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Old December 8, 2018, 01:53 PM   #1
TXAZ
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Gun Safe heater rods vs. Dessicant

Any preferences on the gun safe plug in heater rods? How do you like them if you have one?

Also, how do you pick the size of heater rod?

Anyone prefer desiccants (bags of silica gel that absorbs moisture)?
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Old December 8, 2018, 02:12 PM   #2
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The rods work great... Just check them when you're in the safe one on a while.

Mine has been going strong for 5 years now, still warm every time a check it.
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Old December 8, 2018, 02:25 PM   #3
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Passive is better than active.

While rare, a heating rod gone bad can start a fire (called an arching ground fault that does not rise the current to the point of tripping the CB unless its on a GFI circuit.

Desiccant packs are cheap from McMaster or Grainger and last forever (and now power use)
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Old December 8, 2018, 02:33 PM   #4
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Both work well.

As usual, there are always trade-offs. I have been using a hot-rod for a number of years and in time, they will shrink you furniture. I check to time to make sure it is still warm but has decade some. So far so good ……

The desiccants packs or containers have to be monitored as well but can be easily regenerated. If used correctly, they will last you a long time and initial cost is low. At any rate, I suggest the use of a humidity monitor, in addition to the ones that sometimes come with the packs. You don't have to worry about a power source and can be placed anywhere in you safe. ….

Be Safe !!!
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Old December 8, 2018, 03:28 PM   #5
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I use three of the plug in rechargeable small dehumidifiers along with the silica gel packets that one finds in their furniture boxes, tv boxesor online. I have two safes in very damp locations andit keeps both bone dry. My other safe and firearms in the upstairs closet also need oil or a dehumidifier in their safe, closets get pretty damp unless there is air flow, I had a ton of surface rust on a shipment of mags and a few rifles I had left in there without oiling and it got pretty bad.

Those rods and fans are a great idea if your safe is in your basement or you live near a wetlands or possibly if you're in a humid climate. I'll probably install one in my "tier one platforms" safe.
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Old December 8, 2018, 03:51 PM   #6
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I think you really need to look at what each does. Then based on individual situation make a choice and move on the decision.

Using a Golden Rod for example will warm the sir in the safe a few degrees and least we forget the placement is important. You want it low so convection happens where the air is heated rises, then slowly cools falling to the bottom and rising again so we get some airflow. Heaters like this do not literally suck moisture out of the surrounding air like for example a dehumidifier would. The size is based on the volume of the safe and generally chosen from a chart. I am not going to get into the physics of the slightly heated air resulting in a lower humidity. They work fine and last a long time.

I use desiccant as in my area and environment that works fine for me. I also had an endless supply of the stuff. Desiccant is a hygroscopic substance which means it does suck in water from the air around it. I also use little humidity indicator cards and a few times a year bake out my desiccant bags:



I also make sure that every now and then I check what is going on inside my safe:


Wow, just noticed the recorded temperature and humidity was a two year old sample.

In conclusion depending on your environment determine what is a good choice for you. Just make sure every now and then you look in on what is going on in your safe.

Ron
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Old December 8, 2018, 05:13 PM   #7
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Quote:
Originally Posted by Pahoo View Post
As usual, there are always trade-offs. I have been using a hot-rod for a number of years and in time, they will shrink you furniture.
“They will shrink your furniture “?

How much / over what amount of time?
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Old December 8, 2018, 07:33 PM   #8
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A long time and not documented

Quote:
How much / over what amount of time?
The only documentation I have is after a number years, The bands on some of my rifles, became loose. It has never been a major problem and just rotated the rifles that were closer to the rod. I don't see it as a big problem but others might. Keep in mind that you are taking a rifle from an ambient environment, into a drier enclosure. I have never encountered a rusting problem not even under my steel but plates. ……

Be Safe !!!
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Old December 8, 2018, 08:13 PM   #9
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Anyone heard of a "Peet Dryer"?
It's a little more expensive but the claim is by lightly circulating the air it's a more consistent temperature and humidity in the safe.
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Old Yesterday, 12:00 PM   #10
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Quote:
As usual, there are always trade-offs. I have been using a hot-rod for a number of years and in time, they will shrink you furniture
I only use desicant in my safe. I have had furniture shrink after several years. It doesn't matter what system you use, if it changes the humidity the wood will change as well. The most notable change for me was a Win 94 that spent no time in the field over several years. When I pulled it out to show a friend, the stock was loose and every screw in the wood was loose.
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Old Yesterday, 12:28 PM   #11
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I use a Golden Rod AND 3 large passive desiccant packs (live in humid Florida) they all work just fine.
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Old Yesterday, 05:18 PM   #12
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TXAZ,

