Hot air station element insulator query - Page 1
Forum section: electronics / beginners

author: algorithm
author_rank: Regular Contributor
timestamp: June 18, 2022, 10:03:12 am
content: Is it ok to use a hot air handle if it lacks the mica sheet around the element?

author: Gyro
author_rank: Super Contributor
timestamp: June 18, 2022, 10:08:38 am
content: Hard to say without seeing pictures, but if the outer barrel and any exposed metal at the tip are solidly earthed, there shouldn't be a problem.

author: Ian.M
author_rank: Super Contributor
timestamp: June 18, 2022, 10:18:50 am
content: Without the mica to partition the air flow, its likely to transfer more heat to the barrel. For brief use, Gyro's probably right, but if you use it for an extended period there's a risk the barrel running hotter may melt the handle or degrade its anchor points till it break loose. Also if its a mains powered element, does it have adequate clearance for the voltage without the mica present?

author: Gyro
author_rank: Super Contributor
timestamp: June 18, 2022, 10:24:12 am
content: QuoteGood point.

author: Fraser
author_rank: Super Contributor
timestamp: June 18, 2022, 11:18:01 am
content: A glass or mica insulator is mounted in the barrel for good reason. The heating elements in most hot air stations are of an open design, either ‘birds nest’ or ‘helix on a ceramic former’. In either case, the heating element needs to be insulated from the metal barrel. Removing the insulator from the barrel is a breach of the units safety integrity, even if the metal barrel is earthed (not always the case).I have to ask why you would wish to operate a mains powered heating element without its safety insulation in place ? Replacement parts for common budget hot air stations are not expensive and this scenario appears unnecessarily dangerous to even contemplate. If you do use the hot air station without the insulator, expect the heater to either trigger your house RCD/ELCB or burn out as it contacts an earthed barrel. If your metal barrel is not earthed, the hot air station will likely work but you will effectively have a ‘live’ metal barrel if the heater contacts it.Please spend the money on the required replacement parts and do not take risks with safety.Fraser

author: Gyro
author_rank: Super Contributor
timestamp: June 18, 2022, 12:48:58 pm
content: Hmm, I was reading it as the OP having purchased a station and found that it doesn't include any insulating sheet inside the barrel. OP clarification (and image) needed I think - one line isn't much to go on.

author: Fraser
author_rank: Super Contributor
timestamp: June 18, 2022, 01:12:12 pm
content: Gyro,Very good point !Yes I read it as though the OP wanted to use a hot air station without the originally fitted Mica or glass insulating sleeve. I own PACE hot air stations that do not use the Mica sleeve as the heater cartridge includes the metal barrel with a custom ceramic heater support providing correct distancing between heater and metal barrel. Some of the newer hot air stations may do similarly ? Good point though as designs do change/advance.Fraser

author: algorithm
author_rank: Regular Contributor
timestamp: June 19, 2022, 04:34:50 am
content: Well in my strange case, years ago bought a handle without the matching station.Idea was to make the handle work with a supply for element and supply for fan.Give element full volts but vary the fan supply. (From what I understood how the cheapest air stations work- or 2 volt variation to element, like 24 full, 9 from 0 to middle)Although when I actually tried to make it and find out what voltage the element got. I was confused, read conflicting statements, 1 saying the element was on 220 mains the other saying 24v.I found out that likely the latter was right. But, I bought a element cheap from china, it was 110v it said, but that referred to station transformer I guess lolWhen I swapped elements to what I thought was mains powered, the mica paper was stuck in the pipe, the new element came with mica, I double layered the mica thinking if one is good 2 must be twice as nice.When I hooked it up it got hot, but then too hot. When I tried to run it it started smoking after 7 seconds. I mean pluming smoke. The tube is all rainbowed from heat. It melted the spring around the element in twain. It stopped gettin hot then.But worse is both mica sheets burnt through, I threw the particle shedding fragments away. So now I have an element that I can only presume wants 24vac. But no mica sheet. Well I can look at fitment and see if there is by design safe space but if any wobbling Ill just keep it as a spare and hold out for mica sheet, better safe than sorry.Thanks for the replies yall.

