Designer Guide

19
LOCHINVAR, LLC
300 MADDOX SIMPSON PKWY
LEBANON, TN 37090
www.lochinvar.com
Designer’s Guide / Knight XL Boiler
BOILER TEMPERATURE RISE CHART
Model
Minimum
20°FΔT
25°FΔT
30°FΔT
35°FΔT
Number
Pipe Size
GPM
Ft/hd
GPM
Ft/hd
GPM
Ft/hd
GPM
Ft/hd
KBN 400
1 1/2"
37
21
30
14
26
11
21
8
KBN 501
1 1/2"
46
23
37
16
32
13
26
10
KBN 601
2"
55
31
44
22
38
18
32
13
KBN 701
2"
65
30
52
20
45
16
37
11
KBN 801
2"
74
33
60
23
51
18
42
12
WATER FLOW
We have one item to check regarding water flow.
Is the minimum planned flow rate for the system loop below that of the planned
flow rate through the boiler?
In a Primary / Secondary Piping System, the lowest potential System Loop Flow
Rate MUST be 25% greater than the Boiler Loop Flow Rate.
LOW SYSTEM FLOW RATE
The use of System / Boiler Loop piping is used to separate the higher system flow rate from the
lower boiler flow rate. But what about low system water flow? Does the System / Boiler Loop
piping protect the boiler during low system flow? No, not if the system flow rate drops below the
flow rate chosen for the Boiler loop.
As seen in the two diagrams on the next page, the boiler flow rate will backfeed down the System
line and recirculate taking the path of least resistance. This means the boiler is recirculating
heated water and it is a very small volume of water.