Schematic safty check.

[nycsteve]

From what I can see. You should be fine with 12 AWG across the board. But 10 AWG would provide a larger margin of overhead. You only have something like 13-14 amps being used if all devices are on at the same time. 12 AWG THHN is good for 20 amps. 10 AWG THHN is good for 30 amps

Adjust your MRBF to the amp rating of your wire. 20A for 12 AWG and 30A for 10 AWG

Then the individual fuses in the fuse block can be sizes for each appliance. The fridge can be a 15A, TV at 5A and phone charger 1A. If the phone charger or any other appliance is being plugged into a 12V socket then you can fuse the socket at the socket rating plus 20% overhead or the next sized fuse above that if no fuse size matches

I'd use 10 AWG myself

Excellent! Thank you. Almost all the ducks are in line!
A new bit of info came to light. I reached out to Dometic , the refrigerator manufacturer and asked about amps required for the fridge. I will include a picture of their response. Mine is the NRX 130. It appears the max amps for the compressor in my model is in freezer mode and is 6.7 amps .
I added the amps of the 3 devices , plugged the number into the wire size calculator and the magic number was now 10 AWG. Which agrees with your suggestion.
I was thinking about MisterSandals saying the Ah/Hr of 1.29 seemed very low. Perhaps after the refridge expends energy in the cooldown which takes 4 hours , maintaining that cold level , in ideal conditions , is where they get that number.
So the MRBF on the battery positive should be 30A as the wire will be 10AWG .
How about the breaker/isolator being used as an on off switch between the panels and the controller , 30A as well?
Again , thank you so much. 120v home electric is so much easier

 

[Backyard]

Use whatever breaker size you want for the panel disconnect/isolator as long as it's at least 20% above the total short circuit current of both panels. There's not really any situation where that breaker is going to actually do any protection as the panels are self limiting on current and will not generate enough to trip the breaker. Your panel arrangement doesn't require any breakers or fuses. So, in your case it's just a switch. 20-30 amps will work fine

 

[nycsteve]

Use whatever breaker size you want for the panel disconnect/isolator as long as it's at least 20% above the total short circuit current of both panels. There's not really any situation where that breaker is going to actually do any protection as the panels are self limiting on current and will not generate enough to trip the breaker. Your panel arrangement doesn't require any breakers or fuses. So, in your case it's just a switch. 20-30 amps will work fine

Perfect. Thank you. Think I got it

 

[robbob2112]

Pretty much all devices that heat or cool have a duty cycle --- on time to off time.... So there is a thermostat in the fridge that just turns on at one temperature and off at another ... there is a spread in there that can vary from one mfg to the other ... sometimes it is adjustable .... but a 4 degree spread with a setpoint of 35 degrees would mean it bounces between 37 and 33 degrees ... So turn on when the temp reaches 37 then off when it reaches 33 .... If the spread is to small the fridge will cycle to much... or if it is cheaply manufactured and isn't insulated well enough it will loose the cool quickly and the compressor will cycle on and off frequently.

Typical fridges have a 40/60 duty cycle -- so on 40% of the time and off 60% of the time... If you take the yellow tag rating from the new fridge and divide by 365 that gives you the daily usage and then divide by 24hrs and that gives you the watts used.... This should pretty closely match what the quoted watts are in the specs sheet.

They don't count the initial cool down time in that yearly number because they assume you don't turn it off and let it get warm ever.

If you are using a 120vac fridge you can use a kill-o-watt meter and just plug it through that to get the actual wattage used. Don't be surprised if it is actually a bit lower than either the yellow tag or the stated wattage --- they usually state the max wattage for both and the average unit will be 5~10% lower than that.

Heaters for water and a furnace or a mini-split all work the same way --- thermostat, duty cycle, and spread...

 

[MisterSandals]

Wires are sized based on the current, insulation, allowable temperature rise and acceptable voltage drop. Not wattage

Yes, thanks, that could have been written better. The point I was trying to make was that 16W (1.29A) wasn’t a realistic (to me anyway) power number, but the label’s 10A rating (120W) seems more accurate.

 

[Backyard]

Yes, thanks, that could have been written better. The point I was trying to make was that 16W (1.29A) wasn’t a realistic (to me anyway) power number, but the label’s 10A rating (120W) seems more accurate.

