BY GEORGE LANTHIER
Five pieces of radiation installed in five rooms are now going to become five secondary loops .
• The first loop delivers 22000 Btus or 2.2 gpm that needs a ¾ ” pipe .
• The second loop delivers 19200 Btus or 1.92 gpm
Figure 13 that needs a ¾ ” pipe .
• The third loop delivers 28800 Btus or 2.88 gpm that needs a ¾ ” pipe .
• The fourth loop delivers 9600 Btus or 0.96 gpm that needs a ½ ” pipe .
• The fifth loop delivers 4800 Btus or 0.48 gpm that needs a ½ ” pipe .
If you add all of these up , you will have a total Btu load of 84,400 or 8.44 gpm . That means your primary loop will be a 1-inch pipe . We ’ ve doubled the baseboard requirements . The first loop has 40 feet of baseboard , the second has 36 feet of baseboard , and the third has 52 feet of baseboard . The fourth room has 16 feet of baseboard , and the last one has 8 feet of baseboard .
Now we need to size the circulators . The Primary Loop is only
15 feet long and is steel pipe right around the boiler . 15 ’ x . 06 = ( 0.9 ) 1 foot of head So , we need a Primary Loop circulator that will pump 8.44 gpm at 1 foot of head . Using Figure 12 , you could use that circulator
again and again set it to low-speed . Using Figure 13 , I would use the model ‘ E ’. Have you noticed that all of our circulators are very small ? That ’ s the whole idea .
Now to size the Secondary Loop circulators . But let ’ s look at the closely spaced tee theory again and what happens when water flows through a tee . If water goes into
Figure 14
Figure 15
a tee , it has to come out , but how the water goes in and out of a tee is really what matters . With a diverter tee fitting the diverter does the work and sends the water along the right path , Figure 14 , but there are no diverter tees in the basic Primary-Secondary system , although as you ’ re about to see they could be in the secondary loop ( s ). Water always takes the path of least resistance and so as the water enters the tee it ‘ sees ’ that it can travel right along without any resistance or take that branch cut-off , which is more work , so it keeps going straight through . The reason why it ’ s more work is because of the circulator in the way and the resistance put up by the other fittings in the branch circuit that make up the Secondary loop . The trick is to keep those tees closely spaced and no more than six pipe diameters apart . With ¾ ” pipe your goal is to keep the branches no more than 4-½ ” apart . If you put them too far apart , water may start to think that going through the Secondary loop is easier and that will ruin your day . Again , using a fitting like the one shown in Figure 15 eliminates the problem . We ’ ll pick this up again in Part Two . Thanks for reading this and see ya ! l FON
* George Lanthier is the owner of Firedragon Academy . His website and contact information can be found at www . FiredragonEnt . com .
38 SEPTEMBER 2023 | FUEL OIL NEWS | www . fueloilnews . com