Dehumidifier in garage

[markchamness]

I live in the San Francisco bay area and I got tired of my tools rusting.  So I installed a dehumidifier in my garage.  It quickly lowered the humidity from 80+ % to 60% overnight.  But it's taking a few days to get below 50%.  I suspect that the concrete floor is releasing moisture into the air.  Should I seal the floor?

 

[tbellemare]

Mark:

Do you have a pool?

Tom

 

[peter halle]

As a long time user of dehumidifiers - I use one year round inside my house - I have some decent size aquariums that evaporate at the five gallons of water a day - I will offer some of miy observations.

1.  It sounds like you have digital display.  They are famous for not being accurate.
2.  Size matters
3.  Everything porous in your garage has absorbed moisture and will be leaching it back into the air.  It may take a long time to lower further from the plateau you are on.
4.  Keeping the filter clean - if yours has one greatly affects the performance.

You didn't mention if you open and close the garage doors - as in actually allow your vehicles to share space with your tools.  If so, each time you open you are letting moister air in and the dehumidifier has to work

My advice would be to give it a few weeks.  Then put a reasonably large piece of poly down on the floor and tape the edges.  Wait a couple of days.  remove the poly and see how much moisture has accumulated underneath.  If you have a significant amount, seal your floor.  If not - you have saved yourself the hassle and don't worry about it.

Just my 5 gallons worth,

Peter

 

[BMH]

Mark,

What type of dehumidifier are you using. I am thinking of installing one in my garage, I live in Oregon.

Bruce

 

[whk]

I have applied water based epoxy and a urethane coating to my garage floor, and I am very satisfied with the results. For a successful installation, they emphasize careful preparation, in particular the garage floor needs to pass a moisture test.  The test is just as mentioned above, cover the floor with plastic and see if any condensation shows up.

So, you've got a classic Catch 22 situation.  The same test that tells you that you have a moisture problem also tells you that the solution probably won't hold up.

Will

 

[tbellemare]

The reason I asked about the pool is because a friend of mine who lives here, so the climate is the same, has had a real bad rust problem in his garage. I don't have any problem at all.

After years and all of his tools rusting like crazy, he finally thinks he's identified the problem...
He was storing his pool chemicals, including chlorine, in his garage.

He has since moved them out but I don't know if it has solved the problem because everything is already rusty.

Tom

 

[markchamness]

No pool or pool chemicals.  (But good point.)  Another local woodworker had incredible rust issues.  He had a lab analysis done and determined it was a chemical stored in his garage.

This is the dehumidifier:
http://www.costco.com/Browse/Product.aspx?Prodid=11490527
Danby Dehumidifier model DDR2509EE. With a 25-pint capacity,

Door is always closed.  It's only a one-car garage.  There's also a washer, drying, and water-heater.

 

[jonny round boy]

I'll apologise beforehand for asking a stupid question, but is the dryer vented outside, and not just into the garage?

 

[markchamness]

The dryer is vented outside.  So is the water heater exhaust heat.

 

[richard.selwyn]

I'll apologise beforehand for asking a stupid question, but is the dryer vented outside, and not just into the garage?

Jonny your question interests me - I run a small dehumidifier permanently in my shop - which is rather stupidly located in an old water mill.  [laughing] [laughing] The water is collected in a small tank that I empty about every two days.  (We use the water in the steam iron) I don't know how dry the shop is, but it is dry enough.  I wonder if it would make much difference if the machine drained outside?  How dry should one's shop be?  I don't make fine furniture and use a lot of sheet goods, but if you made furniture in a very "dry" shop and then delivered it to a client here in Normandy with a regularly "humid" house you could have problems.

Anyone else got any knowledge or experience to share?
Richarc

 

[jonny round boy]

I'll apologise beforehand for asking a stupid question, but is the dryer vented outside, and not just into the garage?

Jonny your question interests me - I run a small dehumidifier permanently in my shop - which is rather stupidly located in an old water mill.  [laughing] [laughing] The water is collected in a small tank that I empty about every two days.  (We use the water in the steam iron) I don't know how dry the shop is, but it is dry enough.  I wonder if it would make much difference if the machine drained outside?  How dry should one's shop be?  I don't make fine furniture and use a lot of sheet goods, but if you made furniture in a very "dry" shop and then delivered it to a client here in Normandy with a regularly "humid" house you could have problems.

Anyone else got any knowledge or experience to share?
Richarc

I think you've misunderstood - If the dryer is a condensing one, ie outputs liquid water, then I doubt it would make any difference whether it collected in a tank or was drained outside. I was thinking of the older non-condensing dryers, that output warm, moist air.

I've seen quite a few cases (mainly in rented properties) where the tenants have complained about damp in the property - then it turns out that they use a non-condensing dryer in there & it isn't vented outside, and all the moisture that's drawn from the clothes simply stays in the room & settles on the walls & ceiling...

 

[prodrying]

I live in the San Francisco bay area and I got tired of my tools rusting.  So I installed a dehumidifier in my garage.  It quickly lowered the humidity from 80+ % to 60% overnight.  But it's taking a few days to get below 50%.  I suspect that the concrete floor is releasing moisture into the air.  Should I seal the floor?

There are two types of refrigerant dehumidifiers.  One is a standard unit with only one set of coils the other is a low grain refrigerant dehumidifier which passes the air over the coils twice or two different coils.  A standard unit will not get the relative humidity below 55 - 60% and it sounds like you have a standard refrigerant.  An LGR will get the humidity down to 30-32%.  So the only time your unit will go below 55-60% is when the air it is pulling in is below that.  

 

[peppapig101]

I realise that this is an old post but in my experience other people are suffering from the same problem(s).

That said I have an extensive Garage Dehumidifier Guide on my website that people ought to read.

I'm not sure if I should link to it in this post but if you are interested you know where to find my site (my profile might have something to do with it).

If you have any further questions about dehumidifiers please feel free to ask and I'd be happy to answer.

 

[mo siopa]

This is a good topic to readdress "Pippa."  Whether it is with rusting tools or finishing issues, relative humidity is a constant thorn in the side of woodworkers whether they realize it or not.  In the OP's situation, a few seconds of the garage door being open may be eliminating several hours of dehumidification.  Depending on the current and recent weather conditions, this could mean that your tools are collecting some dew while the door is open.  It could take several hours to remove the excess moisture after the garage door is closed.

 

[Steve-Rice]

I sincerely hope I don't come off as some sort of wise guy or anything, but wouldn't a simple solution be to coat all your tools with a rust preventative like Boeshield T-9 or some other wax or oil?