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ronfire

Solid state relays

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Kicking around the idea of getting rid of the sitter and build in a Genesis 3 zone controller on my Skutt kiln. Looking into solid state relays for a longer relay life span and less issues. Anyone run these on there kiln? I know they cost 3 -4 times as much but if they last it would be worth it.

Looking at maybe using there for each zone.

264295375_ScreenShot2020-06-01at7_53_42PM.png.cc73795d47c7cad2428d83f03106101b.png

 

Edited by ronfire
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Just now, ronfire said:

Kicking around the idea of getting rid of the sitter and build in a Genesis 3 zone controller on my Skutt kiln. Looking into solid state relays for a longer relay life span and less issues. Anyone run these on there kiln? I know they cost 3 -4 times as much but if they last it would be worth it.

 

Go for it!  You need to be able to cool them, actively.  That means using a fan.  If your control box is mounted to the kiln, the interior of the control box is too hot for passive cooling.  At least on my kiln.  I was thinking about using them but measured my control box at cone 6 and it was a balmy 120 degrees, which would not be ideal for passive cooling (heat sink).

To me, adding solid state relays, heat sinks and fans was just adding 3 more points of failure, but done correctly I'm sure they would do really well.  I just don't trust myself with that :lol:

 

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Could use these with the heat sink and mount so the heat sink is outside the control box but they are not a double pole relay.

 

 

 

152445360_ScreenShot2020-05-31at7_11_37AM.png.ef68efee7ec1f2a85298e54390714a9a.png

Edited by ronfire

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I think you can either raise the amperage capacity of the relay or raise the cooling to compensate.  The higher the amperage being put through it, the hotter it gets, so if it's a 30 amp ssr, and you're putting 30 amps through it, you need to have very active cooling.  This means fans and heat sink.

If you get an 80 amp ssr, and put 30 amps through it, you may be able to get by with passive.cooling

Hope that makes sense...when I was shopping around for SSRs I would see one that says 50 amp, but when looking at the specs it was 50 amps at 25 celsius, which could only exist under ideal circumstances with active cooling.

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10 hours ago, ronfire said:

Kicking around the idea of getting rid of the sitter and build in a Genesis 3 zone controller on my Skutt kiln. Looking into solid state relays for a longer relay life span and less issues. Anyone run these on there kiln? I know they cost 3 -4 times as much but if they last it would be worth it.

Looking at maybe using there for each zone.

264295375_ScreenShot2020-06-01at7_53_42PM.png.cc73795d47c7cad2428d83f03106101b.png

 

They work well in industry and have some minor drawbacks. For safety they need a mechanical means to positively shut them off as they can fail in the closed position more so than mechanical relays which occasionally fail that way. Common method is a lid switch integrated into a safety loop. All hard wired stuff for reliability. Finally protecting the relays themselves requires proper fuses that quickly blow else the relay itself is not protected. Not really a big deal to add the fuses actually and these are becoming so cheap folks may just accept replacing them if the unlikely short occurs in the kiln. Finally thermal management is super important so the size relay you need is fine but requires a whole lot of heatsink to be proper.

As a favor and at request we made a video of some of the things it took to design. They definitely have benefits and mostly only come on expensive kilns at this point. Price point for us as a diy design / install was about three hundred bucks for two kilns I believe.

At some point I will likely do this as a favor for a trusted studio. It’s just relays are so cheap and easy to change quickly I am not sure when.

 

Edited by Bill Kielb

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9 hours ago, liambesaw said:

I think you can either raise the amperage capacity of the relay or raise the cooling to compensate.  The higher the amperage being put through it, the hotter it gets, so if it's a 30 amp ssr, and you're putting 30 amps through it, you need to have very active cooling.  This means fans and heat sink.

If you get an 80 amp ssr, and put 30 amps through it, you may be able to get by with passive.cooling

Hope that makes sense...when I was shopping around for SSRs I would see one that says 50 amp, but when looking at the specs it was 50 amps at 25 celsius, which could only exist under ideal circumstances with active cooling.

There are some tricks and with most ambient temps around kilns passive cooling is possible and can even be well over designed. It definitely takes external mounting of the heatsink and the heatsink itself ends up larger than expected. Passive however is reliable as active that depend on fans, not so much.

Edited by Bill Kielb

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Wall mount definitely will keep the controller and relays cooler but there are a lot of wires to the kiln for a 3 zone system..

Great video posted Bill, Thank you.

 

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27 minutes ago, ronfire said:

Wall mount definitely will keep the controller and relays cooler but there are a lot of wires to the kiln for a 3 zone system..

 

You can zip tie the TC wires together, even tie them to the power cord, so it's not messy.

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Was thinking, could run inside a conduit with all the other cables, or the flex conduit.

Would that interfere with the TC signals?

