Author Topic: I fried my SSR........ HELP!!!  (Read 5571 times)

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Offline jwilsonTopic starter

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I fried my SSR........ HELP!!!
« on: January 24, 2020, 10:24:13 pm »
Hey guys, I'm a newbie and really need some help.

I'm trying to replace the old controls in a Paragon kiln and use a PID with 2 SSR's using 220v.

Here's a list of the equipment I'm using:

SSR - 2 x Inkbird Solid State Relay 40DA DC SSR

PID - Auber Instruments PID TEMPERATURE CONTROLLER,W/ 30 RAMP / SOAK,SSR OUTPUT

Here's how I wired everything and killed an SSR.....

220V coming into the box and the white leg going to SSR #1 on terminal 2.

The black leg of the 220V going to SSR #2 on terminal 2.

I wired the SSR's in series going from SSR #1 I wired terminal 4 to terminal 4 on SSR #2.

I wired SSR #1's terminal 3 to SSR #2's terminal 3.

Then I ran a wire from SSR #2's terminal 4, negative, to terminal 8 on the PID.

I ran a wire from SSR #2's terminal 3 to terminal 7 on the PID.

I ran a wire from SSR #1's terminal 2 to to terminal 9 on the PID.

I ran a wire from SSR #2's terminal 2 to a rocker switch and then to terminal 10 on the PID.

I also hooked up the thermocouple to the PID via terminals 4 and 5.

So, I was using terminal #1 on BOTH SSR's to go to the heating elements on the kiln.

When I switched the PID on and the output light kicked on, the elements started to heat up and then SSR #2, with the black 220V wire going to it, started smoking and made a POP!!! It's dead.

How should I wire this thing up????????? This is killing me and I don't get it.

Please help!!!!

« Last Edit: January 24, 2020, 10:31:00 pm by jwilson »
 

Offline duak

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Re: I fried my SSR........ HELP!!!
« Reply #1 on: January 24, 2020, 11:06:15 pm »
Ouch!

A few questions:
1.) what is the element power rating or the rated current?
2.) is the element isolated from ground?  Please check with a meter.
3.) has this kiln worked before, perhaps with a different controller?
 

Offline james_s

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Re: I fried my SSR........ HELP!!!
« Reply #2 on: January 24, 2020, 11:21:32 pm »
Are these cheap SSR's from China? I'm not familiar with that brand but they sure look like it. Keep in mind the specs on those are hugely exaggerated, I think you'd be lucky to reliably switch 15A with a "40A" SSR. Buy SSRs from a reputable company like Crydom, they will cost a lot more but you can rely on their specs to be honest. Also make sure you mount them on an adequate heatsink, if you are pushing 30-40A through SSRs they're going to get hot, they have a much higher dissipation than mechanical relays though they are superior for applications that do frequent cycling such as PID temperature controllers.

You'll also probably want to have some sort of backup protection, see this for an example of what can happen when one of thee fails: https://hackaday.com/2018/08/24/fail-of-the-week-solid-state-relay-fails-spectacularly/

When a SSR fails it usually fails closed, this can be a very bad situation when you are controlling a heating device. I would probably add an additional mechanical relay controlled by a thermal fuse.
« Last Edit: January 24, 2020, 11:26:29 pm by james_s »
 

Offline james_s

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Re: I fried my SSR........ HELP!!!
« Reply #3 on: January 24, 2020, 11:39:59 pm »
This is the sort of thing you want. You can either get a pair of single ones like this:
https://www.digikey.com/product-detail/en/sensata-crydom/D2440/CC1071-ND/221764

Or you can get a double one like this and only need one of them.
https://www.digikey.com/product-detail/en/sensata-crydom/D2440D/CC1122-ND/221840
 
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Offline jwilsonTopic starter

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Re: I fried my SSR........ HELP!!!
« Reply #4 on: January 25, 2020, 12:33:12 am »
Ouch!

