Kilns and Furnaces FL80 firing issue

[MartinC]

I have a Kilns & Furnaces FL80 with a firing issue that is periodic. The problem is that sometimes the kiln will not heat. It either won't start or, at high temp (typically when I get to a hold at 1146 going up), it stops heating. Rather than hearing the loud clunk of the contactor, I hear a quiet click suggesting that something is going on. If the kiln cools a bit ( a few hundred degrees and a while later), I can start it again.

The elements are quite new and I changed the contractor so that is not the problem. I would appreciate guidance as to what the problem might be and where to look to resolve.

Thanks

[neilestrick]

So normally there's a loud clunk throughout the firing as the contactor cycles on and off? But when it's not working you only hear a soft click?

Without a wiring diagram it's hard to say, but it sounds like a sticky relay, as they often stick when they get hot (from a combination of the current flow and the heat of the kiln), but then they'll work again as they cool. Is the contactor switched directly by the controller, or is there a smaller pilot relay that works between the controller and contactor? A small pilot relay would account for the quieter click. Of course, that wold mean that the big contactor is failing periodically, despite you changing it.

Any chance you can post a wiring diagram? The manufacturer's website was no help.

I did fine this little gem on their venting page: "The kiln itself will not produce any fumes. Most material used in hobby ceramics are safe and produce minimal fumes. Certain materials like lustres and ceramic transfers can produce more harmful fumes when fired in quantity, but are rarely used in school/hobby kilns." Lots of issues with that statement. Apparently they have only ever fired their kilns empty!

[MartinC]

Thanks for your response and your first sentence is correct

I have also never found a wiring diagram. I'm going to open it up again tomorrow and get into the nuts and bolts. I'll follow the wires and look for a pilot relay. However, I don't understand why a new contacter would fail within a week with the same issue unless there was a common underlying problem. Perhaps the sticky relay issue permits it to cycle on and off  but the connection to the contactor is dodgy?

[neilestrick]

12 minutes ago, MartinC said:

Thanks for your response and your first sentence is correct

I have also never found a wiring diagram. I'm going to open it up again tomorrow and get into the nuts and bolts. I'll follow the wires and look for a pilot relay. However, I don't understand why a new contacter would fail within a week with the same issue unless there was a common underlying problem. Perhaps the sticky relay issue permits it to cycle on and off  but the connection to the contactor is dodgy?

Pilot relays are typically only used in kilns with large contactors, like 50 amps or more, where the controller doesn't have enough output to switch something that large. Can you post the info on the serial plate- volts, amps, etc?

I have seen brand new relays/contactors fail right away. If it's not due to the contactor itself being faulty, then you want to replace the power wires that connect to it, as they may be overheating and causing the failure. In my experience it's almost never the control wires.

[MartinC]

Image attached. Could the wires from my elements be getting too hot? I can stuff the gaps with kiln blanket

[MartinC]

This is the contactor I'm using, if it helps

https://new.abb.com/products/1SBL137001R1310/af09-30-10-13

[neilestrick]

Can you post a pic or two of the open control panel so we can see what's in there? Most of us on here have probably never seen that brand of kiln.

[MartinC]

Will do, it's late evening here in the UK so am going to open up the kiln tomorrow. Thanks for your help again. Much appreciated

[neilestrick]

1 hour ago, MartinC said:

This is the contactor I'm using, if it helps

https://new.abb.com/products/1SBL137001R1310/af09-30-10-13

How many of these are in the kiln?

[Bill Kielb]

2 hours ago, MartinC said:

This is the contactor I'm using, if it helps

https://new.abb.com/products/1SBL137001R1310/af09-30-10-13

Looks like this is rated at  25 amps max and your load is 26 amps and each is rated at 9 amps @ 240 v.. This is also a three phase contactor with an end switch. You service should be single phase 240v, 1 hot wire and one neutral. Not sure this is the right relay for several reasons. Even though resistive circuits start without tremendous inrush, they do generate a lot of heating in the circuit though. It’s regular practice in North America to supply them with wiring and switching that is rated 125% though to minimize the effect of the heating on the switching device such as a circuit breaker. As a control relay, these contacts should be rated well beyond the maximum load for longevity.

