Vernon Tuck
Stainless
- Joined
- Oct 26, 2008
- Location
- Brenham, Texas
Guys,
We are converting a dumpy little farmhouse into a dumpy little machine shop. The 200 amp, single phase, residential 3 wire 230V service entrance is connected to a 200 amp, Square D QO, 8 space "feed through" panel such as are sometimes used for mobile homes.
The location is beyond the jurisdiction of any municipality and nobody seems to care what I do or how I do it. Of course this puts the onus on me to do it right.
The service entrance panel is mounted outside the house on the south gable end. The entire 200 amps then passes through the exterior wall and into an identical QO, exterior, 200 amp box, mounted inside the front bedroom closet. To comply with codes, the closet wall has been removed to create a 36" x 72" "alcove" in the front bedroom. Nothing else is in the closet. Hence, this interior panel complies with the NEC "refrigerator rule.
This second box, also a "pass through", passes the entire 200 amps out yet again, through 2" EMT, straight up into the attic, for a run of about 20', then down again, to a 200 amp QO main disconnect box, mounted on the front wall of the recessed front porch of the house, between the front door (on the left) and a large picture window.
From this disconnect box, the 200 amps passes through the exterior wall, straight into a third 200 amp box mounted in the living room directly across from the disconnect and next to the front door. There is also code required clear space around this box. This third box is also a 200 amp Square D QO box. But unlike the three upstream boxes (counting the disconnect), it is NOT an exterior box and it is NOT a "pass thru" box. It is a 30 space residential indoor box.
This third box is intended to supply the living room and the front porch. The living room contains a lathe and a Gorton tracer mill. The living room also contains a mid 80s vintage Miller Syncrowave 300 transformer type square wave TIG welder. We also have a couple of Syncrowave 500 welders, although these are not currently in the house or on the front porch.
But they might end up there some day. All three welders consume a whopping amount of single phase power. And that's the reason for my electrical scheme in this house. It is unlikely I will ever need/want to run any of these welders at full output. But I am trying to arrange things so that by cutting power to everything else in the house, I could shunt the full 200 amps to one of these welders. 200 amps will keep both the Syncrowave 300 AND the Syncrowave 500s well fed.
It is my understanding that Square D offers a 200 amp branch breaker and that it will fit in my box. Apparently it's a big old honkin' thing and it takes up 4 full spaces. My tentative plan is to buy one of these breakers, and to install it at the very top of the box. This breaker will spend most of its life in the "off" position.
For your information the 200 amp box will also feed a few minor 220v loads - this being the mill and its hydraulic power unit, and a lathe or two, all of which will be powered by VFDs. This box also feeds a 20hp rotary phase converter. The RPC is installed and operational but for the moment it amounts to surplus capacity. Some day it might supply power to other equipment on the front porch or on the north end of the house.
The said 200 amp branch breaker is pretty damn expensive. Going from memory, I think it's crowding $400 dollars. An alternative approach, and a cheaper one, would be to power the welder(s) from a 100 amp, 125 amp, or even a 150 amp branch breaker. These breakers are quite a bit cheaper than the big 200 amp breaker although they're still pretty expensive.
Under this alternative scenario, I would simply rely on my self-control not to crank the welder up too high. Under the 200 amp branch breaker scenario, I would conversely rely on my self-control to de-energize the rest of the house before flipping the breaker and energizing the welder.
My question to y'all is not "Is this an optimum arrangement. I know that it is not. However, I am attempting to get maximum energy management versatility out of a small residential service. So my question is: Is there a better way?
The original house wiring, which was conventional residential through the wall romex, is now totally isolated from this electrical scheme. So for purposes of this discussion there are no "creeping, uncontrolled loads". The wiring throughout the 3 boxes is 3/0. The house is completely surrounded by a grounding ring of heavy single strand, zinc plated bare copper wire, connected to industrial quality 10' x 5/8" copper clad grounding rods driven into the ground every 10' around the perimeter of the house.
In summary, I suppose my question is really this: Am I safer relying on the 200 amp breaker? Or should I use a 100 amp, 125 amp, or 150 amp branch breaker in this scheme?
