Reliability of Solid State Relays

gactrx
gactrx Solar Expert Posts: 72 ✭✭
in Wind Power Generation #1
Hi, would anyone know how reliable are SSR these days?
I'm looking at a Crydom 60 A Surface Mount, DC Switching MOSFET Solid State Relay, 32 V Mfr. Part No.D1D60.
Would it last 10 or 20 years? Are they very susceptible to voltage spikes? and would they be more or less reliable than a mercury displacement relay?
Thanks,
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    A big thing is to mount them on a good size metal heat sink... You don't want them to get hot.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • gactrx
    gactrx Solar Expert Posts: 72 ✭✭
    #3
    BB. wrote: »
    A big thing is to mount them on a good size metal heat sink... You don't want them to get hot.

    -Bill
    Thanks, yes I have some large heat sinks I can mount in good air flow. Anything else to make sure they last along time?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Besides heat and thermal cycling, lectronics can be easily damaged easily by static electricity... Dry weather, synthetic clothes can make static worse. Most devices like SSRs should be protected (internal design) against static discharge--But just be careful all the same.

    If you have lightning in the area--Having surge suppressors is always a good idea for all appliances.

    I don't know about SSR's specifically, but many electronic "devices" can fail open or shorted. Just making sure you that if there is a failure, that those failures don't cause worse problems...

    For example if the SSR fails shorted and it is used to power a water heater--Having a T&P safety valve (temperature and pressure) to prevent the tank from exploding is critical for safety.

    For well pumps, some people have put a small light connected to the motor that can be seen from the house--If the light is on too long/when not expected, the owner can out out and investigate (failed switch, leaking plumbing). You do not want your attempt to use a few dollars of extra power to cost you a few thousand dollars of battery bank killed by a stuck SSR draining the battery bank.

    For better for for worse--In California (and possibly much of the US), mercury wetted relays are probably nearly impossible to purchase (heavy metals).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #5
    SSrelays are incredibly reliable in some ways more so than mechanical relays as no arching across the contacts so no possibility of staying on when power turned off...You usually dont need a very large heatsink unless you are using it under continuous load close to its rated limit. To give example I have a water pump rated 11/2 hp and use a 40a one at 220v and no heatsink and after running about 30 mins is still at about ambient temp. Have never had one fail even no heatsink and high load.. They ok up to about 80deg C case temp..Never found one damaged by static electricity ..It may be possible it can happen but very unlikely.

    Mercury relays are bad in just about every way possible..If overloaded can heat the murcury to a temp to blow the glass and then.. mercury here there everywhere.. Should have been banned 50 yrs ago..Work ok for light duty like boot/trunk interior light on motor car.
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  • gactrx
    gactrx Solar Expert Posts: 72 ✭✭
    #6
    Thanks for your replies. I think I'll try the SSR's but hopefully I can find out if any particular sort fail open or fail closed. I need one of each. Open for hot water element, closed for dump load. I do also have a thermal trip on the hot water cylinder which is a vented to air low pressure type. A N/C 60A 100V DC SSR would be very useful to me if they make them. Generally I have only seen N/C.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #7
    I am not predicting they will fail (probably will never fail).... But you do need to protect against failures, just like we do with fuses and breakers.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • gactrx
    gactrx Solar Expert Posts: 72 ✭✭
    #8
    Yes, good point. I have secondary protection on my hot water cylinder but the wind generator is a problem. I'll be fitting surge arresters and have good earthing. I'll probably use HRC fuses on the system as well as lower rated circuit breakers.I think there are two types of arresters, spark gap and MOV. Midenite use the MOV which I think are the best but expensive.
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #9
    You will find all SSRs are N/O and close when supplied with 3 to 30v dc.. only a few ma of current needed to operate them.. .24 awg wire over almost any practical length on 12v dc . is fine...
    You just have to accept some things have such a low failure rate not worth worrying about.. Even a circuit breaker can fail.but what can you do in a practical way to overcome this problem?? nothing .. Lightning arrestors are something that usually are a waste of effort as the voltage/current just jumps across them. . Every test I have seen done with then ended in total failure.

    There is no SSR made that has a predictable fail in open or short circuit...
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  • Johann
    Johann Solar Expert Posts: 245 ✭✭✭
    #10
    How many watts are lost across an SSR? Since they tend to get warm, losses should be there.
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  • Ethan Brush
    Ethan Brush Solar Expert Posts: 235 ✭✭
    #11
    gactrx wrote: »
    Hi, would anyone know how reliable are SSR these days?
    I'm looking at a Crydom 60 A Surface Mount, DC Switching MOSFET Solid State Relay, 32 V Mfr. Part No.D1D60.
    Would it last 10 or 20 years? Are they very susceptible to voltage spikes? and would they be more or less reliable than a mercury displacement relay?
    Thanks,

    My understanding is they are very reliable. Here is a link to some further discussion. Rob Becker's used a crydom with good success to protect wind turbines, the link to his write up is in the page of the link I posted.

