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Part number 550-100-211/0122
– 40 –
All piping methods shown in this manual use
primary/secondary connection to the boiler loop.
These designs ensure proper flow through the
boiler, for the most ecient and reliable operation
of the boiler and the heating system. For other
piping methods, consult your local Weil-McLain
representative or see separate boiler piping guides.
e boiler circulator (Taco 0014 for Evergreen
®
220, 299 and
300; Taco 0013 for Evergreen
®
399) is shipped loose. Locate it
in the boiler outlet, as shown in the appropriate piping diagram
in this manual.
DONOT use the boiler circulator in any location
other than the ones shown in this manual. e
boiler circulator is selected to ensure adequate ow
through the boiler.
Failure to comply could result in unreliable perfor-
mance and nuisance shut downs from insucient ow.
Install a system circulator or zone circulators as shown in the
piping diagrams in this manual. ese circulators must be sup-
plied by the installer.
Systemorzonecirculatorowrate
1. Size circulators based on the ow rate required to achieve the
temperature change needed.
2. You can closely estimate temperature rise (or drop) through a
circuit by using the following formula, where TD is tempera-
ture rise (or drop), FLOW is ow rate (in gpm), and BTUH
is the heat load for the circuit:
FLOW =
BTUH
—–—–—–—–
TDx500
Example:
Consider a system loop for a system with total heating load equal
to 210,000 Btuh. e desired temperature drop through the sys-
tem piping is 20°F. en the required ow rate is:
FLOW =
210,000
—–—–—–—–
20x500
= 21gpm
SIMPLIFIED:
For20°temperaturedrop,FLOW=MBH/10.
Systemorzonecirculatorheadrequirement
1. e circulator must be capable of delivering the required ow
against the head loss that will occur in the piping.
2. Determine the pipe size needed and the resultant head loss
using accepted engineering methods.
3. e simplied pipe sizing here is limited to residential sys-
tems, and does not include systems with fan coil units or
radiant tubing.
The following simplified method for pipe and
circulator sizing must be limited to residential ap-
plications using baseboard (nned or cast iron),
cast iron radiators or convectors. DO NOT apply
for radiant heating, fan coil units or commercial
installations.
1. Install the boiler and piping using the recommended piping
layouts shown in this manual.
2. Size the piping and components for each circuit in the space
heating system using Figure49,page41.
Attheowrates
listed, the head loss in all piping will be 0.04 feet per
footofpipe.
a. Det
ermine the heating load (Btuh) for each circuit.
b. Calculate the ow rate for each circuit using its load.
c. To use a 20°F temperature drop, just divide the
MBH (1,000’s of Btuh) by 10.
d. Example — Flow for 20°F temp drop with 35,000 Btuh:
FLOW = 35MBH / 10 = 3.5 gpm
e. Find the pipe size in Figure49,page41 that has a max
ow rate just larger than that required for the circuit.
f. Find the total equivalent length (TEL) of the circuit.
g. TEL accounts for losses through ttings and valves by
using the equivalent length of pipe that would cause the
same head loss. Add these numbers to the measured
length of the circuit to nd TEL in feet.
h.
TELisusuallycloseto1.5timesthelengthofthe
circuitforresidentialbaseboard,radiatororcon-
vectorapplications.
i. Measure the length of each circuit from the circulator
outlet back to its inlet. en multiply this length times
1.5 to get the approximate TEL of the circuit.
j. Find the head loss for
each circuit:
TEL=1.5XCircuitLength
(feet)
HEAD=TELX0.04
(feet water column)
k. NOTE: Size system header piping for the total ow of all
connected zones.
3. Example:
a. For a circuit with heating load = 45,000 Btuh (= 45 MBH).
Measured length of circuit is 88 feet.
b. Flow = 45 MBH / 10 = 4.5 gpm.
c. TEL = 1.5 x 88 feet = 132 feet.
d. From Figure49,page41, select 1" pipe (max ow = 7.1
gpm).
e. Head loss = TEL x 0.04 = 132 x 0.04 = 5.28 feet.
f. Select a circulator that can deliver at least 4.5gpm at a
head of 5.28feet. (Read the NOTICE below.)
To use this method, limit the ow through ¾"
nned-tube baseboard to 3.9 gpm, or use 1" base-
board and limit ow to 7.1 gpm. If the total load of
the circuit requires more ow, split the circuit into
two or more.
(continued)
220 /29 9/3 00 /39 9
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