Solid State Relay Conversion

[Bill Kielb]

11 hours ago, ronfire said:

Would there be a problem with adding an LED indicator light to the output of the ssr on the 220v side to monitor the output to the kiln or elements. I was looking at maybe one of these. I know if you run with the ssr it would have a short cycle time.

 

 

 

It would be fine. Many SSR's have indicators on them. 2 seconds between a second energization I believe, not too fast for this LED if I understand your question. It would illuminate for a few seconds then go out during peak speed switching. Problem with adding this to a high amperage output is how do you protect it? Tiny little wires burn up long before the circuit trips and 240 means two fuses. Indicators are often on the low voltage side with a current doughnut on output (high voltage) side fully decoupled. I have some super economy indicator light style digital that would allow one to know how worn their elements are. Will post later.

@ronfire  added some voltage and current meters. Don’t forget 1/4 amp or less glass fuse each leg for the voltage meters to protect the small wires. Also would need,to keep the wire away from kiln heat, just not rated for it. So a little thought and planning is required to stay safe.

@ronfire added fuse holder - be safe

[ronfire]

Well I decided to build a wall mount unit for my Skutt 1027-3   48 amps.  I will use the Bartlett Genesis with a Square D 50 amp resistant load contactor driven with a pilot relay.

Was thinking of the Omega 75 amp 24-280 volt SSR on a large heat sink with the heat sink mounted outside the control box. Would make a hole in the control box to allow the SSR to contact the heat sink mounted on the outside. Omega has another SSR for $10 more that is rated 48-660 v 75 amp, wondering if that would be a better choice for a few $9.00 more.  The Omega SSR use 2 SCRs instead of the Triacs for better performance they claim. The kiln is run with a 60 amp breaker so I was thinking I would not require fuses on the SSR as it would be a 75 amp.

The  FD5-24 transformer should produce enough to power the board and 2 relays protected by a fuse and switched to be able to shut down the controller.

Would be nice if I could tie in the digital amp meter  that is listed above to the Genesis controller.

If I put in an indicator light I was thinking of placing it on the output side of the SSR to be able to easily see if there is a power issue to the Kiln, might be over kill.

Also was going to remove the cone sitter and place in the thermocouple, saves placing another hole in the kiln. Wire in the supplied power from the wall mount to the output side of the sitter to bypass the sitter controls and not have to use the timer.

Found a reasonably priced hinged steel box for the enclosure, wish I could find a good priced one from aluminum instead so it would add to the heat sink.

All 220V cables would be direct wired with no plugs.

 

[Bill Kielb]

1 hour ago, ronfire said:

Well I decided to build a wall mount unit for my Skutt 1027-3   48 amps.  I will use the Bartlett Genesis with a Square D 50 amp resistant load contactor driven with a pilot relay.

Was thinking of the Omega 75 amp 24-280 volt SSR on a large heat sink with the heat sink mounted outside the control box. Would make a hole in the control box to allow the SSR to contact the heat sink mounted on the outside. Omega has another SSR for $10 more that is rated 48-660 v 75 amp, wondering if that would be a better choice for a few $9.00 more.  The Omega SSR use 2 SCRs instead of the Triacs for better performance they claim. The kiln is run with a 60 amp breaker so I was thinking I would not require fuses on the SSR as it would be a 75 amp.

The  FD5-24 transformer should produce enough to power the board and 2 relays protected by a fuse and switched to be able to shut down the controller.

Would be nice if I could tie in the digital amp meter  that is listed above to the Genesis controller.

If I put in an indicator light I was thinking of placing it on the output side of the SSR to be able to easily see if there is a power issue to the Kiln, might be over kill.

Also was going to remove the cone sitter and place in the thermocouple, saves placing another hole in the kiln. Wire in the supplied power from the wall mount to the output side of the sitter to bypass the sitter controls and not have to use the timer.

Found a reasonably priced hinged steel box for the enclosure, wish I could find a good priced one from aluminum instead so it would add to the heat sink.

All 220V cables would be direct wired with no plugs.

 

I will get my old parts list and share. Automation direct had decent pricing and my contactor was rated 65 amps resistive. I believe it was very economically priced. Also Heatsink USA had the cheapest per inch and you just order X number of inches to more than cover the load. Very economical as well. I will bring up my BOM from the site and forward to you. You might find it useful.  Likely won’t get to it till tonight though

[ronfire]

My problem is cross boarder shipping to Canada. USPS is ok but courier is a rip off.

 

[Bill Kielb]

16 hours ago, ronfire said:

My problem is cross boarder shipping to Canada. USPS is ok but courier is a rip off.

 

Yeah, not sure this helps but automation direct ships to the US and Canada.

[ronfire]

Do you think a 75 amp SSR is enough for a 48amp kiln or should I up it to a 90 amp.  Read someplace that it is recommended to us only 70% of the rating, that calculate to 52 amps. Gets close to max then.

My son is getting me a couple of server heat sinks, should be able to use them for the SSR. They will most likely be copper or copper based, if I have to I can always mount the 2 on a copper plate to make them fit.

