Thorn Piazza


This is the 'classic' version of the Piazza bulkhead; its design was superseded in about 2007 with the more streamlined and imaginatively named "Piazza II".


This version of the Piazza first appeared in the mid-1980s; evidence of this is the style of the Thorn logo that is moulded into the front of the polycarbonate cover - the design was never updated to reflect the changing appearance of the logo over the years of production. The only modification to the logo in that time is the removal of the EMI suffix that was originally applied to Thorn products between 1984 and 1987; a convenient 'block' was created in order to mask this suffix.


The three individual refractor patterns from the front are repeated on either side of the visor.


A factory-fitted Royce Thompson P12R photocell was included with this bulkhead, in order to switch the fitting on and off automatically as appropriate. One of the two anti-tamper screws designed to secure the visor can also be seen here.


Loosening both of said screws using the small key to the right of the bulkhead in this view causes the visor to hinge forwards, in order to access the internal wiring. A small bag containing several 20 mm diameter plugs for the various cable entry holes positioned around the fitting was included, as was the Philips-made lamp.


The label informs us that the bulkhead was made in 2005, and that it is designed to run 70 W SON lamps with internal ignitors.


Removing the objects reveals the slightly angled reflector.


Removing the reflector itself allows access to the connections and control gear components. The photocell relay also fits into a moulding on the inside of the polycarbonate rear section. Although this particularly bulkhead is designed to run internal-ignitor lamps, the right-angled plate that the capacitor is attached to would also support an ignitor; indeed, earlier versions of this bulkhead came with a separate ignitor as standard (except on the 80 W MBF version, of course).


We now backtrack slightly in order to see the bulkhead fitted with a lamp. The use of a clear lamp presumably offers better optical performance than a coated lamp would.


With the visor back in place, the outline of the lamp can still be seen inside.


The Piazza was installed and connected up on Monday, 21st July 2014. The combination of the reflector and cover refractors made for a somewhat diffused distribution.


Lamp warm-up video:

Testing the lantern with my energy monitoring device 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
241.7 0.54 84 131 49.9 0.65 84.84 14.84 21.20%




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