Convertible electrical distribution panel

An electrical distribution panel includes an enclosure, a first power input, a first circuit interrupter including a first terminal electrically connected to the first power input and a second terminal, a first bus electrically connected to the second terminal, a plurality of second circuit interrupters powered from the first bus, a second bus electrically connectable to the first bus through one of the second circuit interrupters, and a number of third circuit interrupters powered from the second bus. The first bus and a number of the second circuit interrupters power a number of first loads. The second bus and the number of third circuit interrupters power a number of different second loads. The electrical distribution panel is converted for operation with a second power input to power the second bus. The second power input receives power from at least one of a separately derived system, and a portable generator.

BACKGROUND

The disclosed concept pertains generally to electrical distribution panels and, more particularly, to electrical distribution panels being configured or being configurable to accommodate non-critical loads and critical loads supplied with power from a second power source in response to power from a first power source becoming unacceptable.

Electrical distribution panels, such as load centers, incorporate a plurality of circuit breakers and provide a safe and controllable distribution of electric power. Such load centers have become a common feature in both residential and commercial applications. Increasingly, such load centers are utilized in installations that incorporate, for example, an electric generator as a second power source in the event that a utility service serving as a first power source fails or becomes unacceptable.

With technological progress resulting in ever more uses for electricity, the amount of electrical power required for both residential and commercial applications has steadily increased, and this had lead to increased demand for relatively larger electric generators. Unfortunately, relatively larger electric generators present various disadvantages over relatively smaller electric generators. While smaller electric generators are typically air cooled, larger electric generators typically require a liquid cooling system with a circulation pump and radiator, thereby adding to both the costs and complexities of operating and maintaining a larger generator in comparison to a smaller generator. Larger generators also require relatively larger quantities of maintenance fluids, including lubrication oil and coolant liquid.

A known proposal for either new construction or the retrofit of existing installations involves the addition of a separate load center panel for critical circuits. This separate load center panel receives a backup power source and, also, manually switches between a utility power source and the backup power source. This can be utilized in installations that incorporate the backup power source, such as an electric generator, in the event that the utility power source becomes unacceptable (e.g., without limitation, fails; becomes unreliable; becomes unavailable). This can provide, for instance, reliable electric power for doctor's offices away from hospitals, home-based businesses and home-based chronic patient care support. For existing installations, this requires that the critical circuits be moved (e.g., rewired) from a first load center to the separate load center panel. However, it requires significant time and effort to rewire a load center in order to electrically connect a backup power source, such as an electric generator or other auxiliary power unit (APU) (e.g., a device whose purpose is to provide electrical energy), to critical circuits in, for example, residential and relatively smaller scale commercial structures.

Transfer switches are well known in the art. See, for example, U.S. Pat. Nos. 6,181,028; 5,397,868; 5,210,685; 4,894,796; and 4,747,061. Transfer switches operate, for example, to transfer a power consuming load from a circuit with a normal power supply to a circuit with an auxiliary power supply. Applications for transfer switches include stand-by applications, among others, in which the auxiliary power supply stands-by if the normal power supply should fail. Facilities having a critical requirement for continuous electric power, such as hospitals, certain plant processes, computer installations, and the like, have a standby power source, often a diesel generator. A transfer switch controls electrical connection of the utility lines and the generator to the facility load buses. In many installations, the transfer switch automatically starts the generator and electrically connects it to the load bus upon loss of utility power, and electrically reconnects the utility power source to the load bus if utility power is reestablished.

Another known proposal employs a single interlock between a main circuit breaker and a manual transfer switch. In response to loss of utility power, the user must first manually turn off any non-critical circuits, turn off the main circuit breaker, and then turn on the transfer switch. The manual sequence is reversed when utility power has returned.

Other known proposals provide mechanical interlocks between a main circuit breaker and a generator circuit breaker.

Further known proposals require that the entire load be switched from the utility power source to the generator power source. In other words, the loads are not separated into critical loads and non-critical loads.