Thanks for any and all replies, suggestions, ideas, and admonitions.
Vernon
We are converting a dumpy little farmhouse into a dumpy little machine shop. The 200 amp, single phase, residential 3 wire 230V service entrance is connected to a 200 amp, Square D QO, 8 space "feed through" panel such as are sometimes used for mobile homes.
The location is beyond the jurisdiction of any municipality and nobody seems to care what I do or how I do it. Of course this puts the onus on me to do it right.
The service entrance panel is mounted outside the house on the south gable end. The entire 200 amps then passes through the exterior wall and into an identical QO, exterior, 200 amp box, mounted inside the front bedroom closet. To comply with codes, the closet wall has been removed to create a 36" x 72" "alcove" in the front bedroom. Nothing else is in the closet. Hence, this interior panel complies with the NEC "refrigerator rule.
This second box, also a "pass through", passes the entire 200 amps out yet again, through 2" EMT, straight up into the attic, for a run of about 20', then down again, to a 200 amp QO main disconnect box, mounted on the front wall of the recessed front porch of the house, between the front door (on the left) and a large picture window.
From this disconnect box, the 200 amps passes through the exterior wall, straight into a third 200 amp box mounted in the living room directly across from the disconnect and next to the front door. There is also code required clear space around this box. This third box is also a 200 amp Square D QO box. But unlike the three upstream boxes (counting the disconnect), it is NOT an exterior box and it is NOT a "pass thru" box. It is a 30 space residential indoor box.
This third box is intended to supply the living room and the front porch. The living room contains a lathe and a Gorton tracer mill. The living room also contains a mid 80s vintage Miller Syncrowave 300 transformer type square wave TIG welder. We also have a couple of Syncrowave 500 welders, although these are not currently in the house or on the front porch.
But they might end up there some day. All three welders consume a whopping amount of single phase power. And that's the reason for my electrical scheme in this house. It is unlikely I will ever need/want to run any of these welders at full output. But I am trying to arrange things so that by cutting power to everything else in the house, I could shunt the full 200 amps to one of these welders. 200 amps will keep both the Syncrowave 300 AND the Syncrowave 500s well fed.
It is my understanding that Square D offers a 200 amp branch breaker and that it will fit in my box. Apparently it's a big old honkin' thing and it takes up 4 full spaces. My tentative plan is to buy one of these breakers, and to install it at the very top of the box. This breaker will spend most of its life in the "off" position.
For your information the 200 amp box will also feed a few minor 220v loads - this being the mill and its hydraulic power unit, and a lathe or two, all of which will be powered by VFDs. This box also feeds a 20hp rotary phase converter. The RPC is installed and operational but for the moment it amounts to surplus capacity. Some day it might supply power to other equipment on the front porch or on the north end of the house.
The said 200 amp branch breaker is pretty damn expensive. Going from memory, I think it's crowding $400 dollars. An alternative approach, and a cheaper one, would be to power the welder(s) from a 100 amp, 125 amp, or even a 150 amp branch breaker. These breakers are quite a bit cheaper than the big 200 amp breaker although they're still pretty expensive.
Under this alternative scenario, I would simply rely on my self-control not to crank the welder up too high. Under the 200 amp branch breaker scenario, I would conversely rely on my self-control to de-energize the rest of the house before flipping the breaker and energizing the welder.
My question to y'all is not "Is this an optimum arrangement. I know that it is not. However, I am attempting to get maximum energy management versatility out of a small residential service. So my question is: Is there a better way?
The original house wiring, which was conventional residential through the wall romex, is now totally isolated from this electrical scheme. So for purposes of this discussion there are no "creeping, uncontrolled loads". The wiring throughout the 3 boxes is 3/0. The house is completely surrounded by a grounding ring of heavy single strand, zinc plated bare copper wire, connected to industrial quality 10' x 5/8" copper clad grounding rods driven into the ground every 10' around the perimeter of the house.
In summary, I suppose my question is really this: Am I safer relying on the 200 amp breaker? Or should I use a 100 amp, 125 amp, or 150 amp branch breaker in this scheme?
Thanks for any and all replies, suggestions, ideas, and admonitions.
Vernon