Abstract:
A load center is upgraded by removing the existing load center and replacing it with a renovation load center. As the existing incoming and branch circuit wiring may not be sufficiently long enough to reach the proper terminations in the replacement load center, renovation terminal blocks are provided in the renovation load center adjacent the penetrations of the external wiring to which the incoming lines, and if necessary, the branch circuit wiring are connected. Cabling is then provided between the terminations on the renovation terminal blocks and the appropriate load center terminations. The renovation terminal block(s) can be housed in an auxiliary enclosure mounted adjacent to a main enclosure containing the load center interior or all of the components can be housed in a single renovation enclosure.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to replacing an existing load center with a renovation load center without the need for rewiring the distribution system. 
     2. Background Information 
     Load centers house the connections between the incoming lines of an electric power distribution system and the numerous branch circuits in an installation, such as a residence or light commercial or industrial facility. Overcurrent protection is provided for the branch circuits in older load centers by fuses but now in most installations by circuit breakers. Additional protection, such as surge protection, is provided in some load centers. Typically, the load center will have a main circuit breaker as well as separate breakers for each of the branch circuits. 
     The load center includes an enclosure that may be fabricated from sheet metal or molded of an insulative resin. Housed in the enclosure is a branch circuit assembly, also commonly referred to as the interior, which typically includes a pair of line buses secured by a support insulator to the rear wall of the enclosure. The fuses or circuit breakers connect each branch hot conductor to one of the line buses, or to both buses in the case of a two pole breaker. The branch circuit assembly also includes one or more neutral terminal blocks to which the branch circuit neutral conductors are secured. In some cases, such as for ground fault circuit breakers, a ground terminal block or blocks are also provided in the enclosure. 
     There comes a time when the existing load center needs to be replaced, such as where a fuse load center is replaced by a load center with circuit breakers, or for instance, where branch circuits are added or updated. Typically, in existing load centers, the incoming lines are made as short as possible. It is common for them to be too short to reach the required terminals in the replacement load center. However, the gauge of the incoming lines is large enough that it is difficult, time consuming and expensive to splice extensions onto the incoming lines. 
     There is a need, therefore, for an improved load center and method of upgrading a load center which does not require the splicing of the incoming lines. 
     SUMMARY OF THE INVENTION 
     These needs and others are satisfied by the invention which is directed to a renovation load center for a distribution system having incoming lines and a plurality of branch conductors, each including a hot conductor and a neutral conductor. The renovation load center includes an enclosure having a rear wall and a branch circuit assembly mounted in the enclosure on the rear wall with line terminals at the one end of the assembly. An incoming terminal block is provided adjacent the one end of the branch circuit assembly and has line terminations for the incoming lines. Cables engaging the line terminations connect the incoming lines to separate ones of the line terminals on the branch circuit assembly. The incoming terminal block can be mounted on the rear wall of the enclosure adjacent the line terminals on the branch circuit assembly. The branch circuit assembly can include a circuit breaker mounting assembly with the line terminals at the one end and at least one neutral/ground terminal block. An additional neutral/ground terminal block can be provided adjacent the incoming terminal block. 
     The enclosure of the load center may include a main enclosure in which the branch circuit assembly is mounted and an auxiliary enclosure in which the incoming terminal block is mounted. In this case, the cables extend from the incoming terminal block in the auxiliary enclosure to the branch circuit assembly in the main enclosure. 
     The invention also embraces the method of upgrading an existing load center by disconnecting the input lines and branch circuit conductors from the existing load center, removing the existing load center, mounting a renovation load center in place of the existing load center, providing a renovation terminal block in an enclosure of the renovation load center, connecting the incoming lines to terminations on the renovation terminal block, connecting cables from the terminals on the renovation terminal block to line terminals on the branch circuit assembly of the renovation load center, and connecting the branch circuit hot conductors and neutral conductors in the renovation load center. The renovation load center may have a single main enclosure, in which the renovation terminal block is mounted, or alternatively the renovation panel may have a main enclosure housing the branch circuit assembly and an auxiliary enclosure housing the renovation terminal block mounted adjacent to the main enclosure. In the latter case, connecting the cables includes routing the cables from the auxiliary enclosure to the main enclosure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which: 
     FIG. 1 is a front elevation view with the covers removed of a renovation load center in accordance with the first embodiment of the invention which includes a main enclosure and an auxiliary enclosure. 
