fifth
Well-known member
I'm installing a 150amp subpanel to my new garage. The run is about 125ft, my research shows that I need two #1 copper lines for that long of a run. Does this sound correct?
150amp subpanel
- Thread starter fifth
- Start date
1/0 copper, to achieve your load, length and voltage drop.
theoldwizard1
Well-known member
Better ? No. More expensive ? HELL YES.
What size is the breaker in the main panel ? IMHO, 150A (from the main) is over kill, unless you are going to have 2 or 3 buddies bring the welders over for a welding contest !
If you are a "one man band", 60A feed from the main will likely cover everything, but you never know until you write down all of your loads, including possible future loads, and add them up. (There is no reason that the feed from the main needs to match the main breaker in your sub-panel.)
At 60A, Mobile Home Feeder 2-2-2-4 will save you a ton of money !
sberry
Banned
2 is good for 90
Copper is always the conductor of choice, but is a lot more expensive then aluminum alloy, installed correctly aluminum alloy is a safe, economical choice.
theoldwizard1
Well-known member
He is a "pro". Listen to him.
ard
Well-known member
I always install copper.
That way, in the future if I develop a crack problem, I know where to go...
That way, in the future if I develop a crack problem, I know where to go...
sberry
Banned
How is this panel going to be fed?
Fed off my main 200amp panel. I'm debating on either pulling off the main feed (always hot) or installing two 70amp breakers. I went with two runs of #4 cooper as it showed #4 rated 85amps each.
I don't think I will ever use 150amps but it was the only one I could find with 15slots, above 125amp, and had a main breaker.
Items on the panel;
-A/C
-hot tub
-air compressor
-welder
-40 T5 lights
-RV
sberry
Banned
you need a little help with this. Did you already buy the wire?
prostreetamx
Well-known member
I used a 24 circuit 150a sub in my new garage but only fed it with a 100a breaker. You can use a larger panel but the wire and main breaker must match your permit.
mike93lx
ALLIANCE MEMBER
You need a pro electrician, seriously. You are way off on how to do this and are going to end up with major code issues.
wyliesdiesels
Well-known member
Looks like my reply disappeared.
#1 is too small.
Where did you read that #1 is good for 150a?
What do you mean by always hot? Would this be from the meter lugs?
What size in HP is the compressor?
ard
Well-known member
+1000
Op is headed for a major mess.
Dude, stop now. You are making some needless mistakes.
Pro help would be good, but even floating your plans here will help.
The idea that you can add wires and breakers like preschool math problems is...scary.
Put a breaker in the panel, connect to the breaker, the same way every circuit in your house is fed. Wire and breaker sized correctly according to load.
ard
Well-known member
1. Determine how much power you NEED in the new location. aka load calc. You can also spitball, then add a bit for future. This isn't an exact science.
But 150A is a LOT. It becomes especially problematic if you really are pulling 150 off a 200A main, if you really are using 150 plus what the 200 needs, it will be an issue.
You could probably do nicely w 90Amps.
2. Based on the load above, figure out the wire lenght. UNDERSTAND that it is generally ONE conductor per leg. Two lines, one neutral, one ground. Do a voltage drop calc to see what size wire you need.
I won't guess here, if you need help you will get 10 responses on wire size. There are online calculators
3. Based on the wire size, and how you are running from panel, under ground and into the new structure, plan out the conduit or cable. Personally I run everyting underground in conduit. The number of conductors, lenght, bends dictates the conduit size. 2 inch feels good.
4. Breaker in the 200A box determines the average. If the cable you selected above is good for 90A, then a 90A breaker in the main box protects this cable. It is NOT the main breaker inthe subpanel that dictates the amps of the circuit.
