Skutt GlazeTech kiln issues. Relay still clicks but output voltage not as expected?

[cadenrank]

I have been helping a friend with doing some testing on her Skutt GlazeTech kiln. To give some back story, the kiln originally started throwing an ERR1 code, she's replaced elements and thermocouple, and that didn't solve it, Skutt told her that it was more than likely the mechanical relay, and she replaced it. ERR1 continued. Skutt said they didn't think it would be the case, but told her to replace the solid state relay as well. She did, and it was running fine for a few weeks, and now once again has failed with ERR1. The kiln will not rise in temperature at all anymore, and eventually ERR1's all programs given to it within 20 minutes or so without any increase in temp. 

It was tested at the elements, and resistance was as expected. Voltage between the two terminals that lead to the elements was 10.1vAC. Opened it up further, and did some tests inside.
Incoming voltage was 243vAC.
With a program running, the control wires from the controller to the SSR were 16.5vDC, and the control wires from the controller to the mechanical 'safety' relay was also 16.5vDC.
When the program was running (and TC still attached)  voltage at the middle (input) terminals of the mechanical relay were 240v, and the output was 10.1vAC. 
Voltage (with program running) at the SSR, between the output side and ground was 120v when the relay was active, and 47v when the relay was open. When there was no program running, the output side of the SSR and ground was also 47v. I thought this was odd, but no less odd than the 10.1vAC out of the mechanical relay to the elements.

My conclusion from testing was that the mechanical 'safety' relay has failed. The relay clicks, but there is no continuity between any of the input and output pins when the control side is energized, and the output side is 10.1vAC when it's energized. 

So here's what still doesn't have me 100% on the diagnosis. The mechanical safety relay clicks still when the controller energizes it. And receives the 240v input, but only gives 10.1v across it on the outputs. The other part is that this relay is only a month old with 8 firings on it. The other part is that I'm unsure if that 47v on the SSR when it's deenergized by the controller is normal. Skutt's documentation in this field is poor. 

At this point I'm 95% certain the mechanical relay is at fault for the failure to provide power to the elements and the current Err1 code, but would like some reviews of the data collected, from you folks and see if you agree with that diagnoses and what you think about the other anomalies that were recorded. 

Below is the wiring diagram for reference. 

12.700-GlazeTech-1ph.pdf

Edited August 7, 2022 by cadenrank

[cadenrank]

This is a modified version of the wiring diagram that shows the voltage measurements taken with a program running and where they were taken relative to the original wiring diagram attached to my first post. 

[neilestrick]

With the firing off, you shouldn't be getting any voltage from the output of the SSR, so I think you must be getting something coming through the mechanical relay. The relay can still click even if it's having problems, so that's not unusual. I agree that the problem is probably the mechanical relay. What model is the relay- the typical one they use in all their kilns? It could be you got a bad one, or it could be that there was a bad connection the caused it to overheat. FYI, don't have to buy those relays from Skutt or any kiln manufacturer/dealer. You can find them for half the price or less online. Just search the part number, or I use THESE. They hold up better than some of the others I've used.

[cadenrank]

1 minute ago, neilestrick said:

With the firing off, you shouldn't be getting any voltage from the output of the SSR, so I think you must be getting something coming through the mechanical relay. The relay can still click even if it's having problems, so that's not unusual. I agree that the problem is probably the mechanical relay. What model is the relay- the typical one they use in all their kilns? It could be you got a bad one, or it could be that there was a bad connection the caused it to overheat. FYI, don't have to buy those relays from Skutt or any kiln manufacturer/dealer. You can find them for half the price or less online. Just search the part number, or I use THESE. They hold up better than some of the others I've used.

When the program was off, but the kiln was still powered, I believe the output of the SSR still had 47vAC to ground. (This was the only way I could think to test it since it only switches one leg of the 240v on the SSR.). I'd have to go back and look for certain, but I believe when the SSR was deenergized (0.4 or less vDC from the controller) but the kiln was still powered, there was 100vAC across the inputs of the mechanical relay. It wasn't tested from each leg of the inputs to ground, but I'd assume one was 47v, and the other 120v. Which went to 240v when the SSR was switched closed when the program was running. I thought this part was odd. 

It's the clear Deltrol relay as the 'safety' mechanical relay. It's a Deltrol 20850-81. The SSR is a Crydon CSW2475. 

I always imagined that clicking would mean that the contacts were closing, but I suppose that doesn't mean that the contacts are able to carry current appropriately. 

