Air Exchanger for Woodshop

[John]

I was thinking of putting an air exchanger in the woodshop to allow me
to paint in the colder months. I'm wondering if anyone has any
experience or recommendations that they'd like to share.

John

[LdB]

I have one in my house. I would not have another house without one.
That said, these are heat recovery units. They were very expensive and
I assume they still are. It will take many hours of operation for the
unit to earn it's keep. That will happen in a house, but in a workshop
probably not. You will have to put in a good air filter in front of
the exchanger or it will clog up. Factor that cost in as well. You
would probably be better off with a simple exhaust fan.

LdB

[Puckdropper at dot]

LdB <L...@nowhere.com> wrote in
news:l6adnWMOXtfrXunT...@supernews.com:

I've got a Jet air filter (not an air exchanger). One thing I've noticed
is the filter tends to get dirty really quickly. If you have anything
that does air filtering, make sure you get washable filters or you'll
spend a fortune on disposable.

I haven't tried it yet, but there's an adjustable charcoal filter
available that should absorb odors. It might be good for finishing work
in the shop.

Puckdropper

[Mike Marlow]

I'll second that. I paint all year long and I am in a cold winter climate
(Central NY). If I'm painting a car in the winter, I crank up the furnace
to a comfortable temperature, and I put a 24" box fan under one of the
garage bay doors, and seal the opening off with plastic. Yup - I blow warm
air outside, for sure. It's not as noticible as one might think though.
The garage keeps a steady temperature suitable for painting and I've never
had any problems that were related to temperature, or the fan being stuck
under the door as described. The small amount of extra propane that I use
this way is not even worth the mention. It's not like things stay this way
for days. Plus - no up front costs for elaborate systems that I wouldn't
use enough to get a pay back from.

--

-Mike-
mmarlo...@windstream.net

[Bill]

Mike Marlow wrote:

> I'll second that. I paint all year long and I am in a cold winter climate
> (Central NY). If I'm painting a car in the winter, I crank up the furnace
> to a comfortable temperature, and I put a 24" box fan under one of the
> garage bay doors, and seal the opening off with plastic. Yup - I blow warm
> air outside, for sure. It's not as noticible as one might think though.
> The garage keeps a steady temperature suitable for painting and I've never
> had any problems that were related to temperature, or the fan being stuck
> under the door as described. The small amount of extra propane that I use
> this way is not even worth the mention. It's not like things stay this way
> for days. Plus - no up front costs for elaborate systems that I wouldn't
> use enough to get a pay back from.
>

Makes sense to me. Thanks!

[Eric]

"John" wrote in message
news:b3ca9828-9026-4f9d...@t3g2000vbe.googlegroups.com...

================

HRV units would be plugged up severely in a few minutes of woodshop
usage. The cores would be too expensive to replace on a regular basis.

Wood dust may need to be vented but painting vapors without overspray
may work. Good prefiltering to ensure this would be a necessity.

I understand HRV units are commonly used in new home construction in
Canada. Not so common in the USA where our energy consciousness is not
as predominate.


--

Eric

[LdB]

Modern construction practices make the air to air heat exchangers
necessary. HVAC (heating, ventilation, and air conditioning).

More so for health reasons rather than heat recovery. A properly built
house is almost airtight. That's great for heating or air conditioning
bills but not for the occupants. Radon along with a multitude of
chemicals out gassing from the building contents will build up to high
levels very rapidly. They just have no way to escape the house. Even
carbon dioxide from breathing will build up if there are enough people
in the house at any time.

I built my house and can honestly say that the amount of air
infiltration through the walls and windows is so close to zero that
it is insignificant. If it wasn't for the doors opening occasionally
it would be like living inside a balloon.

By the way there is a big difference in heating costs between new and
old construction. My old 900 sq ft 1950's style bungalow cost about
30% more a year to to heat than does the new 1800 sq ft house. That
considering the new house has over three time the window area than the
old house had is quite impressive.

My air exchanger runs whenever the house is closed up. Winter heating
and on the summer days when the A/C is running.

If you live in a well sealed house anywhere you should be doing some
sort of air exchanging all the time. A few open windows is usually
good enough but few of us live in an ideal climate where we at not
either heating or cooling our homes for days on end.