A few questions:
1.) what is the element power rating or the rated current?
2.) is the element isolated from ground?  Please check with a meter.
3.) has this kiln worked before, perhaps with a different controller?

1. The element power rating is 30 Amps and 7200 Watts
2. The element wasn't grounded.......That's probably the problem.
3. The kiln did work before, but I'm a knife maker and need to hold precise temps in order to heat treat knives.

Thanks for chiming in!!!
 

Offline jwilsonTopic starter

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Re: I fried my SSR........ HELP!!!
« Reply #5 on: January 25, 2020, 12:35:52 am »
Are these cheap SSR's from China? I'm not familiar with that brand but they sure look like it. Keep in mind the specs on those are hugely exaggerated, I think you'd be lucky to reliably switch 15A with a "40A" SSR. Buy SSRs from a reputable company like Crydom, they will cost a lot more but you can rely on their specs to be honest. Also make sure you mount them on an adequate heatsink, if you are pushing 30-40A through SSRs they're going to get hot, they have a much higher dissipation than mechanical relays though they are superior for applications that do frequent cycling such as PID temperature controllers.

You'll also probably want to have some sort of backup protection, see this for an example of what can happen when one of thee fails: https://hackaday.com/2018/08/24/fail-of-the-week-solid-state-relay-fails-spectacularly/

When a SSR fails it usually fails closed, this can be a very bad situation when you are controlling a heating device. I would probably add an additional mechanical relay controlled by a thermal fuse.



The SSR's are from China via Amazon. I probably should have purchased American made components.

I do have an adequate heat sink and I used thermal paste on each one just to be safe.

Thanks for the info!
 

Offline jwilsonTopic starter

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Re: I fried my SSR........ HELP!!!
« Reply #6 on: January 25, 2020, 12:38:14 am »
My main question is this.

Should I connect one leg of the 220 to the SSR and one leg to the element?

Or, do both legs of the 220 go to both SSR's? One leg to each.

I'm confused.

Thank you all for chiming in and giving me some direction!
 

Offline ignator

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Re: I fried my SSR........ HELP!!!
« Reply #7 on: January 25, 2020, 02:02:47 am »
I have a 3KW radiant heater that is wired similar to your initial wiring. Mains power L1 through one SSR (then connect its terminal to the heater), and mains power L2 through the other SSR (and then connected to the other heater lead). This is correct to have the SSR's connected this way.
Now, cheap China SSR can be fake and use a name brand, Fotek being one that is the most common to counterfeit (from what I see and buy). They do not have the Triacs of correct capable max current, nor are they connected properly to the heat sink back plate of the SSR.
I used to see a guy on eBay that had a fake selling listing to warn people about the Fotek's he got. He had photos of the inside showing bad parts and assembly practices.

This really looks like you connected it correctly, but the SSRs are junk to start with for what your trying to do.
I also had one of the SSRs fail last year after using this for over 5 years. I replaced it with a Crydon. And yes mine are 40amp SSRs, but I paid ~$5 each for them from China.
« Last Edit: January 25, 2020, 02:04:51 am by ignator »
 
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Offline ConKbot

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Re: I fried my SSR........ HELP!!!
« Reply #8 on: January 25, 2020, 05:23:37 am »
A 30A heater will draw over 30A during warm-up until the element itself is at temperature. They have a positive temperature coefficient, similar to a lightbulb, just nowhere as severe. I'd suspect overly optimistic ratings from the manufacturer is what is the problem. As far as I can tell, the hookup looks fine.
But the choice of wire for supplying 240V to the PID controller looks dubious. If that's speaker wire, it absolutely needs to change to something meant for mains. If that's lamp cord, it's a bit sketchy, but probably fine as long as that compartment doesn't get too warm inside it when the kiln is on. 
I'd also echo the suggestion for a crydom relay (not from ebay or Amazon resellers) it won't be super cheap, but if the SSRs fail short while your doing a final temper, it will waste a bunch of your time when it turns out you accidentally annealed the knife. Determine if future time savings is worth the cost to you.  The two relays in series mitigates this some, but if you're not monitoring for a failed relay, you won't notice the first one failing.

