On Thu, 29 May 2008 21:35:34 +0100 someone who may be "Fredrick
Skoog" wrote this:-

The guy who quoted for the
tubes said that they were more efficient,

True, though one has to compare like with like. If an old radiator
is being used as a flat panel then it is going to be rather less
efficient than a well designed, low water volume, flat panel.

Vacuum tubes will still have an advantage over flat panels,
especially in cloudy weather, but it is not as marked as some imply.

less susceptable to dirt (i.e.
bird **** was more likely to splat between them rather than all over them)

Random bird **** is a little more likely to hit the tubes than the
gap, the gap typically being a little narrower than the tubes.
However, the gap should be filled by reflectors so both types of
panel should be a large unbroken area. A flat panel of equivalent
output will be larger, so there is a larger target.

and any damage was more likely to mean the replacement of a tube or two
rather than then whole panel (he obviously had a thing against birds as he
cited an example of a bird dropping a stone or some such)

Or someone throwing stones. However, it is true that an individual
tube can be replaced to deal with damage, as opposed to the whole
panel or the whole panel cover.

In a DIY context the advantage is with vacuum tubes. The header,
frame and tubes are all individual items which can be lifted onto a
roof individually. Lifting a flat panel, especially one made from an
old radiator, means lifting the whole thing, with size and weight to
deal with. Not insurmountable problems, but ones to bear in mind.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54