Tricity Sunray Tungsten Radiator

The first electric heaters were based around high power single-ended carbon filament lamps, commonly known as the Dowsing Radiator. Such lamps faced competition after the 1905 invention of chromel / nichrome, a nickel-chromium alloy which resists oxidation up to dull red heat without requiring an evacuated glass bulb. The wire was typically coiled around a ceramic former which held the coils in place, and was itself heated and served as an auxiliary heat radiator. The resulting elements were much smaller than the old carbon lamps, and a new generation of portable electric fires was introduced with a horizontal bar heater at the focus of a polished metal reflector.

This lamp appears to have been an attempt to revive the heat lamps business, with a more modern alternative featuring a coiled tungsten filament. It actually employs four filaments connected in series to reach a total power of 200W, slightly less than the 250W of the original carbon lamps. The filaments are supported on a central glass rod which is itself supported by a coiled spring at the far end of the bulb. The bulb end is conically shaped, this facilitating its support when used horizontally.

'Tricity' was the brand of the British Electricity Transformer Co. Ltd, an early pioneer in transformers as well as domestic cooking and heating apparatus. Sunray was its brand for a range of domestic luminaires intended to produce both light and warmth, such as the famous 1978 copper louvred table lamp. Tricity owned a small lamp factory, Kye Lamps, of Edmonton in London. In 1930 it was absorbed by Crompton and the lampmaking was relocated to Crompton's own factories, where it is suspected that this lamp was produced.
Manufacturer: Crompton Parkinson Ltd.
Lamp Power: 200 Watts
Lamp Voltage: 230 Volts
Lamp Current: 0.8 Amperes
Cap Type: B22d/35x38 Brass & Vitrite
Bulb Type: T-57 T-18 in eighths/inch
Bulb Finish: Clear Soda-lime glass
Filament Type: 4C-8 4x axial coil
Atmosphere: Vacuum Red P getter
Luminous Flux: 1075 lumens
Luminous Efficacy: 5.38 lm/W
Colour Temperature: 2250K
Colour Rendering: Ra 100
Chromaticity Co-ordinates: CCx: 0.498 CCy: 0.412
Lifetime: Approx. 1000 hours
Burning Position: Universal
Overall Length: 285 mm 111/2 inches
Light Centre Length: 185 mm 71/4 inches
Factory: Leeds England
Date of Manufacture: Approx. 1930
Original Value:
References: 1) Photoelectric Measurement
2) Rays of Light, R.G. Tye, publ. Glowlamp Publications (UK) 2019, ISBN 978-0-9927054-0-4, p.375.
3) Tricity Sunray Table Lamp, Drew Pritchard Ltd.
4) Tricity Sunray Table Lamp, Science Museum Collection, UK.
5) Tricity Sunray Radiator, Museum of Technology, UK.
6) Tricity Sunray Radiator, Museum of Bristol, UK.
7) Patent GB 308,625, Improvements in Apparatus for Diffusion of Light and Heat, A.F. Berry, filed 22nd Sep. 1927.