Unpredictable SSR operation

[KartRacer54]

Could use some input. Built a full electric panel running 4500w boil and HLT and 4500 rims running at 120v.
My problem is that the pid is calling for heat and the SSR is sending the signal to heat but sometimes the ssr stays in full on mode instead of cycling with the pid, ssr signal. Other times they work perfectly.
Totally unpredictable.
I can sometimes restart the panel and the ssr functions properly for a while.

The PID is Mypin, the SSR is fotek or knockoff, no way to be sure. SSR,s are 40 amp.
Any idea what is going on?
Thanks in advance!

 

[The_Bishop]

Sounds like a failed SSR. The Foteks aren't the most reliable and they're heavily counterfeited.

 

[doug293cz]

Agree it's a problem with the SSR's. There is a chance that the SSR's are overheating. Do the heatsinks feel excessively warm? If you can't keep your hand on them, they are too hot. Warning: only touch your heatsinks in operation if you know they are securely grounded.

Brew on

 

[KartRacer54]

Heat sinks are warm, not hot.
My understanding was SSR,s failed, is it possible they can be intermittent?
At startup when temp point is set, they often show cycling but heating element stays fully energized. If I cycle the power they will operate correctly for a while or not .
I have no problem replacing them but wanted to make there is not some other reason they are not functioning correctly.
Yesterday R.I,M s would not cycle more than a degree or so, then stay on.
Total disaster!
Thanks

 

[LarMoeCur]

Are you really running it at 120V? With a 40 amp SSR? or did you mean 240v?

Anyway, 90% of Foteks SSRs are counterfeit! Now a good percentage of them are lower amp models re-branded at a higher rating. If I were a betting man...I'd bet that's exactly what you got. SSR works fine until it builds up heat. The heat is causing it to lock in the on position.

Where did you buy the SSRs? If you by Fotek only by from a very reputable dealer. I personally stay way from them. I've read of reputable dealers getting fooled by knockoffs.

 

[shady_ales]

Had the same problem with eBay foteks. Probably a knock off. They're on the list for an upgrade. Light would flash on and off but it wasn't actually switching. I added a computer fan to the side of the cabinet and the problem has gone away for now.

 

[KartRacer54]

Yes I'm running the rims at 120, bought the ssr all together. Could that be the problem. System thinks it's at 240 but splits at the receptacle.

 

[KartRacer54]

I'll try a fan but they don't appear to be hot unless they are hot in the box and thermally not connected well. I ll have to test that.

 

[doug293cz]

Yes I'm running the rims at 120, bought the ssr all together. Could that be the problem. System thinks it's at 240 but splits at the receptacle.

Running under rated voltage is not the issue.

Brew on

 

[shady_ales]

Mine didn't seem hot either. So who knows. I also changed the control cable from the PID to a screened twisted pair. Not sure if that helped but it was the spec'd cable.

 

[kal]

FYI - what's important is how hot the SSR is getting (not the heatsink). A cool heatsink doesn't mean that things are working well: It could be that you don't have good contact with the SSR so heat transfer is poor, causing the SSR to overheat.

Kal

 

[doug293cz]

FYI - what's important is how hot the SSR is getting (not the heatsink). A cool heatsink doesn't mean that things are working well: It could be that you don't have good contact with the SSR so heat transfer is poor, causing the SSR to overheat.

Kal

True, I like your answer better than mine. I just didn't want to suggest someone stick their hand inside a control panel while it was energized. Too many open terminals to be safe. I this case an infrared thermometer would be the tool of choice for checking the SSR temp. Want to measure the base plate temp if you can get a clear view of it, otherwise measuring various points on the body would have to suffice. I think most of the SSR's are rated for max 167˚F (75˚C) operating temp, but if anywhere on the body is more than 140˚F (60˚C), I would start to worry, as the actual solid state switch inside the SSR will be much hotter.

Brew on

 

[kal]

Yup! And the cooler things run, the longer they last. It's why I use an oversized heatsink myself. Good luck!

Kal

 

[KartRacer54]

Ran test today on all 3 SSR. Within 15 minutes they were at 138f.
Open door and blew large fan in cavity, they were running at 85f, but still locked in on position after a short time cycling. Going to assume that damage has been done from excess heat and I will replace units with non Fotek SSR's.
Hope to solve this issue!
Thanks for input.

 

[doug293cz]

Ran test today on all 3 SSR. Within 15 minutes they were at 138f.
Open door and blew large fan in cavity, they were running at 85f, but still locked in on position after a short time cycling. Going to assume that damage has been done from excess heat and I will replace units with non Fotek SSR's.
Hope to solve this issue!
Thanks for input.

Sounds like you may have a heat sink arrangement that is not particularly good at dissipating heat from the SSR's. You may want to reconfigure so that you new SSR's don't run hot. Can you post some pictures of your configuration showing heatsink placement, and describe how your heatsinks are mounted to both the enclosure and SSR's?

Brew on

 

[BrunDog]

As Kal mentioned, getting the heat out of the SSR is the key. If you didn't build these, take them off the sinks and make sure they have a thin film of heat transfer compound. Add if needed, then reassemble and test again with the fan system.

I would also make sure you understand the voltage the SSRs are seeing. Don't assume because the PID light is on or off that the SSR is being commanded properly. Put a voltmeter across the input terminals and watch the voltage changes. Make sure the high and low voltages corresponding to the command signals are correct.

