Garage Plans - The Subpanel

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  #1  
Old 10-20-05, 07:32 AM
d2frette
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Garage Plans - The Subpanel

Once again, good morning everyone -

I'm planning my garage -> workshop conversion. Here is the original thread for background:
http://forum.doityourself.com/showthread.php?t=236062

Here are my needs
# of Circuits : Amps for each circuit : Purpose of the circuit(s)
2: 20: Generap Purpose Recepticles in main 2-bay area
2: 20: Generap Purpose Recepticles in 3rd bay area
2: 20: Lighting over main 2-bay area
2: 20: Lighting over 3rd bay area
1: 20: Sprinkler system which I will install myself
1: 20: Dedicated circuit for additional front lights and recepticles
1: 20: Dedicated circuit for additional back yard lights and recepticles
1: 20: Dedicated circuit for computer, tv, and stereo
1: 20: 220V dedicated for my 1.5HP 9Amp tablesaw
x: x: Future dedicated circuits for future woodworking tools
x: 20: Future dedicated circuits for decorative and holiday lighting
x: x: Future dedicated circuits for inground pool (or for swapping with the main panel to allow a dedicated subpanel for the pool)
* 1: 15 or 20: circuit for front lights, back yard lights
* 1: 15 or 20: circuit for overhead doors, misc recepticles
* 1: 15 or 20: Dedicated circuit for fridge

* = A builder installed circuit effecting the garage which I will leave in the main panel, but I may want to move to the subpanel later in case I need to free up spots on the main panel.

==> TOTAL ==> 13 Circuits, all at 20Amps, with potential for many more 'future' slots. Is this too much? Most panels don't go over 200.
** My main feed is only 150Amp **
I have a friend who will help me convert the 150A to a 200A main feed. I'm wondering if I should convert to a 300A or 400A main feed. Would that be overkill??

For my subpanel, I wanted to get something that would allow me to expand if I choose to do so in the future. I didn't get to go to Lowes, but I looked online. The only product that seemed to fit my needs was this:
http://www.lowes.com/lowes/lkn?actio...P16&lpage=none

It's a 200Amp main panel, 20 spaces, can handle 40 circuits. (what do you call those "spaces," anyway - breaker slots?)

Will this be ok? Can I use a 'main panel' as a 'subpanel'? Have I over-designed my garage?
 

Last edited by d2frette; 10-20-05 at 07:36 AM. Reason: minor edits
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  #2  
Old 10-20-05, 08:25 AM
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I believe that you are 'overdesigning' the _number_ of circuits for lighting in your garage. You seem to have a total of 4 20A circuits...I simply can't see you needing 8kW of lighting, unless you are planning on baking enamel with those lights.

On the other circuits, it looks like you are being quite 'generous', but not excessively so.

I believe, however, that you are making a basic error in understanding what this means in terms of panel requirements.

A 20A circuit does not mean that 20A is actually being _used_. It simply means that you have the _potential_ for using 20A without overloading the circuit.

Similarly, a 200A panel does not mean that you are actually using 200A; it simply means that you have the _potential_ for doing so. Additionally, a 200A panel generally means a 200A _240V_ panel, which could potentially supply 400A worth of 120V loading.

But the fact of the matter is that you won't have everything on at once; you won't turn on all of the lights, turn on the air conditioner and the heater and all of the saws and the dust collector and the sump pump, and and and.... You get the drift: you could have separate circuits which could _potentially_ draw hundreds of amps, but your total actual use will be much less than this.

Depending on the specific circuit layout, it is entirely reasonable that you could have 20 or 30 '20A' circuits, all sitting in a panel fed with a 100A main breaker.

What you need to do is a 'demand' calculation for your garage and your entire house. (Search on the phrase 'demand load calculation' and you will find tutorials). If the number for your garage comes out to less than 100A, then a 100A panel will be just fine. If this number for your entire house comes out less than 150A, then you are just fine with your current 150A service.

