Lochinvar 399 - Manual (Page 62)

Hydronic Heating Boilers and
Domestic Water Heaters
62
Check the flow switch and
Tekmar pins #15 and #16
for 24VAC.
Step 1
Does the power switch
provide power to the unit?
Check the switch for proper
operation. Check the line voltage.
NO
YES
Check 24VAC at TH
(orange wire) on the
ignition module.
YES
Check all safety limit
devices, all connectors
behind the control panel
and voltage from the
transformer to B2.
NO
YES YES
Exchange ignition
module.
Check staging
relay (S2). Is
there 120VAC on
the red wire to the
fan?
NO YES
Replace
relay.
Replace fan.
YES
Prepurge light comes on.
Status light does not
blink 1 flash continuous.
Step 3
Check air pressure
switch 24VAC on tan
wire (N.O.).
NO
24VAC at PS (tan wire) at ignition
module and/or connector plug for
proving relay secure.
NO
YES
Check air pressure
switch for correct
pressures.
Replace air pressure
switch.
Correct air settings.
May have to clean
burners/heat
exchanger.
YES
Trial for ignition completes
and gas valve(s) opens. Does
not go into flame failure.
NO
Check amp draw
for 3.1 amps.
NO
Is air switch
bouncing?
YES
Replace igniter if less than 2.75 amps.
YES
YES
NO Combustion
air blower
comes on.
NO
Does F2 on ignition module
have 120VAC?
YES
Is there 24VAC at B2
on the terminal strip? Step 2
Step 4
NO
NO
Gas valve(s) stays open
and is getting 24VAC. Step 5
NO
Check inlet gas pressure
both static and dynamic.
Check manifold pressure.
Check draft. Check air
pressure.
YES Is the flame sense signal to the
ignition module 5uA dc or greater?
NO
Replace gas valve.
Check ignition module pin #05
(replace RLY2402 if no
voltage).
Unit is running.
NO
NO
Is 24VAC present at main unit
connector (3x3 amp plug) red
wire?
YES
TROUBLESHOOTING GUIDE
399,999 - 750,000 Btu/hr Models