US3267255A

US3267255A - Forced air electric baseboard heater

Info

Publication number: US3267255A
Application number: US341215A
Authority: US
Inventors: Albert E Schulz
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1964-01-30
Filing date: 1964-01-30
Publication date: 1966-08-16
Anticipated expiration: 1983-08-16
Also published as: CH426158A; DE1540782C3; JPS44819Y1; GB1088030A; DE1540782A1; NL6500961A; DE1540782B2; ES308091A1

Description

Aug. 16, 1966 A. E. SCHULZ FORCED AIR ELECTRIC BASEBOARD HEATER 2 Sheets-Sheet 1 Filed Jan. 30, 1964 m #7.? 4177mm Aug. 16, 1966 A. E. SCHULZ 3,267,255

A FORCED AIR ELECTRIC BASEBOARD HEATER Filed Jan. 30, 1964 2 Sheets-Sheet 2 z gg w I R y x? @l x s I G SO n & v w Q Q Q w W 2 m2 f/Wama/ United States Patent 3,267,255 FORCED AIR ELECTRIC BASEBOARD HEATER Albert E. Schulz, Fairfield, Conn, assignor to General Electric Company, a corporation of New York Filed Jan. 30, 1964, Ser. No. 341,215

8 Claims. (Cl. 219-370) This invention relates to electric heating apparatus and more specifically to a forced air, electric baseboard heater, i.e., a heater adapted to be positioned at the base of a wall.

So as to be relatively unobtrusive within a room, it is desirable that electric baseboard heaters have a long, low and shallow shape. Until recently, the majority of electric baseboard heaters being sold were of the non-forced air type and relied primarily on convection to obtain circulation of the heated air. One major disadvantage of such heaters is that the heat naturally tends to move directly upwardly and the occupants of the room do not feel the benefit of the heat unless they are standing directly over the heater or until the temperature of the entire room has been raised.- Incorporating a fan in the heater to direct the air horizontally away from the heater in a direction parallel to the floor tends to alleviate this problem. With forced air electric heaters it is highly desirable that the heated air be provided in an even blanket, spreading over the floor. If the heat is uneven, the occupants of the room are subjected to uncomfortable hot and cold air flows in the area of the heater; and equally as important, the heater is probably not operating efiiciently in that certain portions of the heating elements are likely to be significantly hotter than other portions.

It is a primary object of this invention to provide an improved forced air electric baseboard heater having a smooth even heat output throughout the length of its air outlet.

It is a further object of this invent-ion to provide a forced air electric baseboard heater with an improved low cost construction which is easy to assemble and manufacture.

In accordance with one form of this invention, a forced air electric heater is provided having a horizontally elongated housing with a centrifugal fan and electric motor therefor mounted in one end of the housing. A fan scroll is positioned around the fan; and a horizontally, elongated duct is located in the housing and connected to the scroll air outlet. Within the duct there is positioned an elongated electric heating element. Elongated air outlet means are formed in the housing adjacent to and parallel with the duct and a plurality of spaced openings are formed in the duct and positioned in direct communication withthe housing air outlet. These openings are sized and arranged with relation to the size of the duct, the characteristics of the heater and the output of the fan to obtain a relatively even heat output throughout the length of the elongated housing outlet.

Other objects and advantages of this invention will be apparent from the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a front partially sectionalized, elevational view of the baseboard heater of the invention;

FIG. 2 is a perspective View of the heater showing the entering and leaving air flow;

FIG. 3 is a top cross-sectional view along lines 3-3 of FIG. 1;

4 FIG. 4 is a cross-sectional view of the heater along line 4--4 of FIG. 1; and

FIG. 5 is a perspective view of the heater heating element and associated structure.

Referring now to the drawings, the heater shown therein includes an external housing having a rear wall 12,

3,267,255 Patented August 16, 1966 "ice a bottom wall 14, a front wall 16, a top wall 18 and

end walls

20 and 22. The front wall 16 has a lower and an upper vertically oriented

portion

24 and 26, with portion 2 6 being positioned above and outwardly from portion 24. These vertically oriented portions are connected by a horizontally extending wall 28 having a plurality of elongated openings 30, as shown in FIG. 2, which permit the entry of air to the housing. Such an arrangement of the air intake uniquely conceals the openings 30, but yet permits the heater to be positioned on the floor adjacent a wall of the room. Having the intake so positioned also insures thatthe colder air adjacent the floor of a room isdrawn into the heater.

' In the upper portion 26 of front wall 16, there is formed an elongated rectangular air outlet 31. To prevent objects from being inserted into the interior of the housing, the outlet 31 is covered by a protective grill 32.

