Electric Power size needed for new shop, questions

[Ian Parish]

I have talked to 3+ electricians now and I am not sure of all my options to power my new shop. The work will be done by or with the help of a licensed Electrician. I have just been given a bunch of options. The shop is 2000 sq shop, with a 950 sq foot storage/attic/kids play room in the rafters.

I have a 3 inch plastic electric conduit running 160 feet from my existing house meter to the exterior wall of the new shop. The existing house meter is 225 amp panel with 2 100 amp breakers in it for 2 panels in my house.

In the shop I will have 5 dedicated 220 volts outlets for tools, two 50 amp, 2 30 amp, 1 20 amp. Plus I will have lots of lights and 110 volt plugs. I will have a panel in the utility room about 30 feet from the entrance of the wire into the shop.

Here are the option I have been given.

1)Upgrade the meter panel to 300 or 400 amps and add a new either 125 or 200 map service to the new shop. This is an expensive option and 200 amp service to the shop seems like overkill.

2) Put a 125 amp breaker in the main panel and add an sub panel next to the meter panel and run the shop and the house basement on the 125 amp breaker to a sub panel. This option seems like it would work but I run the risk of popping the 125 amp breaker and shutting down the basement and the shop.

One electrician said 60 amp service to the shop was just fine. I had 50 amp service to my previous shop, but it was 800 sq feet.

I think I am deceiding on 100 or 125 amp service to the shop. Is this overkill? With a 24 spot panel. What size and type of wire should I pull through the 3 inch conduit. SER or some type of single strand. Can I pull SER through a 3 inch pipe or will this be a real pain?

Opinion of my options are greatly appreciated.
Thanks in advance,
Ian

[Gene Howe]

IMO, 200 amp to the shop is not overkill.
With the proper lubricant you can pull any gauge and wire configuration you will need to serve a 200 amp box.

[Rod Sheridan]

Ian, you need to list your machinery along with it's consumption and which machnes will be used at the same time.

For example if you are going to use your cyclone and one machine, pick the largest machine and lump them as one load.

Are you going to be running lighting, HVAC and a compressor at the same time?

My shop, which doesn't have lighting fed from the shop panel, is a 35 ampere circuit to the shop panel.

I have a 1.5 HP cyclone, and a couple of 4 HP combination machines, only one of which runs at one time. The 35A feeder is fine for that.

Remember aside from compressors, cyclones and HVAC units, shop machinery runs as an intermittent duty cycle, with typically much less than full load current.

Regards, Rod.

[Ian Parish]

Ian, you need to list your machinery along with it's consumption and which machines will be used at the same time.

Regards, Rod.

My compressor 20 amp and my Plasma cutter 50 amp running at the same time are my two biggest machines. I also have a Millermatic 230 welder which can use a 30 amp circuit. But in a one man shop not much runs all at once.

My wood shop side is lower power, 1.5 hp HF DC and a 110v Jet are the machines that will run at the same time, or a 110v table saw, or 110v drill press. I may upgrade to a bigger DC in the (near) future.

The shop has HVAC in the form of an attic furnace, or a big gas hanging shop heater.

Thanks,
Ian
p.s. I may end up with a few new tools now that I have more space.

[Philip Rodriquez]

The key is how many tools you'll be running at the same time. Based on your equipment, you'll be fine with a 100 amp service.

[Roger Frazee]

Hello Ian

Your set up is very common. Detached shop with a cl 200 meter main as the service equipment for your home. Any service less than 226 amps is considered a cl 200 meter base.

You have mentioned working with an electrician so I'll just give you my options based on what you have described.

Option #1

Look at your meter main where the two 100 amp breakers are located & see if the distribution busses have feed thru lugs at the bottom. If so you can connect to those with your shop feeder. Now if the panel has feed thru lugs or can have feed thru lugs installed you can supply the shop as much as the service to your home without sacrifice to the power demand the home uses. In your case this will save you the cost of a breaker at the house panel.

What you will be using code wise is called the unlimited tap rule. So if running 100 amp wire off those lugs you will need overcurrent protection for the feeder to the shop of 100 amps or less. This protection can be in form of a 100 amp main breaker panel.

But one thing to remember and your electrician may know this is that a service rated disconnect must be located at the nearest point of entrance of the feeder either inside or outside to your shop.

You mention that the feeder enters the shop 30 feet from where your locating the panel. So one of two things have to happen ... your going to have to locate a disconnect where the feeder enters the shop or get an exception from the inspector to allow you to use a main breaker in the shop panel located 30 feet away from where the feeder enters the shop to satisfy the disconnect requirement.

In my area that exception ain't going to happen and we would do one of two things. We would place a properly rated disconnect at the feeder entrance with overcurrent protection for the chosen feeder size and then install a main lug only panel 30 feet after that.