You can use a 'main' panel as a subpanel, but remember that subpanels have different grounding requirements. If you use a main panel as a subpanel, you will need to remove the bonding jumper and add a ground bar kit.

-Jon
 
  #3  
Old 10-20-05, 08:54 AM
d2frette
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Originally Posted by winnie
I believe that you are 'overdesigning' the _number_ of circuits for lighting in your garage. You seem to have a total of 4 20A circuits...I simply can't see you needing 8kW of lighting, unless you are planning on baking enamel with those lights.
Well, that's my tendancy. But I am going off the recommendations from others here. =)


Originally Posted by winnie
On the other circuits, it looks like you are being quite 'generous', but not excessively so.
I have been feeling generous lately.


Originally Posted by winnie
I believe, however, that you are making a basic error in understanding what this means in terms of panel requirements.

A 20A circuit does not mean that 20A is actually being _used_. It simply means that you have the _potential_ for using 20A without overloading the circuit.
Yep, I know that part.


Originally Posted by winnie
Similarly, a 200A panel does not mean that you are actually using 200A; it simply means that you have the _potential_ for doing so. Additionally, a 200A panel generally means a 200A _240V_ panel, which could potentially supply 400A worth of 120V loading.
Ah hah! Here is the tidbit that I had read before but completely forgot about!


Originally Posted by winnie
What you need to do is a 'demand' calculation for your garage and your entire house. (Search on the phrase 'demand load calculation' and you will find tutorials). If the number for your garage comes out to less than 100A, then a 100A panel will be just fine. If this number for your entire house comes out less than 150A, then you are just fine with your current 150A service.
Hmmm. I'll have to look into that!


Originally Posted by winnie
You can use a 'main' panel as a subpanel, but remember that subpanels have different grounding requirements. If you use a main panel as a subpanel, you will need to remove the bonding jumper and add a ground bar kit.
Are there good tutorials on removing a bonding jumper and adding a ground bar kit?

Thanks Jon.

- Dave
 
  #4  
Old 10-20-05, 09:19 AM
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It will be different for each panel, and should be pretty obvious. There will be a screw or strap that connects the neutral bar to the metal box. You simply remove this connection. There should be a description of this on the panel label.

Adding a grounding bar is similar; it will be different for different panels, and the instructions should say where it can be connected. Be certain to remove any paint near the mounting screws, so that the bar makes good electronic contact to the metal box.

I don't know of any tutorials on the subject. You will probably find something on one of the many electrical wiring books.

-Jon
 
  #5  
Old 10-20-05, 09:31 AM
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If the ampacity of the existing Service-Conductors = 150 , I suggest that you not replace the Service at this time; wait till you add a substantial additional load in the future.

I suggest a 30-circuit Square-D "Main-Lugs" panel- this type of panel does not have an MCB.It's my opinion that DIYers are best served by purchasing from an electrical supply-house.

You will have to decide between a 60/100 amp Feeder.
 
  #6  
Old 10-20-05, 09:40 AM
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I'm all for overengineering when working on your own house. But you've gone way past overengineering and are well into uncharted territory. Four 20-amp circuits dedicated to lighting one garage is way, way beyond simple overengineering.
 
  #7  
Old 10-20-05, 10:24 AM
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sprinkler

Dave; Tell us more about the sprinkler system. Is this for fire suppression or lawn watering? I'm curious since I'm also building a 2 car garage right now, and know little about fire sprinkler systems. It would surprise me if they depended on line power, however. Just wondering...
david
 
  #8  
Old 10-20-05, 11:41 AM
d2frette
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Originally Posted by telecom guy
Dave; Tell us more about the sprinkler system. Is this for fire suppression or lawn watering? I'm curious since I'm also building a 2 car garage right now, and know little about fire sprinkler systems. It would surprise me if they depended on line power, however. Just wondering...
david
David-

It's an irrigation sprinkler system, not a fire one. I'm not familir with fire sprinkler systems, but I don't think they require power at all. The ones I've seen pictures of usually use some form of PEX pipe, and I've never seen any wiring in the photos.

