Ive been building my dream garage for about a year now. A few months ago we installed the heater. It is a natural gas Procomp 30000btu heater, and it works well. A few days ago I was working in the garage and I noticed a small puddle of water on the concrete floor, right under the fuse box. You could see a water mark on the sheetrock under the box, where a stream of water ran down to the floor. I removed the cover to find a lot of water in my fuse box. There was condensation on the back of the box, on the busses and there was water dripping off of the wires that comes out of the standoff. This dripping water was pooling up on top of the breakers.
The box is mounted on an exterior wall, with no insulation between the box and the exterior plywood. The garage is well insulated, and finished with drywall throughout. The heater is a natural gas (blue flame) ventless heater and the owners manual does say it can produce a little bit of water, but that it should just form a puddle under the heater. The outside air temperature was 10f inside 63f. The stand off goes up through the roof and does include a weather head.
Not sure what other details you guys would need to know. Feel free to ask.
Thanks in advance!