 
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Offline duak

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Re: I fried my SSR........ HELP!!!
« Reply #9 on: January 25, 2020, 05:31:49 am »
Jwilson, here's what I think:

1.) the SSRs are probably NFG.  Last I checked, Crydom or other quality SSRs are quite a bit more expensive
2.) If the element has a metal case or tube, that can be grounded but you definitely do not want the resistance wire to connect or even slightly conduct to ground.  Check this out!
3.)  as wired, two SSRs in series is a good idea in case one fails.
4.) you are dealing with 30 amps here and anything smaller than 10 AWG conductors is marginal if not hazardous.
5.) each SSR is running at about 75% of capacity and will dissipate about 15-20 W.  You seem to have a galvanized sheet steel enclosure probably about 0.030" thick.  IMHO, this is nowhere near good enough as steel is not a good conductor of heat as is aluminum.  It's just too thin to carry much heat away.   I've used a rule of thumb of at least 1 square inch of 1/8" thick aluminum sheet for heat sinking.  Where to put it is another question.
 

Offline jwilsonTopic starter

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Re: I fried my SSR........ HELP!!!
« Reply #10 on: January 25, 2020, 02:34:08 pm »
Jwilson, here's what I think:

1.) the SSRs are probably NFG.  Last I checked, Crydom or other quality SSRs are quite a bit more expensive
2.) If the element has a metal case or tube, that can be grounded but you definitely do not want the resistance wire to connect or even slightly conduct to ground.  Check this out!
3.)  as wired, two SSRs in series is a good idea in case one fails.
4.) you are dealing with 30 amps here and anything smaller than 10 AWG conductors is marginal if not hazardous.
5.) each SSR is running at about 75% of capacity and will dissipate about 15-20 W.  You seem to have a galvanized sheet steel enclosure probably about 0.030" thick.  IMHO, this is nowhere near good enough as steel is not a good conductor of heat as is aluminum.  It's just too thin to carry much heat away.   I've used a rule of thumb of at least 1 square inch of 1/8" thick aluminum sheet for heat sinking.  Where to put it is another question.

Bear with me here, so I do not want to ground the heating element?

The heating element is just coiled wire with 2 ends. I have 4 elements in total. Here's what I did.

Since I have 8 leads total, I wired 4 wires together for a + lead and 4 wires together for a - lead.

Should I ground the "-" leads to the chassis?

When I blew the SSR, I had power going to each set of leads and it blew the SSR.

I figured my mistake was that I didn't ground half of the leads.

What do you think?

THANK YOU!!!!!
 

Offline jwilsonTopic starter

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Re: I fried my SSR........ HELP!!!
« Reply #11 on: January 25, 2020, 02:36:17 pm »
Jwilson, here's what I think:

1.) the SSRs are probably NFG.  Last I checked, Crydom or other quality SSRs are quite a bit more expensive
2.) If the element has a metal case or tube, that can be grounded but you definitely do not want the resistance wire to connect or even slightly conduct to ground.  Check this out!
3.)  as wired, two SSRs in series is a good idea in case one fails.
4.) you are dealing with 30 amps here and anything smaller than 10 AWG conductors is marginal if not hazardous.
5.) each SSR is running at about 75% of capacity and will dissipate about 15-20 W.  You seem to have a galvanized sheet steel enclosure probably about 0.030" thick.  IMHO, this is nowhere near good enough as steel is not a good conductor of heat as is aluminum.  It's just too thin to carry much heat away.   I've used a rule of thumb of at least 1 square inch of 1/8" thick aluminum sheet for heat sinking.  Where to put it is another question.

Oh, and to address #5, you can't see it well in the pictures, but each SSR is connected to a heat sink per SSR. The heat sinks are aluminum and about 2"x2"x2" tall.

Thanks again!
 

