Coughtrie SW.10

As with the sister fitting, the PW.15, this bulkhead was purchased new from Coughtrie, and so is unused. Examples of this classic 'Wellglass' fitting are very common, though their sale price has increased somewhat in recent years, owing to the fashion of using 'industrial'-type fittings as trendy indoor lights, particularly in locations where former factories and warehouses have been converted to domestic or commercial use. Naturally, this particular SW.10 is to be used in its intended outdoor environment!

The SW.10 comprises an aluminium gallery and bowl support ring (finished in textured black in this example, though white and grey finishes are also available) and (unusually for these days) glass bowl. Altogether, the bulkhead measures 222 mm (8.74 inches) in height, and 120 mm (4.72 inches) in width.

Nine fins are cast into the gallery. As well as providing strength, they will also act as a means of heat dissipation for the lamp (not that this will be required here!), as well as a tactile grip during installation. Just visible in the casting are "Coughtrie", "Glasgow" and the part number.

Three slotted screws spaced at 120 degree intervals secure the bowl retaining ring (and therefore, the bowl itself) to the gallery. The dome-like nature of the end of the bowl distorts the appearance of the bulkhead's interior.

With the screws undone, the retaining ring (part number C423) is removed, and can be separated from the bowl itself.

A thick rubber gasket (part number E863) ensures that the bulkhead's interior is sealed to a level of IP 65.

A porcelain bayonet lampholder takes up much of the space on the inside of the gallery. Although the lampholder had been pre-wired, this wiring was removed, as the fitting would be wired directly through a conduit system.

As with the PW.15, a wall bracket comprising a 20 mm tube and mounting plate were included with the fitting.

The SW.10 was installed outdoors on Monday, 12th December 2016. A Sylvania 'ToLEDo' 4 W LED lamp (designed to resemble a pearl-finish GLS filament lamp) was fitted.

The little LED lamp worked flawlessly, with its output (detailed as being equivalent to that of a 40 Watt GLS lamp) being perfect for lighting up the narrow passage around the side of the house.

Prior to installation, the lamp was tested with my energy monitoring device, which revealed the following results:

Test Voltage (V)	Current being drawn at full power (A)	Measured wattage (W)	Apparent Power (VA)	Frequency (Hz)	Power Factor	True Power (W)	Difference (W)	Percentage Difference
238.1	0.03	4	7	49.9	0.65	4.64	0.64	16.07%

An observation I made during this test was that the Power Factor fluctuated considerably, with it dropping to around 0.5 at times. The recorded 0.65 figure was the highest PF obtained during the test.

Coughtrie PW.15 | Whitecroft Centurion