Abstrict
An electric heater is provided with an identifying resistor associated
with a connection between the heater and a fan control. When the
electric heater is connected to the control, the identifying resistor
provides information with regard to the capacity of the particular
electric heater that is being attached to the control. The control
then utilizes this particular capacity to control both the electric
heater and an associated fan motor.
Claims
10. An electric heater comprising: at least one electric heating
elements for delivering heat; and a connection to be connected to
a control for said electric heater, said electric heater having
an identifying characteristic provided to the control when said
electrical connection between said electric heater and the control
is made, said identifying characteristic providing information with
regard to a capacity of said electric heater.
11. The electric heater as set forth in claim 10, wherein said
identifying characteristic is provided by an identifying resistor,
with distinct identifying resistances being associated with different
levels of capacity for said electric heater.
12. The electric heater as set forth in claim 11, wherein said
identifying resistor is positioned within a wire harness for connecting
said electric heater to the control.
13. The electric heater as set forth in claim 10, wherein said
identifying characteristic is selected from a family of available
identifying characteristics, said selected identifying characteristic
having a value associated with said capacity of said electric heater,
and others of the family of available identifying characteristics
having a different value associated with electric heaters of a differing
capacity.
14. A family of electric heaters comprising: a plurality of electric
heaters each having electric heating elements for delivering heat,
said family of electric heaters having a plurality of heating capacities;
and a connection to be connected to a control for each of said family
of electric heaters, said family of electric heaters each having
an identifying characteristic to provide to the control when an
electrical connection is made between each of said family of electric
heaters and the control is made, said identifying characteristic
associated with each of said family of electric heaters providing
information on the capacity of each electric heater in said family
of electric heaters to the control, such that the control can identify
the capacity of the particular electric heater of said family of
electric heaters.
15. The family of electric heaters as set forth in claim 14, wherein
each of said identifying characteristic is provided by an identifying
resistor, with distinct identifying resistors being associated with
different levels of capacity for said family of electric heaters.
16. The family of electric heaters as set forth in claim 15, wherein
said identifying resistors are positioned within a wire harness
for connecting said electric heater to a control.
Description RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/707,524 which was filed Dec. 19, 2003.
BACKGROUND OF THE INVENTION
[0002] This invention relates to an electric heater that carries
an identifying characteristic to communicate the capacity of the
electric heater to a control.
[0003] Electric heaters are utilized in many heating applications.
Typically, an electric heater has electric coils that generate heat.
An associated fan blows air over the coils, and the air is heated,
and then delivered into a space to be heated.
[0004] A control is typically associated with at least the electric
fan, and preferably the electric heater. The control receives signals,
such as a demand signal from a thermostat, and actuates the electric
heater and fan, as appropriate, to provide the demanded environmental
conditions.
[0005] Among the items that must be communicated to more modern
fan controls is the capacity of the electric heater. To provide
optimum efficiency, the desired temperature and to provide most
reliable operation, the control operates the fan motor dependent
upon the capacity of the electric heater. However, in the field,
there are many available heater capacity options. Thus, when installing
a heater, a control for the fan must be configured to be provided
with information on the actual capacity of the installed heater.
It is often the case that this configuration is done improperly
by the installer. The control then does not provide optimum operation.
SUMMARY OF THE INVENTION
[0006] In the disclosed embodiment of this invention, an electric
heater is provided with a reporting characteristic that provides
control information with regard to the capacity of the electric
heater. In a preferred embodiment, an electrical connection between
the electric heater and a control includes some electrical characteristic
that provides an electrical signal corresponding to the capacity
of the electric heater. Most preferably, an identification resistor
is included into the electric heater, and is associated with a particular
capacity. The control is also a control for controlling a fan coil,
such that the fan can be operated at an optimum level to provide
the desired temperature, efficiency, and reliability given the actual
installed electric heater capacity.
[0007] These and other features of the present invention can be
best understood from the following specification and drawings, the
following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 schematically shows a fan and heater combination.
[0009] FIG. 2 is a schematic wiring chart.
[0010] FIG. 3 shows an exemplary look-up table.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0011] FIG. 1 schematically shows system 20 for providing heated
air to an environment. As known, an electric heater 22 generates
heat through electric heating elements. A fan blows air over the
electric heater elements to be heated. The air is delivered into
ducting 23, and then to the environment. A control 26 controls the
fan and the heater, dependent upon a desired state, such as may
be requested through a thermostat control 32.
