Ground Conductor size for parallel SE

[Fineimages]

Hi again everyone,
Thanks for all the ideas on my initial question. My rewiring project is going slowly forward. To catch you up on what I'm doing and where I am. I pulled parallel runs of 4/0 aluminum URD from a splicebox at the base of the power pole to the meter base. The power company will be running 300 kcmil aluminum from the transformer to my splice box. From the meter base, I ran 300 kcmil through a 2" conduit into a trough. In the trough I spliced a run of the 300 kcmil up to a 200 amp main breaker panel, using 2" conduit, and another splice of the 300 kcmil to a 200 amp disconnect. From the disconnect I'll be running #2 MC 65 feet to another main breaker panel. I ran a 5/8 ground rod in at the base of the meter, and used #4 copper to ground and bond all the panels, trough, and disconnect.

That said, the electrical inspector came and looked at things, so I could at least get the trench filled back in. He started questioning everything I did, and instead of telling me what he wanted, he just kept asking me the same question. "Is that what the code book says?" I thought it was his job to either say it was OK, or tell me what he wants to change it to. But, he didn't, he just kept saying: "I don't think the code says that's what it should be." or would ask me again what the book said. SIGH....

OK, so, the things he thought he didn't like, but wouldn't tell me how he wanted it, were the size of conduit from the meter base to the trough and breaker panels, and the size of the ground wire. He also didn't like that the ground wire was run and attached to the breaker panel in the garage, and then bonded from there to the trough and disconnect, but that's easy to fix. What I don't know, is what size conduit and what size ground wire. When I look at Annex "C", it says I was correct to use 2" for the conduit. I checked 250.66, and it says the #4 for ground was correct, but then I read #1, and wondered if I needed a larger ground wire because I ran the parallel 4/0 aluminum up to the meter base. I just figured, since the power company was only running 300 kcmil, I was fine with the #4. Again, the inspector never told me to change it, he just kept asking if it ws to code.

So, what would you guys do? Should I go through all the trouble and change the conduit size to 2 1/2 adn the ground wire to something bigger, or should I just show him the code book to back up each of the things I did? If I do change the ground wire, what should it be upped to???

Thanks in advance!
Alan

[suemarkp]

First I'll ask some questions. Since you're running 300 KCMIL Al Service Entrance Conductors, I'm assuming you wanted a 250A service. Is this what you intended, or did you think you have more? The parallel 4/0 run would allow more current, but you're limited by the 300 KCMIL AL coming out of the meter to your trough. Why did you run a segment of parallel 4/0 and a segment of 300 KCMIL? Are your conduits PVC, and if so sch 40 or sch 80? What type of wire is the 300 KCMIL (THWN, XHHW, ???).

Is your neutral also 300 KCMIL? What size wire did you run to the ground rod from the meter? Why did you run 300 KCMIL to the 200A panel and disconnect -- can their lugs take conductors that large? Why are you running a #2 (al or cu) off of a 200A disconnect? Is it going to a panel with a 100A main breaker? Can you explain exactly where the #4 ground/bonding wire is going. Much of your service equipment is bonded by the neutral. Metal conduits may need a wire run to a bonding bushing, but only if you have concentric knockouts.

Now for answers and comments. It seems to me you've run things backwards. I would have run larger single wires from the splicebox to the meter (and something like 600 KCMIL would make sense to match parallel 4/0's). Running parallel 4/0 would be OK too if that costs less. Now, from the meter, especially since you're going to two separate panels, parallel conductors would have made a lot of sense, especially parallel 4/0 since that is what the other end of your service is. But running a 300 KCMIL cable is OK IF IT MEES YOUR AMPACITY REQUIREMENTS. Normally, you'd split bolt smaller conductors to this 300 KCMIL wire to each panel (4/0 wires if the panels are 200A).

Your conduit, if sch 40, is maxxed out with three 300 KCMIL THWN conductors. There is no additional room if you need to run anything else through that hole. If sch 80 PVC, you've exceeded the fill unless the conduit is straight and less than 24" long. If you used wire larger than THWN, you're probably over the fill limit too. If you rip out the 300 and go to dual 4/0's in this conduit, then you'll have to use 3" conduit. Or consider using copper for these shorter runs in which case the conduit you have should be fine.

Your grounding electrode is sized per 250.66 based on the largest service entrance conductor. Your service conductors are either single 300 KCMIL's or two 4/0, so need to see which has greater area. A 4/0 wire is 211600 CM, so two of them are 423 KCMIL. This is larger than 300 KCMIL. So for wires between 250 and 500 KCMIL, you need a #2 copper or #1/0 Al GEC. However, the GEC to a rod does not have to be larger than a #6. I'd run a #4 to the rod, and by the way, you must have two rods. If you have any metal water pipes or exposed structural steel, they must be bonded with a #2 copper or #1/0 Al wire. The bonding wires inside the trough and meterbase must be #2 copper or 1/0 Al because these are still upstream of your service disconnect. If you used all plastic conduits, then just terminating the neutral to a lug in the trough should be plenty.

Your grouding electrode conductor can come from many places in your service equipment, but it is only to be used for the GEC and nothing else -- no bonding of enclosures with it. It is also good to run that conductor as straight as you can to the ground electrode.

