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Sub-Panel, wire gauge, and breakers

 
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scottbryant99




Joined: 15 Jun 2017
Posts: 4



PostLink    Posted: Thu Jul 27, 2017 3:57 pm    Post subject: Sub-Panel, wire gauge, and breakers Reply with quote


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I am wanting to put a sub panel in my basement off of the panel panel that would be above it in the garage. I am an industrial maintenance technician/electrician so this is something I am comfortable doing myself.

The sub-panel would power a 30A PID panel with a march pump`, a vortex blower for condensation extraction, and possibly additional lighting in the future probably LED.

What size breaker would you put in the main panel? I bought 8 gauge 10-3 wire to go from the main panel to the sub-panel. Should I have bought 10ga? I can take it back still.

Can a 30A GFCI breaker handle a 30A PID panel without popping the breaker? I would think that you would need to get it 10% of extra amps. Can I use the 8 gauge 10-3 wire to wire the subpanel to the 30A PID panel?
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GAParkins




Joined: 07 Jan 2016
Posts: 29
Location: South Florida


PostLink    Posted: Thu Jul 27, 2017 4:58 pm    Post subject: Reply with quote

The pump is a couple of amps and the LED's are negligible. What is the nameplate FLA figure for the blower? That's an inductive, not a resistive load. I am in the same situation, looking to add a 50A PID panel. Because of other planned loads, I think I'm going to go for at least a 60A feed, if not more.

In your case, you are cutting it pretty fine with a 30A feed, but the #8AWG should be fine if you limit the feed to the subpanel with a 40A breaker.

All bets are off if the distance gets to 100'+. If that is the case in your situation, you should consult the NEC and your local codes. Find a voltage drop table for low-voltage AC power, and see what is recommended for your distance.
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itsnotrequired




Joined: 15 Sep 2015
Posts: 177
Location: central wi


PostLink    Posted: Fri Jul 28, 2017 2:38 am    Post subject: Reply with quote

if putting in a sub panel, might as well go bigger than you think you will need, you never know what you may want to add in the future.

to your specific situation, what is the actual load of this 30 amp panel? assuming it is like a kal setup with a 5500 watt heating element, a couple pumps and some indicating lights, you might be able to get by with a 30 amp feeder to the sub and still pick up the fan and some lighting but man, it would be close and maxed out. i would run 40 amp at a minimum. i assume this would be a 240 volt feeder with a neutral and ground.

it is unclear what you mean by '8 guage 10/3' wire. is this #8 awg conductors? or #10 awg conductors? if #10, you will be limited to a 30 amp breaker upstream. #8 lets you use a 40 amp upstream breaker. these would be two-pole breakers, with two hots, a neutral and a ground to the sub-panel. this also assumes you have nm cable (commonly referred to as romex).

the 'xx/3' notation is typically used with nm cable where the 'xx' represents the conductor gauge size and the '3' means there are two hots, a neutral and a ground, what you would use for a 240 volt feeder. so 8/3 is #8 awg conductors and 10/3 is #10 awg. 'xx/2' would be the notation for a nm cable that has a hot , neutral and ground. this would be for 120 volt circuits, like to a receptacle in the wall.

so long story short, you might be able to get by with #10 and a 30 amp feeder but i really wouldn't recommend anything less than #8 with a 40 amp breaker. but go bigger if you can. when i went to finish my basement, i had to put in a sub next to the main panel since i only had two spaces available in the main panel. it is only a few feet away from the main so i figured what the hell and put in a 100 amp sub. massive overkill for some lights and receptacles in the basement but fast forward five years and i have since added an outdoor electric sauna (60 amp feeder) and an electric brew setup (30 amp feeder)...sure glad i went with the 100 amp sub!
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GAParkins




Joined: 07 Jan 2016
Posts: 29
Location: South Florida


PostLink    Posted: Fri Jul 28, 2017 12:06 pm    Post subject: Reply with quote

itsnotrequired wrote:
when i went to finish my basement, i had to put in a sub next to the main panel since i only had two spaces available in the main panel. it is only a few feet away from the main so i figured what the hell and put in a 100 amp sub. massive overkill for some lights and receptacles in the basement but fast forward five years and i have since added an outdoor electric sauna (60 amp feeder) and an electric brew setup (30 amp feeder)...sure glad i went with the 100 amp sub!



