Timpwk,
As an electronics tech I personally have found that the 12VDC Power supplies are a joke when it comes to water "resistance" and the fans are not much better as far as durability. I just bought 11 new ones this year to replace the ones that had failed over the years. It poured here off and on for a couple of weeks and in total we had 7 of the new power supplies fail. Well that was a waste of money. When I cracked them open they all had water in them. The only way that I can figure that it got in there was either through or around the low voltage connector. Therefor I figure there are only 2 options to cure that problem;
1) As soon as you get new ones run a good bead of silicone around the connector where it meets the box, with a smear around the AC blades to seal them to the case. Then take a dielectric grease and put a good coat on the 12 volt connector before you screw it together to help act as a seal.
2) Use a heavy duty 12 volt power supply that will power all of your inflatables, put it in a weather proof outdoor rated enclosure, and then build an electrical distribution system to route the power where you want it with extension cords. This will require custom made extension cords with a unique connector so you can not plug them into your 115 volt system. I would also recommend installing a watertight inline fuse holder in the cord from each inflatable. Make sure that the fuse is rated the same as or very close to the power supply that it is replacing. In other words if the power supply is a 1 amp, make sure you use a 1 amp fuse. If it is something odd like .67 amps, use the closest you can get that is slightly higher than the supplies rating. As an example I would try to find a .75 amp fuse. I believe that they make those in the old glass type AG fuses.
Personally, I am going to be working on option number 2 this year. At current I need a total of close to 30 amps at 12 volt DC. We have over 40 inflatables and most are the crappy 12 volt ones. I am therefor considering making a couple of enclosure based power supplies so that I can place them somewhat strategically around the yard and I won't have as many or near as long of extension cords for them. I am also considering taking the factory connectors from the powers supplies, making a small junction box on the end of a cord and potting it with epoxy to water proof them. Not sure that is necessary, but I am contemplating it. Marine grade adhesive line butt splices might work to splice the wires, and seal the joints. That way I can use one cord and power 3 inflatables with a small box placed in between them. The small box of course would have an inline fuse for each connector so that I could just slap the correct fuse per outlet depending on what inflatable is plugged into the outlet. Basically, I am tired of our inflatables dying because of cheap garbage power supplies that you can't get when you need them and I know how to fix the problem.
If you decide you like option number 2, but are not sure of what to do let me know and I will do what I can to help. After what I built this year, a 12 volt system to me would be cake.
Since we live in a rental with no exterior outlets I had to design a way of getting power out to the yard that was temporary. I ended up using a very heavy cable, an outdoor rated circuit breaker panel, and exterior rated outlet boxes. I took the 230 VAC from our dryer outlet, ran it out the window and around to the front of the house. There I used the circuit breaker panel to separate the 230 VAC into 4 circuits of 115 VAC at 15 amps, just like the circuit breaker panel in a normal house does and it worked great. Now here is the kicker, the dryer outlet is rated at 30 amps in this house. That gives me 60 amps of power at 115 and I used about 40 amps of it with no issues. It is going to get some modifications this year so that it is more useful, portable, and corrects a minor design flaw that I didn't think of when I built it. The problem I ran into was that with inflatables when it is windy you do not want to run them. Well I used one heavy duty switch to turn on / off all the power for both our lights and inflatables, so when it was windy I could not even turn on our lights. So I am going to redesign it and use 2 switches so that I can turn on the lights, inflatables, or both depending on time of day and weather conditions. I am also going to use a generator connector so that instead of having a very heavy (52 lbs for a 100 feet) cable permanently attached, I can disconnect it so that it is easier to store and carry. Basically minor tweaks that if I had more time to think about in advance I would have done the first time. Oh well, live and learn.
Regards,
John.