Listed below are possible causes for carbon monoxide escaping from the efm unit and not being vented safely to the outside of the house. It is not intended to replace a qualified technician's inspection, nor can it be considered a comprehensive list of any and all causes.
1. Improper draft.
A. Caused by a blockage in the chimney or ash build-up in the flue pipe, especially in an elbow.
B. Caused by weather conditions in a chimney which normally has poor draft in good conditions. The efm unit requires a
draft of negative .02 at the fire door port, located in the "e" of efm, which will usually result in a negative .04-.05 at
the rear flue port, which is a hole drilled mid-point in the flue pipe after the breach and before the draft regulator.
Measurements are taken using a draft meter or manometer after the stoker has been firing for about 10 minutes and
the unit and chimney are fully warmed up. The draft regulator weight is adjusted to achieve this proper negative draft
and proper draft cannot be established without a measuring device. It is possible that there will be a slight positive
draft until the unit is warmed up. A negative draft will draw in smoke through the fire door port while a positive draft
will force smoke away from the fire door. If there is a positive draft at the fire door and a negative draft at the
flue pipe, there could be a blockage inside the unit. Tjerlund makes a continuous draft inducer to help solve a
poor chimney draft situation.
C. Can also be caused by remodeling or sealing off air infiltration into the boiler space, preventing enough air supply for
2. Leaking joints in the flue pipes.
3. Missing rope gaskets around the iron fire door, the ash pit door, or under the bin pipe collar, which bolts to the boiler's
jacket and prevents gas from escaping around the coal pipe where it exits the jacket.
4. Lack of boiler putty around all the joints in the boiler base. The entire perimeter between the boiler and base must be
sealed, as well as the outside edges of the three plates that bolt to the base.
5. Rust in the base from a wet/damp basement which has resulted in holes in the base. There cannot be any unsealed
holes in the base.
6. Using too short of a coal pipe between the stoker and the coal bin. Some owners will use a 55 gallon drum and the short
burner worm because of space considerations. While this has often been successful and there have been no problems
with carbon monoxide, it is not recommended by efm. The long length of pipe, about 8 feet in total, is designed to
hinder carbon monoxide from being forced down the pipe and into the coal bin. Some owners have overcome a CO
problem with the short pipe by putting a sealed lid on the 55 gallon drum; again, not recommended by efm.
7. Improperly installed burner end pipe. This pipe has a series of holes drilled into the end of the pipe which enters the
pot. The holes MUST face upward when placing the new pipe into the pot. This allows any CO in the pipe to be safely
vented back into the pot.
8. A fire that is burning too low in the pot. This can occur when using a new supply of coal of unknown quality or because
of an improperly adjusted coal feed and air ratio. If the coal burns faster than the old supply and the feed and air
setting aren't adjusted accordingly, the coal will burn up faster and the fire will burn down into the bottom of the pot.
If the feed rate isn't increased, the fire can burn down into the auger and the blower air will begin forcing CO backwards
into the coal bin, especially one with a short coal worm. If you suspect that a new supply of coal is of lesser quality than
a previous supply, the coal feed rate of the stoker should immediately be increased and the air setting adjusted to
achieve a cooler center of the pot fire and the desired 2 inches of ash ring around the perimeter of the burner holder
at the top of the burner plates. There should be no live coals in the 2 inch ash ring, however, some unburned coal
specks are acceptable. A good starting point for a stoker boiler is 5 teeth of coal feed and 4 1/2 air. Adjust from
there to achieve a good burn. If the ash ring isn't wide enough, slightly increase the air setting Anytime a new supply
of coal is used, the pot fire should be checked to see if any adjustments are necessary to the feed or air settings.
Not related to CO problems, a fire that burns too low in the pot can, in very rare instances, also melt the burner pipe
and worm as the fire works its way towards the coal bin. The burner-end pipe should never be extremely hot outside of
the jacket. If you notice this, the coal feed and air settings must be reset immediately.