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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.
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Mar 5, 2010 20:28
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GreenTrench posted:I hope you know what you're doing since installing a PV system is more complicated than most people think. 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.
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Mar 28, 2010 14:22
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What would you recommend for panels, and where should I buy them? I'm looking for the cheapest I can get that are still UL approved and not total crap. I have a 45'x15' area to mount them, so I can afford to trade more area to use cheaper lower wattage panels. I assume buying by the pallet will be the least expensive option per watt. Xantrex has a good system configuration tool on their website where you pick the panel and inverter and it tells you what output you'll get from X strings of Y panels.
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Mar 30, 2010 15:00
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So long as the panels meet UL1703, I can use them. From what I've see, all but the cheapest Chinese ones do. I'm going to try and buy non-Chinese if I can, though the cost difference may force me to do otherwise. I like Evergreen Solar, but their panels won't allow me to get to 5kW with my inverter. I'm not sure on which NEC is in effect here. My neighbor is a licensed electrician, and though I plan on doing most of the work myself, I'm going to hire him to help me make sure I build everything to code. I understand why you need to design to the record low, but it's still annoying because it hasn't been -34°F here in almost 100 years. Since you design systems, do you have accounts with any of the wholesalers? If so, could I buy through you rather than trying to convince them to sell to me? We can take this to PM if you want. Thanks for all the advice!
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Mar 31, 2010 12:07
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GreenTrench posted:Unfortunately I just switched to a company that does large scale systems. I get truckloads of panels straight from distributors. I haven't looked at racking yet, but I was thinking of using flatjacks as roof mounts since they are self flashing. Got any recommendations?
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Apr 1, 2010 16:37
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GreenTrench posted: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 like the way that system looks, but when I used their guide and clicked on engineering report I got this: The data you have entered for Wind and Snow loads is outside the acceptable range for this specification guide. The Wind Load must be equal to or below 120 mph. The Snow Load must be equal to or below 40 psf. You can use the Modify fields above if you feel the automatic lookup for these values is in error. It put in 60 psf for snow automatically. Does this mean I can't use their system in my area (NH)?
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Apr 2, 2010 18:01
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For those of you wondering about the need for GFCIs, we had a great demo at work where the instructor plugged a router (woodworking tool, not network equipment) into an extension cord, turned it on, then tossed it in a tub of water. It merrily ran with no issues. He then plugged it into a mini-extension cord with a built in GFCI, repeated the experiment, and it shut off the second it hit the water. This was supposed to show us the dangers of working around water without using GFCI circuits, but I also took away from it that routers will work under water.
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Apr 12, 2010 19:56
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I have these all over my house from where the previous owners switched from electric heat to gas. I think they used to be the thermostats. Also, instead of just removing the wires from the breakers and tying them out of the way, they cut them all so that none can be reconnected. So I have a useless 20A run to every room.
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Apr 12, 2010 21:14
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Mark Kidd posted:I'm going to quote myself here and say that as I think this over a bit more, it seems clear that this safety switch is designed to work with electronic thermostats. When the float is low the state is NOT normal, the switch is pressed in, and COM is connected to NO (Normally Open). When the float goes high, the switch is released, the state is normal, and COM connects to NC (Normally Closed/Connected) Here is a tutorial on building a switched outlet that can be driven by a micro: http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=119 For your application though, we can simplify it. You will need a relay that can handle 15A @120V. The control voltage isn't important, but try to keep it under under 24V. If you get one that switches at 9V or less, you could run this off of a 9V battery. Otherwise you will need a DC power supply. I'll assume a 9V battery for ease of explaining. 1. Connect +9V to the COM terminal of the switch on the pump. 2. Connect the NC terminal on the switch to one side of the coil on the relay. 3. Connect the other side of the coil to the - terminal on the battery. 4. Wire up the outlet as shown in the link I posted, but use the NC contact on the relay, not the NO! I added that bold bit, because the sparkfun project is designed to turn ON an outlet when the relay is energized. You will want to turn OFF the outlet. When the float goes high, the switch will turn on the relay, which breaks the connection between COM and NC on the relay and kills power to the outlet. Hillridge fucked around with this message at 16:27 on Apr 22, 2010 |
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Apr 22, 2010 16:22
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Quick mspaint: Load1 is the black wire from the power source. Load2 is the black wire to the controlled outlet. The diode isn't essential, but is a good idea. Hillridge fucked around with this message at 16:37 on Apr 22, 2010 |
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Apr 22, 2010 16:34
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babyeatingpsychopath posted:I think you've got the relay load contacts wired backwards. If the float is not normally high, then then NC will be on, so the relay will be on, so the contacts will be closed. You have NC on the relay controlling the load, so they'll be open if the float is down. That's the confusing bit. When the float goes up, the switch is released, so NC(sw) is shorted to COM(sw). This then energizes the coil, turning on the relay and breaking the connection between COM(relay) and NC(relay). you could reverse everything as well though, which may be safer. In one instance (the one I described), the relay is only powered when the float is high, so it saves power. The problem is that if your DC supply dies, the outlet will turn back on. The other way around wastes power but fails to outlet off.
