Blowers & Fans: Hot Air Circulation
by Irwin L. Goodchild
The most common ways of heating air are by passing it by hot pipes, baseboard heaters, convectors, or so-called radiators. In each case the air being heated becomes lighter and slowly rises naturally to the ceiling.
The heated air then fills the top of a room. It does not descend to where people are until it cools and is replaced by more warmer air. As can be seen this is a slowway of moving heated air to where people are. In addition this way places the warmest air where it is most likely to lose heat through the ceiling and the surrounding upper walls.
Now, there are two ways to move the warm air at the ceiling more quickly down to where people are. One way is to have a forced hot air system and the other is to have a ceiling fan. The drawback to each of these ways is that the warmest air is still going to the ceiling first. It just does not stay there as long.
But note that there is a still better way to get the warmed air to people. That is to have a fan blow it horizontally toward the area where people are, — one to three feet above the floor. It does this most quickly and most cheaply with fan forced warm air.
Fan Forced Warm Air
There are several ways for fans to be used to blow warmed air horizontally one to three feet above the floor.
- The simplest, easiest, and cheapest would be for homeowners with forced hot air systems. They have only to buy deflectors for each of their hot air vents. The only caution is to be sure the blower system is not overloaded and for this one can check with their heater serviceman.
- The next simplest, easiest, and cheapest is to invest in fan forced portable electric heaters. The economy of purchase, installation and operation and the convenience of portability go a long way toward making up for the cost of electricity. The cautions obviously are to be sure your electric outlets will supply 1500 watts safely. Use no more than one heater per outlet. Be sure no fire hazards exist, and be sure that local regulations are met. The method does have its adherents.
- For homes using steam, hot water, or electric baseboard heaters the idea is simple. Have an electric fan blow air across, along, or through the heater when the heat comes on. The way to do it is not simple. Placing a fan at each heater is no problem. What is a problem is how to have the fan run when, and only when, the heater is on. Two methods best duplicate the advantages of fan forced portable electric heaters. One uses fan forced propane or natural gas heaters which are permanently installed along one or more walls of each room. The other method is to use electric fan forced heaters installed in or on room walls. The only change is to swap the practicality of fixed installation for the convenience of portable heaters.
- Propane or natural gas fan forced heaters have the advantages of piping in for combustion air from outside and piping the spent gases back to the outside. This eliminates outside air mixing with inside air and cooling it. It eliminates the need for a chimney and the chimney’s construction and maintenance costs. Their drawback is that their purchase and installation costs are not cheap.
- Electric fan forced wall heaters are most similar to fan forced electric portable heaters. Their purchase costs are low and their installation costs are, too. The particular economy of fan forced electric heat far outways the cost of electricity as a heat source.
- Fan forced heat is the most direct heat distribution system.
- Fan forced heat has the most positive “on” control with minimal delay in starting. In the case of electrical heat there is no significant overshooting when the thermostat calls for shut off.
- Because of A. and B. above there is no need to heat rooms not in use for it takes only minutes to make a room comfortable.
- The significance of the economy and the comfort of fan forced heat outweighs all other ways for distributing heat.
- Radiant heat has the particular advantage of warm floors but it is not a distribution system where time is important for starting – or where overheating can be stopped quickly. The amount of flooring controls these things and economy of operation can be diminished. Conduction of heat through floors and air is a limiting factor and with any significant temperature rise in a floor the heat loss to the ceiling by true radiation can become a factor.
- Plans for any new heating system should have as a priority careful attention to the amount of insulation planned for or in place already. If there is any question of what to do first, always insulate first and then install an appropriately sized heating system.
- With sufficient insulation in the walls, modem windows of modest size, and the distribution of heat by fan forced heaters there should be little concern about the former practice of having heaters placed along outer walls to limit cold drafts from these walls. This is not to say that window insulation would not be advantageous.