CFM for solder fume extractor

[matthuszagh]

I created a solder fume extractor that pulls air out my window. I used a Hakko Loc-Line kit (https://hakkousa.com/products/fume-extraction/999-205-02-loc-line-kit-with-rectangle-nozzle.html), a duct fan, a window duct connection, and ducting. I've included an image of the setup (sorry, I know it's a little difficult to see parts of it - happy to post pictures of specific things if desired). The duct fan allegedly goes up to 190 CFM and the tubing is 3" and 4" diameter. I thought 190 CFM would be plenty, judging by the CFMs of the Hakko FA-430 (https://hakkousa.com/products/fume-extraction/fa-430-with-duct-rectangular-nozzle.html#specifications) (145 CFM) and JBC fume extractor (47 CFM), but it feels pretty weak. My iron has to be quite close to the extractor nozzle for the fumes to go there. So, now I'm looking at duct fans with much higher CFMs. Has anyone else done something similar? If so, what CFM do you use? Any other thoughts? I felt around for leaks near the connections, but didn't really notice any.

[thm_w]

What is the model number of the fan? Is it adjustable in any way? Is there any restriction or filter on the window going out?

I would, if you don't need the extreme length, try to shorten up the "U" loop of your ducting a bit. Though I don't expect that to make a massive difference.
190CFM should be more than enough.

Maybe a video for comparison or something, you want the duct close to what you are soldering.

[wraper]

You need to consider static pressure spec, not only airflow. If fan cannot create decent static pressure, it won't be able to push much air through the hose even if airflow spec looks great.

[matthuszagh]

What is the model number of the fan? Is it adjustable in any way? Is there any restriction or filter on the window going out?

This is the fan I bought: https://www.amazon.com/dp/B01DXYMGOM.

There are no restrictions or filters.

I would, if you don't need the extreme length, try to shorten up the "U" loop of your ducting a bit. Though I don't expect that to make a massive difference.
190CFM should be more than enough.

Thanks, yeah I was thinking of doing this. I was also considering replacing the 3" tube between the table mount and the duct fan with the 4" tube (which I already use between the duct fan and window and can just cut in half).

Maybe a video for comparison or something, you want the duct close to what you are soldering.

Here's a link to a video: https://drive.google.com/file/d/14KPpslDBWGuwFeUQIrGubUMNN_xw4VUo/view?usp=sharing.

[matthuszagh]

You need to consider static pressure spec, on only airflow. If fan cannot create decent static pressure, it won't be able to push much air through the hose even if airflow spec looks great.

Thanks for pointing this out. Any idea what I should be targeting, or how to figure out what sort of static pressure I need?

[wraper]

I'm not an expert in that but it depends on hose diameter, length, smoothness of its walls and air flow you try to push through it. Expandable hoses like yours certainly create much more air drag than a smooth duct. Fan with higher CFM but lower static pressure spec likely will not provide any improvement and could be a downgrade actually. I meant that you should look at static pressure spec too because it's always a tradeoff between airflow, static pressure and somewhat noise when designing fan blades.

[wraper]

I thought 190 CFM would be plenty, judging by the CFMs of the Hakko FA-430 (https://hakkousa.com/products/fume-extraction/fa-430-with-duct-rectangular-nozzle.html#specifications) (145 CFM) and JBC fume extractor (47 CFM), but it feels pretty weak.

Those fume extractors likely have airflow spec with hose attached and everything else restricting the airflow. While your fan most likely has spec when totally unrestricted.

[thm_w]

This is the fan I bought: https://www.amazon.com/dp/B01DXYMGOM.

There are no restrictions or filters.

Its a proper duct fan, 60W, I would expect that to work well enough. Though they don't give a static pressure rating on amazon or their site.

The video shows normal behavior to me, its completely capturing the fumes once you have the iron ~20cm away from the inlet. You need to position the vent either very close behind what you are soldering, or vertically above what you are working on to catch the rising fumes. You could get a more powerful fan but without a lot of work the noise level would be unbearable IMO.

Look at how close they position the inlet at 00:31 in this video:

[wraper]

Its a proper duct fan, 60W, I would expect that to work well enough. Though they don't give a static pressure rating on amazon or their site.

I expect it to have shaded pole motor which have terrible ~25% efficiency. This inefficiency becomes very obvious if you look as 120/230V  AC fans like this one https://www.amazon.com/230V-Cooling-Fan-120mm-38mm/dp/B0071HDDY0 effing 20W, DC brushless fans of this style and similar airflow/static pressure spec consume only about 1/4 of that.

[wraper]

Interesting. In Amazon listing one picture shows obvious shaded pole motor, another picture shows BLDC, one that is way more fake looking.

[thm_w]

Its a proper duct fan, 60W, I would expect that to work well enough. Though they don't give a static pressure rating on amazon or their site.

