When an entry into this duct
was opened up it was found to start at a
height as high as a walkway but then
gradually decreased in height until it
became a crawlway before it finally ended as
two adjacent earthenware hollow pot
air passageways. At this point the cast iron
pipework left the duct and was then buried
in the ground. Through the passage of time
the wet soil had corroded the surface of the
cast iron and ultimately the pipe wall
eventually failed and this created the
leaks.
|
The
gradual reduction in size and area of the
flueway kept the flue gases moving at a slow
enough velocity, so that they could distribute
and transfer their heat into the surrounding
brickwork structure. At the end of the duct
the flue gases finally passed into the two
earthenware pot shafts before connecting
into a vertical brick chimney at the other
side of the building from the fire room.
It must have soon been found
that this method of heating was proving
unsuccessful as the long horizontal duct run
for the flue gases could not provide
sufficient draught in the system to draw the
gases into the chimney. We can only imagine what the room conditions were like for the unlucky stoker trying to maintain the fire well alight. That
this original system did not prove
successful is evident by its
replacement with the more reliable
method of
using 4" cast iron hot water coils as the
heating system.
|
The Palm House. Belfast
When Musgrave came to fix the floor gratings which were to follow the elliptical route of the pathway, it was found that they had been cast slightly too large. Due supposedly to wrong measurements being taken. The sections were out of alignment and would not fit together following the route of the pathway. Consideration was then given to scrapping all the cast iron sections, but an alternative and unusual solution was adopted to correct the misalignment. |
To overcome
these slight errors in the measurements of the
gratings, the floor levels of the pathways were laid
to create a slight camber in either direction,
outwards or inwards to compensate and correct
for these dimensional errors. Also where found necessary slight offsets had to be formed in the alignment of the ducts under the pathway. |
The back wall of the Palm House was constructed as a double skin cavity brick wall plastered on either side. This allowed the wall to be used as a 'hot wall', and up through the cavity passed the flue gases from a fire in a brickwork furnace sited in a basement room. The outer skin of the wall tapers inwards towards the top of the Palm House which narrowed the pathway for the flue gases and slowed them down to maximise the heat transfer into the brickwork walls. At the top of the wall along the roof ridge line a few decorative flue terminals were fitted to allow the flue gases to escape to atmosphere. Stokers were employed who worked in shifts day and night to keep the fires permanently alight. They lived on the premises in the rooms at the rear of The Palm House. This early method of heating the
glass houses was not successful so in 1862 a wet
heating system was installed by Musgrave and
C0mpany for £95 using banks of 4" cast iron
piping fitted under the plant stagings, fed from
a Cockey's patent boiler. New boilers were
installed in 1871 and they were supplemented in
1881 by large terminal end saddle boilers.
The installation work was carried out by
Wimmington and Co. who also removed the pipes of
the smoke flues. Later changes were made 1892
to the heating when the Saddle
boiler was taken out and the firm of John Hall,
Queen Street installed two Hartley and Sugden
boilers.
|
CIBSE HERITAGE GROUP
DECEMBER 2001