OT: Dry heat

[Franklin]

I once called a diesel heater builder to ask the price of his heater ($2,300) and he mentioned that it produces "Dry heat". I didn't know there is such a thing...after all, the heat doesn't put water in the air (see note below). I was on a boat recently that when the boat's 110 volt reverse cycle heater ran, the hatches were soaked during the night on the inside. Shortly later the heater stopped working so I used a little 110 volt pluggin heater and the boat was all dry on the inside. How could that be? What is the difference between the two heaters that causes this "Dry heat"?Note: I fully understand that the boat is supposed to have condinsation when it is warmer then the outside and it's humid. These different heaters though seem to point to something that dries out the air.I know this isn't about Heads but thought you (Peggy) might know.

 

[Mike]

Heating methods

All heaters remove moisture from the air, some more than others. It varies based on the method of heating the air. Electric seems to dry the air the most, radiant the least. It depends on what method is being used to heat the air. Any system that passes forced air directly over the heat element has a tendency to dry the air the most. A system that heats a chamber then passes the air through that chamber drys it out less. Radiant heaters dont pass air through at all. They just radiate the surrounding air and generally leave more moisture or humidity in it. A wood fire also radiates heat but tends to dry the air out more. I suspect the diesel heater was an open flame radiant type that most likely would produce a fairly dry heat.As far as the condensation is concerned you would certainly expect some as humans radiate moist heat. Based on the size of the boat, the temperature both inside and outside, the number of people inside and how well ventilated the space is you'll get varying degrees of condensation.I hope this helps.

 

[Ross]

There are two measures of humidity

relative and absolute. Absolute humidity measures the grams of water vapor per unit volume. The relative humidity measures the dew point of the moisture vapor and compares it to the air temperature. In foggy conditions you have 100 percent relative humidity but the density of the fog is determined by the absolute humidity. In cold weather the relative humidity of the cold air can be quite high but when it is brought into a warm room and heated the absolute humidity stays the same but the relative humidity is lowered. A cold room may feel damp because the relative humidity is high. Warming the room with electric, steam or hot water heat will lower the relative humidity but not the absolute humidity. Warming the room with a fire will pull in cold air and ventilate the room as well as warming it.Just filling a cold room with people will warm it but because people sweat it will also raise the humidity and soon it will smell like a locker room.