Ideally, you would use something the Munter's type dehumidifier, but the heaters are way easier and less power hungry. Forced circulation is superior, as wet air is less dense than dry air, so it tends to float up away from the heater. The opposing influence is that warmer air rises, so heat increases circulation right up until the air has cooled to where its density equals that of the cooler wet air, and then, as it cools further, it starts to fall. So the two effects fight each other and forced circulation prevents creating an air ceiling in which circulation is only part way up the safe before the air starts to return to the bottom. It doesn't take much, though. Think, ceiling fan on low rather than a high-speed blower.

I have got good circulation by mounting a small-ish DC computer fan on legs where the mounting holes are, so it stands horizontal, then running it off a DC wall wart at half its rated voltage or less. Most such fans have switched DC motors that don't mind running that way, and that will start and run with as little as 1/3 rated voltage in some instances. At half voltage, you get 1/4 the power moving air, but at that lower speed the noise is negligible, and the bearings last indefinitely, and dust doesn't build up on the blades much in a closed space. The fan I linked to would add about half a watt to your heater load.
Desiccants pull more water from air faster when they've recently been "recharged" (maybe it should be called 'discharging,' as the effect of the heating them is to drive water out). In a sealed area, the relative humidity limit desiccants allow increases as they fill with water and there is less remaining capacity to attract and hold water.

The same thing happens with air. Dry air is a desiccant, too, and the closer air is to having all the water it can dissolve, the higher the relative humidity is. This is true by definition, as relative humidity is just the percent of the air's capacity to dissolve water that has been used up. The warmer air is, the more water weight it can attract and dissolve, which is why heating it lowers relative humidity.

The advantage of using air as a desiccant is you effectively "charge" it continuously with the heater. As long as the heater has more power than you need, you can control the humidity of the heater's effect with a humidistat, but you can't do that with the desiccant unless you open and close a sealed opening to it. A desiccant can over-dry wood, as described, and even cause cracks if it goes too far. The general rule of thumb is that wood will change length along the grain about 1% for every 4% change in moisture content. At an RH of about 80% or below, the water content of the wood, allowed to equilibrate in that RH (and this happens through finishes, albeit more gradually than for bare wood) is to multiply RH times 0.186. So, if you want to limit wood length change to 1%, don't change the RH more than 5.4%.

How much should you actually reduce humidity? For wood size, you would like it to be as little as possible. For corrosion protection, you want the opposite. This page, when you scroll down, the second illustration is a graph of the change in the air corrosion rate of steel vs. RH. At 60% RH, the rate is about 18 times slower than it is in 80% RH. Indeed, there is a very sharp knee there, and the rate drops off much more slowly after that. At 40% RH, it is extremely hard to get any air rusting and at 30% and below, it is essentially impossible.

But 30% RH can split stocks and the like. I think 60%, therefore, makes the obvious target value to shoot for (but any amount helps). This calculator will help you figure out what you need, ideally. To use it, put in your temperature on the top argument space and RH on the bottom one, and click on "Calculate." It will figure out the dew point temperature for the amount of water in the air. Next, click to clear temperature at the top and the RH at the bottom. Put 60 in at the bottom for your desired RH and the top will display the temperature you need to raise the safe to on the inside to get it down to 60%.

For example:

I clicked on the button to use the Fahrenheit temperature scale at the top left. I put in 70°F degrees at the top and 80% RH at the bottom, leaving the dew point temperature blank, and then clicked on calculate. It came up with a dewpoint of 63.55°F. Then I clicked on the button to the right of both the 70°F temperature I'd put in at the top and the 80% RH at the bottom to clear them. I then typed in the desired 60% RH at the bottom and clicked on calculate. It tells me I need to raise the inside temperature to 78.59°F, or 8.59°F to get down to the 60% RH I want. So I need a heater big enough to do that.

If I substitute an ambient temperature of 90°F and go through the process again, I find I have to raise the temperature by 9.33°F to get RH down to 60% inside. Given the amount of required temperature gain goes up with the ambient temperature, you really want to make the calculation for your worst case high outside temeprature so you are covered.
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