 

 

Edited by ronfire

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1 hour ago, ronfire said:

Was thinking, could run inside a conduit with all the other cables, or the flex conduit.

Would that interfere with the TC signals?

 

 

No, greenfield or flexible metal conduit will be fine for the high voltage and tie wrapping the TC wires to it would be great or you could stuff them in another piece of greenfield. Honestly even though remote mounting could be cooler, we found that mounting the heatsink near the very bottom of the kiln ended up to be great with a fantastic updraft created by the kiln. This solved a lot of issues as all the wiring that needs to be around the relays, etc... was easiest to keep in the current control box. The kilns we looked at though have a control box that is full length top to bottom. Our thermal solution was a very large heatsink from heatsink USA that was about double the expected thermal capacity. We intended to mount outside the kiln with the SSR’s inside and the control box cut Out in the areas of the SSR So the SSR was mechanically attached to the heatsink. We would also improve the thermal performance of the relays and heatsink by polishing with 1000 grit on a piece of glass, but that is an old trick and overkill actually.

For remote install Electrically It  needs to stay within 6 feet of the kiln For code and generally folks mount it 4 feet above the floor which often ends up hotter than near the bottom of the kiln..

All ways work however, I would suggest spending time on the safety aspect and adding a contactor and overkill on the thermal management of the relays.

Edited by Bill Kielb

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Hi Bill, Sounds like you have done a few conversions.  I like the idea of a tall control box with the relays and heat sinks at the bottom. I was planning on using a mechanical contractor to feed the 3 zone relays .  If I kiln mount the conversion I may remove the existing boxes,switches ect and start with a whole new case up, wall mount I would just tie into the switch location and bypass the rest. I do like the idea of a clean start and strip the kiln back. I have a Skutt 1027 that is in great shape and just changed the elements. Any experience with the lower priced SSR on Amazon? I like DigiKey but their SSR is $133  cdn for the Crydon but Amazon has some for $25 with the same specs.

Will there be much difference in the element life between the sitter or a controller, I know the sitter uses 3 of the elements more but they do not get cycled like a controller.

My other option I might look at is just getting a new  Skutt or L&L kiln, but a custom control system that I am thinking of would give less problems with the SSR and save a lot of $$.

Not in a rush for this project yet as I want to do it right and safe but it still has to be worth it for the money.

 

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16 hours ago, ronfire said:

Hi Bill, Sounds like you have done a few conversions.  I like the idea of a tall control box with the relays and heat sinks at the bottom. I was planning on using a mechanical contractor to feed the 3 zone relays .  If I kiln mount the conversion I may remove the existing boxes,switches ect and start with a whole new case up, wall mount I would just tie into the switch location and bypass the rest. I do like the idea of a clean start and strip the kiln back. I have a Skutt 1027 that is in great shape and just changed the elements. Any experience with the lower priced SSR on Amazon? I like DigiKey but their SSR is $133  cdn for the Crydon but Amazon has some for $25 with the same specs.

Will there be much difference in the element life between the sitter or a controller, I know the sitter uses 3 of the elements more but they do not get cycled like a controller.

My other option I might look at is just getting a new  Skutt or L&L kiln, but a custom control system that I am thinking of would give less problems with the SSR and save a lot of $$.

Not in a rush for this project yet as I want to do it right and safe but it still has to be worth it for the money.

 

I like the pre made because their engineering includes all the compliance issues already addressed to an acceptable level. Crydom has been in the bus. forever so their reputation is good. Having said that lots of my orders have been through automation direct and whoever their vendor is has worked out well. Making your own setup is great and using the existing control box often works out but separating the hot and cold plane effectively so all your stuff stays cool takes  a bit of work. I have infrared cameras and cool measurement devices so when I am done I can check my design assumptions.

Definitely doable And an interesting project  but needs lots of thought as well. I am not sure of the additional firings with respect to a sitter. For situations where your infinite switch is cycling the elements rather than a relay the sitter and electronic controller are likely similar from a longevity standpoint. 
SSR’s have greater switching speed so that should improve your distribution of heat as well as overall firing speed. Zero crossing firing should help with element longevity as well. The current problem is mechanical relays are cheap and last a reasonable amount of time .

Edited by Bill Kielb

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I have also been looking at some used kilns as well. Just saw a 3 year old Skutt 1231 for $3300 cdn. Trying to find out more about it and asked for photos of the decal plate and interior. I understand that it would be a PK kiln as that is all Skutt lists.

That kiln sure draws power but it hold almost twice what my 1027 does.

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After pricing the components it comes out cheaper to just buy the wall mount or sitter delete units and they are aproved. But I think the better option is for $2500 mor I van have a new kiln :P   Guess I will look in the fall after the border opens so I can pick it up.

 

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