Help With Breakers!

System
System Posts: 2,511 admin
in Advanced Solar Electric Technical Forum #1
Crewzer, Bill, et. als.:

I am having some problems finding the breakers/fuses I need (Cf. "Cable size and fuses", posted nov. 1st).

Since I do not have lots of money, and given that my system is a modest one, I do not want to buy "combiner boxes" or "enclosures". Hence, I am looking for breakers that can be installed as "stand alone" devices. I have sent two emails to the folks at NAWS but, so far, I have not received any answers.

Does anyone Know of that type of breakers or fuses and where I may buy them?

According to Crewzer and Bill (whose advise I respect), I will need one 20 amps (maybe 30 amps), one 60 or 40 amps; and one 70 amp, all DC rated.

I will appreciate any advise and recommendations!

Amilkar
Puerto Rico
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Comments

  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    #2
    Re: Help With Breakers!

    Hi Amlkar,

    Have a look on ebay.com at automotive fuses for the guys who pimp up there hi fi systems they have a selection of distribution blocks and f
    use blocks I used some 4 to 1 distribution blocks for my homemade combiners. There are also some cheap reset switches in the 60 100 amp range all are stand alone insulated units. Price is good ie cheap *mass market* Also look at midnightsolar baby box and Din Fitting DC fuses, NAWS stocks Midnight stuff. Heres a few ebay item numbers to get you looking Look up agu fuse holders and distribution bloacks


    180175486502 First eg. An agu fuse holder fully insulated stand alone excepts nice thick wires comes with free choice of fuse only $4.59 +post

    180175105829
    280168823476
    270182042195

    HTH
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  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    #3
    Re: Help With Breakers!

    This is my homemade combiner boxes made using Automotive Audio Distribution Blocks

    http://energistar.com/phpBB2/album_pic.php?pic_id=16&sid=e70f642efa5edd3ae1f8825b734ff785

    Easily allowed 35mm2 cable and plenty of room to double the individual PV wires The smalles AGU fuses available are 20 amp
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #4
    Re: Help With Breakers!

    One can't beat Square D's QO series of breakers ... DC rated for 50 volts and your amp range the little 2 gang boxes used for AC disconnects are cheap and perfect.

    Breaker and box can be had for 30 bucks at home depot.
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  • System2
    System2 Posts: 6,290 admin
    #5
    Re: Help With Breakers!

    Hi, Nig:

    Great!
    And thanks for the photo!
    But, how do you DISCONNECT the system (or any part of the system)?
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  • System2
    System2 Posts: 6,290 admin
    #6
    Re: Help With Breakers!
    Solar Guppy wrote: »
    One can't beat Square D's QO series of breakers ... DC rated for 50 volts and your amp range the little 2 gang boxes used for AC disconnects are cheap and perfect.

    Breaker and box can be had for 30 bucks at home depot.

    Guppie:

    Are you talking abbout the same "Square D QOU" sold at NAWS?
    If so, are they "cable in, cable out" breakers (In other words, "stand-alone", does not need racks or mount to be attached to.)?
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  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    #7
    Re: Help With Breakers!

    They were primarily combiners but added the fuses before the main feed gets to the C40 charge controllers, from Charge controllers to the DC 250 Xantrex Disconnect and two DC rated airpax black switches one for each controller

    See picture two switches either side at botton of Disconnect, one was wired in when picture was taken hence only one thinner red wire going tobatteries

    http://energistar.com/phpBB2/album_pic.php?pic_id=12&sid=4bc1fbdb8bf9547a67da4c95df50a35e

    I thought as you were on a budget these might do but SG suggestion at $30 seems the way togo, Im in Spain and UK DC switches are like Rocking Horse shonet to find and expensive
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  • System2
    System2 Posts: 6,290 admin
    #8
    Re: Help With Breakers!

    Hi:

    Your system is, well, a LOOOOT bigger than mine, but I think your recommendations are worth considering.
    Nevertheless, SG has not yet answered my questions, so I don't Know if Square D breakers are the kind of breakers I am looking for.