So that the heater will be relatively unobtrusive, it is given an elongated shallow shape to conveniently fit adjacent the baseboard of a room. A pair of front legs 33 provide additional stability to the heater and the protective tips 34 on the legs in conjunction with the insert supports 35 prevent the metal housing from scratching the surface upon which the heater rests. A handle 36 at tached to the top wall 18 enhances the portability of the heater by allowing it to be easily lifted and carried to the desired location.

A motor 38 driving a centrifugal fan 40 is positioned within one end of the heater housing 10. More specifically, the motor is attached to a supporting strap 42 mounted on an orifice plate 44, which is, in turn, secured to a fan scroll 46 surrounding the fan 40. Scroll 46 is welded or otherwise secured to rear wall 12 through scroll flange 46a. Orifice plate 44 is provided with a central opening through which air may flow past the motor into the fan, and scroll 46 has an air outlet section 46b tangentially positioned with respect to the fan in the upper portion of the housing.

In accordance with the invention there is provided an elongated duct or tunnel 48 positioned in the upper portion of housing 10 with one end in direct communication with scroll outlet 46b. As can be seen from the drawings, the duct 48 has a rectangular cross-section formed by upper and lower walls 50 .and 52, a portion of the rear wall 12, and an apertured front wall 54.

Walls

50 and 52 are each provided with a right angle flange 50a and 52a to facilitate securing the walls to rear wall 12. Front wall 54, which is spaced slightly from grill 32, has a shallow U-shaped cross-section adapted to fit partially over

walls

50 and 52. A plurality of lugs 56 integrally formed with

walls

50 and 52 extend through mating slots 58 formed in front wall 54 to align the front .wall with respect to the upper and

lower walls

50 and 52; and by deforming the lugs, the front wall may be securely attached to the upper and lower walls. Integrally formed with the front wall 54 is .an end wall 60 also having a pair of slots for mating with lugs extending from the upper and

lower walls

50 and 52.

Front wall 54 is provided with a plurality of holes or apertures 62 which permit the air from the fan to flow out of duct 48. Since the duct is completely closed except for the apertures in the front wall and except for the intake end of the duct connected to the scroll outlet 46b, all .air is directed forwardly through the apertures 62 in a direction parallel to the floor or other surface upon which the heater is supported. The combined cross-sectional area of the apertures 62 is related to the air output of the fan in a manner such that there is .a slight pressure build up within duct 48. Hence, the duct maybe considered as a plenum chamber for the fan. As a result of the pressure'build up within the plenum chamber, the

air tends to flow evenly from the various air holes 62 as jet streams into the room. In the absence of such a pressure build up, the majority of the air would tend to flow out of the openings adjacent the end wall 60. The further significance of this pressure build up and the sizing of the apertures 62 will be later discussed in greater detail.

Within the duct 48, there is positioned an elongated heating coil 64 which extends throughout substantially the entire length of the duct. The ends of the heating coil 64 are attached to suitable lead wires (not shown) which are in turn secured to supports 66 and 68 made of ceramic or other insulating material. Since the coil is resilient and relatively stiff, it may be placed under axial tension so that it is supported by simply the two end supports 66 and 68. However, to prevent possible sagging of the wire during heating, there are provided intermediate ceramic supports or

guides

69, 70 and 71. As best seen in FIG. 5, each of these intermediate supports is provided with a central enlarged aperture through which the heating coil extends. The coil is only loosely positioned within the intermediate supports so that it is free to move axially. As can be seen in FIG. 5, all of the ceramic supports have upper portions which extend through openings in the duct bottom Wall 52 and are secured in this position by a retaining wire 72, which cooperates with notches formed in the base of each support to hold the bases in contact with the lower surface of wall 52. The retaining wire is held in position by ex- [tending through deformed portions in wall 52.

A unique advantage of the heating element arrangement is that the coil is somewhat self adjusting. For example, in the event a portion of the coil should overheat due, for example, to partial blockage of the air flow, the overheated portion will lose some of its strength and resiliency and the tension on the coil will cause the overheated portion to be axially elongated. This reduction of the quantity of heated wire in that area natural ly reduces the heat concentration in that area, thus automatically tending to alleviate the difliculty.

As can be seen by the arrows in the drawings, the air enters the heater through inlet ports 30 and is drawn through the orifice in orifice plate 44 into the fan; the fan output is forced through the apertures 62 in duct 48 and out of the heater through elongated opening 31. Note that the opening extends in parallel relation with the duct 48 throughout substantially the entire length of the duct; thus, providing a direct unobstructed air flow from the duct.

