Test switch

01

Lay out the poles for each circuit

ABB's Flexitest descriptive bulletin DB 41-077 describes FT-1 (10 poles, rear connected), FT-1F (front connected), FT-1X (extended terminals) and FT-14 (14 poles) switches. Potential poles are single non-shorting knife blades for potential, trip or control circuits; current poles are configured in pairs (C-C) in the bulletin, with a current test jack, a shorting spring, a shorting blade and a non-shorting blade, and the shorting spring positions are visible from the front. [1]

The bulletin states that the make-before-break current short-circuit feature lets test personnel isolate equipment from current transformer circuits, that voltage can be measured at a test clip on top of each pole, and that handles are black for potential and current circuits and red for trip circuits, with other colours available. [1]

Editorial calculation: the bulletin says the FT-14 gives 40% more poles than the FT-1 for 18% more space; 14 poles against 10 is the 40%, so a panel needing 12 poles could use one FT-14 instead of two FT-1 switches. [1]

Give the supplier the circuit list (CT phases, VT phases, trip, close, control), pole sequence and type for each position, handle colours, front or rear connection, terminal type, panel cut-out or 19 in rack mounting, cover type and sealing, test plug type, standards and listings required, and quantities.

02

Check ratings, standards and accessories

ABB's FT Flexitest family document states the switches are rated for 600 V and 30 A, come in 10- or 14-pole versions in combinations of potential, current or current-shorting poles, and are UL recognised, with 1E-qualified versions. [2]

DB 41-077 states that Flexitest switches meet ANSI/IEEE C37.90 and are UL, CUL and CSA listed, with Class 1E switches meeting IEEE C37.98, C37.105, 323-1983 and 344-1987; it gives net weights of 0.79 kg for FT-1 and FT-1F, 1.25 kg for FT-1X and 1.5 kg for FT-14, and says covers accept meter seals, with clear covers that can be left on with handles open. [1]

Editorial note: DB 41-077 is dated November 2007 and has been superseded; ask the supplier for the current bulletin and listing certificates for the exact catalogue number.

A second maker's meter test switch carries the same electrical rating under metering standards. TESCO Metering lists its test switches for transformer-rated metering installations with 600 V insulation and 30 A capacity, meeting EEI, ANSI C12.9, NEMA and H-Q requirements and UL recognised, in 4 to 12 poles on a moulded base. Its standard build has tin-plated components, standard stud connectors, a clear polycarbonate cover and single-colour handles; options are no plating or tin or nickel plating, box connectors, bi-colour or half-colour handles, and clear or black polycarbonate covers, with captured hardware and a stated delivery of 2–4 weeks. TESCO asks buyers to define pole count, connector type, handle colours, any reverse-potential requirement, cover and plating. [3]

Editorial note: the ABB relay test switch cites ANSI/IEEE C37.90, while the TESCO meter test switch cites ANSI C12.9; state whether the switch serves a protective-relay panel or a revenue-metering installation so the supplier quotes against the right standard. [1] [3]

03

Find test switch manufacturers

No manufacturer record has been reviewed for this product yet. Send your specification and CNFX will match it against manufacturer records.

04

Check pole letters, terminals, tie bars and rack panels

GE Vernova's FT & RT brochure rates its standard FT switch at 600 volts and 30 A, meeting ANSI/IEEE C37.90 and UL and cUL recognised. An FT switch holds 1 to 10 knife-blade poles, lettered A to J, each a potential, current or current-shorting unit, with rear screw or stud terminals numbered 1 to 20, one pair per pole. [4]

Handles are black, with red supplied by changing P to T for potential and C to R for current poles, and 2 to 10 handles can be tied with an interlocking bar. The black cover fits only when all blades are closed; the clear cover fits with blades open or closed. Net weights are 1.4 lb for the switch and 1.2 lb for the test plug. The RT rack assembly mounts three FT switches on a 19 in panel with up to 30 terminals and a standard full-length clear cover. [4]

For the 10-pole In-Service Series test plug, only current poles with shorting springs short the CT circuits automatically when the blades are opened before the plug goes in. [4] Editorial note: GE Vernova's FT stops at 10 poles, while ABB's FT-14 offers 14 [1]; list poles by letter in the enquiry.

05

Trace the switch components

This is a functional reference built from the sources cited; it is not one maker's design.

06

Fill the specification fields with values for your panel

A test switch quotation needs values for your panel. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

07

Send the circuit list, ratings and accessories together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Circuits: [CT; VT; trip; close; control]
Poles: [sequence P / C-C; handle colours]
Ratings: [voltage; current; listings]
Mounting: [panel; 19 in rack; front or rear]
Accessories: [cover; seal; test plugs]
Supply: [drawings; quantity]

See manufacturer records Send an enquiry through CNFX