Fulton Vertical Electric (FT-N) Thermal Fluid (hot oil) Heater - Manual (Page 76)

Fulton Thermal Corp.*Electric Thermal Fluid Heaters Manual* Version 2010-0423
Page 76
needs to be replaced.
If the coil shows resistance, energize coil and check contacts.
With coil energized, normally open contacts should close
resulting in a reading of control voltage on both the common and
normally open contact.
c. If voltage exists on common but not on normally open contact
either switch contacts if another set of normally open contacts
are available or replace relay.
Safety Interlock
a) High temperature limit
1. All thermal fluid heaters have at least one High Temperature Limit. The
high temperature limit(s) is/are normally closed switch(es) that break on
a temperature rise over set point.
2. The switch may be either a solid state controller or a bulb and capillary
type switch. The High Temperature Limit is a safety device that protects
the thermal fluid and heat transfer coil from excessively high
temperatures.
3. Solid-state high temperature limits will have a manual reset. Bulb and
capillary type limits will not have a manual reset. If this/these switch(es)
trips, it is generally one of the following issues.
b) Flow rate is too low
1. Too low of a flow rate will result in a higher rate of heat transfer to the
thermal fluid and heat transfer coils. This will result in a higher
temperature difference between inlet temperature and outlet
temperature.
2. It is important to make sure that the minimum flow rate as specified by
Fulton for that specific model is maintained.
3. Check inlet and outlet pressures of the heater to determine differential
pressure and flow rate. Ensure that this flow rate meets or exceeds
minimums specified by Fulton (see chart). Also check differential
pressure switch for proper operation and setting.