Or we would install a manual service rated disconnect without overcurrent protection and a main breaker panel 30 feet from that disconnect.

The idea is to comply with code to satisfy the disconnect requirement and to comply with the unlimited tap rule which says you must have overcurrent protection for the shop feeder located at the termination point of the feeder. The termination point being either the disconnect location or the panel location.

Option 2

This one you already have been given. Install a breaker in the service equipment panel and feed the shop from that. You still have to have a disconnect where the feeder enters your shop. So in your case I would install a service rated disconnect without overcurrent protection. Then at the panel location I would install a main lug only panel. The breaker back at the main panel in this case serves to protect the feeder. If you go with a main breaker panel at the shop then you have redundant overcurrent protection for the feeder but sometimes that is just the way it goes. There is no foul or right or wrong though whether the panel has a main breaker or not as long as that disconnect is located at the nearest point of entrance of the feeder.

As for the shops power requirements I would venture to say that 60 amps on the feeder would be close to the worst case screnario for your shop. so I'd just give it a 100 amp panel with a 90 or 100 amp feeder. Your going to need at least a 100 amp rated panel anyhow to get enough spaces for circuit breakers to feed all your branch circuits.

Your wire costs will be expensive in that you are going to need 640 feet of wire based on what you said for the distance to the shop panel from the service equipment panel.

If your buying the wire I would suggest getting USE-2 aluminum in a quadplex. You can look at this at the big box ... they call it mobile home feeder. This will give you 3 current carrying wires plus your equipment ground. You can direct bury this or run it in conduit. You already have conduit so direct bury is irrelevant. #2 al mobile home feeder (USE-2 )will be good for 90 amps in your application.

Doing some quick calculations if you by some miracle pulled 90 amps on the feeder you would have only 3.8% voltage drop at 160 feet using #2 al. I suspect with your load descriptions you would never see more than 2%.

The feeder only needs to be large enough to carry the calculated load but when you start trying to get that precise you often find yourself with an undersized feeder on down the road when you add equipment to your shop.

So keep it simple and give the shop a 90 or 100 amp feeder. 200 amps IMO is giant overkill for a one man shop with your equipment.

Your using conduit so any cable like SER is unnecessary and not allowed underground even inside conduit.

Hope this helps answer some of your questions.

Roger

[Rollie Meyers]

You cannot use SER in a conduit underground, & if it was aluminum the bare AL grounding conductor in a SER cable will fail in a UG conduit because of the water in the conduit & the water is unavoidable.......

The AL will turn to a toothpaste like substance when wet.

[Chris Damm]

If 50amp was good in the old shop why do you need more at the new one. Are more people going to be working at the same time? The size of the shop has nothing to do with the electrical requirements. 100amp should be more than adequate unless you are going to have more people working at the same time.

[Mike Cruz]

The only reason that the size of the shop matters is that you can fit more in it. By more I mean bigger things. In an 800 square foot shop (about what I have now) you can't fit REALLY big machines...things that take up big footprints. In a 2000 square foot shop, you have more flexibility. Also, an 800 square foot shop can be cooled and heated with window units that don't take that much to run. With a 2000 square foot shop, you might be going with a heat pump on a 50 amp circuit.

Ian, 200 is not overkill. It may be more than you NEED, but as I just posted in another thread, you never know what the future may bring. It may be a little more expensive, but if you can afford it, I think it would be worth it...for the peace of mind that you know you won't every max out, and for resale on your house. If I walked into a potential purchase and saw three 100 amp panels and a subpanel and the whole thing looked retrofitted and and and... If I walked in and saw a 300 or 400 amp panel and knew 200 was run to the shop...hmmmm I'd be a LOT more apt to buy. JMO.

[Ian Parish]

Hello Ian


Option #1

Look at your meter main where the two 100 amp breakers are located & see if the distribution busses have feed thru lugs at the bottom.


Option 2

This one you already have been given. Install a breaker in the service equipment panel and feed the shop from that.
Your wire costs will be expensive in that you are going to need 640 feet of wire based on what you said for the distance to the shop panel from the service equipment panel.

If your buying the wire I would suggest getting USE-2 aluminum in a quadplex. You can look at this at the big box ... they call it mobile home feeder. This will give you 3 current carrying wires plus your equipment ground. You can direct bury this or run it in conduit. You already have conduit so direct bury is irrelevant. #2 al mobile home feeder (USE-2 )will be good for 90 amps in your application.

Roger

For your Option One I really like it. I looked at my main meter panel and the wire comes in from the side and the breakers are up and down vs. sideways in most panels. So the feed through lug are not it it and doesn't look like I have room unless I get a new interior for the panel and rotate every thing 90 degrees. this would have made things slick.

for option 2) Everyone I have talked to says I need a main breaker for the shop at my meter. where it enters the house I can just have a connection box to change from the wire that is in the conduit to a different type that will run the 30 feet to the panel.

