Talking to a guy in the electrical supply isle at Lowes a couple days ago. Anyway, somehow he got on the topic that he and his co-workers like to put in multiple subpanels within new homes. He said not only did it offer a closer location to reset a breaker, but that it saved electricity because the heavier gauge sub-panel wire loses less than multiple smaller gauge wires.
I was on lunch, so didn’t have time to expand the idea and don’t know if this guy was an electrician, contractor, or what. But I’ll be darned it I didn’t run into the same idea YESTERDAY while perusing an old FHB at lunch (issue 154).
Subpanels and heavy gauge wires cost $$. How much electrical savings are we talking about? 5 cents per year, $50, what? Does anyone have numbers on this to calculate what you’re gaining by putting subpanels in instead of just running the individual circuits from the main panel??
jt8
It’s better to light a candle than to curse the darkness. –Chinese proverb
Replies
Well I looked at that article and he is really putting the emphasis on voltage drop, which can affect the operation of the equipment, more than cost savings.
And he is talking about large home (4000 sq ft).
I don't want to spend the energy doing any calculations, but even at 12 cents/kwh it would take a long long time to pay for it in terms of strict power loss.
Maybe TRUE if ya do 6 guage or so for the entire house!
Bill,
Assuming an average run of 100' with out SPs; 25' with; and an average run of 50' per SP.
Ohms per 200' 14ga = .505Ohms per 50' 14ga = .2525Ohms per 100' 0ga = 0.063Power usage = 10 amp/hours/day (1.1-1.2 KW)
Loss per 200' 14ga (IxIxR) = 50.5WLoss per 50' 14ga = 25.25WLoss per 100' 0ga = 6.25W
50.5W - 31.5W = 19W saved per day (I'm not doubling that in cooling periods)
6.9KW saved per year at 1KW/day use
To find your savings, take your daily power usage in KWHs (ie; 4.3), square it (ie; 18.49), and multiply that times 6.9KW (ie; 128KW) to get your savings/annum.
At $.12/KW, that's $15/annum (at 4.3KWH/day)
Assuming it costs $35,000 over ten years to replace all electrical equipment and voltage drop cuts 1% off it's life, the annual equipment savings is $35.
SamT
perhaps if it was a 3phase factory and we want to worry about voltage drop and the affect it has on the equipment or we want to limit wire sizes...
John,
The energy savings is real, but incidental; it doesn't amount to much relative to the energy used in a home. I don't have the time to do the calculation, either.
Most of the time, my decision to install a subpanel is driven by necessity--either the house has more than 42 circuits (the max allowed in a panel), or because distances would lead to unacceptable voltage drop. On the former point, it's amazing how quickly a panel fills up, and you always want to leave a few empty spaces (two full-size spaces/4 circuits is what usually I leave open) for future addition of circuits.
Secondary considerations are homeowner convenience (if the distance from the far end of the house to the main panel is considerable), safety (adding a sub in a home woodworking shop is cool 'cuz all power to the machinery can be locked off), and future expansion (having a subpanel on the top floor with an empty conduit running into the attic can make it a relative breeze to add a circuit in the future).
Also, I think there is an advantage in terms of labor saved in installation (i.e., not installing longer runs of branch circuit cable). Running one feeder (for instance, 4-3 wg NM-B cable for 70 amps at 240V or 6-3 for 55 apms at 240v) between a subpanel and main panel is a lot less effort than running 20 or more 12-2s another 80 feet back to the main panel. Granted, a 4-3 cable is more work to wrestle with than a 12-2, but if you have the tools and know the tricks, it's no big deal. I recenty ran a 100 amp/240v feeder (keep in mind that that's 200 amps at 120V) to a sub because it was a big house, the main panel was getting full, and the sub was supplying the kitchen circuits. Working the #2 was a chore.
Glad you liked the article. That's a pretty high-class lunch room (at your office, I'm assuming), what with FHB back issues lying around!
Cliff
Cliff, that was a good article. I'm comfortable wiring lights, recepticles, and such, but leave the panel work to electricians. But from a design point of view, that gives me something to think about.