I expect it to have shaded pole motor which have terrible ~25% efficiency. This inefficiency becomes very obvious if you look as 120/230V  AC fans like this one https://www.amazon.com/230V-Cooling-Fan-120mm-38mm/dp/B0071HDDY0 effing 20W, DC brushless fans of this style and similar airflow/static pressure spec consume only about 1/4 of that.

Sure, thats why its cheap. But its designed to do the job, move air through a duct with a bit of restriction.

If you want more efficiency you can get proper DC fan as you say, it looks like this is a comparable DC model: https://vivosun.com/vivosun-aerozesh-g4-inline-fan-p146097781066261532-v146123521342167154

[wraper]

If you want more efficiency you can get proper DC fan as you say, it looks like this is a comparable DC model: https://vivosun.com/vivosun-aerozesh-g4-inline-fan-p146097781066261532-v146123521342167154

Well, I was meaning that its power is worth about 15W of computer fans. So you should not expect much from it.

[matthuszagh]

I'm currently looking at:

https://acinfinity.com/hydroponics-growers/ventilation/inline-fan-systems/cloudline-a4-quiet-inline-fan-with-speed-controller-4-inch

but still waiting on the manufacturer to provide specs on CFM at different static pressure levels. But, initial thoughts/opinions on it certainly appreciated!

[wraper]

I'm currently looking at:

https://acinfinity.com/hydroponics-growers/ventilation/inline-fan-systems/cloudline-a4-quiet-inline-fan-with-speed-controller-4-inch

but still waiting on the manufacturer to provide specs on CFM at different static pressure levels. But, initial thoughts/opinions on it certainly appreciated!

Not worth it. I will be about the same and maybe even a little bit worse.

[matthuszagh]

I'm currently looking at:

https://acinfinity.com/hydroponics-growers/ventilation/inline-fan-systems/cloudline-a4-quiet-inline-fan-with-speed-controller-4-inch

but still waiting on the manufacturer to provide specs on CFM at different static pressure levels. But, initial thoughts/opinions on it certainly appreciated!

Not worth it. I will be about the same and maybe even a little bit worse.

Ok, thanks for the input. FYI, they sent me these specs for the units (attached plots). GDFP100 is the unit I was looking at. To get from Pa to inch H20 multiply by 0.004 and to get from m^3/h to CFM, multiply by 0.589. I don't have much info on static pressures and what's a good CFM at those pressures, but I figured McMaster-Carr probably sells quality products, so I compared it to this: https://www.mcmaster.com/19135K111/. That has 143 cfm @ 3/8 in. of H2O. The AC infinity unit has 135 cfm at the same pressure. If we assume the McMaster unit is good, then this unit doesn't seem so bad. But, obviously that's a big assumption since I have no idea what's "good".

If you have any ideas about things that would serve me well I'd love to hear them. I know you mentioned DC brushless motors. The AC infinity units are apparently EC motors, which from a quick search is a DC motor driven by a rectifier and filter and PWM. Is that not the sort of motor that would be good here? Thanks again for all your input.

[thm_w]

I don't really see why you are looking for fans, the existing one works fine IMO.
Unless you are absolutely OK with the noise level and don't mind it being louder, then you can get whatever reasonable quality higher CFM rated unit is out there. If you care about power efficiency then a brushless one.

Static pressure here is not a major issue, for a duct fan, as we are not running through any filters.

[wraper]

Static pressure here is not a major issue, for a duct fan, as we are not running through any filters.

It may be a surprise for you, but many fans that are optimized for airflow and low noise noise will become nearly useless if need to push air for more than a few meters through the duct. https://www.fanco.com.au/how-does-ducting-impact-fan-performance/

Ok, thanks for the input. FYI, they sent me these specs for the units (attached plots). GDFP100 is the unit I was looking at. To get from Pa to inch H20 multiply by 0.004 and to get from m^3/h to CFM, multiply by 0.589. I don't have much info on static pressures and what's a good CFM at those pressures, but I figured McMaster-Carr probably sells quality products, so I compared it to this: https://www.mcmaster.com/19135K111/. That has 143 cfm @ 3/8 in. of H2O. The AC infinity unit has 135 cfm at the same pressure. If we assume the McMaster unit is good, then this unit doesn't seem so bad. But, obviously that's a big assumption since I have no idea what's "good".

If you have any ideas about things that would serve me well I'd love to hear them. I know you mentioned DC brushless motors. The AC infinity units are apparently EC motors, which from a quick search is a DC motor driven by a rectifier and filter and PWM. Is that not the sort of motor that would be good here? Thanks again for all your input.

I see no point changing the fan for something in the same ballpark of performance. You won't see any noticeable difference from 10% improvement. You may want to look at centrifugal type duct fans for higher performance, although at a cost of a higher noise.

