CraftWEB Hot Glass Talk  

Go Back   CraftWEB Hot Glass Talk > Hot Glass > General Hot Glass Discussion

Reply
 
Thread Tools Display Modes
  #1  
Old 08-30-2020, 08:11 PM
Peter Bowles Peter Bowles is offline
Registered User
 
Join Date: Sep 2002
Location: Breadalbane, Tasmania
Posts: 639
Peter Bowles is on a distinguished road
Gas Furnace to Moly Conversion

Hi All

I'm trying to scope out the practicality and feasibility of converting my existing gas furnace to a moly. I'm moving studio and the move is giving me the impetus to make these changes for the next venture.

I'm doing as much of the background reading around moly and control systems here and a couple of other places and everything gets pretty murky pretty quickly in my limited electrical knowledge.

What I do know is that I can't afford to get the sizing of the control system wrong, everything in Tasmania comes in from afar with additional cost and often delay so I'm going to need some expert input and I'm not quite ready to have a conversation with Cheyenne till I'm not so in the dark and don't look such an idiot.

What I do know:

I've got an internal chamber of 19.5 of your cubic feet, which once the crown is modified will come to 16.3 cubic feet. The furnace takes a 24 inch diameter pot of approx 300lb. There is an additional space at the back of the furnace where I was once going to put a couple of small colour pots, I could modify the build and get the volume down to around 13.5 Cubic feet if needed.

At a recommended 2000 - 2200 watts per cubic feet that comes out to 32 - 35.8 kw which seems high for a 300lb furnace which I've seen as needing 22-24kw.

I've got 3 phase distribution board with a 63A mains breaker and Australian voltage is 240v single phase 400v 3 phase.

The furnace is lined with 2 inch dense refractory castables and backed up with 4-6 inches of insulation castables / fibre. It's probably a little heavy in thermal mass and a bit light on insulation in comparison to other furnaces out there.

I'll be melting batch once a week to once a fortnight.

First off, I'm having trouble making any sense of how many KW I've got available - there seems to be so much conflicting information regarding 3 phase and how much power it can actually deliver, so maybe that's where I need to start.

I'll be running a small kiln as a hot box - single phase (240v 3.6kw) and an annealer rated at 3 phase 3x240v, 3 x 3.6kw. Plus lights etc.

An upgrade to a 100A supply is possible, anything over 100A gets very expensive here and probably prohibitive - especially in these times.

Any thoughts please? I just need to know at this point how this is looking.

Thanks

Peter
Reply With Quote
  #2  
Old 08-31-2020, 07:41 AM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 22,199
Pete VanderLaan is on a distinguished road
the refractory brick interior is not dissimilar to the castings Steve had in his. What is critical is no unnecessary dead air space. That means no combustion chamber essentially. Having the extra AMPS (2200) means it will respond better when you are preparing to turn it up to charge. The chamber height is really going to be determined by the length of the elements. Mine was larger and accommodated a 28 inch pot if I wanted and it ran on 22KW. It did have a 120 AMP breaker. It was also sluggish and I turned it up the night before to get a head start. I only used my own fine powder batch.

I don't know how anyone can do this with a 100 AMP Service. Scott Benefield has the same problem in Northern Ireland and he doesn't have a moly. Something about former colonies getting what they deserve.

When I ran mine with the color pots, I did have three 75lb pots in there. I never ran it the way it was intended. The KW usage you cite seems ridiculously high. I can't recall any of the big moly's using more than 22.5 unless you're talking the 34 inch units. That's a big pot.

I had a 30KVA Transformer with six 9/18 312/500 elements.

I went back to gas and vastly prefer it.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #3  
Old 08-31-2020, 08:53 AM
Antti Torstensson Antti Torstensson is offline
Registered User
 
Join Date: Jan 2013
Location: Finland
Posts: 33
Antti Torstensson is on a distinguished road
400 V and 24 kW in a three-phase circuit draws only 20 A per phase. So I think it can be done easily with a 100 A main fuse. As that's 100 A for each phase.