U.S. patent application Ser. No. 12/043,514 discloses a first bus powered from a first circuit breaker and a first power input, a second bus, an automatic transfer switch including a first input electrically connected to the first bus, a second input electrically connected to a second power input, and an output electrically connected to the second bus, and a number of pairs of circuit breakers. The number of pairs of circuit breakers include a second circuit breaker powered from the first bus, a third circuit breaker powered from the second bus, a power output powered from the second and third circuit breakers, and an interlock cooperating with the second and third circuit breakers and structured to prevent both of the second and third circuit breakers from being closed at the same time.

It is known to provide a load center that can accept an automatic transfer switch.

NEC 2008, Optional Standby Systems, provides in Section 702.5(2)(a)-(b) that where automatic transfer equipment is used, an optional standby system shall comply with either: (a) the standby source shall be capable of supplying the full load that is transferred by the automatic transfer equipment, or (b) where a system is employed that will automatically manage the electrically connected load, the standby source shall have a capacity sufficient to supply the maximum load that will be electrically connected by the load management system. Hence, for an automatic transfer switch, the standby system must be able to handle the entire load that is transferred.

A suitable manual switch/interlock arrangement is used with a portable generator. This is because Article 702 of the NEC requires that a load center or panelboard cannot be simultaneously energized from two different power sources. Hence, the user must turn off a utility source input before turning on a generator source input. For example, a mechanical interlock prevents accidently backfeeding onto the utility source input since this could, otherwise, cause equipment failure, fire, or possible death due unexpected energized utility power lines. Also, portable generators are not setup to automatically start up and transfer power, which must be done manually.

In a “separately derived” system, the neutral and ground are electrically bonded together by a system bonding jumper at the generator. This neutral and ground are typically protected by a ground fault circuit interrupter (GFCI) at the generator. Failure to install the system bonding jumper correctly can result in nuisance tripping of this GFCI.

In a “non-separately derived” system, the neutral and ground are not electrically bonded at the generator. Instead, the neutral assemblies for the utility source and the generator source are electrically connected together at the load center. Failure to properly make that electrical connection could lead to equipment failure, fire, or possible death due to a floating neutral condition.

U.S. patent application Ser. No. 12/172,504 discloses an electrical distribution panel including an enclosure comprising a first compartment and a separate second compartment, a first power input, a first circuit interrupter including a first terminal electrically connected to the first power input and a second terminal, a first bus electrically connected to the second terminal of the first circuit interrupter, a plurality of second circuit interrupters powered from the first bus, a second bus electrically connected to the first bus through one of the second circuit interrupters, and a number of third circuit interrupters powered from the second bus. The first bus and the number of second circuit interrupters are structured to power only a number of first loads. The second bus and the number of third circuit interrupters are structured to power only a number of second loads. The second compartment is structured to receive an automatic transfer switch including a first input electrically connectable to the first bus, a second input electrically connectable to a second power input, and an output electrically connectable to the second bus. The automatic transfer switch is structured to selectively electrically connect one of the first and second inputs of the automatic transfer switch to the output of the automatic transfer switch. This enables a user, such as a home owner, to install an electrical distribution panel, such as, a load center panel, at the time of construction and use that load center panel as a conventional load center until, at a later date, they can afford to purchase and install a second power source (e.g., without limitation, a generator) and an automatic transfer switch. Hence, the electrical distribution panel provides a load center that is ready to receive an automatic transfer switch and operate with an automatic, standby generator of a non-separately derived power system. An automatic transfer switch kit includes an interior assembly having an automatic transfer switch and a corresponding wire harness.

Referring toFIG. 1, a load center2includes an enclosure assembly4, a trim assembly (not shown), a first interior assembly8and a second interior assembly10. As is conventional, the load center2also includes a ground bar assembly12and a number of neutral bar assemblies14. The load center2is divided into a first or upper (with respect toFIG. 1) section16containing the first interior assembly8and a second or lower (with respect toFIG. 1) section18containing the second interior assembly10. A barrier20preferably separates the first section16from the second section18. For example, the barrier20physically separates the sections16,18for UL purposes. The section18preferably meets panelboard standards under UL67, and transfer switch standards under UL1008. A wire harness22electrically connects the first interior assembly8and the second interior assembly10as will be described.