^^^ This, x 1000 ^^^
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kal
Forum Administrator



Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Fri Jul 28, 2017 12:48 pm    Post subject: Reply with quote

+1 to that as well. Unless the run is extremely long, put in a larger subpanel, at least 60A. But then the price of a 100A is negligibly more so you might as well do that. The only big cost savings will be on the wire used for the run and only if it's far.

I would probably put in a 100A panel with a 30A GFI breaker for the control panel and then a couple of separate 15A circuits for other things.

The VTX600 vortex fan I use and recommend consumes only 100 watts so it's not huge:



I wired an outlet for it in the ceiling that's in series with some other 'regular' 15A outlets.

See: http://www.theelectricbrewery.com/Vortex-VTX600-6-Powerfan-452-CFM

scottbryant99 wrote:
What size breaker would you put in the main panel?

The main panel breaker that feeds the subpanel should match the size of the main breaker in the sub-panel. The main panel breaker is there to protect the wiring from the main panel to the sub-panel. So if you put in a 100A sub-panel, you'd have two 100A breakers: One in the main panel feeding the sub, and one in the sub feeding the smaller 30A and 15A breakers. (EDIT: Or put in a smaller main cutoff breaker in the sub-panel).

scottbryant99 wrote:
I bought 8 gauge 10-3 wire to go from the main panel to the sub-panel. Should I have bought 10ga? I can take it back still.

The wire size should be whatever amperage you want for the sub-panel - the breakers on either end need to be matched accordingly. (EDIT: Or put in a smaller main cutoff breaker in the sub-panel).

P.S. Make sure to not bond neutral and ground in the sub-panel. Only do this in the main panel. This is often done incorrectly as even electricians are used to bonding the two in panels.

scottbryant99 wrote:
Can a 30A GFCI breaker handle a 30A PID panel without popping the breaker?

A 30A breaker should indeed be used with a 30A panel. See the instructions here:

http://www.theelectricbrewery.com/control-panel-part-2?page=3

Current draw with 2 pumps and a 5500W element running is just under 24A, so just under 80% load. The 80% load rule is built into the design with the 30A panel.

Good luck!

Kal

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Last edited by kal on Fri Jul 28, 2017 1:49 pm; edited 3 times in total
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GAParkins




Joined: 07 Jan 2016
Posts: 29
Location: South Florida


PostLink    Posted: Fri Jul 28, 2017 1:14 pm    Post subject: Reply with quote

kal wrote:
The main panel breaker that feeds the subpanel should match the size of the main breaker in the sub-panel. The main panel breaker is there to protect the wiring from the main panel to the sub-panel. So if you put in a 100A sub-panel, you'd have two 100A breakers: One in the main panel feeding the sub, and one in the sub feeding the smaller 30A and 15A breakers.


I'm pretty sure that you wouldn't need the 100A breaker in the subpanel. You might even wind up with trip coordination issues. The #2AWG feeding the subpanel is protected at the main panel. The only thing the subpanel breaker would do is to serve as a local disconnect. There are subpanels available from Square D and others that don't have a main breaker. Look for the words "Main lug" instead of "Main breaker."
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kal
Forum Administrator



Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Fri Jul 28, 2017 1:36 pm    Post subject: Reply with quote

True - good point. I should have said that the downstream breaker is the same size or smaller. (It should never be bigger). I updated my post. Or go with a sub-panel without a main cutoff breaker.

You could go smaller in the sub-panel, but if it's a pretty simple setup like this sounds like it is (only 2 levels of panels?) and you did do two 100A breakers one of the two will always trip first and it would be obvious where the issue is (easy to pinpoint) and the results would be the same: Loss of power to the sub-panel. My house has exactly this setup we're talking about: After we moved in we had a new main 200A panel installed opposite the meter with multiple breakers including a 30A for the brewery control panel, 60A for the hottub, 40A for the sauna, 20A for a sunroom heater, and a few other 15A breakers. This panel also has a 100A breaker that feeds to the original 100A house panel that powers the rest of the house (40A stove, 30A A/C, a bunch of 15A circuits for the various rooms in the house, etc). That original panel has a 100A main breaker on it so we now have a 100A breaker in a 200A panel feeding into a 100A sub-panel with a 100A main breaker. Had we designed it the "right way" from the start we would have had one large 200A panel with no sub, or maybe a 200A main panel and a sub-panel without a main breaker like GAParkins mentions. It really would depend on the setup and distances. In our case we do have 2 full panels because the 100A was already in place when we moved in, but it actually works out well for us because that panel is actually very far from the high current devices powered by the new 200A panel (the two panels are far apart) so we probably saved in the end as thick gauge wiring is expensive.