LdB

[John]

Yeah, I'm looking to be able to paint in the winter in those -30C
days... Opening a window isn't an option. I also want to prevent the
paint fumes from getting outside of the woodshop by using negative
pressure (most air exchangers allow you to put the return air vent in
a different room that the exhaust). I could do this via a simple
exhaust fan, and absorb the extra heating costs. This house is 25
years old, and not completely air tight, so it would likely work.

John

[Eric]

"John" wrote in message
news:2e68d48b-1393-48d4...@p4g2000vbp.googlegroups.com...

=============

Heat exchangers typically perform by large exchange surface areas and
small spacing between. Any overspray in the fumes of paint or other
coating type substances will coat these surfaces with same and block up
the heat exchange membranes very quickly.

You will require some special commercial HRV / ERV unit to perform this
function. A residential unit will be clogged in a few spray painting
operations and quite possibly be an expensive write off. Brush painting
should work OK and should not plug up the air system.

A warm room with some good "heat inertia" and an exhaust fan, and fresh
air intake, for short durations of spray painting may work best. After
the initial fumes are removed an HRV unit may work fine for keeping
gasses to lower levels and conserving heat energy during the paint
hardening phase.

--

Eric

[whit3rd]

On Monday, September 19, 2011 7:26:52 PM UTC-7, Eric wrote:

> Heat exchangers typically perform by large exchange surface areas and
> small spacing between. Any overspray in the fumes of paint or other
> coating type substances will coat these surfaces with same and block up
> the heat exchange membranes very quickly.

By the time paint moves a few yards, it's semisolid (dust),
and a standard disposable house-ventilation filter will likely
collect it fine. If it's liquid, it'll certainly stick to a filter.
So, a stack of filters, and a little excess power to the ventilation
fan, should do the trick. When the filters get clogged (you can
use a colored-water-in-glass manometer to detect this)
just change 'em out. Such porous filters won't catch all the
fine wood dust, though.

[Eric]

"whit3rd" wrote in message
news:7086717.719.1316646852482.JavaMail.geo-discussion-forums@yqog21...

===

All that may help for occasional jobs but it doesn't in the paint shop
exhaust fan systems. Most of them have to scrape the vents and fans blades
out every year or two. I have never seen a heat exchanger used in an
industrial or commercial setting. I don't think it can be made to work
without huge maintenance. Perhaps somebody has experience in a paint shop
can comment??

If you use a paint that is dry enough to not stick to anything that fast you
will not need an exhaust then either. It should just fall to the floor.
(sarc)

--

Eric

[whit3rd]

On Thursday, September 22, 2011 10:31:35 AM UTC-7, Eric wrote:
> "whit3rd" wrote in message
> news:7086717.719.1316646852482.JavaMail.geo-discussion-forums@yqog21...

> By the time paint moves a few yards, it's semisolid (dust),
> and a standard disposable house-ventilation filter will likely
> collect it fine.

> If you use a paint that is dry enough to not stick to anything that fast you
> will not need an exhaust then either. It should just fall to the floor.

What 'fast' are we talking about? I'd do spraying in still air, and afterward
(minutes) turn on the airflow. Someplace-away-from-wind is the prime
requirement for a good spray environment, IMO.

[Mike Marlow]

whit3rd wrote:

>
> What 'fast' are we talking about? I'd do spraying in still air, and
> afterward (minutes) turn on the airflow. Someplace-away-from-wind is
> the prime requirement for a good spray environment, IMO.

Away from wind, and airflow are two different things. Having an exhaust fan
is by far, a preferred environment, over a still air environment. You're
not creating wind with an exhaust fan, you're creating an air pattern that
evacuates overspray and mist.

--

-Mike-
mmarlo...@windstream.net

[m II]

Now we have heard it all from the biggest BS expert going!

Good one Mickey! and I love your email domain too. ROFLMFAO!!!

--------------

"Mike Marlow" wrote in message
news:d0e96$4e8458ed$4b75eb81$23...@ALLTEL.NET...

Away from wind, and airflow are two different things.

