EC111A Rapid Nigrescence Lighthouse Lamp

The EC111A is the most recent incandescent lamp created for lighthouses operated by the Trinity House Corporation of Great Britain. It is unusual in its electrical rating, optical configuration of the filaments, and its mode of operation.

Earlier British lamps had low voltages of 50-100V, because they were operated from batteries or diesel generators in remote places beyond the reach of the electricity grid. The higher power lamps had one or two filaments, and their light output was coded with massive rotating optical systems. By the 1960s mains supplies began to reach the larger lighthouses and a 240V lamp became feasible - and efforts were made to enable pulse the light signal electrically.

The first lamp for this purpose was the 240V 3000W EC111 developed by Osram-GEC, which employed six small 500W filaments in a triple cylindrical configuration so as to reduce the nigrescence time of the cooling filaments, and achieve better defined light pulses. That was produced until 1975/76 when it was replaced by this superior EC111A of Thorn Lighting. It employs a considerably simpler arrangement of four 750W filaments arranged in a box configuration

The lamp is hand-made throughout, its stem having a lateral Jaeger exhaust tube. The filaments are mounted on heavy nickel rods clamped to the stem with nuts and bolts. The bulb is mouth-blown in Monax glass by Moncrieff glassworks of Scotland, and the cap hand-turned from solid copper by Lamp Caps of Chesterfield. A last run of EC111A lamps was produced by Thorn at Buckie shortly before its closure, and they became obsolete around 1996 following the conversion of the last lighthouses to 1000W MBI metal halide lamps.
Manufacturer: Thorn E.M.I. Type EC111A
Lamp Power: 3000 Watts
Lamp Voltage: 240 Volts
Lamp Current: 12.5 Amperes
Cap Type: P89s/82x75 Solid Copper & Porcelain
Bulb Type: GS-200 GS-63 in eighths/inch
Bulb Finish: Clear Monax borosilicate glass
Filament Type: 4C-13X Box
Filament Size: 27mm x 62mm
Atmosphere: Argon-Nitrogen Red phosphorus getter
Luminous Flux: 52,500 Lumens
Luminous Efficacy: 17.5 Lumens per Watt
Colour Temperature & CRI: CCT: 2900 Kelvin CRI: Ra 100
Chromaticity Co-ordinates: CCx: 0.444 CCy: 0.406
Rated Lifetime: 800 hours
Burning Position: Vertical cap down ± 30°
Overall Length: 405±10 mm 16 inches
Light Centre Length: 235±3 mm 91/4 inches
Factory: Buckie Scotland
Date of Manufacture: Approx. 1986 Serial No: 12-12
Original Value: GB£59.33 (1977)
References: 1) Thorn EMI Lamp Catalogue, 1984/85
2) Trinity House Engineering Chief's Specification of Electric Lamps for Stores Supplies, 1962/63.
3) Lighting Industry Federation Schedule of Projection Lamp Types, London, 1982.
4) Twenty Years in Lighthouses 1924-1944, F.W. Cooper, Lighthouse Department, Chance Brothers Limited, 1979, pp.19-20.
5) Private Communication, Ian Tutt, Trinity House Lighthouse Corporation Ltd, Cowes, Isle of Wight, August 1995.
6) Private Communication, Bill Bellion, Watermarks Ltd., Hayling Island, September 1995.
7) Private Communication, Harry Pattison, Master Glassblower, GE Lighting Leicester, 1996.