Need your opinion on 1-phase electric kiln

[VladCruceanu]

I am looking to buy my first electric kiln and I need to know from your experience if 1-phase kilns are good.   

This is the kiln: Nabertherm Top 60 Eco - https://www.scarva.com/en/Nabertherm-Top-60-Eco-Pottery-Kiln/k-4947.aspx

The same kiln with the exact same exterior and interior dimensions can be bought also for 3-phase with more loaded KW (1-phase is 3.6 KW and the 3-phase is 5.5 KW).  How is this difference affecting the firing and the objects?

Thank you.

 

[Chilly]

Vlad, in the UK, 3 phase electricity is usually supplied to factories and industrial type premises.  Houses only get 1 phase. 

So, when I bought my kiln for use at home I needed 1 phase.  And the kiln at the community centre is 3 phase, as that is a commercial property.

I don't think the firing will be any different.

 

 

 

 

[Bill Kielb]

What we know for sure is 3.6 KW is about 65% of 5.5KW. So the single phase product has much less output which could mean longer firings or it may not be rated to the same top cone temperature. It is odd that the wattage of each is not similar, generally kiln manufactures keep wattage near the same for each option. I started to search their site but it was far too annoying as mostly materials would show up regardless of the kiln drop down chosen. 

[VladCruceanu]

Both 1-phase and 3-phase kiln has the same top temperature and the exact same dimensions. 

Probably the 1-phase will heat up more slowly? Are there any disavantages if I go for the 1-phase? I am asking because I have heard rumors but not from ceramists. 

My home permits the 3-phase as the house has the connection but from the ground floor to the 2nd floor, is very hard for an electrician to get the cables for a 3-phase kiln without making holes everywhere. The 3-phase cables will not have room in the existing pipes that are in the walls, made for actual cables.

[Mark C.]

If you have three phase and you intend not to move(moving to single phase location will be a expensive issue later)Then use 3 phase . I'm assuming you want the 3 phase upstairs (you did not make that clear) if your kiln is located with single phase buy a single phase kiln.

I have use single phase kilns at home for 45 years now with zero issues as I do not have 3 phase at home.

Buy the kiln soles on what phase you have at site and in the future, Single phase kilns have more resale as most use only single phase at home.

[neilestrick]

There are several kilns in the US that have different KW ratings for single and 3 phase kilns. For example, in the US, kiln manufacturers all make a line of kilns that are meant to be plug and play. That is, they do not have to be hard wired. The vast majority of kilns sold in the US are of these models. In order to be used with a plug, they have to keep the amperage draw of the kiln at 48 amps or less. With 3 phase service you can get a higher kW rating while keeping the amps well below 48. This doesn't really affect most models, but with the 10 cubic foot kilns they are underpowered on single phase service, especially at 208 volts. So there may be something going on with the Nabertherm kilns similar to that, with plug sizes and such.

At 3.6 KW that kiln is probably underpowered. I would talk to the seller and see if they know anything about why they're different.

[Bill Kielb]

OK finally have time to get to this.  A sixty liter kiln is about 2 Cu Ft and comparing it with something similar in the US  3.6 KW is probably fine. The link for the website Scarva is a bust for me but having looked up this actual Kiln on the Nabertherm site it appears solid. This is a very small kiln and combined with the extra thermal insulation likely makes 3.6 KW adequate.  The actual kiln specifications have a subscript note 1 that if you are using three phase only two of the phases will be used. If my memory is correct your single phase voltage is 240 V (Phase to Phase)and three phase approximately 400 V (Phase to Phase).

So my opinion now is:

• Single phase is fine especially for this size kiln
• I believe the manufacture designed this for 3.6 KW
• The additional KW is due to the same elements being used at 400V,  hence the wattage increases.  I would expect this  and further expect that the designers accounted for the additional voltage through element design and duty cycle.  They really have a single phase model that can be used at a higher voltage.  In the UK this makes sense to me!

