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Sleeping Bear
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# Posted: 18 Feb 2015 10:32
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I have worked out the system that I plan to use to run my water pump in my rainwater harvesting system (1700 gal. tank). Could some of you Electrical/Solar types look at it and let me know if I have missed something. I have not shown the lightning arrestors but will be adding them. This will be a stand alone system seperate from the others.
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MtnDon
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# Posted: 18 Feb 2015 10:56
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From my first look I have three comments.
1. I find the inclusion of a + sign at each end of the breakers confusing. They come with a + at one end for a reason and that is to indicate which way the current must flow for the breaker to operate properly. They seem to be oriented properly, just that the double = in not correct.
2. Is the 175 amp inverter main breaker approved for a two wire connection as illustrated? I don't know; just asking.
3. Nice drawing; much better than the back of an old envelope. 
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Sleeping Bear
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# Posted: 18 Feb 2015 11:03
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Thanks MtnDon, Sorry for the confusion but what you see that looks like a plus sign is actually suppose to be a phillips head screw. I can see where that is confusing. I am going by what I was told by Backwoods Solar on the Disconnect, I'll have to investigate that further. I have been a Mechanical Designer for over 30 years so making drawings is my life. Thanks for the comments
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MtnDon
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# Posted: 18 Feb 2015 14:36 - Edited by: MtnDon
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That explains it. I don't recall seeing many breaker or buss connections with a Phillips head screw so that never entered my mind.
That big breaker is made in both back mount (stud) and front mount styles I believe. It's made by Carling Switch. If that is the Midnite MNEDC175 you can find a much better price at NAWS. They sell it in the stud mount version. The stud mount would be no problem for two wires using terminals on each wire.
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Sleeping Bear
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# Posted: 18 Feb 2015 14:47
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I really didn't think that it was right either but that Is the way it was shown in the manual I found on the Internet I think it might really be A blade type screw.
Thanks for the heads up on NAWS.
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Steve_S
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# Posted: 18 Feb 2015 16:06
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Great Diagram ! Picture is worth 1000 words isn't it. I am wondering, you are looking at using a Modified Sinewave inverter for this install. Is this strictly for your pumping arrangement or do you intend anything more for it ?
If you have intentions for other uses of this power, you should very seriously consider Pure Sine wave especially for electronics which is quite intolerant of Mod or Square wave. I saw on the Grundfos site in one of their myriad of docs that they suggested Pure Sine as well, as it results in better pump performance.
Lastly, battery location: I have no idea where you are but is there a need to consider temperatures ? If subject to potential freezing or extreme heat, the life expectancy of the batteries & failure rates will certainly be affected. (this is one of my biggest issues as temps swing from -35 to +35C (-31 to +95F).
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MtnDon
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# Posted: 18 Feb 2015 17:12
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Steve makes an excellent point on the inverter type and I completely zoned out it. Any AC motor runs hotter on mod wavw than it does on pure sine wave. Not only does the heat mean the motor may fail earlier but it wastes energy, not a good thing to do with hard earned solar watts, as a rule.
Grunfoss makes some really nice efficient pumps. Albeit not cheaply.
The temperature swings will more or less average out, the lows making life longer as long as they don't freeze while the heat will shorten life.
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creeky
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# Posted: 18 Feb 2015 18:15
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Can I ask why you're using an ac deep well pump?
You're not pumping from a deep well. You're pumping from a rainwater tank. So there's a lot of lift somewhere?
A much smaller system with DC pump might work just as well (pun intended)? And eliminate some of the redundancy. Even a small dc pump could give you 10 gpm.
Just a thought.
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Just
Member
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# Posted: 18 Feb 2015 20:26
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I'm with creeky , greet drawing but,' more ' than most folks would need .
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Sleeping Bear
Member
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# Posted: 19 Feb 2015 10:47
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I have a dc pump now in a cistern system and it just does not work like I would like it too. I know this system is overkill. I want a reliable system that works the way i feel it should and I don't have to worry about wether or not it will be enough. I don't get to spend as much time at my cabin as it is since it is in Pensylvania and I am in Texas. I would also like to branch off of it someday later for other uses.
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Just
Member
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# Posted: 19 Feb 2015 19:46
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you could first try adding a 30 gal. sealed bladder pressure tank to your dc system .It will greatly improve a pressure switch only system ,Quoting: Sleeping Bear dc pump now
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Sleeping Bear
Member
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# Posted: 20 Feb 2015 07:19
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The system has a 30 gal pressure tank now. My problem is with how long the pump runs and the drain on the battery bank. I have tried everything from shortening the wire runs, increasing the wire size, decreasing the set pressure, the system just does not run efficiently enough for me. In the past ten years I have not had to run a generator once to charge a battery but the pump has come close on many occasions to making that neccessary.
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razmichael
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# Posted: 20 Feb 2015 08:31
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If you are thinking about expanding this system later then now might be a good time to consider other potential uses and design accordingly. Some things can easily be upgraded and others cannot.
I'm not sure if your current plan will actually help with your concern. Why do you assume your DC pump is less efficient than a 120? Run time may or may not really make a difference (less power for longer time = more power for shorter time). I fully realize that this is very simplistic and things like voltage drop have an impact, but so does using an inverter that will likely be only 90% efficient at the best of times (not to mention idle draw that may or may not have an impact depending on the type of inverter).
IMO (and it is just an opinion), building this 120VAC system just to power a pump is not the best way to go - costly, not likely more efficient and more things to go wrong. If you want a 120VAC system for other things then you should design it for the other things - I would still consider keeping the pump at 12V. Many of the smaller systems we all have are hybrid - pumps, lights and others at 12VDC with some 120VAC circuits for running appliances when needed. Again - this all depends on your overall plan on how to wire the cabin. Maybe you need to just upgrade the pump or take a closer look at the plumbing method? I have no idea how much you use your water but I do know that I run my cabin (two sinks, shower, hot water) with a 12 volt marine pump without any significant hit on my batteries (two 6v T-105s) and no pressure tank.
Standard disclaimer - just my opinion and based on how we "do business"
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Just
Member
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# Posted: 20 Feb 2015 08:57
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Quoting: Sleeping Bear The system has a 30 gal pressure tank now. My problem is with how long the pump runs and the drain on the battery bank.
Sounds like you have been down the road . The new system you have designed may be overbuilt but I can understand your frustration .
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creeky
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# Posted: 20 Feb 2015 09:39
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a dc pump should be 3 times more efficient than an ac pump. maybe you could look into getting a new pump. pumps don't last forever, maybe your pump is getting to the end of it's life?
and add a larger battery bank and a bit more solar to the equation?
your drain on the batteries is going to increase with an ac pump and inverter overhead.
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