DC SSR size?

[kauaisolarman]

hello all

so i have finally finished installation of my second off grid system and i have been having problems with my DC SSR and my hot water dump load.


anyway I am running my dump directly off my battery bank 48V and using the AUX 2 waste not HI off 1 of my controllers to switch on/off.

problem is i keep burning up relays.  i am using 75A 5-240V DC SSR and only putting 47Amps at 49.6V and once i turn on the aux the relay connects and never wants to disconnect after that.

now the relay always stays in the "on" configuration no matter if i have the 12V switch side connected or not.

i have 4 different relays all different brands all same results.

then i initially install the relay is "off" and there is no current flowing from the battery to the heating element.  when i turn on aux 2 manually the relay turns "on" and current flows to the heating element, but, when i turn aux 2 off manually the relay does not turn off an current keeps on flowing into the heating element.  after that happens the relay never turns back "off" after that.

I'm assuming i'm frying relays.

WbJr says the heating element was drawing 47A @ 49.6V today just after the sun went down with no PV input just straight draw from the heating element.  battery  SOC was 100%

does DC SSR need blocking diodes?

[mike90045]

Generally, SSR's do need a heat sink.  Even 50% load, a couple watts builds up without any sink.

Also, there are AC SSR's and DC models,  are you sure you ordered DC models.  They should have some sort of spec for latch and disconnect.

http://www.crydom.com/en/products/catalog/s_1.pdf  specs on 1st page

These are AC only models, with DC control
http://www.allelectronics.com/item/srly-2425/25a-solid-state-relay/1.html

[kauaisolarman]

thank you for the reply

yes i am sure about the DC relay  purchased here
http://www.ebay.com/itm/140534723852?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

also connected to a 100A heat sink
http://www.ebay.com/itm/271793449716?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT


made sure the battery was connected to the (+) side of the relay and the load/heater element connected to the (-) side.

i also tried flotek 100A and same results.  if i dont turn off the breaker and just leave it on it burns up the relay (smoke) within 2-5 mins of being on.

as mentioned earlier when the sun went down i turned on the heating element breaker just to see the load coming out of the battery and WbJR says 47A draw and CC reads 49.6V.   battery 100% SOC and resting voltage 54V no loads on battery other than heating element.

burned/damaged 7 different relays today.  don't know how to proceed.

my other system is running AC heating element directly off my inverter with AC SSR and works perfect for using excess power with waste not HI AUX 2.

was told to go the direct battery DC route and it would be better but it seems to be only producing problems.  anyone running DC-DC ssr to heating element can give me any advise on how to hook it up properly?

as of right now my positive wire is coming off my (+) battery bus bar and passing through 2 breakers (one in my controller room and the other next to the water heater) then connected to the (+) load side of the DC SSR.   the (-) load side of the DC ssr is connected directly to 1 heating element terminal, while the other heating element terminal is connected directly to my battery (-) busbar.

aux 2 connected to the switch side of the DC SSR.   

with everything connected for the initial time no power passes through the relay and the heating element doesn't see any current.  if i manually switch aux 1 on it activates the relay allowing current to flow to the heating element, but when i turn off aux 1 manually the current never stops flowing.  after that point the SSR never goes back to the "disconnected" position it just always allows current to flow through. at this point i use circuit breaker as off switch as the relay is "stuck on".

not sure what i am doing wrong at this point.  like i said WbJR is only seeing 47A draw out of the battery bank while the SSR is on.

tried to leave it on and see what happens and it fried internally (smoke and burnt plastic smell) within 3 mins of being on.  the heat sink and relay are extremely hot at this time.

any advise would be lifesaving

[mike90045]

here's the best DC output SSR (which really use s MOSFET)
http://www.crydom.com/en/products/panel-mount/perfect-fit/dc-output/

Also, when switching heavy DC loads, you can get a large inductive spike from the ON or OFF mode,  and that can fry the innards.   
Most PWM solar controllers use a FET or MOSFET as the switching device, it's a well established technology, and good factory prime parts should be fine.   
You may want to get some 70V zeners and put them back-to back at the control AND load connections to snub any spikes.

