3 phase kiln questions?

[HappyHippyDad]

A customer has asked me to install a supply for a Wenger Webcot kiln.

The faceplate is very worn and I cannot see the kW. They state the kiln it type 3670w and is rated at 12kW.

The paperwork does have 3670w on it but when I look at the spec sheet (see picture 2, SpecSheet) ) there is no sign of a kiln which is 12kW. This model has 12 elements therefore it must be one of the last 6 models on the spec sheet, but again no sign of 3670w. It looks like there is one called 3060w though but this is not 12kW. Does anyone have any ideas how I could find the kW, or does anyone recognise the kiln details and know the kW?

The wiring diagram (see picture 4) shows that it can be wired as single phase or 3 phase. This will be wired as single phase. My questions...

1. Do I just join the 3 phases together as per the diagram?
2. Do I need to increase cable size compared to the existing flex on the Kiln as I am joining 3 x 10mm cables into one conductor? Although the neutral carries the same current and there is only 1 neutral conductor! Why is this?
3. On the spec sheet (pic 2) it has 2 columns for electricity supply required. One for single phase and one for 3 phase. The last 4 columns for single phase have a dot. looking below it says treat as nominal rating 14kW for single phase, yet the actual column labelled nominal electrical .loading states different, higher values, why is this?

Pictures below show the almost unreadable faceplate, spec sheet, cable and part of the wiring diagram.

Picture 1, faceplate.


Picture 2, Spec sheet.


Picture 3, Cable


Picture 4

 

[HappyHippyDad]

Maybe give these people a call?

Wenger webcot | Kilncare | Made in Britain

We are the true Wnger Webcot kiln specialist with details and specification from everything from replacement elements to switch gear and controllers.

www.kilncare.co.uk

"We have details, knowledge and specifications for just about every kiln made by Webcot and later, Wenger before Wenger kilns ceased in late 1982. We are truly Wenger Webcot specialists in every manner."

Just emailed them?

 

[pc1966]

Did you read his last post, he is asking how to measure resistance of the elements and you have instructed him to do a live test for this???? ... unless he wants to blow his meter up this is not a good idea, be clear what you mean especially when live testing please.

No, I meant the oven controls switched on otherwise he will see infinite resistance at the terminals or cable!

Perhaps I should have been a bit more verbose/explicit about that.

 

[Avo Mk8]

One sold on ebay three years ago, and the seller listed technical details, which appear to confirm it is 12kW.
In which case on single phase with the existing cable, and all L conductors connected together, just over 16A down each L. Whereas the N conductor didn't have much, if any, current down it when it was 3 phase, it'll have about 50A on single phase, so you will need to upgrade at least that!
I guess safest to assume 14kW as the total worst case load, so a 60A single phase supply and a cable to match.

Wenger Webcot 3670W Electric Front Load Kiln for Ceramics/Pottery or Glass​

SOLD - 15 Mar 2018, 21:36 £450.00 Buy It Now or Best Offer, eBay Money Back Guarantee

Seller: catspudkin (140) 100%, Location: Totnes, Ships to: Free Local Pickup, Item: 173185872805Wenger Webcot 3670W Electric Front Load Kiln for Ceramics/Pottery or Glass. This kiln is designed for pottery but has been used successfully for glass fusing. The front door can be removed easily to aid transportation/lifting. The kiln was last used 5 years ago and was in good working order. Potential buyers are welcome to arrange to come and look before bidding. External measurements: Height 125cm Width 83cm (including keylock box) Depth 98cm Internal measurements: Height 75cm Width 45cm Depth 50cm 12 kw Three Phase Maximum temp 1300 centigrade Stafford ST301 controller and cabling included

 

[HappyHippyDad]

Super! I shall measure between the ends of the elements with them disconnected. Would @pc1966 's solution also work (not live of course)?

Could we do an example calculation please?

Lets say the kiln is 12kW. What should the end to end resistance be of each element if wired as single phase?

My maths would give :

230/12000 = 0.0192ohms but is this then multiplied by 12 because of the amount of elements?

I don't think this is correct as if I just changed it for 3 phase I would get 400/12000 which would give a different resistance reading.

What calculation do you do with the resistance reading of 1 x element once you have it?

 

[Darkwood]

I'm guessing PC just meant to have the on button on, not actually live.

Possible but at best his post is ambiguous and at worst it is dangerous advice given the previous posts.. we mustn't assume you or others would read the post correctly hence I asked for more clarity.

If however he did mean as you express then it will not likely work like that, heating processes of this size will most likely be contactor controlled or even solid state relay via a temp' controller so switchin the kiln on with no power will not link you to the elements and most likely will give you readings of the control equipment, if he meant testing at the elements themselves then it begs the question of why anything needs to be in a on position, until we get a response back I am a tad confused and think the advice is not relating to recent posts but earlier ones.



EDIT @pc1966 you replied while I was typing, ok fair response but you can see why it is a little ambiguous, but as above you will see infinite resistance anyway unless you are testing from the output of the contactors or direct onto the elements, with no power you have no power circuit pulled in for the elements.

 

[Darkwood]

We need to see the wiring config of the elements, you have the wiring plan there so we can then use ohms law to establish the demand of the elements per phase.

 

[pc1966]

True, it might have a contactor, but they stopped making these in the early 80s I think so SSR very unlikely. At around 18A/element it might even be a basic bimetallic operated switch as for domestic cookers, but the schematic should reveal this.

 

[Darkwood]

@pc1966 Domestic cooker loads are suitably small enough to work off simmerstats, this is an industrial kiln and I have yet to see one that works off such rudimentary control methods, I would favour contactors here simply because of the current been switched, also the fact it is changeable between single and 3 phase would mean some kind of 3 phase switching mechanism, normally the stat's however they are configured be it load passing or control circuit operation don't do 3 phase switching although I will stand corrected as there are certainly machines etc out there that have bespoke items in them purposely designed for them.. however, this is a very expensive solution to use if we have off the shelf alternative methods like contactor control and such alternative bespoke solutions are only really used to save space for more compact design, a issue I doubt needs to be applied to a kiln.
I will add here that some modern domestic ovens do indeed give both 1 an 3 phase options yet do not house contactors, this is where bespoke comes in and given the much lower loadings in domestic ovens it may be the case they use a 3ph simmer stat.

 

[HappyHippyDad]

I do have the complete wiring diagram, but it is a mismatch of many pictures, which would be just be chaotic to look at. I've just texted the customer for one full picture.

 

[westward10]

See all that ohms law stuff at college wasn't a waste of time???

 

[HappyHippyDad]

We need to see the wiring config of the elements, you have the wiring plan there so we can then use ohms law to establish the demand of the elements per phase.

The best I can do!

 

[westward10]

You have four elements per phase. What you need to do is access that contactor.

 

[pc1966]

Yes, it is contactor controlled just as @darkwood said.

Elements seem to be 3 identical sets of 4 in series, star-connected. If you can access the contactor out-going terminals you should easily manage to measure the resistance of each set and they ought to be very similar.

 

[westward10]

According to that schematic the elements are all the same so if it easier to access the elements you only need the resistance of one.

 

[Darkwood]

Measure any element 2 elements to confirm duplicate readings (wires disconnected) and not a faulty element you picked by chance, take this common value and we can tell you the rating with ohms law, taking measurements further upstream may not give accurate reading if any of the elements are failing and or loose connections so only do that if access restricted from getting to the elements.
If you need to take reading further upstream then get the ohms readings between every phase to phase option and they all should match give or take a few ohms, if they do we can rely on that value with confidence.

PS you can ignore the N in testing.