And the light bulb really went off when you mentioned setting up a subpanel for a kitchen. With 3 recepticle circuits, 1 light, oven, cooktop, garbage disposal, chest freezer, etc... If all of that could be run out of a subpanel, that would make life a lot easier. Shoot, if I was running two 8ga lines for the oven and cooktop, the savings on those two being shortened might pay for the subpanel wire.
But I think you suggested taking the fridge circuit back to the main panel to avoid flickering? Which probably means the freezer circuit would need to go back as well? If you had your choice, would you run the electric oven and cooktop from a sub, or take it directly to the main panel?
If the associated flickering caused by the fridge compressor kicking on is just a nuissance (and won't harm the other items on the subpanel), I wonder if it wouldn't be a reasonable setup to simply run the light circuit back to the main panel and let all the big dogs come out of the subpanel.
Most of the time, my decision to install a subpanel is driven by necessity--either the house has more than 42 circuits (the max allowed in a panel), or because distances would lead to unacceptable voltage drop. On the former point, it's amazing how quickly a panel fills up, and you always want to leave a few empty spaces (two full-size spaces/4 circuits is what usually I leave open) for future addition of circuits.
A friend and I joke that you can never have too many circuits. He is threatening to put an outlet in every 12" when he builds his new house ;)
Most of the subpanels I've encountered were installed due to overcrowding of the main panel (and are often within a couple feet of the main panel). Or was put in for something big (like AC unit). Sister & BIL's house has a subpanel in their attic (basically 3 floors up from the main panel), which I thought was a good idea since it is powering attic and 2nd floor circuits.
Working the #2 was a chore.
I've never messed with stuff that thick. I thought the 8 was pretty cumbersome. By the time you get to #2, it must be like trying to bend a grounding rod. ;)
Glad you liked the article. That's a pretty high-class lunch room (at your office, I'm assuming), what with FHB back issues lying around!
I had pulled it out of my 'archive'. Grabed it to read Gary Katz bookshelf article, and your subpanel article caught my eye.jt8
It's better to light a candle than to curse the darkness. --Chinese proverb
Forgot to mention:
dude at Lowes had mentioned setting up a subpanel for a master bedroom/bath. He was saying between the hottub circuit, towel warmer, various recepticles, lights, etc, it made sense for them.
I didn't know if this was logical or not (not being an electrician), but liked Cliff's kitchen suggestion.
jt8
It's better to light a candle than to curse the darkness. --Chinese proverb
Edited 5/13/2005 2:03 pm ET by JohnT8
setting up a subpanel
I like the idea of a kitchen SP; the one-per-level makes sense, too.
(It would really make sense in my attic, what with the power demands of an air handler, and needing by code a 15amp DPCV near by, and a switched light.)
Now, the only hiccup that occurs to me is where are all these SP going? Need 30" wide, 36" deep, and not more than 66" to top of panel to get a permit here in town. In a basement, in an attic, that's not so tough--but, I'm not coming up with a good kitchen location that would "pass." That could be 'cause it's Friday, and I'm all "imagined" out, too <g>.Occupational hazard of my occupation not being around (sorry Bubba)
I just finished my second floor. I ran a sub panel to the floor. One wire to fish to the main. It was much easer then running all the circuits to the main."A friend and I joke that you can never have too many circuits. He is threatening to put an outlet in every 12" when he builds his new house".I put the sockets every 4 feet. Looks a little over kill when you're done, but after my kids moved up stairs the, furnishings covered half of them.
But the extra cost of the sub panels and the thicker wire, extra labor, you are losing money. beside if he knew so much why is he working at Lowes for $6 a hour instead of electrician at $18 a hour.
I know everything there is about concrete but cannot finish concrete at all. My dad a welding engineer knew everything about welding but could not weld. Those who can, do, those who cant, teach.
But the extra cost of the sub panels and the thicker wire, extra labor, you are losing money. beside if he knew so much why is he working at Lowes for $6 a hour instead of electrician at $18 a hour.
He wasn't working at Lowes, he was shopping at Lowes. I don't know if he was an electrician or a contractor or what.
Brown, you don't think it would be less labor to run one thick wire to a subpanel rather than run several smaller wires back to the main panel?
jt8
It's better to light a candle than to curse the darkness. --Chinese proverb
John,
You've asked some good questions.