It is a little disconcerting for the inspector to be wondering aloud as to what the code book says. You're doing an advanced residential service, so he may not have been prepared for all the details. But a commercial inspector should have known about conduit sizes, GEC sizes, etc. Since he's not providing you much protection, I'd study 250.66 (actually most of 250), 310.15(B)(6), and the surrounding text to at least get the conductors sized right.

[Fineimages]

Hi Mark,
Thanks for the reply. I see I didn’t clarify. The 300 KCMIL from meter to trough is copper, not alum. The 4/0 from pole to meter is aluminum. I am wanting 300 amps when all is said and done.

>>Why did you run a segment of parallel 4/0 and a segment of 300 KCMIL?
The parallel is direct burial, and once it’s in the meter, we went to the 300 kcmil copper since it would be easier to work with in the trough.

I used THHN stranded copper from the meter base to the trough, and ran it through an 10” threaded 2” galv. nipple. The only PVC used was up to the meter base, and in and out of the splice box, and those are 2 ½” schedule 80. From the trough to the disconnect and the trough to the one panel, I used 2” long 2” galv. nipples.

From the trough to the fused disconnect, and from the trough to the one breaker panel I mis typed before. Those runs are 2/0 copper, with the neutrals being the same size. The parallel 4/0 from the pole to the meter has a reduced neutral. The lugs and power distribution blocks are all sized correctly. (The power distribution blocks have one 300 KCMIL on one side, and the 2 2/0’s on the other side going up to the disconnect and breaker panel.

The ground wire is #4 solid, attached to a 5/8” grounding rod located directly below the meter. Another #4 will be run from the trough, down to the basement and attached to the water line a couple inches from where it comes in.

>>Why are you running a #2 (al or cu) off of a 200A disconnect?
>>Is it going to a panel with a 100A main breaker?
This is where it MIGHT be dicey. <G> I’ve got a 200 amp panel in the garage, a few inches up from the trough. That’s for garage receptacles, lights, the AC compressors, etc. Then, the other 2/0 goes from trough to the 200 amp fuesd disconnect, with the MC coming out of it 65 feet to a SECOND 200 amp panel. It isn’t that I am going to run 400 amps, but I need all the home runs for the lighting controls I’m putting in.

OK, let me see if I can explain the grounding I just did. #4 solid copper from ground rod up to ground bar in garage breaker panel. Then ran #4 stranded to insulated bushings at each end of the nipples going to all boxes. (trough, disconnect, generator transfer switch, meter base, and 200 amp panel.) The other ground isn’t installed yet, but will attach to the 200 amp breaker panel in the garage, and go to the water pipe.

>>Running parallel 4/0 would be OK too if that costs less.
That’s the exact reason for doing the parallel 4/0. TREMENDOUS price difference here when I checked. <G>

>>Normally, you'd split bolt smaller conductors to this 300 KCMIL wire to
>>each panel (4/0 wires if the panels are 200A).
Right you are, which I did, just mistyped before.

Am I OK on the 10” nipple from meter base to the trough, when it comes to fill capacity? I thought I was.

>>I'd run a #4 to the rod, and by the way, you must have two rods.
I did run #4 to the ground rod, but the inspector here said only ONE ground rod, and the other MUST be the water pipe. I thought 2 ground rods would be fine.


>> If you have any metal water pipes or exposed structural steel,
>>they must be bonded with a #2 copper or #1/0 Al wire.
>>The bonding wires inside the trough and meterbase must be #2 copper
>>or 1/0 Al because these are still upstream of your service disconnect.
DARN! I used #4 for bonding the insulated bushings. Does it matter that the electric company is only going to run 300 KCMIL from the pole? Can we not get by with #4 ground since the weak link is the power company run from the pole?

>>It is a little disconcerting for the inspector to be wondering aloud
>>as to what the code book says.
MY SENTIMENTS EXACTLY!!!! I could not believe it. He kept quizzing me. I was rushed, put on the spot and didn’t have my books with me to quote chapter and verse. <G>

I’ve got a sheet with notes to justify what I did, but this ground wire size was a bit confusing. So, with all I’ve explained, what do you think now?

Thanks!
Alan

[suemarkp]

Good, the 300 MCM copper gets you a service rated at 300 amps. I'm still confused with the size of wire to the 200A panel and 200A disconnect. You said you split bolted to the 300 MCM wire -- did you splice on 2/0 copper, 4/0 al, or something else?

For your nipples, they are each less than 24" long so you are allowed 60% fill rather than the normal 40% fill. Three 300 MCM THHN wires in a 2" galv conduit are near maximum fill at 40%. Since you can go to 60%, you have room for more. I can't tell if your 2.5" conduits are OK because I don't know the size of the URD and whether that is individual wires or a cable. I'll assume you calculated those correctly....

The ground rod connection is OK, except that you are required to have a second rod if you can't prove your existing rod is 25 ohms or less. The fact that you have a water pipe ground is not relevant. If you had any other type of ground (buried wire, concrete rebar electrode, etc) then an additional rod wouldn't be needed.