[cadenrank]

Other than the voltage only dropping out to 47vAC from the SSR switched leg, the controlled side of the equation seemed to be working as I'd expect. And when control was telling the SSR to close, the voltage at the inputs on the mechanical safety relay were good. Just nothing (10.1v) on the outputs. 

[neilestrick]

Ah, they're using the clear relays they used on the older kilns. You can get those HERE. Not as cheap as the black relays, but cheaper than from Skutt. I'd buy two in case something goes wrong again. If you blow another one, check all the wiring connections and make sure nothing has come loose. All the slip-on connectors should be snug, so if necessary crimp them down a little with some needle nose pliers before slipping them on. Make sure no connectors have come loose from their wires.

How long did the kiln go before this problem started happening- how many firings did she get from the first relay? Is the control box on that kiln that same size as on the non-SSR model? If so, that's a tiny little control box without much ventilation. The SSR has a heat sink, correct? But the mechanical relay is not getting much cooling because the box is short and doesn't create much chimney action. So you may want to consider adding a small fan to the system if the relay is dying prematurely. You can get a small computer case fan and mount it to the bottom of the control box on the outside, and wire it through the safety relay so it's on whenever the relay is on. If there are louvers on the bottom of the box it can just blow through those, or cut a hole for it if necessary.

[cadenrank]

2 minutes ago, neilestrick said:

Ah, they're using the clear relays they used on the older kilns. You can get those HERE. Not as cheap as the black relays, but cheaper than from Skutt. I'd buy two in case something goes wrong again.

I will pass that information along to her. Thank you! 

 

3 minutes ago, neilestrick said:

How long did the kiln go before this problem started happening- how many firings did she get from the first relay? Is the control box on that kiln that same size as on the non-SSR model? If so, that's a tiny little control box without much ventilation. The SSR has a heat sink, correct? But the mechanical relay is not getting much cooling because the box is short and doesn't create much chimney action. So you may want to consider adding a small fan to the system if the relay is dying prematurely. You can get a small computer case fan and mount it to the bottom of the control box on the outside, and wire it through the safety relay so it's on whenever the relay is on. If there are louvers on the bottom of the box it can just blow through those, or cut a hole for it if necessary.

I'm unsure how long before this started happening prior to this time. However, I know she said she moved in January, and it had been working normally up until a month or so ago, and she had said she had the kiln for about 3 years prior to the move. Then the elements and everything were replaced when the issue presented itself, then both relays. The relays have only been installed for 1 month or 8 firings she said. And the past month of firings had been normal until she messaged me today, where it had failed to ERR1 again, and then upon trying to restart, didn't gain any temp at all. 

It is the same small size control box. Louvers on top and bottom. There is a form of heat sink, it's mostly just a large metal piece that has a 1 inch air gap behind it that spans the whole area there though, not dedicated to the SSR. The safety relay, SSR, terminal block, and transformer are all mounted to this sheet of metal. 

[cadenrank]

And just talked with her, confirmed that prior to this year, in the 3 years she's had it she hasn't needed to do any repair related stuff on it. 

[neilestrick]

5 minutes ago, cadenrank said:

And just talked with her, confirmed that prior to this year, in the 3 years she's had it she hasn't needed to do any repair related stuff on it. 

That's a good sign. Might want to replace the wiring harness. They can cause the relays to fail, and it's a cheap repair.

[cadenrank]

28 minutes ago, neilestrick said:

That's a good sign. Might want to replace the wiring harness. They can cause the relays to fail, and it's a cheap repair.

Would an aging wiring harness theoretically increase in resistance? Or is there a numerical way to test that value?  Visibly there were no signs of discoloration on the wires or at connectors and resistance through the element and TC terminal block and feeders was perfect to what I predicted (skutt doesn't provide the resistance data for this kiln like their other kilns for some reason. They spec at 4000w. So at 240v, am basing my estimate on the resistance of the whole element loop at 14.4) and measurement through the feeders and the whole element loop and the connection block was 14.4 on the dot. 

I brought that up to her though. I noted that if she replaces it and it fails again prematurely probably needs to look into what's causing it to fail prematurely. Nothing visibly or from the various tests appeared to indicate any other issues. 

