Patterson-Kelley Thermific, Installation & Owner'S Manual

Page: 28 / 46

Thermific
®
Gas-Fired Boiler Maintenance
Page 24
7. A time delay of 10 seconds (standard) or 30 sec-
onds (depending on insurance or local code re-
quirements) occurs after the air proving switch
closes and the programmer signals a continuation
of the start sequence. During this time period the
combustion chamber is pre-purged to eliminate
any residual combustible gas or combustion prod-
ucts.
8. A 10-second "trial-for-ignition" period is initiated
with both Terminals 10 and 8 being energized.
Terminal 10 of the programmer powers the igni-
tion transformer and the "Ignite" indicator. The
transformer output creates a spark at the igniter.
Terminal 8 powers the pilot gas valve and the in-
dicator for "Pilot".
9. When a pilot flame is detected by the UV scanner,
a signal is sent to Terminal F in the programmer
and a red "Flame" indicator is illuminated on the
control panel. Terminal 10 is de-energized shut-
ting off the spark ignition and the pilot remains on
for 10 seconds during the pilot flame establishing
period.
10. After the pilot flame establishing period, Terminal
9 is energized, which opens both main gas valves
and lights the "Main Gas" indicator. After 10 sec-
onds, Terminal 8 is de-energized and the pilot
valve and indicator light are extinguished. Lo-Hi-
Lo: When Terminal 9 is energized, the Lo-Hi-Lo
valve will be maintained in the low fire position
for "low fire start" for ten seconds. If the operat-
ing temperature control calls for high fire, the pro-
grammer will initiate high fire (Terminal 21) at the
same time the pilot valve and indicator is de-
energized.
11. When the desired water temperature is reached,
the operating control switch opens and the pro-
grammer is de-energized at Terminal 6 and the in-
dicator for "Heat" is turned off. This action also
de-energizes Terminal 9, thus closing both main
gas valves and turning off the indicator for "Main
Gas".
12. When the water temperature is reduced by the load
on the system, the operating control switch will
close again. The operating sequence will recycle
to step 5, provided that the limits on water flow,
gas pressure, and high temperature are all met.
5.6 T
ROUBLESHOOTING
Loss of Power
In the event of a power failure (or when the On/Off
switch is in the Off position), the "Power" indicator or
amber switch is not illuminated and the entire system
is de-energized, closing all automatic valves and halt-
ing all boiler operations. When power is restored the
sequence of operation will resume at Step 5, provided
that all the limits are satisfied.
Loss of Water Flow
When the "Low Water" or "Water Flow" indicator is
illuminated, there is insufficient water flow to close
the switch, and burner operation is interrupted. When
water flow is re-established, the sequence returns to
Step 5, provided that the other limits are satisfied.
Low Gas Pressure
When the "Low Gas" or "Gas Press" indicator is illu-
minated, there is (or has been) insufficient gas pressure
available for safe and proper operation of the boiler,
and power to the programmer is interrupted. If a gas-
supply shut-off valve is closed for any reason, a low
gas condition will result.
When gas pressure is restored, the "Low Gas" or "Gas
Press" indicator will remain on and the boiler will re-
main locked out until the low gas pressure switch is
manually reset.
On certain boilers equipped with a high gas pressure
switch, the "Low Gas" or "Gas Press" indicator may
also be illuminated to indicate high gas pressure.
Once the switch is reset, the sequence returns to Step
5, provided that the other limits are satisfied.
High Water Temperature
When the boiler water has exceeded both the operating
and high-limit temperature; power to the programmer
is interrupted. When the water temperature falls below
the high-limit temperature, the boiler will remain
locked out until the switch is manually reset. Once the
switch is reset, the sequence returns to Step 5 to await
heat demand below the operating temperature, pro-
vided that the other limits are satisfied.