Your hotbox and annealer together draw 30 A.
Reply With Quote
  #4  
Old 08-31-2020, 09:33 AM
Josh Bernbaum Josh Bernbaum is offline
Registered User
 
Join Date: Feb 2009
Location: Brattleboro, VT
Posts: 719
Josh Bernbaum is on a distinguished road
I don't know enough about 3 phase, but I can maybe add to the discussion at least a little bit based on my single phase setup. I have a moly with a 22" pot/200# rating, 15kW transformer, and it's hooked to an 80A circuit breaker. I have a 400A single phase service/main breaker, but I know that's a bit overkill although I do also run an air compressor motor, an O2 generator, my welder, other ovens, etc. My guess is that I'd have some issues if I had anything less than 200A service to the building.
__________________
www.jmbglass.com
instagram.com/joshbernbaum_glass
Reply With Quote
  #5  
Old 08-31-2020, 11:12 AM
Shawn Everette Shawn Everette is offline
Registered User
 
Join Date: Mar 2013
Location: Indianapolis, IN
Posts: 696
Shawn Everette is on a distinguished road
Always get as many amps as you can. Always. 10 amps is not much in the way of overhead, and wouldn't follow the 80% rule. The small things can add up quick, and a motor with a high start pull, think ac, is a surefire way to trip the main when everything's humming.

I'm curious why your 3 phase annealer is running on a different voltage than the furnace?
Reply With Quote
  #6  
Old 08-31-2020, 02:42 PM
Antti Torstensson Antti Torstensson is offline
Registered User
 
Join Date: Jan 2013
Location: Finland
Posts: 33
Antti Torstensson is on a distinguished road
Quote:
Originally Posted by Shawn Everette View Post
I'm curious why your 3 phase annealer is running on a different voltage than the furnace?
It's just a matter of connecting the neutral wire or not. If you were to wire the annealer for line voltage (400 V) it would require almost three times the amount of heating wire compared to wiring it for phase voltage (240 V). In this case it would only save you few amps.
Reply With Quote
  #7  
Old 08-31-2020, 04:13 PM
Shawn Everette Shawn Everette is offline
Registered User
 
Join Date: Mar 2013
Location: Indianapolis, IN
Posts: 696
Shawn Everette is on a distinguished road
Doesn't that make it not 3 phase then? Maybe "2 phase", like a dryer. Is 400v set up different than 240v? All 240v 3 phase I've experience has 2 120v lines and a 240v, where any combination gets you 240v. Using the ground would get you 2 lines running at a lower voltage.

I also wasn't under the impression that each phase didn't add up to the same total on the main breaker. If that's not the case then essentially you'd have 300a on a 100a service.

Last edited by Shawn Everette; 08-31-2020 at 05:20 PM.
Reply With Quote
  #8  
Old 08-31-2020, 04:54 PM
Antti Torstensson Antti Torstensson is offline
Registered User
 
Join Date: Jan 2013
Location: Finland
Posts: 33
Antti Torstensson is on a distinguished road
I'm only familiar with the Finnish 3-phase supply, which at least voltage wise is similar to the OP's, 400V/230V. The voltage between any two phases is 400 V and the voltage between any phase and neutral is 230 V. So you can easily use either voltage depending on your needs. Generally 400 V without a transformer is too high for any kind of glass kiln.

