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Homeroasters - Home Roasting Coffee Community » ALL ABOUT ROASTERS » HotTop Roaster

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Using a variac with an Artisan-controlled HT?
Barrie	#1 Posted on 05/19/2014 7:32 AM
Pounder Posts: 504 Joined: April 10, 2012	I am about to acquire a Variac but have no idea how to integrate it with an Artisan-controlled Hottop. Can someone please set me on the 'right' course? The line voltage here does not change much during a roast and stays between 118-120, usually 118-119. The Kill-A-Watt shows wattage in the 710-715 range, commonly 711 with heater at 100%, and my objective is to improve RoR during a large-batch roast by raising wattage a tad (load is 283g currently). A few questions. 1. At what stage do you turn on the Variac and in what order? 2. Do you just turn the Variac up until reaching the desired wattage and leave it there, using Artisan to control everything else? Michael says that the HT elements are rated for 740 watts max. 3. With a 15 amp circuit-breaker in the line, why would a 20 amp fuse ever blow under these sort of circumstances? Can transients blow both at once? 4. Is the fan going to run faster? I look forward to words of wisdom from the cognoscenti. Barrie (San Diego, CA) "So much to learn, so little time." Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).


smico	#2 Posted on 05/19/2014 2:46 PM
1/2 Pounder Posts: 262 Joined: December 17, 2011	Barrie, 1. I set variac at the beginning of the roast and normally never touch it. If, for whatever reason, tracking of the template roast is not satisfactory, I adjust the variac a bit up or down. 2. I use maximum 130V. 3. Variac's in-rush current is many times higher than nominal, so only speed of the breaker will determine which one will trip first. Although if you have the same type of breaker, 15A will normally trip faster more often than 20A. 4. HT power unit keeps output DC constant for that kind of input voltage variations. No change in fan speed is expected. Cheers, Miroslav Hottop B2 + HTC, Cremina 83, OE Pharos, Brewtus IIIR, Baratza Vario


Barrie	#3 Posted on 05/19/2014 2:55 PM
Pounder Posts: 504 Joined: April 10, 2012	That is the sort of information for which I was looking, Miroslav. Good to hear from you. Barrie. Barrie (San Diego, CA) "So much to learn, so little time." Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).


smico	#4 Posted on 05/19/2014 5:34 PM
1/2 Pounder Posts: 262 Joined: December 17, 2011	Barrie, Just to add a line about the breaker... Most probably neither breaker will trip in your case. I connect 30A variac to the 15A breaker, and without soft-start circuit it trips almost every time. But hopefully your breaker is a bit slower and it will not budge at all. Good luck, Miroslav Hottop B2 + HTC, Cremina 83, OE Pharos, Brewtus IIIR, Baratza Vario


Barrie	#5 Posted on 05/19/2014 7:59 PM
Pounder Posts: 504 Joined: April 10, 2012	Quote smico wrote: Barrie, Just to add a line about the breaker... Most probably neither breaker will trip in your case. I connect 30A variac to the 15A breaker, and without soft-start circuit it trips almost every time. But hopefully your breaker is a bit slower and it will not budge at all. Good luck, Miroslav Hmmm. The toy arrives later this week, so I will find out, I guess. Barrie (San Diego, CA) "So much to learn, so little time." Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).


Barrie	#6 Posted on 05/23/2014 3:29 PM
Pounder Posts: 504 Joined: April 10, 2012	Quote smico wrote: 2. I use maximum 130V. Miroslav, The element in the HT is rated at 740 watts. I am not sure what that means other than it will work best at wattages up to that level. By running your variac at 130, the wattage in your machine will be well above that rated level, and although I would like to do the same, what do you think is the consequence - a burned-out element in the offing? Regards, Barrie (San Diego, CA) "So much to learn, so little time." Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).


Barrie	#7 Posted on 05/23/2014 5:47 PM
Pounder Posts: 504 Joined: April 10, 2012	Have now run my first roast with a variac and Kill-A-Watt in line, and it has been both educational and humbling. On the educational side, it is enlightening to see the wattage change as Artisan turns down the heater. The manual control provided by the variac mimics the continuously variable effect of the Artisan slider, or vice versa. Obvious, but I was startled when I first saw the watts that I had carefully increased to my selected 100% equivalent suddenly drop to a much lower level. While trying to figure out what had gone wrong, the penny dropped and I realized we had reached the programmed moment for an alarm to kick in. Oh well, the old cogs are slowing down here. The humbling moment came after the beans were ejected, and I began disconnecting things as per usual (USB cable, mini-speaker), and thought (or, rather, didn't think) that I didn't need the variac any more. So I turned it off. Darn! The thing is in-line. #*?&@. Anyone want a big handful of hot beans. Hopefully, I will be a bit smarter from here on? Barrie (San Diego, CA) "So much to learn, so little time." Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).


snwcmpr	#8 Posted on 05/24/2014 7:10 AM
1 1/2 Pounder Posts: 925 Joined: March 03, 2011	Would it be wise to order a heating element, just in case you do reach the 'point of failure', so you don't have to wait weeks for a replacement to arrive???? Just a thought, Ken in NC -------------- Backwoods Roaster "I wish I could taste as well as I wish I could roast." As Abraham Lincoln said "Do not trust everything you read on the internet".


