Document 6RDqgmoqeO9en9qgLmyQMOJd

Hoffman Voices Specialties, Heating Hoffman 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-adjustabie 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 alnjost 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 the alternate blowing over and resealing of the loop, a constant differential pressure will be maintained between the steam main and return main and also that by the main tenance 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 Loops 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. Loop No. DIMENSIONS AND CAPACITIES OF HOFFMAN DIFFERENTIAL LOOPS Capacity A B C D E F G j K L Sq.Ft. Rad. w xh"1 % I'/.' 1%' I/.* 26' 30H' m' 3' 2000 w2 %' w 1'/.' y,* 18'/.' 26' 30M" 7X' 3' 3500 3 %' Wi' \'h' V 1' 23' 32' 37%' io' 3%' 7500 4 %' 2' 1* 2" 1' 25' 32' 37%' 10* 8%' 15000 Write for Descriptive Circular--Hoffman Controlled Heat 514 Hoffman Valves ' Specialties, Heating TYPICAL INSTALLATIONS HOFFMAN "CONTROLLED HEAT" EQUIPMENT OR* RETURN MAIN GRADING OOWN FROM BOILER ALLOWANCE FOR* GRADE OF MAIN VLOOP CAMCirv S4Pi.no ATDKWJT LLSJ Than PIPING CONWtCHON eooo 24' iy4* N* 3500 24 l'/4 N3 7500 30 l'/t H?4 15000 30 2 $L0W OFF YALVC* Write for Descriptive Circular--Hoffman Controlled Heat 515