The conduit bonding wires in the trough and meter base are to be sized per the largest service entrance conductor. The fact that the power company runs teeny wires upstream of you doesn't matter (but even 300 MCM aluminum requires a #2 copper bonding jumper). I did this for you before, but thought the 300 MCM was al not cu. However, you still get the same answer -- you've got to have #2 copper in those locations, not the #4 you used. Is the trough bonded to the neutral in any way (perhaps a triple lug is bolted to it)? If not, you'll need a #2 bonding wire to the metal trough. Inside the disconnect and 200A panel, a #4 conduit bonding wire is OK.

The water pipe ground also must be this larger size (and this is regardless whether the pipe is metal in the yard dirt or not) -- if the water pipes are metal in the house, they must be grounded or bonded with a #2 copper, not the #4 you were planning.

Your 200A panel off the 200A disconenct is definitely a problem. You either need to change the disconnect to 100A, or change the wire to 2/0 copper. You could also replace the 200A disconnect with another 200A main panel (like the other main one), and put a 100A breaker in that panel to feed the 200A panel 65 feet away via the #2 MC cable (this is probably the cheapest and most versatile solution).

[Fineimages]

Mark,
Sorry for the delay in replying to you. Power was out for a week here in Louisville. 115,000 people without power due to a freak 70 MPH wind storm that blew through on a week ago Tuesday. Over 3200 power lines came down. Then, another storm came through and took out 6,000 more homes 3 days ago. Being without power for 5 days put me so far behind, I’m just now getting caught back up. So, I wasn’t trying to ignore your prompt reply to my questions. <G>

>>did you splice on 2/0 copper, 4/0 al, or something else?
Spliced on 2/0 copper to the 300.

>>I'll assume you calculated those correctly....
Yes, I did calculate those correctly, and my supply house said this is what they sell everyone on a regular basis. I also thought I was correct using the 2” nipple. Thanks for clarifying that.

It’s interesting that you say I need an additional ground rod, along with the water pipe. This inspector was adamant that all he would require is the one rod and the water pipe. I’ll play it safe though and add the second rod at least 6 feet from the first, just to be sure a different inspector says something different. <G>

OK, so it sounds like I need to change to #2 no matter what for both grounds. Not a problem, since I hadn’t pulled the one all the way through the house to the water pipe yet. I’m only out a bit of money on the #4 I already purchased. I wasn’t sure if it mattered about it being alum or copper. Good to know that the #4 between disconnect and trough is OK though. We have the trough bonded to the neutral now.

>>Your 200A panel off the 200A disconnect is definitely a problem.
>>You either need to change the disconnect to 100A, or change the wire
>>to 2/0 copper.
OK, I need to learn how to type better, or proof-read what I type better. <GRIN>
It is 2/0 copper going from the trough to the disconnect, NOT #2, and then 2/0 going to a generator transfer switch, and 2/0 MC going the rest of the way to the 200 amp panel in the basement.

So, it sounds like as long as I swap my ground from #4 to #2, from the ground rod to the panel/trough, add a second #2 ground to a second ground rod, and run a #2 to the water pipe, I should be fine. Good to hear!!

One more question while I have you. I am needing more than 40 breaker spaces in the basement, and want to do two 40 space panels. Can I use two 200-amp main breaker panels, and pass through from one to the other, or is that then considered a 400 amp service? There isn’t any way I could load the thing with 400 amps, but am wanting it because of all the individual home runs I need for a home automation system I am hooking in. The Square-D panel (QO series) does not offer a pass-through lug on the bottom, so I was going to put another splice block on it once it comes into the first panel, and take it over to the second one. That would give me 80 spaces, which is plenty. Or, should I swap out the 200 amp breaker in each of them, and just put a 100 amp in each panel? Or “D”, none of the above? 

Thanks Mark for the advice!
Alan

[mdshunk]

You could use an NQOD (Square D) panel to get the feed through lug option (this panel takes QO or QOB breakers). Or, you could feed out of a breaker in panel #1 to the lugs in panel #2. Or, you could bring the 200A line to a wire trough, and bug the wires down to both panels. Don't know which one Mark's going to reccommend... (my personal preference would be the trough).

[Fineimages]

That was a quick reply. <G>
I looked at the NQOD panels for just that reason, but they are considerably larger and more expensive than QO ones, so I went with the QO.

This might be dumb, but how do you get such a large wire into a breaker? Do they make some sort of lug that attaches?

I also thought about the trough. Let me ask you this. I am recessing the two panels into a wall, with about a 6" space behind the wall, to the concrete foundation behind the wall. One panel is going to be mounted between 2 studs, and the other panel between the next 2 studs. If I use a trough, would I need to put a brace in this wall, and cut the middle stud out between the two panels, and mount the trough just below them? (I'd have to mount the panels upside down to feed them from the bottom.) This way I can run my home runs up the top and out. Do they make a trough that would allow recessed mounting? I do care how this all looks. <G>

Lastly, is it OK to do what I intended, using 2 panels with the 200 amp main breakers in each, when I only have a 300 amp service coming into the house, and the feeder wirie is only rated for 200 amp service? Is it assumed that the fused disconnect will protect things before the feeder wire causes a problem?

