I have read the 56 threads on the 220 v service and chose not to steal it as it’s a serious issue. Not to be redundundant but I am setting up my retirement shop 24×48 with a ful range of tools and think that a 100 amp panel tapped from my 200 service should be enough to service a one man shop. The house was built in ’94 has a heat pump and an electric stove and dryer in the laundry. The stove will go as you CAN’T make a proper white sauce on an electric stove. It’s great for baking or roasting but $uck$ for delicate stove top cooking like a reduced rosemary madiera sauce over a pair of fillet mignion.
I plan to leave the lighting on the house panel and split it there if I must or create another circuit or two to split the shop (a real possibility as some areas don’t need to be lit all the time -lathe, mechanical(read truck work dirty bench ) or the coal stove in the corner and perhaps the shop in two parts.
In the sub panel I would propose six 30 amp 110v utility circuits running in three paths . A&B along the east wall, C&D running down the center main beam in the overhead and E&F running down the west wall. All of these on 10-2
The biggies are . 3 hp Dc cyclone from the main panel
3hp Unisaw from the sub
1 1/2 hp contractors saw from the sub
5 hp compressor from the sub
two 1 hp jointers from the sub
I am still shopping for a small heat pump to heat/cool the basement shop.
If this plan has any holes in it please advise .
All good advice very welcome. Thanks, Pat
ps, I am out of here 11/19 to TN back on @12/ 15 happy turkey.
Replies
My first concern with all of that equipment pulling in the electricity would be the size of the transformer you're pulling it off of. May people don't realize it, but an undersized transformer will hurt as badly as undersized wire when it comes to voltage fluctuations. I think that given that load, you should probably have a 15 kva transformer all to yourself. Not one of those "lets share a 25 kva transformer with 6 or more people" setups some municipalities seem to enjoy creating.
The other thing is making sure you balance out your loading and don't end up loading up one buss excessively compared to the other. That will screw up your household voltages and blow a transformer if the load is high enough on one buss. (It'll literally blow the top right off of the can. It sounds like a cannon going off.)
You could split the lighting up, but people will usually run all of the lights or none of the lights anyhow. Your shop, your call.
Lastly, run a dedicated line to to that air compressor, another to the unisaw, and yet another to the dust collector, since they're high load stationary tools that could possibly all be on at once.
I hope that helps!
Mr. B. thanks for the info. The big guys are planned to be separate circuits as Saw, compressor and DC could be all in use. The utility 110 will be two circuits per run, precluding two big hand helds or bench units cranking at the same time with me 75% of the time alone and rarely a neighbor or my son when they visit.
The lighting will be three circuits but with switched sections. Waste not want not. The electric coop said that I have more than enough capacity as they upgraded when my house was built in '94. Both neighbors heat with wood and the third is never there. These are 5 to 10 acre plots and we are the only service draws on this leg of the system. Pat
I have a couple of issues with this situation. First off, you don’t have control over how the utility company distributes power so you don’t need to worry about their transformers, and there is nothing you could do about it anyway. (Mr. B, where are you getting your numbers from anyway? A 15KVA transformer would provide only 60 amps. His 200-amp service alone requires 50 KVA without sharing! Furthermore, load balance isn’t an issue when the tools listed are 240-volts.)
You have 200 amp main service and a 100-amp subpanel will be plenty for running a shop of this size.
The first thing I noticed with your proposal is the use of 30-amp circuits at 120 volts. You cannot place standard 15 or 20 amp outlets on a 30-amp circuit. Your shop will run fine with 20-amp circuits for your outlets, and you are permitted to place 15-amp outlets on a 20-amp circuit. For a shop of your size, six circuits should be OK for standard outlets, but you may want to plan ahead for high draw stationary tools (like your contractors saw) and place them on limited circuits.
Your Unisaw and dust collector will each require a 20-amp, 240-volt circuit.
If your compressor is a true 5-hp, then it will require a 30-amp, 240-volt circuit.
Your contractors saw and jointers are small enough to be dual voltage, so they would either require 20-amps at 120-volts, or 15-amps at 240-volts. These tools could share the same circuit, or even be plugged into your general use circuits.
Make sure the new subpanel is unbonded with separate Ground and Neutral busses. If this is a separate building, it is a good idea to install a ground rod even though the primary ground is coming from the main building. It needs to be a unified grounding system with all ground rods tied together.
240*200 = 48000 VA on the -secondary- side.Where I'm from transformers are rated on the primary side, so 48kVA/*240 (secondary voltage)/2400 (primary voltage change for your local voltage) = 4.8kVA required.Make more sense?
