COMPONENTS - Cartridge Heaters
Application Guidelines
- Up to 1.297" Dia.
- Up to 60" Lengths
- Up to 11,500 Watts
- 120 and 240 Volt
- Up to 1400°F Max. Working Temp.
- Modification Available to Fit Custom Applications


Type CIR cartridge heaters are most frequently used for heating metal parts by insertion
into drilled holes. For easy installation, the heaters are made slightly undersize
relative to their nominal diameter.
Determining Fit – At high watt densities, a close fit is
important. The fit is the difference between the minimum diameter of the heater
and the maximum diameter of the hole. For example, 1/2" diameter Type CIR cartridge
heater is actually 0.498" plus 0.000" minus 0.005". If this heater
is placed in a hole which has been drilled and reamed to a diameter of 0.503",
then the fit would be 0.01" (0.503" 0.493" = 0.01").

Determining Watt Density – Watt density refers to the heat fl ow
rate or surface loading. It is the number of watts per square inch of heated surface
area. For calculation purposes, CIR stock cartridge heaters have 1/4" unheated
length at each end. Thus, for a 1/2 x 12" heater rated 1,000 watts, the watt
density calculation would be as follows:
Watt density = W/ p x D x HL
Where:
- W = wattage = 1,000 W D = diameter = 0.5 in.
- HL = heated length = 11.5 in.
- Watt density = 1,000 / 3.14 x 0.5 x 11.5 = 55 W/In 2
Selecting Sizes and Ratings — The calculation of total heat
requirements for an application.
Determining, Quantity, Size and Rating — Once total heat
requirements are established, the quantity, size and rating of cartridge heaters
can be decided. Plan for enough heaters to permit even temperatures through the
part during heat-up and operation. The sensor for the temperature control should
be placed close to the working surface for accurate control.
Calculate Watt Density and Fit — After the wattage for each
heater has been established, the watt density and fit must be calculated. Then,
use Graph G-235 to be sure that the watt density is within allowable limits. For
example, a 1/2 x 12" CIR heater rated 1000 watts has a watt density of 55 W/in
2 . If it were used in a part with an operating temperature of 1000°F
with a fit of 0.01", the allowable watt density from the graph would be 90
W/in 2 . Thus, the actual watt density of 55 W/in 2 is well
below the maximum allowed. A substantial safety margin would exist and high reliability
can be expected.
If the heater selected had a watt density higher than that allowed by the graph,
consider the following changes.
- Using more heaters of lower watt density.
- Using longer or larger diameter heaters.
- Improving the fit.
- Reducing heat requirements by reducing heat losses or by allowing
for longer heat-up time.
Using the Maximum Allowable Watt Density Graph — This graph
is useful for choosing Type CIR cartridge heaters. The curves should be considered
as guides and not precise limits.
The graph is based on a 1600°F resistance wire temperature inside the cartridge
heater, when the heater is installed in an oxidized mild steel block. Watt density
values from the graph should be lowered by about 10% or more when other materials
are used which have a lower thermal conductivity or lower emissivity than oxidized
mild steel. Contact your Local Chromalox Sales office.
Cartridge Heaters Selection Guidelines
Type CIR High Watt Density
Advanced Internal Construction Plus Swaged Leads — The challenge
to Chromalox engineers was to design a cartridge heater that would out perform any
brand cartridge heater — under any given set of conditions, and to assure
that the customer receives and continues to receive the most heater performance
and life possible for his investment.
Type CIR Cartridge Heater — Includes several signifi cant
advances in cartridge heater technology. Its high performance characteristics have
been proven, not only in the laboratory, but also on Customers' equipment on selected
problem applications, at 1500°F and higher operating temperatures.
Type C-LD, C-HD & C-DE
Medium Watt Density
Type C Large Diameter Cartridge Heater — For medium and low
watt density applications. The tightly compacted refractory insulation provides
excellent heat transfer to the heavy wall stainless steel sheath. This means the
resistance wire runs at a lower temperature than competitive units with loose-fill
insulation; the result is much longer life. This heavy-duty construction also provides
high dielectric strength as well as shock and vibration resistance required for
many industrial applications.
Type CBH Electric Stud Heater — Used to wrench-tighten bolts
or studs to “shrink fit” tightness.
Type SCB Small Space Heater — Edison screw base installs
in standard porcelain lamp socket to heat very small spaces.
Cartridge Heaters - Selection Guide
Max. Work Model Applications Temp. (°F)
|
Watts
|
Dimensions (In.) Length
|
Dia.