A closing note: in the US we work in BTU so 1000 Watts thermally to us is 1000W X 3.41 Btu/W = 3410 Btu, where you may work in Watts or Joules per second. Either way regardless of units it is all linear meaning 10% more watts is 10% more heat.

And the last maybe useful or useless thing to know is Watts in single phase are calculated as: Voltage X Current = Watts and in three phase: Voltage (L-L) X Current X 1.73 (Sqr. Root of three) = Watts.

Since this kiln only uses two of the three phases it is simply Voltage X Current for all cases.

 

[neilestrick]

The downside of Nabertherm kilns is that replacing bricks is a real bear due to the one piece outer jacket design. Also, diagnosing electrical problems can be difficult. The last Nabertherm wiring diagram I looked at was 5 pages instead of the typical 1 page. It's German engineering for sure! They use very good parts, like solid state relays, but they can be expensive to replace. If you're not adept at kiln repair, make sure you have a repair person in the area that you can hire should the need arise.

[Bill Kielb]

The more I read about this kiln the more impressed I am. I downloaded and read the manual. Among the goodies, Solid state relays so no nuisance relay replacement and relay noise. Lid cutoff switch, flexible program controller.  And originally I started writing this to warn of slow cool programs executing properly in a well insulated kiln. To my surprise they have provided for this as well as a connection to remove off gasses. As far as replacing refractory, maybe an issue, maybe not since it is unusual to replace in the short term and removing the outside jacket is in my view an acceptable price to pay for the better thermal design and payback on each firing in electric savings.

We have some Cone Art studio kilns with well over 1000 firings that we just replaced the top section of bricks on. It is a similar kiln just not quite as thermally efficient (Only 1" of rigid additional insulation) as the '60eco. At $0.10 - $0.15 US dollars per KW these kilns have been our most economical workhorses and the stainless outer wrapping has really preserved the fire brick.

The Solid state relays answer part of the variable wattage and should allow the elements to last a bit longer as well as provide smoother temperature control than turning elements completely on then off as a means to regulate temperature rise.

Overall I went from skeptical to reasonably impressed if the literature is accurate.

Best of luck in beginning firing!

[Bill Kielb]

Maybe, but if the bricks were the driving criteria then we all would be buying 1950’s flathead engines and stacking bricks in our kiln doorways because replacement is easy. If he is comfortable about learning how to maintain his kiln it most likely will be  changing elements which are reasonably easy after the first change out. Solid state relays (good ones) have proven extremely reliable throughout industry. I have replacements in operation today  with over ten years of service on them ( all duty cycles) and changing them is pretty straight forward plug and play wire for wire stuff anyway.

if he is Squamish about learning how to repair and is fearful of calling a tech as well, then any old style kiln he buys will almost surely  require relays and elements earlier than this kiln., with this one potentially not ever requiring relays.  Again bricks usually last a long time,  unless one is careless in operation.  I am not sure he should base his entire decision on bricks and wiring. I would hate to discourage him solely on that basis.

Now out to purchase my new Tesla, but it requires a 240 volt charger!

All kidding aside, the maintenance is worth noting.

[neilestrick]

It's rare that I replace elements in a kiln without replacing at leas one brick. Accidents happen, it's not about being careless, and ease of repair and repair costs should be a factor. It's the same reason you don't buy a Mercedes with 100,000 miles on it- the repair costs will eat you alive. Seriously, though,I'm not trying to discourage, just making him aware so he can make his decision based what aspects of kiln ownership are important to him. Not all kilns are the same. Being able to do repairs yourself is a big deal for some people, and these kilns have the most complex engineering of any kiln I've seen. It's not an easy control box to work in, and for someone who isn't familiar with electrical systems, this would be a very daunting adventure.

Good discussion!

[VladCruceanu]

Thank you all for joining this discussion and sharing your opinions, it’s very helpful.

I will probably buy the electric kiln. I am also considering a wood kiln but it is a pretty complicated project and much more expensive. Will see.