Did some googling based on what you described and found out this: https://ctlsys.com/support/four_wire_delta_circuits/

Never heard of high-leg delta service before but apparently it's common at least in North America. This of course reveals that you have to be cautious giving or receiving electrical advice on a discussion board with an international audience.
Reply With Quote
  #9  
Old 08-31-2020, 05:22 PM
Shawn Everette Shawn Everette is offline
Registered User
 
Join Date: Mar 2013
Location: Indianapolis, IN
Posts: 696
Shawn Everette is on a distinguished road
Yes, I've only encountered high leg systems, so that's what's causing the confusion. Might be different on a 400v US system, but I haven't worked with those.
Reply With Quote
  #10  
Old 08-31-2020, 05:29 PM
Antti Torstensson Antti Torstensson is offline
Registered User
 
Join Date: Jan 2013
Location: Finland
Posts: 33
Antti Torstensson is on a distinguished road
Regarding the main breaker and three phase breakers in general, the rated current is per phase. So you do get three times the power out of a three-phase service compared to single-phase with the same size breaker. That seems to be the case also in USA.
Reply With Quote
  #11  
Old 08-31-2020, 05:34 PM
Art Freas Art Freas is offline
Registered User
 
Join Date: Aug 2014
Location: Washington
Posts: 710
Art Freas is on a distinguished road
Here is what looks like the 400V 3ph version of the diagram.

https://d2vlcm61l7u1fs.cloudfront.ne...FphpYgWZ9j.png
Reply With Quote
  #12  
Old 08-31-2020, 05:59 PM
Shawn Everette Shawn Everette is offline
Registered User
 
Join Date: Mar 2013
Location: Indianapolis, IN
Posts: 696
Shawn Everette is on a distinguished road
That is totally not what the engineers were telling us when we moved to our new location, I'm pretty sure we ended up with something crazy like a 600a service. Even with that they were acting like we were barely going to be able to run anything.

We ended up buying a gb5 with a power share to see how that could help. While I love digitry, I can't recommend the power share, all of our kilns would take twice as long to get hot, and would have major temp swings. Possibly if you had smaller or better insulated kilns.

Eventually I just fired up everything that I could full bore and nothing popped. I really wanted to murder the engineers at that point. They were some of the most incompetent people to work with from the start. Luckily our contractors were great.
Reply With Quote
  #13  
Old 08-31-2020, 10:50 PM
Peter Bowles Peter Bowles is offline
Registered User
 
Join Date: Sep 2002
Location: Breadalbane, Tasmania
Posts: 639
Peter Bowles is on a distinguished road
I think I read somewhere that for 3 phase delta without the neutral, you have to have equal loads on each phase. But that was just another rabbit whole I went down.

So, in terms of this conversation (appreciate the comment about this being an international conversation) in terms of Kw....If I have 63A 3 phase with a line to neutral voltage of 240v ...

do I have (63 x 240) x 3 = 45Kw available?

Or, do I have (63 x 400) = 25 Kw Available?

I'm really struggling with this one and everywhere I'm going to try and find out I'm getting very conflicting information.

Also, my head is spinning at a 600a service!! That sounds insane.
Reply With Quote
  #14  
Old 09-01-2020, 12:58 AM
Shawn Everette Shawn Everette is offline
Registered User
 
Join Date: Mar 2013
Location: Indianapolis, IN
Posts: 696
Shawn Everette is on a distinguished road
Moved into an old industrial area, bare bones building, but could order whatever you wanted for utilities. 14k sqf, generically large annealers, full warm shop, full cold shop, 100a neon panel, actual proper hood and make up air, and several private studios. All public access. Electric was a significant, I repeat significant, portion of the budget, but it meant that they should never want in terms of power.

The old building we got booted from was probably a 1200a+ service; was once a defense contract site, tanks fabrication is what the lore was. Had it's own transformer substation, and we didn't pay a dime for electric. Too good of a situation to last, new owners made sure of that. One day a squirrel completed a circuit on the substation, killed power to most of the block. Poor bastard was extra crispy.

Last edited by Shawn Everette; 09-01-2020 at 01:01 AM.
Reply With Quote
  #15  
Old 09-01-2020, 03:00 AM
Antti Torstensson Antti Torstensson is offline
Registered User
 
Join Date: Jan 2013
Location: Finland
Posts: 33
Antti Torstensson is on a distinguished road
Quote:
Originally Posted by Peter Bowles View Post
I think I read somewhere that for 3 phase delta without the neutral, you have to have equal loads on each phase. But that was just another rabbit whole I went down.
That's true. Any glass kiln is typically a balanced load. It just means that each phase has the same resistance ie. there's the same amount of the same heating elements in each phase. If the loads are not balanced you need the neutral wire to carry away excess current.

