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2 series heat gun elements
Has anybody stacked 2 heat gun elements in series in a single air tube? Seems like if a single element is not quite enough by us, a second in series might add some additional capacity. Or would the increased resistance lower the resultant temp?
jbrux4 built this way with 2 heat gun elements here post #97;

Edited by CK on 01/31/2023 8:55 PM
I built mine like this in post #29 and #47 with two popper heaters on separate circuits.
I understand phases matter when you're running a motor so if it is3*220v it is 3 phase... That being said 3*220V heating elements shouldn't require you to use different phases.

Here is a 4400W 230V 6.38A 3 wire heating element.


Now if you felt like using a step up transformer and spending more money than it makes sense to do you can get into 440v heating elements and I've seen these on Aliexpress putting out 15,000W.... Don't think you're going to need that...

I've not tried either of these approaches nor would I necessarily trust anything that is UL or CE rated. (lots of insulation anywhere there could be a potential short and maybe a GFCI breaker with everything grounded out).

I just don't understand how you're going to double stack in the same tube without burning up some wires. You would almost have to split the tube to run to different heating elements and then run back in, or you could buy one of these and not have to stress.
Edited by renatoa on 02/01/2023 1:40 AM
230V is between any phase and the null, 400V is between phases.
You need no transformer.
Check attached figure also.
renatoa attached the following image:
So it appears that the consensus is that 2 series element on a single 20 amp (120VAC) is not expected to work? I think I can make the wiring work. I’d like to build a unit that can roast 250 - 500 kgs.
Hundreds... per month maybe... Shock
Look for other principle, fluid bed is not for big batches.
Hot air yes, but mechanical agitation.


BadHabitRoasters wrote:

So it appears that the consensus is that 2 series element on a single 20 amp (120VAC) is not expected to work? I think I can make the wiring work. I’d like to build a unit that can roast 250 - 500 kgs.

There are several examples including CK's referenced builds that have been successful in roasting up to 500 grams on a 120 volt 20 amp circuit. The wiring between the 20 amp breaker and outlet would need to be checked for proper wire gauge commensurate for the wiring distance.
When determining feasibility of stacking two elements, the critical issue is ensuring the wire insulation exiting the downstream heater is able to handle the highest temperature expected to leave the first element and that the chosen heaters are capable of flowing the needed cfm without undue resistance to airflow. Some of the smaller diameter ceramic types (less than 2" diameter) would require an extremely high static pressure to hit the needed cfm.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
Sorry, are we talking here about hundreds of grams or kilo ?
Sorry, should have stated the goal. 250 kg up to 500kg is what I’m aiming for. I see elements used for roasting 250 - 400 kg with a single 120 VAC circuit but wondering if I can series 2) 120 VAC elements to extend capacity to 500?
Edited by BadHabitRoasters on 02/03/2023 8:06 PM
Where we can see such element/machine, please ?
Are we really talking about a FB roaster, or a laundry dryer machine ?
So sorry. I assume everybody is here in my head with me. I'm in the parts collecting stage. I am in the US so all voltage will be 120VAC. I will be controlling with a TC4 and aArtisan software. I have a Bake-a-round RC with a cocktail shaker lid for the base. I will probably end up welding the base to a sanitary fitting system for quick removal but for now will just be clamped with hose clamps. I have a stick vacuum cleaner motor that is advertised to be rated at 240 watts. I have an old heat gun that I've measured at 900-100 degrees F (fan is pretty low in CFM) but know that that temp will drop when I push more air though it. I understand the added complexity of wiring 2 heating elements but am wondering if that's even an option if I don't have enough heat with 1.
ok, ok... then why are we talking about hundreds of kilos roasting ?

As far as I read in many threads, 230V is also available in US...
Handling more than 20 Amps is not an easy job... I have troubles with my 5kW water boiler that is rated 22 Amps from 230V, so I try to stay away from such currents.
Sorry again, probably 1 too many beers and used metric because more here use it but not my normal unit. I meant 250 to 500 grams. I/2 to 1 pound finished weight. Now I understand your dryer element. And yes, 250 is easy enough but would require some new wiring circuits in my garage, which I’d rather not have to.
Why not hook up multiple elements in parallel? That's what I did and I run it off a 30A,120v circuit (US). I can do up to 1.5lb (700g) per batch with an extender on my chamber. The basic RC can do up to 350g with 225g being my usual batch size.
After reading some of the other threads about 1 LB setups, I see that I will need 220VAC or 2) 110 VAC circuits or a 30 amp like you have to make that happen. I can do all of those but I was hoping to not have to. Now I understand why some have multiple fluid beds. A single circuit 110 can be used in almost ny location and a 220 or 30 amp 110 will be limited to where you have the wiring for it.
For more than half pound, FB for me is no more a design to consider, for household usage.
Too hunger power, too noisy, no perceivable advantage over alternative designs.
Thanks for the comments from a voice of experience!
D'oh... looking at your setup, so you are a TO guy...
Feeling like trying to sell ice to an Eskimo Grin


BadHabitRoasters wrote:

... a 220 or 30 amp 110 will be limited to where you have the wiring for it.

Just because your machine may be capable of drawing 30A doesn't mean you have to use it all. I take my roaster to family and friends homes and run it on their 15/20A circuits. You just have to be mindful and keep your batch size smaller. I have a power meter on the roaster so I can see line voltage, amps and watts.
Renatao, my original TOSC is what I'm using for roasting now. The roaster in my profile pic is hacked together system that never quite worked. I have moved a couple times and never had time to fix it. I've always wanted to build a roaster that I could really control so I've started a fluid bed.
treyd, good point. Do you have any pics of your heating element setup?
Is debatable about how easier is to "control" a FB versus a TO.
Power wise they use the same circuits to control the heater, but as agitation and heat distribution TO is easier to figure.
And one variable less to fight, for TO... constant airflow.

If you decide, I would love to assist you to make that TO working.
Thanks for the offer. After I get my FB working, I might revive that project. The real reason I paused it is that I'm close to a "0" when it comes to programming and I finally realized I was in way over my head to get a TC4 integrated. Here the thread from when I was working on it back in 2013

Edited by renatoa on 05/21/2023 2:03 AM
Wonderful build, the closest to mine I seen so far in this forum, thank you for pointing me there.

But you don't need any electronics attached to do a good roast... I know it sounds as an heresy... Shock
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