Infloor 31075, 31076, 31077 User Manual
Code A B C D E
(lb)
1” FNPT
1” MNPT
3
13/16
”
2
1/16
” 6
5/8
” 1.4
31076
1” FNPT
1” SWT
2
”
2
” 6
” 1.4
1
”
FNPT
1
” MNPT
3
”
2
” 7
” 1.5
E B D E B D
E B D E B D E B D
Differential Pressure By-Pass Valve
Code A B C D E
(lb)
31075
3/4” MNPT
3/4” MNPT
2
” 1
” 5” 1
31075-31077 series
BS EN ISO 9001:2000
Cert. n∞ FM 21654
UNI EN ISO 9001:2000
Cert. n∞ 0003
01007/09 NA
Function
The differential pressure by-pass valve is used in systems with a
fixed speed circulating pump supplying several zones controlled
by two way zone valves. This valve ensures that the head pressure
of the pump is proportional to the number of two way valves being
closed. It will bypass the differential pressure created by the pump
as the zone valves close, thus eliminating water hammer noise.
31077
Product range
Part # 31075 Adjustable differential pressure by-pass valve with graduated scale, flow up to 9 gpm Size 3/4" Sweat x 3/4" Sweat outlet
Part # 31076 Adjustable differential pressure by-pass valve with graduated scale, flow up to 40 gpm Size 1” Female NPT x 1” sweat outlet
Part # 31077 Adjustable differential pressure by-pass valve with graduated scale, flow up to 45 gpm Size 1 1/4” Female NPT+1 1/4” sweat outlet
Technical specifications
Materials
Body: brass
Valve plug: brass
Valve plug gasket:
O-R ing
seals:
Union seals: asbestos free NBR
Control knob:
Spring: stainless steel
Dimensions
519
502A
519
599A
2
3
4
5
mH2O 6
1
A
C
3/4” SWT 3/4” SWT 2
2
3
4
5
1/4
1/8
” 2
31075
1
mH2O 6
A
7/8
1/2
” 5
Performance
Medium: water, glycol solutions
EPDM
EPDM
ABS
C
Weight
9/16
” 1
Max percentage of glycol: 30%
Temperature range: 32–230°F (0–110°C)
Maximum working pressure: 150 psi (10 bar)
Flow rates: 3/4” flow up to 9 gpm
1” flow up to 40 gpm
1 1/4” flow up to 45 gpm
Setting range: 1 - 6 m w.g. (2 - 10 psi)
519
600A
519
700A
1
2
3
4
5
mH2O 6
A
31077 1
C
1/4
1/4
”
FNPT
519
4
5
1/4
1
1/4
” SWT 3” 2
609A
1
2
3
mH2O 6
A
C
13/16
15/16
519
709A
4
5
1/16
11/16
11/16
” 7
1
2
3
mH2O 6
A C
Weight
5/8
3/8
3/8
” 1.5
TOT
AL
LOAD
➪
P
A
RTIAL LOAD
Operating principle
When the spring (1) compression is adjusted using the control knob (2), the force
balance acting on the valve plug (3) changes, thus modifying the threshold pressure
value of the valve. The valve plug opens, activating the by-pass circuit, only when it is
subjected to a differential pressure sufficient to generate a thrust greater than the thrust
exerted by the spring. This allows the flow discharge through the outlet (4), limiting the
difference in pressure between the two points in the system where the valve is fitted.
2
5
1
3
➪
➪
System operation
The job of the differential pressure by-pass valve is to maintain the
pump operating point as close as possible to its nominal value (point
A on the graph shown below). If the by-pass valve is not used, when
the flow rate in the circuit decreases due to partial closure of the twoway zone valves, the head loss in the circuit increases, point B.
The by-pass valve, set to the nominal head value of the pump, limits
the increase in pressure, by-passing the flow rate ∆G. This behavior
is guaranteed at any closing condition of the system two-way zone
valves. In fact, once the posit i on of the valve control knob has been
established, the threshold pressure value is more or less constant
as the discharge flow rate varies (see hydraulic characteristic
diagrams).
A proper valve sizing must guarantee a sufficient flow rate by-pass to
keep the pump at its nominal operating point in all system operating
conditions, for example when the first zone valves are closed.
∆p
∆p
NOMINA L
Circuit resistance curve
with two-way valves
partially open
B
∆p constant
on the circuit
Pump curve
A
Circuit resistance curve with
two-way valves fully open
50%
∆G
100%
Flow rate G
Setting
To regulate the valve, turn the knob to the required value on the
graduated scale: the values correspond to the differential pressure in
psi or meters w.g. to open the by-pass.
For a quick setup adjustment of the differential pressure by-pass
valve, use the following manual method. As an example, a hydronic
system with several zone valves: the system must be operating, the
zone valves must be fully open and the by-pass valve must be set to
the maximum value (a) (clockwise). Gradually open the differential
pressure by-pass valve using the control knob (counterclockwise).
Use a thermometer, or simply your hand, to check that the hot water
is flowing into the by-pass circuit (b). As soon as a rise in the
temperature is noted, turn control knob (clockwise) one half turn
closed so hot water stops flowing into the by-pass (c). Lock the knob
in this position (d) with the locking screw.
4
a) b)
Two-way
1 1
2 2
3 3
4 4
5 5
mH2O 6 mH2O 6
3 3
4 4
5 5
mH2O 6 mH2O 6
1
2
c) d)
1
2
3
4
5
mH2O
6
1
2
3
4
5
mH2O 6