To obtain an even heat output throughout the length of outlet 31, it is necessary to have approximately the same amount of air flowing through each of the air holes 62. As previously explained, the pressure build up within the plenum chamber or duct 48 helps greatly to provide the even air flow. However, in view of the considerable length of the duct, it has been found that the heat distribution is improved when outlet holes 62 are made of varying diameters. More even heat distribution is obtained by forming the holes in the upstream end of duct 48 with slightly larger diameters than the outlet holes at the downstream end of the duct. With the particular length of heater shown in the drawings, the heat distribution is further improved by utilizing two holes of the larger diameter size near the downstream end of the duct, as can be seen in FIG. 1.

Still referring to FIG. 1, note that the outlet holes 62 in the upstream end of duct 48 are on a centerline approximately coincident with the centerline of coil 64, whereas the holes in the downstream end are on a line slightly below the coil centerline. It has been found that this arrangement provides superior results to that obtained when all holes are aligned on the coil centerline.

In the particular arrangement shown, duct 48 is approximately 22 to 23 inches in length. There are ten outlet holes in the upstream end of the duct, each having a diameter of approximately one-half inch. There are eight smaller holes in the downstream end of the duct having a diameter of approximately three-eighths of an inch. In addition,

apertures

76 and 78 which are adjacent to the last hole in the downstream end of the duct are of the one-half inch diameter in size. The centerline of

holes

76 and 78 and the eight smaller holes is located approximately one eighth inch below the centerline of the ten upstream holes. The air output of the fan is of course a critical factor in determining the pattern for the outlet holes 62. The air delivery of the particular unit illustrated in the drawings is approximately 140 cubic feet per minute in free air.

While the various air outlet holes 62 can be sized and arranged to provide a relatively even air flow, it has been found that if all of the air which passes through the downstream holes has first been heated by the upstream portions of the heater, the resulting temperature of the air is higher than desired. To overcome this problem, there is provided a baffie positioned Within the upstream end of duct 48 between heater 64 and rear wall 12 and being slightly greater than one-third the length of the duct. The baffie may be secured in this position by being welded or otherwise suitably attached to the upper and

lower walls

50 and 52. As can be seen from FIG. 3, a portion of the air from fan 40 flows through the passage formed between the baflle 75 and the rear wall 12, thereby bypassing the upstream portion of the heater. Consequently, this air which then passes over the downstream portion of the heater and through the downstream air outlet holes is basically heated solely by the downstream portions of the heater. Therefore, the temperature of this heated air does not reach an objectionable level. The portion of the air output which flows in front of bafile 75 tends to leave the duct 48 before reaching the downstream end of the duct since such air is always flowing adjacent to some of the air outlet holes 62. In other words, the baffle 75, generally speaking, controls the air flow such that the bulk of the air is heated solely by only a portion of heater 48 with the result that even heat distribution from the heater is obtained.

In a longer production version of the heater, the duct 48 is approximately twenty eight and one-half inches long and is provided with eighteen holes of the one-half inch size, with sixteen of the holes being on the upstream half of the duct and the other two one-half inch size holes being the last two holes in the downstream end of the duct. Eight of the smaller three-eighths of an inch diameter size holes are formed in the duct between the upstream holes and the two holes at the far end of the duct. The baffle employed is also correspondingly longer. Naturally, if the duct is formed of other various lengths or if some of the other factors in the system are changed, such as the air output of the fan, the diameter and location of the outlet openings can be varied accordingly.

To control the operation of the heater, there are provided two thermostats. A first thermostat 80 is located in the scroll outlet section 4611 to sense the temperature of the air entering the heating chamber. The shaft of this thermostat extends through the front wall 16 and has an indicator knob 82 attached thereto for controlling the temperature in turning the heater on and off. Suitable markings surrounding the knob 82 may be provided to indicate the heater setting. The other thermostat84 is located on the underside of duct wall 52 midway between the ends of the duct to sense the duct temperature and to shut the heater off when the temperature rises above a predetermined level. Thermostat 84 will normally not operate to shut off the heater unless a portion of the air flow is blocked or restricted so as to cause an overheat condition.

With the heater construction which has been described, it will be appreciated that a smooth evenly heated air flow is obtained. Moreover, it should be noted that the components are arranged to provide an easily assembled low cost construction. In this connection, note that all of the components such as motor, fan, scroll, and outlet duct are all mounted directly to back wall 12 of the housing. Such an arrangement simplifies manufacturing and the assembly problems.