--
-Mike-
mmarlo...@windstream.net

[Mike Marlow]

m II wrote:

> Now we have heard it all from the biggest BS expert going!
>
> Good one Mickey! and I love your email domain too. ROFLMFAO!!!
>

Oh look - I have my own internet stalker.

--

-Mike-
mmarlo...@windstream.net

[kayl...@aol.com]

Hi John,
I was considering just such a unit for my Laser Engraver, as it produces
some pretty nasty exhaust gases when working on certain materials. It was
going to double for exchange of air in my wood-shop as well. After talking
to a few engineer friends, and shopping around for the needed blowers,
filters, Frame materials and fabrication, sheet materials and fabrication,
insulation and hardware I arrived at the conclusion that it was best to do
one of two things . . .
1) Bite the financial bullet, and pay the cost of a well designed commercial
unit. Expect it to cost about $5,000 to $10,000 depending on the size of
your shop, and add on the additional expense of pre-filter devices and
media. Don't expect it to deliver any type of super efficiency either. The
best units available don't exceed 75 - 80 percent efficiency. There will
still be substantial thermal loss when you factor in the relatively small
quantity of air to be exchanged in your type of application. This makes
sense when you are working with the potential losses in a commercial
environment, working constantly for a large space over 8 hours a day, but
the overall cost benefit would take years to recover in a small shop,
especially for infrequent use. The unit would likely rust out and need
costly replacement long before you reach the break even mark.
2) Design and build my own unit which ended up consuming a considerable
amount of space to reach the efficiency threshold that would make it cost
effective. I considered this to be above 85% efficient. It takes a long
exposure time to the opposing air flow (read long passage) and slow movement
( huge cross sectional area by creating a tall narrow cross section) to
accomplish. This type of design results in quite good efficiency, at a cost
that was very close to or exceeds that of a commercial unit, but requires a
large amount of space consumption. And don't forget that you need to bleed
off the condensate, and also keep the entire air path clear and clean of
mold, mildew and funguses too. Quite a job when you consider how large the
chambers will be on an effective unit.
Both of these options led me to one final result . . . It turns out that it
is actually cheaper and easier to just exhaust the gases to the outside,
placing properly sized vents on an upper floor, (preventing instant chilling
of the work area), and simply absorb the expense of the additional utilities
utilized by blowing the contents of the houses warm air out the blower. If
you resign yourself to this type application, you just learn to shut the
heat off for a short time while you do your work, and plan it carefully so
you don't have to chill the house for too long. It really isn't any worse
than having young kids running in and out of the house on a busy day. But it
does work best if you plan your work for times when the rest of the family
is out doing other things. You will get to do your work, they will get the
benefit of breathing in a freshly ventilated house, and nobody is going to
be too uncomfortable for too long. Plus we don't have to worry about
legionaire disease, and other such negative health effects from accidental
neglect of maintenance. The list of dangerous pathogens that thrive in these
units (all of them) is extensive! We prefer to just put up with some cold
air in the house on occasion, and so far it is working for us.
If you decide you want to build your own exchanger, I may be able to share
what I learned in greater detail, and you can make your own decision. The
design my buddies and I came up with exceeds the efficiency of commercially
available units, but it isn't going to be 100% efficient, or even close. Nor
is it going to be inexpensive to build either. You can expect to commit some
serious time to building it and maintenance is hard and time consuming.
Either way, an efficient unit is going to be a large item in your
shop/house. The air has to be filtered in both the exhaust AND the intake.
And even then the unit will need to be kept very clean in order to maintain
efficiency and health standards. That is the main advantage of the
commercial unit... most of the research has been done ahead of time by
professionals. They don't want to get sued by not telling you about the
pitfalls ahead of time.
As for the little household units . . . Don't waste your time! They will
neither serve the function you require, nor provide the level of efficiency
required for the volume of air you will need to move.
Bottom line . . . Go big, expensive and effective and safe, or just plan on
saving some serious time, money and aggravation by making due with a few
chilly Saturday mornings when the family is out and busy elsewhere.
I hope this bit of insight helps you. This is not a simple installation when
you add in the substantial requirements of woodworking/paint/finishing/smoke
etc..
Do a LOT of homework, and ask lots of questions of QUALIFIED professionals
before you jump in to this project . . . it may just save you and your
families lives.