I have a slightly different take from most of the posts here.
The small home style dehumidifier I run on my boat produces a couple gallons a day of water when we are onboard in the winter plugged into shore power. It makes it so much more comfortable onboard.
Thank you for sharing your real life experience.
At this point, I am not very clear what could be the best solution in my situation? Here are few points:
1/ The ER has condensation. It is possible that it seeps over to the cabin area. I cannot tell exactly how, due to the boat's pitch, which changes as the water tank gets low (270g). The ER also has a watertight door, but there is an opening above the door, which will let outside air in. I do not know, if this can be an issue, or should I keep the door always closed and seal the opening above it? Although the ER is not heated, it is possible that the warm air comes through from the cabin area, which is on the other side of the bulkhead.
2/ I did run dehumidifiers before, but I could not see any significant change. If I cook and the windows fog up, the dehumidifier cannot clear the air enough and the moisture is there for hours even after the cooking finished. As I listed earlier, I bought a larger dehumidifier. It will be brand new and perhaps more effective. The other units are used.
3/ I do have air moving duct system installed. They are on 24/7 now, but the flow is not very strong. Steady slow air into the bilge and stronger air out from the bilge to outside. The distance between the IN and OUT point is the length of my cabin, which is about 10'. The floor covers up the bilge.
I am thinking about getting higher volume fans and see, if that makes any difference? The slow air down to the bilge collects the warm air from the salon ceiling right next to the diesel furnace. This goes to the bilge at the beginning of the cabin. The exit air is collected at the other end of my cabin directly from the bilge and pushed outside directly. So, this is a circulation there but I am not sure, if this is enough to dry the air enough in the bilge area.
4/ I also run the diesel heater more frequently. When I leave the boat, I turn it off for safety. Otherwise it is on all the time. This uses the inside air, but the exhaust pipe goes directly to the top. The open flame furnace takes the air in at the bottom from the salon.
My point is; I do have air circulation now, but I don't know if it is enough to dry the bilge. Once the new dehumidifier is in place, I will closely monitor the bilge area in question. I can live with lower temps inside the boat. I stopped using electrical heaters now. I think they did not help and more condensation was generated.
Now I put on an extra layer of clothes.... lol