As is conventional, the load center2includes a main circuit breaker24(e.g., without limitation, two poles, 200 A). The main circuit breaker24provides power from a first power input25for a first power source (e.g., without limitation, utility; primary)26(shown in phantom line drawing) to a first bus28(e.g., without limitation, 120 VAC and/or 240 VAC) of the first interior assembly8, which first bus28includes a number of circuit breakers of which only example circuit breaker30(e.g., without limitation, two pole, 50 A) and circuit breaker31(shown in phantom line drawing) are shown. Although two-pole circuit breakers are shown, the load center2can include circuit interrupters having any suitable number of poles. The main circuit breaker24includes a number of first or line terminals27electrically connected to the first power input25and a number of second or load terminals29. The first bus28is electrically connected to the number of second or load terminals29of the main circuit breaker24. The circuit breaker30includes a number of line terminals41(e.g., without limitation, two line terminals are shown) electrically connected to the first bus28.

The first interior assembly8also includes a separate second bus32(e.g., without limitation, 120 VAC and/or 240 VAC), which second bus32includes a number of circuit breakers of which only circuit breakers33,34(shown in phantom line drawing) are shown. As will be explained, only circuit breakers, such as33,34, of the separate second bus32are employed to power critical loads. Also, only circuit breakers, such as31, of the first bus28are employed to power non-critical loads. The circuit breakers30,31operate independently from (e.g., without limitation, do not require any interlock therebetween) the circuit breakers33,34.

The wire harness22electrically connects the load terminals39of the circuit breaker30to first input terminals36of an automatic transfer switch (ATS)38of the second interior assembly10. The wire harness22also electrically connects the input terminals40of a sub-feed lug block42to the output terminals44of the ATS38. The sub-feed lug block42, thus, electrically connects the output terminals44of the ATS38to the second bus32.

As is conventional, the ATS38includes second input terminals46for receiving power from a second power input47for a second power source48(e.g., without limitation, backup; a generator; an auxiliary power unit; an uninterruptible power source).

During normal operation, the critical circuits powered from the second bus32are energized by the ATS38with power from the first power source26. As is conventional, the non-critical circuits powered from the first bus28are always energized by power, if available, from the first power source26. When the power from the first power source26is interrupted, the ATS38recognizes that loss of power, automatically starts, for example, the generator48, and energizes only the critical circuits powered from the second bus32with power from the generator48through the output terminals44of the ATS38and through the sub-feed lug block42.

Referring toFIG. 2, another load center50is shown. The load center50is similar to the load center2ofFIG. 1, except that the second interior assembly10including the ATS38and the wire harness22are not included. Instead, inFIG. 2, the branch mounted circuit breaker30(e.g., without limitation, CH250 marketed by Eaton Electrical, Inc. of Pittsburgh, Pa.) is electrically connected by jumper assembly52to the sub-feed lug block42(e.g., without limitation, CHSF2125 marketed by Eaton Electrical, Inc. of Pittsburgh, Pa.) to energize, when the circuit breaker30is closed, a number of critical circuits powered from the second bus32of the “split bus” (i.e., first bus28is electrically split apart from second bus32) interior. Other non-critical circuits are terminated as part of the first bus28of the “split bus” interior. The jumper assembly52electrically connects the load terminals39of the circuit breaker30to the input terminals40of the sub-feed lug block42. The jumper assembly52includes jumpers or wires (conductors) that supply power from the branch mounted circuit breaker30to the sub-feed lug block42. For example, these jumpers or wires electrically connect the A and B legs of the first bus28(see, for example, the load terminals39of the circuit breaker30) to the corresponding A and B legs (see, for example, the input terminals40of the sub-feed lug block42) of the second bus32.

