DC SSR size?

[kauaisolarman]

i am using the same aux 2 PWM signal to switch

I think if you contact the SSR Mfg, they will say you CANNOT use pulse mode as a trigger.
You can use DC on and off, but not PWM, that will quickly violate the specs, and they will burn up.

thanks for the input.   is that only for DC SSR?   my AC SSR is working great using the same AUX 2 pwm as the trigger.

when i try with the DC SSR it just fails, but, i have tried to hook everything up and just turn on the 12V trigger manually (no PWM) to test if the relay would just turn on and off manually and it will only work until the SSR starts to overheat.

so basically i hook up the SSR and turn on the 12V switch manually (no PWM) and the load current flows through the SSR, but it starts to get extremely hot (NO PWM just constant on) until it cannot manually turn off anymore.  so when i switch AUX 2 from manual on to manual off after the relay gets hot it will not turn off anymore just stays on all the time. 

thats with a 100A heat sink connected to a KYOTTO 75A SSR with only 47A running through the element. 

[kauaisolarman]

here is a diagram of how i have this wired

only thing different is instead of the 63A breakers i am actually running 40A breakers



what wrong with that?

[Vic]

Hi Kauai..,

What is the exact part number of the DC SSR that you are using?  Do you have a Link to the manufacturer's spec sheet?

What is the manufacturer of the Heat Sink used with the DC SSR, and any part number or spec sheet Link for that?

There are specifications for the SSR Temp Rise for various load currents.   The heat sink will also have specs.

Normally,  one would use a conductive grease or Silpad (tm) between the SSR and the heat sink.   The heat sink should be mounted with the fins vertical,  for maximum convection cooling.   A fan may be necessary for adequate cooling of the heat sink.

Since you noted that manually operating the DC SSR without PWMing it,  that it seemed to get excessively hot,  it implies that either the heatsink is inadequate,   excessively high ambient temperatures,  improper heatsink mounting/orientation,  or the DC SSR is perhaps defective,   is a reject or a fake ...   and so on.

There appears to be no clamp diode in your schematic,    which could cause the SSR to fail due to excessive voltage when the SSR is turned off ...   although in manual mode this may not have been the case.

In manual mode,   when the SSR gets excessively hot,   and cannot be turned off by the trigger input,   has that DC SSR been damaged,  and will never again work,  or  does it recover when allowed to cool to room temperature?

Major brand DC SSRs appear to not be made in 75,  or 100 A models ...  perhaps there is a reason for this.

Thanks,   Vic

[ClassicCrazy]

I found the specs for his SSR Vic
http://www.kyotto.com/eng_KG20.htm

Wonder what the exact PWM timing is set up for on his AUX.

Larry

[CDN-VT]

here is a diagram of how i have this wired

only thing different is instead of the 63A breakers i am actually running 40A breakers



what wrong with that?

Everything !!!!!!!!!!!!!!
Load of heater 1
SSR is NOT to be used as a relay of just on off 2
do a real PRINT & USE ONLY WIRE SCHEMATICS , PIX OF STUFF i CAN'T SEE OR READ IS JUNK.

There needs to be a level ___________________ standard to ask .

I'm not guessing what was posted !!
DUH

VT

we will help , but Be precise  rather than waste our time extracting !!!!  DUH !!!
VT

[ClassicCrazy]

What kind of thermostat is that in the AUX control line ? Is it a built in one on the water heater ?
Maybe you should try taking that out of line and see if your relay still heats up.  Just thinking that if it is standard built in AC type it may not work right on DC. Not sure what is inside of those -- if they are just a simple switch or if they do some other stuff too with the AC.

I think his pictorial schematic is just fine - no problems reading it here.

Larry

[Vic]

I found the specs for his SSR Vic
http://www.kyotto.com/eng_KG20.htm

Wonder what the exact PWM timing is set up for on his AUX.
Larry

Hi Larry,  Thanks ...

First,  it is always very good to know EXACTLY what part we are talking about,  so that part number would help make sure that we are speaking apples-to-apples.

YES,  did find those "specs",  which are horribly incomplete,  and I hope are wrong  --  the turn-off time is speced as "less (than) 1/2 AC Cycle"   for this supposed DC SSR ...   although  I do not know what they mean by referring to it as a DC DC SSR.

