HVAC ducts? or just dump?

[kevenc]

I have yet to introduce myself. I love garages, mainly because I get to work in them. I work with metal, wood, cars, etc. I like welding, cutting shaping, and any kind of fabrication/modification.

I have a small attached garage (about 550 sqft), which hasn't housed cars for years because all the above means I love tools, and my garage is very cluttered with tools of all kinds, which is good and bad. I actually have a lot of organization, but am still working on decluttering. Right now though, I have a different question.

I live in Houston, Texas, which means I don't normally have trouble with heating, but sometimes in the winter it is pretty "cold" (to me) here. It also means my house is poorly insulated, and my garage is not insulated at all, but does have drywall, so there's some insulation in the air space.

I inherited a nice 1.5 ton split system (standard inside air handler and outside A/C unit) HVAC, and I want to install it in my garage. I know it's way overkill for this garage. Someday I hope to have it installed in my dream garage (1200sqft) that I may build on some property north of town when we move there, but for now, I'll have to settle for what I have.

I've done some of this kind of work before, and I'll leave the pipe brazing and charging of the freon to the A/C guy, but the rest I'll do.

My main question is this: should I put in ducts, or just dump the outlet to the middle of the garage? I'm not sure it matters that much since my garage is so small, does it? It was in a garage previously, and had three ducts, which worked well. I could do the same thing, but I'm not sure it's worth the trouble.

My secondary question is about filtering. I would like to use the unit as a filtering system too. Sometimes I cut wood/whatever and the fine dust is a problem. This unit would easily filter the air quickly, but I need to know what kind of filtering system is best. I may just look up what carpenters use for dust filtering, but if someone has some experience there, I'd love to hear it.

I'm looking forward to talking with others who love garages as much as I do!

 

[12ozd]

I had 8 ducts ran in my ceiling when I built mine.
Flex ducts off of main flex.
Never been happy since it was installed.
Last weekend, I removed the main trunk feeder line and "dumped" it through the wall.
Heat works great now! (would expect the same results w/ a/c this summer)

Then again I think my ducting was to restrictive when installed.

 

[kevenc]

Thanks for that reply, that's just the kind of experience I was looking for. My blower is supposed to handle 800-1200 cfm, so that's a lot of airflow for only the three ducts it had previously. I bet it was pretty restrictive, but it's so oversized that it may not have mattered.

I think I'd have to install about 8 ducts in mine, but I can tell you that's not likely. I have too much stuff in my garage attic for that to be practical. The ducts would take up a significant portion of my attic.

One possibility is just dump it into the air space in the ceiling between the joists and seal it, then open the ceiling drywall with squares every so many feet. Then I get a "duct" that doesn't take up any room, and does spread out the cooling/heating somewhat. That sounds like a good idea on paper...

It won't run very often, so I'm not too concerned with operating costs.

 

[pseudorealityx]

A) 1.5 tons = ~600 cfm. Not 800-1200 cfm.

B) Dumping is fine for a 550 sq ft garage.

C) If you're doing real woodworking, You would want to fab up some sort of extra spiffy filter box section, because a standard HVAC filter isn't what you need or want.

D) Don't dump it above the ceiling. Too much heat up there that you'll kill all your cooling capacity before it ever gets into your garage.

E) Once you get it operating, don't do something silly like set the thermostat at 68. You'll run into humidity problems in a heartbeat.

 

[12ozd]

E) Once you get it operating, don't do something silly like set the thermostat at 68. You'll run into humidity problems in a heartbeat.

I agree w/ everything you posted.
Explain that one (E) please.
I'm not understanding it.
Thanks.

 

[kevenc]

My air handler is rated at 2 tons actually, so the installer wanted to go for extra efficiency I guess. It's rated at 800-1200 cfm, depending on the restrictions.

Yes, I assumed I'd have to go with the spiffy filter box. I think that's a good idea as long as I don't end up with an $80 filter I have to change too often.

Humidity problems? In the summer? This poor thing is going to be dripping all the time it's on. Conditions here are typically 90% humidity all summer long, but I'm not quite sure I understand what humidity problems you're talking about.

You may be right about not dumping it into the joists. There is a lot of heat up there. I guess I could insulate it with foam board, but since none of this has to be final until I like it, I might as well try dumping it first. I can always go back and do something fancier later if I don't like it. Two of you have said dumping is O.K. so that sounds like I'm not off my rocker for thinking it should work.

Thanks for the reply!

 

[EOC_Jason]

I would just dump it, here is a picture of a setup we have in one of our warehouses.

I wouldn't rely on it for filtering the air if you are doing a lot of woodworking, the filter will clog up quickly and what does get through will coat the entire inside of your coil & furnace and make a mess. I would highly recommend using some quality pleated filters and also get some of that filter media that they use for paint booths, that will increase the filtering ability and capacity. I would also over-size the filter grills since it's going to be sucking a lot of dirty air.

