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TECHNICAL
When
should I use a braided cable, and when should I use an overjacketed
cable?
Braided
cables are intended for use in dry areas. The braid is tinned copper,
which allows for maximum conductivity but can deteriorate over time
when exposed to moisture. For wet areas, select an overjacketed
cable. In the commercial products, overjacket is polyolefin; in
industrial and high temperature cables overjacket is flouropolymer,
which also offers superior corrosion resistance.
I
see cables listed for 240 volt use. What if I only have 208 volts
available?
Cables
rated for 240 volts can be used at any available voltage from 208 to
277. There will be slight variations in heat output, depending on the
voltage applied. The Heater Design Data Sheets include selection
guides at nominal voltages (120 or 240) as well as 208v and
277v.
How
do I know what category of cable I should use?
Commercial
cable products have UL approval for ordinary (non-hazardous) areas.
These cables have 18 gauge bus wire and are ideal for freeze
protection or for temperature maintenance up to about 150 degrees F.
For the same temperature ratings but with 16 gauge bus wire for
longer heater cable segment length and additional UL & FM
approvals for Class I Division 2 hazardous locations, use an
Industrial cable product. Both Commercial and Industrial products
have a maximum intermittent temperature exposure of 185 degrees F.
For higher maintain temperatures (up to 250F) or higher exposure
temperatures (up to 375F) select a cable from the High Temperature
product group.
If
I am using heater cable on a pipe, why do I need insulation?
Without
insulation the heat produced by the cable will dissipate into free
air, with little or no effect on pipe temperature. Even a small
amount of insulation will help keep the heat from the cable on the
pipe. (See the watt loss charts for more specific information)
Okay,
then if I insulate the pipe, why do I need heat tracing?
Good
question! Insulation slows the loss of heat to ambient air, but does
not stop it. The heater cable is used to offset the heat loss through
the insulation.
Do
pipe supports and valves need any special treatment?
Yes.
Pipe supports and valves will lose more heat than straight sections
of pipe, so additional cable is required at these locations. The
installation manual that ships with your order includes a table to
let you know how much extra cable to use.
Can
I install heater cable on top of the pipe?
Well,
you can but we sure don’t recommend it. For one thing, a heater on
the top of the pipe is more susceptible to mechanical damage --
having a tool dropped on it or someone walk across it. Also, as a
pretty good general rule if the pipe is only partially filled, the
fluid tends to be in the lower quadrant of the pipe. (At least on
planet Earth.) Looking at the cross section of the pipe as a clock,
four o’clock or eight o’clock are ideal.
How
do you know whether to use aluminum or fiberglass tape?
Aluminum
tape is typically used for plastic pipes and tanks to aid heat
distribution. It is also required when installing heater cable on
steel tanks. Fiberglass tape is recommended when attaching heating
cables to stainless or metal pipes. Fiberglass tape is applied across
the heater cable at every foot; aluminum tape is applied on top of
the entire span of heating cable after it has been secured to the
pipe with fiberglass tape.
If
the heater cable is self-regulating, do I need a controller?
That
depends on how precisely you need to control the temperature of the
pipe. If tight control is required, a line sensing device is best.
For freeze protection applications, an ambient sensing controller
often used with self-regulating heating cables. When using a line
sensing controller, a separate controller should be used for each
unique flow condition.
How
should I decide whether to use ambient or pipe sensing controllers?
Ambient sensing
controllers typically offer a simpler installation and lower material
cost, since one thermostat can control multiple pipe segments.
However, energy costs will be higher, since the controller does not
respond to changes in pipe temperature. (Think of the heat in your
house -- if the thermostat was on the front porch instead of in your
living room, the heat would be on most of the winter, keeping the
house much warmer than needed and energy bills higher than
necessary.)
Pipe sensing controllers are more precise and
energy efficient, but can have a higher initial material and
installation cost since a separate controller is required for each
unique pipe size and flow condition. Controlling multiple pipes with
a single pipe sensing controller can lead to freeze ups.
For a
single pipe run, pipe sensing controllers are usually the best
option. For mutliple pipes, consider the balance between upfront cost
and long term operating costs. For long pipe runs or where total
electrical loads are high, the initial cost differential for pipe
sensing controls can be an economical choice in the long run.
What
is a “self-regulating” heater cable?
A
self-regulating heater provides a watt output that increases as
temperatures fall and decreases as temperatures rise. The wattage
rating given for each cable is the output of that heater at nominal
voltage (120 or 240) at 50 degrees Fahrenheit. Above 50 degrees, the
cable will put out less than its nominal wattage; below that
temperature, it will produce higher than nominal wattage. As the
cable heats up, output approaches zero.
Is
ground fault protection required for heating cable systems? What
type?
The
National Electrical Code requires a ground fault protection device
for any electrical heating cable circuit. There are two basic types
of ground-fault protection.
GFI devices are personnel
protection with a 5 to 8 mA trip level. Typically this type of
protection will cause nuisance tripping when used with heater
cables.
GFEPD (ground fault equipment protective device)
is used for equipment protection, with a trip level of 30 mA. This is
typically used for heater cable applications and is specifed by the
N.E.C.
This protection can be provided by using a GFEPD branch
circuit breaker to power the heater cable, or by using an electronic
controller which includes ground fault protection. See the electronic
thermostat section for
product options.
What
is the effect of wind on heat traced lines?
An
insulated pipe is not affected by wind chill the way a human being
is. In absolutely still conditions, a thin layer of air around the
insulation helps reduce heat losses, but once air is moving that
layer is gone. Heat loss calculations for a given pipe at 5, 10, 25,
or 50 mph wind do not vary a great deal.
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