Planning for a new sub-panel

[SnoFalls]

I'm in the process of getting an RV pad setup for my elders to use.

I've got a "pad" graveled in, and have a sewer drop there too.

This is all next to my shop building which has plenty of power being fed in. I'm not sure, but it might even have 3 phase (I'll post another thread for the electricians to guess about *that*).

This is a 2 story shop (24x50) where 900sq/ft of it is "upstairs" that I'll also be remodeling (it was office space, but I may live in during a house rebuild, yet revert back to "office").

I will bring in a electrical contractor at a point, but for a planning perspective does this sound reasonable all from one 200a panel?

downstairs
50a - RV plug
20a - fridge/(+small freezer)
20a- washer
50a - dryer
15a - lights/outlets for laundry/bath

upstairs
50a - stove
20a - fridge
20a - lights/outlets for "kitchen"
20a - lights/outlets for "great room" (either cubicles or living room)
15a - for 3/4 bath
20a - for "exec office" (aka bedroom #1)
20a - for "conf room" (aka bedroom #2)

Adding all that up comes to a total potential draw of 320a ...
The reality is that it wouldn't come close to pulling *all* that at once. But would I now be "maxed out" ... e.g. I'd like to run anothe 20a to the "great room" area since that might have 3 cubicles in it.

The plan is to also have a seperate 200a panel for the "shop" space, so the welders, table saws, etc are on another panel.

thoughts?

BTW, here's an example layout of the "upstairs"

The downstairs might look like this.

(those layouts have changed since I made those screenshots since plumbing will also be moving ... but it's an idea of the space)

 

[Kendall69]

My advice ALWAYS put in more than you need. Putting in a bigger panel now is a whole lot cheaper than adding something later.

Granted they may not ALL be on at once, but if you have just the three or four biggies on at once your at the max. ( Oven, compressor, dryer etc. a computer on, some lights, and maybe the RV with the Air on).

Separating the panels helps, but you still have to have the right power/wire size coming into the complex, in order to fire up the 200 amp plus the separate panel.

Also they have breakers that have two 15/20 amp breakers that take up only one breaker slot.

 

[Diesel-ME]

Sno,

The circuits are not additive in calculating the load. You will be fine with a 200Amp service. While you may not want to do a huge welding project while cooking Thanksgiving dinner (with all elements hot) and the RV AC cranking, you will be fine.

BTW, the dryer will probably be a 30Amp branch circuit and it's not uncommon, depending on the load requirement, for ranges to be 40Amp.

Adding several sub-panels is a great idea as it gets the load center closer to the branch circuits. With the price of copper being so high you will save $$ in both labor and materials to run shorter branch circuits to a conveniently located sub-panel.

Even with a shop (AC welders, compressors, etc) it's rare that you see a residential install with greater than 200Amp service. Besides, if you are worried about pushing it too far, what with the shop and RV, you could always go to gas for your dryer and range, etc.

For planning purposes you are on the right track.

~paul (not a master electrician)

 

[mjarrels]

Spent some time at SnoFalls... probably never be running the motorhome AC... maybe the heater?

mark

 

[ultrarunner]

All good points.

The loads are not cumulative.

Last year, at work, I installed a second x-ray unit. There was a question if adding the x-ray would require upgrading the transformer and Main Panel. This would have been a major expense making the project no longer feasible.

To alleviate everyone's concerns, we recorded the load actually used over a continuous 10-day period. Even though the Hospital has outlets everywhere and every piece of equipment has a dedicated circuit, the actual, real world load never exceeded 27% of the panel rating and averaged no more than 20%

If you have the option, you can also free-up some capacity by replacing your electric dryer and electric range with gas and using screw-in fluorescent lighting in your ceiling fixtures.

When my brother added on to his home, he was able to use his electric dryer 30 amp circuit for his new Air Conditioner by by replacing the electric dryer with gas. Saved a few dollars and the inspector was OK with it.

 

[hockeypuck]

I would put a 8 crkt 200 amp "pass through" panel in the garage (Square D) makes them.
http://ecatalog.squared.com/pubs/El...Single Phase Load Centers/1170BR9601R1003.pdf

Pass through is found on page 6

This panel would allow you to pass the full 200 amps to a "subpanel" somewhere else in the house. You could put your welding circuit and other high amperage loads (ie air conditioning condensors) in the pass through panel and put the house circuits on a main lug 200 amp panel somewhere else in the house. The other nice thing about using this pass through panel is you can then put a generator transfer switch after the pass through panel, but before the subpanel. That way you can eliminate the high amperage loads that may overload the generator.

 

[BobRip]

Sno,

The circuits are not additive in calculating the load. You will be fine with a 200Amp service. While you may not want to do a huge welding project while cooking Thanksgiving dinner (with all elements hot) and the RV AC cranking, you will be fine.

BTW, the dryer will probably be a 30Amp branch circuit and it's not uncommon, depending on the load requirement, for ranges to be 40Amp.