So, you're thinking that 47v to ground when the relay was not closed could be coming from the failed mechanical relay? I knew 47v didn't make any sense to be there in that condition, but didn't seem like it would be causation to this issue

Edited August 7, 2022 by cadenrank

[Bill Kielb]

@cadenrank

16.5 vdc for control voltage is high especially for 12 vdc relays. Check your meter or check the power transformer is jumped for 240 not 208 v.  If it’s correct measure between ac1 & ac2 for 24 VAC and then between ac1 to the center tap = 12VAC  and ac2 to the center tap = 12VAC. 

All those values ought to be within ten percent. Careful they are AC values from the transformer.

The control board should change the ac from the transformer to 12 vdc, so there is a chance your meter could be off, or the input voltage to the board is high. 12v relays will heat and wear faster driven by 16.5 volts so let’s make sure that is right first.

To (for sure) test the mechanical relay which really only needs to have one bad leg in this configuration, remove the power from the relay, turn it on so it is closed (make sure 240v power (both legs) is disconnected and safe from the input of the relay)  and measure for continuity. Measure the relay input to output (across the relay) it should be zero ohms for each leg. If any leg measures higher than 0.1 ohm, it’s defective. Failure of either side of the relay or both will cause the kiln to simply not work as the elements are configured in series so without both phases, they just won’t work. To triple check, temporarily (and safely)  jump both sides of the safety relay respective phase inputs to their outputs and confirm the SSR fires the elements. Please  Always use appropriate caution around ALL live electricity. If you were to operate the machine for any length of time in this jumped configuration you would need to unplug the kiln before ever loading or unloading because of that SSR leakage issue and the potential to shock the operator.

The SSR will have some leakage so you likely will measure some voltage even when it is off. With a very high impedance meter this certainly can measure in the double digits. It sounds likely the mechanical relay will test as failed but the 16.5 vdc is really too high so figure that out regardless.

Since leakage on the SSR is hard to test, to test the SSR (when this is all working again), during operation measure the high voltage across it In the on cycle it should read zero or very near zero (record what your read) in the off cycle it should read line voltage. 

I have to say single SSR made possible by series elements, single zone. I think a bit disappointing for an initial impression for me. 

Edited August 7, 2022 by Bill Kielb

[cadenrank]

5 hours ago, Bill Kielb said:

@cadenrank

16.5 vdc for control voltage is high especially for 12 vdc relays. Check your meter or check the power transformer is jumped for 240 not 208 v.  If it’s correct measure between ac1 & ac2 for 24 VAC and then between ac1 to the center tap = 12VAC  and ac2 to the center tap = 12VAC. 

All those values ought to be within ten percent. Careful they are AC values from the transformer.

The control board should change the ac from the transformer to 12 vdc, so there is a chance your meter could be off, or the input voltage to the board is high. 12v relays will heat and wear faster driven by 16.5 volts so let’s make sure that is right first.

I will bring up this point with her.  The SSR's control side is labeled 3-34VDC, and I thought the specs for the Deltrol relay said up to 24VDC on the switching side, but the specs for that weren't exactly clear. 
 

5 hours ago, Bill Kielb said:

To (for sure) test the mechanical relay which really only needs to have one bad leg in this configuration, remove the power from the relay, turn it on so it is closed (make sure 240v power (both legs) is disconnected and safe from the input of the relay)  and measure for continuity. Measure the relay input to output (across the relay) it should be zero ohms for each leg. If any leg measures higher than 0.1 ohm, it’s defective. Failure of either side of the relay or both will cause the kiln to simply not work as the elements are configured in series so without both phases, they just won’t work. 

We sort of did a test as you're describing. I didn't record the numerical values of it though. With the relay closed from the controller, we checked for (audible) continuity between all variations of the input and output pins in case it was wired incorrectly somehow, and none of the variations we tried across the relay caused the meter to beep when the relay had audibly clicked on, and a program was running. I'm not sure what the meter's range is for when it provides the beep or not, but I can probably find it out. Testing the leads against each other provided the audible beep, but again, no combination of input to output pin caused the meter to beep. (meter's manual says: • Continuity Check: Audible signal <50Ω)

We know that both of the inputs to the mechanical relay have 240v when the SSR is closed. But only 10.1vAC at the output pins. 
And we know that when the SSR was open, there was 100v across the input pins on the mechanical relay, nothing on the outputs. 

5 hours ago, Bill Kielb said:

The SSR will have some leakage so you likely will measure some voltage even when it is off. With a very high impedance meter this certainly can measure in the double digits. It sounds likely the mechanical relay will test as failed but the 16.5 vdc is really too high so figure that out regardless.