Thanks Bill for all the advise on electronics, sure appreciation the knowledge. Is this what you taught in school?

 

 

[Bill Kielb]

1 minute ago, ronfire said:

Do you think a 75 amp SSR is enough for a 48amp kiln or should I up it to a 90 amp.  Read someplace that it is recommended to us only 70% of the rating, that calculate to 52 amps. Gets close to max then.

My son is getting me a couple of server heat sinks, should be able to use them for the SSR. They will most likely be copper or copper based, if I have to I can always mount the 2 on a copper plate to make them fit.

Thanks Bill for all the advise on electronics, sure appreciation the knowledge. Is this what you taught in school?

 

 

I taught HVAC, long story, studied engineering ( electrical - primary) was an electrician early in life who went back to school but minored in mechanical and civil. Guess I always liked engineering actually. Applied my skills in construction and built a bunch of ordinary buildings, mainly commercial For 30 years to make money. All the engineering provided an advantage in construction but I always taught (part time - 20 years JC, HVAC) so mostly mixed up and confused actually.

The funny story is I began teaching- HVAC testing adjusting and balancing at the JC because no one liked all the math, Interesting story in that my high school counselor said maybe get a physical job as a mover or something he didn’t see much potential I guess.  Always took that as a challenge so became proficient  in math and was able to teach TAB to technicians without emphasizing the math as much as being able to solve problems real world and understanding the basic physics of the processes they were encountering so they could troubleshoot effectively and learn the adjust by the numbers part. Perfect fit actually My motto was if I can learn it anyone can. A job I truly enjoyed .

Most of my work now is consulting or currently HVAC oversight in energy management. Lots of young engineers straight out of school, very smart, little field experience. Turning out to be a very rewarding fun job right now. I am pretty lucky actually. I will log kn and send you whatever parts I had in my BOM by PM. I Believe I picked  the 40 amp SSRs  For my 20 amp loads following the reasonable over design idea.

As far as heatsink, heatsink USA has them cheap by the inch with actual  ratings per inch. For three SSR’s I thunk I had an eight inch wide by 12-16” Long  sink Picked out which doubled my required capacity with 85 - 90 degree ambient air.

As far as heat transfer, good machining better than thermal paste and indium is probably one of the easiest and best. Simple hand prep of the mating surface improves conductivity far beyond the paste or pad.

video here at about 8:00 -  9:00 min in Is an old technique but far superior to anything you buy off the shelf with regard to keeping things cool.

 

[ronfire]

Interesting video, would definitely polish the contact points. Makes sense.

 

[ronfire]

Looking to connect a wall control to the Sitter but eliminate the use of the sitter controls.

I was going to connect the power leads to the other side of the shunt block  and use like a terminal block to eliminate the use of the sitter but was wondering about the timer. Don't understand how it works in the circuit as it looks like it would create a short in the operation . I know I could disconnect it to eliminate it but not sure why it works.

Also planning on removing the sitter tube and replace it with the Thermocouple.

 

 

[Bill Kielb]

50 minutes ago, ronfire said:

Looking to connect a wall control to the Sitter but eliminate the use of the sitter controls.

I was going to connect the power leads to the other side of the shunt block  and use like a terminal block to eliminate the use of the sitter but was wondering about the timer. Don't understand how it works in the circuit as it looks like it would create a short in the operation . I know I could disconnect it to eliminate it but not sure why it works.

Also planning on removing the sitter tube and replace it with the Thermocouple.

 

 

The timer needs power to run the timer motor, it mechanically turns off the sitter

 

[neilestrick]

The timer is just a countdown timer that has a little pin that trips a spring mechanism that trips the power button. You can't just use the sitter as a terminal block, because the two sides of the block don't have continuity unless the power button is engaged. So you'd still have to use the sitter to some degree.  When I do these I remove the entire sitter, make a plate to cover the hole, and just put in a simple terminal block to connect the element feeder wires to the power cord.

[Mark C.]

(Square D 50 amp resistant load contactor )

Since the draw is  48amps is this thing going to hold up over time? seems like a weak point.

[Bill Kielb]

36 minutes ago, Mark C. said:

(Square D 50 amp resistant load contactor )

Since the draw is  48amps is this thing going to hold up over time? seems like a weak point.

Nope, but hopefully this is a 50 amp AC rated which would put it more like 65 amps resistive. If it acts as a safety and only cycles once per firing then it lasts forever. If you cycle the elements with it, it likely fails as predicted or before- MTBF (Mean Time Between Failure)

[neilestrick]

43 minutes ago, Mark C. said:

(Square D 50 amp resistant load contactor )

Since the draw is  48amps is this thing going to hold up over time? seems like a weak point.

The Skutt KM-1 wall mount controller uses a 50amp resistive relay and they tend to last many years. They don't get as hot since they're far from the kiln.

