Sizing Direct-Connected Dhw Piping - Weil-McLain Ultra 3 series User Manual

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gas fired water boiler

Sizing direct-connected DHW piping

Direct-connected DHW piping
Weil-McLain PLUS water heaters
For
PLUS water heater manual for application information.
Also see quick-select information on page 14. The infor-
mation here is for other water heater designs.
When using the Ultra boiler for dedicated DHW applica-
tions, use the circulator supplied with the boiler (007 for
Ultra-80/105; 0014 for Ultra-155/230/299; 2400-20 for
Ultra-399) to circulate to the water heater, except where
higher flow rates may be required for the heater used. Use
the following method to select a circulator for the water
heater on combined space heating/DHW systems.
1. To pipe the DHW tank and boiler, follow the suggested piping
diagrams beginning on page 12.
2. Figure 55, page 53 shows the pump curves for typical DHW circu-
lators. Use these curves along with boiler pressure drop data from
Figure 54, page 53 to size the DHW piping and circulator.
3. Procedure to select a DHW circulator:
Step 1
:
From the water heater manufacturer's data, find:
• Required boiler water flow rate, GPM, at 190°F.
• Pressure drop across the water heater at this flow rate, in feet
water column (this is H3 in the formula below).
Step 2
:
Find your boiler model in Figure 54, page 53.
Select a flow rate in the Flow rate column just larger than the
required boiler water flow rate from Step 1.
Step 3
:
Read across the row selected to find the boiler pressure drop, H1,
and the pressure drop in the piping, H2. Make sure to use the cop-
per pipe size given in column 3 when piping the water heater.
Step 4
:
Add the pressure drop across the water heater, from Step 1, to the
values of H1 and H2 for total head loss.
H = H1 + H2 + H3
total
Step 5
:
Select a circulator that can deliver the required flow rate, gpm,
against the total head loss found in Step 4.
Example
:
Consider an Ultra-155 used with a water heater that requires a
flow of 12 gpm with boiler water at 190°F. The water heater is to
be piped as in Figure 52.
From the example water heater manufacturer's data, the head loss
across the water heater at 12 gpm is 5.5 feet water column.
Read down the first column of Figure 54, page 53 for the Ultra-155
until you find a flow rate just larger than the required 12 gpm.
You'll find a value of 13 gpm in the third row.
At 13 gpm, with an Ultra-155, the recommended pipe size is
1¼ inch. From the table, the head losses are:
H1 = 13.3 feet
H3 = 5.5 feet (from water heater manufacturer's data)
H = 13.3 + 3.9 + 5.5 = 22.7 feet.
total
52
— Boiler Manual
, refer to the
H2 = 3.9 feet
The closest circulator selection (from Fig-
)
ure 55, page 53
22.7 feet head is either a Taco 1400/2400-30 (top
chart) or a Taco 0013 (bottom chart).
Note that, if the water heater were piped as in
Figure 53, then H1 would be 0, so total head loss
would be H2 + H3, or 9.4 feet (3.9 + 5.5). A Taco
0010 would handle the load if piped this way.
See previous pages in this manual for
piping details not shown below. For
DHW piping as shown below, use sizing
information in Figure 54, page 53.
Figure 52
DHW piping direct-connected across the
boiler
Figure 53
DHW piping as a secondary circuit — for
high-flow-rate applications
Part number 550-100-090/0809
that can deliver 12 gpm at