While there has been shown and described a particular embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention; therefore, it is intended in the appended claims to cover such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A forced air electric baseboard heater comprising: a horizontally elongated housing adapted to be positioned at the base of a wall; a centrifugal fan and electric motor therefor mounted in one end of said housin a fan scroll positioned around said fan having an air inlet and an air outlet; an air inlet formed in said housing for permitting air to flow to said scroll air inlet; a horizontally elongated duct positioned in said housing having an end disposed "adjacent said fan and connected to said scroll outlet; an elongated electric heating means positioned in said duct extending substantially the full length thereof; elongated air outlet means formed in said housing positioned adjacent to and parallel with said duct; and a plurality of spaced openings formed in said duct along the length thereof and positioned in direct communication with said housing air outlet; said openings having a predetermined total area relative to the air out-put of said fan to maintain a pressure differential above atmospheric in said duct throughout its full length, the area of said openings per unit length of said du'ct being greater in the portion thereof disposed adjacent the fan than in the portion adjacent.

the opposite end of said duct.

v2. A forced air electric baseboard heater comprising: a horizontally elongated housing to be positioned adjacent the base of a wall; a centrifugal fan and electric motor therefor mounted in one end of said housing; a fan scroll positioned around said fan having an axial air inlet and a tangential air outlet; an air inlet formed in said housing for permitting air to flow to said scroll air inlet; a horizontally elongated duct positioned in said housing spaced from the front and top walls, said duct having an end disposed adjacent said fan and in communication with said scroll outlet; an elongated electric heating coil positioned in said duct extending substantially the full length thereof; an elongated air outlet formed in the front wall of said housing positioned adjacent to and parallel with said duct; a plurality of spaced openings formed in said duct along the length thereof positioned in direct communication with said housing air outlet; said openings having a predetermined total area relative to the air output of said fan to maintain a pressure differential above atmospheric in said duct throughout its full length, the area of said openings per unit length of said duct being greater in the portion thereof disposed adjacent the fan than in the portion adjacent the opposite end of said duct.

3. A forced air electric heater comprising: a horizontally elongated housing; a fan and electric motor therefor mounted in one end of said housing; an air inlet formed in said housing for permitting air to flow to said fan; a horizontally elongated plenum chamber positioned in said housing having an end disposed adjacent said fan and connected to receive the air output of the fan; an elongated electric heating means positioned in said chamber extending substantially the full length thereof; an elongated air outlet formed in said housing positioned adjacent to and parallel with said chamber; a plurality of circular openings formed in the front wall of said chamber and spaced along the length of said heater in direct communication with said housing air outlet; said openings having a predetermined total area relative to the 6 air output of said fan to maintain a pressure differential above atmospheric in said duct throughout its full length, the area of said openings per unit length of said duct being greater in the portion thereof disposed adjacent the fan than in the portion adjacent the opposite end of said duct.

4. A forced air electric heater comprising: a horizontally elongated housing; a centrifugal fan and electric motor therefor mounted in one end of said housing; a fan scroll positioned around said fan and having an air inlet and an air outlet; air inlet means formed in said housing for permitting air to flow to said scroll air inlet; a horizontally elongated duct positioned in said housing having an end disposed adjacent said fan and connected to said scroll outlet; an elongated electric heating element in the shape of a helically Wound coil extending throughout substantially the entire length of said duct, a plurality of insulated supports secured at spaced locations to said duct for supporting said heating element, each of said supports including end supports attached to the ends of said heating element, said support-s intermediate the end supports having an opening (for loosely receiving the coil heating element whereby the element is supported but is yet free to move axially; means defining a plurality of air outlet openings in the front wall of said duct and positioned in spaced relation along the length of said duct; said openings having a predetermined total area relative to the air output of said fan to maintain a pressure differential above atmospheric in said duct throughout its full length, the area of said openings per unit length of said duct being greater in the portion thereof disposed adjacent the fan than in the portion adjacent the opposite end of said duct; and air exhaust means formed in said housing and positioned adjacent to and in direct communication with the duct air outlet openings.

5. The electric heater set forth in claim 4 wherein said end supports have a predetermined spacing therebetween which is greater than the unstretched length of said helically Wound coil heating element, said coil being normally maintained in axial tension by said end supports and moving axially in said intermediate supports in response to variations in the strength and resiliency of the coil caused by heating thereof.