|
Sheath Materal
|
Sheath Temp. Terminal Life (°F) Type Rating
|
Page
|
CIR
|
Molds, Dies, Platens, Hot Plates, Sealing
|
1400
|
75 - 5,000
|
1-1/4 - 48
|
1/4-3/4
|
INCOLOY®
|
1500
|
Swaged Leads
|
Superior
|
A-102
|
SST QST
|
Molds, Dies Platens, Presses
|
1400
|
Variable
|
5-120
|
3/8-1
|
INCOLOY®
|
1600
|
Flexible Leads
|
Standard
|
A-111
|
C-LD, C-HD, C-DE
|
Aluminum Extrusion Dies, Container Heaters
|
600
|
450 - 1,750
|
8-25
|
15/16-1-19/64
|
Stainless Steel and Brass
|
750
|
Bolt
|
Standard
|
A-107
A-108
|
MZ
|
Hot Press Metal Forming, Zone Control
|
1800
|
Variable
|
18-180
|
.495, .685 .935
|
INCONEL® 600
|
2000
|
Plug
|
Standard
|
A-109
|
CBH1
|
Shrink Tightening
|
1200
|
1,150 - 11,500
|
18-60
|
.553-1.106
|
Steel
|
1600
|
Standard Octagon Box with Handle
|
Standard
|
A-115
|
SCB
|
Closet and Control Cabinet Space Heating
|
600
|
50 - 200
|
4-3/4
|
1-3/8
|
Brass
|
1000
|
Edison Screw Base (light bulb socket)
|
Standard
|
A-113
|
HTRC
|
Heat Transfer and Release Coating
|
|
|
|
|
|
|
|
|
A-101
|
Note — Not UL Recognized or CSA Certified.
|
Cartridge Heater Application & Installation Recommendations
Applications
Application at High Watt Densities — Type CIR cartridge heaters
are designed and manufactured to provide watt density capabilities second to none.
To obtain best life at the highest watt densities allowed per Curve G-235 in the
Application Guidelines, close attention to application details is suggested.
- A. For closest fit and best heat transfer, holes should be drilled
and reamed, rather than just drilled to final diameter with a general- purpose drill.
- B. The sensor for the temperature control should be placed between
the working surface of the part and the heaters. The temperature of the part approximately
1/2" away from the heaters is used in selecting maximum allowable watt density
from the graph.
- C. Control of power is an important consider- ation in high watt
density applications. On/Off control is frequently utilized, but it can cause wide
excursions in the temperature of the heater and working parts. SCR power controls
are valuable in extending the life of high watt density heaters, since they effectively
eliminate on-off cycling.
Application at Medium Watt Densities — Curve G-235 in the
Application Guidelines shows maximum allowable watt density for various fits and
operating temperatures. The vast majority of applications do not require maximum
W/In 2 , however. Use a watt density only as high as you need. Take advantage
of the safety margin provided by using ratings less than the maximum allowed. Select
and space heaters for most even heat pattern rather than for highest possible wattage
per heater.
At medium watt densities, general purpose drills are usually adequate for drilling
holes. Typically, these result in holes 0.003 to 0.008" over the normal size
of the drill, resulting in fi ts of 0.01 to 0.015". Of course, the tightest
fit is desirable from a heat transfer standpoint, but somewhat looser fits aid in
installing and removing cartridge heaters, especially long ones. Holes drilled completely
through the part are recommended to facilitate removal of the heater. After drilling,
clean
Operation in Vacuum — When heaters are operated in a block
which is in a vacuum, the inside of the holes should be pre-oxidized to improve
emissivity. Substantial reductions in maximum allowable watt density are usually
necessary for vacuum operation. Where possible, the installation should be designed
so that the lead end of the heater is outside the vacuum. When the lead end of the
heater is inside the vacuum, a voltage of 120 volts or less is recommended. On an
unsealed heater, outgassing may be expected.
Operation in Square Grooves — Round type CIR cartridge heaters
may be installed in square or v-shaped grooves if this proves convenient. The inside
of the groove should be treated to improve its emissivity (by oxidizing or anodizing).
Allowable W/In 2 can be estimated by using the 0.05" fit line in
the graph, providing that the square is approximately the same width as the nominal
diameter of the heater.
Operation on 480V — Chromalox type CIR cartridge heaters
5/8" diameter and larger can be operated on 480 volts. One approach is to take
two stock 240 volt heaters and connect them in series on 480 volts. Another is to
order specially rated 480 volt cartridge heaters. Check with your Local Chromalox
Sales office for recommendations.
Because of higher voltage stresses inside the heater, lower maximum watt densities
are allowable in 480 volt applications, either with two 240 volt heaters in series
or with specially rated 480 volt units. To determine maximum allowable watt density
at 480 volts, enter Curve G-235 with an operating temperature value which is 200°F
higher than the actual operating temperature. A maximum operating temperature of
1000°F is suggested.
Cartridge Heater Testing Recommendations
Testing Recommendations—Testing under simulated operating
conditions is suggested when equipment manufacturers design new products. Cartridge
heaters of the appropriate physical size are operated on a variable transformer
until the heat output is at the proper level. Then, voltage and current measurements
are taken and required wattage rating is calculated. Heaters of the correct wattage
rating are then ordered for the designed product.
Cartridge Heater Installation Recommendations
- On moving machinery, anchor the leads securely. As little movement
as possible should be allowed close to where the leads emerge from the heater. A
loop in the lead wire will frequently extend lead life. If application conditions
result in continual lead flexing, terminate the cartridge heater leads at a terminal
block which moves with the heated assembly. Flexing is transferred to the extension
leads which can be economically replaced.
- For rapidly vibrating equipment, employ the terminal block described
above. Keep leads from heater to block short and well supported to prevent lead
movement due to vibration.