 

[KartRacer54]

Doug
Thanks for your input. The SSR,s are mounted to Aluminum plate 5x8x1/4, heatsinks are mounted to plate and another plate above the heatsinks.i am placing 2 -1 1/2" holes in the side of the cabinet with fan on opposite top corner. Should flow air across the SSR's.

 

[KartRacer54]

I'm not sure I verified voltage to the SSR. Made the choice to assume input voltage was correct. I will verify that before installing new SSR's.
Thanks

 

[Ozarks Mountain Brewery]

I would suggest this ssr and a good heat sink, I use a pc processor heatsink and fan with mine

http://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=9

 

[kal]

Doug
Thanks for your input. The SSR,s are mounted to Aluminum plate 5x8x1/4, heatsinks are mounted to plate and another plate above the heatsinks.i am placing 2 -1 1/2" holes in the side of the cabinet with fan on opposite top corner. Should flow air across the SSR's.

Can you take a couple of pics of what you mean by this?

You don't need airflow across the SSRs, you need airflow across the heatsink(s).

Kal

 

[augiedoggy]

Yes I'm running the rims at 120, bought the ssr all together. Could that be the problem. System thinks it's at 240 but splits at the receptacle.

What do you mean the system thinks it's at 240? It's either wired for 240v or for 120v. Either way the SSR only switches one side of the circuit so if you rewired the outlet after the control panel to only use one hot line and added a neutral to the other than there's a 50/50 shot your not using the hot line that's actually being switched by the SSR and that could be your problem.

 

[doug293cz]

Doug
Thanks for your input. The SSR,s are mounted to Aluminum plate 5x8x1/4, heatsinks are mounted to plate and another plate above the heatsinks.i am placing 2 -1 1/2" holes in the side of the cabinet with fan on opposite top corner. Should flow air across the SSR's.

Sounds like everything is inside the panel enclosure. Is this correct? If so, that is likely part of your problem. Big slabs of aluminum will absorb head, until they get "hot" (reach equilibrium.) After that, they no longer absorb any heat, so the heat source (SSR) gets hotter. (A little over simplified,) but close enough.) You need to transfer heat from the heatsinks to the ambient air to get effective cooling. If everything is inside the box, heat transfer to ambient air is severely limited. Vent holes are only really effective if you have both inlet and outlet holes, and a fan(s) that either pulls air into the inlet, or forces air out of the outlet. Just circulating air inside the box, without forced in/out flow, is minimally effective.

As Kal said, some pics would be helpful.

Brew on

 

[KartRacer54]

What do you mean the system thinks it's at 240? It's either wired for 240v or for 120v. Either way the SSR only switches one side of the circuit so if you rewired the outlet after the control panel to only use one hot line and added a neutral to the other than there's a 50/50 shot your not using the hot line that's actually being switched by the SSR and that could be your problem.

Can't wrap my head around this.
I replaced the SSR today on the Rims, running element at 120, everything worked as it should. This receptacle is identical to the HLT and Boil with one lead capped and lead to neutral. I understand what your saying and maybe I just got lucky on the lead that I capped being the correct one.
Both of the other 2 SSR malfunction. I will replace them next.

 

[KartRacer54]

Here's heat sinks fan will be to left pulling air out.
Intake will be to right letting air in to box.
You guys are saying just blow air across heat sinks.
I have not tried that but SSR is hotter on the output side of the SSR than the heat sinks are.
Try to put other 2 pic up.

 

[KartRacer54]

Photo 2

 

[KartRacer54]

Photo 3

 

[kal]

I think you have too many layers here. The heatsinks should be directly attached to the SSRs with a *very* thin layer of heatsink compound between the two. Are you using heatsink compound?

The surfaces should be perfectly flat (the SSR one will be, not sure about the big sheet of alu).

I would probably get rid of the second sheet of alu at the top. It's probably hurting natural convection more than helping.

It could also be that the Foteks you have are counterfeit like you mentioned. I know there have been posts in the past as to how to tell.

Good luck!

Kal

 

[JONNYROTTEN]

I went through ENDLESS Foteks with nothing but issues. I bought a Crydom on EBAY plus 2 more spares. I haven't touched the spares. If you need A 40 amp SSY I would jump on this immediately before its gone. They're not faked like the Foteks. Its a homerun for $12...Don't even waste time asking a question...just buy it...then ask questions

http://www.ebay.com/itm/Crydom-D240...021678&hash=item3d3ee5d193:g:V5EAAOSwmCVY-AT-

 

[BrunDog]

I agree with Kal. I think many overlook the importance of the heatsink. The first thing anyone should do with the stock heatsinks is unscrew them from the SSR and put them in the recycling bin. As Kal mentioned, a proper flat surface is critically important to effective heat transfer. I would venture its not important then the rest of the sink. The compound is there to fill in imperfections, not bridge the gap.

 

[processhead]

I went through ENDLESS Foteks with nothing but issues. I bought a Crydom on EBAY plus 2 more spares. I haven't touched the spares. If you need A 40 amp SSY I would jump on this immediately before its gone. They're not faked like the Foteks. Its a homerun for $12...Don't even waste time asking a question...just buy it...then ask questions

http://www.ebay.com/itm/Crydom-D240...021678&hash=item3d3ee5d193:g:V5EAAOSwmCVY-AT-

Yep. I used the Crydom D2440 SSRs in my panel build and never looked back. That was 7 years ago and haven't had to touch them since they were installed. Also have used Opto 22 brand SSRs in meat smoker projects with 100 % reliability.
Never have tried the Fotek SSRs and have no plans to in the future. Too much uncertainty on what you are getting.
Whats your time worth to you?