Another sub panel thread!

[EMFab]

Hello Everyone!
This is my first post, and I hope it will not be my last. I have been reading this forum for a week or so now and the wealth of information is incredible! I need to run some new electrical in my attached garage, and I have learned so much on here. I still have a few questions, some of which are "stupid" questions because I want to understand what I am doing and why.
We have a small 3 axis CNC router coming in the next two weeks, and its temporary home is our current wood shop that is an attached two car garage. I have contacted 8 Licensed Electricians, all have either blown me off, they don't want to provide a quote, or they can't get to me till the end of August. Keep in mind that I have been searching for almost 8 full weeks now, and I must have our new machine connected before the end of August.
I was really hoping that some one you on here can help me understand what I need to do and why. The machines electrical requires are really simple; the spindle needs 220/240V 40A, the vacuum system needs 220/240V 30A, the dust collection needs 220/240V 30A, and of course I need a 110/120V 15A for the computer.
Today, we went to a big box store and bought a Square D 125A 12 space 24 circuit panel, (1) double pole 40A breaker, (2) double pole 30A breaker, and the panel came with a couple of single pole 20A breakers. So that's a start!
Through reading, I have found out that I can put a 125amp breaker in my 200amp main panel. But what I don't understand is this...if I put a 125amp double pole breaker in my main panel, won't the main panel exceed 200amps and trip the main?
I have a series of other questions as well, but I thought I could start off with a really simple question for a new person. Thank you so much for the help!

 

[Zeke]

The question you ask will have answers in the gray area. It's not a simple as adding up the total amount of breaker capacity and trying to plug it in to the main. That's even true for branch circuits. On branch circuits you will have 10 or so on the average outlets on a 20 amp breaker. It is assumed you won't plug in 5 oil heaters on that circuit. But, you can move one around to different outlets and still have some capacity left over for a TV, computer and/or a couple of floor lamps.

The kitchen and baths are different and require dedicated circuits such as your machine setup. In the house it is assumed that it will be hard to overload the dedicated circuits unless you plug in an electric frying pan or 2 plus a couple of other heavy draw appliances. IOW, the circuits are designed to be convenient not to designed to have a large draw on every outlet.

Then there's the single circuits like the garbage disposer, dishwasher, washing machine and more. These circuits are rated at 20 A but none will draw that much. So, what I'm pointing out is that there are way more circuits than what the draw will be on the main.

You have to survey your panel and see what's there. If you have a couple of 30's or 40's in there to run the house A/C and maybe an electric water heater, then you might very well overload the main with your 125 A breaker.

But now study the running draw of your circuits to the router. You've added up the maximum potential of the circuits to determine the need for a 125 A breaker to power your sub panel. I'd say you can get by with a 100 or less. That is unless you constantly power up the different machines simultaneously. That is not likely if you set up your vacuum to come on first, the dust collection 2nd and the router when ready to make your part. Do run a clean circuit to the computer with an isolated ground.

 

[Eriehunter]

Typically the 125a breaker you are looking for will not stab into your panel, they are a larger frame size. most 200 amp panels will accept a 100 amp max breaker. "Typically" there may be exceptions or a kit that may allow something to be retrofitted.

 

[EMFab]

Zeke, thank you very much for the reply. I'm pretty sure I understand what your saying. The vacuum will be powered first, then spindle and then the dust collection. So there will not be a 100amp draw simultaneously.

You're also correct and I do understand that the computer needs to be on a dedicated circuit. The CNC manufacture actually recommends that the spindle, vac an computer to all be dedicated circuits.

The house does have AC/gas packs, and an electric water heater, etc. I need to get a meter and see what my amperage is when these appliances start, and then run (to know what the amps drop to). Then total the amperage if the appliances started all at once, and I started the "appliances" that are on the sub panel. Correct?

 

[EMFab]

Thank you Eriehunter, I haven't even looked for breakers to fit my main panel yet.

 

[Mustang51js]

You need to find out what the running load would be when the machine is on,you may find out you are only drawing 50 amps or so after the machine is started. Your water heater is prob your other biggest draw, but at same time it will draw less because the water is heated up allready. Maybe think about running the 40 amp line separate from the sub panel this way you can just hook up a 90 amp sub panel to save on wire costs

 

[larry_g]

So here again location is important. One of us may be next door and could lend a hand.

Can you post up a manual for the machine your getting. Those are some high horse power draws for a 'small' cnc machine. I would contact the builder and have them supply the FLA currents of the motors that you are going to be running. The more detailed information you put out here will get you the best answers.

lg
no neat sig line

 

[Bib Overalls]

I agree with Zeke on the 100 amp breaker at the main panel.

 

[Norcal]

When adding additional loads doing load calculations is a must, in addition the panel may not be listed for a 125A breaker, the label attached to the panel needs to be read very carefully to see if it is allowed, 100A should be fine & a whole lot cheaper too.

 

[Zeke]

Zeke, thank you very much for the reply. I'm pretty sure I understand what your saying. The vacuum will be powered first, then spindle and then the dust collection. So there will not be a 100amp draw simultaneously.

You're also correct and I do understand that the computer needs to be on a dedicated circuit. The CNC manufacture actually recommends that the spindle, vac an computer to all be dedicated circuits.

The house does have AC/gas packs, and an electric water heater, etc. I need to get a meter and see what my amperage is when these appliances start, and then run (to know what the amps drop to). Then total the amperage if the appliances started all at once, and I started the "appliances" that are on the sub panel. Correct?