If you had your choice, would you run the electric oven and cooktop from a sub, or take it directly to the main panel?
I'd feed 'em from the sub, as long as the sub is fed with enough power. By that, I mean I'd want the sub fed with 1.5 times the amps of the major appliances fed from it. My thinking being, if the cooktop and oven both coincidentally cycle on at the same time, I don't want those loads to consume all the power at the sub. So with a 30 amp cooktop and a 40 amp oven, a 100 amp sub outght to do it.
If the associated flickering caused by the fridge compressor kicking on is just a nuissance (and won't harm the other items on the subpanel), I wonder if it wouldn't be a reasonable setup to simply run the light circuit back to the main panel and let all the big dogs come out of the subpanel.
If you're talking about a commercial subzero unit, the compressor startup current can be enough to cause a little flicker. I'd run the refrig circuit from the main panel if that an issue--it depends on how fussy the client is.
On a recent remodel/addition, the two AC compressor units were far away from the main panel and closer to the subpanel. I powered them both from the mail panel; an AC compressor can draw a startup current that's several times its running current. Running that from a 100 amp sub would have lead to serious flicker in lights fed from the sub.
Yea, the #2 in the NM cable is stranded coarser than #2 free conductor (for use in conduit). It's a PITA to bend. Using the holes in the handles of two crescent wrenches works pretty good.
Cheers,
Cliff
I get the impression that the consensus among the majority of posters here believe that garages and workshops , and very large homes are the most "bonafide" regions for receiving subpanels.
I agree that such areas often render the need for subpanels...my workshop has it's own subpanel.... I've witnessed many large homes that do have subpanels running up to upper level floors...but, I think perhaps many of you are overlooking another valid use for subpanel placement......the remodeling field.
I have remodeled kitchens and bathrooms, and sometimes find that it is much simpler to run a subpanel and re-wire that room altogether new. Many of the homes I work in have very old, antiquated stuff...such as ITE Pushmatic breakers. Last house I remodeled, had a 100 amp breaker box....practically 2/3rds of the entire house had been "plugged" into one 20 amp breaker.....I'm talking, refrigerator, furnace, bathroom, kitchen, and part of the basement.
Sure, we "cleaned" up a lot of the old system by seperating into several, seperate branch circuits. But due to original service entry location, it was much more feasible to install a subpanel close by, than to run new entrance cable and change out existing box into a 200 amp box. We were able to utilize an existing 50 amp breaker from the original box that had been wired in for a kitchen stove ( but never actually used...owners had a gas fired stove instead), and divert that unused amperage into a new subpanel, and then run several branch circuits off of that. I felt better knowing that the new kitchen had all new wiring, complete with new breakers ( Cutler Hammer) , and that the owner could easily identify each kitchen circuit as depicted on the new subpanel ledger.
A lot of old panel boxes have had wiring changed around until you have no idea as to what breaker controls what. Old boxes are sometimes sooo "over extended"...that is to say that you will find practically all duplex (slim-line) breakers occupying space and the bus bars are at overflowing capacity to hold all the grounds and neutral legs.....I've seen many a box with more than one ground wire or neutral sharing the same lug....which is definately verboten.
Soooo, Joe Remodeler is asked to do a simple renovation that requires a few new circuits for lighting and such...but after going down to basement to inspect, finds wiring to be a bit on the shoddy side....maybe at times violating codes, other times, simply suspect. Homeowner doesn't want entire new service...not part of the planned budget....Joe doesn't want to open too big a can of warms ...is safer for Joe to add a subpanel and be responsible for his "new work"...rather than take responsibility for entire house wiring.
Yes, Joe will rectify visible code violations....but unless Owner is willing to allow (PAY) Joe for tracking down and inspecting the entire original wiring system, it's better for him to fix what he can thats in plain sight, then add a new subpanel and wire his new work accordingly, and feel good knowing that at least his work is up to snuff.
For the record, West Virginia is one of those states where electrical work can be done by the home owner himself...he does not need to be licensed...and very few times such work ever gets inspected by a State or City BI. Now, to become a State licensed sparky is another matter...tests are very hard and grading scale is tough!
When dealing with home owners and their (residential) wiring problems, professional remodelers have to walk a "fine" line in this arena!