[Bill Kielb]

@neilestrick
MTBF is pretty high with most relays extending into the tens and hundreds of thousands of cycles. Most of this is dependent on frequency and ultimate load that is switched on and off.  Most relays are rated for Max inductive loads and pure resistive is higher just because it is so much easier on the contacts. I suppose skutt  could use a 50  Amp resistive rated relay, but then it would carry a high 30 amp Inductive load rating off  the shelf, so to speak  which would be a decision of economy. I guess if you are sticking it in box that will handle up to as they say 50 amps resistive then no worries to not over design it. Either way, if they do, it’s a bit disappointing but I certainly understand the economics of it and rarely in its life will it be switching a full 50 amps so it should work for many cycles. If you are doing this for yourself, the cost is nearly insignificant, oversize it would be my suggestion.

Same complaint I have about powering and insulating kilns actually. When you think about losing 10% of your power often means you can’t make the intended firing cone. Kilns have been designed marginally for many years, disappointing actually for potters that just want to fire their stuff. I can’t really think of any ordinary industry design where we use the actual load and not provide at least a 20% factor of over design in some way ......... except for kilns that is. We design them all at 110% heating capacity. Go figure!

[ronfire]

I was looking at the wiring diagram of the timer and saw 2 leads, not thinking they where to power up the timer.

I was going to move the power leads to the other side of the shunt block so it becomes a buss bar instead and directly feeds power to the switches that will be left on high.

Looking forward to not having to run out to the kiln all the time and be able to monitor it from my phone.

 

Decided to use output 4 on the Genesis to run the fan. Instead of using power from the 220 input I will run a piggyback plug that are on the float switches. I wont have to add fusses to the system to run 15 amp plug, it will draw power from the wall plug.

 

 

 

[neilestrick]

8 hours ago, Bill Kielb said:

@neilestrick
Same complaint I have about powering and insulating kilns actually. When you think about losing 10% of your power often means you can’t make the intended firing cone. Kilns have been designed marginally for many years, disappointing actually for potters that just want to fire their stuff. I can’t really think of any ordinary industry design where we use the actual load and not provide at least a 20% factor of over design in some way ......... except for kilns that is. We design them all at 110% heating capacity. Go figure!

It's just economics. Consumables is where the money is long term, and elements are the primary consumable in kilns, so they don't necessarily want to design them to last forever. Plus the vast majority of kilns are made to be plug-and-play, so there's a limit to how powerful you can make them. The most popular size kiln sold in the US is the 23x27, 7 cu ft model. You can't make it more powerful without it having to be hard wired, plus at over 50 amps they have to have branch fusing in the control box, both of which drive up the price. It's all a balance between function and cost. They can make kilns with super heavy duty elements, lots of power, solid state relays, 6 inch thick walls, type S thermocouples, etc, etc, but there's no market for all that with the exception of a handful of people like you and me who geek out on that stuff. They're making Toyotas, not Ferraris.

[Bill Kielb]

58 minutes ago, neilestrick said:

It's just economics. Consumables is where the money is long term, and elements are the primary consumable in kilns, so they don't necessarily want to design them to last forever. Plus the vast majority of kilns are made to be plug-and-play, so there's a limit to how powerful you can make them. The most popular size kiln sold in the US is the 23x27, 7 cu ft model. You can't make it more powerful without it having to be hard wired, plus at over 50 amps they have to have branch fusing in the control box, both of which drive up the price. It's all a balance between function and cost. They can make kilns with super heavy duty elements, lots of power, solid state relays, 6 inch thick walls, type S thermocouples, etc, etc, but there's no market for all that with the exception of a handful of people like you and me who geek out on that stuff. They're making Toyotas, not Ferraris.

Understood,  but insulate it 10% better and voila it now is engineered for 120% Heating capacity.  Maybe 30% and now you can lob off 10% of the wattage and still be 120% of design. It will come eventually, kilns are basically uninsulated or poorly so, so achieving this with 1” material or 2” extra exterior size is very doable.  Eventually I am sure at a price. Energy is too cheap to make it attractive  and competitive right now but we will get there I believe. Toyota’s were rust buckets, now they are high quality cars that American brands finally were forced to compete with. Go figure!

[neilestrick]

13 hours ago, Bill Kielb said:

Understood,  but insulate it 10% better and voila it now is engineered for 120% Heating capacity.  Maybe 30% and now you can lob off 10% of the wattage and still be 120% of design. It will come eventually, kilns are basically uninsulated or poorly so, so achieving this with 1” material or 2” extra exterior size is very doable.  Eventually I am sure at a price. Energy is too cheap to make it attractive  and competitive right now but we will get there I believe. Toyota’s were rust buckets, now they are high quality cars that American brands finally were forced to compete with. Go figure!

I think we're working towards better kilns, but it's slow. A big part of the problem is that materials costs keep going up quickly. The cost of making a kiln gets higher every year without any improvements at all. But as attitudes about efficiency change, there will be a place in the market with people who are wiling to pay for a premium product if it means it will last longer and be easier and less expensive to maintain.

I think we're starting to evolve away from the disposable market, albeit slowly. We all remember when appliances lasted 30 years or more.