nickbarnes (nickbarnes) wrote,

The Mystery Box

A very geeky post; skip if you aren't interested in old gadgets
Since I moved into my rented house in Staines 4 years ago, I've often wondered about the Mystery Box. The Mystery Box is about 30cm x 45cm x 10cm, and is mounted on one wall of the living room of my rented house in Staines. It's painted white, and has a switch and a control knob on the front, but has no visible identifying marks or branding. The Box is silent, cold, and appears inactive. Neither the switch nor the control knob seem to have any effect. At the prompting of my friend Alex Atkins, I finally took the cover off and found ...
mystery_box(photo by Alex Atkins)
It's a long-disused ventilator unit. Behind it there are two holes through the external wall - one about 10cm in diameter, one a little less (given the vintage, they are probably 4-inch and 3-inch respectively) - which have been filled in with concrete on the outside of the wall. You can see the end of the upper hole in the picture; the lower hole is behind that central metal plate. The box contains two airways: the upper one is presumably for outgoing air and the lower one for incoming air. All the airways and the front and back of the box are lined with some ancient insulation, half an inch thick. Behind the metal plate in the centre is a fan, to draw air in through the lower hole. Then that lower airway goes all the way around the fan unit, and exits into the room through a concealed grille in the bottom of the Box. The upper airway comes in through another concealed grille on the left of the Box and just zigzags across before exiting through the upper hole. I imagine these airways are designed like this to promote heat exchange somehow, but I am not sure as they are not arranged so that heat in incoming air can be transferred to outgoing air. There doesn't appear to be any heating element, although some wires do disappear into the covered metal channel below the fan and I couldn't readily get access to that without breaking things. None of the electrics is connected to the mains or any other supply.
The oddest thing was that the fan was totally clogged with old newspaper, and there was some screwed-up newspaper in the lower hole, and a heap of newspaper fragments at the bottom. My guess is that the newspaper was jammed in the hole before it was sealed up, but before the Box was disconnected from the mains. At some subsequent point somebody turned it on (maybe to find out what it did) and it ran for a short while with the fan chewing up the paper. Unfortunately for the cause of domestic archaeology, I didn't have the time to pick the paper apart and find a date, but it looked to me like a 70s tabloid, at least typographically.
So now I know. The Box went back on the wall, and the cover went back on the Box. If I owned the house, it would have been removed long ago. I might ask the landlord if it can be removed and the holes made good, because (although they are filled in at the outside end) they doubtless contribute to the drafts in the room.

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