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.
However, the discovery of this duct brought to light an earlier method of heating the Tropical Ravine House. The duct had originally been used as a horizontal path for the flue gases to escape from an open hearth fire which was kept constantly fired in a basement room. The flue gases supposedly warmed the walls of the brickwork duct and the soil piled around the duct. This provided a continuous constant heat flow into the Ravine House. The duct originally had been used as a horizontal path for the flue gases to escape from an open hearth fire which was constantly kept fired in a basement room.
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.
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.|
slight errors in the measurements of the gratings, the
floor levels of
the pathways were laid to create a slight camber in
outwards or inwards to compensate and correct
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 ridgeline 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