There is room for improvement in electrical distribution panels.

SUMMARY

There remains a need for an electrical distribution panel, such as, for example and without limitation, a load center panel including a “split power bus” structure that is capable of operation with a portable generator (i.e., manual or non-automatic generator) and/or that can be configured as a “separately derived” system.

There also remains a need for such an electrical distribution panel that includes a mechanical interlock for utility and generator circuit breakers of a separate, second bus.

There further remains a need for such an electrical distribution panel that includes an additional neutral assembly, such that it can accommodate a “separately derived” system.

These needs and others are met by embodiments of the disclosed concept, which provide an electrical distribution panel structured to be converted for operation with a second power input to power a second bus, wherein the second power input is structured to receive power from at least one of: (i) a separately derived system; and (ii) a portable generator.

In accordance with one aspect of the disclosed concept, an electrical distribution panel comprises: an enclosure; a first power input; a first circuit interrupter including a first terminal electrically connected to the first power input and a second terminal; a first bus electrically connected to the second terminal of the first circuit interrupter; a plurality of second circuit interrupters powered from the first bus; a second bus electrically connectable to the first bus through one of the plurality of second circuit interrupters; and a number of third circuit interrupters powered from the second bus, wherein the first bus and a number of the plurality of second circuit interrupters are structured to power a number of first loads, wherein the second bus and the number of third circuit interrupters are structured to power a number of second loads, which are different than the number of first loads, wherein the number of the plurality of second circuit interrupters operate independently from the number of third circuit interrupters, wherein the electrical distribution panel is structured to be converted for operation with a second power input to power the second bus, and wherein the second power input is structured to receive power from at least one of: (i) a separately derived system; and (ii) a portable generator.

The electrical distribution panel may be structured to be converted for operation with the separately derived system.

The enclosure may include a number of first neutral bar assemblies and a number of second neutral bar assemblies, the number of first neutral bar assemblies and the number of second neutral bar assemblies being electrically connected together by a field-removable jumper.

The second bus may be structured to receive a first circuit breaker including a plurality of first poles with one of the first poles being structured to switch a first neutral, and a second circuit breaker including a plurality of second poles with one of the second poles being structured to switch a second neutral. The first neutral may be electrically connected to the number of first neutral bar assemblies and may be operatively associated with the first bus and the first power input. The second neutral may be operatively associated with the second power input. After the number of first neutral bar assemblies and the number of second neutral bar assemblies are electrically isolated by removing the field-removable jumper, one of the first circuit breaker and the second circuit breaker may switch one of the first neutral and the second neutral, respectively, to the number of second neutral bar assemblies.

The electrical distribution panel may be structured to be converted for operation with the portable generator.

The electrical distribution panel may be further structured to be converted for operation with the separately derived system.

The second bus may be structured to receive a first circuit breaker and a second circuit breaker; the first circuit breaker may be structured to selectively receive power from the portable generator; and the second circuit breaker may be structured to selectively receive power from the one of the plurality of second circuit interrupters powered from the first bus.

The enclosure may be structured to receive a trim assembly including a mechanical interlock structured to prevent both of the first circuit breaker and the second circuit breaker from being simultaneously closed.

The second bus may be structured to receive a fourth circuit interrupter and a fifth circuit interrupter; the fourth circuit interrupter may be structured to selectively receive power from the portable generator; the fifth circuit interrupter may be structured to selectively receive power from the one of the plurality of second circuit interrupters powered from the first bus; and the enclosure may be structured to receive a trim assembly including a mechanical interlock structured to prevent both of the fourth circuit interrupter and the fifth circuit interrupter from being simultaneously closed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As employed herein, the term “electrical distribution panel” shall mean a load center or a panelboard (e.g., without limitation, a lighting and appliance panelboard; a Class CTL enclosed panelboard).