We really need some specs on temperature rise verses current,   and heatsink area,  pulse duration verses current,   any rep-rate limitations or curves,  etc.

This DC SSR appears to be very inexpensive,   and perhaps is not for serious users,  a knock-off,  reject,   ...  or ...

It is difficult to try to do Engineering problems without real Engineering specs on candidate parts,   that are real,  honest,   and that specify data that is needed to design the product for a specific application,   IMO.

FWIW,   Thanks,   Vic

[kauaisolarman]

thanks for the input.

@ CDN VT if the drawing is not up to your standards then look somewhere else.  I don't remember pointing a gun at your head and requiring your input or help. you got nothing better to do than go online and make judgments about other peoples work?  go watch some more porn.

Classiccrazy and others thanks for your actual input and help rather thank being a little B****.

as far as the thermostat it was the lower thermostat that came with the heater, but i understand that the lower water heater thermostat can be used in 12/24V applications as it is just a switch.

info here http://waterheatertimer.org/Convert-AC-water-heater-to-DC-water-heater.html

will try to remove the thermostat and see what happens.

thanks again for all that provided helpful input.

will keep giving updates until it is figured out.  maybe someone else can benefit from the info in the future.

next step is to PWM the LOAD side off a Tristar ts60 and just use the SSR/contactor to run through the thermostat to turn off the tristar load when the water temps come up.

[mike90045]

AC & DV SSR   Are VERY different.   AC power stops 60x a second, and allows an AC SSR to switch off  ( electronically, you turn them ON, and the the AC turns them OFF 60x a sec, and then you turn them back on)

DC is a whole different matter, and your control signal "quenches" the power flow, at the expense of generating heat, the more often you turn them off (PWM) the hotter they get.

Try a test, using a switch and a battery to turn the SSR ON with your normal loading.  I'll bet it runs much cooler and lasts a long time. 

So, if you are wanting to do real mans work with real mans tools, you have to pay for them, as you have found, counterfeit junk on fleabay does not work.  here are links to 2 real parts, each about $115 US

http://www.digikey.com/product-detail/en/crydom-co/D1D60/CC1683-ND/2060411
http://www.digikey.com/product-detail/en/crydom-co/D1D80/CC1684-ND/2060412
chose the one that fits your specs best.
Below the part, are the recommended accessories: copper terminal lug for hi amps, heat sink thermal pad, heatsink.....

You realize, you cannot place an 8ga wire under the screw terminal, it won't make proper contact, you must use a lug.

And read the stinking data sheet.  If you don't understand how to wire this stuff up, you are doomed to repeat
repeat your mistakes over and over

MAX PWM Fq 800hz
Resistive loads only. Consider switching losses; at maximum frequency reduce to 75% output current.
Heat is your enemy - keep the part cool:
Heat sinking required, see derating curves.
Output wire 2 x 8 AWG
Thermal Resistance Junction to Case (Rjc) [°C/W]  0.34

[littleharbor2]

 It appears we have our very own "Sunking" here for any who know who I am referring to.

[TomW]

@ CDN VT if the drawing is not up to your standards then look somewhere else.  I don't remember pointing a gun at your head and requiring your input or help. you got nothing better to do than go online and make judgments about other peoples work?  go watch some more porn.

Well, KSM, if this were any other forum your account would be frozen. Since it is a Manufacturer support website, you can get away with this. Once.

Your hybrid parts picture and non standard drawing of the circuit interconnects is pretty useless for easy helping you so chill out with the attitude! There are accepted standards for depicting circuits and your crayon drawings do not qualify. This makes it much much harder to actually help.

Pretty easy to see you have absolutely no qualifications to do this yourself without the generosity of others.

I told you before you should probably get local professional help.

With this attitude, I suspect you rub everyone the wrong way as a matter of course and cannot get local help for that reason alone?

You have world class help here and they deserve a lot of respect for trying

Play nice.