5. Install. Turn on.
teamextreme
Well-known member
I'm surprised nobody has commented on this one yet. You can't parallel conductors smaller than 1/0, so your plan of 2 runs of #4 won't be code compliant, and connecting them to 2 different breakers is certainly not. There are absolutely TONS of threads on people installing sub panels just like you, with lots of good advice given. There's even an FAQ sticky with info from Wylies on feeding separate structures. Do some more research before you waste any more money on parts.
It basically boils down to this:
You don't need to match the rating of subpanel with your feeder breaker/cable. You can feed your 150A sub with any size breaker and properly sized wire you want.
You most likely don't need anywhere near 150A
Most people go with #2 MHF in 2" conduit and a 90A breaker. Simple, cost effective and works.
You haven't stated if this is an attached or detached structure, that will also effect how this is wired, and particularly grounded. (you're slipping on asking that question Wylies
)ticklechicken
Well-known member
I had a similar situation with my shop that I'm building now. I installed a 150 amp panel with its own meter from the pole 100 feet away. Most of the charts say that I could use 2/0 aluminum, but that ultimately wasn't correct. Since it was a detached garage, the code assumes a higher duty cycle and forced me to use 3/0 aluminum.
In this project, I've discovered a lot of details like this that you'll get wrong if you don't dig in.
In this project, I've discovered a lot of details like this that you'll get wrong if you don't dig in.
No, for dwellings it's allowed to UNDERSIZE conductors, there used to be a table listing the allowed conductor sizes but was removed, now calculations are required.
So an item like this is what is recommend to pull power off the main panel?
https://www.amazon.com/dp/B002KGFTXU/?tag=atomicindus08-20
https://www.amazon.com/dp/B002KGFTXU/?tag=atomicindus08-20
sberry
Banned
Yes but needs a couple sizes smaller for the wire you have.
ard
Well-known member
You are up to Step 5 in my list???
What size service are you planning? Did you estimate or just like the idea of *** Amps?
What size conductors? Conduit?
sberry
Banned
A hot tub is about as greedy as most people get, if you want automatic air conditioning and air compression in a short overlapping circumstance could see 70A.
wyliesdiesels
Well-known member
I'm surprised nobody has commented on this one yet. You can't parallel conductors smaller than 1/0, so your plan of 2 runs of #4 won't be code compliant, and connecting them to 2 different breakers is certainly not. There are absolutely TONS of threads on people installing sub panels just like you, with lots of good advice given. There's even an FAQ sticky with info from Wylies on feeding separate structures. Do some more research before you waste any more money on parts.
It basically boils down to this:
You don't need to match the rating of subpanel with your feeder breaker/cable. You can feed your 150A sub with any size breaker and properly sized wire you want.
You most likely don't need anywhere near 150A
Most people go with #2 MHF in 2" conduit and a 90A breaker. Simple, cost effective and works.
You haven't stated if this is an attached or detached structure, that will also effect how this is wired, and particularly grounded. (you're slipping on asking that question Wylies
I assumed by 2 runs he meant 2 #4s for the hots not parallel conductors but i shouldve asked. And many people think that 2 single poles are the same as a double pole.
I was tired when i read his OP and kinda of glazed over some of the obvious novice thinking. Good catch on your part.
As far as me slipping on the attached detached, I thought i was safe to assume that this is a detached structure since its 125'. Or maybe the OP has an attached structure that is 125' long :dunno
Nevertheless, the only difference between attached and detached is grounding electrodes and the allowed wire and cable types...neutral is isolated in either case... and i didnt want to bring up rods til we get the basics settled first which seems like is still an issue...
Most charts? Theres only one valid chart and thats 310.15(B)(16) which BTW says 135a for 2/0 al.
yes that is a double pole circuit breaker and thats what you will need IF there is room in your main service panel.
But you cant use just any breaker. It needs to match the brand and model listed for your panel.
What brand of panel do you have?
Can you post pics of your main service panel so we can see what you have.
And you have jumped ahead quite a few steps.
First we need to know what your loads will be.
Most people over exaggerate their loads and electrical needs...