Just my 2 cents.
Davo
I agree that sub-panels often make sense from a convenience point of view. They allow a homeowner/contractor team to selectively upgrade the house in terms of electrical service, w/o having to resort to widespread demo to run the wires. Fishing one wire goes faster than fishing 10...Furthermore, a good argument can be made for sub-panels in areas of the house where you have concentrated loads, like the kitchen, or the utility room. Panels don't cost much, and the can make everyone's life easier by putting the control over loads close to their point of use.Sub-panels also simplify life by reducing the spaghetti effect of 10 billion romex wires snaking into the basement, through walls, floors, ceilings, etc. like wild salmon swimming upstream. Plus, if the supply wire is oversized somewhat, you can later easily attach new, presently unanticipated loads.Having said all that, there are some downsides, such as the confusion where to find the things, if there are a lot of them. Even if they know where the interior designer/electrician hid the panels, it will take most non-engineer homeowners probably some time to figure out what each breaker does (despite being (hopefully) labeled). I have a friend in Germany that has to keep calling the former owner/renovator of her house to figure out where he hid the various utility shutoffs, etc.Our three-story Mansard has one sub-panel on the third floor, which feeds the third, and most of the second floor. Along the way, it provides power to a 3-ton AH, a air cleaner, etc. Having the panel up there saved us a lot of 12/3 wiring (outlets) as well as 14/3 wiring (lights). The less wire that snakes through the walls, the lower our chances of inadvertantly hitting it. The basment main panels feed the rest of the house. As these panels were installed close to the kitchen and shop, there was no point in having separate sub-panels for either.The basement panels are hidden behind a foldaway door, the third-floor sub-panel is at arm level right in the hallway. A interior designer (if we had one) would probably howl in protest, but this house is an excercise of function over form... Yet, despite having to work for an engineer, our wonderful contractor and his dedicated band of merry subs have done a fantastic job of rebuilding our home.
Another safety/convenience principle is that each floor should have its own subpanel. That way you don't have to climb stairs in the dark.
-- J.S.
The simple answer is that any savings are likely to be vanishingly small. There are a few situations where savings would be greater.
Most circuits within a house are not anything close to fully loaded. With the entire family home I have taken readings on a huge house that had a 400A service. The entire load pulled by the house was under 30A most of the time.
If there were circuits which ran at something close to maximum load for 12 or so hours a day upsizing that circuits conductors above and beyond the standard voltage drop requirements would make some sense. In commercial settings it can make economic sense in terms of savings by reducing voltage drop.
In most residential settings there are precious few circuits which fall into this category. Perhaps a grow room, running 12 hours a day, would fit a circuit which would benefit but no others come immediately to mind. There are savings in reducing voltage drop in any circuit but the return on investment is typically somewhere between glacially slow, over 50 years, and nonexistent.
In terms of very large and strung out homes there can be some limited savings in labor by installing a subpanel. It is easier to run a single feed to a subpanel than dozens of individual cables the same distance to a distant main panel. Particularly if the feeder can be run directly in conduit under a slab or other direct route. This is somewhat offset by the additional equipment cost of the subpanel and feeder. Given a sufficiently strung out house it can make some sense. Careful calculation will determine the break-even point but either way I would not expect huge differences in the cost of either installation.
IMHO the most persuasive argument for subpanels comes down to two points: Convenience in handling loads that are expected to trip more often and reducing the cost of future additions.
The most frequent circuits likely to trip regularly and need resetting are shop or garage circuit and exterior circuits used for lawn care. A subpanel at or near the garage, shop or back door can save time, trouble and the walking in of sawdust or lawn clippings. An amenity worth the additional cost to some people. Less so to others.
Also a well placed subpanel, particularly if empty conduits or chases are installed to make access into the subpanel easier, can make adding circuits a lot easier and greatly ease the electrical side of planned additions. This can offer some small savings to the construction cost of the combined house and addition.
Subpanels have a roll and discreetly applied they offer some small savings. The widespread and indiscriminantly use of subpanels, outside of careful analysis, is more a matter of convenience than economics. That the people selling the equipment and those who make money installing it would promote the practice should surprise no one.