As employed herein, the term “critical load” shall mean a load that needs to be powered from one of a primary power source and an alternate backup power source during all times or during substantially all times. Non-limiting examples of critical loads include heating, ventilation and air conditioning (HVAC) loads; sump pumps; refrigerators; freezers; alarm systems; essential loads; medical equipment; and emergency loads.

As employed herein, the term “non-critical load” shall mean a load other than a critical load. Non-limiting examples of non-critical loads include non-essential loads; non-emergency loads; and not critical loads.

As employed herein, the term “convertible electrical distribution panel” shall mean an electrical distribution panel including a “split power bus” structure that can be converted to operate with a portable generator (i.e., manual or non-automatic generator) and/or that can be converted or configured as a “separately derived” system.

The disclosed concept is described in association with a load center accepting input from a number of power sources having two legs, although the disclosed concept is applicable to any electrical distribution panel having suitable current ratings for critical and non-critical loads and accepting input from power sources having any number of legs or phases.

FIG. 2shows the ATS-ready load center50including the jumper assembly52between the first bus28and the separate second bus32. Any suitable number of branch circuits can be employed with the first bus28and/or the separate second bus32. InFIG. 2, all branch circuits, whether “critical” or “non-critical”, use the same neutral, since all of the neutral bar assemblies14are directly electrically connected together by fixed, rigid, conductive strap54at the load center50. Since the strap54is not field-removable, only a “non-separately derived” system is possible. Hence, a “separately derived” system cannot be provided.

FIG. 3shows a load center100, which is similar to the load center50ofFIG. 2, except as will be described. Unlike the load center50, the load center100includes a number (e.g., without limitation, two are shown; any suitable number) of neutral bar assemblies102and a field-removable jumper104electrically connected between one of the neutral bar assemblies14and one of the number of neutral bar assemblies102. The neutral bar assemblies102are installed proximate the separate second bus132. When installed, the field-removable jumper104permits a “non-separately derived” system to be provided as shown inFIG. 5. Conversely, when the field-removable jumper104is removed, this permits a “separately derived” system to be provided as shown inFIG. 6. Hence, the load center100can readily be converted to provide a “non-separately derived” system (FIG. 5) or a “separately derived” system (FIG. 6).

Some what similar to the load center50, the load center100includes an enclosure4′, a first power input25′, a first circuit interrupter24′ including a first terminal27′ electrically connected to the first power input25′ and a second terminal29′. A first bus128is electrically connected to the second terminal29′ of the first circuit interrupter24′. A plurality of second circuit interrupters30′,31′ are powered from the first bus128. A second bus132is electrically connectable to the first bus128through the second circuit interrupter30′. A number of third circuit interrupters33′,34′ are powered from the second bus132. The first bus128and a number of the second circuit interrupters31′ are structured to power a number of first loads. The second bus132and the number of third circuit interrupters33′,34′ are structured to power a number of second loads, which are different than the number of first loads. The number of the second circuit interrupters31′ operate independently from the number of third circuit interrupters33′,34′.

Unlike the load center50, the load center100is structured to be converted for operation with a second power input47′ which is structured to receive power from at least one of: (i) a separately derived system48″ (FIG. 6); and (ii) a portable generator48′ (FIG. 5). The separately derived system48″ (FIG. 6) can also be a portable generator.

A wide range of suitable conversion kits can be provided for the load center100depending upon user needs. Example conversion kits, which are discussed, below, in connection with Examples 1 to 5, are different from the automatic transfer switch kit of application Ser. No. 12/172,504.

Referring toFIGS. 4 and 5, a first example conversion kit includes the trim assembly106ofFIG. 4along with a generator circuit breaker108(e.g., without limitation, two-pole; 30 A; 50 A; any suitable rating) and a hold down kit110for the generator circuit breaker108. This conversion kit, when installed, provides the load center100′ ofFIG. 5. The utility circuit breaker42′, in this example, is part of the load center100ofFIG. 3. The second bus132is structured to receive circuit breakers108,42′. The generator circuit breaker108is structured to selectively receive power from the portable generator48′, and the utility circuit breaker42′ is structured to selectively receive power from the circuit interrupter41powered from the first bus128. The trim assembly106includes a mechanical interlock134structured to prevent both of the circuit breakers108,42′ from being simultaneously closed. In this example, the portable generator48′ is a non-separately derived system. The trim assembly106covers the enclosure4′ (shown in phantom line drawing inFIG. 4) ofFIG. 3.

