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Forum topic by Walnut_Weasel posted 09-12-2010 02:35 AM 1075 views 0 times favorited 9 replies Add to Favorites Watch
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Walnut_Weasel

360 posts in 1941 days


09-12-2010 02:35 AM

Topic tags/keywords: humidity

I do a lot of my handtool work indoors in one of our spare rooms. I have recently purchased a temperature and humidity gauge and the humidity has been running between 45-60% even with the A/C on. What humidity do you guys in the midwest have indoors? This would explain why I am constantly battling rust on my planes even when they are waxed. I does anyone have a recommendation for a dehumidifier?

-- James - www.walnutweasel.wordpress.com


9 replies so far

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Tom Coster

120 posts in 1557 days


#1 posted 09-12-2010 04:46 AM

Walnut,
I’m in the same boat as you. I’m in South Carolina coast. August humidity runs in the high 90’s outdoors. I keep my garage shop a/c on dehumidify mode and the temp set at 78 unless I’m actually in there working, then I knock it down to 72 to 74 degrees. My humidity runs 55 to 60 and I still have to watch out for surface rust. During the winter I run a separate dehumidifier to keep the moisture down.

-- Tom, MI, SC

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closetguy

744 posts in 2611 days


#2 posted 09-12-2010 06:12 AM

With my air conditioner running, my shop will maintain 45% here in Georgia when it’s about 90% outside. If the overhead door is open a few times during the day, it will hit 55-60%, but drop quickly once they are closed again. I don’t run a dehumidifier.

-- I don't make mistakes, only design changes....www.dgmwoodworks.com

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Tom Coster

120 posts in 1557 days


#3 posted 09-12-2010 10:49 PM

My garage shop has no insulation.

-- Tom, MI, SC

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8iowa

1489 posts in 2480 days


#4 posted 09-12-2010 11:33 PM

There is no “ideal” humidity. Temperature and humidity ane not seperate entities that can be independently adjusted. The term “relative humidity means that the amount of moisture in the air is relative to it’s temperature.

For example, cold air holds much less moisture than warm air. If you compare air at 10 degrees F with air at 90 degrees F, even if the relative humidity is the same, the amount of moisture in the air can be much greater at 90 degrees. That’s why it is called “relative humidity”

In our basement this Spring, when the cold air from outside was heated to 70 degrees F by our furnace, the humidity inside dropped to 50%, even though the relative humidity of the cold air outside was in the 70’s. Later in the summer, when the outside air was 70+ degrees, I had to run a dehumidifer in order to drop the humidity down to 67%. I was emptying a gallon of water a day even though the relative humidity of the outside air was only 7-8% higher.

It’s not going to be practical, and certainly not economical to take hot Summer air and attempt to reduce the humidity to 50%. You just can’t separate humidity from it’s relative link to temperature.

-- "Heaven is North of the Bridge"

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Rick

6751 posts in 1752 days


#5 posted 09-13-2010 08:17 AM

In the Summer in the Toronto Canada area I set my Air Conditioner to 72/73 Degrees. It keeps the Indoor Humidity at a Very Comfortable 50 to 52%.

Even if it’s in the Low 70’s outside, windows open, the Humidity is sometimes Higher than I prefer (60% or so, inside & outside) so I close all the windows, drop the AC to one degree lower than it’s reading and within an hour or so it’s down to 50/52 inside.

In the Winter I HAVE to use a Furnace Mounted Humidifier to keep the Humidity at a comfortable level. I’ve never had to use a Dehumidifier, Summer Or Winter.

-- If there was any Logic in this world .... it would be Men riding Side Saddle, Not Women!

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Tom Coster

120 posts in 1557 days


#6 posted 09-14-2010 03:58 PM

8IOWA I see the wisdom of what you are saying. I am certainly not an expert on this subject. I am on the coastal plains of South Carolina. An area that many decades ago was one big cypress swamp. Today it is basically a half drained swamp. Here you have to lower the humidity by any means possible. During the summer a ten point change in temp can equate to at least a 20 point change in humidity. That may not seem like much but in August it can feel like you are breathing under water. And bare metal will rust badly over night. Even in the winter months I must run a dehumidifier occasionally, about two days a week, in my un-insulated garage shop.

-- Tom, MI, SC

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8iowa

1489 posts in 2480 days


#7 posted 09-14-2010 09:02 PM

Tom:

I’m trying to make the point that there is no magic control panel in which you can independently set temperature and humidity. Also, it is wrong to think that a humidity of 50% is the same for air say at 32 degrees as opposed to 90 degrees. There is a world of difference because the 90 degree air can hold a whole lot more moisture.

In fact, using a dehumidifier in the shop during a hot humid summer will be doing well to reduce the humidity by 10% in respect to the outside air. In your case, with an uninsulated shop, you could run the heart out of a dehumidifier and only the electric company would be happy.

I insulated my shop (garage) here in Gainesville, where it is pretty hot and humid in the summer. The thru the wall A/C unit is set at 80 degrees and I’m certain that I’m only reducing the humidity 6 – 8% relative to the outside temperature, yet this seems to do a pretty good job of keeping the rust gremlin at bay.

-- "Heaven is North of the Bridge"

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Camper

232 posts in 1575 days


#8 posted 09-16-2010 03:30 AM

I am not an expert on this either, but my understanding is that if you have a “larger” A/C unit ,it cools your house faster down to the thermostat setting and stops and does not remove as much humidity as would a “smaller” unit which takes longer to cool your house but removes more humidity. Sizing AC units is actually a fairly complex process based on the size of the windows you have, volume of your house etc…it is difficult (maybe impossible) to draw a simple correlation between humidity and temperature given outside conditions without knowing a lot more information regarding the structure(the house) as well as the AC unit specifications. 2 cents

-- Tampa-FL

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Tom Coster

120 posts in 1557 days


#9 posted 09-16-2010 07:56 PM

8iwoa, I understand the gist of what you are saying. My problem is wrapping my head around how the heat makes it feel different. Today, in the Myrtle Beach the high is 86 degrees with only fifty percent humidity. (It feels a lot worst! I guess I shouldn’t complain as the humidity breaks into the 90’s in August.) I keep my shop at 50 % humidity, the same as it is outdoors today. But it is a lot dryer in my shop. You can literally feel the difference. And see the difference in lack of rust on bare metal. I run a 220 volt window unit that I cut into the wall. This unit has a dehumidifier setting. On this setting it does a better job of removing moisture than normal a/c mode but the machine does cycle on more often. Still cheaper than running a 110 volt dehumidifier. Not sure why. I set it at78 to 80 when I’m not there and down to 72 when working in the shop. I keep two barometers in the shop that read about 20 points apart but change consistently together. One is new (cheap) and one is a least sixty years old. I’m betting the old one is reading correctly. With this set up I can keep the humidity down around 50 on the older gauge. But it has to be watched carefully. If I don’t work in the shop at least once a week and not lower the a/c temp for around ten hours the humidity will climb.

-- Tom, MI, SC

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