The enclosure is fabricated of not less than 11 gauge mild steel with the necessary angle and/or channel base frame for regulator support. Units may also be constructed from 304 stainless steel, 316 stainless steel or aluminum. Each section shall be provided with a minimum of 4 lifting lugs for shipping and lifting the unit. All roofs are crowned with rain troughs between sections for proper water drainage.
All corners are formed and welded which are then ground smooth. All hardware is cadmium plated and each compartment shall have hinged doors which shall be external panel mounted to the door and to the enclosure. The door is removable from the open position. All doors have stop latches and "Eberhard" or equal door locks and handles with 3-point latches.
Enclosure is rated NEMA 3R equivalent, which protects the regulators and switches from rain and weather. NEMA 3R – Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet, and snow; and that will be undamaged by the external formation of ice on the enclosure.
Many colors are available which include Ansi 61 Gray, Ansi 70 Gray and Munsell Green to name a few. Paint colors can even be matched to existing units given the color number or paint chip. All Gilbert enclosures go through the same rigorous painting process. First the unit shall be thoroughly scraped and sanded to remove any burrs or welding spatter. The steel shall then be cleaned and phosphatized under 1800 PSI fluid pressure and treated at 2580F at a distance of 6 inches. Phosphoric acid shall be Fremont #658 applied at 3/4 of 1% by volume of water. Unit shall be allowed to dry for 30 minutes.
A red oxide modified alkyd primer shall be applied to unit in an even, thorough coat. Wet primer thickness shall be 3.0 - 4.0 mils. Dry primer thickness shall be 1.2 - 1.6 mils. A minimum period of one - two hours should be allowed for prime to dry before recoating.
A modified silicone acrylic alkyd enamel shall be applied a minimum of one - two hours after the primer has been applied to insure proper bonding. After the first coat is applied allow a minimum of 2 hours before recoating. After additional coat is applied allow a minimum of 2 hours before handling the unit. Minimum dry total thickness is 3.0 mils; desired dry total thickness is 3.5 mils.
Paint meets tests specified in ANSI C57.12.28-1998.
There are many ways to customize your order in lieu of different sizes. Items such as protective barriers behind each door, penta head door handles, dead front, live front, etc. Since different needs require different enclosures, table 1 below is a list of options that may guide you in constructing you own custom enclosure.
The first two options in table 1 are door handles. Standard Eberhard door handles are provided unless replaced by these options. The following four options are protective barriers. Utilities, electric companies, and REA sometimes require these protective barriers, which are located directly behind the door. All barriers are Nema and IEEE compliant.
The final two options are windows in the doors and no venting. If ordering a window in the doors please specify how many doors must have windows in them by adding a number immediately after the –W.
Table 1 - Options |
| Code |
Description |
| 0 |
Penta Head Door Handles |
| 0 |
Hex Head Door Handles |
| -B2G (GPO-3 Fiberglass) |
40" Hinged Door Barrier |
| -B2L (Lexan) |
40" Hinged Door Barrier |
| -L2G (GPO-3 Fiberglass) |
40" Lift-out Door Barrier |
| -L2L (Lexan) |
40" Lift-out Door Barrier |
| -W# (number of doors with) |
Window for Door |
| -NV |
No Venting |
Specifications for Gilbert Electrical Systems Pad-Mounted Metal Enclosure
1.0 Scope
This specification covers the design and construction of factory assembled pad-mounted metal enclosures.
2.0 Construction
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2.1 Enclosure to be tamper resistant and weather resistant. There are to be no exposed screws or bolts.
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2.2 Enclosure to be constructed of a minimum of 11 gauge mild steel.
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2.3 Enclosure to be of bolted construction.
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2.4 Enclosure design to utilize welded spreader frames at top and bottom.
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2.5 All panels and doors to have formed edges.
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2.6 All external fasteners to be stainless steel.
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2.7 Roof to be domed to shed water.
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2.8 Construction to allow additional unit(s) to be added on to the existing enclosure at a later date.
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2.9 Enclosure to be shipped completely factory assembled with lifting provisions. When specified, the assembly is to be mounted on a 4" steel channel skid with lifting provisions.
3.0 Doors
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3.1 All door openings to be a minimum of 40" square. Larger sizes are available.
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3.2 A recessed penta-head bolt to be provided on all doors when specified. Dead-front construction to be provided when specified.
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3.3 Two doors to be provided on each unit as a standard. Side panels may be substituted for doors when requested.
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3.4 Door hinge to have a minimum of 0.375" diameter stainless steel.
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3.5 Doors to have a positive 3-point latching mechanism.
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3.6 Door handles to be capable of accepting a padlock handle to have 0.312" square shaft.
4.0 Venting
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4.1 Enclosure to have adequate venting to dissipate the heat of the enclosed equipment.
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4.2 Vent openings to be covered on inside with perforated aluminum screen.
5.0 Painting
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5.1 Red Oxide Primer.