author: algorithm
author_rank: Regular Contributor
timestamp: December 14, 2022, 07:23:25 am
content: Back trying to finish cobbling this.I got a replacement mica sheet. Wired a dc jack to the heater and sent 24vac to the heater element. Didnt get hot though.My research found the 110v element can do 700w max.But now im confused because it seems to me my breakers being 15a would hAVe thrown a breaker. But my elements wire burnt apart like a fuse. I was giving it 120v. Because I assumed 110v referenced the power for heater. But I guessed it was for station after it burnt apart. Now im not sure if it should have worked.Am I right in assuming it doesnt maTter much about the voltage. But the amps do?How would I put a mains wire on this and limit the current so it doesnt melt in half?I have some 5w cement resistors handy.If doing this with 120 isnt possible what would be the simplest circuit I could build? I dont need temp control or that magnetic sensor soft power. I will plug it in to turn it on. (I rarely would briefly need hot air so not much risk of me forgetting its on after plugging it in for a job) I have a few ac and dc wall supplies for a circuit. Have some bt137s. Buf would prefer a mains cable.The element has 36 ohms.

author: tooki
author_rank: Super Contributor
timestamp: December 14, 2022, 11:31:31 am
content: Quote from: algorithm on December 14, 2022, 07:23:25 amWhy would you expect it to pop a breaker? 700W/120V = 5.8A, well below the 15A breaker.Quote from: algorithm on December 14, 2022, 07:23:25 amAbsolutely not correct!!Quote from: algorithm on December 14, 2022, 07:23:25 amAmps (current) are theresultof volts (voltage) vs ohms (resistance).Quote from: algorithm on December 14, 2022, 07:23:25 amP = V2/R ==> V = sqrt(P x R)sqrt(700W x 36 ohms) ≈ 159V.Since the resistance of the element will go up once hot, that’s plausible for a 230V element. (It’d draw 6.4A initially till hot, and when hot, resistance would rise to about 75 ohms and current would fall to about 3A.)Quote from: algorithm on December 14, 2022, 07:23:25 amIf the one that melted was 36 ohms cold, it was literally not possible for it to instantly melt on 120V. Ergo, the one that melted was either a bona fide 24V element (which would be about 0.8 ohms hot, and probably 0.2 ohms cold), or it was damaged or shorted in some way, such that the effective resistance was lower than expected.Quote from: algorithm on December 14, 2022, 07:23:25 amHonestly, you should build anything. Your electrical knowledge isn’t yet quite where it needs to be for you to be safely working with mains voltage.Given that you can buy an 858D hot air station for $35 on Amazon, there simply no sense in building your own, especially given that you aren’t yet at a place where you can work with mains safely.

author: algorithm
author_rank: Regular Contributor
timestamp: December 14, 2022, 08:57:38 pm
content: Why would you expect it to pop a breaker? 700W/120V = 5.8A, well below the 15A breaker.Thanks greatly for your proper thorough response. Criticism aside its helpful.As in, a breaker would trip before the element would melt. But that math isnt right really I guess. But just my suspicion that the melted element had an issue. Not that I gave it too much juice. Because that was my assumption initially months back.Quote from: algorithm on December 14, 2022, 07:23:25 amAmps (current) are theresultof volts (voltage) vs ohms (resistance).Excuse my blunder, how silly of me to forget simple fundamentalsQuote from: algorithm on December 14, 2022, 07:23:25 amP = V2/R ==> V = sqrt(P x R)sqrt(700W x 36 ohms) ≈ 159V.Since the resistance of the element will go up once hot, that’s plausible for a 230V element. (It’d draw 6.4A initially till hot, and when hot, resistance would rise to about 75 ohms and current would fall to about 3A.)At 3a wouldnt that be around 400w?Hmm. So if I gave that element 120v it should have been underpowered it being the same exact resistance? Or am I tripping about that too.If the one that melted was 36 ohms cold, it was literally not possible for it to instantly melt on 120V. Ergo, the one that melted was either a bona fide 24V element (which would be about 0.8 ohms hot, and probably 0.2 ohms cold), or it was damaged or shorted in some way, such that the effective resistance was lower than expected.Ok, thanks for clarifying my concern. Good to know I was right to question that at least.Honestly, you shouldnt build anything. Your electrical knowledge isn’t yet quite where it needs to be for you to be safely working with mains voltage.Given that you can buy an 858D hot air station for $35 on Amazon, there simply no sense in building your own, especially given that you aren’t yet at a place where you can work with mains safely.If that worries you you should see what I work with elsewhere. Like transformers bigger than your skull outputting enough volts to make a pair of hands entirely combust if incompetent or complacent. While you are entitled to your opinion and I appreciate it. I can assure you me handling 120 is no concern. Heck I could jump rope with 120! (Thats a joke by the way, obviously dont do something so foolish. Research the 1 hand technique if you dont already know.)Well I came here hoping to form some sort of plan to prevent melting 2 elements. But if I do either get a working setup or melt another ill report back.Just the numbers tooki posted should be plenty for me to figure out the constraints.