7
The flame sensing rod must be positioned as shown in Figure 3 so that the Electronic
Control will detect a proper flame.
Both the spark and flame rods are current carrying conductors and, along with their
connecting wires, must be kept free of contact with conductive metal parts of the burner. Rod
insulators and wire insulators should be clean, dry and free of cracks.
Both the spark and flame rods are made from heat resistant alloys and can be expected to
have a long service life. They should be routinely inspected, however, for corrosion or loss of
metal.
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Should replacement or service be required, valve manufacturer's instructions must be
followed as outlined in their information sheet.
Outlet pressure settings must be checked while the gas is flowing.
To adjust outlet pressure, remove the seal cap for access to the adjusting screw. Turning
the screw clockwise will increase outlet pressure, counter clockwise will decrease outlet
pressure.
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The Midco RE4400DS is supplied with two timers to provide high fire purge and low fire
start. With power applied to L1 and L2 the blower motor starts. Once the blower motor
starts the blower air switch closes. 24 Volt power is applied to the air damper actuator and
prepurge timer. The air damper actuator begins to open the air damper to provide a high fire
purge. After 45 seconds the air damper actuator begins to close. 24 Volt power is then
applied to the Honeywell S87K DSI Ignition control module. The S87K DSI Ignition control
module also provides additional prepurge for 30 seconds. Once the S87K DSI Ignition
control module completes its prepurge 24 volts is applied to the Combination gas valve and
internal ignition transformer. If flame is proven (minimum 2 DC Micro amps) the burner will
continue in the run mode. The 2 to 10 Volts DC temperature control will then begin to
modulate the air damper actuator to provide the proper combustion air for the burner. The
feedback signal from the air damper actuator will drive the spring return gas valve actuator to
provide the correct gas flow for the burner. Refer to Table 3 for the correct maximum fire
manifold pressure settings.
If the burner lights and then loses the DC micro Amp flame signal it will retry to ignite after
completing an additional prepurge cycle. If the burner fails to reignite power will need to be
turned off and reapplied after 30 seconds.
For startup information see section X.
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The S87K is a low voltage, solid state, direct spark ignition control module for gas-fired
furnaces, boilers and heating appliances. UL Listed models are only available with a pre-
purge timer. The S87K controls the gas valve, monitors the main burner flame and
generates a high voltage for spark ignition.
The S87K uses separate electrodes for spark ignition and flame sensing. Includes a 30
second (minimum) delay for use with system pre-purge.
For operation characteristics, maintenance, and service procedures, refer to
manufacturer's literature provided with burner, or contact your Honeywell dealer.
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Startup instruction for RE 4400DS HTD
1. Set the operating control to off or thermostat below room temperature.
2. Turn manual gas cock on.
3. Turn burner power on.
4. Set operating control to ON or thermostat to call for heat. Wait 75 seconds, if the
burner has failed to light, or if burner lights then goes out, the system will go into
safety lockout. De-energize the system by setting operating control to off or
thermostat below room temperature for at least 30 seconds to reset the system.
Repeat step 4 for restart.
5.
The Belimo Actuator controls the firing rate of the burner by providing a signal to
terminal 3 on the actuator. The actuator has stops (set screws), which have been
pre-set to 20 MBH (0.02” W.C. manifold pressure, 2 Volts DC signal input) at low fire
and 400 MBH at maximum fire (4.5” W.C. manifold pressure, 8 Volts DC signal
input) at zero back pressure. The regulator on the combination valve has been set to
high fire and should not need to be adjusted. The “Modulating Gas Valve” (butterfly
valve which is attached to the spring return actuator) will vary the amount of gas flow
into the burner.
Part 2 Service
Part 2
Service
VII
Valve Train
VIII
Sequence of
Operation
IX
Electronic
Control
X Start
Up
VI
Electrodes
Continued