In contrast to Example 1, the load center100ofFIG. 3is also structured to be converted for operation with the separately derived system48″ (FIG. 6). A second example conversion kit includes the trim assembly106ofFIG. 4, two three-pole circuit breakers112,114and a hold down kit116including two hold downs for the two circuit breakers112,114. The utility circuit breaker114replaces the utility circuit breaker42′ ofFIG. 3. This conversion kit, when installed, provides the load center100″ shown inFIG. 6. The three-pole circuit breakers112,114provide a switched neutral (e.g., each circuit breaker has a respective pigtail136,138, rather than a stab (not shown), for the third switched-neutral pole137,139, respectively) and are employed by the separately derived system48″. The generator circuit breaker112is structured to selectively receive power from an example portable generator, which is the separately derived system48″.

In this example, the second bus132is structured to receive the two three-pole circuit breakers112,114as shown inFIG. 6. One of the poles139of the utility circuit breaker114is structured to switch a first neutral141from the neutral bus bar14. One of the poles137of the generator circuit breaker112is structured to switch a second neutral143from the portable generator48″. The first neutral141is electrically connected to the neutral bar assemblies14and is operatively associated with the first bus128and the first power input25′ (FIG. 3). The second neutral143is operatively associated with the second power input47′. After the first neutral bar assemblies14and the second neutral bar assemblies102are electrically isolated by removing the field-removable jumper104(FIG. 3), one of the circuit breakers114,112can switch one of the first neutral141and the second neutral143, respectively, to the second neutral bar assemblies102.

Although the circuit breakers112,114are shown including three example poles (e.g., A,B,N), the disclosed concept is applicable to any suitable number of poles (e.g., without limitation, four poles; A,B,C,N).

Although the example portable generator48″ is shown, any suitable second power source, different from the first power source26′ (FIG. 3) (shown in phantom line drawing) can be employed.

The example three-pole generator circuit breaker112is connected in a backfeed arrangement as follows: generator A,B,N to load-side A,B,N, respectively; line-side A,B to second bus132A,B, respectively; and line-side N pigtail136to the lower left (with respect toFIG. 6) neutral bus bar assembly102.

The three-pole utility circuit breaker114is connected in a backfeed arrangement as follows: utility A,B (from the first bus128utility circuit breaker41′ A,B) to load-side A,B, respectively; utility N (from neutral bus bar assembly14) to the load-side N; line-side A,B to second bus132A,B, respectively; and line-side N pigtail138to the lower right (with respect toFIG. 6) neutral bus bar assembly102.

Since the two example neutral bus bar assemblies102are electrically connected together by the fixed, rigid, conductive strap140, both of the example neutral bus bar assemblies102provide termination points for the neutrals of critical loads (not shown).

The conversion kit of Example 1 can alternatively include another two-pole utility circuit breaker (not shown) of suitable rating and a corresponding hold down kit (not shown), since there is no need to switch the generator neutral leg of a non-separately derived system.

The example conversion kits of Examples 1 to 3 cover “manual” (portable generator) interlock setups. Additional example conversion kits, without interlocks, can be provided for users that wish to use an automatic transfer switch, such as38(shown in phantom line drawing inFIG. 3; see the ATS38ofFIG. 1). It will be appreciated that the load center100(FIG. 3) can be converted for such a system in a similar manner.

The example conversion kits of Examples 1 to 4 can cover a wide range of different amperages to accommodate a corresponding generator of suitable rating that the user wishes to use.

