First timer with questions on wire gauges

[Mikep4485]

hi everyone! I’ve been learning a ton from YouTube and reading everything I can on here. I’m putting in a new solar project and I think I have it figured out except one part. Im putting 12 480 watt panels connected to an eg4 6500ex and a power pro 14kwh battery. My issue is I would like to have a pro Tran 2 or similar transfer switch put in the garage to run a mini split and be emergency power for outages. i live in central Florida so my garage can get to be extremely hot in the summer, too hot for most inverters. The only room I can put the inverter in about 75 feet through the attic to where the transfer switch would be. What gauge cable would be needed to go that far and be able to run the mini split and maybe a refrigerator and small chest freezer. thanks for any info!

 

[timselectric]

hi everyone! I’ve been learning a ton from YouTube and reading everything I can on here. I’m putting in a new solar project and I think I have it figured out except one part. Im putting 12 480 watt panels connected to an eg4 6500ex and a power pro 14kwh battery. My issue is I would like to have a pro Tran 2 or similar transfer switch put in the garage to run a mini split and be emergency power for outages. i live in central Florida so my garage can get to be extremely hot in the summer, too hot for most inverters. The only room I can put the inverter in about 75 feet through the attic to where the transfer switch would be. What gauge cable would be needed to go that far and be able to run the mini split and maybe a refrigerator and small chest freezer. thanks for any info!

The Pro Tran 2 appears to be rated for 50a.
#8 copper or #6 aluminum.

Edit: it looks like there are different sizes available.
Need to know which one you are going to use. Before we can recommend a conductor size.

 

[Mikep4485]

When I’m doing a wire gauge calculator do you just use the max amps from the transfer switch?

if I were going to use the reliance 30 amp pro Tran 2

 

[timselectric]

When I’m doing a wire gauge calculator do you just use the max amps from the transfer switch?

Yes, conductors are rated for amperage.

if I were going to use the reliance 30 amp pro Tran 2

#10 copper.

 

[Mikep4485]

last question on this, if the largest breaker I’m moving over is 20 amps, the 30 amp switch is fine right? Even if I have all 6 of the breakers in use and they are all 15 and 20 amp breakers I won’t run into any trouble? Just need to keep the individual breakers below 30 amps?

 

[timselectric]

It will be safe. But it won't hold up to everything running at full load. It will trip the 30a feed breaker.

 

[Mikep4485]

So if I were doing a mini split, refrigerator, a small chest freezer, as well as a couple lights would the 50 amp switch be a better choice? Also, thanks for the help with my other questions

 

[zanydroid]

So if I were doing a mini split, refrigerator, a small chest freezer, as well as a couple lights would the 50 amp switch be a better choice? Also, thanks for the help with my other questions

If you balance the 120v legs the 30A switch has a pretty decent chance to be OK. Mini split is the largest power load. Fridge and chest are under 300W each. They do have a high surge though but that doesn’t affect breaker sizing. Everything else is pretty low. LED lights are pretty irrelevant from load calculation angle.

Did you calculate the load?

 

[timselectric]

So if I were doing a mini split, refrigerator, a small chest freezer, as well as a couple lights would the 50 amp switch be a better choice? Also, thanks for the help with my other questions

The 50a will always be better.
But, could be more than needed. It's hard to guess without knowing what your actual loads are.
The 50a will give you 4,800 watts continuous per leg.
The 30a will give you 2,880 watts continuous per leg.
Once you figure out what your actual loads will be. You will be able to see which one best fits your needs and budget.
Don't forget about the future. You may want to add more loads, later. So, leave yourself some room for that.

 

[zanydroid]

Are you going to be tempted to run some small kitchen appliances? Like even just basic heating stuff up during an outage (I find it helps keep me sane). That tips the scale to 50A

 

[AZ Solar Junkie]

The 50a will always be better.
But, could be more than needed. It's hard to guess without knowing what your actual loads are.
The 50a will give you 4,800 watts continuous per leg.
The 30a will give you 2,880 watts continuous per leg.
Once you figure out what your actual loads will be. You will be able to see which one best fits your needs and budget.
Don't forget about the future. You may want to add more loads, later. So, leave yourself some room for that.

I'm just curious about how your math works out. Isn't 50 amps at 120 volts 6000 watts? I'm sure you are right and I'm just not taking everything into account... I'm new at this.

 

[zanydroid]

80% rule for continuous. I’m not sure any of the loads in question is required to be considered continuous.

 

[Mikep4485]

If you balance the 120v legs the 30A switch has a pretty decent chance to be OK. Mini split is the largest power load. Fridge and chest are under 300W each. They do have a high surge though but that doesn’t affect breaker sizing. Everything else is pretty low. LED lights are pretty irrelevant from load calculation angle.

Did you calculate the load?

I just started calculating. I bought a killawatt meter. The freezer used 1400 watts in a full day with the highest surge at 85 watts and the fridge is going to be around 4000 watts. Not sure on the mini split as I’m going to order it with the other components.

