System Disconnects

[WStayton]

Hi. Guys!

  Since we had such a ruckus when I stuck something about disconnect's in somebody elese's thread, I though it would be better if I started my own, and then had my own messes to contend with!  <grin>

  This subject didn't fit anwhere, exactly, so I sort of "came-close" by putting it in the ST generator section - if an op thinks it is better elsewhere, by all means, move it!  (NOT to the trash can, please!!! <grin>)

I need two (2) disconnects – one on the incoming 120/240 line, which I am required to have so that I can get the tax benefits for being grid connected, and one on the output line from the 24 kW ST Generator that I have just acquired.

  The disconnect on the 120/240 incoming line is so that I can "unhook" myself from the grid during those time periods when I won't need to sell power to NYSEG, which would be during the entire winter and during the night in the summer time – unless somebody comes up with some "moonlight" solar panels!  <grin>

  My reason for disconnecting from the "mains" is slightly (well, some would say "very", but I don't listen to them!  <smile>) paranoid in that the only reason for having the disconnect is to ensure that if there is some sort of EMP event, be it solar or man made, I won't be an immediate victim!  With this reason in mind, I think that a magnetic contactor is quite possibly not enough protection in that, when open, the gap between the contacts is relatively small and could be readily jumped by a massive EMP induced pulse.  For that reason, and because I firmly believe in KISS, I think I am best served by a simple knife switch,  appropriately UL rated and certified for 124/240 volt usage, in that when it is open, a spark would have to jump something like an inch to harm anything not a .tenth of an inch, or less, as there is in a contactor.  Knife switches are pricier than I thought they would be, but they are still cheaper than a magnetic contactor, and, they don't draw ANY current from anything, EVER!  <grin>

  For the disconnect from the generator, I just need something that will absolutely, positively, ensure that I don't have a load on the generator at shut down and thus fry the AVR and demagnetise the field coils.

  The generator will have a split output, going to the Xantrex 120 amp inverter/100 amp battery charger, which feed the batteries and the 120/240 outlets allocated to it, (due in Monday – I'm like a kid at Christmas!  <grin>) on one " leg" of the split and going to an auxiliary electrical panel to run things that I don't feel that the Xantrex is appropriate/capable for/of – think welder, etc., etc.

  For this purpose, just about any contactor will do the job, but again, from the KISS standpoint and the not-using-any-juice standpoint AND the cost standpoint, the knife switch wins again. 

  Switching these things off and on will be a PITA, but the mains one will get closed once a day and  then opened once a day, in the summer time, and it will be opened in the fall and closed in the spring.  The generator one will be cycled, at the most, twice a week, in the winter time – I hope!  It is my plan to use the generator to top up the batteries in the winter when the solar panels aren't up to the job, both due to cloud cover and day length.  I'm planning for this to be done every three days, but if that isn't enough, I can do it as often as necessary, like once a day.  The batteries are/will-be two sets of eight ( each six (6) volt golf cart batteries of 186 rated amp hours capacity – my intention is to NOT pull them down to less than 50%, EVER!!!!  So, I will be watching like a hawk the first winter to figure out just what my need to recharge is.  Oh, and the "machinery room" is right beside the most direct pathway into/out-of the dwelling, so I have to walk right by it to leave the premises, so I THINK I will be self-disciplined enough to take the two minute side trip to "flick the switch"! <grin>

  Realistically, I don't ever expect to need the mains disconnect switch, but to have it and not need it, isn't big deal – to NOT have it and need it is a VERY big deal, indeed!

  So, that's the plan – what do you think, guys?  Am I building a battleship to carry a couple of hamsters or is this a reasonable way to go?  Critique/criticisms are hereby solicited!

Regardz,

Wayne Stayton

[WStayton]

Hi Guys!

I forgot something - yea, even with my 5,000 word essay, I left something out!  <grin>

  The disconnect for the incoming power will be a three pole/knife unit, so that I can disconnect the neutral to be absolutely sure that there ain't nothing coming in when the switch is open.  This previous omission was pointed out to me by rcavictim - thanx for the heads up!

  Thats it!  Omission corrected!