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Apr 22, 2010 18:25
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Yeah, we're on the same page. I'd look for a SPDT relay (that one from spark fun is not a SPDT) since it will have both options and shouldn't cost any more than a SPST one. I'd say go with option 2. I don't like the idea of constantly wasting energy (roughly 1W with the relay from sparkfun), but I like things to fail safe. you may also be able to find a relay that consumes less power. A solid state relay would do it, but they cost a lot more. Hillridge fucked around with this message at 18:46 on Apr 22, 2010 |
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Apr 22, 2010 18:43
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Mark Kidd posted:Cool. I'd use one of these relays from digikey: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PB308-ND http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PB310-ND They are the same internals, just with different mounting and connector options, and a lot cheaper than the one you linked. They come in different voltages. Those two are 12V versions and only need 83mA of current to turn on. Use a 100mA supply just to be safe. A 1N4148 diode is super common, and for something like this you don't even really need it. If you have one laying around, use it, but I wouldn't buy one just for this.
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Apr 22, 2010 19:31
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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.
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Jun 24, 2010 15:44
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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.
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Jun 27, 2010 03:57
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Thanks for the ongoing help. I think I'll keep looking for one rated to 600VDC. My strings of panels could get to near 500V in extreme cold. I have another question related to this project. I need to connect the exposed USE-2 cables from the panels to 4x #10 THWN-2 wires and run them in conduit across the asphalt roof, and down the side of the house to the disconnect. I also need to run a #6 ground wire along the same path. What type of conduit should I use, and how should I secure it to the roof (20° slope, asphalt shingle)? Can I use flexible conduit or must it be rigid? Also, does the ground wire need to be run inside or outside of the conduit, and should it be solid or stranded, insulated or bare?
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Jun 28, 2010 15:07
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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. I'm still working on the details, but here is the plan so far: I have 26 panels arranged as two strings of 13 each. The conduit will carry 4 runs of #10 THWN-2 (+ and - for each string), along with a beefy #6 ground. The panels are grounded together and to the racks with bare #6, which is connected to stranded #6 for use in the conduit. This conduit goes across the roof and down the side of the house to a DC disconnect (most likely a HU361RB). The ground will tie to the chassis of the disconnect, then continue out to a ground rod driven into the earth near the disconnect. The two positive lines will go to the line side of the disconnect, then continue into the house to the inverter. The two negatives (unbroken) and a #10 ground also pass through to the inverter. The inverter ground is tied to the production meter and my main panel with #10 as well. I'm familiar with using EMT indoors, and with the watertight PVC based conduit, but I haven't used EMT with raintight fittings before. Are these a special part, or would most electrical supply stores carry them?
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Jun 28, 2010 20:41
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I'm using a Xantrex GT5, which is good for 5kW. I plan to backfeed a 30A breaker (with a meter in between the two) with it using #10. I should have posted this a bit ago, but here's my one line drawing: http://hillridge.net/SA/images/wiring.png
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Jun 29, 2010 03:05
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I started a thread for my solar project in case anyone is interested: http://forums.somethingawful.com/showthread.php?threadid=3324488 Please let me know if I'm doing anything dumb with the wiring.
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Jul 7, 2010 14:35
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What are the black connectors on the front of this box called? Click here for the full 1280x960 image.
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Jul 8, 2010 21:14
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Sorry, I should have worded that better. They are strain reliefs with wires passing through them, but they don't come with that box. I was wondering what to look for so I could buy them.
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Jul 8, 2010 21:39
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What is the proper way to combine ground wires outdoors? I have a few #6 (bare, 7 strand) grounds that need to be joined before they make it back to a junction box. On the one I did so far, I twisted them together to make them secure, then soldered them for an extra measure. Solder is legal in the NEC, so long as it isn't the sole method of bonding, but there must be a better way.
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Jul 18, 2010 12:04
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As  as that is, I don't think it's a good idea to try it out on my roof.Could I use these, and bolt them together and then to one of my support rails?  My setup looks like this: code:
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Jul 18, 2010 20:17
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I just got done showing the local electrical inspector my wiring for the solar panels, and as usual, it was someone else's work that they had complaints about. My existing wire to my water pipe is a #6 or #8 and needs to be a #4 to meet code. I have some #4 THHN, but it's not rated for outdoor use. Can I use it anyway since it is for a grounding electrode?
