Raypak MVB 503-2003 - Manual (Page 30)

Freeze Protection
The Raypak electronic temperature control includes a
freeze protection feature. In the event the temperature
drops below 40°F at any of the boiler temperature sen-
sors, the pump is turned on and will remain on until the
temperature at all boiler sensors rises to 45°F.
Controls
30
Fig. 29: Outdoor Venting
The Raypak modulating temperature control is pro-
vided to maintain the desired system water
temperature. The control has various modes of opera-
tion which are listed on the following pages.
Setpoint: The intended system supply temperature.
Deadband: Deadband is a band of temperature sens-
ing where no action occurs. All temperature controllers
have a deadband and the purpose is to prevent short-
cycling of the heater. The on-board temperature
controller has a deadband of 2ºF around the differen-
tial.
Differential: A heat source must be operated with a
temperature differential in order to prevent short-
cycling. The temperature differential is divided around
the “target” temperature or set-point. The Call For Heat
(CFH) contact will close in the controller when the
water temperature is below the target temperature by
1/2 of the differential setting, and will open when the
water temperature is above the target temperature by
1/2 of the differential setting. See Fig. 30.
Operating Modes
Mode 1 (Not supported) – Setpoint operation using
primary piping. The heater outlet water temperature is
controlled to the boiler target setpoint.
Mode 2 – Setpoint operation using primary/secondary
piping. The control operates the heater to satisfy a
remote system sensor. The heater is turned off based
on boiler max and boiler differential (factory default).
See Fig. 31.
WARNING: Installation, adjustment and service of
heater controls, including timing of various operating
functions, must be performed by a qualified installer,
service agency or the gas supplier. Failure to do so
may result in control damage, heater malfunction,
property damage, personal injury, or death.
WARNING: Turn off the power to the heater before
installation, adjustment or service of any heater
controls. Failure to do so may result in board
damage, heater malfunction, property damage,
personal injury, or death.
CAUTION: This appliance has provisions to be
connected to more than one supply source. To
reduce the risk of electric shock, disconnect all such
connections before servicing.
CAUTION: Risk of electric shock: More than one
disconnect switch may be required to de-energize
the equipment before servicing.
NOTE: Condensate can freeze on the vent cap.
Frozen condensate on the vent cap can result in a
blocked flue condition.
Fig. 30: Differential Graph