it was what was available at the time but the math is correct.

 

[Bud Martin]

BTW, If you are going to use the circuit breaker between MPP and the battery it will have to be non-polarized since you will have current flowing both directions (charge and discharge).