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GreenTrench
Jun 19, 2004

Has anyone seen me?

Three-Phase posted:


(Also, the NEC says you cannot derive a branch circuit from an autotransformer. I need to check some details as to what's OK with the NEC and what isn't. Sadly my codebooks are at work.)


You freaked me out a bit since I install battery-backup solar electric systems with autotransformers so I looked this up;

210.9

"Branch circuits shall not be derived from autotransformers unless the circuit supplied has a grounded conductor that is electrically connected to a grounded conductor of the system supplying the autotransformer." (I'll ignore the exceptions).

Essentially, you can't run two hots without a neutral on either side of the autotransformer.

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GreenTrench
Jun 19, 2004

Has anyone seen me?

Elendil004 posted:

There's no applicable codes this is in VT.

Five seconds of googling gives me

http://www.dps.state.vt.us/fire/lic.../Electrical.htm

The 2008 NEC is the adopted electrical code.

GreenTrench
Jun 19, 2004

Has anyone seen me?

grover posted:


Hot water on demand draws a LOT of current- an obscene amount, really. A small one may not be too bad, but a large one is probably just not practical. Just run your tap for 10 seconds like the rest of us

On demand hot water heaters use less energy than a conventional electrical hot water heater since it doesn't have to keep a giant tank of water warm. But your flow is limited.

Gas hot water heater is cheaper than both though.

GreenTrench
Jun 19, 2004

Has anyone seen me?

grover posted:

Less energy, but FAR more power; don't confuse the two.

A 150A tankless water heater can only heat about 4 gallons per minute, wheras a 40 gallon water heater can be powered from a 30-40 Amp circuit. It's the difference between brewing a pot of coffee over 5 minutes vs plugging in 6 or 7 coffee pot heating elements in-line, each drawing 15 amps, so you can heat is as you pour the water into your cup. Likewise, you need to double or triple the size of the gas lines to a gas on-demand water heater. It's easy to run the costs way up in the name of energy efficiency. Properly insulated hot water tanks don't even waste that much heat.

Most definitely they are different. I think I misread what was going on.
I thought he wanted to go to an electric hot water heater to save money.

GreenTrench
Jun 19, 2004

Has anyone seen me?

Morkai posted:

This little luxury wouldn't be about how fast the water gets hot for a shower, but to have an unending supply of hot water for 4 people to have showers without being rushed. Like you said they pull a lot of current, but less energy overall than doing a larger tank water heater, or two in series configuration. It also wouldn't be a large model, it only needs to feed the shower, not the whole house.

Tankless hot water heaters don't work in a series configuration. Very few of them throttle the power, and the ones that do have a minimum power output. Because manufacturers don't ever want to put out scalding water, if the temperature coming in is too high (say 90F), the tankless hot water heater won't come on. Not only do you deal with luke warm water, you're susceptible to Legionellosis. A large tankless hot water heater at 3gpm can be fine for a house if you don't have multiple people using hot water at the same time. It all depends on preference and what you're willing to work it.

Morkai posted:

I'm all about planning. I've sized up everything I intend to do, and I think my 200A service will be just enough. I'm just undecided on if I like the idea of just enough, or if I want to have room for more if some other factor changes. For me personally, I'd want the room, but I don't think a potential buyer is going to think about a maxed out panel vs their future remodeling plans. What does it cost to go all out and hit 400A?

Thanks for you help!

Going over 200A isn't that easy. The feeder cables coming in may not be rated for over 200A and may have to be replaced. I've also heard of some utility companies requiring external disconnects for services over 200A.

The cost depends on what area you're in. I've heard of service upgrades as cheap as $500 and go upwards of $3000. As always, get a quote, shop around, and make sure the electrican gets a permit.

If you're doing it yourself, you'll need two 200A panels with a wire trough below. The feeder cables from the utility company go into the wire trough and branch off to the two panels. If you are doing this, GET A PERMIT so you can get a cut-in card for your utility company. They'll also come out and cut tag on your meter so you can remove it and not work on live wires. I wouldn't recommend do it yourself though.