Your 48V bank ,  when charging, can hit 64V, which is only a couple % away from the 70V limit on your relay,

Maybe the parts are miss marked and that's why they are on ebay

[dgd]

What exactly is the heating element you are using? I have never seen a 2500watt 48v element, the 47A at 49v is close to 2500watt.
If the SSR is getting hot and the heat sink too then the actual current draw may be significantly more, I assume you have the Wbjr between the -ve busbar and the battery and the SSR -ve is connected to the -ve busbar.
Take a look through some of the earlier posts here concerning water heating and DC SSRs.
Also google the Crydom D1D100 datasheet and see the wiring diagram that shows a diode used to supress inductive spikes, best to include one anyway even if your heating element is not a coil type design.

dgd

[kauaisolarman]

thanks again for the replies.

this is the heating element that is being used  chose the 2000 watt 48V option.
http://mwands.com/store/dc-water-heating-elements/9-3-8-inch-dc-submersible-water-heating-element

the output/power readings that i provided was just what i got off the WbJR.  with the batteries at 100% SOC (54V) and no loads running (0.0A on WbJR) i turned on the heating element and then wbJR says -46.9A and controller registers 49.6V wile the load is on.

still a newbie at this stuff so please try to be as layman as possible when explaining possible solutions/problems that you may see for my situation.

Yes Wbjr is hooked up with 1 side of shunt going directly to battery (-) negative terminal and other/opposite side of shunt on my Negative "bus bar".   negative lead off heating element is going directly to negative "bus bar" with no circuit breakers in between just direct connection.

does the diode need to be across the load or can i connect it directly to the ssr?  i was thinking of thins blocking diode any suggestions?
https://www.amazon.com/gp/product/B004FGPUE6/ref=ox_sc_act_title_2?ie=UTF8&psc=1&smid=A2TN19FHI2Z5KL

trying to spend as little money as possible to get this going.   I though this ssr relay was just straight forward stuff.  what could i be doing wrong?

[TomW]

Things you should know.

Ebay parts are often factory seconds or did not meet spec for their markings.

The SSR needs a properly sized heat sink with thermal grease. Period.End Quote.

A stud diode IS NOT a zener and will not protect against voltage spikes. Maybe research "flyback diodes" and "zener diodes". "Across the load" can be at the load or at the SSR, they are electrically the same. I would put it at the SSR myself.

More of those little details it is hard to pass along via a forum that can make or break a project.

I would suggest you source parts from someplace other than Ebay. My experience is the stuff from Ebay is quite often low grade  junk Chinese knockoffs  or seconds. Go to a reputable online parts source.

A lot of solid state components are more susceptible to over voltage than over current and even a bit of static from walking across a carpet can zap them if you don't properly ground yourself while handling them. The devil is in the details.


Best of luck.

Tom

[ClassicCrazy]

Maybe you need to move up to something more substantial like a contactor.  For all the relays you have burned up this probably is the same price.
Check with the EV parts place or the Gigavac - I am sure they will give you info on the correct product to do what you want it to .

http://www.evwest.com/catalog/product_info.php?cPath=2_13&products_id=407
http://evwest.com/support/gv200.pdf


Larry

[TomW]

Maybe you need to move up to something more substantial like a contactor.  For all the relays you have burned up this probably is the same price.
Check with the EV parts place or the Gigavac - I am sure they will give you info on the correct product to do what you want it to .

http://www.evwest.com/catalog/product_info.php?cPath=2_13&products_id=407
http://evwest.com/support/gv200.pdf


Larry

Absolutely, if it is  an on / off application and not PWM driven.

Tom

[kauaisolarman]

thanks everyone for all the input.

i did look into the crydom D1D100 and the price is $140 ish.

at that pricing should i just opt for a tristar TS60 and use it specifically as a diversion load controller PWM.

I do have a TS40 but the amperage that was being drawn from the element was a bit higher than that controller can handle, but a TS60 would be within amperage range?

what would be the better route?

a) purchase crydom D1D100 and use a diode to try to protect the relay.  (problem is i'm not too sure of what kind of diode would be applicable in my situation blocking/flyback/zener?).  this would be activated by waste not HI AUX 2 PWM and direct battery hookup 

b) purchase tristar TS60 PWM CC and use it for diversion control and run it off the battery then to the heating element and hopefully it will work the same as having the SSR and AUX 2 waste not HI


i do have another system using a diversion load heating water for me but it is running AC directly off my inverter.  been running great with no problems and harvests a lot of would be wasted energy throughout the day.

option c)  run AC for this system also.  instead of running DC off the battery bank i would need to source a bigger inverter and just run AC heating elements directly off the inverter.

don't know what to do......

