Check Diaphragm Expansion Tank And System Pressure; Check Functioning Of Safety Valves - Viessmann VITODENS 100-W Installation And Service Instructions Manual

Initial Start-up, Inspection and Maintenance
Steps
(continued)
S
Start-up and Maintenance
ervice
S
Start-up and Maintenance
ervice
60

19. Check diaphragm expansion tank and system pressure

Perform check on the system when cold.
1. Drain boiler/system and reduce
pressure until the manometer reading
is "0".
2. If the nitrogen pressure of the
precharged expansion tank is less
than the static pressure of the
system, inflate membrane pressure
to slightly exceed pressure of
system.
The static pressure required at the
tank is based upon the static height
of the system. The system fill
pressure value must be equal to the
expansion tank pressure value at
approx. 60 ºF/15.6 ºC.
3. Top up with water until filling
pressure is higher than the inlet
pressure of the diaphragm expansion
tank.
4. When starting up the system for the
first time, mark this value as the
minimum filling pressure on the
manometer.

20. Check functioning of safety valves

Ensure proper operation of low water
cut-off(s) (if applicable), pressure relief
valve, and pump(s).
Check pressure gage, air vent and
pressure relief valve. Ensure that
pressure relief valve does not leak and
that it operates in accordance with
information provided by the original
manufacturer.
Example
Static head of 33 ft./10 m
(distance between boiler and
topmost heat emitter surface)
corresponds to a static
pressure of 1 bar/15 psig.
With the system cold, the filling
pressure must be approx. 3 psig
higher than the static pressure.
Max. boiler
operating pressure .............45 psig
Min. boiler
operating pressure ......14 to 23 psig
Pressure relief valve..............30 psig
A lower manometer reading usually
indicates loss of water due to
leakage. All leaks must be repaired.
Refer to maintenance instructions
supplied with low water cut-offs,
pumps, etc.
Flush float water type low water
cut-offs (if used).
Follow local regulations with respect to
backflow preventers.
If oil-lubricated pumps are used, ensure
proper lubrication.
If motorized zone valves are used, refer
to maintenance instructions provided
with zone valves.