 

[kevenc]

Clarification: 1.5 Ton outside unit, 2 Ton air handler

 

[kevenc]

Ooh, I like that setup. That's nice. I may do that in my dream garage!

As far as the filtering, I was thinking of a nice 2" pleated filter like this:
https://www.grainger.com/product/AIR-HANDLER-Std-Cap-Pleated-Filter-2W231?functionCode=P2IDP2PCP

With a 2" polyester prefilter like this:
https://www.grainger.com/product/AIR-HANDLER-Filter-Media-Pad-5W102?functionCode=P2IDP2PCP

But I haven't done much research into it yet.

BTW, nice vise! I just got my 16 year old son a beautiful 1915 Reed 3C (IIRC). He loves it, and I do too. I'm jealous now, my 1995 Craftsman pales by comparison!

 

[volleyball]

The furnace filter is to help keep the furnace clean, not to clean your air.
Plan on a separate filter.
You said 550sq ft is that a square garage or long and narrow? If it is long you'll need ducts. round steel are the best.

 

[kevenc]

It's a square garage, with one little side cubby, so I think it'll be O.k. in that respect.

I'm looking into filters now. The magic is the media, and I'm not quite sure where to get it. I have the luxury of making the plenum box any size I want, so the area could be really large, but I need good media.

Thanks!

 

[Zeke]

Large would be good for the prefilter. I would look into reusable filters and even prefilters for the prefilter. I would also look into a dedicated dust collection and filtering system. If you're going to do wood working in a closed area, this is for your health.

 

[kevenc]

I actually have a dust collector (well, most of the parts of one anyway), but just have no room to install it right now. I will do that when I move into my dream garage, but I don't do enough woodworking now to really need it most of the time.

Right now I'm just going after the low hanging fruit, which can be part of my install of this system. A pre-pre filter might be a possibility though.

 

[volleyball]

Make a filter box with a 50 cent filter, followed by a merv 5 and then or not a merv 10 filter. Go big on cross area.
the cheap filter will take the brunt

 

[EOC_Jason]

You can try contacting Air Filter Systems in Cypress, TX...

http://www.afshouston.com/

We purchase all our air filters from them for our rental offices. I bet they will have something that will work for ya.

 

[Jamie V]

Flex ducts off of main flex.

Then again I think my ducting was to restrictive when installed.

Flex duct ***** so bad but it's used all the time!

 

[kevenc]

Looks like the commercial woodworkers dust filter is something like this: https://www.grainger.com/product/AIR-HANDLER-Pocket-Air-Filter-2JRX9

I could easily use this and a cheap pleated pre-filter. MERV 14 should do it!

Thanks guys! Your help has been very helpful. I'm excited about being a part of this list!

 

[kevenc]

That AFS place is within walking distance to my house! That's amazing. I may have to call them up. You must live around me?

Thanks!

 

[EOC_Jason]

I'm over in Spring, not too far away from you.

 

[pseudorealityx]

I agree w/ everything you posted.
Explain that one (E) please.
I'm not understanding it.
Thanks.

The best you're going to get out of a standard split is ~54/55 degree air, with coil temps a bit lower than that. As that discharge air heats up to 68 degrees, without adding any moisture, you have 60+% RH.

Have to look at a psychrometric chart to see it.

 

[pseudorealityx]

My air handler is rated at 2 tons actually, so the installer wanted to go for extra efficiency I guess. It's rated at 800-1200 cfm, depending on the restrictions.

Yes, I assumed I'd have to go with the spiffy filter box. I think that's a good idea as long as I don't end up with an $80 filter I have to change too often.

Humidity problems? In the summer? This poor thing is going to be dripping all the time it's on. Conditions here are typically 90% humidity all summer long, but I'm not quite sure I understand what humidity problems you're talking about.

You may be right about not dumping it into the joists. There is a lot of heat up there. I guess I could insulate it with foam board, but since none of this has to be final until I like it, I might as well try dumping it first. I can always go back and do something fancier later if I don't like it. Two of you have said dumping is O.K. so that sounds like I'm not off my rocker for thinking it should work.

Thanks for the reply!

You do not have 90% RH all during the summer. More like ~50% during most of the summer. At the extremes, you'll close in on 90%, but it's not many hours.

And with 1.5 tons, it's only going to be dripping when it's actually running, which may not be that often. And because you're locating it in a hot attic space, you'll get less condensate because you won't be able to keep the coil temps down as well.

 

[kevenc]

The local weather people say 90% humidity, but I guess that's peak, because last year I got a humidity meter, which ranged from about 45%-66% depending on the time of day, much higher in the mornings.

Yes, of course it will only drip when it's running, which will usually be in the evening hours. It's in an insulated air handler, which should help the coil temps.