Electrical Repair Questions? Ask an Electrician for Answers ASAP
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1) Good afternoon...... Yes, I am available. What are your questions regarding service for a workshop?
I'm considering adding service to out building on the property to create a workshop/fab shop.
The land is county, rear of property with no easements. There's a pole about 75~100' away with 480 power.
I want to run power to the building to run equipment I'll buy along the way with some being 480 while others will run 230(? or 208) while still needing 120v outlets and lighting.
What will happen here after I get my local utility to drop from the pole to the building?
My understanding is I'll need a transformer for the 480 to 208/120.
So, power drops to building--->goes into 480v panel--->drops out to transformer---> out of transformer to 208/120 panel--->then into building?
1) Just to confirm, the building will have its own dedicated meter from the utility, correct?
2) In your application, you will be going from the utility 3-phase 480 VAC and will require a 480 VAC main disconnect which will feed into 480 VAC a step-down transformer, then out of the transformer this will feed into a 208 3-phase panel which will provide 208 3-phase as well as 120 single phase.
3) The main disconnect, the step-down transformer and the 208/120 panel will be located inside the building. It is recommended that the utility meter socket be located back-to-back from the 480 VAC Main Disconnect switch. If the 480 VAC Main Disconnect switch cannot be located back-to-back from the meter socket, your local inspector (Authority Having Jurisdiction) will need to approve for the distance from the meter socket out to the main disconnect. Reason being is the National Electrical Code is limited on the distance as to how far the main disconnect switch can be located from the meter socket.
The 480 VAC Main Disconnect, the step-down transformer and the 208/120 panel should all be co-located as close as possible to each other. Either way, voltage drop calculations will need to be performed based upon the type of feeder conductors (copper versus aluminum), the distance from the main disconnect out to the transformer and the distance from the transformer to the main 208/120 load-center as well as the amperage load in the panel.
4) You will also need approval from the AHJ as to how the system will be grounded. For example, if the building will have concrete footings, I recommend installing a "Ufer" Grounding Electrode Conductor directly to the concrete footings as the "Ufer" is the best ground available. If a "Ufer" cannot be deployed, and the building will have a city cold water metal supply piping, then the ground connects to that. If no city water supply but using a well, then the ground will connect to the well head. Either using a city or a well water supply grounding, a supplemental grounding such as a minimum of (1) one or more 8 foot copper ground rods will be required. Many AHJ's allow the use of a "Ufer" ground as the single ground and a supplemental ground such as ground rods, grounding plates, water supply ground, etc, may not be required. The AHJ would need to make this call and advise you to what they require.
5) Another area where you will need to engage the AHJ is the type of raceway they will require connecting from the exterior meter socket to the main disconnect. Most likely, they will require Rigid Metal Conduit. Here again, the raceway type is their call.
6) If the service drop will be over-head and not a service underground lateral, then there are more additional requirements. Underground is more cost effective and the preferred service routing method.
2) Is the 480VAC a service panel/disconnect (i.e.-how do you access 480 vac power if required)
3) Can be back to back
4) Dont know yet. Maybe pouring a new floor as current concrete is pretty bad off which mean s "Ufer" would be perfect.
5) Will be overhead as easiest to run from utility
Can you give hipshot part costing items listed in #3?
1) The 480 VAC disconnect is either switch gear and would house a 480 VAC main breaker or a 480vac service panel. Think of this as more as a distribution panel versus a typical electrical panel or a load-center that would be installed in a home. These types of switch gear are fairly large in size and are typically used in commercial and industrial factory applications. The 480VAC switch gear will act as the main disconnect via a 480VAC rated main breaker sized according to the required total amperage load. A 480VAC switch gear can also house a 480 VAC breaker to act as the disconnect to shut down the step-down transformer which in turn will shut down the secondary of the transformer, ie, the 208/120 load-center. In this configuration, the 208/120 load-center acts as a large sub-panel.
For your application, I don't think that a 480VAC switch gear would be required since your building is not a full-blown factory. You can get away with a 480VAC panel with a 480VAC breaker sized according to the expected building amperage load. This would act as the Main Disconnect. If deploying a 480 panel, this can also house the disconnect for the primary side of the transformer. The 208/120 load-center coming off the transformer secondary will act as a sub-panel and will house all of the 208 3-phase and 120 single phase branch circuits. If the 208/120 panel will be co-located near the 480 panel, then the 208/120 panel may be either a Main Lug or a Main Breaker panel. Keep in mind that if using a Main Breaker panel, this will be more expensive than a Main Lug panel due to the cost of the breaker. You will require a dedicated wall/floor space area to install the equipment.
2) The "Ufer" is the most widely used Grounding Electrode Conductor for commercial and industrial new construction. It is also becoming more prevalent in new residential construction. A "Ufer" ground must be connected directly into the concrete footings and not just to a concrete floor.
3) Back-to-back is good and is the preferred method. This will minimize voltage drops.
4) If running the service entrance cables as over-head, this may be the easiest method from the utility but it will be more costly to you. Overhead is typically more labor intensive compared to underground entrances. The riser mast will need to be Rigid Metal Conduit resulting in a larger diameter conduit for stability purposes. Depending upon the roof structure of the building, ie, soffits or flat roof, the AHJ may require additional bracing for the riser mast. For an overhead service entrance, you as the owner are responsible for all material and labor up to the weather head drip loop where the utility service entrance wires get connected using Burndy connectors.
5) Without knowing all of the approximate building dimensions, roof type, exterior building wall material types, loads, quantity of branch circuits, AHJ approvals due to local requirements, grounding methods and transformer KVA rating, that is going to be difficult for me to provide you with even a budgetary price. Due to the many variables in this type of design, I would recommend that you engage a local electrical contractor who has design experience in this type of application and is familiar with the local electrical code requirements. I would recommend a site survey meeting with your local AHJ, the electrical contractor and yourself.
Thank you for the excellent service rating as well as the bonus.............much appreciated!
If you have any follow-up questions, just reply back to this same question. No need to create another question.
Take care and have a great evening.............Thanks................Kevin!
Thank you Kevin. I'm much less confused but feeling this will not be "worth the $$" as it appears this is going to be quite spendy.
We'll see I guess.
Have a good evening as well and thanks again
Glad I could assist you and provide you with an explanation on some of the basic requirements for this type of service application.
Yes, this type of new service install is not going to be priced similar as a residential 200 amp service panel would be priced. Due to the cost of the three-phase equipment, transformer and the associated labor, the price will be reflective and it will be costly. Much of the project cost will be due to the three-phase equipment as this is always much higher equipment costs versus a single phase entrance. I understand your cost concerns.
If you do decide to move forward with the project, I would recommend that you obtain a pricing quote from (3) three reputable and licensed electrical contractors who are experienced in this type of design & installation.
Thanks again and hope all turns out well with the project..............Kevin!