Tom

[ClassicCrazy]

I will respectfully disagree with you a bit on circuit drawings Tom.
There are schematics,  ladder diagrams, pictorial  ( which this one falls into ) and some often  weird cryptic wiring  diagrams I see on certain devices. They all have their own purpose and uses.
If this drawing accurately portrays the circuit it is as valuable as any others in my mind. It also includes information like distances, breaker sizes , SSR type,  and wire sizes.
I have worked on a lot of devices, appliances, and electronics and it can take some time to basically do what his diagram does - isolate the one circuit and control that is being studied. Sure there could be other things that will come into play but other than detailed photo's or an onsite visit it would be difficult to take it all in.
We all learn from our mistakes - at least I have . The next job I do is usually better than the previous . And let me tell you I have made some real wiring tangles in the beginnings - especially before internet when I could publicly post up those messes for critique .
Larry

[ClassicCrazy]

AC & DV SSR   Are VERY different.   AC power stops 60x a second, and allows an AC SSR to switch off  ( electronically, you turn them ON, and the the AC turns them OFF 60x a sec, and then you turn them back on)

DC is a whole different matter, and your control signal "quenches" the power flow, at the expense of generating heat, the more often you turn them off (PWM) the hotter they get.
........

MAX PWM Fq 800hz
Resistive loads only. Consider switching losses; at maximum frequency reduce to 75% output current.
Heat is your enemy - keep the part cool:
Heat sinking required, see derating curves.
Output wire 2 x 8 AWG
Thermal Resistance Junction to Case (Rjc) [°C/W]  0.34

Mike - You make a lot of good points that need to be taken into consideration  !  There is more engineering in some of those devices than meets the eye sometimes !

Larry

[Vic]

I will respectfully disagree with you a bit on circuit drawings Tom   ...

Larry

Not to try to argue with anyone,   but,  I do totally agree with Larry.
That diagram was/is perfectly adequate for the purpose that it was trying to serve ...  AND,  it DOES have the part number of the DC SSR (which I had erroneously asked for).

One additional comment.  Kauai..,  it is good that you are not using the thermostatic switch in the DC supply side of the feed to the water heater element.   Over time,  you could possibly find that this switch function may become intermittent,   as those switch contacts are designed to handle fairly large AC current,   and the action of this current can help keep these contacts clean.

For a "dry circuit",   there is essentially no current flow,  and therefore the contacts can get dirt,  dust or a film which can cause the contact resistance to become so high,  that this switch could fail to pass enough current for the switch to do its job.

Many times,  switch and relay contacts which are designed for very low current circuits are Flashed or plated with Gold or similar,   essentially inert metal,  to allow lower contact resistance at continued low current operation.

And so on ...   Vic

[kauaisolarman]

@ Mike, Larry, and VIc

thank you very muck for your input and helpful information.

someone can definitely learn something from what you put online.

@ TomW, sorry i don't mean to slander or degrade anyone online, but if they (CDN-VT) send it my way i may just return to sender.  hopefully he got a good reprimanding also for his useless post that did nothing but insult me and my work.  just sayin

anyway back to subject

I will definitely try the better quality SSR and stay away from the cheapo stuff. 

only reason for not going with crydom to start with was i read some bad reviews online and Kyotto was noting but positive.
but lesson learned.

i have been in contact with SSRstore and they are setting me up with 1 of their SSR's and some protection diodes for it.

as far as the wire i am using 6 awg thhn and they terminate with a lug that goes on the screw terminals of the SSR.
not sure what PWM freq aux 2 sends from the classic.


an update:

since i burned all my SSR's and waiting for more "quality" ones to come in i have been playing with my tristar (PWM) CC and using it as a diversion controller.

it works good.  diverts my excess power and heats my tanks to 140 degrees.  only problem is when the tank gets to temp i have to manually turn off the breaker to stop the diversion.

i was thinking instead of PWM on the switch side of the DC SSR i would instead keep the tristar sending the PWM diversion load and just  hook the switch side to always on and run through the thermostat so that when the thermostat reaches temp it can turn off the 12V switch signal and cut off the PWM diversion that is comming in off the tristar.

this way the SSR is always in the "on" position and the load side will see the PWM and the SSR would only be switched to "off" when the water temps are up to 140 degrees.

could the DC SSR handle the PWM through the load side if it is always in the "on" position?  or is it because i am sending a PWM DC current i would still need the flyback diodes across the load terminals of the SSR?

thanks again if your contributing helpful information. i'm sure i am not the only one that will benefit from this information being out here.