     FIG. 2 is a side elevation view of the auxiliary enclosure which forms part of the renovation load center of FIG.  1 . 
     FIG. 3 is a bottom view of the auxiliary enclosure. 
     FIG. 4 is a top view of the auxiliary enclosure. 
     FIG. 5 is a front elevation view of another embodiment of the renovation load center in accordance with the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As mentioned, the renovation load center of the invention can be used as a replacement for an existing load center. Circumstances where the invention might be used include, but are not limited to, installations where an old fused load center is being replaced by a load center with circuit breakers, or an installation where an existing load center with circuit breakers is being upgraded with or without the provision for additional branch circuits. It is common, for the incoming supply lines, and in some instances the branch circuit conductors also, to be too short to extend to the terminations in a replacement load center. Typically, the incoming supply lines are of such a gauge that it is difficult to splice extensions onto these lines. While the branch conductors are commonly not of such heavy gauge, it is still also inconvenient, time-consuming and costly to splice extensions on these conductors. 
     FIGS. 1-4 illustrate a first embodiment of a renovation load center in accordance with the invention that addresses these problems. The renovation load center  1  includes a main enclosure  3  fabricated from sheet metal. This main enclosure  3  includes a center section  5  forming a rear wall  7  with integral sidewalls  9  terminating in inwardly directed, forwardly facing side flanges  11 . The main enclosure  3  further include a sheet metal top wall  13  and bottom wall  15  which are both identical to the top wall  63  described in connection with the auxiliary enclosure  53  to be described. These top and bottom walls  13  and  15  have flanges  17  by which they are secured to the center section for instance by welding or a mechanical crimping process such as the TOX LOCK™ process. Finally, the main enclosure  3  includes a cover  19  which has been removed to show the interior of the main enclosure, but is shown in phantom. As is well known, the cover typically includes the hinged door (not shown) for access to the interior. 
     The main enclosure  3  contains a branch circuit assembly  21  commonly referred to as the interior of the load center, which is secured to the rear wall  7  and includes two line buses  23  and  25  extending vertically and forming alternate, vertically aligned stabs  23   s  and  25   s  which can be engaged by line side conductors of circuit breakers. The branch circuit assembly  21  also includes notched, vertically extending circuit breaker mounting flanges  27 . Such branch circuit assemblies or interiors  21  are well known and will not be further described in detail. Miniature circuit breakers  29  engage the mounting flange  27  on one side of the assembly and one of the stabs  23   s  or  25   s.  Two miniature circuit breakers  29  can be mounted in confronting relation to stabs of the same bus  23  or  25  and to opposite mounting flanges  27 . In the arrangement shown, a two pole circuit breaker  29   m  engages adjacent stabs  23   s  and  25   s.  This breaker  29   m  is back fed through the cables  31   1  and  31   2  to energize the buses  23  and  25  and serves as a main circuit breaker for the load center. 
     Incoming lines or conductors  33  from a supply include lines  33   1  and  33   2 , neutral lead  33   n  and, in some cases, ground lead  33   g . The main enclosure  3  also includes a neutral terminal strip  35  and can contain a ground terminal strip  37 . In the installation shown, the neutral terminal strip  35  is grounded at the load center by a strap  39  which is connected to both the neutral terminal strip  35  and the ground terminal strip  37  and is also connected to the metal enclosure at the rear wall  7  by the fastener  41 . Each of the circuit breakers  29  is connected to a hot lead  43  which extends out of the enclosure to a branch circuit serving one or more loads (not shown). A corresponding neutral lead  45  from each of the branch circuits is returned to the neutral terminal strip  35 . If required a ground lead  47  can be provided from the ground terminal strip  37  for each branch circuit. The neutral terminal strip and the ground terminal strip are connected to supply leads  33   n  and  33   g , respectively. These connections will be explained in detail later. 
