Use SSRs to make change over relay?

XRingerXRinger Solar Expert Posts: 529 ✭✭✭
I have some parts in the mail.. Five Crydom D2425 Solid State Relays (240Vac 25Amp).

And, I'm thinking of making a change-over relay. It would work a bit like my
IOTA relays, but without the moving parts..

blockdiagram.jpg

The solid state change-over would be for 230vac, and would switch
the Sanyo mini-split (AC & Heat) to inverter power.
(The goal is to use solar to power the AC during sunny days).

Has anyone done this before? Are there products on the market that do
this kind of switching task using SSRs?

Thanks,
Rich

Comments

  • john pjohn p Solar Expert Posts: 814 ✭✭✭
    Re: Use SSRs to make change over relay?

    PROBLEMS
    solid state relays are single throw single pole:grr (on or off )
    NO solid state relays I know of can do double pole(changeover switching):grr
  • RCinFLARCinFLA Solar Expert Posts: 1,397 ✭✭✭✭
    Re: Use SSRs to make change over relay?

    You can do it with two SSR's.

    Your control has to be sure only one is activated at a time and you should allow about 20 msec gap delay time between changing states to ensure turn off time before other is activated.

    Remember there is about 1.5 volt drop across SSR so heat dissipation will be 1.5 X amps flowing through SSR. Make sure you provide sufficient heat sink.
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Use SSRs to make change over relay?
    RCinFLA wrote: »
    You can do it with two SSR's.

    Your control has to be sure only one is activated at a time and you should allow about 20 msec gap delay time between changing states to ensure turn off time before other is activated.

    Remember there is about 1.5 volt drop across SSR so heat dissipation will be 1.5 X amps flowing through SSR. Make sure you provide sufficient heat sink.

    I think these will only switch on (and off) at Zero Crossing, EDIT: I agree with your timing. 20 milliseconds will work okay.
    (Since the lines are not in phase, there could be problems if the open SSR being closed switched fast and the on SSR switched 15 milliseconds later).



    I've been using a couple of similar SSRs to feed my Sanyo and they have
    never warmed the heat sink above 60F.. These SSRs seem to run cool..
    http://i46.photobucket.com/albums/f147/Xringer/NCL/AB2011.jpg
  • john pjohn p Solar Expert Posts: 814 ✭✭✭
    Re: Use SSRs to make change over relay?

    RCin FLA you cant do a changeover with just 2 SSR,s
  • Paul54Paul54 Registered Users Posts: 18
    Re: Use SSRs to make change over relay?

    Xringer,
    I use the exact setup as in your picture, except I am using conventional relays. I got mine from Grainger. They are Omron brand if I'm not mistaken. The switch contacts are rated at 20 amps AC, a typical branch circuit amperage rating. The coils are AC, and are fed by my inverter, so that when I turn on the inverter it automatically switches the branch cicuits from grid to inverter. I have an occasional issue with the relays chattering when the inverter first fires up. I believe this is some kind of noise on the inverters part that goes away after a few seconds.

    I see that you are switching both the hot and neutral legs at the same time. In my system I had to do it that way which is why I went to an electro-mechanical relay. It was the cheapest way I could find to get Double Pole Double Throw switching. My inverter can not share its neutral with the grounded grid neutral. Be sure to check that your branch circuits are not sharing any hots or neutrals downstream of your main grid panel. Should not be a problem normally, but I have an older house that had a few issues and ended up damaging a couple of the relay coils, until I found the improperly shared neutrals and grounds. I recomend that if it is not a listed grid tie device, allways keep complete isolation of inverter or generator conductors from the grid power.

    I really like my system and the convenience of instant changes from inverter to grid. I do not run my inverter 24/7 but do use it daily.
  • Joe_BJoe_B Solar Expert Posts: 318 ✭✭✭✭✭✭
    Re: Use SSRs to make change over relay?

    Yes you can do it but it costs... http://www.power-io.com/products/cfamilydc.htm
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Use SSRs to make change over relay?