Morkai posted:

I just want to augment the capabilities of my existing water heater, and only for the shower in the master bath. Given how well my water heater works, which is already electric and has a 2" added insulation blanket, I can go with one of the smaller 30-50A@120V on-demand types just to boost the temperature after the tank is depleted.

I don't think they go that small. A Stiebel Eltron that'll raise water from 50F to 105F at 3gpm is 24kW.

GreenTrench
Jun 19, 2004

Has anyone seen me?

Mthrboard posted:

Quick question; does anyone here know if you are allowed to do an entire panel swap-out by yourself in Minnesota? I know we're allowed to do pretty much everything else in a residence, but I've read conflicting reports online as to whether replacing your main panel is allowed or not. My mom just bought a cabin by Itasca state park, and I want to upgrade from a 100 amp panel to a 200 amp, mainly so we can install a tankless water heater. I know what all is involved, and I believe I am up to the task, I just want to know whether or not I can actually do it legally.

You'd have to go to your local building department to find out. They may require your mother to pull the permit unless your name is on the deed. You definitely need to pull a permit so you can get a cut-in card for the utility company. They need to check the feeder cables and/or transformer to make sure it's fine for a 200A service.

IsaacNewton posted:

I have this going from my house's 200 amp panel to my garage: (underground)



I did the muscular part (digging the trench and the 3in hole in my garage's concrete floor) now comes the part I need help with.

I'd like to wire all this up for 240v @ 60 amp (I might have a 240v compressor eventually but I wont be running much machinery of this, is 60 amp too much for lighting, a few electrical outlets and the compressor?) How should I wire this up on the panels?

Red and black are the two hots, the white is the neutral, and the green is the ground. I don't think direct burial comes in anything smaller than #6, so you're fine with a 60A breaker. There should be some writing on the outer insulation assuming it has not rubbed off that will tell you exactly what it is.

IsaacNewton posted:

Well I'm preparing to get a permit for this, hoping to have some help..

Here's how I plan to install this;


100amp breaker (it can do 240v since it's a double pole) @ the house panel, (Why don't they make 70 amp breakers to match their 70amp panels?)
70amp panel (8 slots) in the garage

For now I'll only drop 2 15 amp breakers (1 for external light, 1 for internal lights) 2 20 amp breakers (one for each sides of the garage's wall electrical outlets) into it, but I will have room to add the breaker needed for a compressor etc.

How's this sounding to you guys?

As grover said, you cannot feed a 70A subpanel with a 100A breaker. I'd recommend this instead. Type QO breakers are incredibly common.

GreenTrench
Jun 19, 2004

Has anyone seen me?

Hillridge posted:

I'm working on a design for a grid tied 5kW solar array I plan to install on my house. The inverter will need to be connected to my breaker panel via a backfed breaker. My house was built in the 70s and has those awful pushmatic breakers. I have plenty of 20A breakers open since the house was converted from electric to gas heat, but I think I'll need a 30 amp for the inverter.

A few questions:
Would a 30 amp be sufficient?
Can pushmatic breakers still be bought?
Are they rated for backfeeding? This one is real important because I'd need to hook it up this way.

I don't want to add the expense of replacing the whole panel if I don't need to, so are there other options if the pushmatics are unavailable or can't be backfed?

Have any of you done solar installations? I know several electricians, but they don't have any experience with grid tied solar.

I hope you know what you're doing since installing a PV system is more complicated than most people think.

Yes, you need a 30A breaker. However, if your panel is not rated at least 150A, it'll be a code violation.
You can still get pushmatic breakers. Just not at home depot. You'll have to order online.
All breakers are rated for backfeeding unless they specifically state line and load on them.

There are other options - installing a subpanel from your main service panel. Or you can do a line side tap (although you would need a 60A breaker for that, and then a subpanel with the 30A breaker for inverter.)

If you want, you could send me the design and I'll check it over for you. If you are connecting a grid-tied system, you'll have to file an interconnection agreement with your utility company.

GreenTrench
Jun 19, 2004

Has anyone seen me?

Hillridge posted:

Thanks for the advice.