Since leakage on the SSR is hard to test, to test the SSR (when this is all working again), during operation measure the high voltage across it In the on cycle it should read zero or very near zero (record what your read) in the off cycle it should read line voltage. 

I have to say single SSR made possible by series elements, single zone. I think a bit disappointing for an initial impression for me. 

We sort of did this test originally, I forgot that this SSR was only switching one leg, so took the initial measurement across the output pins with the relay closed and got 0 - 0.1 vAC.  For what that information may be worth. The mechanical relay was still in the circuit during that test, as well as the issue still present. 
It wasn't tested in the off cycle this way. Only tested the SSR in the off cycle between output and ground (output to ground when off was 47vAC, when closed was 120vAC) and input and ground. (Input to ground when it was off or on was 120vAC). 

I appreciate everyone's input! I've passed it along to her that the consensus seems to be with me that the mechanical relay is probably the fault, and also passed along all of the other information provided about possible causes. 

Edited August 7, 2022 by cadenrank

[Bill Kielb]

11 hours ago, cadenrank said:

It's the clear Deltrol relay as the 'safety' mechanical relay. It's a Deltrol 20850-81

It’s a 12 vdc relay, try and find out the cause of the 16.5 v reading. If the mechanical relay failed the continuity test and the meter tested good, the mechanical relay is bad.

16.5 volts if true will shorten the life of the mechanical relay, definitely check the transformer installed wasn’t errantly installed using the 208 v primaries.

 

 

Edited August 7, 2022 by Bill Kielb

[Bill Kielb]

58 minutes ago, cadenrank said:

t wasn't tested in the off cycle this way. Only tested the SSR in the off cycle between output and ground (output to ground when off was 47vAC, when closed was 120vAC) and input and ground. (Input to ground when it was off or on was 120vAC). 

Btw - very hard to do this without enough load to drain away the leakage, especially with a typical VOM. SSR’s have forward voltage leakage.

[cadenrank]

16 minutes ago, Bill Kielb said:

16.5 volts if true will shorten the life of the mechanical relay, definitely check the transformer installed wasn’t errantly installed using the 208 v primaries.

The transformer is a FD5-24. It says 250Vac on the front. 

So to understand, the measurements, between the two outer posts should be 24vAC, and from any of the outer posts to the center post should be 12vAC? 

If they weren't within that range of 10%, would that imply the transformer is bad? If they are within that range, but control voltage at the relays is still 16.5vDC, what would that imply? A controller issue? 

 

1 minute ago, Bill Kielb said:

Btw - very hard to do this without enough load to drain away the leakage, especially with a typical VOM. SSR’s have forward voltage leakage.

I figured that was the case, but wasn't sure if those values meant anything without a load/with it not working properly as it was. 

[Bill Kielb]

37 minutes ago, cadenrank said:

So to understand, the measurements, between the two outer posts should be 24vAC, and from any of the outer posts to the center post should be 12vAC? 

Yes, see below. It is multi voltage but 115v / 230v not 120/208/240 so unlikely it’s hooked wrong. 16.5 v is very high though. Only other thought I would have is there is possibly not a good chassis ground on the control board that turns this into regulated 12vdc. One of the retaining screws on the board ought to establish a positive ground. Very strange reading, ought to shorten the life of that relay. Or ….. bad 12vdc regulator on the control board, or measurement error of the meter.

 

37 minutes ago, cadenrank said:

I figured that was the case, but wasn't sure if those values meant anything without a load/with it not working properly as it was

It is so much the case, SSR’s publish their forward leakage. The lesson, never touch the output of an SSR because of the potential for shock.

 

Edited August 7, 2022 by Bill Kielb

[cadenrank]

47 minutes ago, Bill Kielb said:

It is so much the case, SSR’s publish their forward leakage. The lesson, never touch the output of an SSR because of the potential for shock.

 

Just to confirm on this point, does the 47v from output to ground when in the off-state seem to be something that would be acceptable or otherwise expected? (electrically speaking) or does the output to ground test not accurately depict the off state voltage? 
 

50 minutes ago, Bill Kielb said:

Yes, see below. It is multi voltage but 115v / 230v not 120/208/240 so unlikely it’s hooked wrong. 16.5 v is very high though. Only other thought I would have is there is possibly not a good chassis ground on the control board that turns this into regulated 12vdc. One of the retaining screws on the board ought to establish a positive ground. Very strange reading, ought to shorten the life of that relay. Or ….. bad 12vdc regulator on the control board, or measurement error of the meter.