Thanks to both you and Mark! (And others here!)
Alan

[suemarkp]

You can have as many panels as you want hanging off that 200A feeder. What matters as far as your 300A service size is what is the calculated load connected to the 2 (or more) 200A panels. If its less than 200A, then you're fine for the feeder, and if the rest of your service is 100A, then the total service being provided is adequate. If those panels only calculate to 60A, then you have a huge margin in the feeder and can have 240A of other equipment connected to your service. I know you need a bunch of breaker spaces, but I'm curious what your calculated load is on these basement panels -- I can't believe you'd need more than 60A for lighting only circuits.

I think you can find a wireway or trough to do what you'll want, but I'd say yes you'll need to cut the center stud and put a header of some sort below it (4x4, doubled 2x4). This could complicate how you get the conduits out of the gutter and into the panels, as you may need to take a significant hunk out of the header.

You may be better off to just put a 100A breaker in the first panel and run a #2 copper (2-3 w/gnd) cable or a 1.25" conduit to the second panel. You'll only have 100A available to the second panel (and its still OK to have a 200A main on the second panel if you want or you can go MLO).

[Fineimages]

Mark,
I haven't done an official calculation, because I am currently living in an identical house to the one I am remodeling, and am directly across the street. Where I am now, I have almost the same amount of stuff running on a 100 amp service, and haven't tripped a breaker once. There will be several large UPS units for all the computers. (I runabout 5-6 servers in a rack at a time, along with a few other machines as needed.) So I was fairly confident that 200 amps of service was plenty, but was more concerned about breaker spaces. Should I do an official calculation of the loads I will be running off this, even though I am confident I have plenty of headroom?

I will look and see about a trough. If I can get one that fits, I can bolt it directly to the panels from below, using close nipples to get the conduits between the two.

Thanks again for the help.
Alan

[Wgoodrich]

Alan

Without performing a demand load calculation per the NEC rules found in Chapter 2 then you are only guessing. Guessing when it comes to electricity is not a good thing. Does not take that long to calculate a demand load calculation. Do you know a format to perform this demand load calculation? If not look at the top of this page in the green and yellow boxes for "demand load calc and follow the instructions. Then you will be making an informed decision.

Good Luck

Wg

[Fineimages]

OK, I think you talked me into it. <G>
I'll do a calculation this weekend and see what I come up with. I should have remembered that when you assume something, you get in trouble. <G>

Thanks for the reminder to be more careful!
Alan

[Wgoodrich]

Alan

I think that would be a professional move on your part. Let us know how you come out on your answer. Might be interesting.

Wg

[Fineimages]

OK folks,
I sat down and did my calculations last night. Now, I might be off slightly, in that I really don't know how much extra load is going to be put on some of the basement circuits by the computers and UPS units, but judging from my numbers, it shouldn't be enough to cause any problems, since I have plenty of head room. I added in what I think I will have. I used the formula and came up with a total of 190 amps. Of that 190, 60 is going to running from the 200 amp garage panel. (Some lights, the 2 A/C compressors, and some of the branch circuits.) I went ahead and added the square footage of the attached garage, and the main living quarters, and the basement, and used that total as my starting point.

That leaves 130 amps split between the 2 200 amp basement panels. I did not calculate how much was going to go to each panel, since I prefer to put all of the office/basement on one panel, and all of the residence/upstairs on the other panel. I know it probably would be best to equalize teh loads between the two, but it will be easier for me to do it just by each floor going to it's own panel.

I am going to have all my calculations ready for the inspector, since he's been a pain, to prove I am OK with what I am doing.

My buddy and I went ahead and mounted the trough and 2 panels, and that was a good idea. That worked out really well. Thanks for the suggestion!

So, does everything sound good so far?

I will let everyone know if it pases inspection, hopefully I can be ready for that next week sometime. Let me know if I am forgetting anything, and thanks again for all the help. I will be posting another couple questions soon I am sure. <G>
Alan

[suemarkp]

For what you've said, yes. Do you feel like making your calculations public? I'm still surprised you have a 130A load for inside the house unless that includes an electric range, electric clothes dryer, and electric water heater. Did you apply the demand factors as allowed for more than 3 fixed appliances? Did you include the kitchen and laundry appliance circuits in your general load calculation so the demand factor can be applied? Did you treat the computers as continuous loads (don't have to for a residence, but I would if you plan on running them 24/7).

Overall, it seems like a choice of 300A service was a good one, as you'd be pushing a 200A service.

[Fineimages]

Mark,
I don't mind sharing at all. I did consider the computers as on full time. Even though it is a residence by nature, it is more of a business, so I wanted to err on the side of caution.

I'll type up my hen scratchings and post them this weekend. <G>
Alan

[Fineimages]

Yikes!!!! After sitting back down, and adding some things I had forgotten the first time, and corrected some addition errors, here is what I came up with. I was considerably off. I now get right about 250 Amps. Would you mind glancing at things, and see if I missed something, or am forgetting to make an adjustment anywhere? I wasn't sure if some of the items I am listing as appliances can be considered part of the general small branch circuits.
What do you guys think?