Offline calzap

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Re: I fried my SSR........ HELP!!!
« Reply #12 on: January 25, 2020, 04:05:29 pm »
I agree that quality brand SSRs are the way to go.  However, if the controller is slapped on the side of or anywhere near the kiln, passive cooling may not be enough.  Advise fan-cooled heat sinks.  And if possible, don't attach the controller to the kiln or place it above it.

My one experience with an Auber controller (for a smoker) was not good.

And, minor point, your power voltage is almost certainly 240 VAC, not 220 VAC

Mike in California

 
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Offline james_s

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Re: I fried my SSR........ HELP!!!
« Reply #13 on: January 25, 2020, 04:47:14 pm »
For chassis wiring you can get away with #14 wire though I don't think I'd go smaller than #12. The ampacity is considerably higher than for power transmission where the length is greater and it may be enclosed within walls or covered by insulation.

https://www.powerstream.com/Wire_Size.htm
 

Offline DBecker

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Re: I fried my SSR........ HELP!!!
« Reply #14 on: January 25, 2020, 06:58:50 pm »
For chassis wiring you can get away with #14 wire though I don't think I'd go smaller than #12. The ampacity is considerably higher than for power transmission where the length is greater and it may be enclosed within walls or covered by insulation.

https://www.powerstream.com/Wire_Size.htm

That is correct: chassis wiring suspended in free air has much higher ampacity than supply wiring that is likely thermally insulated and bundled with other current-carrying conductors.
But for one-off prototypes and projects you can afford to be much more conservative and use thicker wire.  That will compensate for inconsistent connections and act as additional heat sinking.

I agree with the other posters: eBay SSRs are often rated more like fuses than components.  The stated current is where they very likely will fail, not a continuous operating current.  A Chinese "40A" SSR is OK for 10 amps, but (generalizing here) unsuitable for 20 amps.

If you want reliable operation at a low price, use a single SSR to operate a 40 amp dual circuit contactor.  Most will operate continuously at their rated current, survive surges and overloads if they aren't make- or break-current, and will survive hot conditions.  Their main down-sides are size, slight noise, and a floor on power use.
 

Offline dmills

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Re: I fried my SSR........ HELP!!!
« Reply #15 on: January 25, 2020, 07:21:30 pm »
 What does that PID controller output on its control terminals? For SSRs it should be dc of a modest number of volts, not mains!

No you should NOT earth ether end of the heating element! That you suggest this says you probably want to find someone who understands US style split phase wiring.

There should be a modestly rated fuse or circuit breaker separating the control power from the heavy current, otherwise a fault in the PID controller could cause many, many amps to flow thru its supply wiring, which would be bad.

SSRs are not usable as isolation, so given you need a separate isolation switch to make touching the elements safe, you may as well just use one 240V rated SSR instead of two, and leave one  end of the load connected to one leg of the supply, this saves you half the heat load in the control box as each SSR will drop around a volt, so at 30A will be burning off 30W as heat.
 

Offline floobydust

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Re: I fried my SSR........ HELP!!!
« Reply #16 on: January 25, 2020, 07:49:14 pm »
I drew a circuit and realized you may have wired the heating elements wrong. How many ohms are they each, or as a quad? Originally they have might been wired in pairs, as 120V elements each? This could overcurrent the SSR.

I have a few issues with safety, the galvanized enclosure and kiln must both be grounded.
Why are you using cheapola PVC speaker wire when this enclosure sure looks like it gets very hot. The indicator lamps have high temp wire so I'm worried the whole thing will melt.

Can you touch the heating elements (when the kiln is cold) ? Usually this is the case, when putting stuff in or out of the kiln. Using SSR's (instead of a contactor) there can be an electrocution hazard due to the SSR's leakage current putting stray voltage at the heating elements, despite the SSR's being off. You'll need to measure ACV at the heater when the controller is off, to make sure.
 

Offline DBecker

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Re: I fried my SSR........ HELP!!!
« Reply #17 on: January 25, 2020, 07:52:55 pm »

SSRs are not usable as isolation, so given you need a separate isolation switch to make touching the elements safe, you may as well just use one 240V rated SSR instead of two, and leave one  end of the load connected to one leg of the supply, this saves you half the heat load in the control box as each SSR will drop around a volt, so at 30A will be burning off 30W as heat.

