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.
The invention claimed is:
1. An electric heater and fan combination comprising: an electric
heater having any one of several available capacities, and having
an identifying characteristic to be automatically reported to a
control, said identifying characteristic being associated by said
control with said one of said available capacities; a fan for delivering
air over said electric heater, said fan also being under the control
of said control; and said control receiving said identifying characteristic
from said electric heater, and associating said identifying characteristic
with said one capacity, and using said one capacity to provide control
over said heater and said fan.
2. A combination as set forth in claim 1, wherein said identifying
characteristic is an electrical signal.
3. A combination as set forth in claim 2, wherein said identifying
characteristic is provided by an identifying resistor, with distinct
resistances being provided to associate each of said several available
capacities to said control.
4. A combination as set forth in claim 3, wherein said control
provides a voltage source through a voltage divider to said identifying
resistor, and said control evaluates a voltage across said voltage
divider to determine the resistance of said identifying resistor.
5. A combination as set forth in claim 4, wherein said control
compares said identifying characteristic to a look-up table of potential
6. A combination as set forth in claim 1, wherein said control
is provided with a signal to instruct an operator to manually enter
said capacity of said electric heater if said control cannot associate
said identifying characteristic with one of said available capacities.
7. A combination as set forth in claim 1, wherein said control
further receives a signal from a thermostat to provide a demand,
and said control determining operation levels for said fan and said
heater based upon said demand.
8. A method of providing heated air into an environment comprising
the steps of: (1) providing an electric heater, and a fan for delivering
air over said electric heater, and ten into an environment to be
heated, and providing an electronic control to control said electric
hearer and said fan; (2) connecting said electric heater to said
fan, and providing information from said electric heater to said
control of a capacity of said electric heater; (3) associating said
provided information with a capacity of said fan from information
previously stored at said control; and (4) utilizing said control
to control said fan based upon said determined capacity.
9. A method as set forth in claim 8, wherein said provision of
information in step (2) occurs by electrically connecting said electric
heater to said control, and sending an electric signal from said
electric heater to said control.
10. A heating, ventilating and air conditioning system, comprising:
a utility device having any one of several available capacities,
and having an identifying characteristic to be reported to a control
without manual intervention, said identifying characteristic being
associated by said control with said one of said available capacities;
and said control receiving said identifying characteristic from
said utility device, and associating said identifying characteristic
with said one capacity, and using said one capacity to provide control
over said utility device.
11. The system of claim 10, wherein said identifying characteristic
is provided by an identifying resistor, with distinct resistances
being provided to associate each of said several available capacities
to said control.
12. The system of claim 11, wherein said control provides a voltage
source through a voltage divider to said identifying resistor, and
said control evaluates a voltage across said voltage divider to
determine the resistance of said identifying resistor.
13. The system of claim 12, wherein said control compares said
identifying characteristic to a look-up table of potential values.
BACKGROUND OF INVENTION
This invention relates to an electric heater that carries an identifying
characteristic to communicate the capacity of the electric heater
to a control.
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.
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
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 INVENTION
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.
This information is automatically provided, that is, without manual
intervention. 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.
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 DRAWINGS
The present invention will be more fully understood by reading
the following detailed description in conjunction with the drawing,
FIG. 1 schematically shows a fan and heater combination;
FIG. 2 is a schematic wiring chart; and
FIG. 3 shows an exemplary look-up table.
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.
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.
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.
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.
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=voltage.sub.DC.times.RH/(RH+R.sub.1)
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 such as the one in FIG. 3.
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
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.
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.
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.
FIG. 3 shows exemplary resistances for various sized heaters. Of
course, the invention is not limited to these particular resistances.
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.
Although this application has been described with respect to an
electric heater, one skilled in the art would recognize that this
invention is also applicable to identifying other utility devices,
such as ventilators, humidifiers, air conditioners and the like,
in heating, ventilating, and/or air conditioning systems.
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.