new subpanel in garage


  #1  
Old 06-22-04, 04:28 PM
pete curtis
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new subpanel in garage

I moved into a house with an attached garage served by a single 20A circuit which has way too much on it: refrigerator, chest freezer, washer, gas dryer, attic fan, 3 light fixtures, and the occasional power tool (table saw, drill press, various small hand tools). We've been here 4 years and have never tripped a breaker, but i think we're past due for an upgrade.

The main service is 125-amps and the total house load is currently less than 50 amps. I plan on adding a subpanel and several new 20A circuits:
1- gas dryer, roof fan, 2 outside receptacles
2- freezer and occasional hand tools
3- table saw, drill press and various small bench tools
4- washer only
5- lights

I'd like to keep the cost down if I can, but I'm not interested in skimping too much on the capacity as someone might want to run heavier loads in the future. I'm thinking i should probably set the panel up for 240 volts even though i currently have only 120V needs. The wire distance from main panel to subpanel is 50 feet (under the house). So...

What size subpanel?

What size wire for the feed from main to sub? I'd rather run a single cable if possible (like 2/3 w.grd or 4/3 w/grd). If i have to run separate wires, what's the best way to handle that?

How do I connect the wires at the main and the subpanel?

Do the circuits I've listed above seem adequate and fairly well-balanced?

One of the outside receptacles will be in a gazebo at the end of a 15' trench (40' from subpanel). will 12-2 UF be adequate? How deep must it be buried?

many thanks,
pete
 
  #2  
Old 06-22-04, 06:32 PM
J
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I suggest you get a 12-space subpanel. Then you can split that circuit #1 into three circuits for only about ten bucks more. It's worth ten bucks to not have to worry about whether the dryer and roof fan are on when you go to plug in the ice cream maker or Christmas lights into the outside receptacle.

Most certainly you want to set the panel up for 240, even if you are 100% sure that you will never have anything at 240 volts. The reason is voltage drop. I'd run 6/3 UF-B under the house off a 60-amp breaker. That should be plenty for all your needs (unless you plan kilns or a large welder).

At the main, you just connect them to the breaker the same way an electric dryer would be connected. At your sub, you just connect the black and red to the two main lugs, the neutral to the neutral bar, and the ground to the grounding bar (which you may need to purchase separately).

12/2 UF-B will be adequate for your gazebo. If you direct bury it, and protect it with GFCI before it goes underground, you need only bury it 12 inches.
 
  #3  
Old 06-22-04, 06:49 PM
W
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One additional suggestion. Since this is an attached garage, you can use a 'lugs only' subpanel, which doesn't have a main breaker in it. However bulk pricing being what it is, you may find that it is _cheaper_ to buy a 100A panel with the 100A main breaker than it is to get a 60A lugs only subpanel. It is entirely reasonable to use this with the 6/3 wire that John suggests, as long as the supply breaker is 60A.

Also, IMHO the washer and dryer can share the same 20A circuit. The fridge and freezer can also be together on one 20A circuit. These circuit for the washer and dryer need not be GFCI protected. The circuit for the fridge and freezer should not be GFCI protected. (Code would _permit_ GFCI protection for the fridge and freezer, but this is a bad idea )

All of the receptacles for your hand tools _must_ be GFCI protected.

The general rul is that all receptacles in a garage need to be GFCI protected, but the exception is for receptacles dedicated to an appliance that is not moved from one place to the other. Thus the washer, dryer, fridge and freezer are not required to be GFCI protected.

It is debatable if the receptacle for the drill press or the table saw needs to be GFCI protected. I personally would dedicate a receptacle and circuit for the table saw, and _not_ GFCI protect it. The reason is that GFCIs are known to 'nusiance trip' when large motors are started. The drill press has a much smaller motor, and IMHO can be plugged in with the other hand tools.

-Jon
 
  #4  
Old 06-22-04, 07:17 PM
R
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One word of caution, and I am likely to get slammed for this.

Code does say that receptacles dedicated for a refrigerator and freezer do not need GFCI protection, while others in a garage (or unfinished basement) do.

However, some inspectors interpret the code to mean that only the receptacle that the refrigerator or freezer is plugged into can be non-GFCI. They require a non-duplex receptacle. The thought process is that if you use a duplex, the other half of the duplex might be used for something else.

I see the logic in this thought if the receptacle is out in the open (next to the refrigerator), but I fail to see the logic in this if the refrigerator is effectively blocking the receptacle from other use.

In your case, if the two items (refrigerator and freezer) are on the same circuit and right next to each other, then you don't face that issue, as both halves of one duplex receptacle can be used.

If you do run into this problem, it's easier to comply rather than argue. However, single eceptacles are more expensive than duplex receptacles, and if the single receptacle is the only eceptacle on a 20 amp circuit, it must be a single 20 amp reeptacle.
 
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Old 06-22-04, 07:25 PM
J
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I don't think "a single receptacle or a duplex receptacle for two appliances" has any ambiguity.
 
  #6  
Old 06-23-04, 09:31 AM
pete curtis
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Thanks everyone. I was surprised (and pleased) to hear that 6/3 wire would be adequate for this. I had specified #2 on my permit application and then had second thoughts about it when I was unable to find 2/3 "Romex" type copper cable (am I right to be avoiding aluminum?). I'd rather not wrestle with 3 separate #2 wires plus the ground wire, since the crawl space under the house is very tight.

