Potter Releasing Systems - Manual (Page 38)

38
Dry Pipe Systems
Waterflow Switch - Pressure Type
Unless an annual trip test is being done, open the alarm by-pass valve. This will allow water to flow from the water
supply directly to the pressure type flow switch, as soon as the pressure reaches 6 psi, the flow switch should trip. This
is usually a 1/2” or 3/4” ball valve. On most systems there will be two ball valves between the pressure switch and
the alarm valve. One of these is the normally closed by-pass valve that is only opened for testing. The other valve is a
normally open alarm shut-off valve. It is used to either silence the pressure switch in an actual alarm or to disable it if
water must be flowed into the system.
Low Air Supervisory Switch
The low air switch should have a bleeder valve installed in line with the switch and a pressure gauge. A bleeder is a
1/2” ball valve with a small orifice drilled in one end of the valve. When the valve is closed it bleeds off the air pressure
between the valve and the pressure switch. A pressure gauge should be installed on the pressure switch side of the
bleeder valve so it can be determined at exactly what pressure the switch trips at. The low pressure switch should trip
at 10 psi below the normal air pressure which should also be 10 psi above the trip point of the dry pipe valve. After the
switch trips, open the bleeder valve.
If a bleeder valve is not installed: Shut off the water supply to the system. Shut off the air compressor. Slowly bleed air
off the system while observing the the pressure gauge so it can be determined at what pressure the low air switch trips
at. To bleed air off, a pipe union may need to be loosened or the inspector’s test valve partially opened. After the switch
trips, close the inspector’s test valve or tighten the pipe union, turn on the air compressor. After the air pressure returns to
normal, very slowly open the water supply valve.