Posted: 1/2/2016 1:09:08 PM EDT
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I have a 30x50 metal building on some land with a 2" PVC penetration for electrical. I will eventually have another 30x50 that we will live in for a while, and then a house after that. I would like to get electrical service this year. I have a few questions about distribution. The electricity will need to go to all of these buildings. I will also want a transfer switch for a future ~20 kW generator. What is the best method for distribution? 1. 200A transfer switch on building exterior feeding another exterior breaker box with circuits going to each building? 2. If a house is normally 200A, and the service is 200A, would I have a 200A breaker to the house and 100-150A breakers to the metal buildings? One metal building will have HVAC. 3. My garage breaker box has more than 200A worth of breakers, so I assume there is no rule on circuits having to add up to the total because not everything is running at once. 4. I will also have a well. Should the well be on a 4th circuit going to a pump house? 5. If four circuits come out of the main breaker box, how can I distribute them in the cleanest manner? I assume there is no such thing as an under ground connection box. Recall that I have one 2" penetration to the current building, but the main box can go have a penetration through the wall. I'm trying to avoid having 3-4 conduit legs coming out of the bottom of the main breaker box. Thank you. |
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If I were you, run the service to a 400 main with meter base with two 200 amp breakers, don't forget to get neutral and ground bars for this. This panel should also have about 8 or so additional circuits. Use the two 200 amp breakers to feed two more of your buildings. Using two of the spaces in the main panel install 150 amp breaker to feed a sub panel in the first building where the main is. As far as your future back up generator, try to plan your circuits around the load you need the generator to carry. Don't take the 20kw rating to the bank, all generators are not built alike. You shouldn't want to max out no more than 80% of a generator therefore 16kw or about 65 amps. Most 20kw gen sets come with 200 amp transfer switches. You may want to run all of your must have circuits out of one panel that is tied with your transfer switch. If this is going to be inspected pay attention to grounding and bonding. Well pump from the panel tied to transfer switch. There are many variables to your questions. Distance between buildings? Voltage drop? Nothing wrong with conduit and wire except for cost. Is it possible to run conductors on messenger wires between buildings? How is your power provider going to run the main service? For a 400 amp main, your utility company will want a 3" conduit if not 4" for the conductors.
I am a licensed electrical contractor, more than happy to help ya any way I can. Like I said, I would go with a 400 amp main service. I'm sorry I can't remember what brand I used to use for 400 amp mains. I haven't done residential in a few years. For what it's worth, I bought most of my residential material at Home Depot or Lowers if they had it, they were usually cheaper on the basic stuff than the supply houses. |
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I love big elec services, but unless he has some plans for a bunch of high amp draw stuff, 200 amp main is plenty.
This would be a good app for a 200amp meter main, might as well put in the transfer switch now too. Send appropriate conduits to future buildings with 150 to 200 amp wire to sub panels at each location. |
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Quoted: I love big elec services, but unless he has some plans for a bunch of high amp draw stuff, 200 amp main is plenty. This would be a good app for a 200amp meter main, might as well put in the transfer switch now too. Send appropriate conduits to future buildings with 150 to 200 amp wire to sub panels at each location. I was going to question the 400A service. From what I've read online, 400A is commercial grade. Worst case scenario load would be: 600 ft head well pump 20 gpm water supply Dryer ~2.5-3T A/C for metal building ~3.5-4T A/C for house 220V air compressor welder When we resolve the components, I want to talk about how to minimize conduit. Is this correct:  |
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I'm not an electrician; just a guy who recently had to rewire (and is still completing this process) an old property with a big house and multiple out-buildings. Here is what I did (am doing) for what it is worth.
200A service comes to the house, with a 200A breaker box in the basement. The first breaker in that box is a 70A feeding #4 wire going to a subpanel in another part of the house so that I can run those circuits from that branch to some bedrooms instead of having all of those circuits running all the way back to the basement (they would be very long runs of wire and it is an old house with thin walls and limited routing options). The second breaker slot is (will be) a tied breaker that can only be switched on when the main is switched off. The generator will plug into that. I'm only going to be running a backup genny that can handle some necessities, not power everything. If you have a bigger amp generator you may have to run heavier wire than can fit in a breaker like this. The third breaker in the main box is a 40A feeding 8/3 direct burial (UF) wire to a small shop outbuilding sub-panel. No conduit other than right through the basement wall. The fourth breaker in the main box is another feed to direct burial wire going to another shop sub-panel. Like all of those above the sub-panel has a 100A breaker in it, but the breaker in the main panel sets the max amperage in that circuit. My well is fairly close to the house, so it is just another 20A 240V breaker at the main panel. 12/2 Direct burial wire runs to the well. On #3 you are correct. Since not everything is running at max amperage all the time the total amps of your breakers may exceed the main breaker's max capacity. If your out-buildings are far away, you'll have to run heavier wire than your amperage requirement in order to reduce voltage drop. Good luck. Sounds like a fun project. |