Quote:
Originally Posted by Peter Bowles View Post
So, in terms of this conversation (appreciate the comment about this being an international conversation) in terms of Kw....If I have 63A 3 phase with a line to neutral voltage of 240v ...

do I have (63 x 240) x 3 = 45Kw available?

Or, do I have (63 x 400) = 25 Kw Available?

I'm really struggling with this one and everywhere I'm going to try and find out I'm getting very conflicting information.

Also, my head is spinning at a 600a service!! That sounds insane.
You should have 63 A for each phase. So the theoretical maximum power you can get would be (63 x 400) x 3 = 75,6 kW. But obviously all your equipment won't be three-phase and rated for 400 volts.

In your calculations for three-phase equipment current draw you can basically use just one phase and ignore the other two. So let's say your three-phase furnace is 400 V and 24 kW. Power for one phase is 8kW and current is 8000 W / 400 V = 20 A. Your three-phase annealer is 240 V and 10,8 kW. That's 15 A per phase. And your single-phase hotbox is one third of the power of your three-phase annealer so it is also 15 A.

So all together that would add up to 50 A. That doesn't leave much room for anything else. We actually have only a 3x63A service but our furnace is just 12 kW. I've never popped the main fuse. Pretty much all of our equipment including cold working equipment is three-phase which helps alot.

Again this is the case in Finland.

Edit: I was wondering the 240 V / 400 V ratio and found out that in Australia the line voltage is officially 400 V but in practise it's usually 415 V. That would make more sense with the 240 V phase voltage.

Last edited by Antti Torstensson; 09-01-2020 at 04:36 AM.
Reply With Quote
  #16  
Old 09-01-2020, 08:48 AM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 22,199
Pete VanderLaan is on a distinguished road
Quote:
Originally Posted by Shawn Everette View Post
Always get as many amps as you can. Always.
*****
I would have agreed with this most of my life but then came the sale of NH public service to Eversource and the deal that followed from the utilities commission.

I have a 400 AMP Service, more than I would ever need but we did have the moly and a lot of big grinders- never enough to dent our potential. However, Eversource bills us at a far higher rate because we have the potential to use 400 AMPS. It's not on the electricity side, it's the delivery side of the bill and delivery is always higher than the power cost. It's Pure BS no lines have been changed or upgraded. I have never been able to get the monthly bill below $200 bucks with no draw. If it actually gets run, with no moly mind you, the usage delivery cost goes up to as high as $400. with the power- $600.00

We're considering one of two scenarios. First, rewire the house and run a line out to the shop and to then disconnect the shop entirely, or to fire up the 30KVA generator and to run the shop off of it. It's propane powered.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #17  
Old 09-01-2020, 09:18 AM
Shawn Everette Shawn Everette is offline
Registered User
 
Join Date: Mar 2013
Location: Indianapolis, IN
Posts: 696
Shawn Everette is on a distinguished road
Quote:
Originally Posted by Antti Torstensson View Post
If the loads are not balanced you need the neutral wire to carry away excess current.

Edit: I was wondering the 240 V / 400 V ratio and found out that in Australia the line voltage is officially 400 V but in practise it's usually 415 V. That would make more sense with the 240 V phase voltage.
I'm not sure how hooking to neutral "carry(s) away excess current". You're not changing the voltage of a line with a neutral, a transformer would be necessary in that situation, and load is going to be dependent on what it's using it. I wouldn't consider a standard line to neutral wiring as manipulating current, just not using the voltage boost of 3 phase.

