Can I share a dryer vent with a portable A/C unit?

Question

I want to add a portable A/C unit in our sun room which also houses our washer/dryer. Rather than vent the A/C thru a window I'd like to know if I could utilize the dryer venting by using a Y connector to combine the 2. If so, should I use a damper in one or both of the lines before the Y connector?

If you have any option at all, don't use a "portable" A/C. They're far less efficient than any alternative. I would try to look into a mini-split instead. — Matthew, Mar 23 '21 at 16:29
Or at least a 2-hose portable. With a 1-hose, it sucks hot wet air into the house.. — Harper - Reinstate Monica, Mar 23 '21 at 21:27

score 2 · Answer 1 · answered Mar 23 '21 at 16:19

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It's generally a bad idea to combine exhaust vents. You'll end up with backflow one way or the other, or you'll inadvertently block a working vent when you forget to flip a diverter or set dampers correctly. It could result in a dangerous situation with the dryer.

answered Mar 23 '21 at 16:19

isherwood

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Even if I install a damper on both the dryer and A/C exhaust and locate them before it reaches the Y connector? – Bob Mar 23 '21 at 16:29
Dampers dampen, they don't seal. Also, it doesn't matter where they are if you forget to switch them. – isherwood Mar 23 '21 at 16:36
The dampers I am looking at are automatic. They open when there is air flow. For example the one on the A/C line is closed by default, but when the a/c is turned on the exhaust air will open the flange – Bob Mar 23 '21 at 17:41
By "automatic" do you mean "spring-loaded"? That's not advisable on a dryer. They tend to not open completely and reduce airflow, which can increase heat buildup. – isherwood Mar 23 '21 at 18:07
No, I have seen online a damper with no mechanical parts,,,as in not spring loaded. – Bob Mar 23 '21 at 19:44
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The only thing I can imagine you're talking about are gravity-closed flaps. Those are fine for single exhaust scenarios, but as soon as you have two machines pushing air there's a good chance that one of the flaps doesn't open due to pressure from the other, or it only opens partway. It's not a reliable strategy. You don't want dryer lint in your air conditioner. – isherwood Mar 23 '21 at 20:51
Thank you for the advise. The plan was to put a non spring loaded damper on each line (dryer & a/c) However only one appliance would be in use at a time. If we are using the dryer we'd not use the a/c. What I am trying to avoid is back-draft from the a/c running into the dryer, and vice-versa – Bob Mar 23 '21 at 21:02

score 1 · Answer 2 · answered Mar 23 '21 at 15:49

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For the exhaust that is probably a good idea as long as the dryer is not in use and the door is closed. Are you bringing in fresh air through a vent or is the house leaky enough it won’t be a problem for the supply of fresh air (any air that goes out has to be replaced).

answered Mar 23 '21 at 15:49

Ed Beal

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The sunroom is not that air tight. I just has a concern that the hot air release from the portable A/C unit might not vent to the outside properly if it shared a common exhaust line with the dryer. Also I do have some concern of lint build up if I use dampers in each line. – Bob Mar 23 '21 at 15:56
With the door closed the ac should push out fine. You would have to check with the dryer turned on to see if there was a back flow into the ac if yes a flapper vent could solve the back flow but it may already have a back flow device built in. – Ed Beal Mar 23 '21 at 16:14

score 0 · Answer 3 · answered Mar 23 '21 at 23:51

No, you can't. Why? Lint

Dryer lint, as many can attest to, is quite the combustible stuff. As a result of such concerns, as well as the significant amount of moisture found in dryer exhaust, the IRC requires that vented dryers have a dedicated vent path to the outdoors:

M1502.2 Independent exhaust systems.

Dryer exhaust systems shall be independent of all other systems and shall convey the moisture to the outdoors.

Exception: This section shall not apply to listed and labeled condensing (ductless) clothes dryers.

So, I'd get a window-type air conditioner instead of a "portable AC" at minimum. If that's an absolute non-option for some strange reason, then you'll need to use a two-hose unit to avoid the AC depressurizing the sunroom in a self-defeating fashion; keep in mind that the dryer will do that anyway when it's on, though, so not running the dryer and AC at the same time is still wise advice.

Can I share a dryer vent with a portable A/C unit?

3 Answers3

No, you can't. Why? Lint