Diagnostic help please! (Smoked an SSR)

[cyberbackpacker]

Short story... I have an illuminated push button 2-way switched wired inline such that I choose between one of two 4.5kw elements to use so that they are isolated and both cannot be run concurrently, while only having to use one 25A SSR for both of them.

The 2-way switch has a NO and NC contact block. When "off" the HLT element is being controlled by the 3-way switch and when "ON" the BK is being controlled.

Attached you will see a diagram of how I am controlling the two elements and how everything is wired. I don't know if I have the switch that is circled in purple diagramed properly, but I am attempting to show the NO and NC contacts.

I also attached a pic of both contact blocks I am using (Came from ebrewsupply).

Here is my problem and what I am looking for an explanation for. The other day I was testing, and when I pressed the button to go from the BK to HLT element I smoked my SSR that controls the two element, and the GFCI breaker also popped.

One thing of note: I was really just trying to isolate the circuit to the BK and did not think ahead (really was just trying to turn the element in the BK off) but the wire to the HLT was not terminated to anything at the time. It was in a junction box but not connected to the element.

So I am hoping to avoid this mistake inthe future.

From how everything is wired, I do not know how I managed to smoke the SSR through pushing the push button. The switch is isolated from the SSR, and the contact blocks as far as I can tell are rated to 10A and there is no other voltage going through the switch. The 3-way switch which reallythat is also diagramed only has 10a and low amp/low voltage 5v going into it. Additionally, the 2-way switch is really only switching 120v at 10a; the switch is controlling which DODT 120v coil 30a contactor (BK or HLT) is being energized by the 120v.

The breaker popping is from the HLT wires not being connected, because it is "registering" as a ground fault. But, I am puzzled for why the smoked SSR.

The only thing I can maybe guess for why the SSR smoked is there was too much resistance because of the "open" wires?

Any ideas? I would love to be able to know I can have the main 3-way switch diagramed in a BCS or Manual mode, and know that I can switch between the BK and HLT simply by pressing the illuminated 2-way switch without having to turn the 3-way switch to the off position first.

I could remember to so this but someone who was unfamiliar would not and it just doesn't seem like good design, and after so much time and work trying to do this "right", I don't want to have this be a bugaboo.

Thanks for the help.

 

[stlbeer]

Are you sure there's no point in time when both the NC and NO sides of your switch are not both in contact? I know you said the HLT element wasn't wired up, but I wonder if that somehow overloaded the SSR.

 

[johngaltsmotor]

Most likely you had a short. Was the HLT wire just cut and left in the conduit box? i.e. could the cut ends have touched each other or the housing (ground). If so that would result in a dead short.

If that's the case your SSR is going to blow LONG before that circuit breaker trips. To protect SSRs and SCRs at rated current you really need a fast blow semiconductor fuse.

It is also possible that because you have two switches that aren't interlocked as a "break before make" there is nothing to guarantee that they aren't on at the same time for a short period.

 

[cyberbackpacker]

Thanks guys... I was thinking the same thing myself in regards to the switch being used that it is possible that possible for a period of milliseconds that both contact blocks are activated which caused a surge of current which fried my SSR.

Johngaltsmotor, the wire to the element in the junction box had each line wire capped off, so a short at the point does not seem to be the issue I would think.

 

[johngaltsmotor]

If your GFCI tripped it must have found ground somewhere. Otherwise at a minimum your tandem 25A should have popped if it was due to a 50A overload.

Why does your e-stop go from line to ground? It would seem that your always going to have a GFCI trip with that configuration because it will cause a Line 1 v Line 2 imbalance.

 

[cyberbackpacker]

Johngaltsmotor, thanks again. I have more diagnosing to do!

As for the e-stop, that is the common type of e-stop as used/advised by PJ on here and many other beer forums. The switch is a momentary switch with a NO contact. When it is activated, it shorts to ground tripping the breaker and killing all power. So it is by design. The ground to short only happens intentionally WRT to the e-stop switch.

 

[johngaltsmotor]

Okay, but you have the e-stop shown as NC, that was my concern. I can understand using the GFCI as your e-stop trip.

 

[P-J]

Okay, but you have the e-stop shown as NC, that was my concern. I can understand using the GFCI as your e-stop trip.

Yup. All the E-Stops I've drawn use N/O contacts. Somehow he chose to use a N/C contact illustration. Wrong...

 

[johngaltsmotor]

Do you have a heat sink on your SSR?
What is the cold resistance of your HLT/BK elements? (i.e. what cold inrush current are you expecting?)

 

[jeffmeh]

You may have a different problem, but a 3 position switch that forced you to go through off when switching between elements would be a better solution.

 

[clearwaterbrewer]

If you have a 25A circuit breaker like the drawing says, overcurrent should not have fried it, I have personally smoked 2 SSR's in a row due to an internally shorted boil kettle element (I think it was actually shorted to ground sheath inside the element) and not having circuit breakers. I installed a dual 30A breaker on each element and have not had a problem since...

 

[cyberbackpacker]

Well, I tried the easiest solution first, and replaced the 2-way push button with a 3-way and it works perfectly. No issues. I can only guess that there was an over current and that the SSR acted as a Fuse first, before the breaker tripped.

Oh, last thing... On the diagram I admit I never really looked at the estop switch diagram... It was literally copied and pasted for one of P-J's diagrams exactly as depicted above. That said, for my own record now, I updated it on my hard copy to be properly denoted as NO as opposed to NC.

Thanks for the input.

 

[cyberbackpacker]

NEW problem. Maybe I'll start a new thread, but it utilizes the same diagram and such...

I am getting leakage from somewhere in each circuit that is energizing the red led that is wired in after the contactor when in BCS mode. In that instance, it should only be illuminated if the BCS is actually switching on the SSR. But it is illuminated even when the BCS us not powering the SSR.

I thought the element could be allowing the current to run through, but again one circuit terminates at wire caps right now, not to an element. Yet both circuits exhibit the same behavior WRT to the light being illuminated even though the contactors are not energized. I had a friend who is an industrial licensed electrician come check things out, and he measured everything and does not believe it is a failed component or improper wiring, etc. He believes it is leakage, either radiative or... I forget the other term. He thought a resistor could be added to increase resistance since the LED requires so little current but he was unsure what size resistor to recommend as that is outside of his typical line of work.

So, any thoughts on resistor size to try with reference to above diagram? LEDs are from ebrewsupply.

Thanks in advance!

 

[jeffmeh]

You have the elements plugged in when you are testing this? If not, that is your issue. They will provide the resistance.

 

[cyberbackpacker]

One is plugged in, one is not; both lights are illuminated!

 

[jeffmeh]

I just looked at your diagram again. Will your LEDs run at 240v? The least problematic method appears to be wiring the indicator lights at 240v, in parallel with your element. Then with the elements providing resistance, it should work as expected. If not, you have a different problem. You really do not need to protect the LEDs with fuses.

 

[cyberbackpacker]

Jeff, my LED's are unfortunately only rated at 120v, but your idea is one worth considering.

As for fusing, I did that because in the DC world of car audio, the standard is to always fuse when reducing wire size... So since I was dropping from 10awg to 14awg I fused the LED's there.

 

[jeffmeh]

Sorry for the lack of clarity. If you move to 240v LEDs and use 10AWG to run to them, then you won't need the fuses. If you are really downsizing the wire, carry on.