Regardz,

Wayne Stayton

[Tom Reed]

Wayne, are you aware that the Xantrex inverter has an internal transfer switch that IIRC can be programmed for time of day operation? I believe battery voltage is also a possible parameter.

Also you might be surprised how much those panels will produce in the winter. The cold really increases there output. Our 3.4 kw array will fully support our household usage on the winter solstice if the weather is clear.

[WStayton]

Tom;

  I'm expecting to have a system somewhere between 3.28 kW and 4.1 kW which is either 16 or 20 each 205 watt panels. And you think that I MAY be all right without the generator???  That would be sort of good-news/bad-news!  Good news in that I won't/don't need a generator, bad news in that I have already spent the money for the ST generator and the engine(s) to drive it and it is sitting in the equipment room awaiting the influx of the other pieces/parts! <grin>

  I need the "waste" heat from the generator to help heat the building, so I will have to find a load for the generator if the batteries don't require the generator!

  Gee, you have just thrown a wrench into my carefully laid plans!  <grin>

  But you do have the "if the weather is clear." caveat, in there, and hear, in the New York grunge, we get about twenty percent of the days in the winter that are clear to scattered sky conditions

  Thanx for the input - it IS good to hear from somebody who has already done it and had it work!

Regardz,

Wayne Stayton

[WStayton]

Tom;

You say: "Xantrex inverter has an internal transfer switch that IIRC can be programmed for time of day operation."

Are you proposing that I use this switch to replace the system isolation from the net, three pole switch, or the generator isloation switch?

I THINK it is probably not big enough to handle the full 200 amps of the service to eliminate the sytem isolation switch and it has, Iwould think, the problem of having a very small air gap when it is open - if I replace the system isolation switch with the Xantrex internal on, and there is and EMP event, and a spark jumps the small gap in the internal switch, I will have succeded in being 100% WRONG!

For the generator isolation, I would think that the internal switch in the Xantrex woulod not be a good idea, since I would think that its transfer times would be set into the unit and if I was runninng late one day, and still had the generator operational when the Xantrex pulled the plug, I would, AGAIN, have been exactly 100% unsuccesful in doing what I want to do - which is ensure that I don't shut down under load!

Don't THINK that the Xantrex internal switch is going to help in this case, but I better go read the manual and make sure - when I get it on Monday!!

  Thanx for the input - it shows that somebody, at least, is thinking, out there!  <grin>

Regardz,

Wayne Stayton

[BioHazard]

I don't know if you saw it in the other thread but I still like the idea of using 100 amp fuses. Just pull them out and have an absolutely positive disconnect with a couple inch gap. Fuse holder is a bit over $20 at surplus center. Keep extra fuses on hand....

[rcavictim]

Wayne,

Here is a good simple, low cost knife switch for ya' !    The actuator may have to be replaced frequently... YMMV, but the contact replacements are common.

[highwater]

http://www.surpluscenter.com/item.asp?item=11-2012-B&catname=electric

I got a hand full of these the last time I ordered from SC.

Very heavy and the 2 wire terminals will bring 2.49US these days.

I would have no problem putting 100 amp fuses in them.

Randall

[highwater]

OR.........
using them as a base for a DIY knife switch

Randall

[BioHazard]

I posted these in the other thread:
http://www.surpluscenter.com/item.asp?item=11-2485&catname=electric

[WStayton]

rcavictim:

  That picture look suspiciously like me when i was about three - right down to the blond hair and the fingers into everything!!!

  Alas, the blond hair has been largely replaced by a shiny pate and I hope that I am more circumspect about what I put my fingers into these days!  <grin>

  As for using one as a "disconnect", I THINK that the bag limit on children is pretty restricted these days!  However, judging by many that I see these days, this MIGHT be a higher and better use for them than what their parents are doing now!!!!

  I DO like your tongue-in-cheek humor!!!  (That IS humor, isn't it??? <grin>)

BioHazard:

  I DO like the price tag of using fuses as an "interrupter", however I do have ONE problem - my strokes/min-strokes have left my dexterity sort of compromised and I am concerned that setting up something that takes a reasonable amount of dexterity to operate, by somebody who is dexterity impaired, I might be building my own version of the "electric chair"!  <grin>

  I probably am, again, concerned about a problem that doesn't exist, but getting electrocuted IS a one time experience - if the last one that you have!

