Document brE12RnvwVBVk2YR7gev07w6

Hoffman Specialty Co., Inc. Specialties, Heating HOFFMAN "CONTROLLED HEAT" EQUIPMENT--(Continued) DIFFERENTIAL LOOP The Differential Loop is the safety device for maintaining a steady water line in vapor and vapor vacuum systems. It is entirely automatic, non-adjustable and has no moving parts to stick at a critical moment. Through its use water is permitted to rise in the return main a certain predetermined amount when the loop functions, blowing over a small quantity of steam which closes the No. 10 or 11 Valve installed on the loop for venting the system and then compresses the air which is "bottled up*' in the return main and builds up a pressure which prevents further rise of water in the vertical part of the return beyond the predetermined amount. As soon as this is accomplished, and the action is almost in stantaneous, the loop reseals and no more steam is blown over until the differential pressure is not maintained. It will be readily seen that; by Hoffman Differ- the alternate blowing over and resealing of the loop, a constant enttal Loop differential pressure will be maintained between the steam main and Hoffman Differential Loop. return main and also that by the maintenance of this differential regardless of how high the boiler pressure goes circulation will take place in a radiator which is turned on with the return main vent closed through loop action. \ Differential Lpops are made in four sizes, having a capacity up to 15,000 sq. ft. of radiation. For larger systems the No. 4 Loops can be installed in a battery or the return mains divided so as to have their load come within the capacity of stand ard loops. No. 1 and No. 2 Loops should not be used where the low point in the dry return is less than 24 in. above boiler water line; with the No. 3 and No. 4 Loops this distance must be at least 30 in. DIMENSIONS AND CAPACITIES AND LIST PRICES OF LOOPS Loop No. 1 2 3 4 AB C DE F G j X L Ca pacity Sq. Ft. List Price Rad. w w wV4 Va y. \'/a V/i 2 1'// V/a l'/2 2 Wi 2 2 w 18%' 26* 30%' 7%' y. Va 18% 26 30% 7% 3 2000 $50.00 3500 * 75.00 1 25 32 37% 10 33/4 7500 100.00 1 25 32 37% 10 8% 15000 225.00 310 Hoffman Specialty Co., Inc. Specialties, Heating HOFFMAN "CONTROLLED HEAT" EQUIPMENT--(Continued) 311