    I was planing on switching both sides of 230v, using 4 SSRs.

    solid-state-relay-SSR-75DA-H.jpg

    One side of the 230v load would connect to pin 1 on two SSRs (A&B).
    The other side of the 230v load would connect to pin 1 on other two SSRs (C&D).


    Pins A2 & C2 would connect to the grid's 230vac.
    Pins B2 & D2 would connect to the inverter's output.

    One pair on with the other pair off.
    A & C on= grid power.
    B & D on = inverter power.
  • Paul54Paul54 Registered Users Posts: 18
    Re: Use SSRs to make change over relay?

    OK. I think I see what you are trying to do. You want to switch 230/240 split phase power to the Sanyo. Four solid state relays should work since you will only be switching the 2 hot legs from either the grid or the inverter.

    A few things to be sure of: Can and does your inverter have its ground safely tied to your grid ground? You will need this since you are only switching the hot legs.

    Is there always a proper size circuit breaker in line with each source to protect the wiring to the AC unit?

    The way you will be switching the SSR's on and off has to be failure proof, so that at no time is it possible to have the inverter and the grid both feeding the AC unit, even for a fraction of a second, or be partially switching one leg from one source and one from another. Any mixing or missmatching could be disastrous.

    It looks like the SSR switch contacts are rated at 75 amps, but be sure to verify that the Sanyo's requirements can be safely switched by the particular relay you use.
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Use SSRs to make change over relay?

    That picture was just used as an example, I'm using 25A SSRs. (Crydom D2425 : See 1st post).
    I needed to refer to some pin numbers. I got 5 for $21 on Ebay. :cool:

    I will have the inverter ground tied permanently to ground line from the breaker box.
    The same way I did for the IOTA relays.
    http://ecorenovator.org/forum/solar-power/1360-solar-back-up-power-project.html

    The inverter that I'm thinking of using does not output "split phase power".
    It's just 230vac across the two hot lines. Which exactly what the Sanyo is looking for (on pins 5 & 6).
    http://i46.photobucket.com/albums/f147/Xringer/NCL/outdoor.jpg
    http://i46.photobucket.com/albums/f147/Xringer/NCL/F104.jpg
    Those ground lines on the left are for safety.

    I have a 9.5A breaker in the Sanyo line right now.
    http://i46.photobucket.com/albums/f147/Xringer/NCL/AB2011.jpg
    Since it's electronic, I could actually use this with the change-over, to add an extra layer of isolation from the grid.
    Funny, it's already 1/2 of a change-over relay.. :)
  • Paul54Paul54 Registered Users Posts: 18
    Re: Use SSRs to make change over relay?

    Looks good. I'm thinking about one, or more, of the Sanyo units to try and run off of solar. Right now I'm using an antique 30 year old power pig of an AC unit to cool way too much square footage all the time. I'd like to try cooling a few smaller areas with something more efficient.
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Use SSRs to make change over relay?

    There are some DIY mini-split blogs here..
    http://ecorenovator.org/forum/geothermal/

    Mine is here. http://ecorenovator.org/forum/geothermal/683-sanyo-24khs72-ac-hp-diy-install-project.html

    This technology is being used all over the world and is starting to become
    popular in the USA now.
    (I'm not the only guy on the street, with a mini-split anymore)..

    It is the perfect solution for retrofitting 1950s houses with baseboard heat.
    (No air vents installed).
    And prefect for your app, controlling cooling & heating in enclosed parts of your home.

    Had I known more about these systems, I would have likely gotten two units.
    A 9k BTU for my den(lots of glass) and the 18k or 24k BTU for the rest of the house..
  • nsaspooknsaspook Solar Expert Posts: 396 ✭✭✭
    Re: Use SSRs to make change over relay?

    That a great site, except the part about using R-290. :grr
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Use SSRs to make change over relay?
    nsaspook wrote: »
    That a great site, except the part about using R-290. :grr

    R-290? It's all part of the plan to reduce the earth's population.
    Less peeps means less pollution.. :roll:


    Anyways, now that it's April and the trees and the higher sun angle are
    starting to show me there really isn't any good locations for panels in the backyard,
    I'm starting to think maybe I should be flying my RC planes this summer and forget about doing solar stuff..
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Use SSRs to make change over relay?

    you had winter sun, but no spring or summer sun back there?:confused: that's unusual.
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Use SSRs to make change over relay?
    niel wrote: »
    you had winter sun, but no spring or summer sun back there?:confused: that's unusual.