Most SSRs are rated for and suitable for line isolation.  Internally they use an opto-triac.  Most types have excellent isolation at very low cost, with the circuit board layout generally being the weak point rather than the component.

A kiln will have incompletely shrouded heating elements, so both sides of the supply will need to be switched, likely including a safety switch on the lid hinge.
 

Offline james_s

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Re: I fried my SSR........ HELP!!!
« Reply #18 on: January 25, 2020, 07:55:19 pm »
Almost all of those low cost Chinese SSRs will have a 10A triac in them regardless of what the label says. There is no need to explore other options until this part is taken care of, if you look at the bottom of the SSR and see the end of a screw that is a dead giveaway that internally it contains a standard TO220 triac instead of a proper design with the die bonded to the plate. there is no way that a 10A triac is going to control a 30A heating element without burning up, that is your problem.
 

Offline floobydust

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Re: I fried my SSR........ HELP!!!
« Reply #19 on: January 25, 2020, 08:07:48 pm »

SSRs are not usable as isolation, so given you need a separate isolation switch to make touching the elements safe, you may as well just use one 240V rated SSR instead of two, and leave one  end of the load connected to one leg of the supply, this saves you half the heat load in the control box as each SSR will drop around a volt, so at 30A will be burning off 30W as heat.

Most SSRs are rated for and suitable for line isolation.  Internally they use an opto-triac.  Most types have excellent isolation at very low cost, with the circuit board layout generally being the weak point rather than the component.

A kiln will have incompletely shrouded heating elements, so both sides of the supply will need to be switched, likely including a safety switch on the lid hinge.

It's not the isolation I'm talking about, it's the leakage currents from the triac and snubber that are significant in any SSR. They flow mA's when off and that's enough to keep a floating load hazardous live.

I think OP should have a Neutral wire in there and the heaters may be all be 120V elements. Have to check the kiln's make and model to see how it was originally wired.
 

Offline jwilsonTopic starter

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Re: I fried my SSR........ HELP!!!
« Reply #20 on: January 25, 2020, 08:14:58 pm »
I drew a circuit and realized you may have wired the heating elements wrong. How many ohms are they each, or as a quad? Originally they have might been wired in pairs, as 120V elements each? This could overcurrent the SSR.

I have a few issues with safety, the galvanized enclosure and kiln must both be grounded.
Why are you using cheapola PVC speaker wire when this enclosure sure looks like it gets very hot. The indicator lamps have high temp wire so I'm worried the whole thing will melt.

Can you touch the heating elements (when the kiln is cold) ? Usually this is the case, when putting stuff in or out of the kiln. Using SSR's (instead of a contactor) there can be an electrocution hazard due to the SSR's leakage current putting stray voltage at the heating elements, despite the SSR's being off. You'll need to measure ACV at the heater when the controller is off, to make sure.

For the elements, they are 8 ohms. 

Here's a link to the elements https://www.paragonweb.com/ELA82.cfm

I changed out the speaker wire........ I now realize that was a horrible idea. I'm using 16 ga primary wire to run power from the SSR to the PID.

I haven't tried to touch the elements when they are live. Due to my mistakes, I can't now until I wire it up properly.

I wish I could pay one of you guys to come over and help me wire this thing up!!!!! I'm in Fayetteville, AR.

Anyone close????  ;D

 

Offline jwilsonTopic starter

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Re: I fried my SSR........ HELP!!!
« Reply #21 on: January 25, 2020, 08:18:59 pm »
I drew a circuit and realized you may have wired the heating elements wrong. How many ohms are they each, or as a quad? Originally they have might been wired in pairs, as 120V elements each? This could overcurrent the SSR.

