I am adding an additional outlet for my AC circuit and it will be a standalone (GFCI 20A). I plan on running our 40W icebox fridge, battery charger, and microwave. Should I be looking to get 10 gauge instead of 12 gauge due to the high amps? Let me know what you all think. Thanks.
AC Wiring Question
- Thread starter tym2
- Start date
Depends on the round trip distance and minimum acceptable voltage drop. I can recommend the Circuit Wizard at https://bluesea.com.
The outlet will be in the port cockpit locker and connect to the starboard panel at the nav station. I'm estimating this to be 12' of wiring (not a straight shot) so 24' round trip?
The microwave that is currently installed is a 9A 120V.
The microwave that is currently installed is a 9A 120V.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 21,573
For your AC circuit you need too look at the total AMPS you plan to use and plan your wiring accordingly.
Look not only at the running AMPS but the start load. A refrigerator starting and stopping will put a heavier load on the circuit than the when it is running or resting.
Loading up a single circuit with a series of heavy AMP use loads will mean the breaker will be opening a lot when all of the appliances are in use at the same time.
"Hey honey I am going to use the hair dryer... That's ok, I'll pop the coffee in the microwave... just then the temp in the refrig is rising and the machine's brain says START THE COMPRESSOR!... Pop... goes the breaker.
DAMN! there it goes again.... Maybe I need a bigger breaker...."
NOooooo!
Look not only at the running AMPS but the start load. A refrigerator starting and stopping will put a heavier load on the circuit than the when it is running or resting.
Loading up a single circuit with a series of heavy AMP use loads will mean the breaker will be opening a lot when all of the appliances are in use at the same time.
"Hey honey I am going to use the hair dryer... That's ok, I'll pop the coffee in the microwave... just then the temp in the refrig is rising and the machine's brain says START THE COMPRESSOR!... Pop... goes the breaker.
DAMN! there it goes again.... Maybe I need a bigger breaker...."
NOooooo!
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 21,573
Ralph. He has not specified that info. He did say he was putting in an AC circuit
"I am adding an additional outlet for my AC circuit and it will be a standalone (GFCI 20A). I plan on running our 40W icebox fridge, battery charger, and microwave."
The fridge specs:
AC: 0.45A 117V
DC: 4.5A 12V
I’m assuming this is not the start up strain however
So the fridge will add some load although quite small. I don't think the inrush is a problem as it is only momentary.
You are right in identifying every possible load before putting your money down for the wire.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 21,573
Good guess but without data to support the choice it is just a guess. You may be way over the wire size or under it.
That is the reason electricians will actually examine the data and arrive at a size that serves the purpose.
There are many websites with calculators. You could look at several and using your data get a best solution.
This web site says 14AWG based on what I input into the calcualtion.
I changed the data points and the calculator says you need 8AWG.
Please help your self and learn the details before you jump forward. You did a good thing to ask the question. I encourage you examine the actual amps you hope to consume and make the calculations for your boat and project.
That is the reason electricians will actually examine the data and arrive at a size that serves the purpose.
There are many websites with calculators. You could look at several and using your data get a best solution.
This web site says 14AWG based on what I input into the calcualtion.
I changed the data points and the calculator says you need 8AWG.
Please help your self and learn the details before you jump forward. You did a good thing to ask the question. I encourage you examine the actual amps you hope to consume and make the calculations for your boat and project.
Huboy. Everything was going so well, and then it wasn't 
.
Follow @jssailem 's recommendations. Add up all your A's and show your work. GIve us the single and return lengths. Ignore inrushes. Show all your work for wire sizing and we'll check your calcs.
You know what you're doing, you just fell off the rails momentarily.
.Follow @jssailem 's recommendations. Add up all your A's and show your work. GIve us the single and return lengths. Ignore inrushes. Show all your work for wire sizing and we'll check your calcs.
You know what you're doing, you just fell off the rails momentarily.
My shore power is 120V/30A. My AC breaker says its 30A and says it trips at 37.5A. Distance from outlet to panel is ~12ft. The outlet is a 20A GFCI. I plan on plugging in:
- Microwave: 1080W 120V 9A
- Ice box refrigerator unit: 52.65W 117V 0.45A
- ProSport HD 20A 2 Bank charger : 780W 120V 6.5A
9A+0.45A+6.5A = 15.95A
How's the math?
- Microwave: 1080W 120V 9A
- Ice box refrigerator unit: 52.65W 117V 0.45A
- ProSport HD 20A 2 Bank charger : 780W 120V 6.5A
9A+0.45A+6.5A = 15.95A
How's the math?
12 Ga is all the outlet can support. 20 amps. On a boat you will need tinned wire to help control corrosion. not a home depot thing. My question is where do you plain on grounding the GFI will not work without. Use your shore power ground.I was an IBEW marine electrician.
Your math is right on. No problem with excessive drop due to wire length.
Your 20A GFCI will limit your current supply to your wiring to 20A. Your estimated load is 16A. Personally, I would want a slightly higher breaker suited to your wiring to allow for an inconveniant inrush and maybe a bit of future additional load.
According to the National Elelctrical Code:
#14 marine wire with 90 deg. C insul. is rated for 25A and this should be protected with a max. sized 25A breaker.
Your 20A GFCI will limit your current supply to your wiring to 20A. Your estimated load is 16A. Personally, I would want a slightly higher breaker suited to your wiring to allow for an inconveniant inrush and maybe a bit of future additional load.
According to the National Elelctrical Code:
#14 marine wire with 90 deg. C insul. is rated for 25A and this should be protected with a max. sized 25A breaker.
Check the wire from your shore power plug to the main breaker. On my 1988 C30, they used 12-3 cable for the 30A plug and that is too smalls. For 120v AC load the following is standard
15A - 14GA
20A - 12GA
30A - 10GA
I replaced wire from the plug to the panel with 10-3 Ancor tinned cable.
15A - 14GA
20A - 12GA
30A - 10GA
I replaced wire from the plug to the panel with 10-3 Ancor tinned cable.
Yep, I did what @Hayden Watson did, upgraded the boats incoming 120vAC cable to 10GA.
And to repeat what Hayden and @Shadowwalker said, use Marine Grade Stranded & Tinned AC wire.
Also, use ring terminals or locking fork terminals for the connections to the panel and outlet.
Welcome to the forum Shadowwalker!
And to repeat what Hayden and @Shadowwalker said, use Marine Grade Stranded & Tinned AC wire.
Also, use ring terminals or locking fork terminals for the connections to the panel and outlet.
Welcome to the forum Shadowwalker!