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Kiln taking a long time to reach temp with new elements


Osso
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Hi all, 

I have an amaco select fire (same as skutt 818). I recently replaced the elements AND the relays (both gave out at the same time).

I did a cone 05 bisque yesterday at medium speed. It hit temp (1888) in 7.5 hours. 

Today, I am doing a bique 05 again medium speed and after 9 hours it's still not up to temp. What could be the issue? Normally I hear the elements buzzing on and off but I don't right now and while the kiln is gaining temp it's going sloooooow. It was perfect yesterday! New elements, new relays, none of the connections are loose. Help!

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If anyone was wondering I waited for it to cool down and then looked inside. One of the (new) relays melted. 

Luckily it was bisque that was in there not glaze work. Very frustrated though because I am sure I wired correctly. This relay melted on the second firing with it. 

Screenshot_20210913-101553.jpg

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9 minutes ago, Osso said:

If anyone was wondering I waited for it to cool down and then looked inside. One of the (new) relays melted. 

Luckily it was bisque that was in there not glaze work. Very frustrated though because I am sure I wired correctly. This relay melted on the second firing with it. 

 

I would check your wiring again just to be sure. If you didn't take pix when you took things apart, I would refer to the wiring diagram for your specific  kiln...

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22 minutes ago, JohnnyK said:

I would check your wiring again just to be sure. If you didn't take pix when you took things apart, I would refer to the wiring diagram for your specific  kiln...

I do one in one out wiring. As in, i take it off of one of the relays and put it on the same spot on the new one. But it does fit with the wiring diagram. 

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16 minutes ago, Osso said:

I do one in one out wiring. As in, i take it off of one of the relays and put it on the same spot on the new one. But it does fit with the wiring diagram.

I suggest Double check your element resistance, the relay rating, relay wiring diagram as  it could be a defective  one but it really is hard  and very unusual to melt one that way. Reminds me of double pole relays I saw earlier this year that were the wrong form.

That relay ended up as form Z but looked identical to form C

https://community.ceramicartsdaily.org/topic/25213-duncan-kiln-not-reaching-temperature/?do=findComment&comment=203748

 

Edited by Bill Kielb
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If it helps anyone understand things:

The new relay 20850-81 is described in https://deltrol-controls.com/sites/default/files/pdf/data-sheet/270-275 Series Data Sheet.pdf
under Model 25F Coil 24VDC on p4 (DPST-NO of I've read it right)

The only reference I could find to the new old relay 23640-70 was in the "View all part numbers" list at
https://deltrol-controls.com/products/relays/power-relays/275
Maybe Detrol could clarify the picture, or confirm the identify of a plug-in replacement?
 

Edited by PeterH
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28 minutes ago, PeterH said:

The new relay 20850-81 is described in https://deltrol-controls.com/sites/default/files/pdf/data-sheet/270-275 Series Data Sheet.pdf
under Model 25F Coil 24VDC on p4 (DPST-NO of I've read it right)

Look again. It's a 12 volt coil, like it shows on the relay itself. It's the correct relay for the kiln, the same one I use in all older Skutt and Amaco kilns.

FYI, how to tell if your Skutt or Amaco SF kiln should have the clear ic cube relays above or the black rectangular ones is by the depth of the control box, which can be measured by the number of louvers in the top of the control box. The older kilns have a shallower box and have 5 louvers, the newer kilns are deeper and have 6 louvers. There was a period where they were switching from the ice cube relays to the black relays and they put in an adapter plate to hold the longer black relays at an angle, and the wiring harness used right angle connectors because the box was too shallow for straight connectors since the connections are at the top of the black relays, not at the end like the clear ones. At some point they made the box deeper to accommodate the straight connectors and because they found the box was running too hot for the black relays and they were burning out too quickly. If you have the black relays with right angle connectors in your control box, they recommend replacing them with the clear relays because the clear ones last longer in the shallower box.

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2 hours ago, Osso said:

New one (melted) on left, old one (stuck) on right. 

Same relay, so that is good, right form. The  actual moveable contact on the new one has overheated without a sign of the terminal overheating which means either it was defective from the factory and misaligned or lots of load went through it. I would double check the wiring and element resistance as wired to be sure that 25 A or more continuous wasn’t going through it. If not, then it likely came misaligned and overheated during firing. IME it’s rare to see them melted without the melting occurring right at the connection first. The moveable contact on this one looks annealed. Definitely worth thorough check IMO before dropping a new one in.

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2 hours ago, Bill Kielb said:

Same relay, so that is good, right form. The  actual moveable contact on the new one has overheated without a sign of the terminal overheating which means either it was defective from the factory and misaligned or lots of load went through it. I would double check the wiring and element resistance as wired to be sure that 25 A or more continuous wasn’t going through it. If not, then it likely came misaligned and overheated during firing. IME it’s rare to see them melted without the melting occurring right at the connection first. The moveable contact on this one looks annealed. Definitely worth thorough check IMO before dropping a new one in.

How do I rest the resistance? This is the only part of kiln repair I haven't done/am not familiar with 

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