I have a few issues with safety, the galvanized enclosure and kiln must both be grounded.
Why are you using cheapola PVC speaker wire when this enclosure sure looks like it gets very hot. The indicator lamps have high temp wire so I'm worried the whole thing will melt.

Can you touch the heating elements (when the kiln is cold) ? Usually this is the case, when putting stuff in or out of the kiln. Using SSR's (instead of a contactor) there can be an electrocution hazard due to the SSR's leakage current putting stray voltage at the heating elements, despite the SSR's being off. You'll need to measure ACV at the heater when the controller is off, to make sure.

FLOOBYDUST, I can't thank you enough for the schematic!!!! I have a new SSR coming tomorrow and I'm going to leave well enough alone until I get it and then wire according to your schematic.

Thank you so much!
 

Offline jwilsonTopic starter

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Re: I fried my SSR........ HELP!!!
« Reply #22 on: January 25, 2020, 08:25:22 pm »
I drew a circuit and realized you may have wired the heating elements wrong. How many ohms are they each, or as a quad? Originally they have might been wired in pairs, as 120V elements each? This could overcurrent the SSR.

I have a few issues with safety, the galvanized enclosure and kiln must both be grounded.
Why are you using cheapola PVC speaker wire when this enclosure sure looks like it gets very hot. The indicator lamps have high temp wire so I'm worried the whole thing will melt.

Can you touch the heating elements (when the kiln is cold) ? Usually this is the case, when putting stuff in or out of the kiln. Using SSR's (instead of a contactor) there can be an electrocution hazard due to the SSR's leakage current putting stray voltage at the heating elements, despite the SSR's being off. You'll need to measure ACV at the heater when the controller is off, to make sure.

One more question, your schematic includes everything I need, but how about the AC lines going to terminals 9 and 10?

Here the PID I'm using:  https://www.auberins.com/images/Manual/SYL-2352P%20Manual.pdf

Thanks again.
 

Offline floobydust

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Re: I fried my SSR........ HELP!!!
« Reply #23 on: January 25, 2020, 08:26:00 pm »
WAIT - that's a schematic based on your picture, what you wired up. Not how it should be- I'd have to think about it. The heaters surely aren't all in parallel! Groan.

Inkbird 40A SSR reviews are pretty funny on Amazon. They seem to smoke and melt.
"Got two of these in succession, both caught fire filling the air with acrid smoke! First one, than the second one a few months later as well. Too late for Amazon refund."
"Melted on first use, despite heat sink. Unable to brew beer until I get it replaced, this is the second 40A Inkbird SSR to go bad on me, 0 for 2."
"This SSR should have been over powered for the setup I put it into but it failed about 15 minutes after being turned on. The system was drawing 6.3 amps @ 238v when it popped and failed. The 10 amp inline fuse didn’t have a chance to protect this 40 amp switch..."
 

Offline jwilsonTopic starter

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Re: I fried my SSR........ HELP!!!
« Reply #24 on: January 25, 2020, 08:35:15 pm »
WAIT - that's a schematic based on your picture, what you wired up. Not how it should be- I'd have to think about it. The heaters surely aren't all in parallel! Groan.

Inkbird 40A SSR reviews are pretty funny on Amazon. They seem to smoke and melt.
"Got two of these in succession, both caught fire filling the air with acrid smoke! First one, than the second one a few months later as well. Too late for Amazon refund."
"Melted on first use, despite heat sink. Unable to brew beer until I get it replaced, this is the second 40A Inkbird SSR to go bad on me, 0 for 2."
"This SSR should have been over powered for the setup I put it into but it failed about 15 minutes after being turned on. The system was drawing 6.3 amps @ 238v when it popped and failed. The 10 amp inline fuse didn’t have a chance to protect this 40 amp switch..."

DOH.... I thought your schematic was how it SHOULD be wired up.

Definitely time to invest in better SSR's.........

How should the elements be wired?

There are four in total, with 2 leads on each.

I am attaching a pic of what the element arrangement looks like.

I can't thank you enough for all your help!!!

I owe you lots and lots of beers!!!
 


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