[Bill Kielb]

Good for you, maintenance can be challenging but after looking at the elements in this kiln Neil is right. I would make any tech I paid to replace these fix any brick he damaged doing it.

More importantly wood fire kiln? Fantastic! I hope you get to do both! 

 

[neilestrick]

13 hours ago, Bill Kielb said:

Good for you, maintenance can be challenging but after looking at the elements in this kiln Neil is right. I would make any tech I paid to replace these fix any brick he damaged doing it.

 I think you misunderstood me when I said I rarely replace elements without replacing a brick. I didn't mean that I break them during the repair, I meant that bricks get broken during regular use. There are almost always chips in the element grooves that are large enough to cause elements to sag, so I replace those bricks when I replace the elements. There's no reason for bricks to break during element replacement, but shelves banging into the bricks cause a lot of damage.

[PeterH]

Can you confirm that your power supply is 220v? [1]
How would you feel if the 1-phase power was 3.0 kW rather than 3.6 kW?

Regards, Peter---
From the US site discussed by Bill Kielb the 3.6kW seems to be for a 240v US power supply. With the same
elements on a 220v supply this gives 3.0 kW (P=iV=V^2/R).

[1] Only if you really want to know...
A quick google will give the impression that the whole of Western Europe  receives a  230v  power supply (https://www.worldstandards.eu/electricity/plug-voltage-by-country/).
While it is true that the power companies conform to the appropriate 230v European standard, this simply means that any voltage in
the range 206.8v-254.4v is allowed. My understanding is that the power companies simply continue to supply the voltages they have
been using since WW2; ~220v for mainland Europe, ~240v for the UK (https://www.schneider-electric.co.uk/en/faqs/FA144717/).

 

[Bill Kielb]

2 hours ago, PeterH said:

Can you confirm that your power supply is 220v? [1]
How would you feel if the 1-phase power was 3.0 kW rather than 3.6 kW?

Regards, Peter---
From the US site discussed by Bill Kielb the 3.6kW seems to be for a 240v US power supply. With the same
elements on a 220v supply this gives 3.0 kW (P=iV=V^2/R).

[1] Only if you really want to know...
A quick google will give the impression that the whole of Western Europe  receives a  230v  power supply (https://www.worldstandards.eu/electricity/plug-voltage-by-country/).
While it is true that the power companies conform to the appropriate 230v European standard, this simply means that any voltage in
the range 206.8v-254.4v is allowed. My understanding is that the power companies simply continue to supply the voltages they have
been using since WW2; ~220v for mainland Europe, ~240v for the UK (https://www.schneider-electric.co.uk/en/faqs/FA144717/).

 

It appears that since the device was created as a  voltage tolerant product it was designed for the inevitable variablility.  It is well insulated so likely performs as well as practical under the expected conditions.. at 200 v the thing will likely draw under 20 amps so it amounts to what we think of  as a big test  kiln.  I am not sure rated wattage is an issue anymore.. In most of North America we have grown accustomed to  inexpensive and stabile electric comparatively speaking. I think he has enough now to answer his original question.

[Bill Kielb]

On 11/27/2018 at 7:21 AM, neilestrick said:

 I think you misunderstood me when I said I rarely replace elements without replacing a brick. I didn't mean that I break them during the repair, I meant that bricks get broken during regular use. There are almost always chips in the element grooves that are large enough to cause elements to sag, so I replace those bricks when I replace the elements. There's no reason for bricks to break during element replacement, but shelves banging into the bricks cause a lot of damage.

Maybe but he is buying a brand new mercedes, likely with a warranty. Bricks get damaged in all kilns though careless loading / unloading  ( a two cu ft kiln, not usually as much) and simpler designs will likely require maintenance sooner so I am not sure worrrying about learning how to take apart this kiln is all that relevant. 

 Bricks last a long time comparatively speaking to relays and elements. It seems like a nice well built kiln. To me it is starting to become a primary point of discouragement.

It is a component of his decision we just disagree on how much  of a component it should be. To me his operating cost will likely be a primary concern.

we just have different perspectives.