Barrie	#9 Posted on 05/24/2014 8:04 AM
Pounder Posts: 504 Joined: April 10, 2012	Quote snwcmpr wrote: Would it be wise to order a heating element, just in case you do reach the 'point of failure', so you don't have to wait weeks for a replacement to arrive???? Just a thought, Ken in NC I wondered about that, but thought I would wait and see what the experience has been among those who turn their variacs up high on a frequent basis. My experience with wait times from HT USA has been good to date! Barrie (San Diego, CA) "So much to learn, so little time." Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).


smico	#10 Posted on 05/24/2014 10:08 AM
1/2 Pounder Posts: 262 Joined: December 17, 2011	Yes Barrie, it might shorten life of the heater. From what I read the elements seldom burn, and they more often bend after years of use as parts of heater's metal shield give up. Hottop B2 + HTC, Cremina 83, OE Pharos, Brewtus IIIR, Baratza Vario


Barrie	#11 Posted on 05/24/2014 12:14 PM
Pounder Posts: 504 Joined: April 10, 2012	Thanks, Miroslav. As you have said you turn your Variac up to 135 and leave it there I am assuming that you have not experienced any heater damage, so will try that for my next roast in the early phase. Barrie (San Diego, CA) "So much to learn, so little time." Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).


smico	#12 Posted on 05/24/2014 2:29 PM
1/2 Pounder Posts: 262 Joined: December 17, 2011	I normally don't go over 130 V, but I did try to go higher, even to the maximum my variac would provide, and no damage to report so far. Hottop B2 + HTC, Cremina 83, OE Pharos, Brewtus IIIR, Baratza Vario


smico	#13 Posted on 05/24/2014 6:05 PM
1/2 Pounder Posts: 262 Joined: December 17, 2011	Quote Barrie wrote: Quote smico wrote: 2. I use maximum 130V. Miroslav, The element in the HT is rated at 740 watts. I am not sure what that means other than it will work best at wattages up to that level. By running your variac at 130, the wattage in your machine will be well above that rated level, and although I would like to do the same, what do you think is the consequence - a burned-out element in the offing? Regards, Sorry Barrie, I did not read you post carefully and missed your concerns... Heating element is just stupid wire made of material that has high melting point. Normally heaters are rated for 1300C and higher and I have not seen on any forum burnt HT heater. After long time use heater changes shape so drum scratches the heater, and you need to spend $40 and change the heater... There certainly is a breaking point that will melt the wire immediately, but my experience is that we are not close to that point. Last winter it was 5C in my garage, and I was always running my first cold-roaster roast with highest voltage, 133V or so, 890W. Good luck, Miroslav Hottop B2 + HTC, Cremina 83, OE Pharos, Brewtus IIIR, Baratza Vario


Barrie	#14 Posted on 05/24/2014 7:38 PM
Pounder Posts: 504 Joined: April 10, 2012	Your wattage and voltage (890/133) are pretty much the same as mine, which suggests to me that your older, more 'travelled' heating element is holding up very well, despite being stressed by Variac manipulation for some time. This compared to my much newer HT that only met a Variac for the first time this weekend. I think your analysis is correct, and there is considerable reserve in the elements. You have been very reassuring. Barrie (San Diego, CA) "So much to learn, so little time." Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).


allenb	#15 Posted on 05/24/2014 10:15 PM
Administrator Posts: 3858 Joined: February 23, 2010	The tubular heating elements on Hottops are most likely using incoloy sheaths which are good to 1500 F. At 1500 F, metal is a fairly bright orange as you see when your kitchen stovetop element is on max setting. To judge whether you're putting undue stress on your Hottop's heaters all you need to do is find a way to view them while running at 130 volts and if they aren't a brighter orange than your stove's oven elements or top elements while on full power then you should get maximum life expectancy. On the other hand, if you see a color between orange and yellow then you are most likely cutting the life expectancy down by a big margin. Allen 1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana


Barrie	#16 Posted on 05/24/2014 10:39 PM
Pounder Posts: 504 Joined: April 10, 2012	A useful pointer. Thank you, Allen Barrie (San Diego, CA) "So much to learn, so little time." Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).