If you take a high leg system and wire each phase to a single element and to neutral, then you'll have one element with an out of sync voltage that's probably going to pop it, or at least significantly shorten the life span. A balanced load is also important so that you kiln is heating evenly, but I have seen commercial models that take advantage of such an imbalance. Really only in "2" phase kilns for fusers, but the 240v line does the brunt of the work, while a smaller element in the kiln lid uses 120v for top fire.

"240v" is kind of a catch all here in the US, really need to take readings off the line to tell what you actually have. Majority of what I've encountered is 208v as the high leg, 110/120v for low legs, with 220v in delta configuration.

This question is aimed at the international crowd, but what kind of amperage do you typically have available on a 240v household line?
Reply With Quote
  #18  
Old 09-01-2020, 09:28 AM
Shawn Everette Shawn Everette is offline
Registered User
 
Join Date: Mar 2013
Location: Indianapolis, IN
Posts: 696
Shawn Everette is on a distinguished road
That is quite the bullshit situation you have. Nothing like for profit utilities.

Not directing this at you Pete, but I'd say figure out what you need at a minimum, and add 50%. We knew it was way cheaper for us in the end to get the system we knew would handle our anticipated load, than to retrofit it later on. There were several layout changes that could have also significantly lowered our wiring costs, but our "architect" got to be in charge of all of that.
Reply With Quote
  #19  
Old 09-01-2020, 01:34 PM
Antti Torstensson Antti Torstensson is offline
Registered User
 
Join Date: Jan 2013
Location: Finland
Posts: 33
Antti Torstensson is on a distinguished road
Quote:
Originally Posted by Shawn Everette View Post
I'm not sure how hooking to neutral "carry(s) away excess current". You're not changing the voltage of a line with a neutral, a transformer would be necessary in that situation, and load is going to be dependent on what it's using it. I wouldn't consider a standard line to neutral wiring as manipulating current, just not using the voltage boost of 3 phase.

If you take a high leg system and wire each phase to a single element and to neutral, then you'll have one element with an out of sync voltage that's probably going to pop it, or at least significantly shorten the life span. A balanced load is also important so that you kiln is heating evenly, but I have seen commercial models that take advantage of such an imbalance. Really only in "2" phase kilns for fusers, but the 240v line does the brunt of the work, while a smaller element in the kiln lid uses 120v for top fire.

"240v" is kind of a catch all here in the US, really need to take readings off the line to tell what you actually have. Majority of what I've encountered is 208v as the high leg, 110/120v for low legs, with 220v in delta configuration.

This question is aimed at the international crowd, but what kind of amperage do you typically have available on a 240v household line?
The neutral wire carrying away excess return current was just a side note and has little to do with the discussion. I simply meant that in a balanced load the sum of return current is zero, in an unbalanced load by definition it’s not and the excess current has to go somewhere. I can see the return current when my cheap Chinese SiC elements age unevenly. Right now there’s 5 A running across the neutral wire. When the loads are balanced there is no current flow in the neutral wire. I don’t know what happens in an unbalanced load without neutral connection.

I don’t understand what you mean by “You're not changing the voltage of a line with a neutral”. Voltage is the difference in electric potential between two points. A line in itself has no voltage. The difference in electric potential between two phases is not the same as the electric potential between a phase and neutral. So you do get different voltage depending on if you connect the neutral point or not.

I also don’t know what you mean by “manipulating current”. Of course if voltage goes up and power stays the same the current goes down.

I guess most of the confusion here comes from the fact that you’re thinking about high-leg delta service which doesn’t seem to be used outside North America.
Reply With Quote
  #20  
Old 09-01-2020, 03:11 PM
Shawn Everette Shawn Everette is offline
Registered User
 
Join Date: Mar 2013
Location: Indianapolis, IN
Posts: 696
Shawn Everette is on a distinguished road
Yeah, I definitely think there is some loss in translation here.

I can't say that I've been in a situation where I've experienced an "overage" of amps on a neutral line. With any of the 4 wire equipment that I've used, the only time a hot line would be run to neutral would be to power a different aspect of the machine that needed 120v, e.g. controller or relay coil. Those types of situations would register mA of pull. I also try to change coils all at the same time to avoid heat discrepancies in the kiln.

