Fulton Hopkins (HPN) Horizontal Coil Thermal Fluid (hot oil) Heater - Manual (Page 74)

© The Fulton Companies
MAINTENANCE
HPN-IOM-2014-0416
SECTION 4
4-14
TABLE 10-G - AIR SWITCH TROUBLESHOOTING
Problem Potential Remedy
Combustion Blower Fan is
Dirty If the cups of the squirrel cage type fan become dirty, less air will be moved by the fan. If the fans are dirty enough, there will not be
enough air fl ow for the air switch to prove. You should assure that the combustion blower fan is clean, reset the fl ame programmer
and try to light unit again
The sensing line is plugged,
crimped or pointing in the
wrong area If the sensing line to the air switch is crimped or blocked, the switch will not sense the proper pressure. Ensure that the sensing line
is clear and not crimped by removing both sides of the sensing line and using compressed air to blow through the line. Also ensure
that the elbow acting as an air scoop is pointing directly into the air stream. Reset the fl ame programmer and try to light the unit
again.
The Switch setting is improper The adjustment screw for the air switch is located opposite the electrical connections. A gray cap covers the screw. Turn the screw
clockwise to increase setting, counter-clockwise to decrease setting. To set switch, run unit at low fi re. Increase setting 1/2 turn every
5 seconds until unit trips on interlock. Decrease setting by 2 full turns. Reset unit.
TABLE 10-H - AIR FILTER SWITCH TROUBLESHOOTING
Problem Potential Remedy
The air fi lter is dirty If the air fi lter becomes dirty, the fan will generate greater suction. Too much suction will result in not enough airfl ow for proper
combustion and mixing and will cause air switch to trip. You should regularly change fi lters on a schedule dependent on how dirty the
makeup air is. After checking or changing air fi lter, reset the fl ame programmer and try to light unit again.
There is an obstruction in the
make-up air ducting Units that have make-up air ducting need to assure that blockage to the ducting does not occur. Check outside termination and any
bends in the ducting for blockage. Clear blockage, reset fl ame programmer and try to light unit again.
The sensing line is pointing in
the wrong direction The sensing line for the air fi lter switch is supposed to provide the static pressure of the air box. The termination of the sensing line
should be pointing in the direction that limits its contact with moving air. If the sensing line is pointed perpendicularly to entering air
stream, the switch will not sense the proper pressure and could give a false indication of air box suction. Reset the fl ame programmer
and try to light the unit again.
Switch setting is improper The adjustment screw for the air switch is located opposite the electrical connections. A gray cap covers the screw. Turn the screw
clockwise to increase setting, counter-clockwise to decrease setting. The switch setting should be set in such a way that with 50 % of
the air box opening blocked, the switch will trip. Reset switch setting, reset the fl ame programmer, and try to light the unit again.
TABLE 10-I - AUXILIARY BLOWER MOTOR STARTER TROUBLESHOOTING
Problem Potential Remedy
The blower motor starter coil
is bad If this is the case, the blower starter will not latch in. Check for voltage to the coil. If proper voltage is present and the starter does not
pull in, that proves the coil is bad. Replace the starter, reset the fl ame programmer and try to light unit again.
The auxiliary contacts are
burned or pitted Visibly inspect contacts. With power off , attempt to clean or replace starter if damaged. Reset fl ame programmer and try to light unit
again.
TABLE 10-J - HIGH TEMPERATURE LIMIT TROUBLESHOOTING
Problem Potential Remedy
Flow rate is too low Too low of a fl ow rate will result in a higher rate of heat transfer to the thermal fl uid and heat transfer coils. This will result in a
higher temperature diff erence between inlet temperature and outlet temperature.
It is important to make sure that the minimum fl ow rate as specifi ed by Fulton for that specifi c model is maintained Check inlet
and outlet pressures of the heater to determine diff erential pressure and fl ow rate. Ensure that this fl ow rate meets or exceeds
minimums specifi ed by Fulton (see chart). Also check diff erential pressure switch for proper operation and setting.
Heater is over-fi red If the heater has more fuel input than design, it is probable that the heat transfer rate will increase beyond design. Check input to
heater at high fi re for modulated heaters or at the standard rate for on / off units. This can be done by either using a corrected gas
meter reading or measuring gas pressure supplied to the burner compared to factory test-fi re settings.
If input is improper, inspect burner as described below. If burner is not damaged or have improper components, adjust fuel input
and combustion to specifi cation.
Gas-fi red burner is damaged Pull and inspect the burner. Primary areas of concern for gas-fi red units are the orifi ce plate, pilot assembly seating and orifi ce plate
gap.
If the orifi ce plate is warped or burned through, pilot assembly is not seated or gap between orifi ce plate and gas tube is improper,
more fuel than designed for will enter the furnace.
This will cause the heater to have more fuel input than designed for. The design fl ow rate will then be too low causing the fl uid to
heat up higher than it should.