  So, with my concern(s) in mind, how does one extract the fuses from the fuse holder without putting yourself at danger IF there is current flowing through the fuses at the time of disconnect??  Yea, I know, there isn't SUPPOSED to be any current present when you are opening the circuit, but if something bad can happen, it WILL!

highwater:

   Well, I need 100 amps, but I guess it is probably possible to put a 100 amp fuse into an 80 amp holder - with the right tools! (Read:  a big enough hammer!!!)  but I still have the dexterity-impaired-how-to-open-hot-switch that I expressed in my comment to  Biohazard.  I would much rather spend an extra $20 or $30 for something that is easily openable then spend a couple thousand dollars on a casket!  <grin>

I have one other thought - since I will have to have the whole installation inspected by the local code inspector - who, so far at least, seems to be pretty reasonable to work with - but does the fuse holder meet code for a circuit interrupter?  I'm not sure if this is really an issue, if you are putting something in the circuit that isn't required by code and it meets UL, I SUPPOSE it is good to go, but I would hate to get it all in and then have to take it all out!


Thanx for the ideas, guys - you ARE making me think about the problem in a slightly different dimension - or in rcavictim's case, a VASTLY different dimension!  <grin>

As always, thanx, everybody, for your input!!!

Regardz,

Wayne Stayton

[rcavictim]

Yes Wayne,  I employ a lot of tongue-in-cheek, or in this case knife-in-wall-socket humor in my day-to- day routine.    That picture accurately depicts an incident I created also when I was about the same age. 

I need high voltage (up to 480 VAC) disconnects around here in my off-grid system for genset and wind turbine isolation and have decided to go with big assed 3-phase circuit breakers.  I just picked up a nice 225 amp, 600 VAC, 3-phase magnetic trip breaker at a e-waste recycling center yesterday for about $5.  Looks like new.  Years ago I stripped out two complete mid 50's, RCA BTA10K, 10 kW AM broadcast transmitters. They contained a real wealth of electronic tube type parts for making DIY stuff including tesla coils and high powered hi-fi tube amps.  Out of them I scored four identical 100 amp, 600 VAC, 3-phase magnetic trip breakers.  I plan to use them as disconnects.  These are huge bakelite black boxes around 12"H x 4" thick x 9" W.  The trip point on all of these is screw driver adjustable individually per phase.

The fuse holder idea works in theory but as you point out in practise has real safety issues.  You can buy a special wrench that is made of insulated material and grabs the fuse so you don't have to pry it out awkwardly with a srewdriver.

I like the fused pullouts myself but only have a couple of 2 pole 60 amp units in stock.  They must make a 100 amp 3 pole for 3-phase circuits.  That may be your best option! IMHO.

[BioHazard]

This isn't the correct tool for the "big" fuses, but I'm sure they make ones for them too:
http://www.homedepot.com/h_d1/N-5yc1v/R-202259324/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

I also have a pair of needle nose and linemans pliers that are electrically insulated, made to be used with live wires.

but getting electrocuted IS a one time experience

ONE time? LOL, I wish! Maybe that's why my ears ring...

[rcavictim]

A three phase circuit with three separate single phase breakers and not having all the handles tied together to act as one would not pass code as far as I know.  For the same reason and some others I would add for safety's sake,  separate fuses would fail the same inspection if intended as a disconnect.

[BioHazard]

I'm not sure how much you want to spend, but ebay prices aren't bad on 3 phase 100 amp enclosed safety switches:
http://cgi.ebay.com/219-ITE-Siemens-100-AMP-3-Phase-Safety-Switch-GNF323-/150611123961?pt=LH_DefaultDomain_0&hash=item23111f5ef9
http://cgi.ebay.com/240v-disconnect-fused-100-amp-3-phase-safety-switch-/350459253060?pt=LH_DefaultDomain_0&hash=item5198ffd144
http://cgi.ebay.com/927-HU363-Square-D-Disconnect-100-AMP-600-V-3-Phase-/150611125289?pt=LH_DefaultDomain_0&hash=item23111f6429

You could also use a giant pin and sleeve connector to simply "plug in" your generator when you're using it and pull the plug when you're not.