87%-efficiency boilers – special instructions – Raypak 302B-902B User Manual
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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 S 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
categorization, see appropriate code NFGC (U.S.)
and B149 (Canada), or applicable local building
codes.
10°F T
20°F T
30°F T
Min. Flow
Max Flow
Model
No.
gpm
P (ft)
gpm
P (ft)
gpm
P (ft)
gpm
P (ft)
T gpm
P (ft)
T
302BE
52
3.3
26
<1.0
N/A
N/A
20
<1.0
26
90
9.8
6
402BE
69
6.0
35
1.5
23
<1.0
20
<1.0
35
90
10.0
8
502BE
87
9.7
44
2.5
29
1.1
22
<1.0
40
90
10.4
10
652BE
N/A
N/A
57
4.4
38
2.0
28
1.1
40
90
10.8
13
752BE
N/A
N/A
65
6.1
44
2.8
33
1.6
40
90
11.3
15
902BE
N/A
N/A
78
8.9
52
4.1
39
2.3
40
90
11.7
17
Combustion
Air Supply
Exhaust
Configuration
Heater Venting
Category
Certified
Materials
Combustion Air
Inlet Material
Vertical Natural Draft
Venting
II
Stainless Steel
(Gas Tight)
From Inside Building
(Non-Direct Venting)
Horizontal Through-
the-Wall Venting
IV
AL29-4C
Vertical Natural Draft
Venting
II
Stainless Steel
(Gas Tight)
Galvanized Steel
PVC
From Outside Building
(Direct Venting)
Horizontal Through-
the-Wall Venting
IV
AL29-4C
ABS
CPVC
Table R: Heater Rate of Flow and Pressure Drop
Table S: Category Determination for Venting Purpose and Venting Arrangement
Note: Basis for minimum flow is 20 gpm or 40°F ∆T. Basis for maximum flow is 90 gpm.