14
FLOW SWITCH
The flow switch is a safety device which must be installed at the
water outlet of the unit to prevent main burner operation in the
event of inadequate water flow through the unit.
An accessory package containing a flow switch is available for
this application.
This switch may be mounted in a horizontal pipe line or a vertical
pipe line with upward water flow. Do not install the switch where
the water flow is downward.
For proper performance mount the switch in a section of pipe where
there is a straight run of at least 5 pipe diameters on each side
of the flow switch (i.e. do not locate adjacent to valves, elbows,
orifices, etc.).
The flow switch shall be mounted in a standard 1-1/2" x 1-1/2"
x 1" tee for a 1-1/2" pipe application. For larger pipe sizes use
a reducing tee in order to keep the switch as close to the pipe
as possible. Install the flow switch in the branch (top) opening of
the reducing tee and provide adequate paddle length in the flow
stream. For example in a 2" pipe installation use a 2" x 2" x 1"
reducing tee. For 2", or 3" pipe use paddle segments as supplied.
For other pipe sizes (i.e. 1-1/4", 1-1/2" and 2-1/2") trim the paddle
to the proper pipe size, see Figure 9 below. If a standard tee is
used, install a face or hex bushing in the top opening. The paddle
must be adjusted or trimmed to the size of the pipe in which it will
be installed.
Any part of the paddle must not touch the pipe or any restrictions
in the pipe. Screw the flow switch in position so the flat of the
paddle is at right angles to the flow. The arrow on the side case
must point in the direction of the flow.
Minimum Pipe Rate
Model Number
Contacts Closed
(Flow)
Contacts Open
(No Flow)
GPM
LPM
GPM
LPM
HW-300
5.8
22.0
3.7
14.0
HW-399
7.5
28.4
5.0
18.9
HW-420
7.5
28.4
5.0
18.9
HW-520
13.7
51.9
9.5
36.0
HW-670
13.7
51.9
9.5
36.0
The flow switch may be field adjusted to obtain higher minimum
flow rates than those shown inTable 9.
To adjust the flow rate setting:
1. Remove the flow switch cover.
2. For higher flow rate - turn the range adjusting screw
clockwise.
3. For lower flow rate-turn the range adjusting screw
counterclockwise.
The switch is factory set at approximately the minimum flow rate,
refer to Table 9. It must not be set lower than the factory setting
as this may result in the switch failing to return at a 'no flow'
condition.
4. Replace flow switch cover. Where units are installed in
multiples, each boiler must be individually protected by a flow
switch.
TABLE 9. FLOW SWITCH
FIGURE 9. FLOW SWITCH