     As shown in FIG. 1 all of the input conductors and branch conductors penetrate the main enclosure through the top wall  13 . As mentioned, this top wall  13  is identical to the top wall  63  shown in FIG.  4 . The appropriate knockouts are used for the particular installation. Thus, the installation shown is top fed. As is well known, in some installations the load center can be bottom fed. Thus, the appropriate knockouts in the bottom wall are used for penetration of the conductors. Alternatively, the load center can be fed through the back wall at the top or bottom as shown by the various knockouts  49  in the rear wall  7 . 
     As described to this point, the main enclosure  3  with its branch circuit assembly  21  and neutral and ground terminal strips  35  and  37  is identical to a type of load center currently provided for use in new installations. In such new installations, the incoming conductors  33 , the hot leads  43 , neutral leads  45  and ground leads  47  are all long enough to be connected directly to the branch circuit assembly  21  the circuit breakers  29  the neutral terminal strip  35  and the ground terminal strip  37 . However, when such a load center is provided in a renovation, these leads are often not long enough to reach their connections within in the enclosure  3 . Therefore, in accordance with the invention, one or more terminal blocks  51  are provided at a point where they can be reached by the existing wiring including the incoming lines  33 , the hot leads  43 , neutral leads  45  and the ground leads  47 . In the embodiment shown in FIG. 1, these terminal blocks  51  are provided in an auxiliary enclosure  53  which is mounted adjacent to the main enclosure  3 . In the exemplary installation, the auxiliary enclosure  53  is mounted on top of the main enclosure  3 . 
     As can be seen from FIGS. 1-4, the auxiliary enclosure is similar in construction but smaller than, the main enclosure. Thus, the auxiliary enclosure has a sheet metal center section  55 , forming a rear wall  57 , pair of integral sidewalls  59  terminating in forward facing, inwardly directed side flanges  61 . The auxiliary enclosure has a top wall  63  shown in plain view in FIG.  4  and bottom wall  65  shown in FIG.  3 . The top wall  63  has a center knockout  67  for conduit carrying the incoming lines  33  of varying sizes and a number of other knockouts  69  any one or more of which can be removed for accommodating the branch conductors  43 ,  45 , and  47 . As can be seen from FIGS. 1,  2  and  4 , top wall has side flanges  71  which are secured to the side walls  59  and a rear flange  73  which is secured to a rear wall  57  of the center section  55 . A front flange  75  extends between the side flanges  61 . 
     The bottom wall  65  of the auxiliary enclosure  53 , which is shown in bottom plan view in FIG. 3, has side flanges  77  which are secured to the side walls  59  of the center section  55  and a rear flange  79  which is secured to the rear wall  57 . A front flange  81  extends upward along the front edge of the bottom wall  65  between the side flanges  61 . The bottom wall  65 , as shown in the bottom plan view of FIG. 3, has a large opening  83 . A pair of tabs  85  extending into the opening have apertures  87  through which fasteners (not shown) secure the auxiliary enclosure to the top of main enclosure  3 . In this manner the auxiliary enclosure  53  can easily be added in the field as needed. The auxiliary  53  also has a cover  89  shown in place in FIG. 2 but shown removed in FIG. 1 but in phantom line. 