    Browsing the Web I found some stuff that seems promising (at "Blue Sea", systems for boats)

    By the way, why do you have two Delta arrestors? How did you wire them?
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
    Re: Help With Breakers!

    i'll answer for him. the qou are as you say, but the qo are for a breaker box. both have the same dc ratings so either configuration would be good to go depending on how you want to work with them.
    now the previous question of disconnects. simply use the breaker as a switch.
    does that help?
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #10
    Re: Help With Breakers!

    My recollection is that we recommnded Amilkar use a "36 V" system. The STC Vmp will be ~51 V, and the STC Voc will be >60 V. Since the Square D QO and QOU breakers are rated for 48 VDC, they are technically not appropriate for use between the PV array and the charge controller.

    However, since Amilkar is planning on a 24 V battery system (max voltage = ~30 V?), a "big" Square D QO/QOU breaker might be OK between the controller and the battery bank. But, I'm not sure about if the breaker's AIR (or AIC) rating is good enough.

    Amilkar: If NAWS isn't answering your e-mails, then other sources for DC breakers are www.solarseller.com and www.thesolar.biz. Also, please double check the DC voltage ratings for Blue Seas switches and brealers. I think the typical spec limit is 30 VDC.

    HTH,
    Jim / crewzer
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #11
    Re: Help With Breakers!

    you're right jim as that's just over the edge on the nec rules and ify otherwise too. you could go with the combiner boxes made for solar with breakers that could handle your needs, but will be at a higher premium if the link jim has provided doesn't help you find something.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #12
    Re: Help With Breakers!

    http://www.grainger.com/Grainger/items/1H245

    also on on eBay

    http://cgi.ebay.com/SQAURE-D-60-AMP-DISCONNECT-AIR-CONDITIONER-QO200TR_W0QQitemZ200169960380QQihZ010QQcategoryZ104232QQssPageNameZWDVWQQrdZ1QQcmdZViewItem


    Is a 60 amp disconnect box, will hold any of the QO style breakers , 15-100 amps, its about 15 bucks at home depot. Note this box comes with a 2 pole 60 amp switch, not breaker, you can also install two single pole breakers if you wish

    http://www.grainger.com/Grainger/items/1D239 single pole 30 amp breaker

    or eBay for 2 bucks

    http://cgi.ebay.com/Lot-of-3-Square-D-Breakers-Type-QO-20-30-amp-2-Pole-30_W0QQitemZ290176341860QQihZ019QQcategoryZ104232QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

    good to 50V dc
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #13
    Re: Help With Breakers!
    crewzer wrote: »
    My recollection is that we recommnded Amilkar use a "36 V" system. The STC Vmp will be ~51 V, and the STC Voc will be >60 V. Since the Square D QO and QOU breakers are rated for 48 VDC, they are technically not appropriate for use between the PV array and the charge controller.Jim / crewzer

    I disagree with your logic ...

    Air rating is full current at full voltage and being able to still break the connection.

    VOC is no current flow, a short of any type will drop the array voltage, likely to zero volts. Either case, the QO's air rating will never be even remotely tested.

    Nice thing about PV's, short them out and nothing happens as the potentional energy goes to close to zero volts at the maximum amps the panel can supply ( close to zero watts ), unlike a battery which is darn near unlimited.
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #14
    Re: Help With Breakers!

    The logic isn’t solely mine; it’s based on the NEC and on comments from John Wiles’ “Photovoltaic Power Systems and the 2005 National Electrical Code: Suggested Practices”:
    Square D has received a direct current (dc), UL listing for its standard QO residential branch circuit breakers. They can be used up to 48 volts (125% PV open-circuit voltage) and 70 amps dc. This limits their use to a 12-volt nominal system and a few 24-volt systems in hot climates . The AIR is 5,000 amps, so a current-limiting fuse (RK5 or RK1 type) must be used when they are connected on a battery system [690.71(C)].
    Personally, I don’t entirely agree with the “125% PV open-circuit voltage” comment. I do agree that the NEC temp correction factors from NEC 690.7 need to be applied to STC Voc, but 125% is pretty far along the scale.