If you had 4-5 levels of panels and breaker sizing wasn't done correctly then it could be hard to pinpoint if breaker coordination wasn't done properly. You see this sometimes in industrial settings where poor breaker coordination results in unnecessary power loss and difficulties in pinpointing issues. Example:



A note to the OP (scottbryant99): GAParkins has some good points here and it goes to show that things aren't always as simple as they seem. If there are any doubts, best to hire an electrician who can confirm things for you. I only mention this because you mentioned that you are comfortable doing this work yourself because of your past experience, but your level of questions concern me a bit as they are somewhat basic questions that an electrician should be familiar with (i.e. wire size to use, loading rules, etc). Please don't take this the wrong way - I simply want to make sure that work is done safely and to code to keep you, your family, and the contents of your house safe. Normally when someone asks the types of questions you're asking I recommend that they hire an electrician to do the work for them because we don't know what we don't know. There may be other things that are overlooked that you're forgetting to ask about that someone with experience in this would not. No matter which way you proceed I would recommend that you pull the required permits (if applicable) and have the work inspected to get a second set of eyes on it. Good luck and brew safe!

Cheers,

Kal

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Last edited by kal on Fri Jul 28, 2017 1:50 pm; edited 2 times in total
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GAParkins




Joined: 07 Jan 2016
Posts: 29
Location: South Florida


PostLink    Posted: Fri Jul 28, 2017 1:49 pm    Post subject: Reply with quote

kal wrote:
Normally when someone asks the types of questions you're asking I recommend that they hire an electrician to do the work for them because we don't know what we don't know.


As usual, you're spot-on, Kal. I work for a firm that designs, builds, and installs power distribution systems on large yachts. Some of these boats have as many as five or six sources of power, and main busses with 480VAC @ 600A. The various classification societies governing the safe installation of these systems (ABS, Lloyd's, DNV, etc) all require trip curve coordination studies prior to approving our designs. It prevents a downstream breaker with a slower trip curve forcing a trip from an upstream breaker with the same amperage rating and a faster trip curve. It can get pretty complicated, and I've seen the inability to coordinate the trip curves properly send our engineers back to the drawing boards for another hundred hours.

The point about unintended consequences is addressed by your recommendation the OP find himself an electrician and pull the proper permits.
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scottbryant99




Joined: 15 Jun 2017
Posts: 4



PostLink    Posted: Fri Jul 28, 2017 2:22 pm    Post subject: Reply with quote

Thanks all for the replies. The wire is 8/3 that I bought. So I plan to go with 40a feed in the main panel which is less than 10 feet from the sub-panel. I'll go with 30a GFCI in the sub-panel and another breaker for the fan.
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kal
Forum Administrator



Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Fri Jul 28, 2017 2:35 pm    Post subject: Reply with quote

GAParkins wrote:
I work for a firm that designs, builds, and installs power distribution systems on large yachts.

Very cool! Not to get too far off topic here but I had some exposure to luxury yacht designers/builders through my other home theater website where I sold hundreds of video converters over the years (it was considerably easier and much cheaper to install black box converters for each TV than re-pulling wiring through bulkhead). The designers always had lots of technical questions - very thorough. Largest ship I sold to was the world's largest privately owned residential yacht: MS The World (43,524 GT, 196.35 meters). You want to get even more regulatory around safety? Try aircraft! (I also sold to luxury aircraft designers).

Back on topic: When I had our electrical work done in the brewery and for sub-panel work, I hired an electrician, pulled permits, had it all inspected. I was comfortable doing the work myself but wanted to err on the side of caution. Good luck!

