39
87%-Efficiency Boilers –
Special Instructions
Water Piping
An 87%-efficiency boiler requires a minimum inlet
water temperature of 120ºF (49ºC) to prevent exces-
sive condensation in the combustion chamber. An
87%-efficiency boiler operated with an inlet tempera-
ture of less than 120ºF (49ºC) must have a manual
bypass or an approved low-temperature operation
system to prevent problems with condensation. A man-
ual bypass, shown in Fig. 15, must be piped into the
system at the time of installation. This piping is like a
primary/secondary boiler installation with a bypass in
the secondary boiler piping. Raypak strongly recomm-
NOTE: The constructions of the 84%- (standard)
and 87%-efficiency (optional) boilers are very similar,
and they are installed to the same requirements,
except as noted in this section.
ends that a thermometer be placed into the boiler inlet
piping next to the in/out header to facilitate tempera-
ture adjustment. Inlet water temperatures below 120ºF
(49ºC) can excessively cool the products of combus-
tion, resulting in condensation on the heat exchanger.
Venting
Appliance Categories
See Table Q for appliance category requirements for
the 87%-efficiency Hi Delta.
CAUTION: Proper installation of flue venting is criti-
cal for the safe and efficient operation of the boiler.
NOTE: For additional information on appliance cat-
egorization, see appropriate code NFGC (U.S.) and
B149.1 (Canada), or applicable local building codes.
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