December 2008 - Plumbing & HVAC

Pipes, Valves & Fittings
Sizing circulators
in hydronic systems
By Art Irwin
Pipe sizing and
circulator sizing
are critical
for hot water heating
systems. One
must first ensure the
piping is properly
sized to carry the
hot water from “A” to “B” or, in other
words, from the heating boiler to the
radiation via the piping system.
There are, of course, hundreds of
sizes of circulators, but it is important
the circulator be properly sized to deliver
the required number of BTU’s, carried
in gallons of water per minute
(gpm), to its destination. If the circulator
is too large or too small, we get into
velocity or noise problems, insufficient
heat, cavitation and pump failure.
There are two issues that must be
addressed when sizing circulators. First,
how many gallons per minute must the
circulator pump to deliver the maximum
heat?
Item number two – what is the
“head” or resistance the circulator must
overcome? There a are a number of
things that can cause “bumps in the
road” – length of piping, elbows, tees
and friction loss. (Refer to the chart at
right for pipe carrying capacity in
To obtain the required gallons per
minute (GPM), divide the total Btu’s
by 10,000:
BTU Heat Loss = Gallons per minute.
10,000
Example:
200,000 Btu/hr.= 20 Gal/Min.
10,000
Btu/h.)
Determining pump head
How do we determine the pump head?
Here’s a quick way to do it. It’s not 100
percent accurate, but close enough for
quick sizing. We must take the total
equivalent length, which means measuring
to the most distant radiator from
the boiler, and back, plus 50 percent,
and multiply x .04
PIPE CARRYING CAPACITY
For Mains For One And Two Pipe Systems
Piper Size – Inches
BTU Capacity
1/2 15,000 – 13,000 –12,000
3/4" 31,000 – 30,000 – 27,000
1” 59,000 – 53,000 – 48,000
1 ¼” 130,000 – 118,000 – 102,000
1 ½ 185,000 – 175,000 – 156,000
2” 360,000 – 322,000 – 294,000
2 ½” 610,000 – 551,000 – 523,000
3” 1,150,000 – 1000,000 – 900,000
Note: Use BTU center column as a BTU average.
Source: B&G Eng. Manual 1954
Here’s an example: boiler out to the
most distant radiator, 80 feet and back
80 feet = 160 feet plus 50 percent (80 ft.)
for a total of 240 feet. Multiply 240 x .04
= 9.6 or 10-foot head.
Therefore, we must purchase a pump
with a capacity of 20 gallons per minute
against a 10-foot head.
Arthur A. Irwin operates Irwin Energy
Consulting Services in Halifax. He can be
reached at irwin.a@ns.sympatico.ca.
ProPress butterfly valves
Viega has added three new butterfly
valves to its ProPress press-fit product
line. The new valves are semi-lug bodies
with EPDM liners, stainless steel disc
and stem, with a ten-position handle.
They are available in 2-1/2”, 3” and 4”
sizes. The valve addition compliments
the existing 550 bronze and copper
ProPress fittings offered in the Viega
ProPress product line.
Viega Circle no. 317
Two-inch plastic fittings
The new two-inch engineered plastic
(EP) fittings from Uponor are designed
to offer a durable solution for commercial
plumbing applications. The line
includes tees, elbows and couplings that
work with the company’s AQUAPEX
tubing. They are immune to corrosion,
pitting and scaling; resist the damaging
effects of aggressive water; and address
future NSF lead-content initiatives and
code requirements.
Uponor Circle no. 318
New firestop formula
Tremco Commercial Sealants &
Waterproofing (CS&W)
has introduced a new
formula for its
TREMstop IA intumescent
water-based acrylic
firestop sealant. It is
designed to provide
more coverage with less
material. It can be
installed around a fourinch
plastic pipe without
requiring a collar, sleeve
or backer rod, reports
the manufacturer. It
expands to fill the voids
left when combustible
materials burn and deteriorate in a fire.
Tremco Circle no. 319
New bronze Y-strainer
The new Class 125 Cast Bronze Y-
strainer line from Nibco are designed
for commercial applications to trap foreign
matter in steam, water, oil or gas
pipelines. It includes solder ½” – 2” and
threaded ¼” – 3” sizes rated 125 SWP /
200 CWP. Features in clude a solid or
tapped cap with
plug, a stainless
steel 20 mesh or
perforated
stainless steel
screen and a
dezincification-resistant
cast bronze body.
Nibco Circle no. 320
Circle Number 125 for More Information
www.plumbingandhvac.ca November/December 2008 – Plumbing & HVAC Product News 27