     In the embodiment of FIGS. 1-4, the terminal blocks  51  are secured to the rear wall  57  of the auxiliary enclosure  53 . The terminal blocks  51  are of a type having insulating barriers  91  between the terminations  93  so that conductors of differing potentials can be terminated adjacent one another without the danger of arcing. As the incoming lines  33  protected by a conduit  95  are not long enough to reach their terminations within the main enclosure  3 , they are connected to terminations  93  on one of the terminal blocks  51 . Cables  31   1  and  31   2  are connected to the appropriate termination  93  and then fed through the opening  83  in the bottom wall  65  of the auxiliary enclosure  53 , through a knockout (not shown) in the top wall of the main enclosure  3  and then to the appropriate termination on the main circuit breaker  29   m.  In addition, cables  31   n  and  31   g  extend from one of the terminal blocks  51  to the neutral terminal strip  35  and ground terminal strip  37 , respectively. If any of the hot leads  43 , neutral leads  45  or ground leads  47  are too short to reach the associated circuit breaker, termination on a neutral terminal strip  35  or ground terminal strip  37 , respectively, they can be connected to a termination  93  on one of the terminal blocks  51  and a cable  97   h,    97   n  or  97   g  can be connected between that termination and the appropriate termination in the main enclosure  3 . 
     If the main enclosure is bottom fed, the auxiliary enclosure  53  can be mounted to bottom of the main enclosure  3 . 
     FIG. 5 illustrates another embodiment of a renovation load center in accordance with the invention. This renovation load center  101  has a single enclosure  103  also fabricated from sheet metal. The center section  105  has a rear wall  107 , side walls  109  and front facing side flanges  111 . The enclosure  103  also has a top wall  113  and bottom wall  115  secured to the center section  105  in a manner similar to that described above in connection with the embodiment of FIGS. 1-4 and each having a front flange  117 . A cover (not shown) is secured to the flanges  111  and  117  and has a hinged door for access to the interior of the enclosure as is well known. 
     The branch circuit assembly  121 , also known as the interior, has a first line bus  123  with stabs  123   s  and a second line bus  125  with stabs  125   s  alternating with the stabs of  123   s.  Notched circuit breaker mounting flanges  127  extend vertically along each side of the branch circuit assembly  121 . A two pole main circuit breaker  129   m  has one pole connected between the first line bus  123  and a first line bus terminal  123   t.  Similarly, the second pole of the main circuit breaker  129   m  is connected between the second line bus  125  and a second line bus terminal  125   t.  A plurality of miniature circuit breakers  129  engage half of one of the stabs  123   s  or  125   s  and one of the circuit breaker mounting flanges  127 . 
     The main enclosure  103  also includes a neutral terminal strip  135  and ground terminal strip  137 . The neutral terminal strip  135  is grounded at the load center by a strap  139  which is connected to both the neutral terminal strip  135  and the ground terminal strip  137  and is secured to the metal enclosure at the rear wall  107  by the fastener  141 . 
     The incoming lines  133  include lines  133   k  and  1332 , neutral  133   n  and in some cases ground  133   g . For each branch circuit served by one of the circuit breakers  129  there is a hot lead  143 , a neutral lead  145  and a ground lead  147 . As any or all of these external conductors may not be long enough to extend to their connections within the enclosure  103 , one or more terminal blocks  151  are provided adjacent the point of penetration of the enclosure  103  by these external lines. Thus in the embodiment shown where the incoming lines and the branch circuit lines are all fed through the top of the enclosure  103 , a pair of renovation terminal blocks  151 , are provided on the back wall  107  adjacent the top of the enclosure  103 . A cable  1311  connects the incoming line  133   k  through a termination  93  on one of the renovation terminal blocks  151  to the terminal  123   t  for the first line bus  123  of the branch circuit assembly  121 . Similarly, a cable  1312  connects the incoming line  1332  to the second line bus terminal  125   t , while cable  13  in connects the line  133   n  to the neutral terminal strip  135  and the lead  131   g  connects the ground conductor  133   g  to the ground terminal strip  137 , all through terminations  93  on one of the terminal blocks  151 . Also, if the branch circuit conductors  143 ,  145  or  147  are not long enough to reach the circuit breaker  129 , or the appropriate terminal strip  135 ,  137 , then conductors  197   h ,  197   n  and  197   g . respectively, can connect these branch circuit conductors to the appropriate terminations through a termination  93  on one of the renovation terminal blocks  151 . 
     While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.