Load calculations for entire house.
1975 square feet main floor + 1250 square feet of basement + 425 square feet of garage to be used as warehouse and shop.
220.3.A - 3650 x 3 Va = 10,950
220.16.A – 3,000
220.16.b – 1,500
Total = 15,450
220.11 – First 3,000 x 100% + 12,450 x 35% =4358 = 7358
220.21 – Heat is natural gas so used A/C.
Two separate 2.5 ton A/C units, each drawing 19 amps minimum. 19 amps x 240 volts = 4560 x 2 units = 9120 minimum.
220.17 Fastened in-place appliances. Number beside each item was calculated using Amps x Volts x 75% for more than 3 fastened in place appliances.
Water Heater – NATURAL GAS, so omitted.
Dishwasher - 1050
1/3 HP Garbage disposal - 648
½ HP Sump pump #1 – 882
(Basement water proofing & condensates for furnaces)
½ HP Sump pump #2 – 882
(Ejector pump for basement bathroom)
Furnace motors (two) - 1700
Refrigerator - 585
Microwave - 900
Whole house vacuum system – 1085
Jacuzzi tub in bathroom - 882
Hot tub outside - 4650
Air compressor for garage – 1350
(Permanently mounted and piped into basement)
Ceiling fans (4 of them) – 60
½ HP Garage Door opener - 882
Clothes washer - 630
½ HP motor in dumbwaiter – 882
Rack mounted UPS units and computer equipment for business – 5,250
Total of three 1000 Va and two 2000 Va UPS units, powering all computer and network equipment)
220.18 - Electric clothes dryer – 6725
220.19 - Electric range – 14,250
220.14 + 430.24 – Motors – included in above calculations.
Sub Total of all appliances – 43,300
Total = 59,777 Va
Divided by 240 Volts = 249 Amps

Using the items above, and proportional square footage calculations, I have the entire load split between the three 200 amp 40 space breaker panels in the following way:

Garage 200 Amp panel = 78.44 Amps
Square footage load (2.0157 Va per square foot) – 857
Appliances – 17,969
Total Va = 18,826

200 Amp panel for main floor loads = 123.8 Amps
Square footage load (2.0157 Va per square foot) - 3981
Appliances – 25,731
Total Va = 29,712

200 Amp panel for basement loads = 46.8 Amps
Square footage load (2.0157 Va per square foot) – 2520
Appliances – 8,712
Total Va = 11,232

[suemarkp]

I think I see a couple of mistakes:
When you added the fixed appliances to the base load, shouldn't that be 43,300 + 7,358? It looks like you added the full 15,450 -- the value before demand was considered.
Did you add the 25% penalty for your largest motor load (probably one of your air conditioners)?
Is the nameplate value of your range 14,250? If so, and this is one range and not a series of ovens and cooktops, then you only need to calculate it as 8,800 VA.
The clothes washer doesn't need to be counted, as the 1500 VA laundry circuit is expected to take care of that.
The refrigerator is assumed to be part of the kitchen small appliance circuit. If this is an additional one located in a basement or garage, then I'd leave it in the calculation.
You may want to multiply the UPS load by 1.25 since it is a continuous load (but use your actual anticipated load and not the max rating of the UPS -- perhaps it will work out the same if you loaded the UPS to 80% as most makers intend).

When you calculate the load on each panel, you should start the calculation over based on the square footage that panel serves and the appliances connected to it. You'll find that each panel, when added up this way, exceeds your service calculation, but that is OK. It just means that a 300A calculated service probably can not be implemented by three 100A feeders. This won't be a problem for you.

[Wgoodrich]

Fineimages, congrats on doing your own research and attempting your own demand load calculation.

I used the numbers you provided dropping the redundant loads you had and performed a quick demand load calculation using the info you provided. However I question your 17,969 load in your garage for appliances. Are you aware that if you are the only person working in that garage even if you had 10 - 100 amp machine you can only run one manually operated machine. You should find the largest one manually operated machine in amps, increase that 125% then add the full load amps of only auto operated machines that may come on at any given time while you operate that one manualy operated machine. This may adversely affect the following answer. All else have been adjusted concerning redundant loads.

My answer right now including the questioned 17,969 machine loads in garage due to noncoincidental load suspected there is 269.4 amps demand load as I calculated using your figures correcting where I knew to correct.

This would call for most likely a minimum of a 200 amp and a 100 amp service panel set up in parallel from the meter base giving you a 300 amp service. Suspect if you research cost little more cost would occur to just install two 200 amp parallel main service rated panels. Remember these to parallel installed service panels must be grouped together.

Relook at you garage appliance load number you provided. Probably will make a difference.

Hope this helps and congrats for you helping yourself doing the proper research. Best move you made.

Good Luck

Wg

[Fineimages]

Thank you both Mark and Warren for the input, support, help and compliments! I really do appreciate it! If you both only found a few mistakes, I feel much better, because I sure wasn't sure I had it correct. <GRIN>

I was shocked at how long it took to do the calculation, and how hard it really was to try and cover all my bases, and as I see, I even under-estimated again. Makes me feel much better about my decision to bring in a 300 amp service, even when my friends all thought I was going way over-board.

I broke out the items by panel below, to help you see what I was doing. The reason the 17,000 is so high, is that the 2 AC compressors and a future hot tub for outside are all going into the garage panel, to try and equalize the loads some between the three.

