Boiler Installation Considerations; Hydronic System; Hot Water Supply Boiler System - General Water Line Connections - A.O. Smith HW 300 Instruction Manual

BOILER INSTALLATION CONSIDERATIONS

HYDRONIC SYSTEM

All modern hydronic type boilers are exceptionally fast heating
units. The low water volumes in relation to firing rates require
special attention to water flow rates for smooth, efficient
operation. These considerations for the A. O. Smith copper heat
exchanger boilers are covered below.
Conventional 20 ºF (10 ºC) drop in systems for a fully loaded
boiler will maintain the following approximate flow rates:
TABLE 6. WATER FLOW RATES
MODELS
HW-300
HW-399
HW-420
HW-520
HW-670
Figure 29 to Figure 42 on Pages 47 to 60 show typical installations
of the boiler with pipe sizing and circulating pump selected by the
installer to provide adequate water flow whenever the boiler is
firing.
In a system with several large zones of which any might be
smaller than approximately 1/3 of the system should include a
hydronic balancer as shown in the piping diagrams. The balancer
connects between the system supply and the return line before
the circulating pump inlet. Adjustment of the balancing cock
should permit adequate boiler flow rate when only the smallest
zone is in operation.
Attention should be given to balancing inputs and water flow
rates where wide variations of system flow rates can occur.
The recommended minimum flow rates that will result in
approximately 50 ºF (30 ºC) temperature rise across the boiler
are as follows:
TABLE 7. MINIMUM WATER FLOW RATES RESULTING IN
TEMPERATURE RISE
MODELS
HW-300
HW-399
HW-420
HW-520
HW-670
Pipe sizing and boiler loop pump selection data are shown in
Table 8 for several different temperature rises across the boilers.
GPM (LPM)
24 (91)
32 (121)
34 (127)
42 (158)
54 (203)
NOTE: Pipe loop sizes and pump selections based on 50
equivalent feet of pipe and fittings.
*All pump sizes listed are B & G model numbers.
HOT WATER SUPPLY BOILER SYSTEM - GENERAL
WATER LINE CONNECTIONS
Piping diagrams will serve to provide the installer with a
reference for the materials and methods of piping necessary for
installation. It is essential that all water piping be installed and
connected as shown on the diagrams. Check the diagrams to
GPM (LPM)
be used thoroughly before starting installation to avoid possible
10 (36)
errors and to minimize time and material cost. It is essential that
13 (49)
all water piping be installed and connected as shown on the
13 (49)
diagrams. Figure 29 to Figure 42 on Pages 47 to 60.
17 (63)
21 (81)
These boilers can be used ONLY in a forced circulation hot water
heating system. Since most forced circulation systems will be of
the closed type, install the water supply line as shown on piping
diagrams, Fast filling of large pipe, old radiator installations and
pressure purging of series loop systems (where high pressures
are not available) requires bypassing of the pressure reducing
valve. Generally, pressure purging is not possible with a well
pump system. High point air venting is essential.
If the system is of the open type, a pressure reducing valve
will not be required as the water supply to the system will be
controlled by a manually operated valve. An overhead surge tank
is required.
12
TABLE 8. PUMP AND PIPE SIZING DATA
(PIPING FROM TEES IN MAIN TO BOILER BRANCHES)
TEMP. RISE °F
MODEL
(°C)
20 (10)
30 (15)
HW-300
30 (15)
40 (20)
20 (10)
35 (15)
HW-399
40 (20)
40 (20)
20 (10)
35 (15)
HW-420
40 (20)
40 (20)
20 (10)
20 (10)
HW-520
35 (17)
40 (20)
20 (10)
30 (15)
HW-670
35 (17)
40 (20)
*PUMP PIPE
GPM
SIZE SIZE
24 1-1/2" PR 2"
16 150 1-1/2"
16 125 1-1/4"
12 100 1"
32 60-13 2"
18 1-1/2" HV 1-1/2"
16 150 1-1/2"
16 125 1-1/4"
34 60-13 2"
19 1-1/2" HV 1-1/2"
17 150 1-1/2"
17 125 1-1/4"
2-1/2" 2-1/2"
42
42 1-1/2" HV 2"
24 1-1/2" HV 1-1/2"
21 150 1-1/2"
54 60-13 3"
36 2-1/2" 2-1/2"
31 2" 2"
27 1-1/2" HV 1-1/2"