A dehumidifier will add MORE heat than a electric resistance heater
with the same power consumption.
It's obvious that all watts consumed by the dehumidifier will stay in
the garage as heat. What is not so obvious is that when water vapor
condenses into a liquid it gives up heat (just the opposite of what
happens when it evaporates). There is also the heat pump effect of
removing heat energy from the cold condensate if it is piped down
Yawp. *lots* of heat.
Approximately 970 BTUs _per_pound_ of water condensed. That's enough
heat to raise the temperature of 10 lbs of water by nearly 100 F.
Or, 8,200 BTUs per gallon of condensate.
For the metric crowd, 540 calories per gram. Enough to raise 10 grams
of water by 54 C.
The effect of this is _trivial_ in comparison to the condensation.
If the water is at 20F below 'room temperature', that's a whopping
TWENTY BTUs per pound of water that goes down the drain. About 1/5
of 1% of the energy released by condensation. Hardly worth mentioning. :)
The metric crowd uses joules, not calories (1 cal = 4.184 J). See the
official SI website:
The heat energy in metric terms is 2,260 J/kg (also 2,260 J/L). The
energy from condensing a cupful would illuminate a lightbulb for 9
You might want to try a small dehumidifier, running it for a few hours during
heating and after...then shut it down and empty it until the next time.
"Character is much easier kept than recovered." Thomas Paine
The propane burner requires about 10 cuft air for each 1000 btu
generated. Each 10 cuft of air burned generates about 1.6 cuft of
water vapor. That's a LOT of water.
To prevent moisture buildup in the room you must get rid of the water
generated by providing an easy exit for it; the exhaust gases from the
burner should go out a stack & not directly into the room.
Also try spraying a thin coating of a non-wetting agent like a
silicone onto the cold cast iron surfaces. That will slow down the
condensation of the water.
How much water is in the water vapor? I'm not doubing the statistics, but
you are saying that 10 cu. ft of air reduces to 16% of vapor by volume.
What else is included here in the 1.6 cubic feet? That means that the
original atmosphere contain 16 percent vapor, but that must be reduced to a
given amount of liquid. How do we calculate the liquid content?
The answer to your last question is "absolute humidity". the math gets
somewhat messy. Google for a write-up. :)
Air consists partly of oxygen. the oxygen is the only part that is
involved in combustion.
The amount of oxygen in 10 cu. ft. of air will combine with a 'fuel' to
"make" about 1.6 cu. ft. of water vapor.
If you want to go through the actual numbers --
You start with the percentage of 'air' that is oxygen. the oxygen
molecule ("O2") has a molecular weight of 32 (roughly). thus 22.4 liters
of O2 will weight 32 grams.
Propane (C3H8, molecular weight 32) provides the hydrogen.
1 C3H8 + 5 O2 => 3 CO2 + 4 H20 +
CO2 weighs in at 40, and H20 at 18
In gaseous form (at standard temperature and pressure), 22.4 liters of
-anything- weighs, in grams, what the molecular weight of an individual
Have fun with the math. <grin>
One lb of propane, when burned, generates about 2-1/4 lbs of water. or about
35 fl. oz.
Even a 4 watt bulb will heat the iron to a slightly higher temperature
than the garage itself. It doesn't matter if the temperature is 80 or
minus 10. All you want is a slightly higher temperature on the
rust-prone area to chase away the moisture.
I fI had a garage shop, I'd spend the money on lots of insulation and
caulking. I know its tough to seal a garage door, but it can be done.
You already know about thick castings and increased humidity and stuff. Now
think about a fan. I've had a cheap box fan running 24/7 in my shop,
moving the air around, since last fall. High humidity, low humidity, high
temperatures (up to 120 F inside the shop) and low (down somewhere below
10) I haven't had anything rust except for stuff that's been kept out of
the moving airstream.
Granted, I don't have any big iron in my shop, but I'm still impressed with
the efficacy of this inexpensive prophylactic. I used to have to wax
*everything* frequently. Every chisel, every screwdriver, every saw
blade... Rust was a severe problem.
Michael McIntyre ---- Silvan < firstname.lastname@example.org>
Linux fanatic, and certified Geek; registered Linux user #243621
A classmate of mine told me that soaking small rusted items (drill,
mortising bits) in coca cola for about 2 weeks will break the rust free. I
haven't tried it yet. I did acquire about $1,500 worth of tools for $200
last summer from a former workmate who was liquidating his father's old
tools. Many of the small drill bits and metal parts of the larger tools had
rust. We tried navel jelly with no success. Some parts are too small use
steel wool. any suggestions?
Sure, try the Coke on the small parts. It is acid and will break down the
Wood magazine just had an article about rust removal and prevention. Worth a
A fan might not be the sole solution in every climate, but it can be a big
part of the solution in many. It's just too simple, and cheap, a solution
for most folks to take seriously ... until they try it.
Other than the occasional coat of Topcote, a fan running 24/7 is the only
rust prevention solution I need. I've been in this particular shop, in a
high humidity, rapid change in temperature climate, for over two years. Fan,
mounted high on one wall and blowing across shop, runs 24/7, NO rust on any
tool surface whatsoever.
Just cleaned rust off the tools, for the third time, in a shop for a lady
friend who no longer has a husband. She has the shop and tools rented out,
but the lessee has yet to take possession. The shop is less than two miles
from mine (and drier overall because mine gets water in around the edges
when it rains heavily), and her cast iron surfaces rust constantly ...
difference between her shop and mine: NO fan.
I was having the same problem - to the point where I would clean and wax
them and a few days later it would warm up and rust would form.
It happened one day and I noticed I corner of hardbard was over the TS - I
moved it and there was no rust under it - the rest of the TS top had rust
all over it.
So I tried a little experiment - I cleaned both my jointer and TS - I took a
peice of HB cut it to the lenght of one of the jointer beds. About a week
later - it got down to about 25 then warmed to about 60 the next day.
Again - the TS and jointer were showing signs of rust (despite the wax i did
the otherday) - I moved the HB and it was still sparking clean. Now I have
3 peices of HB - 1 to fit onthe TS and 2 for the jointer. All marked - DO
NOT USE OR THROW AWAY.
Been using this for about 2 months now w/ great success. I just have to
remember that when im done for the day - to put them back on!
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