Hubbell Electric Heater Company MSE - Manual (Page 17)

Water temperature below
settings at all times Faulty thermostat. Check thermostat adjustment.
Monitor thermostat as described in
Section III, Quarterly Inspection.
Replace if necessary.
Blown fuse in element fuse
block, if installed. Replace fuse.
Heating element not working on
all phases Check to see that heating element
is working on all phases, by
checking the resistance (ohms)
value for each element and
comparing with the chart
included in Section VI.
Heater improperly sized Verify heater is properly sized for
the flow rate and temperature rise
of your system. See formulas
included in Section VI. Replace
elements with proper size as
necessary.
Relief valve discharges
continuously Excessive temperature or
pressure in tank Temperature and pressure relief
valves are made to operate if the
water temperature exceeds 210
°F
or water pressure exceeds the
pressure rating of the safety relief
valve. If trouble is excessive
temperature, then thermostat is not
shutting off at the right setting and
thermostat must be replaced.
17