SECTION ONE – Heater Design and Function
1. The TTTThhhheeeerrrrmmmmiiiissssttttoooorrrr senses the inlet water temperature.
2. If the temperature sensed is lower than that set on
the OOOOppppeeeerrrraaaattttiiiinnnngggg CCCCoooonnnnttttrrrroooollll, power is supplied to the
IIIIggggnnnniiiittttiiiioooonnnn CCCCoooonnnnttttrrrroooollll MMMMoooodddduuuulllleeee through a series of safety
interlocks (see below).
3. The W
W
W
Waaaatttteeeerrrr PPPPrrrreeeessssssssuuuurrrreeee SSSSwwwwiiiittttcccchhhh senses whether or not
there is adequate water flow through the heater.
4. The HHHHiiiigggghhhh LLLLiiiimmmmiiiitttt SSSSwwwwiiiittttcccchhhh monitors the outlet water
temperature and will open if a malfunction causes
the outlet temperature to exceed 135˚ F (57° C).
5. The AAAAuuuuttttoooommmmaaaattttiiiicccc GGGGaaaassss SSSShhhhuuuuttttooooffffffff SSSSwwwwiiiittttcccchhhh ((((AAAAGGGGSSSS)))) moni-
tors the outlet temperature from the Heat
Exchanger and will open if a malfunction causes the
water outlet temperature to exceed 140˚ F (60° C).
6. If the High Limit Switch and the Water Pressure
Switch are OK, the IIIIggggnnnniiiittttiiiioooonnnn CCCCoooonnnnttttrrrroooollll MMMMoooodddduuuulllleeee starts
the CCCCoooommmmbbbbuuuussssttttiiiioooonnnn AAAAiiiirrrr BBBBlllloooowwwweeeerrrr.
7. When the Blower comes up to speed the AAAAiiiirrrr FFFFlllloooowwww
SSSSwwwwiiiittttcccchhhh ((((AAAAFFFFSSSS)))) senses air flow across the Air
Metering Orifice.
8. If the airflow is sufficient, the AFS closes, completes
the ignition circuit, and supplies power to the
IIIIggggnnnniiiittttiiiioooonnnn CCCCoooonnnnttttrrrroooollll MMMMoooodddduuuulllleeee.
9. In 20 seconds the HHHHooootttt SSSSuuuurrrrffffaaaacccceeee IIIIggggnnnniiiitttteeeerrrr ((((HHHHSSSSIIII))))
element heats to ignition temperature. The
CCCCoooommmmbbbbiiiinnnnaaaattttiiiioooonnnn GGGGaaaassss CCCCoooonnnnttttrrrroooollll VVVVaaaallllvvvveeee then opens and
the burner flame ignites.
10. The HSI element automatically switches from igni-
tion mode to a flame sensing mode to monitor the
flame.
11. The SSSSttttaaaacccckkkk FFFFlllluuuueeee SSSSeeeennnnssssoooorrrr monitors the flue collar
temperature and will shut down the heater if the
temperature exceeds 500° F (260° C).
12. The Burner in the CCCCoooommmmbbbbuuuussssttttiiiioooonnnn CCCChhhhaaaammmmbbbbeeeerrrr fires until
the desired water temperature is reached. Once
reached, the Burner shuts off and the Blower contin-
ues to run for about 45 seconds (known as “post
purge”).
13. If the burner does not ignite in seven seconds, the
system shuts down and will not restart. The heater
must be turned off and turned back on again at the
Membrane Pad (wait about 5 seconds) before it will
start.
14. If the flame is extinguished during operation, the
CCCCoooommmmbbbbiiiinnnnaaaattttiiiioooonnnn GGGGaaaassss CCCCoooonnnnttttrrrroooollll VVVVaaaallllvvvveeee closes and the
ignition cycle reactivates.
15. If any safety interlocks open during Burner opera-
tion, the Burner immediately shuts off, but the
Blower continues to run for about 45 seconds.
1-4
PRESS
TAB
VENT
PILOT
O
F
F
OFF
O
N
ON
3
6
9 10
11
12
13
14
2
8
4
5
1
7
Electrical Flow Through the Heater
Figure 1-4: Electrical Flow
SSSSaaaaffffeeeettttyyyy PPPPrrrreeeeccccaaaauuuuttttiiiioooonnnnssss::::
Risk of electric shock, fire or explo-
sion.
Do not attempt to override any electrical safety
interlocks which have opened. Find and fix the fault
before operating the heater.