6. A forced air electric baseboard heater comprising: a horizontally elongated housing adapted to be installed at the base of a wall; a centrifugal fan and electric motor therefor mounted in one end of said housing; air inlet means formed in said housing for permitting air to flow to said fan; an elongated plenum chamber horizontally positioned in said housing having an end connected to said fan to receive the air output of said fan; an elongated electric heating element centrally positioned within said plenum chamber and extending substantially the full length thereof; air outlet means formed in one wall of said plenum chamber along the length of said heating element; an elongated air outlet formed in said housing adjacent to and in direct communication with said plenum chamber outlet means; bafi'le means disposed in a portion of said plenum chamber adjacent said fan between said heating element and a Wall of said plenum chamber opposite said one wall, said bafile means being spaced from said Wall of said plenum chamber opposite said one Wall to form a flow passage so that a portion of the air from said fan bypasses a portion of said heating element adjacent said fan and is ducted directly to a portion of said heating element more remote from said fan, whereby even heat distribution is obtained.

7. A forced air electric baseboard heater comprising: a horizontally elongated housing adapted to be installed at the base of a wall; a centrifugal fan and electric motor therefor mounted in said housing; air inlet means formed in the [front wall of said housing for permitting air flow to said fan; an elongated plenum chamber horizontally positioned in said housing having an end connected to said fan to receive the air output of said fan, said plenum chamber havinga front wall spaced from said housing front Wall and a rear wall; an elongated electric heating element positioned Within said plenum chamber and extending throughout the length of the chamber; air outlet means formed in the front wall of said plenum chamber and in the adjacent opposed portion of the front wall of the housing along the length of said heating element; and a baffle plate disposed in a portion of said plenum chamber adjacent said fan between the rear wall of the plenum chamber and said heating element, said baffile plate being spaced from the rear Wall of said plenum chamber to define an air flow passage therebetween extending along at least one third the length of said duct so that a portion of the air from said fan bypasses the one third of said heating element adjacent said fan and is ducted to flow over a portion of said heating element remote from said fan.

8. A forced air electric baseboard heater comprising: a horizontally elongated housing adapted to be positioned at the base of a wall; said housing including a front wall having a first vertically oriented portion adjacent the lower edge of the wall and a second vertically extending portion positioned above and outwardly from said first portion with a generally horizontally extending wall connecting the two vertically oriented portions; a centrifugal fan 25 and electric motor therefor mounted within one end of said housing; a fan scroll surrounding said fan having 8 an axial air inlet and a tangential air outlet; air inlet means'forrned in said horizontal wall portion for permitting air to flow to said scroll air inlet; a horizontally elongated plenum chamber positioned in said housin 8 above said horizontal wall having an end disposed adjacent said fan and connected to said scroll outlet; elongated electric heater means positioned in said chamber extending substantially the full length thereof; air out-let means formed in said chamber extending along the length thereof; and air outlet means formed in said second vertically extending portion of said front wall directly communicating with said air outlet means of said chamber.

References Cited by the Examiner RICHARD M. WOOD, Primary Examiner.

ANTHONY BARTIS, Examiner.

Claims

1. A FORCED AIR ELECTRIC BASEBOARD HEATER COMPRISING: A HORIZONTALLY ELONGATED HOUSING ADAPTED TO BE POSITIONED AT THE BASE OF A WALL; A CENTRIFUGAL FAN AND ELECTRIC MOTOR THEREFOR MOUNTED IN ONE END OF SAID HOUSING; A FAN SCROLL POSITIONED AROUND SAID FAN HAVING AN AIR INLET AND AN AIR OUTLET; AN AIR INLET FORMED IN SAID HOUSING FOR PERMITTING AIR TO FLOW TO SAID SCROLL AIR INLET; A HORIZONTALLY ELONGATED DUCT POSITIONED IN SAID HOUSING HAVING AN END DISPOSED ADJACENT SAID FAN AND CONNECTED TO SAID SCROLL OUTLET; AN ELONGATED ELECTRIC HEATING MEANS POSITIONED IN SAID DUCT EXTENDING SUBSTANTIALLY THE FULL LENGTH THEREOF; ELONGATED AIR OUTLET MEANS FORMED IN SAID HOUSING POSITIONED ADJACENT TO AND PARALLEL WITH SAID DUCT; AND A PLURALITY OF SPACED OPENINGS FORMED IN SAID DUCT ALONG THE LENGTH THEREOF AND POSITIONED IN DIRECT COMMUNICATION WITH SAID HOUSING AIR OUTLET; SAID OPENINGS HAVING A PREDETERMINED TOTAL AREA RELATIVE TO THE AIR OUTPUT OF SAID FAN TO MAINTAIN A PRESSURE DIFFERENTIAL ABOVE ATMOSPHERIC IN SAID DUCT THROUGHOUT ITS FULL LENGTH, THE AREA OF SAID OPENINGS PER UNIT LENGTH OF SAID DUCT BEING GREATER IN THE PORTION THEREOF DISPOSED ADJACENT THE FAN THAN IN THE PORTION ADJACENT THE OPPOSITE END OF SAID DUCT.