Yes, I understand there is a voltage difference if you connect 1 phase to neutral vs. another phase. That's what the 3rd paragraph was about. Just clarifying that piece of equipment should not cause a change to the voltage unless there is a transformer involved, or something is broken. That was what I was referencing with manipulating current.

I didn't pick delta, just work with what I've get, so I can't comment on the rational for what we do. About the only thing they regularly teach of electricity is to not touch it, so it was confusing as hell at first. 1+N=120, 2+N=208, 1+1=220, also 1+2=220; yeah, that's real straight forward. I cut my tech chops in a studio fixing all the things that were mostly built by drunk or stoned volunteers. Probably not the easiest way to learn a trade, but you learn what wrong looks like. Moving, installing, and updating every single piece of equipment gets you intimate with it real quick.

I'm also going to be real jealous if you guys have 20A and 240v coming out of your kitchen sockets.

Last edited by Shawn Everette; 09-01-2020 at 03:13 PM.
Reply With Quote
  #21  
Old 09-02-2020, 08:42 AM
Victor Chiarizia Victor Chiarizia is offline
Registered User
 
Join Date: Sep 2005
Location: fairview, NC
Posts: 579
Victor Chiarizia is on a distinguished road
i believe i had the last of steves moly conversion kits. my 200lb furnace runs a 30kw system... quite a lot of power but boy it's worked well over the past 15 years. i'll know at the end of september what my bill is without the studio running as we shut down for maintenance....i broke another element i think.
duke power charges ~ 7-9 cents a kw hour plus a 3-400 delivery charge. my whole studio costs ~ $12-1300 a month
Reply With Quote
  #22  
Old 09-02-2020, 12:28 PM
Shawn Everette Shawn Everette is offline
Registered User
 
Join Date: Mar 2013
Location: Indianapolis, IN
Posts: 696
Shawn Everette is on a distinguished road
Never saw the bill when I was using one of steve's molys, luckily hidden under the overhead of the rest of the Art building. $12-1500 was probably standard at my old studio, and that was with gas furnaces. Given, that was a 4 hole shop with less than efficient kiln practices. Gas had way more peaks and valleys, but a lot of that was trying to heat a leaky warehouse in the winter. Unauthorized people adjusting thermostats didn't help.

I swear people would throw tantrums if you got within 6" inches of their piece. Trying to get someone to leave up a kiln for the next person that was coming was another sore spot. They paid money, or sometimes didn't, so they thought they should be able to get to do whatever they want. Major ego and entitlement issues, especially among the "professional" glassblowers. The casuals usually weren't too bad, but the two guys that used to be factory blowers were by far the best renters to work with.
Reply With Quote
  #23  
Old 09-02-2020, 05:09 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 22,199
Pete VanderLaan is on a distinguished road
Working alone is so nice.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #24  
Old 09-02-2020, 07:22 PM
Shawn Everette Shawn Everette is offline
Registered User
 
Join Date: Mar 2013
Location: Indianapolis, IN
Posts: 696
Shawn Everette is on a distinguished road
Only real drawback is that there's no one to blame. Except for the glass, if only they made the glass better.
Reply With Quote
  #25  
Old 09-02-2020, 08:02 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 22,199
Pete VanderLaan is on a distinguished road
which could easily be done but apparently, no one wants to pay for better glass.
__________________
Where are we going and why am I in this basket?
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 12:21 AM.


All published comments within these message boards are the opinions of its contributor and does not represent
the opinion(s) of the owner(s) of this website. Please see the Terms of Use file for more details.

Books to Help Artists Avoid Online Scams: Top 10 Email Scams | Social Media Scams

Powered by vBulletin® Version 3.7.2
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
© CraftWEB.com. Opportunity Network. 2008. All Rights Reserved.