[0012] FIG. 2 is a wiring diagram for the inventive system 20.
As shown, the electric heater 22 has an identifying resistor 34.
A wire harness connection 36 and 38 provides information exchange
between the heater and the control as shown at 33. As shown also,
the control 26 receives information at 30 from the thermostat 32,
and at 28 to and from the motor 24.
[0013] The control 26 operates to take signals in from the thermostat
32, and to control the fan 24 and electric heater 22 to achieve
a demanded level of heated air to an environment.
[0014] The provision of the identifying resistor 34 ensures that
the control 26 will determine the capacity of the electric heater,
once the connection 36 and 38 is made. Thus, a distinct identifying
resistor value would be associated with each of the available capacity
levels for the electric heater 22. Such information would be stored
in the control 26, and related to the various capacities of available
electric heaters at 33. Once the connection 36 and 38 is made, an
electrical signal is sent to the control 26 such that the control
26 has reliable information with regard to the capacity of the heater
22. While an identifying resistor is preferred, other ways of providing
an electric identifier would come within the scope of this invention.
In the. past, information with regard to the heater capacity has
been entered manually, and has sometimes been improperly entered.
[0015] In the preferred embodiment, and as can be seen, when the
electrical connection 36 and 38 is made, the identifying resistor
34 is connected to a circuit to control 26. Identifying resistor
34 has two ends, connecting into mating wires in the control half
of the electrical connection 38. Common line 40 is connected to
one end of the two connections to the identifying resistor 34. The
other end of the identifying resistor 34 is connected to a DC voltage
source 42 through a first resistance R.sub.1. The microprocessor
44 is provided with a second connection through a resistor R.sub.2,
and a noise suppression and protection circuit provided by a pair
of capacitors 46 and 48. As shown also, the microprocessor 44 preferably
communicates with a look-up table 45. The voltage supplied by the
source 42 is modified by the known resistance R.sub.1. Essentially,
a voltage divider is created, and the voltage sensed by the microprocessor
44 can be evaluated to determine the resistance of the identifying
resistor 34. If the sensed voltage is VD, and the resistance of
the identifying resistor 34 is RH, then the sensed voltage VD=:
VD=voltage.sub.DC*RH/(RH+R.sub.1) volts
[0016] The microprocessor preferably has a built-in analog to digital
converter that converts the voltage VD to a digital number. The
microprocessor software then utilizes the above calculation to back-calculate
the value of RH, which can then be compared to the values in a look-up
table (see FIG. 3).
[0017] If there is no match, some signal may be provided to the
installer that the heater capacity must be manually entered, such
as on display 50.
[0018] In one preferred embodiment, the voltage DC was five volts,
the R.sub.1 value is 100 kohm, and the R.sub.2 value is 10 kohm.
The capacitors 46 and 48 are values of 0.01 .mu.F and 0.1 .mu.F,
respectively. Of course, these values are merely exemplary.
[0019] The above-described circuit on the control side is also
exemplary. Many variations would be readily apparent to a worker
of ordinary skill in the electrical control art. As an example,
the analog to digital converter could be external to the microprocessor,
and rather than a voltage divider circuit, a current source circuit
could be utilized. In a current source current, a fixed known current
(IS) is sourced into the heater identifying resistor and the voltage
(VS) across it is measured. The resistor value of the identifying
resistor RH is then calculated by: RH=VS/IS
[0020] Further, while a look-up table is disclosed, the circuit
and the identifying resistance could be simply designed such that
the value VD, or RH, can be input into a mathematical formula to
compute heater capacity. With either the look-up table or this formula,
a worker of ordinary skill in the art would recognize that some
pre-determined tolerance range should be incorporated into the microprocessor
for identifying the particular heater size. Further, the microprocessor
may merely associate the initially identified voltage with the look-up
table or formula, rather than calculating the resistance.
[0021] FIG. 3 shows exemplary resistances for various sized heaters.
Of course, the invention is not limited to these particular resistances.
[0022] The capacity of the heater is used by control 26, such that
the amount of air delivered by the fan 24 is appropriate given the
capacity of the heater 22 and the demand.
[0023] Although a preferred embodiment of this invention has been
disclosed, a worker of ordinary skill in this art would recognize
that certain modifications would come within the scope of this invention.
For that reason, the following claims should be studied to determine
the true scope and content of this invention.
|