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OPERATION
1. Do not heat solutions that are corrosive to the heating element
sheath or the heating chamber.
WARNING: Type NWHO Circulation Heaters are
equipped with steel heating elements and steel heat-
ing chambers. It is the responsibility of the user to
know the chemical composition of the corrosive solu-
tion and the character of the materials entering the
solution as well as the corrosive effect of the solution
upon the heating elements and chamber. Chromalox
cannot warrant any electric circulation heater against
failure by sheath corrosion if such failure is the result
of operating conditions beyond our control.
2. Terminal ends of heater must be protected from drippings, con-
densation, spray or direct spill-over of material. Their presence at
the terminals may damage heater electrical insulation. Liquid-tight
terminal enclosures are available to protect heater. Check with
local sales representative.
3. If foreign material is carried by the liquid flow, install suitable fil-
ters in the inlet pipe line to the heater.
4. Do not allow heater to operate when liquid flow is interrupted.
MAINTENANCE
1. WARNING: Hazard of Shock. Disconnect all power
before servicing heater.
2. Remove heating element assembly periodically to check heater
sheath for scaling, corrosion or excessive oxidation. Correct oper-
ating conditions to minimize sheath deterioration.
3. Periodically check temperature control and limit control operation
to insure accurate and safe process operation.
4. Check all electrical connections periodically and retighten connec-
tions which may have loosened in service. Replace wire terminals
that show signs of oxidation which would interfere with establish-
ment of reliable electrical connections.
3. Whether vertically or horizontally, the heater should be rigidly
mounted so that vibration is at a minimum since excessive vibra-
tion will result in erratic thermostat operation. The NWHO-3 is
provided with mounting lugs to support the heating chamber. (See
photo.)
4. By using a slotted mounting assembly on either of the lugs, the
heater chamber will be permitted to expand with increasing tem-
perature.
5. DANGER: Hazard of Fire. Provide minimum of 6” spacing
from chamber and related piping to nearest combustible material.
Do not operate near combustible fluids or in combustible vapor or
gas laden atmosphere.
6. Provide adequate space at terminal end to permit withdrawal of the
heater from chamber should servicing be required.
INSTALLATION
WARNING: Hazard of Shock. Any installation involving
electric heaters must be effectively grounded in
accordance with the National Electrical Code to elim-
inate shock hazard.
1. Be sure line voltage matches heat voltage (on nameplate).
2. Electric wiring to heater must be installed in accordance with local and
National Electrical Codes by a qualified person as defined in the NEC.
3. Power controllers must be used when heaters are rated 3 phase and
when the heater amperage exceeds the rating of the thermostat.
4. Refer to Wiring Diagram, Table B, to properly connect the heater.
Wiring Diagrams — Table B
Note: Use wire size and type specified by N.E.C. 480V and 550V heaters require 600V wire, per
N.E.C. Contactors and wire supplied by customer.
WIRING
L1
L2
L3
Ground
Contactor
Thermostat
120V
or
240V
240V, 1Ø 240V, 3Ø ss 480V, 1Ø 480V, 3Ø ss
Model Fig. Fig. Fig. Fig.
NWHO-3301 2 1 2 1
NWHO-3451 2 1 2 1
NWHO-3601 2 1 2 1
NWHO-3751 2 1 2 1
NWHO-3901 2 1 2 1
NWHO-3031 2 1 2 1
NWHO-3041 2 1 2 1
Note: Dotted lines indicate “customer furnished.” However, Thermostat could have been furnished by Chromalox if so specified on the order.
Figure 1
240V, 480V 3Øss
Figure 2
240V, 480V, 1Ø
Use contactor when the heater amperage exceeds
the rating of the thermostat.
Ground
Contactor
Thermostat
Line
120V
or
240V