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Chromalox
®
DIVISION
4
SECTION
NWHO
SALES
REFERENCE
DATE
SERVICE REFERENCE
Installation
and
RENEWAL PARTS IDENTIFICATION
PE437-1
APRIL, 1999
(Supersedes PE437)
161-303184-001
GENERAL
INSTALLATION
© 2010 Chromalox, Inc.
Type NWHO(F)-27 Series Circulation Heater
(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.
Hazardous area terminal enclosures are available, consult your
local Chromalox representative for details.
The NWHO-27 series is a general-purpose oil circulation heater
intended for use indoors.
The 27 or 36 steel sheathed tubular elements are welded to a remov-
able steel flange and centered in a 10 inch diameter steel heating chamber.
Depending upon the specifications, the NWHO-27 may or may not be
factory equipped with AR or other Chromalox thermostats. Such ther-
mostats function to control outlet temperatures and limits internal tem-
perature under abnormal flow conditions. These controls do not fail-safe.
Thermocouples are also available as an option.
CAUTION: Users should install adequate back-up con-
trols 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 installation is the responsibility of the user,
Chromalox will be glad to make equipment recom-
mendations.
WARNING: Hazard of Shock. Disconnect all power
before installing heater.
1. Vertical mounting (axis of chamber vertical as in sketch above) is
preferred. (Terminal housing at top of heater) (Figure A)
2. When mounting heater horizontally, inlet and outlet MUST be up.
In any other position, heater cannot be purged of air and elements
may be seriously damaged. (Figure B)
3. This series of circulation heaters are provided with mounting lugs
to support the heater chamber. Refer to sketch above for location
of these mounting lugs.
4. Mount heaters to permit unrestrained expansion of chamber due to
temperature. This can be accomplished by using a slotted mount-
ing assembly on either of the lugs.
5. DANGER: Hazard of Fire. Provide minimum of 6” spacing
from a chamber and related piping to nearest combustible materi-
al. Avoid operation of heater near combustible fluids or in com-
bustible vapor or gas laden atmosphere.
6. Provide adequate space at terminal end to permit withdrawal of the
heater from chamber should servicing be required.
7. If two or more heaters are needed to provide the needed heating
capacity, arrange them for series oil flow.
8. DANGER: Possible Explosion. A pressure relief valve
should be provided by customer at outlet of vessel. There should
be no other valving between vessel and valve.
Thermostat
(When Specified)
3 - 1-3/8" K.O.
for 1" Conduit
3" Pipe
Outlet (Std.)
2 Mtg. Lugs Ea
with Three 3/4" - 10
x1-1/8" Deep
Holes on 1-3/4"
Centers
3" Pipe
Inlet (Std.)
3/4" NPT
Pipe Plug
11"
A
A
A
B
15-15/16"
C
17-1/8"
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-2780R15 240 or 480 3 80 20 77-9/16 52 48-1/2
NWHO-2790R15 240 or 480 3 90 20 81-9/16 56 52-1/2
NWHO-27100R15 240 or 480 3 100 20 87-9/16 62 58-1/2
NWHO-27120R15 240 or 480 3 120 20 97-9/16 72 68-1/2
Fuel Oil Heaters
NWHO-2750R15 240 or 480 3 50 12 77-9/16 52 48-1/2
NWHO-2760R15 240 or 480 3 60 12 87-9/16 62 58-1/2
NWHO-2770R15 240 or 480 3 70 12 97-9/16 72 68-1/2
Dimensions and ratings vary according to customer requirements.
Check engineering drawing for specifications.
F-Denotes heater is baffled, i.e., NWH0F