I said 'clean' circuit, not dedicated. With your machines starting you will have some fluctuations and a lot of electrical noise. I think today's computers are better designed to accommodate electrical abnormalities but 'safe than sorry'.

Yes to your last question, it's always good to know the limits of your total usage. With this new 100 A breaker you could pop the main if the A/C is running, the water heater is running, people in the house using hair dyers and the microwave and you're out in the garage making parts.

Since you have gas, you could consider converting your water heater over and have that bit extra.

 

[EMFab]

Thank you all very much! I'll try to work on getting an average load calculation over the next couple of days. I'm so swamped with work right now, I'll have to do this at night/time permits. I've also updated my location in case someone was local and wanted to help (I'm south of Charlotte, NC in Monroe).

I also attached a couple of pictures of the main panel. Of course nothing is really labeled, so I guess I'll do that as well.

 

[EMFab]

There really isn't much here in the box.
The left side has: Right side has:
30A double pole 15A single pole
30A double pole 15A single pole
50A double pole 15A single pole
15A single pole 20A single pole
15A single pole 20A single pole
30A double pole 20A single pole

Our house is on the average side I guess, 1400 sq ft. 3 bedroom, 2 full baths. Nothing fancy, no jacuzzi bath tub, hot tub, etc. Just a plain old home from 1989. There are no extra refrigerators, or deep freezers. No pools, or any other sub panels. Shoot, we don't even have an attic fan!

 

[Mustang51js]

You could just run all the branch circuits right to the main panel and skip the subpanel

 

[theoldwizard1]

...if I put a 125amp double pole breaker in my main panel, won't the main panel exceed 200amps and trip the main?

In theory, yes. But, it is high unlikely that even starting surges will cause this to happen, because they won't happen at the same time.

The house does have AC/gas packs, and an electric water heater, etc. I need to get a meter and see what my amperage is when these appliances start, and then run (to know what the amps drop to). Then total the amperage if the appliances started all at once, and I started the "appliances" that are on the sub panel. Correct?

Again, in theory, yes. Most ampmeters (especially the clamp on style) will not measure a starting surge because it is so short.

Your big loads are the water heater and the AC (no electric stove or clothes dryer ?) Get them to start (run the hot water, crank the thermostat temp down to 60F) then start up all of your new equipment. Finally, put your "amp clamp" on each leg of the feed to your main panel. I'll bet it is well below 200A. If you feel it is "close", temporarily turn off one of the heavy load (water heater) while you are running the CNC.

You're also correct and I do understand that the computer needs to be on a dedicated circuit. The CNC manufacture actually recommends that the spindle, vac an computer to all be dedicated circuits.

Buy a small UPS for the computer and other electronic equipment related to your CNC.

 

[theoldwizard1]

You could just run all the branch circuits right to the main panel and skip the subpanel

This does nothing to resolve the OP's issue (main breaker overload),

 

[Mustang51js]

We don't even know if it's overloaded yet

 

[Stuff]

EMFab - Can you get amperage specs off of the devices themselves to see what they really draw?

 

[EMFab]

EMFab - Can you get amperage specs off of the devices themselves to see what they really draw?

Yes I will, I didn't have the opportunity "after work" due to the rain. Hopefully the cheapo ammeter I own will be accurate enough.

Again everyone, thank you for the help! I didn't even know what a UPS was other than United Parcel Service. I appreciate the education! I'm also waiting on some specifications from the CNC manufacturer. The machine is pretty small compared to what I am use to using. The table size is only 4'x8'.

I'll do my best to get a reading on all my circuits theough out the day tomorrow.

 

[Charles (in GA)]

Please don't tell me your panel is mounted horizontally.......... I hope the pic is sidways........

 

[larry_g]

Please don't tell me your panel is mounted horizontally.......... I hope the pic is sidways........

Look at the dust man...

lg
no neat sig line

 

[EMFab]

Please don't tell me your panel is mounted horizontally.......... I hope the pic is sidways........

Picture is sideways. The panel is mounted vertically. Why??

 

[EMFab]

Look at the dust man...

lg
no neat sig line

What about the "dust"? This typically happens over the course of 8 months. Summer has started and grass/debris does get behind the face plate even though there are hardly any openings.

I understand that dust accumulation does not allow breakers to trip, but it's not helping the this thread.

 

[sberry]

More nearly obsessive worry about overload. this house wont trip a 100 if you tried.

 

[larry_g]

What about the "dust"? .

The dust will accumulate on the BOTTOM, not on the side. If Charles had look close he could have figured it out. No offence meant, we all have a bit of detritus in the bottom of things.

lg
no neat sig line

 

[EMFab]

The dust will accumulate on the BOTTOM, not on the side. If Charles had look close he could have figured it out. No offence meant, we all have a bit of detritus in the bottom of things.

lg
no neat sig line

Oh! No offense taken! I a little curious as to how does grass get in there so "easily". Gezzz, the only comment I would take offense to is...well, I'm not sure. I'll have to think about it! Too any years in construction, my feelings never get hurt.

Just to keep you all posted on my progress, I received some bad family news and had to leave town last night. Just got to NJ around 11am today. I'll have to be home on the 11th, but I'm not sure when I'll be leaving.

 

[dledinger]

Again, in theory, yes. Most ampmeters (especially the clamp on style) will not measure a starting surge because it is so short.

What is an ampmeter?