Basic Dual Coil Kanthal Build Issues

[westhc]

I am trying my first dual coil builds and am having some problems.
Hope someone can help.

I am building on a Bellus deck at 2.5 mm diameter aiming for around 1 Ohm.
I have tried both 28 and 29 gauge Kanthal at 8 spaced wraps per coil - these seem to fit fine on the deck.
The coils appear identical when I mount them on the deck.
The ohms come out fine - within a range that I find acceptable. I am not looking for low ohm to start with - I'm not ready to blow my head off since I have never tried sub-ohm.

I have 2 recurring issues when I test the coils.

One coil will heat fine but there is a significant delay in the second coil heating and the 2nd coil does not get as red as the first. This seems to be consistent over all the builds I have tried.
Is this normal?

Also on some, but not all, build tries the first coil does not heat from the center out but from one end of the coil to the other. What causes this? I do not have this issue on a single coil build.

I have not yet gone past building to try wicking and vaping a dual yet.

Thanks for all help.
I am perfectly happy with my 1.2-1.5 builds.
I vape mouth to lung - not interested in clouds (yet).
There is always something new to try and to learn but want to keep it in simple stages as I experiment.

 

[edyle]

I am trying my first dual coil builds and am having some problems.
Hope someone can help.

I am building on a Bellus deck at 2.5 mm diameter aiming for around 1 Ohm.
I have tried both 28 and 29 gauge Kanthal at 8 spaced wraps per coil - these seem to fit fine on the deck.
The coils appear identical when I mount them on the deck.
The ohms come out fine - within a range that I find acceptable. I am not looking for low ohm to start with - I'm not ready to blow my head off since I have never tried sub-ohm.

I have 2 recurring issues when I test the coils.

One coil will heat fine but there is a significant delay in the second coil heating and the 2nd coil does not get as red as the first. This seems to be consistent over all the builds I have tried.
Is this normal?

Also on some, but not all, build tries the first coil does not heat from the center out but from one end of the coil to the other. What causes this? I do not have this issue on a single coil build.

I have not yet gone past building to try wicking and vaping a dual yet.

Thanks for all help.
I am perfectly happy with my 1.2-1.5 builds.
I vape mouth to lung - not interested in clouds (yet).
There is always something new to try and to learn but want to keep it in simple stages as I experiment.

One coil will heat fine but there is a significant delay in the second coil heating and the 2nd coil does not get as red as the first. This seems to be consistent over all the builds I have tried.
Is this normal?

Probably.
Depends on the meaning of 'significant'.

Also on some, but not all, build tries the first coil does not heat from the center out but from one end of the coil to the other. What causes this? I do not have this issue on a single coil build.

Check if it's from the positive side; the negative legs have more heatsink. The positive post is insulated from the deck, so that side tends to get hotter.

 

[westhc]

edyle, thanks for the reply.
Since this is my first dual coil build attempt I may be a bit slow on the uptake.

One coil will heat fine but there is a significant (2 seconds on a cold coil) delay in the second coil heating and the 2nd coil does not (ever) get as red as the first. This seems to be consistent over all the builds I have tried.
Is this normal?

Also on some, but not all, build tries the first coil does not heat from the center out but from one end (from the round post) of the coil to the other (square post with the notch at the bottom). Which is the positive post, which is the negative?

Took a closer look at the deck.
The left square post has an L extension and is raised from the deck with what looks like silicone gaskets between it and the deck. So this is the positive post?
If so, then on some builds the coil heats from the negative post to the positive.
What causes this.

 

[edyle]

edyle, thanks for the reply.
Since this is my first dual coil build attempt I may be a bit slow on the uptake.

One coil will heat fine but there is a significant (2 seconds on a cold coil) delay in the second coil heating and the 2nd coil does not (ever) get as red as the first. This seems to be consistent over all the builds I have tried.
Is this normal?

Also on some, but not all, build tries the first coil does not heat from the center out but from one end (from the round post) of the coil to the other (square post with the notch at the bottom). Which is the positive post, which is the negative?
View attachment 542449

2 seconds sounds like a lot to me, but then again I mostly do single coils; maybe one coil has 1 more wrap than the other.

The heating, you might want to try strumming the coil with a non-conductor, or compressing with ceramic tweezers; oh;;;; and one trick is to double back the leg so as to make it thicker and not get hot as fast as the center of the coil.
Or on that deck with dual coil instead of doubling back the legs, you just allow the excess leg from the other coil to continue through the posthole and remain in contact with the opposite coil.

 

[gpjoe]

New coils will often heat up differently. If you squeeze the coils with tweezers, it seems that they will heat slower. So, what I do is build and fire the coils, and squeeze both. Fire again - they should both heat from the center out at this point, if not, or if either coil is not heating evenly I will "strum" the coils with the tweezers. If one coil heats faster I will squeeze that one again to slow it down to match the other.

Also - check your screws. I have tightened mine down and fired only to find one or more of the screws loose. It happens more often than you might think. Not sure if the process of heating, or the act of squeezing the coil which tugs on the wire causes the screws to loosen, but I check them often during the build process, especially if I am having issues with the coils firing evenly.

So basically I just keep firing and squeezing til they both heat evenly and I've never had a build not work by doing this - unless I had a loose screw or coils with a different number of wraps

All of this goes out the window if you must have spaced coils, though.

 

[westhc]

I just tried another build.
Now both coils are heating equally and at the same time and from the center out.
I did not intentionally do anything different.
So I definitely have a learning curve but would really like to know what I accidentally improved on to make this set work like I expected.

This looks good enough to try wicking and vaping with.

 

[gpjoe]

Nice.

 

[rice721]

From my limited experience, make sure your screws are tightened