Hot spots at higher watts.

[skocha361]

Hey, guys. So, straight to the point. I was using a Sigelei 50w V2, with a few toppers. I upgraded to the Sig 150 TC, and this is when trouble started.

I run 26g SS and kanthal wrapped around 2.5mm, anywhere between 0.2 - 0.4 ohms.

At about 75 - 80 watts, after a few seconds, the very center of one coil gets a dull red and gives the worst hits. This has been happening with SS coils, Kanthal, 0.2 ohm, 0.35 ohm, etc.

The positive post for the cooler coil hasn't been screwing down as far. Replaced it with a spare. It now screws down farther, but is still stiff. Still getting the hot center on one coil after a few seconds.

I've been reading around for the past couple days, and haven't been able to find much. Any insight from you more experienced vapers? Time to retire atty? Thicker wire? Thanks in advance

 

[JERUS]

The center of your coil is what heats up first, so that's normal.

What it sounds like is either your wick isn't getting enough juice as that should be absorbing that level of heat cooling the coil and instead creating vapor. Or your coil is simply too hot, you can change that with a few things. Twisted wire is great for this, as 2 strands of twisted wire will act basically as 2gauges lower but cooler than just that same wire 2 gauges lower. To be a bit more thorough, go to the steamengine coil wrapping area. Take a 24g kanthal build with 2.5mm post at .4Ω.

Now, change that to 26g but twisted (say 1mm pitch). With the untwisted 24g you'll see you want ~4.5 wraps and your heat flux is 110 mW/m². Now look at the 26g twisted,you're at ~4.25 wraps but your heat flux is now 55 mW/m². Again, roughly the same build, but half the heat flux.

This does have a downside as ramp up time is hurt, but in my experience with 22/24/26g twist builds it's not bad with just two strands, almost unnoticeable, especially with SS which has a lower ramp up time itself. It wasn't until I tried 3 strands twisted with Kanthal that I felt hindered by that ramp up increase.

What I use now is mainly SS twisted bases, if I notice the issue you're describing I first take a look at my wick, if I can't think of something to improve there I think of how to reduce my heat flux. With that for a few builds I've done twisted SS (at like a 2-3mm pitch) then I helix it (wrap in the grooves of the twist, on one or both sides) with Kanthal and this cools it down. For example my first SS build with my TFV4 was 24g SS twisted, well if I took a deep hit, it got way too hot. So I built a new coil out of the same 24g SS twisted but this time helixed on both sides with 32g Kanthal, it's an excellent coil now, solid ramp up time due to the SS but it doesn't get out of hand like it did without that helix.

I don't swear by Steam Engine, but it's a solid guideline. Certainly something that should be referenced. But, anyways that's my thoughts, either check your wicking or try a coil with less heat dissipation, it may affect ramp up times but trial and error should let you eventually dial in the best coil for the job.

 

[zaroba]

Sounds to me like the heat output is exceeding the cottons wicking ability.
Easiest solutions are to drip more often (every 2-3 hits to keep the coils wet) or turn down the wattage.

I notice this with my RDAs. I only go up to 90 watts on my 20 gauge 0.12ohm builds, after that it becomes real easy to burn the cotton since it simply can't wick fast enough to keep up with my vaping. Some of my higher ohm RDAs, like my current 0.18ohm, top out at around 75 watts. Yea, I can go higher on both of these if I wait between hits or take smaller hits, but it is pointless because ramp-up time still comes into play.

Have been a few times I've had the wattage high, like 100 watts, to get the coils hot and then lowered it to 75 for following hits so the coils wouldn't over heat as easily. Works but can be a hassle. Could call it manual temperature control.

 

[joeyboy]

I don't know if this applies but I had to rewick again, did it yesterday, my 22g kanthal 0.3 build. The very first time was great but yesterday was just not right. The whole "less is more" theory did not work with this coil because the less I use for my mutation 1.0 coil does not work with this. Now it is great.....flavor and wicking.

Maybe you need to turn the watts down, too.

 

[skocha361]

Forgot to update how I fixed it. The heax flux @ 80w, according to steam-engine, was in the red. About 400 units, I think. By buiding a dual parallel coil, 25g kanthal, 0.22ohm, closer to 200 units; I am now able to hit it at 85w and above.

The heat flux and heat capacity parameters are good things to learn.

 

[Neunerball]

...The heat flux and heat capacity parameters are good things to learn....

Yep!

In addition, I had a problem as you described once. Turned out, the one coil, that was heating up to the extreme, had one wrap less, than the second coil.

 

[skiibo4200]

this type of problem happens a lot when building it can be many many things, from improper wicking to improper coil builds, but this will happen from time to time with me and it is usually that I need to tighten down a coil or pull out the ceramic tweezers and give my coil a few good squeezes, I've noticed this happens more the more complicated a build gets like my stapled helix coils I have to clean re tighten and tinker with every few days. where a standard parallel build you hardly have to look at again after its installed. just my experience.

 

[skiibo4200]

also don't use junk cotton sounds like a lot of ppl have the same type of problems cause they just use bad cotton. cotton candy and cotton bacon are the two cottons I use and I have no issues wicking and I can pump my mech builds up to 220w and get no dry hits until my juice is gone.