CleaverBrooks 4WI - 3.2.1.5 - Water Circulation; 3.2.1.6 - Multiple Boiler Installations

Waterside Care and Requirements
3-4
750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
3.2.1.5 — Water Circulation
The Maximum Circulating Rate Chart, Figure 3-2, shows the maximum gpm circulation rate of boiler water in rela-
tion to full boiler output and system temperature drop.
FIGURE 3-2. Maximum Circulating Rate Chart
3.2.1.6 — 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.