[kauaisolarman]

Things you should know.

Ebay parts are often factory seconds or did not meet spec for their markings.

The SSR needs a properly sized heat sink with thermal grease. Period.End Quote.

A stud diode IS NOT a zener and will not protect against voltage spikes. Maybe research "flyback diodes" and "zener diodes". "Across the load" can be at the load or at the SSR, they are electrically the same. I would put it at the SSR myself.

I would suggest you source parts from someplace other than Ebay. My experience is the stuff from Ebay is quite often low grade  junk Chinese knockoffs  or seconds. Go to a reputable online parts source.


Tom

thanks for the input.  it sucks because the KYOTTO SSR's are technically rated for 5-220volts DC  would my 48V battery bank be able to spike the voltage that high?

so basically the problem i have is that when the heavy DC load is turned on/off there are inductive voltage spikes and that is what is causing the relays to fry up?   

not from overcurrent or reverse current?

why would the relay overheat so quickly when i leave the load ON.  i did leave 1 relay on until it actually burned up and smoked only took about 2-3 mins.  i am using a 100A heat sink with the relays and the heat sink ia also very hot to touch after 1 min of being on?    why would this happen?  it seems the SSR is producing the heat instead of the heating element.

[kauaisolarman]

is there any possibility that the AUX 2 12V source power is interfering with the 48V batery signal abd causing the relay to ground out and burn up?

is there anyone that has done this type of DC diversion water heating element using DC SSR at this high amperage?

need some practical advise from someone who has experience setting this up.

checked continuity with my gauge today and when i put the gauge to the beep/sound setting i get a beep when testing between my main + busbar and the negative (-) terminal on the AUX 2.

wondering if somehow when the CC sends the 12V signal to the SSR it could be grounding out to the negative wire that is coming off aux2?

tried for another 5 hours today to troubleshoot and no luck.

1 weird thing happend.

40A breaker has a trip current of 52Amps.  had the heating elemet turned on with my clip on amp meter and meter was registering 46A and the breaker would trip after being on for a minute or 2. amps not near 52A.

[ClassicCrazy]

There are different  ways to setup the AUX contacts using jumper in the Classic - which way do you have yours set up ?
From Classic Manual

"Aux 1 and Aux 2 Graphs/Jumpers
Figure 3.0 shows the two Aux port terminals, with their respective
Polarities. These terminals are located at the bottom of the
Power board below the battery temperature jack. Use a mini
flat head screw driver to tighten the screws. The jumpers are
described in the section below.
In order to select operation of Aux 1 between relay contact or 12v output JP6 and JP8 need to be configured accordingly following the instructions provided in this section. (Set for dry contact by default)
When Aux 1 is used to supply 12v out, JP6 and JP8 have to be in the position shown in Diagram 2. The basic schematic of how this works is shown above. The 12v out is more like 14.5v. The maximum current from Aux 1 should not exceed 200mA. The Aux 1 output can be set to operate at either Active High (12V) or Active Low (0V) when the Aux 1 function condition is true. For more information see Configuring Auxiliary Input/Output on page 37."

[ClassicCrazy]

okay I reread your original post and see you are using Aux 2 instead of 1

How do you have the AUX 2 set up for PWM ?

As others have said you probably need a larger heat sink, better quality relay, and the diode protection.  And if you use one of those big Gigavac  contactors it isn't going to burn up because it is made to switch on large loads and has built in protection for the coil.

Asking the questions you want to know to the Gigavac techs will probably be able to answer since that is their business.

There is a lot of discussion on Otherpower forums  about using PWM for DC loads
http://www.fieldlines.com/index.php?topic=148314.0
Here is detailed discussion about using Classic PWM for hot water heating
http://www.fieldlines.com/index.php/topic,147132.0.html

Larry

[ClassicCrazy]

You also probably want to reread this thread
http://kb1uas.com/mnsforum/index.php?topic=3352.0

You asked on this thread about if you need diodes and there were some suggested and also  was suggested you call this relay vendor who could give you the support.



Larry