I don’t think I’m going to hook up and small appliances until I have a better system. They would be nice but the ac essential in Florida.

 

[timselectric]

I'm just curious about how your math works out. Isn't 50 amps at 120 volts 6000 watts? I'm sure you are right and I'm just not taking everything into account... I'm new at this.

80% as stated above.
Since I don't know what the actual current or future loads will be. And I generally don't load circuits over 80%. Whether the loads are considered continuous or not.

 

[zanydroid]

I just started calculating. I bought a killawatt meter. The freezer used 1400 watts in a full day with the highest surge at 85 watts and the fridge is going to be around 4000 watts. Not sure on the mini split as I’m going to order it with the other components.

I don’t think I’m going to hook up and small appliances until I have a better system. They would be nice but the ac essential in Florida.

Need to keep watt hours and watt straight.

Usually surge for freezer is given in current? Not sure. I maybe wouldn’t trust a killawatt on that, I think most people use clamp meters with surge reading (which when I bought my clamp meter as a noob, I didn’t realize to get).

And 85W surge converted to current is MUCH lower than I expect for a freezer using an AC motor. Maybe if it’s an inverter freezer that would be in line.

Minisplit power will be very smooth, they typically don’t surge in a meaningful sense for system planning

 

[zanydroid]

Since I don't know what the actual current or future loads will be. And I generally don't load circuits over 80%. Whether the loads are considered continuous or not.

Yeah, that makes sense esp in a hot climate. 100% for an hour (which isn't continuous by the book definition) can easily trip a breaker when it's derated due to high ambient temperature.

 

[Mikep4485]

Thank you both for the help! I’ll probably just do the 50 amp to help future proof the system.

 

[glandpuck]

Maybe this will help, or not:
When running wires and trying to figure out the gauge needed to supply a load over a distance, you can easily search for a voltage drop over distance calculator which will be on many websites. Then if you know the voltage range for your loads and the amps required to be supplied to the load, you can choose the wiring for your supply. Say you are installing a 120 volt circuit, 15 amps and your appliance is 120 volts 6 amps, but is 100 feet away from your inverter where the output is 120 volts on a 15 amp circuit. The appliance may actually require 112 to 130 volts (check the labels) and the distance calculator will tell you the voltage drop over the distance. Using a 12 gauge wire may result in a voltage drop of only 2 volts over the 100 foot distance and well within the appliance specs.

The other thing of concern is the number of wires and their gauges and amps flowing that can be installed to NEC code within a certain diameter conduit. 120 volts is 3 wires, 240 is 4 wires. Again, many websites for electrical conduits and wires will tell you the maximum number of wires and their gauges and amps that can be installed in a conduit. Conduits trap heat and you do not want the wires to heat up, the insulation to melt and arcing and a fire to occur.

 

[Mikep4485]

Maybe this will help, or not:
When running wires and trying to figure out the gauge needed to supply a load over a distance, you can easily search for a voltage drop over distance calculator which will be on many websites. Then if you know the voltage range for your loads and the amps required to be supplied to the load, you can choose the wiring for your supply. Say you are installing a 120 volt circuit, 15 amps and your appliance is 120 volts 6 amps, but is 100 feet away from your inverter where the output is 120 volts on a 15 amp circuit. The appliance may actually require 112 to 130 volts (check the labels) and the distance calculator will tell you the voltage drop over the distance. Using a 12 gauge wire may result in a voltage drop of only 2 volts over the 100 foot distance and well within the appliance specs.

The other thing of concern is the number of wires and their gauges and amps flowing that can be installed to NEC code within a certain diameter conduit. 120 volts is 3 wires, 240 is 4 wires. Again, many websites for electrical conduits and wires will tell you the maximum number of wires and their gauges and amps that can be installed in a conduit. Conduits trap heat and you do not want the wires to heat up, the insulation to melt and arcing and a fire to occur.

Thanks for the info. I guess where I’m getting confused is figuring out the amps needed for each appliance. I have put a watt meter on and over a 24 hour period one used 1500 watts and the other was about 2500. but I’m not sure how to figure out the amps. Everything is 120 volts. I probably just need to try to google the manuals.

 

[zanydroid]

Need to brush up on the difference between power and energy. Maybe the inverter manual will explain this but not the appliance.

Watt = power. Instantaneous draw
Watt-hour = energy

Watt meter (incorrectly named) is more of an energy meter. If it has a peak reading then maybe you can use it. Please research it on your own. I don't trust it but I could be wrong from being an elitist -- I would use clamp meter with surge or a energy meter that collects 1 minute data in a graph. Summing over 24 hours doesn't help with amps.

1000W for 1 hour = 1kWh
41.6W for 24 hours = 1kWh

First case: 1000W / 120V = ~8A
Second case: 41.6W / 120V = ~0.34A