What state(s) are you licensed in?

We have an in-house electrician where I work, and he has strongly recommended that I replace my pushmatics with something more modern. I've thought about doing that long before I started this solar install plan, so I think I'll follow his advice. I already have 200 Amp service (the house used to be electric heat), so that's not a problem. Plus if I do it as part of the solar install I'll get 30% of the cost back from the feds.

I filed the pre-approval for the grid tie, and they responded that they are mostly concerned that the inverter is UL 1741 certified, and sent me some more forms.

I think I've nailed down which inverter I'll be using (Xantrex GT5.0) so now I am picking out the panels and working on the whole system design for the rest of my pre-approval paperwork.

I'm not licensed. I design these things for a living though (NABCEP certified).

You'll be fine with the GT 5.0. That's a pretty standard inverter, and a good one at that. The only issue I have with it is that the ground fault fuse is a pain in the rear end to get to compared to other inverters and it doesn't have a log of how many hours it's been up and running.

GreenTrench
Jun 19, 2004

Has anyone seen me?

You'll probably want Suntech. They're good panels and one of the cheapest out there - Conergy has them. I'd try to stay away from Canadian solar since they're not that great. Yingli is new and they're pretty cheap, but I have zero experience with them.

Here are some dealers you can look at.
Sunwize
DC Power
Focused Energy
Conergy USA

If you have some issues with the dealers, altestore has some suntechs by the pallet that aren't priced too unreasonably.


Xantrex's configuration tool is pretty good. Just remember to put in the record low for your area. Also, NEC 2005 and previous editions didn't recognize manufacturer's specifications for open circuit voltage calculations - you had to use a table. The NEC 2008 changed it and now requires you to use the manufacturer's specifications (this is how xantrex calculates it). Do you know what edition of the NEC is in effect in your area?

GreenTrench
Jun 19, 2004

Has anyone seen me?

Unfortunately I just switched to a company that does large scale systems. I get truckloads of panels straight from distributors.

If you're looking for US panels, you'll want Evergreen or Sharp (although technically sharp's cells are manufactured in Japan). Solon, REC, and Suntech are building plants in the US so panels can be assembled here, and they'll be Buy America compliant.

Have you figured out which racking you're using?

GreenTrench
Jun 19, 2004

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According to their manual, it's rated for 160lbs. So in an aread with no snow and 90mph winds (average wind), it can do 32" OC spacing. That's pretty weak. It's also a shared rail system, so you have to lay it out perfectly, which isn't something I'd recommend for an inexperienced individual.

I almost exclusively use Unirac. Their L-feet aren't ever breaking, and usually you can do 4' spacing on them. It doesn't have flashing, but using butyl tape on the underside, and around the head of the lag screw, and putting some sikaflex in the hole, you won't have any leakage. The company I use to work for has over 10,000 of these pentrations, and there were only had something like 10 calls for leaks.

GreenTrench
Jun 19, 2004

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tadashi posted:

I just bought a foreclosed house that was remodeled in 2003 by a bunch of amateurs.

In a previous inspection of the house, the inspector noted that the grounding was not completed correctly. This is what the grounding wire for the house looks like (it's that wire attached to the pipe):

The first inspector stated that the grounding wire is supposed to be grounded above the handle for the main water shut off so it should be higher on the pipe. He said that if this was not fixed, that any plumber coming to work on the house might have to detach the wire. My inspector noted the location of the main water shutoff but did not mention any issues with the grounding wire. Is this a problem?

That's the GEC. If that wire is removed, it can present a serious issue to your house. The odds of a plumber coming in and removing that section of the pipe is pretty small, but it shouldn't be too hard to fix. BTW, if it's the township electrical inspector, you must fix it since he's the one who pointed it out.

I'm having a hard time making out the pic, but if it's a ground clamp, is there any reason why you can't move it? Or better yet, drive a new ground rod in and attach the GEC to that.

GreenTrench
Jun 19, 2004

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grover posted:

Surge suppressors are OK because they're a loophole! Power strips and extension cords are only supposed to be used temporarily. IIRC, it's for less than 90 days and only during construction, or something stupid like that.