Originally Posted by John Nelson
At the main, you just connect them to the breaker the same way an electric dryer would be connected. At your sub, you just connect the black and red to the two main lugs, the neutral to the neutral bar, and the ground to the grounding bar (which you may need to purchase separately).
Could you elaborate please? Does this mean black to one hot bus, red to the other and white to neutral; and the same at the subpanel? Re: grounding bar, what exactly is that? I thought it was a separate bar (not the neutral bar) that sits in the main and subpanel. Are subpanels sold that don't include a grounding bar? The inspector made a point that I should not ground the subpanel separately, but should run a ground wire from the subpanel back to the main panel ground.

Re: GFI, the inspector also made a point that all circuits in the garage must be GFI protected, which i plan to do by making the first box in each run a GFI.

Re: Washer and dryer on same circuit. That makes sense to me, but I thought NEC required the washer be on its own.

Again, thanks for your help.

pete
 
  #7  
Old 06-23-04, 09:49 AM
W
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6/3 copper is rated for 55A at 60C. It may be protected by a 60A breaker if the calculated loads are less than 55A. I have not done a detailed load calculation, nor do I believe that John has...but for the loads that you've described, I am confident that 55A is more than enough.

You should not use 'Romex' for this application, but should instead use 'UF-B' cable. This is similar to Romex, but has a sturdier sheath and an insulated ground. It might be that Romex would be acceptable, but since you describe going under your building (a potentially wet location), the UF-B cable is just a good idea. You may also be able to get copper type SE-R cable. If you have a number of choices, post a couple of them; we will tell you which are acceptable, and you can just pick the cheapest one.

Aluminium may be used; you need to use larger conductors, and be more careful with the terminations, and use anti-oxidant coating on all the terminations. I would prefer to use Copper.

A proper _subpanel_ should have a separate ground and neutral bar, as you say. However the primary service disconnect panel has to have ground and neutral tied together, and they may share the same bar in this one case. So it is very common to sell panels that have a single combined ground and neutral bar, and then to sell separate grounding bar kits to permit subpanel use.

In your main panel, you would connect the red and the black to the appropriate supply breaker (a two pole 60A breaker). You would connect the white to the neutral bar and the ground to the ground bar (if this is your main disconnect panel, then this will be a single bar, as noted above). In your subpanel, you would connect the red and black to supply the phase busses, the white to the neutral bar and the ground to the ground bar.

AFIK the NEC does not require a washer to be on its own circuit unless there are instructions on the washer itself to require this.

The NEC does not require GFCI protection in the exceptions discussed above, since you have discussed this with the inspector, you might want to further discuss not putting the fridge and freezer on the GFCI; better to ask ahead of time and agree on your plans than to get into an argument after the fact.

-Jon
 
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Old 06-23-04, 09:51 AM
R
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Yes, at the main panel the black and white wires get connected to the breaker, and the white and bare wire get connected to the ground/neutral bar.

In the main panel there are usually not separate bars for the ground wires and for the neutral wires. This is because the ground and the neutral are usually bonded together at the main panel. They must be bonded together at one point in your whole installation, but only one point.

At the subpanel you install you must have separate bars for the ground and neutral wires, and the neutral bar must NOT be electrically bonded to the panel itself or to the ground bar.

Regarding the GFCI, my suggestion is not to fight city hall. I would initially place all receptacle outlets on a GFCI, and then swap receptacles after the inspection to get the refrigerator, freezer and washer off the GFCI. As has been stated, you run the risk of tripping the GFCI with a refrigerator and/or freezer and then having all the food spoil. The washer may trip it also, but that usually only results in lost time and unfinished laundry.
 
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Old 06-23-04, 10:32 AM
J
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Does this mean black to one hot bus, red to the other
As both Bob and Jon said, the black and white are not connected to the bus in the main panel, but to the 60-amp breaker in the main panel.

You should not use 'Romex' for this application
Romex is a brand name. UF-B and NM-B are both sold under the Romex brand. What Jon means is that you should not use NM-B for this application.

I would initially place all receptacle outlets on a GFCI, and then swap receptacles after the inspection to get the refrigerator, freezer and washer off the GFCI
Don't try to trick your inspector. It's bad for both of you. I don't know many inspectors who are ignorant of this very common code exception (at least I really hope there are not many). It's not a gray area of the code, and it is not hard to interpret.

I thought NEC required the washer be on its own
Code requires the circuit to be dedicated to laundry area receptacles. As long as all the outlets are laundry area receptacles, the code does not specify what you are allowed to plug into them.

Are subpanels sold that don't include a grounding bar?
Some panels are sold with a grounding bar, some without. The manufacturer does not know whether you are going to use the panel as a main panel or a subpanel.
 
  #10  
Old 06-23-04, 11:26 AM
R
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John,

I am NOT talking about tricking or fooling the inspector. I am suggesting that if the inspector won't allow the refrigerator and freezer to be on a non-GFCI circuit to put them on one, and then later (especially if nuisance trips occur) to change the receptacle to a standard one.

In my opinion this is not tricking the inspector, as I do believe that the inspector is wrong in this case. It's just not worth tht etime or aggravation to convince the inspector to change his opinion.
 
 

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