tom, under the impression that otherwise the outside portions of the loops would easily become air bound. Some of the author's experiences, however, lead him to think that as far as this is concerned the circulation in this type also is better without the top connection. There is, however, one practical advantage which the top-connection radiators have over the steam type, that is more especially marked in long, low radiators. If, with a one-pipe connection, the supply end is somewhat raised, on account of bad steam fitting, the unwarranted expansion of a riser, or other cause, it may trap the end loops of the steam type so as to shut off the air valve entirely, whereas the top-connection type would have a circulation in any such case, as is illustrated in Figure 29. Such a condition, though the result either of poor design or bad workmanship, is still a frequent occurrence in practice.
Figure 30.—Gold's Pin Radiator.
Circulation in indirect radiators.—Indirect radiators, which are always made to lie horizontal, are usually made with loops equivalent to the two-column form, but of greatly exaggerated width and very low, and have the steam connection at one of the lower corners. There are, however, some special forms, and one has to use his judgment as to their qualities in respect to circulation.
It is important that radiators be built and set so that but little, if any, water will stand in them. The openings for pipe connections should be at the lowest point and the radiator should drain perfectly. The loops of some radiators are built so that there is quite a pocket under the opening. This should be avoided, as the
