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help! relays causing overfiring?

updated wed 26 jul 06

 

Steve Slatin on sat 22 jul 06


Emily -- Probably a dumb question, but can you/have you tried to reset the
temperature offset? My understanding of most of the computer controllers
is that as long as you are off by a consistent margin, it should be possible to
readjust the controller and get the desired result.

Another option, if it is consistently overfiring by, say, one cone, you might
try setting it to fire to a cone lower than the one you want. If you can see
the cones it a hot kiln (I can't) check them to see when the computer shows
you're close and if the results are 'on' then you have a simple work-around.

Best wishes -- Steve S

Emily DeFoor wrote:
Hello All,
I have 2 Olympics (which I regret greatly). Both with Bartlet
controllers. Both now overfiring by 1-2 cones. I have had the kilns for
a while with almost no problems (except the bad Thermocouple Olympic sold
with my kiln, apparently they have a quality control issue)...one for 3
years and one for 1.5 years. I have replaced the the Thermocouples with
new ones from Olympic and now new ones from Paragon. I even just put new
boards on both. Still overfiring. Could it be the relays sticking? The
kiln does shut off. It is my understanding that relays either work or
they don't. If they stick they are just stuck and the element stays on
until you flip the breaker. Is it possible that they could just be
delayed some how?...by too much heat?....If the TC and Board are new and
sending the proper signal to the relay but the relay is delayed in its
response, it would cause overfiring...but is this possible?
Thanks!
Emily


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Emily DeFoor on sat 22 jul 06


Hello All,
I have 2 Olympics (which I regret greatly). Both with Bartlet
controllers. Both now overfiring by 1-2 cones. I have had the kilns for
a while with almost no problems (except the bad Thermocouple Olympic sold
with my kiln, apparently they have a quality control issue)...one for 3
years and one for 1.5 years. I have replaced the the Thermocouples with
new ones from Olympic and now new ones from Paragon. I even just put new
boards on both. Still overfiring. Could it be the relays sticking? The
kiln does shut off. It is my understanding that relays either work or
they don't. If they stick they are just stuck and the element stays on
until you flip the breaker. Is it possible that they could just be
delayed some how?...by too much heat?....If the TC and Board are new and
sending the proper signal to the relay but the relay is delayed in its
response, it would cause overfiring...but is this possible?
Thanks!
Emily

William & Susan Schran User on sun 23 jul 06


On 7/22/06 11:38 PM, "Steve Slatin" wrote:

> I have 2 Olympics (which I regret greatly). Both with Bartlet
> controllers. Both now overfiring by 1-2 cones.
>...Still overfiring. Could it be the relays sticking?

I'm assuming you've set your controller to a published end temperature that
is supposed to match the cone.

If your kiln fires faster or slower than the rise of temperature per hour
for that cone to melt at the specific temperature, then the cone will melt
at a higher or lower temperature. This is especially true for the last hour
or two of the firing.

If you want your end temperature to match a specific cone, then you're goin=
g
to have to watch closely towards the end of the firing to see when the
firing cone goes over to mark the temperature reading.

When I'm firing a very fast crystalline glaze firing - 4 hours to ^6 - ^6
goes over at 2150=B0F.


-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu

Ron Roy on sun 23 jul 06


Hi Emily,

Every thermocouple reads differently - and many times they are way off -
every time you install a new one you will have to adjust your end
temperature.

I take it you are not firing with cones - you should always be able to
check your firings by looking at cones during the firing.

Certainly - never trust the info a pyrometer is sending to a controller -
especially if it's new.

I have never used the "S" type thermocouples - I am under the impression
they are better - you would need to find out if your controller will work
with them and make the adjustment.