- Dave F
 
  #9  
Old 10-20-05, 11:50 AM
d2frette
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Originally Posted by John Nelson
I'm all for overengineering when working on your own house. But you've gone way past overengineering and are well into uncharted territory. Four 20-amp circuits dedicated to lighting one garage is way, way beyond simple overengineering.
Well, I am thinking about installing 20+ canned lights in the garage. There are groups of lights, each on a switch.

Switch 1 = 5 lights over bay 1-2
Switch 2 = 5 lights over bay 1-2
Switch 3 = 6 lights over bay 3
Switch 4 = 4 lights over bay 3

I am considering the following options:
(1) All 4 groups on their own circuit
(2) Group 1, 3 on Circuit A; Groups 2, 4 on a Circuit B; The biggest draw will be Circuit A: 11 lights.

I am fine with option (2). Is that what you'd suggest?
 
  #10  
Old 10-20-05, 11:57 AM
d2frette
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Originally Posted by PATTBAA
If the ampacity of the existing Service-Conductors = 150 , I suggest that you not replace the Service at this time; wait till you add a substantial additional load in the future.
I'll leave the service alone. Not just because you said too, but because I did a conservation calculation on my house and needed 175Amp service. That would mean a 150Amp main - which provides [email protected] - leaves 125A.

125A remaining should be enough for the garage, seasonal lighting, and a future pool.


Originally Posted by PATTBAA
...It's my opinion that DIYers are best served by purchasing from an electrical supply-house.
Without hijacking this thread, let me ask this: Why? Do electricians really work in supply-houses? Or, just someone who owns a shop and knows how to pass the NEC exam? Not being sarcastic, but with the economy of businesses these days, they have to really keep wages down to compete with the big box stores.


Originally Posted by PATTBAA
You will have to decide between a 60/100 amp Feeder.
If price isn't that much different, I'll go 100A for sure.
 
  #11  
Old 10-20-05, 12:03 PM
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When you did your load calculation, did you get a requirement of 21000 VA or 42000 VA? Most load calculations give you the results needed in either volt-amperes, or amps needed at 240V. If you need 175A at 120V (21000 volt-amperes) then your 150A service ( 36000 VA) is enough; if the calculation came out to 175A at 240V, (42000 VA) then you probably need to upgrade.

The calculations are usually pretty conservative, but you don't want to push the limits.

-Jon
 
  #12  
Old 10-20-05, 12:33 PM
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d2frette, option (2) sounds fine. That gets us back into the territory of regular overengineering. Depending on the wattage of bulbs you use in each can (with 65 watts probably being the most commonly used can bulb), your most heavily loaded lighting circuit will at least be up to 30% used.
 
  #13  
Old 10-20-05, 12:47 PM
d2frette
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I used this as my base:
http://www.ecmweb.com/mag/electric_d...feederservice/

I did divide out by 240 at the end, so my service panel may not be sufficient!

I only made such a calculation to get a ballpark idea if the home was already pushing the limits or not. I don't know the actual numbers on all the appliances as we have not yet moved into the home.

I can post my numbers if you care to see my math.

Edit to add: My total came to 37,700. / 240 yeidls 157, which means 150 won't be enough. Thus, I rounded to 175.
 
  #14  
Old 10-20-05, 12:54 PM
d2frette
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Originally Posted by John Nelson
d2frette, option (2) sounds fine. That gets us back into the territory of regular overengineering. Depending on the wattage of bulbs you use in each can (with 65 watts probably being the most commonly used can bulb), your most heavily loaded lighting circuit will at least be up to 30% used.
I really want to use 100W bulbs, but I don't think I can find them. 65W bulbs just don't project that much light. I've seen how 5 of them light up our little kitchen. No way! Not when my fingers are on the line with every cut.

Adding more and more cans won't do it, either. They can only project the light so far. I'd prefer larger bulbs over more bulbs.

