Central air system.. venting?

Hi,

I have a house with central air system (for heat, air conditioning, and air filter/circulation fan)… in room I have the air pushing ducts, and I also have the grids where the air is supposed to return… So could I vent directly in those grids so it goes in my central filter ?

Trying to find what is the best way to use my glowforge during winters…

Thanks

I’m not a HVAC guy, but that sounds like a really bad idea.

Why not vent outside, make a little something for the window and put a blast gate in?

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You would need a good dust collector and the activated charcoal to get the fumes. I have a similar system but the dust loads the filters much faster than otherwise I( have a washable prefilter for just that reason ) and the charcoal filter also has a maximum capacity. If that was overwhelmed your house would smell like what you were cutting forever. Even if it was hickory that would get old after a while, much less if leather.

If you can vent outside, that would be best.

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Also no HVAC expert, but HVAC systems are usually self-contained. Anything not caught by your AC filter is inside your house and I’m not sure the filters are designed for the type of stuff GF churns out. [Edited to add that even people with dedicated filters are changing those very frequently with GF use. Could get very pricey and dirty very fast, even if it works.]

Make a window insert. I’ve got casement windows, so I just close them when I’m not 'forging. But there are a number of examples around here of the inserts people have made for regular window panes, even in colder climates.

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Glowforge support will not be able to give you any recommendations beyond what they suggest in the Setup and Safety sections here, and you probably should read them before deciding what to do:

Smoke and Fume Safety

Exhaust Setup

Then check out the Beyond the Manual section of the forum for some of the solutions that other people have used in cold climates. They can vary from super simple to fairly complex, but there are a lot of people up north who run the machines all winter long. (With proper exhaust venting to the outdoors.)

Or hire an expert. Or consider adding a filter. :slightly_smiling_face:

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No, you should not vent into your home HVAC system. It is not designed to eliminate the particles and fumes produced by this machine.

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I will hop on the bandwagon of folks that are politely encouraging you to NOT do that.

I get your reasoning, but it’s very unsafe and it won’t accomplish what you are hoping it will.

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Circulating combustion products throughout your home (and heating system) seems less than optimal. Furnace filters will not catch but a small fraction of that needed to make the exhaust safe.

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not to mention the HVAC vents in your house may be under negative pressure, but there’s no guarantee t here aren’t some leaks. pinhole leaks with hot or cold air are minor annoyances. pinhole leaks when venting laser cut fumes can get nasty.

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Just reiterating, the furnace filter is designed and engineered to capture household dust, not the extreme particulate and fume the laser generates. In the event you have a HEPA filter ($) you are going to face load that filter within hours - and still stink up the house.

Even if it’s a hassle, (was for most of us) if there is any possibility of venting outside, the effort will quickly pay you back in not having to continually replace the filter element$ in even a dedicated fume extractor.

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Most HVAC systems are “closed”, specifically designed so that it neither draws in air from the outside or pushes inside air to the outside when it’s in operation. The “air balance” is said to be “zero” ideally.

The HVAC returns do not exhaust outside of the house, they go through a filter and are recirculated back in to the house. That filter will do nothing for the smoke generated by a GF. If you plumbed the exhaust of your GF to the returns of your HVAC the outcome will be fairly suboptimal (under emphasizing the degree of suboptimality). All this will do is distribute the smoke evenly throughout the house.

No. You want to totally ignore your HVAC system and duct the GF out the window and run it normally. The GF will pump inside air to the outside to remove the smoke, and replacement air will leak in around doors and windows and wall outlets and bathroom ceiling fans and a myriad of other places.

Now, depending on how well the air balance is within the house, running the HVAC at the same time as the GF may reduce the efficiency of the GF exhaust system. You may have noticed that the HVAC outlets and returns aren’t always the same size. This can result in some pressure differentials in different areas of the house, for example a closed room with a larger outlet than a return (or no return) would run at higher pressure than one that had a smaller outlet and a larger return (or no outlet, only return). If your GF is in this second room and the HVAC is running, the GF will have to fight that pressure differential to pump smoke out, it’ll be like the fan isn’t running as fast. The GF is not 100% smoke leak-free even in the best of conditions, and this situation will increase the leak rate to possibly unacceptable levels.

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It is possible to give the exhaust an extra kick with one of these…

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Yeah. I have one like that. I think it’s 210 or 230CFM. I looked for the highest flow rate I could find in a 4" size. But I couldn’t tell you where I found it. Did it make a difference? Definitely. But the seal on all my ducting was not as good as the seal at the GF. It took me a while to close off all the small leaks around the fan housing and my duct connections. So at first, it was actually worse. Now, the only time I really smell any odor is on a very long job or if I’m cutting right up at the front edge of the machine (the air assist fan manages to push a little smoke out around the gaps around the door).

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Thanks for the answers, everyone.

Your Glowforge is designed to operate with the included exhaust hose connected to the outside with a maximum of two 90 degree bends or to your Compact Filter with a maximum of three 90 degree bends. If you configure your exhaust differently, the Glowforge unit may not be able to expel enough air, and it could cause smoke and fumes to enter the room. Because ventilation is complex and poor ventilation could cause smelly and even dangerous results, we can’t advise on exhaust configurations other than what’s described in the Glowforge Manual at https://glowforge.com/manual.

Regardless of how you configure your exhaust, please follow these instructions from the user manual to avoid a serious safety hazard: “There may be some odor present while printing. However, if you detect a strong, sharp smell that also causes eyes, nose, or throat irritation, or if there is visible smoke escaping while the lid is closed, stop immediately and re-check your exhaust setup. If the irritation and/or smoke emissions do not abate, discontinue using your Glowforge and contact support.”

I’m going to close this thread. As @jules mentioned, check out the Beyond the Manual section for some of the solutions other customers have come up with.