Adding several sub-panels is a great idea as it gets the load center closer to the branch circuits. With the price of copper being so high you will save $$ in both labor and materials to run shorter branch circuits to a conveniently located sub-panel.

Even with a shop (AC welders, compressors, etc) it's rare that you see a residential install with greater than 200Amp service. Besides, if you are worried about pushing it too far, what with the shop and RV, you could always go to gas for your dryer and range, etc.

For planning purposes you are on the right track.

~paul (not a master electrician)

I agree. Remember a 50 amp breaker does not mean that you are pulling 50 amps from it. Same with all of the other breakers. The breakers are there to protect the wire and not matched to the average running load. Also it is highly unlikely that all loads would be on at one time. Many a home gets by on 200 amps. Also, let's says you trip the 200 amp main breaker (highly unlikely). Just turn off a few loads until your needs drop. I don't like to undersize, but you are OK. I do recommend using florescent lighting throughout since it pays for itself both in longer bulb life and about 1/3 of the energy consumption.
I would put in a panel with plenty of spare breakers. This is what most people run out of. Sub panels (as mentioned above) are also very good. I have two main panels and two sub panels in my house.

 

[SnoFalls]

Thx for the replies ...

No gas option for this building (unless I installed a propane tank). I'm not really interested in going that route due to install cost and also since this building gets a cut on the power rate (e.g. power is relatively cheap).

Here's some pics of the existing power ... (click for bigger versions, and sry they're fuzzy, it's dark in there and the camera doesn't do too well on flash alone)

1) the buried lines coming in

2 left are power not sure about line on right (phone comes in another point ...)

2) The boxes inside of the feed.

bottom box is sealed and I'm guessing some sort of transformer
center box has 2 feeds from below, a common bus, and then a feed to upper boxes
upper left master switch goes up and over to existing 200a panel, upper right switch isn't feeding anything.

3) An example of why I'm fixing all this ...

One 12-2 in and about 8 going out of one 4x4 box!

The plan is to move the existing panel over to the right of the upper boxes (getting a feed from it's own master switch), and then extend the existing feed that goes up and over the door all the way back to the laundy/bath (that's the new panel I laid out above).

One thing I fogot in the new panel is circuits for ... I'd want to add 3 20a feeds for baseboard heaters.

So,

Does it appear I have enough power to supply 2 seperate 200a panels?

It sounds like the new 200a panel should handle what I'm proposing to put in there correct?

Thx all for the replies, it lets me have a reasonable plan before I bring in a contractor ...

 

[EddieWalker]

I'm curious why you are running so many 20amp lines? Lights and outlets for household items all run fine off 15amps. The outlets cost the same, but there is a significant difference in the price of 14/2 compared to 12/2 wire. There is also a big differnece in handling it and working with it. The only place I can think of in a house that need 20 amps would be your micorowave.

I'm not positive without checking, but I think your stove and dryer are both 30 amp lines. Are you putting in a HVAC system? If so, you will need 60 amps and 30amp lines for that. If no AC, you will still need to have power for your electrical heating system.

Does the RV need AC? I have a pad with a 50 amp and a 30 amp plug in that I can run at the same time. The 50 amp is for friends who come by who need to run there AC units. In the fall, winter and spring, the 30 amp line is plenty. Do you really need to pay for the wire to have 50 amps available?

Wire is what costs you all the money in your electrical. From what you have planned, you are wasting a bunch of money by oversizeing your lines. I don't think there are any safety issues running 20 amps to your lights and outlets, but then again, there might be. You can always put 15 amp circuts on 12/2 wire, but why spend the money on the larger wire?

Eddie

 

[Diesel-ME]

Thx for the replies ...

No gas option for this building (unless I installed a propane tank). I'm not really interested in going that route due to install cost and also since this building gets a cut on the power rate (e.g. power is relatively cheap).

3) An example of why I'm fixing all this ...
http://www.avalonforest.com/misc/shop-elec/wtf.jpg
One 12-2 in and about 8 going out of one 4x4 box!

One thing I fogot in the new panel is circuits for ... I'd want to add 3 20a feeds for baseboard heaters.

So,

Does it appear I have enough power to supply 2 seperate 200a panels?

It sounds like the new 200a panel should handle what I'm proposing to put in there correct?

Thx all for the replies, it lets me have a reasonable plan before I bring in a contractor ...

Wow - that junction box is a fire waiting to happen!!!

The 3 electric heaters are the one item that has the potential to draw close to the rated amperage (depending on the length of each baseboard).

Eddie makes a good point about 20-Amp circuits. However, it's becoming common for electrical contractors to only buy and install 12AWG wire, even when protected by 15Amp breakers. Keeps their inventory simple. But 14AGW wire is way easier to work with when, for example, you are dealing with lights and switches. You can use 15Amp protection with 12AWG wire but can not use 20Amp breakers with 14AWG wire.

Properly protected (breakers) I still think that you'll be OK with one 200Amp main.

