Opinons...what's The Optimal Shop Humidity?

Treetop I did some checking and there is a lot of complaining about current dehumidifiers failing after 1-2 years. As I have no real choice I purchased a $269 unit vs the cheapest I guess we'll see how long it lasts.
 
Getting some heat in there would be a big help to keep the temperature reasonably stable. I think temperature swings are worse than the humidity. Freezing weather for a week, then the next day it starts raining, the temperature goes up to 50 and 100% humidity, every cold surface sweats like crazy.

It is said that a rolling stone gathers no moss, that does not apply to the PNW. Moss grows everywhere.;)
 
So far so good. Humidity was about 72% this evening and I let it run for 4 hours, humidity dropped to 58% and it sucked about 1 gallon of water out of the air. This unit is quiet even on high, not whisper quite but maybe 65 decibels, just an air whooshing sound the compressor when it comes on is pretty quiet. This model has a pump and a 16 foot hose so I could just plum it over to the shop sink but for now I'm using the bucket.

Trivia - this model can also be set to heat the shop up to 86 degrees, I'm guessing it works like a heat pump. I may give that a try this winter.



I decided to test the moisture in my air supply, which the amount of condensation collecting when running the Accu-Lube started this whole humidity management effort. Previously I just had a 50 foot line from the compressor to my mobile air station. I swapped that out and installed 200 feet of air line to give the air time to cool and for the moisture to condensate. I also installed another filter to try to capture most of the moisture before it even gets to my mobile air station. At 58% humidity and about 56 degrees in the shop I emptied the 20 gallon compressor about 1.5 times and not a single drop of moisture collected in the filter.
 
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Living in Adelaide South Australia we have a fairly dry climate, winters are cool and damp, and summer is hot and dry. Humidity is rarely a problem Although with the last few years of global warming or climate change, whatever you prefer to call it, the humidity levels have begun to rise. We normally use evaporative coolers for air con in summer, I think you guys in the states call them swampys. As I understand it, it's not the humidity per se, but the dew point.

If the metal surface temperature, or any surface, drops below the dew point then you will get condensation. Dehumidifiers will certainly help control the problem, but a decent reverse cycle air con will also work, some even have a dehumidify setting. A dehumidifier is really only an air con with a slightly different setting.

The problem is that after cooling the air to get the moisture out, it is often too cold so you need to reheat it for comfort this can be arrange by running the air over the condenser coils, so there is no extra power required for the reheating.

Large commercial units are often set up that way especially in humid climates.
 
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Here in Seattle, a basement is OK for metals with a dehumidifier set for 50%. That's partly
because, even unheated, a basement doesn't get much temperature fluctuation.

A 20 degree temperature drop from 70 degrees F to 50 degrees F with
no change in ABSOLUTE humidity changes the RELATIVE humidity
from 50% to 100%. To put it another way,
if your relative humidity reading isn't near 100%, you don't expect rust. But
it isn't enough to dehumidify, if your temperature swings faster (a half day?)
than the dehumidifier cycles the total air volume in the shop.

So, insulation and air circulation are as important as dehumidification.
Heating is important, too, because few dehumidifiers (none that I've had) are
operable below some critical temperature (55 degrees?) because they freeze
instead of liquefying the moisture, and it never drains.

Dehumidifiers that fill a bucket, can do it every couple of days. They
must be tended, and monitored. The electric bill can be substantial.
 
I purchased a de-humidifier this evening. Fact is I had issues with surface rust on my lathe last winter. My 3 car garage gets almost no sun, a couple hours late in the afternoon at most. I already have moss issues on the garage roof and its only 3 years old. That's also the wet side of the property. The mill was $6k plus so I'm going to do what I can to protect that investment. This should also help with my shop air moisture issue. The question is once I get the moisture level down how long will it last before the unit has to turn back on. The garage is sealed pretty well for a garage I guess, and its insulated.


How long the low humidity will last once you get it down to an acceptable level? It depends on many variables, basically how does new moisture get into your shop, does your shop have a good vapor barrier, how much fresh air is circulated into the shop from outside, are there any open water containers in the shop, even a dripping tap into a hand basin will be a source of moisture as it evaporates in the now dry air. What is the ambient temperature in your shop. If the temp is below comfort level try running some heat that in itself will reduce the relative humidity. conversely if it's above comfort level run some air con that will also reduce the relative humidity.
 
"Rust only forms when conditions are right – when there is enough water and air. Iron will rust when the relative humidity in the air climbs above 50%, and steel rusts when the relative humidity reaches 80%. If your shop is unheated, iron and steel tools will also rust when the nights are cooler than the days. At dawn, the temperature of the air rises faster than dense solids and moisture condenses on the cool metal surfaces. One way to prevent rust is to change the shop environment – either heat the shop to keep the tools surfaces warm or install a dehumidifier to remove the humidity from the air."

Source:
http://workshopcompanion.com/Demos/...lassroom_files/Shop_Notes_Rust_Prevention.pdf
http://workshopcompanion.com/Demos/...lassroom_files/Shop_Notes_Rust_Prevention.pdf
 
Currently 25% in my house and I consider that sort of humid.. Rust? whats that?:)
 
An old thread, but I noticed that my metal toolbox in the garage will condense when it gets hot after being cold. Everything is coated with condensation even inside it.
My wood tool box insulates everything from the condensation taking place. So in that respect, I understand why wood boxes can be an advantage, especially in an unconditioned env.
I also understand why I see so many toolboxes rusted at garage and estate sales.

My wood and metal shops are in the basement. I let in a small amount of air conditioning in the summer from upstairs to keep the humidity down. I tried a de-humidifier but it gets too hot, then I would have to open windows, and that makes it more humid.. So I try to keep it shut. Only in the spring and fall do I get a chance to open it up. I have a full set of gauges so I know what's up with the humidity...
For very important expensive tools, I keep kitty litter in a small tin to soak up any moisture in the drawer just in case. I learned that from a Wood working magazine. It works. I also save tons of packets of desiccate.
I keep my machines oiled, My WW machines waxed.
That's the best I can do.
 
" ...my metal toolbox in the garage will condense when it gets hot after being cold."

Actually, one finds condensation with a cold toolbox (or machine) and warm humid air.... IOW, it sweats like a cold drink bottle......
 
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