This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Various forms of indirect radiators have been shown in Fig.. 8, 9, 14 and 15 of Part I. A hot-water radiator may be used for steam but a steam radiator cannot always be used for hot water as it must be especially designed to produce a continuous flow of water through it from top to bottom. Fig.. 1 and
2 show the outside and the interior construction of a common pattern of indirect radiator designed especially for steam. The arrows in Fig. 2 indicate the path of the steam through the radiator which is supplied at the right while the return connection is at the left. The air valve in this case should be connected in the end of the last section near the return.
A very efficient form of radiator and one that is especially adapted to the warming of large volumes of air as in schoolhouse work, is shown in Fig. 3, and is known as the "School pin" radiator. This can be used for either steam or hot water as there is a continuous passage downward from the supply connection at the top to the return at the bottom. These sections or slabs are made up in stacks after the manner shown in Fig. 4 which represents an end view of several sections connected together with special nipples.
A very efficient form of indirect heater may be made up of wrought iron pipe joined together with branch tees and return bends. A heater like that shown in Fig. 5 is known as a "box coil." Its efficiency is increased if the pipes are "staggered," that is, if the pipes in alternate rows are placed over the spaces between those in the row below.