Sequence Of Operation; Spark Ignition Circuit - Schwank primoSchwank Installation & Owner's Manual

20. SEQUENCE OF OPERATION FOR HONEYWELL S87C DSI CONTROL
1. On a call for heat the S87C DSI Control will check for a false flame condition / short to
ground. The module will lock out if a false flame condition is present. (Reset is usually done
from the Thermostat manually).
2. Spark (30,000 volts) is generated at the spark igniter, for direct ignition of the main burner.
 The Honeywell S87C DSI control has a total 21 second trial for ignition
 For example, if it takes 7 seconds to establish ignition, then there are a total of 14
seconds remaining for ignition re-trial(s) should flame failure occur
 The control will go into lock-out once the total 21 seconds are used up
 Manual reset at the thermostat or power source is required to re-establish ignition
trial
3. Main gas control valve is powered and opens lighting off the main burner.
4. Separate flame sensor, relays the presence of burner flame back to the DSI control by a
rectified dc voltage signal. (TFI period)
5. If the flame-sense dc signal is a minimum of 1.5 µA (microamps) the gas valve remains
open, flame remains established and the DSI control discontinues the ignition spark.
6. If flame fails, the DSI will re-trial for a period up to a total of 21 seconds. Flame will be con-
firmed with a minimum signal strength of 1.5 µA microamps back to the DSI Control. Failing
this the DSI will go into the safety lockout mode and close the gas control valve. (Reset of
the control is manually done from the Thermostat or power source).
7. On a loss of power the S87 shuts the system down safely. Start up / trial for ignition is initi-
ated when power is restored.

21. SPARK IGNITION CIRCUIT

The step-up transformer in the ignition control provides spark ignition at 30,000 volts (open cir-
cuit). To check the spark ignition circuit, proceed as follows.
1 Shut off gas supply to the gas control
2 Disconnect the ignition cable at the ignition control stud terminal to isolate the circuit from
the spark igniter or igniter/sensor
3 Prepare a short jumper lead, using heavily insulated wire such as ignition cable
CAUTION In the next step, DO NOT allow fingers to touch either
the stripped end of the jumper or the stud terminal. This is a high
voltage circuit and electrical shock can result.
4 Perform this test immediately upon energizing the system before the ignition control goes
into safety lockout and interrupts the spark circuit. Touch one end of the jumper firmly to the
ignition control GND terminal. (DO NOT remove the existing ground lead.) Slowly move the
other end of the jumper wire toward the stud terminal on the ignition control to establish a
spark.
5 Pull the wire away from the stud and note the length of gap at which spark discontinues.
6 A spark length of 1/8 in. (3mm) or more indicates satisfactory voltage output. If no arc can
be established, or the maximum spark is less than 1/8 in. (3mm), and power to the ignition
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supra/primo Manual
IM091112
RD: NOV 2009
RL: 11A - BA