To address a couple things you both brought up, and not in any particular order. <G> First, one of the reasons I was rating things a little high, is that there are times I have as many as 3 people working with me in the business, and so, things like the air compressor, vacuum, more computers, etc., could theoritcally be on at one time. (Not to mention the hope that some day, someone might consider marrying me, and raise the number of people living there. <GRIN>)

Moving right along, what I have already done is basically install three 200 amp main breaker panels in parallel, with the loads divided between them in such a fashion that no one panel should be overloaded. I did check cost, and right you are warren, it was very little extra to do everything this way, than to do two 200 amps, and one 100 amp, even though I didn't really need the spaces out in the garage.

Mark, you wrote: When you added the fixed appliances to the base load, shouldn't that be 43,300 + 7,358? It looks like you added the full 15,450 -- the value before demand was considered. What I did was add the 43,300 + 7,358 for lighting + 9120 for the two AC compressors (Heat is gas, so AC was used for calculations.)

I didn't add the 25% penalty for one motor load, thanks for pointing that one out, and right you are, one of AC motors would be the one, so I need to add another 1140 to my total. Then deduct 630 for washer. Only one fridge, so deduct 585 also. So, as you say, a wash between the three. <G>

As for the range, I don't have it yet, and couldn't find the exact numbers on Jenn-Air's web site. It has the highest heat rated elements that I could find on their web site, so I made a guess that it is 19,000, which I took down to 14,250. A bit of a guess, but looking at how they do their model numbers, I think I'm pretty darn close. I can double check that next week when I can talk to Jenn-Air and see.

On the UPS units, that is so tough for me to know what to calculate. If the power goes out, those suckers kick in almost 100% if they are on, so I rated them at their full output. Will I always have them maxed out? No. Will there be times when I might? Yes. I saw that they can only be loaded 80%, and again, agree that the 125% vs 80% made for a wash. Right now, there won't be 5 of them, but I was planning for some growth, adn feel that is a good estimate of what could realistly be installed.

>>When you calculate the load on each panel, you should start the
>>calculation over based on the square footage that panel serves
>>and the appliances connected to it. You'll find that each panel,
>>when added up this way, exceeds your service calculation,
>>but that is OK.
HMM, I really thought I did that Mark. See below. I took the total of 7358 for square footage, and divided it by 3650 (square footage of all three areas.) and that gave me the 2.0157 per square foot number. I then too that times the square footage of each area a panel will service, and got the numbers I listed below for each panel. What was I supposed to do differently? It would be good to have down for when teh inspector comes back out. I want to show him that I am OK with what I am planning.

Thanks again, and again, and again everyone. I sure hope others are learning a lot from this thread. I feel like I am getting long winded, and I hope I'm not boring everyone. <G>
Alan

Here's how it breaks up by panel, square footage and loads:
Garage 200 Amp panel = 79 Amps
Square footage load (2.0157 Va per square foot x 425 sq.ft.) = 857
2-Air Conditioner Compressors – 9120
Whole house vacuum system – 1085
Hot tub outside - 4650
Air compressor for garage – 1350
(Permanently mounted and piped into basement)
½ HP Garage Door opener - 882
½ HP motor in dumbwaiter – 882
Total Appliances – 17,969
Appliances plus square footage = Total Va of 18,826.

200 Amp panel for main floor loads = 124 Amps
Square footage load (2.0157 Va per square foot x 1975 sq.ft.) – 3981
Dishwasher - 1050
1/3 HP Garbage disposal - 648
Refrigerator - 585
Microwave - 900
Jacuzzi tub in bathroom - 882
Ceiling fans (4 of them) – 60
Clothes washer - 630
Electric clothes dryer – 6725
Electric range – 14,250
Total Appliances – 25,730
Appliances plus square footage = Total Va = 29,711

200 Amp panel for basement loads = 47 Amps
Square footage load (2.0157 Va per square foot x 1250 sq.ft.) – 2520
½ HP Sump pump #1 – 882
(Basement water proofing & condensates for furnaces)
½ HP Sump pump #2 – 882
(Ejector pump for basement bathroom)
Furnace motors (two) - 1700
Rack mounted UPS units and computer equipment for business – 5,250
Total Appliances – 8,714
Appliances plus square footage = Total Va = 11,234

[suemarkp]

I think your 2.0157 VA/sq ft number is not correct. In each panel, take the area it serves and use 3 VA/ft2. This will increase the load on a given panel from what was calculated for the overall service, but not by much. I understand what you've done by using 2.0157 and it may be permissible, but I can't find that in the code anywhere.

You should also apply the largest motor penalty to each 200A panel (so add 25% of AC to garage panel, 25% of jacuzzi tub for main room panel, and 25% of a sump pump for the basement panel).

Finally, even if your range was nameplated at 19KW, your calculated value would be (19 - 12) = 7; 7 x 5% = 35%; 8KW + 35% = 10,800 VA. If you had a "normal" 12KW range, the service calc value for that would be 8 KVA.

[Wgoodrich]

Unfinished basements and garages for lighting would calculate .25 Va per square feet for unfinished basements [storage area] and .5 Va for garage areas. See table 220.3.A

3 Va is required for general lighting [including receptacles in living areas] for dwellings. See table 220.3.A.

Fineimage. I believe you calculated your A/C for heat then again for garage load. This may be causing you to be off in you calculation some.