Edit: I found one type of can fixture at Lowes which has the following in it's description: "Uses 75 watt PAR30 or 75 watt R30 or 100 watt R25 bulb"
link: http://www.lowes.com/lowes/lkn?actio...TWW&lpage=none
What does the PAR30, R30, and R25 mean?? Are they insulation levels?

I may have found my 100W fixture afterall!!
 

Last edited by d2frette; 10-20-05 at 01:40 PM.
  #15  
Old 10-20-05, 02:21 PM
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Re: electrical supply-houses

I have the impression, based on comments that have appeared in this Forum, that there are are two types of people with a peripheral involvement in electrical matters who cause problems for DIYers; "home-inspectors" and sales personal at Home Depot.
 
  #16  
Old 10-20-05, 03:07 PM
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R25, R30, PAR30, PAR38, A,... are all different types of bulbs. Reflector bulbs tend to reflect some of the heat down, so _some_ fixtures will be rated for higher wattage when used with these types of bulb.

One caution: since this is new construction, will the ceiling be insulated? My guess is not, since this is a garage and you are in Texas...but if you do have insulation, you will need fixtures that are rated for insulation contact, and these generally have lower wattage ratings.

You might want to consider something other than recessed can fixtures.

-Jon
 
  #17  
Old 10-20-05, 03:42 PM
d2frette
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Jon -

The 2bay area is part of the house structure - there is a 2nd level above it. We got the optional 3rd bay, which is recessed back 5 feet and not part of the supporting structure. The 2bay area should have batt insulation above it because of the envelope requirements. The 3rd bay will be empty above it.

The fixture is rated to have 100W R25 bulbs, which sounds great to me. Price could change my tune real quick though. The fixture is also "thermal protected" and can be used in damp spots. So, I think it'll suit the garage just fine.

I like recessed overheads because they are pretty much out of the way. I want to stay away from those flourescents which hang down. I am open to suggestions.

- Dave
 
  #18  
Old 10-20-05, 03:45 PM
d2frette
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Originally Posted by PATTBAA
Re: electrical supply-houses

I have the impression, based on comments that have appeared in this Forum, that there are are two types of people with a peripheral involvement in electrical matters who cause problems for DIYers; "home-inspectors" and sales personal at Home Depot.
Quote for truth.

I am prone to listening to those guys because I have run into a few who really know what they are doing. I plan to go to Lowes or HD for one thing, shopping. I'll get advice elsewhere! (Like here)
 
  #19  
Old 10-20-05, 03:46 PM
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Recessed cans in the garage ceiling may also breach the fire-rating of the garage ceiling if the attic did not have a proper firewall between the house and garage. Check with your building inspector as recessed cans in a garage are not typical.
 
  #20  
Old 10-20-05, 09:17 PM
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I think that ipbooks noticed a whopper here.

d2frette wrote:

The 2bay area is part of the house structure - there is a 2nd level above it. We got the optional 3rd bay, which is recessed back 5 feet and not part of the supporting structure. The 2bay area should have batt insulation above it because of the envelope requirements. The 3rd bay will be empty above it.
Clearly, the recessed fixtures that you wish to use will puncture the envelope that is supposed to separate the garage from the rest of the house. This is an extremely important fire wall, and you must be quite careful with penetrations. Think about the materials that get stored in a garage: gasoline in particular. Intact wall board actually goes quite a long way to stopping or at least slowing down the spread of fire.

Properly installing recessed lighting in a firewall goes well beyond my expertise. I believe that there are some recessed lights that are specifically rated to maintain the integrity of a firewall, and there are also techniques where you build a 'box' out of wall board above the light fixture. If you wish to follow this route, then you will have quite a bit of research cut out for you.