    Now that the sun is much higher in the sky, those westerly over-hanging branches are making themselfs known..

    solarfarm2.jpg

    Maybe if my wife leaves me, I can put them on the roofs?? :roll:
    No, wait.. She would likely keep the house and send me packing.. :cry:

    Without a good site, solar isn't that great. Need more hours of sunshine.
    I'm thinking that a jumbo post mount in the middle of the backyard would
    be a lot better than under the dang trees..
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,030 ✭✭✭✭✭
    Re: Use SSRs to make change over relay?

    Rich, NICE ! Summer 8)
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • Paul54Paul54 Registered Users Posts: 18
    Re: Use SSRs to make change over relay?

    Chainsaw. Yeah that's the ticket.
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Use SSRs to make change over relay?
    Paul54 wrote: »
    Chainsaw. Yeah that's the ticket.

    We did a bunch of that already.. I have a tiny electric chainsaw on a pole.
    cyndee.jpg

    I made a limb cutter.. Call it ChainSaw-on-a-Rope..
    http://i46.photobucket.com/albums/f147/Xringer/Solar/achain.jpg
    http://i46.photobucket.com/albums/f147/Xringer/Solar/achainpinned.jpg

    Achainsaw.jpg

    Use the slingshot to shoot a fishline over a limb, haul up the chain and the limb
    is on it's way down in a few minutes.. :cool:
  • solarvicsolarvic Solar Expert Posts: 1,060 ✭✭✭✭
    Re: Use SSRs to make change over relay?

    You looking for a laugh at my expense? I finally figured what the ssr is that everyone was talking about on this thread. I was thinking you were talking about that specialty truck that Chevrolet built. Model was SSR. 8)solarvic8)
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Use SSRs to make change over relay?

    Hahaha! It's in the first line of the OP..

    Anyways, the 5 SSRs came in today. They look good, almost unused.

    Now, I need some spare time to work on the design..
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Use SSRs to make change over relay?

    xringer,
    seeing as you brought up the side subject of the cutting of the trees i would like to continue it somewhat. if you prefer not in the thread then you can pm me.

    i have a tree dilemma in my back yard. my backyard is basically a 10ft high cliff with a steep 30 degree uphill angle as it goes away from my home. there are some trees on that hillside that are in the neighborhood of 100-120ft high within 30-35ft from my house. these are too overwhelming for me to tackle and will need to either fall down or wait until i hit the lottery to pay somebody. there are smaller ones that i can and need to address though before they get too far out of hand. these smaller ones would be difficult to reach some of the top branches even with a 40ft ladder and are leaning towards the house to catch the sun's rays due to the larger ones shading. i fear any of them falling, but the smaller ones with their angle have a huge amount of weight that could easily tip and come down even though there is much bedrock there. they get bigger with each passing year too and i estimate the base is around 18-24 inches in diameter. (didn't measure)

    ok, that's the scenario and i thought of those chainsaw like things to throw over the limbs, but some points deterred me from buying it.
    1> getting the cutting surface to bite into it to get it started.
    2> figure out a way to unbind it should it get stuck

    i also thought of putting my small electric chainsaw on an extending pole, but balancing a chainsaw that is to constantly run on a pole that high (better than 30ft is needed) is dangerous. remember the safety switch needs to be defeated too and would be turned on/off via the ground level plug on the extension. that's bad enough, but i have to worry about where it will fall too as the trees are nearly touching the house now and i would also be directly underneath it when it would fall. ropes are good, but may fail and i can't hold them in addition to a saw.

    i am limited in what i can physically do and irregardless for safety reasons no ladders will be placed against any trees even if they would reach the branches. i did take out a few smaller trees that started growing, but they were the easy ones that had diameters under 6 inches. if need be i can take a pic of the situation from on the hill provided the weather starts cooperating and i remember how to upload the image.

    ps-these trees are somewhat inhibiting me from running my antennas on the hillside too as too many branches are falling, but i'll take my chances if i can weed out a few of them.
  • nsaspooknsaspook Solar Expert Posts: 396 ✭✭✭
    Re: Use SSRs to make change over relay?
    XRinger wrote: »
    Hahaha! It's in the first line of the OP..

