CleaverBrooks CBEX Elite Operation And Maintenance page 27

3.2 — Water Requirements
NOTE: The circulating pumps should be interlocked with the burner so that the burner cannot operate unless the cir-
culating pump is running in order to avoid damage to the equipment.
Water Circulation
The Maximum Circulating Rate Chart, Figure 3-2, shows the maximum gpm circulation rate of boiler water in
relation to full boiler output and system temperature drop.
Boiler Output
BHP MBTU/hr
100 3,350
125 4,185
150 5,025
200 6,695
250 8,370
300 10,045
350 11,720
400 13,400
500 16,740
600
20,080
700 23,430
800 26,780
Maximum Circulating Rate Chart
FIGURE 3-2.
Multiple Boiler Installations
When multiple boilers are used, care must be taken to ensure adequate or proportional flow through the boilers.
Proportional flow can best be accomplished by use of balancing valves and gauges in the supply line from each
boiler. If balancing valves or orifice plates are used, a significant pressure drop (e.g., 3-5 psi) must be taken
across the balancing device to accomplish the purpose.
If care is not taken to ensure adequate or proportional flow through the boilers, wide variations in firing rates
between the boilers can result.
In extreme cases, one boiler may be in the high-fire position while the other boiler or boilers may be at low fire.
The net result would be that the common header water temperature to the system would not be up to the desired
point.
Pump Location
It is recommended that the system circulating pumps take suction from the outlet connection on the boiler, and
that they discharge to the system load. The suction side is preferred because it decreases air entry into the sys-
tem and does not impose the system head on the boiler.
750-368
CBEX Elite 100-1200 HP
System Temperature Drop - Degrees F
10 20 30
Maximum Circulating Rate - GPM
670 335 223
836 418 279
1,005 503 335
1,340 670 447
1.675 838 558
2,010 1,005 670
2,350 1,175 784
2,680 1,340 895
3,350 1,675 1,120
4,020 2,010 1,340 1,005
4,690 2,345 1.565 1,175
5,360 2,680 1,785 1,340 1,075
40 50 60
168 134 112
209 168 140 120
251 201 168 144
335 268 224 192
419 335 280 240
503 402 335 287
587 470 392 336
670 535 447 383
838 670 558 479
805 670 575
940 785 670
895 765
70 80 90 100
96 84 75 67
105 93 84
126 112 100
168 149 134
210 186 167
251 223 201
294 261 235
335 298 268
419 372 335
502 448 402
585 520 470
670 595 535
3-3