You need to calculate the garage demand load then the house demand load separately Then add them together. Then calculate sub panel loads only for loading of that certain panel separate from the demand load calc.

Be careful. If you garage is a detached garage you are not allowed to provide power back to the house A/C units causing two main power sources from two separate buildings to one building. If a person shut the main off at the house thinking he cut all power he still has power to equipment associated to the house from the garage. Invite for shock hazard. This is not allowed.

Just some thoughts

Wg

[Fineimages]

Mark,
Is there an article reference I can jot down showing where you got the 3 VA/ft2 figure? I'm wanting to document everything for this inspector. He seems to want me to be able to quote the code book by heart. <G> I'll replace the numbers with the 3 Va, which raises everything a tad, but not enough to put me over on any of the panels. Thanks for pointing it out!

I also added the 25% penalty to each panel. Again, is there a reference in the code book for that? Is it 220.4.A? If so, is the term "circuit" meaning I count each panel as a circuit?

Not sure how you are coming up with the range calculation, but I trust you on that one. <G> I'll reduce that in my calculations, which helps a bit. I know I'm save either way, and I am sure the inspector isn't going to really look at that too hard. My main concern is that I am safe, which I am confident that I am with either number.

Thanks for all your input. I am sure learning a lot!
Alan

[Fineimages]

Warren,
Thanks for giving me more to calculate. <GRIN> Seriously though, doesn't that .25 figure apply only to occupancies OTHER than single family dwellings? Again, as long as I am safe with what I am doing, I'd rather show the inspector a calculated load slightly higher than what it really is, so as long as I am wiring for that, I am covered if it is a little less. Although, I do like being accurate. <G>

As for A/C calculated twice, no, in the top section of my post, I listed everything, and in the bottom section, I split it out by panel. As far as I can tell, the 9120 load is only listed once in the top section, and placed in the correct panel.

I'm not sure what you mean with calculating of garage load seperate from house load and sub-panel loads. The way I have this all wired, there really aren't any sub-panels. It's 3 parallel 200 amp panels, just in 2 different locations in the house. Does that mean I have calculated this correctly, or do I need to adjust something?

The garage is attached to the house, and the way I have it wired, is coming from the meter at the back of the garage, into a trough, and directly above the trough I have the one 200 amp main breaker panel and next to that the 200 amp disconnect which disconnects the two main breaker panels in the basement. So, in this situation it isn't bringing power back to the house.

Again, Warren, thanks for pointing things out to me! You guys have been great!!

Not to add to the confusion, but you did bring up a point I am trying to figure out. What makes a basemetn finished or unfinished? Is it flooring, ceiling, walls, or a combination of the above? I am drywalling all the walls in 75% of the basement, putting tile in ALL of the basement, and ceiling in NONE of the basement. So, when reading code and exceptions, do I assume this entire basement is considered finished, or can I claim the are without finished walls is unfinished basement space? How many finished walls in an area make it finished or unfinished?

Alan

[suemarkp]

First thing to realize is that the calculations can be done for Services, Feeders, and Branch Circuits (see 220.10). The one you did was the Service calculation which globs everything together. But you have a 200A feeder (from the disconnect to the two basement panels). In order to see if you've overloaded that feeder, you perform a calculation for everything connected to that feeder (square feet, fixed appliances, etc). You do the same thing as the service calculation, but you limit the scope to only the items and space served by that feeder. Since your two basement panels are in parallel on that 200A feeder, you can merge the equipment they serve together.

You should also do a calculation for the garage panel separately, as it is limited to 200A by wire size and breaker. Technically, it is a service and not a feeder, but its not your whole service so a separate calculation should be done.

The 3 VA/Ft2 value comes from table 220.3(A). True, that tables lists garages at 1/2 VA/Ft2, but that is commercial garages. Houses have so much stuff in their garages, I think 3VA/Ft2 is barely adequate. NEC 220.3(A)says you don't have to include open porch space, garages, or other unused/unfinished space NOT ADAPTABLE FOR FUTURE USE. I'd be safe, and just use the whole perimeter of your house in the 3 VA/Ft2 calculation.

The motor penalty is buried in the motor section (Article 430). This basically says that each branch circuit or feeder supplying motor loads (or a combination of motors) must be sized at 100% of the motor FLAs + 25% of the largest motor FLA connected to that feeder and/or branch circuit. If you have one motor on your panel, then you have to add that 25% penaly to that panel's feeder. If you have 100 motors on a panel, then you just add 25% of the largest one to the panel's feeder (but each motor branch circuit gets its own 25% penalty based on the motors it serves).

The range calculation is done per 220.19 using Note 1 and Column C of table 220.19.

[Fineimages]

Thanks again Mark,
I just wanted to have the sections handy in case he grills me again. I am pretty sure if I get the same inspector, he will want proof of why I did what I did, and if I show him my calculations, I doubt he will refigure it, but he just will want to see them.

OK, now that that is settled, I will let everyone know how it turns out, and start a whole new bunch of questions on other things I'm planning on doing. I do think it's a shame that he will not allow me to ask him questions BEFORE I do something. I really feel that is part of his job, to listen to what I plan on doing and say, yes or no before hand, but he point blank told me that's not his job. So, I have a feeling I'll be having to redo a bunch of things through-out this project. <G>

Alan

[Wgoodrich]

Some inspectors feel it is part of their job to promote electrical code knowledge. Some inspectors feel it is only their job to pass or fail an inspection they are doing providing no further information other than violations of design.

