Wall mount electric heater air flow

Hi Pondman,

I would have thought it would be safer to have the heating element at the top and the fan at the bottom with the air flowing upward. The reasoning behind this is that normal convection works in this direction so you wont be fighting nature. Configured like this the fan will be protected from the heat of the element in the event of a fan failure thus minimizing the risk of a fire. Finally when the unit is turned off there is still a certain amount of heat stored in the element which will naturally rise so if the fan is above the element it will be heated by this and may be damaged or in extreme situations catch fire.

From what I see there are some fairly powerful safety reasons to have the fan below the element and it is certainly the way I would mount it.

Is the unit installed upside down and the fan reconnected to run in the wrong direction or remounted to blow out instead of in?

As masu said it should have fan below heater and forcing cold air upward over heater coils to blow the hot air outward.

In the U.S., this heater would have to be approved by U.L. in order to be installed. It would have been tested as an assembly and if approved or passed, it would operate safely. My question would be, is it a propeller fan or squirrel cage fan. Its possible that a squirrel cage fan motor would be in a separate compartment, out of the heated air stream. A "pull through" configuration would provide better air distribution across the heater element than a "blow through" configuration.

Also, with the high temperature electrical insulations that are now available to insulate the motor windings, it would not be unreasonable to design the heater with the fan motor exactly where it is located. These little induction motors are very rugged.

You indicated that the entering air was 50 d F and leaving air was 72 d F, that is a 22 d F rise in temperature. If your romm were already at 75, the discharge air would be pretty close to 97 d F....Not too bad!

Pondman,

The heater coil vs fan position has been well covered, and while in general the fan is located on the cool side, in the end it depends on the particulars of your unit.

As to your comment:

"Pretty hard to heat a 10' X 12' room"

While the directional air moving characteristics of the heater can affect perceived comfort, and "evenness" of heat distribution, both horizontally and vertically, the overall average temperature rise in the room will be unaffected. The size of the heating element in watts is the only determining factor, not fan placement. If the heater wattage is insufficient for the room, no change in fan or element location will alter that fact.

Regards, Greg

Thank you all for your comments- I knew that I could count on the group for worthwhile input- the safety aspect is definitely one that I had overlooked. Your time to respond is very appreciated.

"the air going in the bottom is 50 degree and coming out at 72- Pretty hard to heat a 10' X 12' room"----Pondman: A 22 degree rise in the temperature of the airflow is significant. If the airflow is adequate, it wil heat the room and, as the room (intake) temperature rises, so will the outlet air temperature.DickL

I think i have the same type of heater, and the same thing ocurred to me. These actually work very well once they get going. The temperature increase does not seem that great, but note that the volume of air that is heated is much greater than a smaller heater. So if you are heating 350 cubic feet of air 20 degrees each minute it adds up quicker than a heater which heats a higher temperature but much smaller volume. I took mine apart and cleaned out the dust, added a few drops of oil in the bearings of the fan motor.

What do the OEM's instructions say?

Pondman,

Dickl hit it right on the head. A 22Deg differential is adequate to to heat (or cool) a room. If you would have been talking about a heat pump that number would be great.

The voltage is irrelevant. The proper wattage is whats required to heat your space with a forced air unit. Providing you have the correct "R" factor of insulation for your climate, there's be a mathematical formula based on your cubic space. Forgive me for not providing you with the formula, I seem to have misplaced one of my books.