So what about the following:
One man shop, two man shop, business with several employees or a neighborhood welding party shop?
AC, electric heat, large welders, water heater etc?
WAIT!
Figure your loads first before you buy wire.
I bet you could get by with 90a or less....
ard
Well-known member
After we yanked him somewhat firmly, I was encouraged when he came back and asked. "OK, lets start from the beginning"
And gave him what I thought was a decent plan for him to explore with us what is needed to get to a 'purchase parts, install them". Basically 5 steps.
Instead he is asking about specific 125A breakers and buying very expensive wire.
Whatever.... Horse>>>>Water>>>Dead Horse.
PS I did catch his '85A for#4 so that and two 75A breakers gives you 150A service'...my comment was "The idea that you can add wires and breakers like preschool math problems is...scary."
Not really asking about a specific part, just figuring out what is commonly used. I'll grab a few pictures of my main panel in the morning.
The panel is for a one man garage/shop @ 1,300sf. Its attached by a common wall (breezeway). I can run power through the wall and not have to trench anything. The run closer to 100ft.
Power needs:
-40 to 50 T5 lights
-Smaller 220v air compressor (not purchased yet)
-AC/Heat pump
-220v tig
-Hot tub
-Lift
-beer fridge
-stereo
-misc chargers
wyliesdiesels
Well-known member
OK so its attached then.
No rods needed.
We do need to know what brand and model main panel you have.
With those loads Id say 90a is sufficient.
No rods needed.
We do need to know what brand and model main panel you have.
With those loads Id say 90a is sufficient.
ard
Well-known member
Just guessing from these numbers you have: 43A @ 120, figure another 27 with misc'... So 70A @ 120 or 35A at 240.
Then you have 55A at 240.
Add them up, 90A at 240 (I **swear** this is a coincidence.)
This is a rudimentary calc- there is no allowances for continuous load versus stop/start. Also, I just guessed at some of your loads as you didn't provide.
Your wild card is the hot tub plus the HVAC. These are not usual loads on an attached garage. My hot tub is on a 50A240V breaker. One of my HVAC units is on a 40A240V breaker- how ever as I recall this might only draw 20-24 A when running?
Let's see what others say
wyliesdiesels
Well-known member
Go read the nameplate.
What size in tonnage is it?
Prob 3 ton and pulls 10-15a FLA.
Ive got a brand new goodman 3 ton unit and it pulls 9a
running even though nameplate says 14a (i measured with my 381)...my last place had an older 3 ton unit and it pulled closer to 20a. They get more efficient every year...ard
Well-known member
Yeah, totally agree- my point was that you cannot rely on the breaker to guesstimate the running amps. It's a 4 ton unit, from 1994. So yeah, it might not be even 20.
In terms of the load calcs for OP- thoughts? 90 OK? 125 safer? If it is a 120V plug in hot tub, that's one thing- but a 7500W heating element would be something else.
In terms of the load calcs for OP- thoughts? 90 OK? 125 safer? If it is a 120V plug in hot tub, that's one thing- but a 7500W heating element would be something else.
You need 4 wires for a sub panel, 2 hot, one neutral and one ground.
teamextreme
Well-known member
No, 4 wires, like brewchief says. Read the text above the diagram you referenced. It states that 3 wire feeds were allowed up to 2008. Since then, 4 wire has been required.
wyliesdiesels
Well-known member
NO, as has been said above you need 4 wires.
You may be confusing grounding electrodes with equipment grounding conductors.
The EGC for your feeder can be #8 cu or #6 al up to 100a breaker and #6 cu or #4 al up to 200a breaker....
See post #4 in the FAQ sticky for more details...
PS: Just in case it was not clear, I went back and added some bolding and wording on that FAQ to make it as clear as possible!
BTW: Even if i was under pre-2008 code, I would still do 4-wire as its safer and seeing as how many are running communication cabling, water, gas, etc to their detached structures, with a 4-wire you are all set...
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