WATER VELOCITY CONTROL
IMPORTANT
To ensure proper velocity through the heat
exchanger, it is necessary to regulate the
temperature rise across the heat exchanger
from inlet to outlet. (This
must
be done on
initial installation and periodically rechecked).
With the correct temperature rise across the
heat exchanger (See TABLE J), you may be
assured of the proper velocity in the tubes
and long life and economical operation from
the boiler.
WATER FLOW REQUIREMENTS
AND SYSTEM PIPING
Lochinvar boilers are generally capable of
operating within the design flow rates for the
building heating system. To ensure the most
efficient operation, a boiler needs adequate
water flow. Pump sizing, pipe sizing, and piping
layout
must
be taken into consideration for
proper system flow. (Table I) provides maximum
and minimum flow data for each model. (Table J)
provides Gallons Per Minute and boiler head-loss
at various temperature rises for each boiler based
on Btu/hr input. These two charts will provide
assistance in system flow design.
Primary/Secondary Piping
Using a primary/secondary piping arrangement
can solve many system flow complications.
This piping arrangement uses a dedicated pump
to supply flow to the boiler. The pump is sized
based on the required boiler flow rate, boiler
head-loss and head-loss in the secondary system
piping. A separate pump is used to provide the
desired flow for the system.
Primary/Secondary piping allows the system and
the boiler(s) to operate at their optimum flow rate.
The system works best when the boiler(s) are
supplied with pump control relays which are used
to cycle the secondary pump(s). When piped
correctly, the secondary pump helps to prevent
flow through the boiler(s) when they are not firing.
Use of primary/secondary system
will eliminate the need for a system or boiler
bypass. Figure 15 depicts one example of
primary/secondary piping.
L o c h i n v a r
D E S I G N E R
’
S
G U I D E
E F F I C I E N C Y
+
B O I L E R
6 1 5 - 8 8 9 - 8 9 0 0
15
GPM
25.2
33.7
42.1
50.5
FT. HD
0.9
1.4
1.7
2.6
GPM
16.8
22.4
28
33.6
FT. HD
0.5
0.6
1.2
1.6
GPM
12.6
16.8
21
25.2
FT. HD
0.4
0.5
0.7
1.1
GPM
10.1
13.4
16.8
20.2
FT. HD
0.3
0.4
0.6
0.7
GPM
8.4
11.2
14
16.8
FT. HD
0.2
0.3
0.5
0.6
GPM
6.3
8.4
10.5
12.6
FT. HD
0.2
0.3
0.4
0.5
INPUT
150,000
200,000
250,000
300,000
OUTPUT
126,000
168,000
210,000
252,000
TEMPERATURE RISE
10°F
∆∆
T
15°F
∆∆
T
20°F
∆∆
T
25°F
∆∆
T
30°F
∆∆
T
40°F
∆∆
T
(TABLE J) – WATER FLOW REQUIREMENTS
(TABLE I) – MINIMUM & MAXIMUM
BOILER FLOW RATES
MODEL
MINIMUM FLOW MAXIMUM FLOW
NUMBER
(GPM)
(GPM)
EB 150
6
60
EB 200
8
60
EB 250
10
60
EB 300
12
60
*Min. flow based on 40°F temperature rise.
