A week or two ago, I set out to get my 20 lb propane tank filled. I took it to our local "Southern States" to this, as usual.
We had a hard time getting it to take the liquified gas, until I discovered that the Weber grill adapter (quick connect fitting) wasn't screwed in tight enough.
Well I was chatting with the ole guy while it was filling, and he ended up stuffing around 4.6 gallons in that tank. Now 20 lb tanks are only suppose to be filled to 3.4 gallons when they are totally empty. No big deal I thought.
Later on, either that night or the next, I hooked up the newly filled tank as the other tank was getting low. Things were going fine initially until I noticed the temperature dropping. I looked at the tank and the regulator and the hose line were totally frosted over. The main gas valve on the grill was also stiff with cold. Ultimately the flame did go out.
That extra LP in the tank caused such a big pressure differential that there was an enormous temperature drop. I wish I had a non-contact IR thermometer to measure how cold that regulator got. Ambient temperature was about 60-70 deg. F, and the relative humidity was down in the 30% range. It was so cold and iced over that touching it would stick your skin to it. Who says propane doesn't make a good refrigerant.
Anyway, to be able to use the grill, I've had to keep dowsing the regulator with water to keep it thawed out. I've had to do this for several weeks now in order to use the grill. The last couple of times it hasn't been icing up very much, and last night it didn't ice up at all (higher ambient temp probably helped too). So I think I've finally run enough gas out of the bottle. Moral of the story: don't talk to the fill-up guy, or use charcoal.