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Jul 22, 2010 19:02
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Is there a code legal way to convert old 2 prong outlets to 3 prong without running all new wiring? I haven't seen the circuits yet (visiting my grandma this weekend), but I assume there is no ground wire present. Are cheater plugs a bad idea? I think what prompted this is her getting a new toaster that has a ground plug.
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Aug 30, 2010 00:49
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Ah ok, that makes sense. GFCI do the sensing between hot and neutral, ignoring ground, right? So if the amount of current in the hot leg is greater than the amount in the neutral leg, the GFCI will assume some is returning to ground via an unwanted path and pop open the circuit. Can I use any GFCI, or is there one specifically for this application? For labeling can I use a P-touch label stuck to the wall by the outlet?
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Aug 30, 2010 03:37
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Good idea. I thought I had seen that question asked before, but couldn't remember the answer.
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Aug 31, 2010 19:06
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It turns out that even though most of my grandmother's outlets are two prong, the wire that was run to them included a bare ground, although it seemed to be smaller than the other conductors. Was this normal 40-50 years ago? I just wired in a new 3 prong like normal, with no need for a GFCI. I also had to fix another 3 prong that was put in when she had a sun room built a few years ago because the electrician had swapped hot and neutral. The outlet was grounded, but only because the metal box was grounded and the outlet was screwed into it. Is this legal, or should it have an actual ground wire as well?
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Sep 8, 2010 14:47
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I have another 2 prong to 3 prong conversion question. A friend is moving into an old house with 2 prongs. He knows he can add a GFCI to convert to 3 prong, but he is worried about using it for computer equipment without it being grounded (things like the case building up static charge and such). Is there a simple solution to this, like a certain type of power strip or a way to safely tie gnd to neutral so the case isn't just floating?
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Sep 17, 2010 04:38
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chedemefedeme posted:Whats the age of the home? I'm not licensed but that seems a bit odd to me. I'm not sure anyone would wire a residential central light to be 100% always on. If you've turned every switch around and cant get the light to turn off my instinct wants to say something may be going dangerously wrong. Someone else who sees these things on a regular basis should jump in here but could it possibly be something like a floating ground shorted to the hot somewhere going to that fixture? That seems out there but I really cant think of a situation that would legitimately be wired as "always on". I have a few always live ceiling fixtures, but I put them in to hang ceiling fans, so it was intentional. I'm not sure why someone would replace a fan with a light that they can't turn off though.
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Sep 20, 2010 12:59
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chedemefedeme posted:I'll ask this here instead of starting a new thread since this thread has slowed down a bit. When I bought the panels for my install, they were the cheapest, though I was getting the pallet price (26 panels total) and they sometimes have a minimum order, in my case 2 because the panels came 2 to a box. If this is just to mess around with and won't be mounted on your house or anything, you can save a few dozen cents a watt by getting the non-UL listed ones. Don't even think of using these for a permanent installation though. ----------------------------------- I also had a question: I want to switch to more energy efficient lighting in my home. I already have CF bulbs on a lot of the lights, but I have a lot of dimmers I want to keep. What's the best type of energy efficient lights to use with dimmer switches? I have both standard bulbs and 3 of those can style recessed ceiling flood lights that I want to replace. I also don't want to have to wait for them to warm up and brighten if possible.
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Mar 28, 2011 18:11
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I just saw your post at the top of the page a couple back. What do you think is better for the recessed can lights, the PAR30 or the E26? For reference, I think I have 75W incandescent bulbs in there right now.
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Mar 28, 2011 20:02
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I just moved into a space with 208 3-phase. If I have any equipment that's designed to work off of 240, do I need a separate transformer for each circuit, or can I run 208 to a sub-panel that converts to 240 and feeds multiple circuits? Any recommendations on this?
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May 11, 2011 14:53
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Motronic posted:Are you positive your equipment won't run on 208? I've only run across very very few things that need to be either 208 or 240 (high end and quite old UPSes....think nasty early 90's filing cabinet sided Lieberts). I really don't know right now. It's more of a "what-if" type question. I think most of our stuff is currently 120 anyway.
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May 11, 2011 21:06
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208V 3-Phase question: If I want to run all 3 phases to one area to create 3 different 120V circuits (say 1 lights, 2&3 outlets), does the neutral need to be sized differently (larger) than the 3 hot legs?
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Jun 3, 2011 13:38
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