I never thought of the code compliance of power strips before and it got me curious. So I did some looking.

Power strips are to be listed to UL 1363. I didn't find anything in the NEC about Relocatable Power Taps (the closest is Article 380 - Multioutlet Assembly), so I have to go by the standards.

According to that outline, they can be used for computer workstations and the like, but they can't be used in construction sites. Nor can they be daisy chained, or go through walls, or take the place of permanent wiring.


So unless I'm missing something here, power strips are fine as long as they are used correctly.

GreenTrench
Jun 19, 2004

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dietcokefiend posted:


One of the contacts fused and somehow after the breaker was turned back on didn't make it trip again to turn off. Half of the insulation was gone and I got to inspect lots of holes in the carpet from the molted plastic that went flying

Any ideas what went wrong? Not really with the outlet... but with the breaker that allowed a shorted outlet to continue shorting? I replaced the outlet and house hasn't burnt down yet in the past four months. Old wiring is cloth stuff so guessing knob and tube and the saving grace was the metal junction box that made the wall not burst into flames.

You don't have a Federal Pacific panel, do you?

In any case, breakers do go bad after a few trips. It varies from manufacturer and from model number, but I was talking to a UL inspector who recommend that a breaker be replaced after five trips. I'd recommend replacing the breaker.

GreenTrench
Jun 19, 2004

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If you can put a main breaker on your panel, you could use
http://www.interlockkit.com/

Just be sure to use a holddown clip on your backfed breaker.

GreenTrench
Jun 19, 2004

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Hillridge posted:

Does anyone know where I can get a cheap kWh meter (like what you would have on the outside of your house)? I'm building a solar array and want to put one between the output of my inverter and my main panel so I can keep track of my production.

http://www.hialeahmeter.com/

They're utility grade.

GreenTrench
Jun 19, 2004

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Hillridge posted:

Another solar related question:

Can an AC disconnect be used with a DC system? In particular I want to use a GE THN3361R (30A/600V) to disconnect my panel voltage from my inverter.

Only if you wire two poles in series can you get the 600VDC rating. Otherwise, each pole is only listed for 250VDC.

GreenTrench
Jun 19, 2004

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babyeatingpsychopath posted:

Your ground must be in the same raceway as your current-carrying conductors. It can be solid or stranded, insulated or bare. If insulated, it must be green.

That said, parallel 10s? Two strings? #6 ground? Sounds very odd to me.

I'd run it in EMT with raintight fittings, using one-hole or two-hole straps to secure it to the roof. For a little more and much more secure, screw unistrut to the roof, then use strut straps for the EMT. Depends on how far you have to go. I'd recommend against a flexible conduit for anything over 15', because it'd be a cast-iron bitch to get wire in it.

The conduit has to be elevated a bit from the roof, or you'll create a dam.

GreenTrench
Jun 19, 2004

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babyeatingpsychopath posted:

I have a whole bunch of those in a bag somewhere. Lemme see if I can find a better nomenclature than "those waterproof SO cord connectors."

They're strain reliefs.

GreenTrench
Jun 19, 2004

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insta posted:

Hmm, well, since there's apparently not a rule against it ...

I've found dual NEMA 6-15 outlets, and NEMA 6-15 to IEC 320N power cables.

What're the rules for using normal 12/2ga wire? Just tape up the neutral to mark it as hot?

Technically, that's two code violations. One is not allowed to tape up wire that's smaller than #6, and a neutral is not allowed to be phased to hot. Someone some day might pick up that wire elsewhere and go "wow, that's white, it's a neutral! Let me splice in because it's a neutral...."

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GreenTrench
Jun 19, 2004

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dwoloz posted:


Also on grounding, code requires two grounds. One is usually the water and the other a ground rod

Technically, you only need one ground rod if you can show that the resistance to ground is less than 40 Ohms. Otherwise, you need to sink another ground rod in a minimum of 6' away. However, it's far easier to to sink another ground rod and that's why a lot of inspectors will always say drive two ground rods.

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