I think I want to go 100 amp service to the shop, with a 125 amp 24 slot 24 circuit panel. This seems to to fit my needs and future needs. I am still debating the difference between

1) a meter/service panel replacement 1980 dollars

2) a sub panel next to the main meter service panle with it being fed by a 125 amp main breaker in the meter or service panel. 695 dollars.

These costs are for the panel/meter work, an additional 960 is needed for wire and a panel in the shop. I am almost confident enough to do option 2 myself, I would just need to make sure I have the correct wire and parts.

Thanks,
Ian

[Chris Friesen]

It all depends what you want to run at the same time. In most wood shops the worst-case scenario would be:

large stationary tool
dust collector
compressor
air cleaner
heater/AC
lights

Figure out your worst-case load from that and design for that. In my case I was going to run a 60A feed to my 125A shop subpanel, but there was a #8 cable already in the wall, which would give me 40A for free and with a lot less effort.

If I ever upgrade to a large cyclone collector and 5HP compressor I'll need to upgrade the feed, but for now it's fine.

[Steve Costa]

Talk with your electric company about running a separate service to your shop. With a 200 AMP service & panel you avoid the cost of disconnects, etc. In some areas ( I don't live in one) the electric company will pay the cost to run the service to your meter, which can be attached to the exterior shop wall. The electric company or electrician can recommend a wire size.

[Kirk Poore]

... The shop is 2000 sq shop, with a 950 sq foot storage/attic/kids play room in the rafters.
....

In the shop I will have 5 dedicated 220 volts outlets for tools, two 50 amp, 2 30 amp, 1 20 amp. Plus I will have lots of lights and 110 volt plugs. I will have a panel in the utility room about 30 feet from the entrance of the wire into the shop.

...

I think I am deceiding on 100 or 125 amp service to the shop. Is this overkill? With a 24 spot panel. What size and type of wire should I pull through the 3 inch conduit. SER or some type of single strand. Can I pull SER through a 3 inch pipe or will this be a real pain?

Opinion of my options are greatly appreciated.
Thanks in advance,
Ian

Ian:

2000 sq ft (plus 950 sq ft second floor) is pretty big. You'll need to take into account your lighting requirements in addition to any machines--a shop that big may take quite a bit of electricity just for the lights. I'd consider the 100 amp service to be the minimum. I put a 100 amp subpanel in my 550 sq ft shop last fall, and it's certainly not too large.

I also have 12 240V outlets and 11 4-outlet sets for 120V, on 6 240V and 6 120V breakers. Having only 5 240v outlets in a shop that large means you'll be pretty limited in how you arrange stuff, not to mention future growth. It's pretty easy to add outlets at this stage--I'd put a lot more in if I were you.

Kirk

[Mike Cruz]

Steve, and Ian, while this is certainly a viable option (one that I chose as a matter of fact) I don't whole heartedly recommend it...Why? At least where I live, since the shop is not a "dwelling" (which goes for my barn, too) I get charged commercial rates for electricity to my shop (and barn) because the power is run straight from the transformer to the barn and shop (each has its own 200 amp service). So, I pay almost double for electricity to my shop than what I pay in my house. IF YOU CAN, I would up the service to your house to 400, and run 100 or 200 to your shop. In my case, it probably would have been more costly (because of our configuration and stone retaining walls and limited space in the basement corner where the panel is) for us to up the house service and then run to the barn and shop. So, IF YOU CAN, run it from your house...from a monthly bill perspective. If paying almost double for your electricity doesn't bother you, by all means, running a seperate service to your shop is certainly an option. As a matter of fact, if you ever decide to make your wwing a little business and you are looking for deductions ( ) you would know exactly (and could prove it, too) how much you spend on electricity.

[Roger Frazee]

Ian

My previous reply assumed a detached shop from your home. Is the shop detached from your home? I'm picturing a meter/main located on your homes exterior and a 3" conduit running 160 feet underground to a shop detached from your home.

I also understood the meter/main to be located on your home exterior. Things will change some if that is not what you have.

If the shop is detached I'm not understanding why the 'people' your talking to say a breaker for the shop feeder is required at the home near the meter?

Would you be able to post some pictures of what you have including a picture of the interior of the meter main where the 100 amp breakers for your home are located?

Requirements are different depending on your location, power company and local code jurisdiction. But I've never heard that a breaker is required at the meter if the service equipment is located 'on the exterior of the home' to protect a feeder to a 'detached shop'.

It is very possible your meter main may not allow a tap and you may have no other reasonable choice than to have a breaker at the meter panel without changing it.. But I'm simply not understanding this 'connection box and subpanel' thing. Can you possibly be more specific ?