Yeah. But I think the OP was getting confused on how or what measurements to use as he was wall over the place. So, just wanted to put that little bit in there. Looks like the fridge issue is sorted out

 

[nycsteve]

Yeah. But I think the OP was getting confused on how or what measurements to use as he was wall over the place. So, just wanted to put that little bit in there. Looks like the fridge issue is sorted out

Certainly correct on the confusion.......
The fridge manufacturer turned out to be quite responsive , sending along additional info on their own. I received this late in the day yesterday,
" Dometic recommends 14 gauge wire if the run is shorter than 13' , if the run is over 13' we suggest 12 gauge wire"
I'm planning on a 16' run from the battery to a fused block using 10AWG as discussed. It will be an additional 3' to 4' from the fused block to the fridge. Any issues using 14 gauge from the fused block to the fridge?

 

[Backyard]

Certainly correct on the confusion.......
The fridge manufacturer turned out to be quite responsive , sending along additional info on their own. I received this late in the day yesterday,
" Dometic recommends 14 gauge wire if the run is shorter than 13' , if the run is over 13' we suggest 12 gauge wire"
I'm planning on a 16' run from the battery to a fused block using 10AWG as discussed. It will be an additional 3' to 4' from the fused block to the fridge. Any issues using 14 gauge from the fused block to the fridge?

Sounds like the manufacturer wants to keep the volt drop under a 1/2 volt. Using this, you can calculate the voltage drop on the 10 AWG line first, then the 14 AWG next. It looks close with all the loads on, but still within the limit.

 

[robbob2112]

Were it me I would play it safe and run 12awg from the panel to the fridge ... then the combination of 10 and 12 gauge wire meets what the mfg wants without having to mess with thing.

 

[nycsteve]

Were it me I would play it safe and run 12awg from the panel to the fridge ... then the combination of 10 and 12 gauge wire meets what the mfg wants without having to mess with thing.

When you say panel to fridge , it would be from the battery straight to fridge ( with a inline fuse) ? Then I can run a second 12G to the fused block for the TV and phone charging. Can I stick with the 30A MRBF on the battery positive or should I switch out to a 20A?

 

[robbob2112]

no,

10awg from the battery to your fuse block that is close to the fridge
12awg from the fuse block to the fridge

And I would use a 30amp MRBF on the battery....

does the fuse block have a master fuse or current rating? My point being if the fuse block has a 20amp limit you can't put a larger fuse at the battery unless the fuse block also supports the 30amp current. Otherwise if you put 30amp fuse on a line feeding a fuse block that is only rated for 20 amps and that fuse block doesn't have a master fuse you could melt it before the wire even heats up.


Normally you will hear over and over fuses protect the wires.... but in this case you have to make sure you don't overtax the fuse box as well and treat it as an extension of the wire.

 

[nycsteve]

no,

10awg from the battery to your fuse block that is close to the fridge
12awg from the fuse block to the fridge

And I would use a 30amp MRBF on the battery....

does the fuse block have a master fuse or current rating? My point being if the fuse block has a 20amp limit you can't put a larger fuse at the battery unless the fuse block also supports the 30amp current. Otherwise if you put 30amp fuse on a line feeding a fuse block that is only rated for 20 amps and that fuse block doesn't have a master fuse you could melt it before the wire even heats up.


Normally you will hear over and over fuses protect the wires.... but in this case you have to make sure you don't overtax the fuse box as well and treat it as an extension of the wire.

It appears that it supports 30A. But to be sure I'm interpreting specs correctly here is the printed material from fused block.

 

[robbob2112]

That says the inputs can be 100amps with the right size wire...and any of the loads can be 30amps so long as they don't exceed 100amps.

 

[Backyard]

Just feed the fuse block with 10 AWG and 30A fuse. Then 10 AWG from the fuse block to the fridge with a 15A fuse. Keep it 10 AWG for minimal voltage drop.

Making it more complicated than it needs to be

 

[nycsteve]

Thanks guys. Waiting on one more Amazon package before starting. I appreciate the help to get this far .

 

[nycsteve]

Just feed the fuse block with 10 AWG and 30A fuse. Then 10 AWG from the fuse block to the fridge with a 15A fuse. Keep it 10 AWG for minimal voltage drop.

Making it more complicated than it needs to be

One last question. With the MRBF ..... the wire from the positive of the battery to the controller , I will be attaching directly to the battery terminal before the protected side of the fuse?

 

[robbob2112]

The mount bolts to the battery terminal... the fuse holder bolts to the top of the mount --- if you look closely you will see that the stud that goes through the fuse doesn't touch the fuse element... so the current path is terminal---holder---fuse---lug to whatever.

 

[nycsteve]

The mount bolts to the battery terminal... the fuse holder bolts to the top of the mount --- if you look closely you will see that the stud that goes through the fuse doesn't touch the fuse element... so the current path is terminal---holder---fuse---lug to whatever.

Thanks. Wanted to be sure. Hopefully it's all going together tomorrow.