RR

>Hello All,
>I have 2 Olympics (which I regret greatly). Both with Bartlet
>controllers. Both now overfiring by 1-2 cones. I have had the kilns for
>a while with almost no problems (except the bad Thermocouple Olympic sold
>with my kiln, apparently they have a quality control issue)...one for 3
>years and one for 1.5 years. I have replaced the the Thermocouples with
>new ones from Olympic and now new ones from Paragon. I even just put new
>boards on both. Still overfiring. Could it be the relays sticking? The
>kiln does shut off. It is my understanding that relays either work or
>they don't. If they stick they are just stuck and the element stays on
>until you flip the breaker. Is it possible that they could just be
>delayed some how?...by too much heat?....If the TC and Board are new and
>sending the proper signal to the relay but the relay is delayed in its
>response, it would cause overfiring...but is this possible?
>Thanks!
>Emily

Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0

Ivor and Olive Lewis on mon 24 jul 06


Dear Ron Roy,

You say...<are way off - every time you install a new one you will have to adjust =
your end temperature.>>....

I presume you mean this in the sense that if you located half a dozen =
pyrometers at six different locations in a kiln each would give an =
individual reading and no two would give the same reading.

People often forget that a pyrometer thermocouple has two sensitive =
ends, a Hot Junction and a Cold Junction. The Cold Junction has to be =
held at a specific temperature for the reading from the Hot Junction to =
be true. Remember this is an analogue device, one where the microvoltage =
or EMF is translated into a temperature. From memory, the Cold Junction =
reference temperature should be held at the temperature of melting ice. =
If this is not done then a correction should be applied to all readings =
so that ambient temperature is subtracted from the recorded temperature.

The "S" grade Thermocouple is Platinum+10% Rhodium V Platinum and covers =
the range -50 deg C to 1786 deg C. Ref. junction at 0 deg C.

Best regards,

Ivor Lewis.
Redhill,
South Australia.

dwichman@frontiernet.net on mon 24 jul 06


Hi Emily,

I recently had the same problem you did. After replacing
thermocouples and new elements in the kiln(mine is an L & L with a
controller), I ran my glaze firing and the kiln fired to over cone 6
even though my program was to cone 5. I communicated several times
with Rob Battey, tech support for L & L kilns. He was incredibly
helpful and nice to explain readouts I could get from the controller.
To make a long story short, the controller had input from two
thermocouples and had to reconcile the degrees to my desired 5 cone.
Because I was ramping up fairly quickly, there was a 20 to 40 degree
difference in the two kiln sections which was causing the controller to
keep the kiln on the up ramp. When I slowed down the firing - 300 per
hour to 1900 and then 90 per hour till cone 5 - the kiln had a longer
time to heat evenly which resulted in the controller doing a better
job. I am once again happy with my kiln and feeling in control - it is
miserable trying to control the kiln without understanding it.

Rob explained how I could get what each thermocouple was reading, and
gave me tips on firing and stacking the kiln to get a more even firing.
Using cones to verify the heatwork, after a couple firings you can
figure out which temp you need to fire to. You can either program to
fire to this temperature or program thermocouple offsets and then fire
to the normal degrees for that cone. I don't know if all controllers
are pretty much alike, but there was also a way to end the current
segment and go right into the soak if the cones showed it was time.
This was helpful in the couple firings while I was still figuring out
what temp to fire to. I read somewhere that thermocouples need an
offset of about 50 degrees and that the first ones you get in a kiln
are already offset and so you are not aware of this. I have to fire
about 40 degrees less than the thermocouples read to get what I want.

Hope this helps.

Debi

Arnold Howard on tue 25 jul 06


From: "Emily DeFoor"
> I have 2 Olympics (which I regret greatly). Both with
> Bartlet
> controllers. Both now overfiring by 1-2 cones. I have
> had the kilns for
> a while with almost no problems (except the bad
> Thermocouple Olympic sold
> with my kiln, apparently they have a quality control
> issue)...one for 3
> years and one for 1.5 years. I have replaced the the
> Thermocouples with
> new ones from Olympic and now new ones from Paragon. I
> even just put new
> boards on both. Still overfiring. Could it be the relays
> sticking?

This does not sound like a relay problem.

Are the thermocouples grounded to the stainless steel case?

Is the amount that the kiln overfires consistent, or does it
vary from one firing to the next?

Are you using the correct type of thermocouple wire? (Type-K
and Type-S thermocouples require different wire.)

How far do the thermocouples extend into the firing chamber?

Sincerely,

Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com