As can be seen from Examples 1 to 5, the example load center100(FIG. 3) can work with any suitable generator and any system setup, and can be field-converted, at a later date, from any one style to any other style with changes to a different user (e.g., without limitation, a different homeowner), or with changes to user requirements, priorities or power budget finances.

FIGS. 5 and 6show two branch circuit breakers108,42′ and112,114, respectively, across from each other, which function with the example interlock134ofFIG. 4. If the user (e.g., without limitation, contractor; homeowner) desires to provide a portable generator (e.g., without limitation,48′), at a later date, then a suitable manual conversion kit is employed to convert the load center100. This manual conversion kit includes the trim assembly106ofFIG. 4including a deadfront142, along with the appropriate generator circuit breaker (e.g.,108ofFIG. 5) and a suitable hold down kit (e.g.,110ofFIG. 5). The trim assembly106also includes a number of twistouts144structured to accommodate at least one of the branch circuit breakers.

Per UL67and NEC, whenever a branch mounted circuit breaker, such as the example generator circuit breaker108or the example utility circuit breaker42′ ofFIG. 5, is “backfed”, it must be physically retained by something “other than friction” and must require a “tool” to remove. A wide range of suitable brackets, clips, screws and other hold down devices can be employed. The particular type of hold down device depends upon the type of branch circuit breaker and its particular application. With this manual conversion kit, the user can then use any suitable portable generator.

The mechanical interlock134on the trim assembly106ofFIG. 4prevents energizing both the “critical” and “non-critical” loads simultaneously. The mechanical interlock134is used to prevent both of the example utility circuit breaker42′ and the example generator circuit breaker108from being on simultaneously.

The load center100(FIG. 3) leaves the user with the option for either a “separately derived” system (FIG. 6) or a “non-separately derived” system (FIG. 5). Furthermore, at a still future date, the load center100can still accommodate an automatic transfer switch, such as38(shown in phantom line drawing inFIG. 3; see the ATS38ofFIG. 1).

FIGS. 5 and 6show corresponding utility and generator circuit breakers108,42′ and112,114, respectively, installed and their respective wiring for “non-separately derived” and “separately derived” systems. The installation of different conversion kits for a manual transfer arrangement in the load centers100′,100″ permits the user to have the option of installing a relatively less costly portable generator, such as48′. These conversion kits include the mechanical interlock134ofFIG. 4and permit the user to have the options of installing either a “non-separately derived” system (FIG. 5) or a “separately derived” system (FIG. 6).

As shown inFIGS. 4-6, the example trim assembly106and interlock134permit interlocking for the “non-separately derived” system (FIG. 5) or the “separately derived” system (FIG. 6), and can be used when the user (e.g., without limitation, contractor; homeowner) considers the possibility of adding an automatic transfer switch, a corresponding wire harness and an automatic, standby generator at a later date.

The disclosed load center100can be field-converted to accept either: (1) an automatic transfer switch (ATS), such as38(shown in phantom line drawing inFIG. 3), and an automatic, standby generator48′″ (shown in phantom line drawing inFIG. 3; see the ATS38and the second power source48ofFIG. 1), or (2) a manual switch146formed by the example circuit breakers108,42′ (FIG. 5) and interlock134(FIG. 4) and a portable generator48′. Also, conversion kits can be installed to provide either “non-separately derived” (FIG. 5) or “separately derived” (FIG. 6) systems simply by using a different conversion kit.

The first power input25′ ofFIG. 3is structured to receive a primary power source, such as26′, and the second power input47′ (FIG. 5) is structured to receive a backup power source, such as48′.

The primary power source26′ is a utility power source, and the backup power source48′ is one of a portable generator, another generator different from the portable generator, an auxiliary power unit, and an uninterruptible power source.

The loads (not shown) powered from the second bus132are critical loads selected from the group consisting of a heating, ventilation and air conditioning load; a sump pump; a refrigerator; a freezer; an alarm system; and a medical device.

The first power input25′ and the second power input47′ both include a first power leg (A) structured to receive a first power phase and a second power leg (B) structured to receive an opposite second power phase.