Drazice OKC 250 NTRR/SOL Manuel d'utilisation et d'installation - Page 9
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7. PRESSURE LOSSES
200
100
Heating
water
resistance
50
mbar
20
10
1
8. SECURITY EQUIPMENT
Each hot service water pressure heater must have a a membrane spring loaded with a safety valve.
Rated clearance of safety valve complies with the standard DN 20 for 251-1000 litre heaters.
Principles of safety valves fitting
Safety valve is mounted on a cold water inlet, no stop or throttling fitting shall be installed between the safety valve
and the heater.
The safety valve must be easily accessible, as close to the heater as possible. The inlet pipes must have at least the
same clearance as the safety valve. The safety valve is placed high enough to secure dripping water drain by gravity.
We recommend mounting the safety valve onto the branch led above the heater. This allows easier exchange without
having to drain the water from the heater. Safety valves with fixed pressure settings from the manufacturer are used
for the assembly. Starting pressure of a safety valve must be identical to the maximum allowed heater pressure, and at
least 20% higher than the maximum pressure in the water main. If the water main pressure exceeds such value, a
reduction valve must be added to the system. No stop valves can be put between the heater and the safety valve.
During the assembly, follow the guide provided by the safety equipment manufacturer. Connecting a heaters to
plumbing fixtures is shown on page 6.
It is necessary to check the safety valve each time before putting it into operation. It is checked by manual moving of
the membrane from the seat. Proper function of the make-and-break device results in water draining through the safety
valve outlet pipe. In common operation, such a check needs to be implemented at least once a month, and after each
heater shutdown for more than 5 days.
Water can drip from the safety valve through the drain pipe; the pipe must be freely open to the atmosphere, placed
vertically and shall be in an environment free of temperatures below freezing. When draining the heater, use a
recommended drain valve. First, close water input into the heater.
Find necessary pressure values in the following table.
2
1,5
Heating water flow m3/h
Průtok topné vody m3/h
Safety valve
Admissible operating
starting pressure
(MPa)
pressure (MPa)
0.6
0.7
1
3
Type
Exchanger 1m2
Exchanger 1,4m2
Exchanger 2m2
Max. pressure in
water heater
the cold water pipe
0.6
0.7
1
9
Exchanger with heat transfer
Výměník s teplosměnou
surface 2 m2
plochou 2 m2
Exchanger with heat transfer
Výměník s teplosměnou
surface 1,5 m2
plochou 1,5 m2
Exchanger with heat transfer
Výměník s teplosměnou
surface 1,4 m2
plochou 1,4 m2
Výměník s teplosměnou
Exchanger with heat transfer
plochou 1 m2
surface 1 m2
5
4
Presure loss (mbar)
tHV = 60 °C
Amount of heating water in m3/hr
1
2
7
24
51
9
32
68
12
88
42
(MPa)
do 0.48
do 0.56
do 0.8
3
4
5
86
130
115
174
149
226