Since you have single phase 240v (not split phase like in North America) you really only need to switch the hot phase. Picture of how the elements hook to this would help, and the auxiliary contact is rated much less so depending how it’s used, could be an issue as well.

 

Edited February 10, 2023 by Bill Kielb

[High Bridge Pottery]

I thought it was always good practice to switch the neutral too? Even though it is meant to be at 0v or ground that may not always be the case. I couldn't understand the specs on that if it was 25A per terminal or 25A overall but it seems like you say it's 9A per terminal. I wouldn't be surprised that they are on a knifes edge with the rating and how much the kiln draws.

 

If you ring Kilns and Furnaces they should provide you with a wiring diagram.

[Bill Kielb]

2 hours ago, High Bridge Pottery said:

 

I thought it was always good practice to switch the neutral too? Even though it is meant to be at 0v or ground that may not always be the case.

 

IMO, switching the neutral provides for the possibility of a higher resistance connection, something beyond zero volts. Most things are surrounded or in proximity to a ground plane of sorts so switching to me adds more risk. The specs are confusing to me, but why he has a three pole relay with an end switch is a bit of a mystery. If he has more than one set of elements, then that relay may be applicable. My assumption is those contacts don’t exceed 25 amps total load though.  A few pictures of the wiring to the relay with context included for the connections would likely solve the mystery.

[High Bridge Pottery]

It is a front loader and the ones I have seen are split into a separate circuit for each side wall and one for the floor so I assume each pole is switching one of those circuits. 

[MartinC]

Power and controller in

[MartinC]

Power is split to three wires

[MartinC]

Off to the door relay

[MartinC]

Then into the contactor

[MartinC]

Then off to the elements on the right

[MartinC]

And the other right!

[MartinC]

So, if I understand, the solution to the mystery is that the power in is split into three wires in for the door relay. Then three wires out to the contactor. Three wires necessary for wiring the separate elements. The contactor contains a single coil which should take the load. The only other "moving" part is the door relay. The door relay is as old as the kiln and so might be failing at high temp because of the load. Unfortunately, the door relay switch is, I've discovered, discontinued.  

I guess the way forward is to test the circuit when it is hot and failed but I do not think I am qualified to do that (at least not without risking serious injury)

[High Bridge Pottery]

Is this red wire actually connected to anything? Hard to tell from the photo but it doesn't seem to be going to any of the barrel terminals.  The white colour on the top red wire (L1)  seems to hint it is getting very hot.

Edited February 11, 2023 by High Bridge Pottery

[MartinC]

Close up. Yes, it's wired in. On the original photo you are seeing the stripped with and the plastic tie

[Bill Kielb]

Hmm, my best guess here. It looks like element loads are split among the three contacts so prox 8.6 amps each. Depending on the rating which seems based on switching  and derated at ambient operating temperature (60c), these contacts might be rated only at 9amps (switching  prox. 300-600 times per hour) So the simple question would be if these  contacts degrade rapidly, this relay is underrated and causing issues. The inrush from elements should be mild as compared with an ordinary tungsten lamp which is often briefly in excess of 8X, so this could work even at 60c - which is not that hot but seems underrated in and around kilns.

It should be easy to inspect, if worn or burned with little use, you need a better rated relay, without the auxiliary contacts. Not sure why they are here anyway.

If the other relay in the picture is the pilot for this, it could be damaged and likely will suffer a significant inrush to fire this relay. So simple to check relay contacts and understand what has failed or which contacts have burned excessively and replace as necessary.

These are enclosed so not necessarily free air. 60c is not hot for kiln service, my thought is this is likely under rated. The pilot relay however will experience a reasonable amount of wear as well, even though only switching this contactor. It won’t last forever. Definitely check both for contact wear, obvious material transfer etc….

You should measure virtually zero resistance across any of the relay contacts when closed or if live definitely less than a 0.1 volt across them. Live stuff is live though and carries the danger of electrocution. Maybe a local kiln tech?

Edited February 11, 2023 by Bill Kielb

[MartinC]

Okay, I take the wires out and check all the contacts. Easy enough. I'll look for burn damage etc

 

[High Bridge Pottery]

Doesn't look like the nicest connection but at least it is connected 

 

Has it got 12 elements? 6 a side? I tried to figure out how it's wired and this is what I came up with (could be wrong)