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5.2 Paint to be silicone enamel. Color to be green, Munsell # 7GY3.2/1.5.
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5.3 Paint thickness to be 3.0 mils minimum after drying.
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5.4 Paint must meet ANSI standard C57.12.28-1988.
Unless to difficult to ship, the units shall be factory assembled. When shipped, units are wrapped in cardboard sheeting then plastic wrapped for weather resistance. Units are then placed on a wooden pallet for easy lifting from the bottom. If lifting from the bottom is not desired unit may be lifted by the lifting lugs. Lifting lugs are located at the base where lifting plates may be attached for lifting by crane. Lifting attachments are not provided and must be supplied by others.
Each unit is provided with an Operating and Maintenance Manual to allow users to perform scheduled maintenance and to preserve the life of their enclosure.
CONNECTIONS
Regulators can regulate a single or a three phase circuit using any combination of one, two, or three regulators. Two regulators can be connected open-delta to regulate a three phase, three wire wye system. To help explain the different connections, below is a series of diagrams to help illustrate the typical connections of regulators.
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Single phase, two wire circuits require one regulator only with a single bypass switch for complete operation. A fuse and disconnect switch may be added but is not typical for single phase systems. Single phase connections are typical when using single phase conventional transformers. These are commonly seen on distribution lines where space is minimal. See figure 2. |
Figure 2
Single-phase, two wire circuit. |
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Regulating a three phase, three-wire system is no problem by using two regulators connected in an open delta. Single pole disconnects must also be used to totally isolate the regulator for maintenance. A three pole group operated switch and primary fuses are normally provided for the protection and isolation of the transformer. Eliminating the third regulator and bypass switch not only saves money but also space in a limited environment. See figure 3. Regulating a three phase, three-wire system is no problem by using two regulators connected
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Figure 3
Three-phase, three wire wye or delta circuit. |
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Three phase, three wire circuits require three regulators and three bypass switches. This approach uses single pole disconnect switches to isolate a regulator from the system for removal or maintenance. A three phase group operated switch and primary fuses are also added for transformer protection/isolation as shown in figure 4. This arraignment can be connected for systems up through 35 KV. The US State Department has standardized on this connection for all newly constructed embassies. |
Figure 4
Three-phase, three wire delta. |
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Three phase, four wire circuits require three regulators and three bypass switches. There is no need for single pole disconnects on the SL bushing of the regulator for this bushing is grounded. Typically this is the easiest of the different connections to maintain and service this connection is also the most cost efficient of the three phase systems. Using a common neutral/ground eliminates the need for series connections of the SL bushing as shown in figure 5. |
Figure 5
Three-phase, four wire wye. |
Each circuit represented above shows a single pole bypass switch, pole mounted single phase regulators, single pole disconnects Each circuit represented above shows a single pole bypass switch, pole mounted single phase regulators, single pole disconnects for regulator isolation and primary switching and fusing. A variety of combinations are possible and only the typical ones are shown above.
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Figure 6 |
System metering can also be provided in a regulator enclosure by the addition of another bay. As seen in figure 6 to the right, three potential transformers and three current transformers have been added to monitor the users system. These PT’s and CT’s are situated for easy access and maintenance. The PT’s and CT’s are then wired to a terminal block positioned in a convenient location for the user to connect to. Meter sockets and meters may also be provided if given the specific type and model of both.
The pro’s of using regulators enclosures are vast. Not only do you protect the regulator from hostile acts of vandalism, terror and war time acts but also from the weather and wildlife which will prolong the life of the regulator. Gilbert Electrical enclosures have been approved for a seismic 4 event due to the rugged environment which it may be situated.
By using single phase regulators in lieu of a three phase padmounted type regulator, you eliminate the worry of losing a phase and having to replace the entire regulator. Also, by purchasing the complete lineup you have a turn key unit. If purchasing all item separate, you must find real estate to mount the regulators, bypass switches, single pole disconnects, primary fusing and group operated disconnect. Not only do you have to position each item for ease of access and maintenance you must wire/connect these items together. In a three phase, delta configuration this can be quite troublesome and time consuming. All of this is eliminated with a regulator enclosure. Some of the projects completed by Gilbert electrical include US Embassy Nairobi, US Embassy Dar Es Salaam, US Embassy Zagreb, US Embassy Angola and US Embassy Abuja, in Nigeria. Gilbert has projects here in the US as well which include many hospitals for power regulation.
Figure 7 shows a typical regulator enclosure lineup consisting of a five bay enclosure. A primary disconnect switch is located in the left most bay #1. Next, the bypass and regulator isolation switches are located in bay 2. Bays 3, 4 and 5 house the three regulators in a three phase system. All panels are removable and are secured with tamper resistant hardware. Customer connections for the incoming power feed and outgoing transformer feed are located in bay 1 and the rear of bay 2 respectively.
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Figure 7 |