- Protect leads from spray, oil and abrasion. Contaminating liquids
and vapors can enter unsealed cartridge heaters and cause insulation breakdown.
- Avoid tape on leads where they emerge from the cartridge heater.
The adhesive on some tapes can enter the heater and turn to carbon which is electrically
conductive. Where glass tape cannot be avoided, a tape with a silicone based adhesive
is suggested.
- Design the installation so that the leads are in an ambient temperature
which doesn't exceed the rating on the lead insulation (842°F for standard leads).
Where temperatures require it, use nickel or nickel-plated copper wire with fluoropolymer
insulation, silicone impregnated Fiberglas ® or Rockbestos ®
insulation to extend leads.
- Graphite and other lubricants to help insert the cartridge heater
into the hole are generally not recommended. These are electrically conductive and
can get on the lead end of the heater unless extra care is taken. Use Chromalox
heat transfer and release coating.
- As operating temperatures rise, thermal insulation on the heated
part becomes more desirable to conserve heat. Thermal insulation results in lower
wattage requirements and therefore lower watt density on the heaters. Other benefits
are more even work temperatures and greater operator safety and comfort.
- Leads must not extend into the hole containing the cartridge heater.
Generally, the lead end of the heater sheath should be flush with the surface of
hole or extended by 1/16 inch.
Cartridge Heaters Modifications & Options
Cartridge heaters can be easily specified to meet the demands of special applications.
Simply select from a variety of standard options and features to customize the heater
to your specific needs. For customized engineering or alternative options, contact
your Chromalox sales representative for fast turnaround on your specifications.
- Leadwire Types
- End Seal Options
- Lead Options
- Mounting Options
- Built-In Thermocouple
Leadwire Types
Description
|
Volts
|
(°F) (°C) Operating Temperature
|
Mica Fiberglas® Insulation
|
300V Standard 600V
|
842
|
450
|
Fluoropolymer
|
300V 600V
|
392
|
200
|
Seal Options
Type
|
Description/Application
|
Epoxy
|
Epoxy seal available on above leads by voiding end of sheath and filling with epoxy
to provide a moisture barrier.
|
Fluoro-polymer
|
A swaged-in seal that provides additional moisture resistance.
|
RTV
|
For applications where a moisture barrier is required.
|
Hermetic
|
Ceramic-to-metal seal is good for element temperatures up to 1000°F. Specify
heater length beyond the seal. Metal portion of the seal overlaps the heater sheath
by 3/16".
|
MR SEOT2
|
Meets UL FileSEOT2.SA 12768
|
End Seal Temperature Limits
Description
|
(°F) (°C) Operating Temperature
|
Air Set Cement Standard
|
1000
|
538
|
Epoxy Seal
|
194
|
90
|
Fluoropolymer Seal
|
392
|
200
|
RTV Seal
|
284
392
|
140
200
|
Hermetic Seal
|
1000
|
538
|
MR-SEOT2
|
374
|
190
|
End Seal Options
Hermetic Seal
Ceramic-to-metal seal is good for element temperatures up to 1000°F. Specify
heater length beyond the seal. Metal portion of the seal overlaps the heater sheath
”. For washdown conditions.
Lead Options
Right Angle Flexible Leads
Strain Relief
Strain Relief supports leads to reduce bending, crimping, and breakage.
Flexible Stainless Steel Conduit
Flexible Stainless Steel Conduit provides leadwire protection from abrasion and
sharp edges, and facilitates easier handling in harsh environments. Available in
both straight and right angle confi gurations.
Protective Spring
Available in both straight and right angle configurations, the Protective Spring
gives strong, yet flexible leadwire protection from bending, fatigue and flexing.
Metal Braid
Stainless Steel metal braid protects leadwire from abrasion and sharp edges, yet
maintains flexibility and ease of installation. Metal braid is available in both
straight and right angle configurations.
Ceramic Beads
Ceramic Bead insulation can be specified to protect leadwires from high ambient
tem peratures up to 1200 F (649C). To order, specify ceramic beads length and additional
lead length.
Threaded Post Terminals
Post Terminals provide a strong, secure connection to buss bars or ring/fork connectors.
Available only on 5/8 and 3/4” diameter heaters.
Mounting Options
Threaded Fittings
Threaded fittings allow the heater to be easily installed into a threaded hole for
immersion applications. Available with single or double threaded fi ttings. The
fitting overlaps the cartridge heater sheath by 1/4". Specify “brass”
Threaded Fitting Sizes
|
Nom.Heater Diameter (In.)
|
NPT Size (In.)
|
Hex Size (In.)
|
1/4
|
1/8 - 27
|
7/16
|
3/8
|
1/4 - 18
|
9/16
|
1/2
|
3/8 - 18
|
11/16
|
5/8
|
1/2 - 14
|
7/8
|
3/4
|
3/4 - 14
|
1-1/16
|
Mounting Flange
The mounting flange option allows for easy mounting and specific positioning
Wire Pull
The Wire Pull assists in heater removal.
Download the Cartridge Heaters Selection, Applications, and Installation Guidelines