Raypak MVB 504A, Installation & Operating Manual

Page: 37 / 64

37
Standard
The fixed setting manual reset high limit is built into the
PIM™, it utilizes a dual element sensor located on the
outlet (see Fig. 38). To reset a high limit lock-out, press
and release the RESET button located on the user
interface.
High Limit—Auto Reset (Optional)
This heater may be equipped with an optional adjust-
able auto reset high limit temperature device.
The optional adjustable auto reset high limit is located
inside the cabinet on the upper left corner post.
Access the limit by hinging the control box open to
view and make adjustments. Adjust the setting to
approx. 20°F (10°C) above desired outlet temperature.
Fig. 39: Adjustable High Limit (Auto Reset)
Flow Switch
This standard, dual-purpose control, mounted and
wired in series with the main gas valve, shuts off
heater in case of pump failure or low water flow.
Fig. 40: Flow Switch
Low Water Cut-Off (Optional)
The optional low water cut-off automatically shuts
down the burner whenever water level drops below the
level of the sensing probe. A 5-second time delay pre-
vents premature lockout due to temporary conditions
such as power fluctuations or air pockets.
Fig. 41: Low Water Cut-Off
High & Low Gas Pressure Switches
(Optional)
The optional low gas pressure switch mounts
upstream of the gas valve (on the inlet flange to the
gas valve) and is accessible through the removable
access panels on the side or front of the heater to
reset the gas pressure switch, as necessary. It is used
to ensure that sufficient gas pressure is present for
proper valve/regulator performance. The low gas pres-
sure switch automatically shuts down the heater if gas
supply drops below the factory setting of 3.0 in. WC for
natural gas or propane gas.
The optional high gas pressure switch connection
mounts down-stream of the gas valve. Special ports
are located on the backside of the gas valve and
accessible from the front of the heater (to reset the gas
pressure switch) or through the removable access
panels on the rear of the heater (to reset the gas pres-
sure switch), as necessary. If the gas pressure
regulator in the valve fails, the high gas pressure
switch automatically shuts down the burner.
Operation of either the High or Low Gas Pressure
Switch will turn on an LED inside the switch housing.
Push the top of the plastic switch housing as shown in
Fig. 42 to reset a tripped pressure switch. The LED
will go out when the switch is reset.
Fig. 42: High/Low Gas Pressure Switch