[thm_w]

It may be a surprise for you, but many fans will become nearly useless if need to push air for more than a few meters through the duct.

I know, but not duct fans designed to do the task. If this were the case their reviews would likely reflect that.

[matthuszagh]

I don't really see why you are looking for fans, the existing one works fine IMO.
Unless you are absolutely OK with the noise level and don't mind it being louder, then you can get whatever reasonable quality higher CFM rated unit is out there. If you care about power efficiency then a brushless one.

It's fine - it could be better. I'd be much happier if the extractor could suck up solder fumes when my iron is further away. I'd happily trade more noise for that.

The cfm spec for the JBC extractor is really low and I really wouldn't be happy with that extractor given how close the iron was to it (assuming it actually had to be that close).

Static pressure here is not a major issue, for a duct fan, as we are not running through any filters.

Yeah I suppose if static pressure is not limiting the performance and I am getting 190 cfm or close to it, then I'm looking in the wrong place. But presumably, using a lower duct size than the intended one for the fan does increase static pressure, no? I can get a fan that is both higher cfm and higher static pressure in a 6" diameter. I can do that, but then I'll need to adapt down to a lower size at some point - at the very least at the bench mount point.

[wraper]

It may be a surprise for you, but many fans will become nearly useless if need to push air for more than a few meters through the duct.

I know, but not duct fans designed to do the task. If this were the case their reviews would likely reflect that.

At this airflow, duct diameter, its length, and the fact it's not smooth it has quite significant impact on performance though.

[thm_w]

It's fine - it could be better. I'd be much happier if the extractor could suck up solder fumes when my iron is further away. I'd happily trade more noise for that.

Try one of the 400-500CFM units then. You'll have to go to 6 inch and adapt the ends as you say.
I can't focus with that much noise but maybe others can.

[pope]

I have a very similar setup/ problem. I believe the bottleneck (!) is the adaptor from 4" down to 2.5" for the loc-line. Also, mine is attached to a chimney.

Having said that, why don't you put the fan on a stool? You will get rid of at least a meter of unnecessary duct. 

[matthuszagh]

I have a very similar setup/ problem. I believe the bottleneck (!) is the adaptor from 4" down to 2.5" for the loc-line. Also, mine is attached to a chimney.

Have you experimented with fans with good CFM under higher static pressure? If so, has that helped?

Having said that, why don't you put the fan on a stool? You will get rid of at least a meter of unnecessary duct.

Yeah, good suggestion - I will. I just need to find a stool...

[pope]

I have a very similar setup/ problem. I believe the bottleneck (!) is the adaptor from 4" down to 2.5" for the loc-line. Also, mine is attached to a chimney.

Have you experimented with fans with good CFM under higher static pressure? If so, has that helped?

TBH, I have no clue what "high static pressure" is...

I use this one that supposedly is 160CFM/ 275 m3/h but I'm not extremely satisfied.

It's not very quiet either but bear in mind that a lot of the noise is actually coming from the ducting. The fan itslef is rather quiet, when nothing is connected to it.

[tatel]

Yeah I suppose if static pressure is not limiting the performance and I am getting 190 cfm or close to it, then I'm looking in the wrong place. But presumably, using a lower duct size than the intended one for the fan does increase static pressure, no? I can get a fan that is both higher cfm and higher static pressure in a 6" diameter. I can do that, but then I'll need to adapt down to a lower size at some point - at the very least at the bench mount point.

If you have more than *one* 90º bend in your duct you are destroying fan performance. And this is with some minimal radius in that bend. You have way more bending than that. Pros place a second inline fan in their ductings after the second 90º bend.

Worst bend is probably the one just after the fan, really tight one. Perhaps you should google a little bit looking for duct design documentation. Meanwhile, I suggest to you some trials with the less bend possible, and a bend radius over a foot as the bare minimum, before purchasing anything.

Edit: correction, the worst bend is probably that absolutely unnecessary 180º one near the floor before the fan. I would bet you'll get anything between threefold or tenfold performance by getting no more tan one 90º bend. It could be easily done if you think just a little bit about it.

Edit2: get rid of that blue thing, it's another big choke. Also, if that room has the door closed, not enough air will be able to enter, while you are extracting perhaps 20% of room air volume/minute (depending on room volume). That means another restriction. To get air out of the room, it has to enter that room first, otherwise, no fan can work against the negative static pressure that will be established after just a couple minutes working. A little 12V salvaged centrifugal fan can be substituted for a 90º bend with great advantage. The tighter the bend, the greater the advantage. Having greater diameter, smooth duct will certainly help. Rectangular duct is better than round. But your main sin right now is too many, too tight bends in your ducting, and probably also that blue mouth. Get rid of that and you'll see much better results ipso facto