    Anyways, the 5 SSRs came in today. They look good, almost unused.

    Now, I need some spare time to work on the design..

    I would add a hardwired fail-safe signal lockout to keep the legs on both sides of the transfer SSRs from being on at the same time. If you're using TTL level signals a 7486 on a small board should work. I have few SSRs here to make the same thing if your design works.

    http://focus.ti.com/lit/ds/symlink/sn7486.pdf

    XOR+Gate+truth+table+04116.png
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Use SSRs to make change over relay?

    Niel, Check out the reviews on this factory made model..
    http://www.amazon.com/High-Limb-CS-48-Rope-and-Chain-Saw/dp/B0000AX849/ref=sr_1_1?ie=UTF8&qid=1303942106&sr=8-1

    Those steel plates on the ends of the blade help a little, by dragging the
    chain downwards into the cutting posistion.
    And, if the chain is sitting on the limb backwards, you can usually use
    one or both ropes to flip it back over. I would just flip a loop in the line,
    yank it, and let it whip up to the chain and flip it over. (Bullwhip style?).

    Don't worry about starting to cut. It will dig right in to the limb.. Like a chain saw..

    Jamming was a real problem with my DIY high-limb saw. My chain has way
    too many teeth, making it extra hard to pull. So, it would dig in and jam.
    I would have to really yank on the 'easy' rope to get it loose.
    Once, I was so beat while messing with a jam, I quit and tried again the next morning.
    It started working fine again!

    We used a light angle to start up and get into the branch. My wife would take
    the easy rope, and I would pull on the hard rope, digging the blades in.
    If she held the rope firm at all, or walked towards me, too much chain would engage.
    She had to use a light hold, and stay back, as not to wrap the chain around the limb too much.
    If I had not purchased such and aggressive chain, it would have been easier.. :p

    If it jammed while she was pulling it back, I would just whip a flip up to
    the chain and it would lift out of the cut enough, she could pull it back a ways.
    We did most of our cuts in the 'Y' of a limb, so if the chain popped out,
    it was easy to get it back in the cut. But, if it made another cut, so be it.
    Two minutes later it's on the ground..

    Try it on a little stump at ground level to get the hang of it..
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Use SSRs to make change over relay?
    nsaspook wrote: »
    I would add a hardwired fail-safe signal lockout to keep the legs on both sides of the transfer SSRs from being on at the same time. If you're using TTL level signals a 7486 on a small board should work. I have few SSRs here to make the same thing if your design works.

    http://focus.ti.com/lit/ds/symlink/sn7486.pdf

    XOR+Gate+truth+table+04116.png


    I'm familiar with the XOR, used to teach computers.
    IIRC, "One or the other, but not both or neither" was the phrase used.

    I was thinking of designing dual triggers (one of each side of the 230 line).
    Four triggers total (with build in turn-on delays). The pairs would operate differently.

    SSRs 1 & 2 would trigger with a +5 input, and SSRs 3 & 4 would trigger with a ground (logic zero).

    Then, one single line could be used to control all 4 SSRs.
    +5 or logic 1=backup power
    0v or logic 0=grid power


    To generate that control line, I would AND the SOC with a signal from
    an AC current sensor. I don't want to turn on back-up, if the Sanyo is
    drawing over 500 watts. Just leave it on the grid until the Sanyo settles down.
  • nsaspooknsaspook Solar Expert Posts: 396 ✭✭✭
    Re: Use SSRs to make change over relay?

    Lets just say I'm paranoid from designing things in the past that you never want to trigger at the wrong time. I'm sure your delays and logic will work as designed.
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