Low voltage issue

[Didiho]

Hello all,

I have a km 714 kiln from Skutt and recently it has been showing E1 as it rises temperature till around 1180c. Known from 'DIAG' and actual measuring the elements, I found that the voltage is lower that 220/240V. I would if it is the reason of E1 and what should I do for repairing the kiln. Thank you all.

 

 

[neilestrick]

What is the actual voltage of your electrical service? How old are the elements? Have you measured the element resistance? What is DIAG?

[Didiho]

@neilestrick

 

Hello Neil,

the actual voltage of km714 is 208V/240V. The elements are around 1 year old. The DIAG shows it's 217V when with no load and 207V when with full load. I'm not sure how can I check the element resistance. 

 

Didi

[PeterH]

On 7/4/2022 at 4:10 AM, neilestrick said:

What is DIAG?

Minor insight in PS, the rest is just cut & paste of potentially relevant facts.

Looks  like DIAG is used to indicate the kiln's diagnostic tests, which include VOLT.

https://skutt.com/skutt-resources/troubleshooting/diagnostic-tests/

Specification sheet https://skutt.com/pdf/service_manual/km_kiln_specs.pdf

... which seems  a little economical with the truth. 
- Will fire with 240V or 208V power.
- should never be fired on a 240V supply without first installing a full set of 240V elements.

Wiring diagram (without element resistances) https://skutt.com/images/KMT714-W_8510.pdf

BTW the element resistances for  240v & 208v might be the same!

 

PS It might be interesting to use the AMPS feature  in the dIAG (if fitted)?
Am I right in thinking that the current resistances of the elements are given by VOLT/AMPS(1), VOLT/AMPS(2) & VOLT/AMPS(3)?

http://www.skutt.com/pdf/service_manual/11_4.pdf

Edited July 5, 2022 by PeterH
Added PS

[PeterH]

Confused thread about the two versions of the kiln

Although Mop (a UK resident) seems to be talking about 13 & 16 amp 230v versions, rather than the 208 & 240v US versions.
Anyway, the UK versions have max cones of 8 & 10, which will effect the element lives when firing high. What cone do you glaze-fire at?

The US versions (which both have the same element resistances but different voltage feeds) look like they have similar differences in  power -- and presumably max cone rating.

PS Slightly surprised to see the UK classified as 230v rather than 240v, but I was forgetting about the great non-standardisation.

The voltage used throughout Europe (including the UK) has been harmonised since January 2003 at a nominal 230v 50 Hz (formerly 240V in UK, 220V in the rest of Europe) but this does not mean there has been a real change in the supply.

Edited July 5, 2022 by PeterH

[Dick White]

9 hours ago, Didiho said:

@neilestrick

 

Hello Neil,

the actual voltage of km714 is 208V/240V. The elements are around 1 year old. The DIAG shows it's 217V when with no load and 207V when with full load. I'm not sure how can I check the element resistance. 

 

Didi

According to Wikipedia, the standard mains voltage in Taiwan is 110V, or 220V when measured across both poles of the split-phase service. The US version of the Skutt 714 is designed for 120V mains. Something to note about the design of the 714 is that it is actually two stacked but electrically separate 120V kilns. It requires a 4-wire (two 120V hots, a shared neutral, and ground) NEMA 14-30 plug.  One 120V side of the line powers the top element and the other 120V side powers the middle and bottom elements (which are wired in parallel). It is designated as either 120/208V because, in the US, 208V service in commercial locations is also 120V from either line to neutral/ground. So what does this mean for Didiho? In the best of circumstances, the kiln when used in Taiwan will have about 10% less heating power than in the US simply because the standard mains voltage is 110V vs 120V. If the Diag function (which measures across both lines without regard to the neutral) is getting only 217V with no load and 207V under load, that suggests the power supply from the utility is lagging or the household usage is overloading its capacity. This yields a performance loss of at least 20% from the nominal US design.  Further, as the elements wear through usage, the heating power will decrease, until at some point it simple can't finish the job and the dreaded E-1 error appears. You can't fix the utility supply problem, but you can check whether the elements are worn past their prime. The three elements for the 714 are all the same, with resistance specified as 11.4 ohms. You can use a digital multimeter to test the resistance of each element. If the resistance measures more than 12.5 ohms, the element is worn out and should be replaced.

[PeterH]

17 hours ago, Dick White said:

The three elements for the 714 are all the same, with resistance specified as 11.4 ohms.

That  doesn't seem consistent with the figures in http://www.skutt.com/pdf/service_manual/11_4.pdf

OTOH the wiring diagram https://skutt.com/images/KMT714-W_8510.pdf  shows one element across the  L1/N split and two elements in parallel across the L2/N split. If the socket is fed from a split-phase supply these voltages are 120V (if the socket is fed from a 3-phase supply they are 108V).

If all three elements are 11.7 ohms this gives power consumptions of 3,692W & 2,990W (close to the published figures of 3,600W & 3,000W). I can find no combination of 11.4 & 5.7 ohm elements which gives comparable power consumptions.

 

Edited July 6, 2022 by PeterH

[neilestrick]

On 7/5/2022 at 2:14 AM, Didiho said:

The elements are around 1 year old.

How may firings have you done with the current set of elements?

[Dick White]

5 hours ago, PeterH said:

That  doesn't seem consistent with the figures in http://www.skutt.com/pdf/service_manual/11_4.pdf

The elements of the US version are all the same, 11.4 ohms. However, because the middle and bottom elements are wired in parallel, for a service person taking a resistance reading across either of these two with everything in situ will include the other, yielding a reading of half, or 5.7 ohms.