Seems your inspector is using you against you. Sounds like he is asking questions making you defend what you have done. Seems to me he should either pass or fail you. Then defend his ruling by providing the NEC rule reference numbers that you violated. Just my opinion. Seems he is putting you on the hot seat making you prove you know. Not really a fair way to treat a person he or she is inspecting in my opinion. I would provide him with my calculations and let him defend his rulings after he rules. We can help you defend your stance by providing proof of NEC rules and reference numbers to back it up. Work with him but don't let him or her intimidate you by his or her authoritative position. Remember he or she is there to serve you not the other way around.

You say you have no sub panels yet you have main service disconnects with panels fed as slaves of those disconnects in the basement. These panels are servinng as slaves of the main service disconnects are what the NEC calls nonservice rated panels. We often refer to them as sub panels. Sub panels fed power from a main disconnect installed nearby your other main service rated disconnects an main service panels are required to be grouped together at nearest point of entry of the service conductors entering inside the building. Also be aware those sub panels must be wired with the neutral bars isolated from equipment grounding and must get their equipment grounding source from those main service panels or disconnects serving them power.

The 125% increase rule may be found in NEC 430.24 that suemarkup was referring to. Suemarkup and I seem to be saying the same thing in different ways. What he has said is accurate and in my opion just a professional as others replying in this forum making our forum as popular and valuable to all as it seems to be. I am proud of all who take the time to reply to these forum questions. In my proud opinion you are in good hands.

Good Luck

Wg

[Fineimages]

Hi Warren & Mark,
Good news guys, the inspector finally came by yesterday and gave me the OK to have the power turned on to the breaker panels! YEAH! I lucked out and got a different inspector this time. He complimented me on what a nice looking installation it was. I pointed out all the things I corrected per the previous inspector's instructions, and he sort of chuckled, and said it looked fine to him, and couldn't see why the other guy didn't like it. This guy even stuck around and answered questions I had concerning the next phase of things. His approach was great. That's the way they all should be. He explained things, answered my questions and was resonable. For example, He said normally there would be a rough-in inspection, then the On/Off inspection, then the final. But he understood why I wanted the off/on first, and put the sticker on. He said, it was clear to him that anyone who went to the trouble to make this look so good, would be fine to have the power on. Then told me what he wanted to see for the next inspection. Like I said, a very reasonable guy.

I shot a couple photos of the installation if you would like to take a look:

http://www.fineimages.com/house_renovations.htm

I didn't have the ground bars attached yet to the basement sub-panels, and he said fine, but to make sure I had them on before the power company turned on the juice. I said no problem.

Again, I can't thank you guys enough for all the help and advice. I'll keep you posted as the rest of the project progresses.

Alan

[Wgoodrich]

I am picking up that you ran a 200 amp main service rated distribution panel in your garage and a second main being a main service rated disconnect 200 amp rated. This would give you a 400 amp service at that location. Then I am picking up you ran a 200 amp feeder from the 200 amp disconnect through a transfer box then feeding 200 amps to the house basement. This one 200 amp feeder serves 2 - 200 amp sub panels. This would give you 80 circuits in the basement but only 200 amp worth of power in that basement. Is that whate you planned?

Second the feeder leaving that 200 amp disconnect feeding through the transfer box and on to the 2-200 amp sub panels in the basement, what size are those wires? I am taking it that you only ran one 200 amp feeder to serve the 2-200 amp sub panels. Is that your plan?

Also it is hard to pick up for sure but it looks like you joined together electrically both the neutral and grounding bars in those 2 - 200 amp subpanels. A sub panel requires two hot, one neutral and one equipment grounding wire to serve that sub panel then the neutral bar must be isolated electrically from teh grounding bar. Is this what you have done in those 2-200 amp sub panels. Did you isolate the neutral bar from teh grounding bar?

Curious

Wg

[Fineimages]

Hi Warren,
Let's see. Easiest answer is you are right, and yes that's what I intended, except for your last question. <G>

Seriously, to answer the most important one, the ground bar's weren't installed in the panels when I took the picture, but are now, and the bonding screws are removed from the two basement panels. So, the panels themselves are grounded to the ground bar outside the house, but not tied to the neutrals. (Thanks to your advice earlier on in this post!! <G>)

Now, as for number of circuits, I am installing a Vantage Controls Lighting and Home Automation system in the house. It requires me to have 4 breakers for each 8 loads that I want to be able to control by the system. So, each "load" may only be 2 75 watt bulbs, but they will eat up a breaker. That is a LOT of seperate breakers, but very little load. Hence the reason for 2 40 space panels. Square-D doesn't make a MLO panel in their QO series, and the 200-amp main breaker panel was actually the cheaper way to go, and since it isn't doing any harm this way, I went with it.

Any other observation you think I should be thinking about or concerned with? I've appreciated your's and Mark's great help to me so far!!

I'm about to post a couple more questions on new subjects shortly. <G>
Alan

[Wgoodrich]

Sounds like you are well on your way.

Good Luck

Wg