    Either way, the electrical characteristics (Vmp, Voc) of Amilkar’s proposed 36 V array exceed the 48 VDC maximum rating of the Square D QU/QOU circuit breakers.

    Regards,
    Jim / crewzer
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #15
    Re: Help With Breakers!

    Ratings are based on phyical limits, in this case the limit is the arc rating of the breaker device. Solar panels don't fit this well as at the maximum voltage, there is no current, for all other applications, arc rating is based on maximum voltage and maximum current does make sense which how the breaker manufactures test/list.

    There is absolutly no safety issue using QO's for solar panels as its impossible to exceed the arc rating of the breaker. Outback has dealt with this and have I have read paid to have the voltage rating extended for breakers they sell based on this ( voc , no current ) ... nothing changes except some label.

    The breaker manufactures have NO incentive to rate for example QO's the vmp for solar panel applications ( about 78% of VOC ), when they can sell another, already listed part for 5X more. Its all about money, not safety.

    As for the NEC 125%, that's nuts ... at 0.6% per C, the solar panel would have to be at -40C
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #16
    Re: Help With Breakers!

    Both OutBack and MidNite solar did indeed get their breakers rerated at voltages higher (150 VDC) than the OEM spec (125 VDC). But, those are CDI DC breakers (now polarized, BTW), not rerated Square D AC breakers (unpolarized), and they were actually tested at the higher voltage. I for one have no idea how much above 48 VDC the Square D breakers were tested.

    I agree that the DC breakers cost more than otherwise similar AC breakers. But, compared to the cost of PV modules, controllers, inverters, and batteries, I personally consider the marginal cost of the DC breakers to be minor.

    Believe it or not, I probably agree that the Square D breakers are likely safe to use in Amilkar's system. I successfully used Square D QO breakers and boxes in my early 24 V / 12 V system. But, his array voltage exceeds the breakers' DC voltage spec, so I won't recommend them.

    Regards,
    Jim / crewzer
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  • System2
    System2 Posts: 6,290 admin
    #17
    Re: Help With Breakers!

    PLEASE, HOLD YOUR HORSES!

    This is all too much for me!

    I am a professor of logic at the Interamerican University of Puerto Rico, so I like to keep things SIMPLE.

    Now, It seems Square D QOU are just NOT right for my panels (between panels and MX60) but are OK between MX60 and batteries. WHY?????

    Again, regarding Blue Sea switches, well, the guys at conductor@bluesea.com never answered my emails (is this some kind of illness?) [Obviously, I planned to use their switches, because they are inexpensive and, I think, very useful. But since I don't know if they fit...]

    Between batteries and Inverter I have chosen the cfb 110T 110 amp fuse sold at NAWS which, I think, conforms to all recommendations given to me.

    If anyone has more insights, they will be appreciated.

    Thanks again.
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  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    #18
    Re: Help With Breakers!

    Your MX60 has the abilty to accept a higher imput voltage from the PV array and output at the lower correct voltage for your battery bank. Wiring yor PV array as reccomended could technically go higher than the listed 48 volts spec of thes breakers and thus Creezer would not reccomend and I suspect would not pass any of your NEC inspection. From the MX 60 to the batteries the output voltage is regulated by the MX and will not exceed the 48 volt spec therefore suitable and are probably code friendly. Solar Guppy however brings the specific physics and electrical properties of PVs to the table which the original breaker manufacturer was probably not concerned with when he rated this type of breaker. Mixed in with this is the world of bussiness and profit and other breakers the manufacturer can rate for pvs then charge more 4.
    You have to say both are right, Creezer for not going against code or specs
    SG for practical application and saving you money without compromising safety, I doubt anyone here or anywhere could punch a hole in what SG is saying. HTH
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #19
    Re: Help With Breakers!

    Amilkar,

    Square D breakers and load centers are usually available from Home Depot or Lowe's. CDI breakers used by OutBack and MidNite Solar are available from NAWS, www.thesolar.biz , and perhaps directly from MidNite Solar.

    See: http://www.midnitesolar.com/CircuitBreakerPrices1.pdf
    and: http://www.midnitesolar.com/Price_sheet_April1_2007.pdf

    HTH,
    Jim / crewzer
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