13
12

CAUTION

• INSTALL BOILER SO THAT THE GAS IGNITION SYSTEM COMPONENTS ARE PROTECTED
FROM WATER (DRIPPING, SPRAYING, RAIN, ETC.) DURING APPLIANCE OPERATION AND SERVICE
(CIRCULATOR REPLACEMENT, ETC.).
• OPERATION OF THIS BOILER IN A SYSTEM HAVING SIGNIFICANT AMOUNTS OF DISSOLVED OXYGEN
CAN CAUSE SEVERE HEAT EXCHANGER CORROSION DAMAGE.
VIII System Piping

General Piping Notes

Figure 11 shows recommended near boiler piping for most common types of gravity return steam systems. Additional
information on steam system design may be found in Installation Guide for Residential Hydronic Heating Systems (Pub.
#200) published by the Hydronics Institute in Berkeley Heights NJ.
One of the primary purposes of this near boiler piping is to separate tiny water droplets from the steam exiting the boiler so
that “dry” steam is sent to the system. If the near boiler piping is not correct, wet steam will enter the system and the
following problems may occur:
•Short cycling on low water
•Boiler or system Flooding
•Hammering
•Failure to heat one or more radiators
Avoid the three common piping mistakes shown in Figure 12. This applies even if the existing boiler has one of the piping
mistakes shown in Figure 12 and appears to be working. If two or more steam mains must be connected to the boiler, connect a
separate take-off for each main into the header between the riser(s) and equalizer. Also note the following points:
1) A size reduction must be made to connect the header to the equalizer. This reduction must be made in the equalizer line. Do
not make this size reduction in the horizontal header.
2) One pipe steam systems require air vents on each radiator, as well as at the end of each main. For the system to work
properly, these vents must be properly installed, sized, and be in good condition. Inspect and replace any defective vents. If
there are no vents at the ends of the mains, install them.
3) Do not attempt to manifold multiple BSIs with gravity returns.
4) For installations with condensate or boiler feed pumps, follow the pump manufacturer’s piping instructions. Such systems
generally do not require Hartford loops.
5) Do not use a check valve in place of, or in addition to, a Hartford loop on a gravity return system.
6) Pipe the fill connection from a clean source of cold water. When the water supply is from a well, make sure that a strainer is
installed in the well system.
7) Piping with a Chiller - If the boiler is used in conjunction with a chiller, pipe the boiler in parallel with chiller. Use isolation
valves to prevent chilled water from entering the boiler.