TM 10-4520-263-12&P
0003 00
SPACE HEATER SMALL (SHS)
THEORY OF OPERATION
0003 00-1
The Space Heater Small (SHS) operates independently of outside equipment on a regularly maintained
supply of liquid fuel. Combustion gases are exhausted out the roof of the shelter through the stack
assembly.
The heater has variable heat output, and can be controlled by the operator. During operation, heat output
is controlled with the burner rate control.
During normal operation, and with proper burn rate control, the heater will produce an even, yellow-colored
flame. The SHS will not emit smoke or other combustion gases into the space being heated. Proper
safety precautions should be maintained in the area surrounding the heater as the entire unit will be hot
during operation.
The SHS requires minimal maintenance; refer to the Preventive Maintenance Checks and Services as
detailed in work package 0010 for more information.
An operational cycle for the Space Heater Small (1) begins when the air vent/primer port cap (2) is
temporarily removed and the primer bulb (3) used to extract a small amount of fuel from the fuel tank (4).
This priming fuel is then injected into the burner shell (5) through the sight glass opening (6) on the lid
assembly (7).
The fuel shut-off valve (8) is placed in the ON position and the air vent (9) located on the air vent/primer
port cap (2) is opened two or three turns.
Liquid fuel flows from the fuel tank (4) through the fuel quick disconnect (10) and fuel strainer (11) to the
regulating float valve (12). The regulating float valve (12) controls the amount of fuel that flows to the
burner (5) via a gravity feed concept. As the height of the regulating float valve (12) is raised or lowered
using the burner rate control (13), the amount of fuel delivered to the burner is increased or decreased
respectively. Fuel then flows into the burner up-tube (14) inside the burner shell (5).
A burning piece of fuel-dampened tissue is dropped to the bottom of the burner shell (5) through the sight
glass opening (6) on the lid assembly (7). The burning tissue then ignites the priming fuel. After five to ten
minutes, enough heat is produced by the burning priming fuel to vaporize fuel within the up-tube (14).
Fuel vapors are generated and discharged into the downtube (15), where it enters the burner shell (5),
mixes with air, beginning the combustion process. By the time all the priming fuel is consumed, the
combustion process has been established and will continue as long as there is fuel in the fuel tank (4) or
the fuel shut-off valve (8) remains in the ON position.
Air, required for combustion, is drawn through the bottom of the heater and into the burner shell (5). The
lid assembly (7) is secured to the heater body by latches (16). This prevents air leakage which would
impair operating efficiency while the heater is in use.
The flame can be monitored through the sight glass (17) on the lid assembly (7). Combustion gases pass
from the burner shell (5) through the heater body and up through the stack assembly (18), and outside the
shelter through the rain cap (19).
Once combustion is established, heat output inside the tent is controlled by rotating the burner rate control
(13) up or down. An indicator scale (20) labeled from 1 to 10 indicates the current position of the
regulating float valve (12).