This issue also raises a very important point, one that should have been brought up as soon as you started asking questions:

A proper electrical installation involves many details, all of which need to be correct. There are so many details that there is absolutely no way that someone answering your questions could get to all of them. It is quite likely that there are numerous details that you don't even know you should be asking about, and that we've not thought to tell you about. What you need to do is go out and get several books on wiring, and read them. This will provide the necessary background and overview, which will help make your questions useful, and which will protect you from some simple mistake that you didn't know to ask about and that we didn't think to tell you about. Remember that the advice that you get on the internet is really worth what you paid for it

-Jon
 
  #21  
Old 10-21-05, 07:24 AM
d2frette
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Jon, you keep raining on my parade!

Well, I'm very glad I've asked all these questions. I've learned a lot. I may have to give up the canned lights - that's ok. I will find a suitable substitute.

When we have our inspector over to do the final inspection, I'll pose to him my ideas and see what he has to say. He is highly qualified and highly recommended.

I was already planning on getting an electrical book by Tauton's Wiring A House - http://www.amazon.com/gp/product/156...books&v=glance
 
  #22  
Old 10-21-05, 07:36 AM
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I like Rex Cauldwell's books. I believe that I've seen a different version of this book and liked it.

I don't know if Rex will go into details of firewall penetrations, so you may need to look elsewhere for this information.

If you do go forward with the can lights, please write up what you learned about using them in a firewall; that will be useful information to share. As I said, I'm pretty certain that there are ways to do this, but it will be more work than in an ordinary ceiling.

Bouncing ideas off the inspector prior to starting is always a good idea. That way you will avoid making a really bonehead mistake that the inspector will catch and have you pull out.

-JOn
 
  #23  
Old 10-21-05, 09:18 AM
d2frette
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Originally Posted by winnie
If you do go forward with the can lights, please write up what you learned about using them in a firewall; that will be useful information to share. As I said, I'm pretty certain that there are ways to do this, but it will be more work than in an ordinary ceiling.

Bouncing ideas off the inspector prior to starting is always a good idea. That way you will avoid making a really bonehead mistake that the inspector will catch and have you pull out.
I'll share with you all what I learn about penetrating the firewall. I'll probably avoid doing so myself (penetrating the f/w).

The inspector I'm bouncing ideas off of is the final home inspector - we're buying a new construction house. He will likely not be the actual project inspector, though he is a city home inspector.

Again, I'll let you know what I find out. Thanks for everyone's help!

- Dave
 
  #24  
Old 10-21-05, 01:19 PM
d2frette
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My first draft

Here is my initial sketch:

http://www.freephotopost.com/uploads/a568fc36dc.jpg
 
  #25  
Old 10-23-05, 06:06 PM
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My opinions stand as in the other thread for lighting circuits, main garage on one circuit, 3rd bay on another.

I'd 3-way the back row on the main garage with a couple in the 3rd bay, and put the rest of the lights on single way switches. 3-waying L17-10 is redundant IMO.

For the main garage, with the fire rating on the ceiling, I'd really want to consider surface mount fixtures and possibly conduit. For power tools, you MIGHT be able to used flex drops, if installed correctly (if you are thinking of that).

For your main (didn't realize it was there) and sub panel, it should be noted that you cannot build cabinetry or counters in front of them, they must be kept clear floor to ceiling, each 30" wide centered on the panel (in case the dashed line is supposed to be work bench or storage cabinets).
 
  #26  
Old 10-26-05, 09:12 AM
d2frette
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classicsat - you are correct, the dashed line is for cabinets. But I did know that they will have to keep clear of the panels. Perhaps I should put the sub panel all the down to the end of the wall.

The 3-way switches for L10-L16 and L17-L20 is because I want to be able to turn those lights off when I go back into the house if I have forgotten to turn them off. It's for "convenience" (read lazyness).

I do have to consider surface mounts. I posted in another forum outside of this site about penetrating the firewall. Many people responded saying that if it was possible, I'd have to buy special rated lights. Most said they had penetrated it for various reasons, and all had problems with inspections.

Bottom line:
- Surface mount lights instead of cans.
 
  #27  
Old 10-26-05, 09:29 AM
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Surface mount fixtures produce more light, and more even light, than cans do anyway.
 
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