I bought this to see how waterproof it really was. I wanted to check out the quality of construction and how the individual lamp holders were connected to the main cable.
It turns out that it's quite a complex construction.
Traditional outdoor festoon is based on a flat rubber cable with lamp holders attached directly onto it with an IDC (Insulation Displacement Connector) that pierces the two conductors in the flat cable with spikes for an electrical connection, and then clamps on with enough force to prevent water ingress. That approach has the advantage of being very compact and allowing lamp holders to be quickly placed anywhere on the cable. It's still used on some Christmas lighting frames, where a single cable can be attached to the frame with the holders in the appropriate positions.
The downside when using it as a traditional suspended festoon is that the holders can end up pointing upwards if it's thrown up in a hurry. Waterlogged lamp holders can lead to internal carbon tracking and flashover, knocking out the whole circuit and often involving lots of time to find the faulty lamp holder.
This approach has the holders at factory fixed positions with the advantage that even with a twisted cable the holders will generally dangle downwards. The fixed spacing of the holders limits the use of the festoon to simple decorative or general illumination. All festoon should be regularly supported along catenary wires, on hooks along a wall or under a roof edge to avoid stressing the cable.
Ideally the lamps chosen for use should seal gently onto the surrounding flexible plastic rim of the holder. Low power LED is preferred and there should be no seams or vents on the lamp external to the holder where water can seep in. This makes the glass LED filament lamps perfect, not just for their functionality but their appearance.
The current rating of the cable is the limiting factor in how many lamps can be used, and with LED lamps you have to consider the power factor. For the typical power factor of a 2W LED filament lamp of around 0.5 you have to treat it as a 4W load. That means I would limit the maximum number of 15 lamp strings connected together on a 240V supply to about 10 or 12. With the common plastic golf-ball sized LED lamps rated 0.5 to 1W the power factor is so bad that they have to be counted as 10W lamps, reducing the number of 15 lamp strings to just 5. (Use the filament style LED lamps. They're better.) With a 120V supply the number of lamps that can be used is typically halved due to the higher current for the same power.
The UK plug on this set was fitted with a 13A fuse which should be changed for a 3A or 5A one. The Cable is marked HO5VV-F with 0.75mm csa conductors. If the cable is copper (which is not guaranteed these days) then the current handling capability will be in the region of 6A The PVC insulation is not rated for continuous outdoor use, but is OK for short term use. It is not as resilient as proper UV rated black rubber cable.
The availability of the LED filament lamps in other voltages makes it viable to use this festoon on a 12V DC supply. That could be for remote solar operation or it could be for safety if the lamps are at a height where they can be touched. With a 12V supply and 2W lamps each festoon would be better with its own power supply instead of extending them to avoid progressive loss of intensity due to voltage drop.
The DC approach would be perfect for filming applications due to the absence of flicker.
You can also get 3V lamps, but they're rare and while it would be fun to run festoon on a single lithium cell, it's not very practical.
Note that there are cheaper versions of this sold with less lamp holders and traditional high power tungsten lamps in the same shape and size. Be careful to check listing details and power rating if buying a string. It's cheap enough to buy a bulk pack of 12V, 120v, or 230V LED lamps online if you get the wrong set.
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14 окт 2024