    http://midnitesolar.com/Forum/index.php?topic=1582.0
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #12
    Regarding how much power they dissapate... Here is one model:

    http://www.crydom.com/en/products/catalog/s1_dr_timer.pdf

    Max drop of 1.3 volts on AC unit, and 0.3 volts on DC unit. Rated at 6 amps:
    • 1.3 volts * 6 amps = 7.8 watts max (for AC unit)
    • 0.3 volts * 6 amps = 1.8 watts max (for DC unit)
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #13
    BBs figures are about correct.. Also the best one for DCis the one rated at 100a and 30vDC. With good size screw terminals. These are just about indestructible. I have used them in many situations. Including some where they were operated close to the current limit but never a failure and usually with very minimal heatsinking.,, they really beat mechanical relays in every area except initial cost.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #14
    john p wrote: »
    .....Mercury relays are bad in just about every way possible..If overloaded can heat the murcury to a temp to blow the glass and then.. mercury here there everywhere.. Should have been banned 50 yrs ago..Work ok for light duty like boot/trunk interior light on motor car.
    Wow ! I've never tried to overload one. My experience is they are the very best thing ever. also called Never Fail relays. But you have to stay within specs.

    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #15
    Mike thats the real problem.. If overloaded or even long term close to their limit and that happens for so many reasons. they are are big disaster. mercury is just so hard to get rid of. Whereas a mechanical or SSR usually will cause no damage to the surrounding area...I will never understand how you think they are good. mercury is hardly ever good... Thats why its banned almost everywhere for just about every use,, and rightly so..
    Drop on a concrete floor a mercury relay,a SSR and a mechanical relay. and see which gives the worst result.... Hint::::::it wont be the SSR..
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  • Johann
    Johann Solar Expert Posts: 245 ✭✭✭
    #16
    BB. wrote: »
    Regarding how much power they dissapate... Here is one model:

    http://www.crydom.com/en/products/catalog/s1_dr_timer.pdf

    Max drop of 1.3 volts on AC unit, and 0.3 volts on DC unit. Rated at 6 amps:
    • 1.3 volts * 6 amps = 7.8 watts max (for AC unit)
    • 0.3 volts * 6 amps = 1.8 watts max (for DC unit)

    -Bill

    Thank you for your response.
    I thought that losses would be way higher,
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #17
    Losses are small .Thats one thing that makes them so successful. and for most uses will require a small heatsink or mabe none at all....
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  • gactrx
    gactrx Solar Expert Posts: 72 ✭✭
    #18
    Hi, thanks for the information. I think I'll go ahead with the SSR's to switch water heating and dump load.
    Cheers,
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #19
    john p wrote: »
    Mike thats the real problem.. If overloaded or even long term close to their limit and that happens for so many reasons. they are are big disaster. mercury is just so hard to get rid of. Whereas a mechanical or SSR usually will cause no damage to the surrounding area...I will never understand how you think they are good. mercury is hardly ever good... Thats why its banned almost everywhere for just about every use,, and rightly so..
    Drop on a concrete floor a mercury relay,a SSR and a mechanical relay. and see which gives the worst result.... Hint::::::it wont be the SSR..

    Stay WITHIN specs I said. "Drop Testing" is not within spec. Just some relay wired in to some load, with some power source, not going to be in spec and you WILL have trouble. Try some static electricity on your SSR. Or have some fluctuating voltages on it - it works poorly. If mercury was really bad, why do greens insist on using fluorescent bulbs that contain it? Can't even get rid of dead tubes anymore, no body will take them but the haz household waste crew. Progress vs Posturing.
    I could go on about Lead free solder too, and it's failures but it's off topic.
    Mike - retired spacecraft electronics engineer .(used lead solder and mercury relays on DC busses all the time)

    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #20
    Mike just where is the static electricity going to come from in any "normal" mounting situation..???Just out of curiosity I tried to see if I could manage to damage one with static electricity of an intensity that could be found in a home..Rubbed plastic over a nylon carpet and discharged it into both the load and turn on/off terminals.. Tried just rubbing the device over nylon carpet itself. In an impractical test held it about 3" away from terminal of a spark plug on a running motor mower.. Still works fine... As for fluctuating voltage The only test could manage was on a variable power supply with range 3 to 52v manually controlled by a manual continuously variable control..It was connected to 2x24v 1/4 hp motors in series .. its all I had. .seemed to me to work ok.. All I can add is never had one fail under any condition yet and been using some for over 4 yrs.. I use 8 of them in my 2 vehicles.. for horns.,headlights and refrigerator.All are mounted in the engine bays. A harsher place is hard to find..
    I agree with you to some extent about lead free solder.... As for fluro tubes removed all of them from my house over 5 yrs ago.. Now house is almost all LED lights..much easier on the solar power system..
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  • vomus
    vomus Solar Expert Posts: 32 ✭✭
    #21
    Hi!
    I wonder whether anyone has seen a NC SSR rating at about 50A. Or even better, a double pole SSRs rating at a similar voltage.
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