That's not exactly the answer I was expecting, but I was starting to get the feeling that it was going to be a colorful one nevertheless.Where I come from it doesn't matter how you rate a transformer because power-in is equal to power-out. That's one of the fundamental laws of physics that you just threw out the window, and I am pretty sure Nikola Tesla is going to want it back. (grin)In a step down transformer, when the voltage is reduced by a factor of 10 (to use your example) then the current goes up by a factor of ten. So to get 200 amps at 240 volts, the primary side receives 20 amps at 2400 volts.200 x 240 = 20 x 2400 = 48KVA
Where I'm from transformers are rated on the primary sideWhere I come from, it doesn't matter. If the secondary is 240V @ 200A, and the primary is 2400V @ 20A, it's still 48KVA.--
Todd
Edited 11/18/2006 6:06 pm ET by Toto
Rick knows of what he speaks. Follow his advice. I've been operating a one man professional shop off 100 amps for years, it's plenty if you don't have four guys running tools under load simultaneously.Lee
All my work is done on the consumer side of the transformer so I'm no expert on how the power companies size their equipment, but 25kva is a typical size for residential areas around here. I just looked out the back window to double check, and in fact the transformer on the pole behind my house is a 25kva, and it serves three houses. Also, for what it's worth I believe the local utility's primary voltage on their side of the transformer in residential areas is 13.8kv.
For new construction projects, they generally have me fill out a load sheet that lists the anticipated electrical loads - lights, heat, motors or whatever - and they select the transformer size from that.
Rick, thanks, that sounds solid to me. I am an old submarine guy-belt and suspenders at all times- and not about to chintz on this design to save a few bucks. I will still use 10ga to the three 20A utility runs but will buy commercial 20A duplex for the split circuit quad boxes. The 1 1/2 hp contractor saw needs a 30A on 10ga as it's 48' from the source, an existing circuit previously for two chest freezers-I have a temp extension of 10ga sj cord that works fine for the moment as I construct this thing.
I am planning the 100A box to be 25' down the long wall of a 24x48' space with the 200A main service box centered on the short end. This was to shorten up on the runs for the dedicated 240 and 120 circuits, no sense in wasting all that copper. I already bought another ground rod but should I drive it in outside where the new box will be or pick it up for the 100A take off outside where the house service comes in? Come to think of it, I really havent seen if there is a ground rod off the main service , Iwill know by Wed.
I am trying to plan smart and don't want to do this twice and grateful for the advise. I am out of here in the A.M. (sunday) might look at the mail and will be back @ 12/15 going to TN with the Unisaw in the truck and to see the g'kids in Pa on the return. All the best , Pat -happy turkey
Edited 11/18/2006 11:10 pm ET by PADDYDAHAT
Pat,
I just had a 100 amp subpanel installed in my attached 2-car garage shop. The house has a 200 amp panel that I upgraded last year. My shop is 18.5x24. If you are installing lighting, don't short change yourself. I had eight, 8 foot, 2-bulb T8 electronic ballasted flourcescent light fixtures put in with bulbs of a minimum of 85 CRI (color rendition index). Two of the fixtures were hooked up to my house panel and the other six to my new subpanel; that way, if one circuit blew while running a machine, the other circuit of lights will stay on preventing me from finding myself in the dark with a 12" saw blade turning. I drive a MiniMax combination machine equipped with three 5HP motors, a MM20 bandsaw with a 5HP, a 3HP Oneida DC, and a drill press. All but the drill press have dedicated 220 lines. The electric data plate on the Oneida calls for a 20amp 220, while the other large machines require a 30amp circuit. As a one-man shop, I will only be running the DC and one other machine. I also installed a mini-split HVAC system and so far it is doing great for both a/c and heat (and dehumidication) here in Florida with its hot and humid days. The mini-split system cost me $1,600 installed and requires 220 service, a 20 amp I believe. I have not yet installed any insulation in the garage and even with open soffits it has not upped my electric bill substantially. I also installed ample 110v outlets including two quads at my workbench as well as others. In addition, I had a 30 amp 220 outlet installed for my wife's kiln. My electrician assures me I will have ample power to run the shop and the house. I made up my own extension cables with locking plugs and 10/2 cable. All my machines are on Zambus castors (rather than mobility stands) which work like a dream. I can move my 750 pound band saw with one finger.
Again, do not scrimp on lighting. Everyone said I was overdoing it with the fixtures, but I strongly disagree! I also have a 4-bulb 48" flourescent fixure over the workbench.
J Wright
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