How can I force hot air through this fireplace grate?

Question

Ok, here's the front of my fireplace (note the grates on the top and bottom):

Here's the model tag:

This fireplace came with the house and I know almost nothing about it except that the chimney was clean. We burned a cord of wood in it last year without a problem. I was less than impressed with its efficiency and I want to get more out of it this year, so I did some investigating.

Here are two shots of the back of the fireplace:

Last year, I didn't even know this line coming out of the back of the fireplace existed, but since the front of the fireplace is grated, I assumed I could use it the way a conventional fireplace insert works. After checking that the lever on the front of the fireplace (picture below) opens and closes a door behind the duct entrance to the back of the fireplace, I installed a fan on the duct line.

The problem is that when the fan is running (and I installed a serious fan at one point just to check that I was too low on CFM), I can't feel any airflow from the grates on the front of the fireplace unit.

1. Can anyone help in explaining why there's no air coming out the grates?
2. Is this not the intended use of that duct?
3. What's the easiest way to make it work the way I want it to (if possible)?
4. I tried Googling for the manufacturer's documentation but couldn't find anything. Does anyone have a line on some documentation for this unit?

**UPDATE:**I found out that the blowers made for this fireplace have been discontinued. However, I found a company that makes aftermarket blowers. They had a low-profile one that I'm going to give a shot (http://www.fireplaceblowersonline.com/lp_4500_low_profile_fireplace_blower_fan_kit-details.aspx).

Answer 1

It may be that this particular fireplace insert uses passive heating (through the upper and lower grates) to heat the room. From what I could see from your photo's is the flexible duct line in the back is how the unit acquires it's air source (that should be an intake to the unit). The lever as you described it's operation most likely is a damper which controls the amount of air fueling the burning wood. It's a shutter controlling how fast (full open) or slow (partly open) you want the fire to burn. Once the fire has consumed the fuel (wood) the smoke is expelled through the chimney. Lastly, the reason you could detect no evidence of air movement when you attached a fan to the intake vent is because the two grates at the front are not connected to that part of the fireplaces system. Or it is closed from the air intake ducting by a hatch or re-moveable plate (maybe). What I also noticed from the photo of the Model Tag, in the lower left, is that this model "may be used with a blower assembly". From what I remember about fireplace inserts is the fan is attached through a flexible duct to the lower grate on either side of the front. It forces ambient room air through the lower duct vent which is heated from the burning wood. It is expelled as warmed air from the top grate. Go to the Superior Co's site and search for accessories and blowers.

Answer 2

Best bet on the duct is that it's an outside air supply, so any air from it would go into the firebox, not out the front.

Applying fans to fuel-burning appliances in ways not intended by the manufacturer can cause problems, up to and including death by carbon monoxide, or burning down your house.