Tunstall Macon STV Series Manual page 71

STANDARD APPLICATION
PVM is fitted in the intake, the signal pipe is to be
connected at the low pressure side of the STV valve, The
valve can be fitted irrespective of whether it is a straight
length of pipe. Bends, tubes etc. can be
installed immediately after the valve.
1. Flush the valve before fitting signal pipe
2. Install t-pipe with measurement socket on the STV valve.
3. Install signal pipe, on the t-pipe and flush to ensure that
there is no air in the signal pipe.
4. Install the signal pipe on the PVM valve on
the return pipe.
DIMENSIONING
Selecting the right valve in an installation requires
some data about the system.
△P pump available differential pressure from pump
△P load differential pressure for circulation
△P STVP pressure drop over valve fully open (diagram)
△P PVM
pressure drop over the PVM valve
(diagram)
Example:
Calculated value for a valve is 6.34 gpm.
7.25 psi is available differential pressure for
circulation △P load 2.9 psi is required for the main.
We find the minimum differential pressure required for the
PVM valve to achieve minimum working pressure in the dia-
gram.
Two valves can deliver 6.34 gpm 1" and 1 1/4".
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
ADJUSTMENT AND MEASURING
When adjusting the differential pressure on the PVM valve,
measure and adjust to 10 kPa, making sure at least one radia-
tor valve is slightly open.
When measuring the flow, use the STV valve and a measur-
ing tool. The STV valve's wheel may be set lower to have a
higher differential pressure over the PVM valve. Note that the
differential pressure over the STV valve will not be too high
so that the min differential pressure over the PVM valve will
be to low and the PVM valve will stop regulating. Open the
STV valve completely after measuring the flow.
OPTIMIZING PUMP PRESSURE
Lowering to minimum possible pump differential pressure is
carried out by measuring at the PVM valve and obtaining at
least 1.91 psi, this is the pump's lowest level at which the
PVM can be regulated.
118 Exchange Street · Chicopee, MA 01013
Phone (413) 594-8695 · Fax (413) 598-8109
Section: Components
71
Tunstall Corporation
Bulletin-MB-PVM-0915