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Chromalox
®
DIVISION
4
SECTION
NHWO
SALES
REFERENCE
DATE
SERVICE REFERENCE
Installation
and
RENEWAL PARTS IDENTIFICATION
PE406-5
FEBRUARY, 1999
(Supersedes PE406-4)
161-048710-001
GENERAL
INSTALLATION
© 2010 Chromalox, Inc.
Type NWHO-3 Series Circulation Heaters
(for Regular and Fuel Oil Heating)
WARNING: This heater is not intended for use in haz-
ardous atmospheres where flammable vapors, gases,
liquids or other combustible atmospheres are present
as defined in the National Electrical Code. Failure to
comply can result in explosion or fire.
The NWHO-3 series is a general-purpose regular and fuel oil solu-
tion circulation heater intended for use indoors. It is designed for 150
psig at 550˚F per ANSI standards.
The 3 steel-sheathed tubular elements are centered in a 3” diame-
ter steel heating chamber and welded to a removable steel flange. The
assembly is surrounded by 1-1/2” insulation and sheet metal jacket.
Depending upon the order specifications, the NWHO-3 may or
may not be factory equipped with AR or other Chromalox thermostat.
Such thermostats function to control outlet temperatures and to limit
internal temperatures under abnormal flow conditions. These controls
do not fail safe.
CAUTION: Users should install adequate back-up controls
and safety devices with their electric heating equipment.
Where the consequences of failure may be severe, back-
up controls are essential. Although the safety of installa-
tion is the responsibility of the user, Chromalox will be
glad to make equipment recommendations.
WARNING: Hazard of Shock. Disconnect all power
before installing heater.
1. Vertical mounting (Preferred) —
When the heater is vertically mounted, the terminal housing will be
at the top of the heater. The inlet pipe will be located on the side
near the bottom of the heater and the outlet pipe at the top.
The axis of the chamber will be in a vertical position as in the
photo above and as in Figure A.
Note: A drain pipe located at the bottom of the heater should be
provided and enough room left, when mounting heater, to allow
draining the heater.
2. Horizontal Mounting (Optional) —
When mounting heater horizontally, inlet and outlet pipes must be
up. In any other position, heater cannot be purged of air, and ele-
ments may be seriously damaged. (See Figure B.)
Specifications — Table A
Incorrect
Correct
Figure A — Vertical Mounting
Figure B — Horizontal Mounting
Correct
Incorrect
Regular Oil Heaters
Dimensions (In.)
Model Volts Phase kW W/In
2
ABC
NWHO-33015 3 32-15/16 22-1/2 16-1/2
NWHO-34515 4.5 32-15/16 22-1/2 16-1/2
NWHO-36015 240 or 480 1 or 3 ss 6 23 42-15/16 32-1/2 26-1/2
NWHO-37515 7.5 55-7/16 45 39
NWHO-39015 9 55-7/16 45 39
NWHO-30315 3 32-15/16 22-1/2 16-1/2
NWHO-30415 240 or 480 1 or 3 ss 4 15 42-15/16 32-1/2 26-1/2
NWHO-30615 6 55-7/16 45 39
Fuel Oil Heaters
A
B C
8-1/32”
12-5/16”
6-1/8”
Thermostat
Type AR
Mounting Lugs
3/8” - 16
Threaded Holes -
1-1/2” Deep
1-1/4” Centers
1-3/8” Conduit
Openings
1” Pipe
Outlet
1” Pipe
Inlet