Kal

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itsnotrequired




Joined: 15 Sep 2015
Posts: 177
Location: central wi


PostLink    Posted: Fri Jul 28, 2017 2:39 pm    Post subject: Reply with quote

scottbryant99 wrote:
Thanks all for the replies. The wire is 8/3 that I bought. So I plan to go with 40a feed in the main panel which is less than 10 feet from the sub-panel. I'll go with 30a GFCI in the sub-panel and another breaker for the fan.


fair enough, just recognize you will have very little spare capacity for expansion.

and you do not need a main breaker in the sub-panel, at least in the us. one less thing to buy, saves space, etc. i have two subpanels in my system and neither have a main breaker at the sub.
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GAParkins




Joined: 07 Jan 2016
Posts: 29
Location: South Florida


PostLink    Posted: Fri Jul 28, 2017 2:43 pm    Post subject: Reply with quote

itsnotrequired wrote:
scottbryant99 wrote:
Thanks all for the replies. The wire is 8/3 that I bought. So I plan to go with 40a feed in the main panel which is less than 10 feet from the sub-panel. I'll go with 30a GFCI in the sub-panel and another breaker for the fan.


fair enough, just recognize you will have very little spare capacity for expansion.

and you do not need a main breaker in the sub-panel, at least in the us. one less thing to buy, saves space, etc. i have two subpanels in my system and neither have a main breaker at the sub.


Another note...Do not under any circumstances tie the neutral and ground together in the subpanel. Buy an extras bus for the neutrals. The only place that neutral and ground should be tied together is at the main panel where your service entrance cables first appear in the house.
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kal
Forum Administrator



Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Fri Jul 28, 2017 2:49 pm    Post subject: Reply with quote

GAParkins wrote:
Buy an extras bus for the neutrals.

Most panels I've seen have separate NEUTRAL and GROUND buses, with a strap between. So you simply need to remove that strap on the sub-panel (and leave it in place in the main/highest panel).

This is something even the electrician I hired got wrong when we installed a new main 200A panel and our existing 100A panel became a sub. The inspection agency here in Ontario (ESA) even missed it. I had to remove it myself after. I did end up calling them both on it, especially the ESA (what's the point of paying for a permit which includes inspection if they don't properly inspect?).

Kal

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Kazumichan




Joined: 07 May 2014
Posts: 177
Location: Cincinnati Ohio area

Working on: Belgium golden, Dubbel, and imperial red


PostLink    Posted: Fri Jul 28, 2017 8:44 pm    Post subject: Reply with quote

Quote:
Another note...Do not under any circumstances tie the neutral and ground together in the subpanel. Buy an extras bus for the neutrals. The only place that neutral and ground should be tied together is at the main panel where your service entrance cables first appear in the house.


Recently I found out here in my neck of the woods, that you are not to bond the neutral and grounds in the main panel either, they are to be bonded together only at the meter box.
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kal
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Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Fri Jul 28, 2017 10:08 pm    Post subject: Reply with quote

Yup - it can vary by region. Which is why it's always best to have this sort of work done by a certified electrician and not rely on what some unknown person on the internet said.

Kal

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GAParkins




Joined: 07 Jan 2016
Posts: 29
Location: South Florida


PostLink    Posted: Sat Jul 29, 2017 12:24 am    Post subject: Reply with quote

We fuss and bother about every detail about our brewing from recipe to bottle, yet there are lots and lots of clothes dryers sold every day with a little jumper that ties neutral and ground together. So many people have no clue about it, and are perfectly happy that they don't.
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scottbryant99




Joined: 15 Jun 2017
Posts: 4



PostLink    Posted: Sun Jul 30, 2017 12:07 pm    Post subject: Reply with quote

GAParkins wrote:
itsnotrequired wrote:
scottbryant99 wrote:
Thanks all for the replies. The wire is 8/3 that I bought. So I plan to go with 40a feed in the main panel which is less than 10 feet from the sub-panel. I'll go with 30a GFCI in the sub-panel and another breaker for the fan.


fair enough, just recognize you will have very little spare capacity for expansion.

and you do not need a main breaker in the sub-panel, at least in the us. one less thing to buy, saves space, etc. i have two subpanels in my system and neither have a main breaker at the sub.


Another note...Do not under any circumstances tie the neutral and ground together in the subpanel. Buy an extras bus for the neutrals. The only place that neutral and ground should be tied together is at the main panel where your service entrance cables first appear in the house.


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