We will check at the transformer, and then double check at the board again and see what the results are. 

[Bill Kielb]

1 minute ago, cadenrank said:

Just to confirm on this point, does the 47v from output to ground when in the off-state seem to be something that would be acceptable or otherwise expected? (electrically speaking) or does the output to ground test not accurately depict the off state voltage? 

You will ALWAYS measure some random voltage this way for this kiln in its present state,  it’s not accurate in any respect other than to say there is some leakage which we already know because the relay manufacture says it will.

[neilestrick]

I've measured the output voltage on kiln controllers be anywhere from 11V to 16V, and it has never been an issue. I certainly wouldn't expect it to be the cause of a relay failing in 8 firings, especially if it has been fine for 3 years. It's definitely worth seeing where the voltage is out of whack, though.

14 hours ago, cadenrank said:

Visibly there were no signs of discoloration on the wires or at connectors

Wiring can be bad even if it all looks good. I've replaced wiring harnesses on many Skutt kilns because relays were burning out prematurely. The Skutt control boxes run hot.

[cadenrank]

21 minutes ago, neilestrick said:

I've measured the output voltage on kiln controllers be anywhere from 11V to 16V, and it has never been an issue. I certainly wouldn't expect it to be the cause of a relay failing in 8 firings, especially if it has been fine for 3 years. It's definitely worth seeing where the voltage is out of whack, though.

I had told her that we should at least check the voltages at the transformer when she replaces the relay while she has the kiln apart. 
 

22 minutes ago, neilestrick said:

Wiring can be bad even if it all looks good. I've replaced wiring harnesses on many Skutt kilns because relays were burning out prematurely. The Skutt control boxes run hot.

The resistance of the feeders  (didn't test any of the small wires that distribute power in the control box though.) were all within expected limits as well if that means anything, but I mentioned it to her regardless. It's always nice to have a list so that if in a month or two (or any premature time of another premature relay failure) we have a direction to go. 

[Bill Kielb]

1 hour ago, neilestrick said:

I've measured the output voltage on kiln controllers be anywhere from 11V to 16V

That’s an interesting find. These circuits generally use the 78xx or 7812 voltage regulator. With that much variation it ought to be tough on the rest of the circuit design. Have you seen this often?

 

Edited August 7, 2022 by Bill Kielb

[neilestrick]

59 minutes ago, Bill Kielb said:

Have you seen this often?

No, but I don't measure it very often. Controller output is rarely ever the problem. Would it be affected by service voltage? I see 240 volts kilns running on services from 230 to 255.

[Bill Kielb]

2 hours ago, neilestrick said:

Would it be affected by service voltage? I see 240 volts kilns running on services from 230 to 255.

Generally no, after looking at the operating range of the 78xx it’s stabile plus 1.2 v from 14.8 v to 30v input  so I gave up on the transformer theory. Also after reading this kilns manual, it’s a Bartlett backbone  which I believe I have seen the 78xx series chip installed so I would be surprised if all the board voltages were not regulated pretty well. But, ya never know, learn something every day. 16.5 volts would definitely be unexpected and quite high and likely cause extra heating.

The concept is to minimize mechanical cycles and extend the life of the safety relay by turning it on and keeping it on through the firing. Unfortunately in this case it’s just gonna cook a little more than expected for the whole firing. It could shorten the planned long life of the safety relay. Hopefully it’s some measurement error plus the max possible output as it should be limited to 12.25v +1.2v or short of 14 v.

Just curious if you have just measured a bunch, never know.

[cadenrank]

In case anyone was curious of the outcome, she called Skutt today, which had her repeat some of the tests (including the vDC test on the mechanical relay's control side, meaning the Skutt tech also would have seen the 16.5vDC and didn't say anything relative to it) and conclusion was that the mechanical relay was defective, and they're sending a replacement. 

[Bill Kielb]

5 hours ago, cadenrank said:

Skutt tech also would have seen the 16.5vDC and didn't say anything relative to it

Hmm, interesting. I wonder if that means being over voltage by 25% is ok? Just kidding, I am sure it’s not a deal breaker. Your continuity proved the mechanical relay was bad. His silence on the voltage reading while interesting, doesn’t answer much for me except he only wanted to know if the relay was being activated by the control.

I am not sure the real answer, but I do know if 16.5 Volts is accurate it will heat the relay a bit more ……. In fact, approximately 25% more heating so that may be just fine with some folks.

Good job on figuring out the mechanical relay part.