Tunstall Macon STV Series Manual page 70

SETTING THE VALVE
The valve is easy to set on the knob using a 4 mm Allen key.
The setting is read off the pressure drop diagram for each
dimension. When presetting the valve, start by screwing the
setting to minimum. Then open the valve to the required
value according to the diagram. The STV valve is used solely
for shutting off and flow measurement, it must not be set in
any position other than open.
Presetting
The PVM valve is preset according to the diagram.
The curves (the oblique lines that indicate the pressure in the
main line) are shown in intervals of 0.73 psi to make it simple
to take a reading. The curves can be moved so that the valve
setting can be produced if, for example, 1.74 psi is selected in
a pipe instead.
Example: We decide to maintain 1.74 psi differential pres-
sure in the main at a flow of 2.2 gpm
(2.2 gpm comes from the presetting on the radiators).
From the point where 1.74 psi cuts the horizontal line flow
2.2 gpm) a vertical line is taken down to the x-axis. It is then
easy to read off that the valve should be set at approx. 7 turns.
The minimum pressure drop will then be 0.28 psi over the
valve.
INSTALLATION EXAMPLE
Overview of a heating system with 5 stair-
cases with 4 apartments on each one.
The critical valve, defined as the valve with
the lowest pressure drop as a rule of thumb
this will be the valve positioned furthest
away from the pump, is used to lower the
pump pressure so that the valve achieves
the correct pressure. The lowest possible
pressure is then obtained in the system.
See dimensioning pump pressure.
cv-value of the STV Valve
Number
1/2" 3/4"
of Turns
1 0.21 0.39
2 0.37 0.69
3 0.52 0.96
4 0.72 1.31
5 0.99 1.79
6 1.35 2.43
7 1.87 3.35
8 2.95 4.45
9 3.64 5.20
10 4.10 5.90
We reserve the right to alter information without notice.
Optional features and accessories available for this
Macon product are an extra charge, and not included
in the standard model price.
www.maconbalancing.com
Series PVM
1" 1-1/4" 1-1/2"
0.55 0.91 1.39
0.89 1.53 2.37
1.19 2.08 3.24
1.73 3.12 4.74
2.66 4.74 7.17 13.76
4.16 6.82 10.29 19.31
5.78 9.02 13.87 24.51
7.51 11.21 16.99 28.90
9.13 13.30 19.77 33.06
10.17 15.14 22.54 36.42
Total pressure drop:
To dimension the pump it will be:
△Ps + △Pv = △P
1.74 +0.28 = 2.02 psi
Also include the pipe pressure drop from the valve to the
pump.
The pump can subsequently be adjusted optimally
by measuring the differential pressure from PF to
P- ( P pump). To verify the secondary pressure
drop calculated, it can be checked by measuring
PF to P+ and the result should then be 1.74 psi.
2"
2.31
4.16
6.01
8.79
118 Exchange Street · Chicopee, MA 01013
Phone (413) 594-8695 · Fax (413) 598-8109
Section: Components
70
Tunstall Corporation
Bulletin-MB-PVM-0915