~paul (still not a master electrician)

 

[ultrarunner]

The city required load calcs for each individual circuit and for the panel on the last home I wired. They had a formula for calculating assumed load based on the size of the panel, size of the house and number of circuits. Basically, it worked out to the more circuits per square foot of house, the less the assumed load on each individual circuit.

The city also required outlets to be on 12 ga, 20 amp circuits. Garbage Disposal, Dishwasher and Microwave each required individual, dedicated circuits.

14 ga was only allowed to service 15 amp lighting circuits with the exception that you could have a wall clock outlet on the lighting circuit.

In my area, most of the electricians don't bother with 14 ga anymore.

 

[tommu56]

SnoFalls
Is the power three phase?
if it is it might be a current transformer cabinet

Is the meter (on the outside) centered on the big box with the seals on it?
if so it looks like they daisy chained power in to building and back out to some were else. It is sort of confusing with the wires coming out of left side of lower box in spliced trough and back in to lower box. some better pictures might help

I would open sealed box and see whats in side or call the electric co and have them open it and explain.

tommu56

 

[BobRip]

The city required load calcs for each individual circuit and for the panel on the last home I wired. They had a formula for calculating assumed load based on the size of the panel, size of the house and number of circuits. Basically, it worked out to the more circuits per square foot of house, the less the assumed load on each individual circuit.

The city also required outlets to be on 12 ga, 20 amp circuits. Garbage Disposal, Dishwasher and Microwave each required individual, dedicated circuits.

14 ga was only allowed to service 15 amp lighting circuits with the exception that you could have a wall clock outlet on the lighting circuit.

In my area, most of the electricians don't bother with 14 ga anymore.

I would stick with 20 amp 12 guage wire for all outlets. This is somewhat overkill, but it keeps from tripping breakers if you have some light loads and then plug in a large load (vacuum cleaner, saw, etc). But for lighting 15 amp 14 guage is fine. Save some money on the wiring and make the wiring easier.

This is getting complicated and I think you need to get an electrician involved. It would be worth paying him to look at what you have and make suggestions even if you do most of the work. Pay him for a day and have him help you get started. IMHO

 

[SnoFalls]

SnoFalls
Is the power three phase?
if it is it might be a current transformer cabinet

honestly I dunno ... I suspect it might be tho.

Is the meter (on the outside) centered on the big box with the seals on it?

it's not centered on it, but a conduit runs from the big box to the meter.

if so it looks like they daisy chained power in to building and back out to some were else. It is sort of confusing with the wires coming out of left side of lower box in spliced trough and back in to lower box. some better pictures might help

not daisy chained ... I can see both individual lines running down the pole to underground. Our house is fed from a seperate pole (via above ground line)

I would open sealed box and see whats in side or call the electric co and have them open it and explain.
tommu56

This is getting complicated and I think you need to get an electrician involved. It would be worth paying him to look at what you have and make suggestions even if you do most of the work. Pay him for a day and have him help you get started. IMHO

yes, the day is coming where a pro is coming out ...

thx all for the feedback so far.

 

[buckeyefarmer]

Well said.

With the load described 200Amp is plenty, breaker space is what is usually lacking. My dad has more load than that in his house which is still fed with a 60Amp main, which is what was used 50 yrs ago. I don't even think the lights dim when he fires up the welder.
I prefer lights on 15Amp circuits and outlets on 20 amp circuits. The code allows mixing them on 15 amp, but the cost difference in a couple rolls of wire is really insignificant to the advantange. Also remember by code there is a limit to the number of outlets per circuit which you have to calculate when laying out the circuits. Start with section 210 of the NEC.

As for the box with 2 wires in and 8 out, all boxes have a capacity. Most plastic ones are stamped with the wire count. See section 370-16 of the NEC for details. That box might be legal, depending on the depth. If not, you could put an extension on the box to make it bigger.

Looking at the pics, it's hard to tell whats going on. By the size of the bottom box, probably just a big junction box, doesn't look nearly big enough to be a transformer. If it was a transformer, there would be a nameplate on it with all the info. I assume the outside meter picture is right behind the horizonal trough you have open. The wiring size doesn't look big enough to be 200A. Look at the wire and see if you see the size stamped on it.
Do wires exit the back in the center of the trough? hard to tell from the pic, thought maybe that was where it went to the meter and back. Notice from the outside meter pic there is no conduit, so it is feed from inside. If not here, then in the big box on the bottom feeds in and out of the meter.

 

[buckeyefarmer]

oops, should have read the last post......

Nothing in the pics make me think it is 3 phase. It would be very unusual for a building like this to have 3 phase supply, although I could be wrong.

I suspect the reason the bottom box is sealed, is because it feeds the meter. They definitely don't like you feeding circuits from before the meter.

Don't be surprised if the electrician can't help with the load calculations, they're not design engineers. Most however, know the proper number of outlets etc. per circuit because they put them in all the time.

 

[schmism]

you might find this of some help (i shure did)

Detached Garahe - show all

Im fairly shure my utility is asshatish and doesnt allow multi tap meter bases so ill have to dig up one of those key tap boxes....