smico	#17 Posted on 05/25/2014 5:04 AM
1/2 Pounder Posts: 262 Joined: December 17, 2011	Thank you for narrowing down the most probable type of HT heater element Allen. I will look for the clues very next time I roast, and probably attach one thermocouple directly to the heater when I come around to do that. Hottop B2 + HTC, Cremina 83, OE Pharos, Brewtus IIIR, Baratza Vario


ciel-007	#18 Posted on 05/25/2014 9:02 AM
1 1/2 Pounder Posts: 651 Joined: April 03, 2012	Quote allenb wrote: ...The tubular heating elements on Hottops... are good to 1500 F. At 1500 F... if you see a color between orange and yellow then you are most likely cutting the life expectancy down by a big margin... Allen, might a change in the color of the element suggest a potentail shift in IR wavelength? Of so, do you have any thoughts about how such an IR shift might possibly impact the roast? Ciel Ciel... seeking Heaven in my cup with ................................................................................................................. EXPOBAR Brewtus II - MAZZER Mini E - MAHLK?NIG Vario - GeneCafe - RAF-1 Extreme (Modified B-2 HOTTOP) - BellaTaiwan XJ-101


allenb	#19 Posted on 05/25/2014 5:27 PM
Administrator Posts: 3858 Joined: February 23, 2010	After viewing a couple of videos of the hottop in operation I'm fairly certain that the percentage of heat transfer via direct IR to bean is very small due to: 1. Counter clockwise drum rotation keeps the beans mostly from a 6 o'clock to 3 o'clock position versus a clockwise rotation which would keep the beans in close proximity to the element. I'm sure this is necessary to limit the amount of chaff contacting the elements. 2. The drum's perforations appears to be around a 50% open area which would further reduce the potential for IR to play much of a role in the roasting process. With this being said, I don't suspect one would notice any difference in roast quality due to the shift in wavelength. Allen 1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana


Barrie	#20 Posted on 05/25/2014 6:21 PM
Pounder Posts: 504 Joined: April 10, 2012	You guys have moved this whole discussion above my pay scale, so to speak , but it is certainly interesting. Going back to the start of the thread, I have learned that 1. There may be a concern about blowing the Variac 20amp fuse, but the 15amp circuit breaker in the circuit is likely to cut out first. 2. One way to minimize fuse-blowing/circuit breaker switch-offs due to high-voltage ON transients could be to turn on the HT first, with the Variac OFF and the voltage turned down. In sequence, one then turns on the Variac and then moves the voltage up to the desired level. 3. When used with Artisan, the latter's slider or alarm settings use their selected percentage of whatever may be the Variac setting, whether this is in terms of volts or watts. Thus, one can set the Variac to a maximum figure/setting, and allow Artisan to take over from there, all the time remembering that relationship. 4. The physical nature of the HT heating element is such that running it with the Variac turned up to, say, 130 volts is unlikely to damage it. Experience (of others) suggests that the worst that might happen up to that level would be an eventual bending of the element. The combination of watts and time that is likely to do this remains unstated. 5. It may be useful to keep an eye on the color of the hot element, a change from orange to yellow suggesting damage from over-heating. 6. As always, watching out for chaff fires (and regularly removing chaff) is very important. If anyone feels there is an error anywhere in these six statements, please chime in. Barrie (San Diego, CA) "So much to learn, so little time." Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).


allenb	#21 Posted on 05/25/2014 8:51 PM
Administrator Posts: 3858 Joined: February 23, 2010	Quote Barrie wrote: 5. It may be useful to keep an eye on the color of the hot element, a change from orange to yellow suggesting damage from over-heating. Barrie, for clarification purposes, an element glowing brighter than orange (orange/yellow) is not an indicator that it has been damaged from overheating but is operating at a higher wattage than it can safely handle. Allen 1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana


Barrie	#22 Posted on 05/25/2014 9:24 PM
Pounder Posts: 504 Joined: April 10, 2012	Thank you for that. It gets more reassuring all the time. :-) I imagine that anyone interested will see your comment, Allen. Barrie (San Diego, CA) "So much to learn, so little time." Hottop 2K+., Artisan, Jura Capresso ENA 3 (i.e. espresso).


smico	#23 Posted on 05/26/2014 7:46 AM
1/2 Pounder Posts: 262 Joined: December 17, 2011	Quote Barrie wrote: 2. One way to minimize fuse-blowing/circuit breaker switch-offs due to high-voltage ON transients could be to turn on the HT first, with the Variac OFF and the voltage turned down. In sequence, one then turns on the Variac and then moves the voltage up to the desired level. Barrie, First, most people righteously don't bother with this problem as it doesn't exist for them: the breaker never trips. But if you want to do anything, first rule for me would be not to plug in HT until you get desired voltage (around 120V). At the end of the day you might want to add double-pole switch for convenience. Cheers Miroslav Hottop B2 + HTC, Cremina 83, OE Pharos, Brewtus IIIR, Baratza Vario

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