I'm using a $20 household fan 24/7 to ventilate a damp crawl space by sealing it against one of the crawl space vent (i.e. becomes an exhaust fan).
Eventually this fan is going to fail, perhaps the bearings wear out and then the fan stop spinning.
Should I worry about a fire, or do all UL listed fan have some sort of overheat protection?
Is there some sort of fan that is designed to run 24/7 and is well protected against overheating?
Commercial ventilating fans, try
Will the UL not tell you if you ask? If not, you could ask the local fire brigade or Bureau of Standards fire research experts.
I read of household fans being a fire hazard long time ago. Only reason I remember is because my hubby likes to leave them running, 24/7, even when the room is not occupied.
If you are planning a permanent installation, then find a fan built for the purpose that runs on a timer. Constant circ. seems a waste - just periodic to sufficiently move the air. Is the crawl space sealed up with moisture barrier?
It probably depends on the fan. Some of the newer ones I've taken apart have a thermal fuse in line with the run windings. If the fan stops for a sufficient enough period of time, the solder inside of them vaporizes off, and the fan no longer functions.
Jon
That is true and they stink for a while before the thermal blows. I have seen lots of these $20 box fans fail. They were very popular in computer rooms to fix design failures and cool "hot spots". They were generally run 24/7 and ignored until they stopped. You will get 3-4 years out of one from my experience. You can try lubing the bearings when they start binding up but that will not last long. Once those oilite bearings lose their initial load of lube, they are done.
*You need a fan that is rated for damp or wet environments and is also rated for continuous duty. The inline fans from Fantech have both of these ratings. As RBM suggested you can check Grainger for a variety of choices. You could also take a look at McMaster-Carr's website. They may have something suitable.
You are using a portable temporary fan as a permanent installation. There is definite cause for concern over the long term.
Excuse me, I couldn't help a double take when I saw: "the solder inside of them vaporizes off". This is planet Earth not Mercury. Perhaps you meant loss of lubricant?
TDD
The solder is what is inside of the thermal fuse, and when it vaporizes, the thermal fuse goes open permanently and the fan is meant to be thrown away.
My apologies for not explaining that a little better first time.
Jon
A furnace blower fan is a good choice. Get one with at least two speeds to help deal with noise/vibration issues.
That's a better explanation. The thermal fuses don't always use solder or more correctly a eutectic alloy sensitive to a particular temperature. Many thermal fuses use a set of contacts and a spring held in place by a thermoplastic resin pellet which melts at a specific temperature allowing the spring to pull the contacts apart. To vaporize even a soft metal such as solder would require extreme temperatures. You had me worried there for a minute. I could just see flaming box fans in homes around the world.
TDD
See if you can find a power strip with a 5-amp or so circuit breaker built in.
It's not just a waste of electricity and fan-life. It makes the room warmer. It's only of value when a breeze is blowing on a person and probably some animals.
- just
Well, it doesn't vaporize. The temp for that is in the thousands of degrees, I think. In a fuse that uses solder, the solder melts, at a temp a little lower than the rated temp of soldering irons. Then it falls away from the wires at either end of the fuse and doesn't connect them anymore.
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