23
3 Use and maintenance
3.1
PRELIMINARY CHECKS UPON
COMMISSIONING
When carrying out commissioning of the boiler, you are
recommended to perform the following checks:
– make sure that the system is charged with water and
is thoroughly vented;
– make sure that any shutoff valves are open;
– check that the pipe for expulsion of products of combu-
stion is unobstructed and has been properly installed;
– make sure that the boiler is set for operation for the
type of gas supplied;
– open the gas tap and check the soundness of the
connections including that of the burner;
– purge the system, bleeding off the air present in the
gas pipe by operating the pressure relief valve on the
gas valve inlet;
– make sure that the electrical connections have been
made correctly and that the earth wire is connected to
a good earthing system;
– check that there are no liquids or inflammable mate-
rials in the immediate vicinity of the boiler.
3.1.1
Temperature adjustment of D.H.W.
The
“MURELLE”
boilers (except for
“20 R - 20 BFR”
models) are equipped with a potentiometer for adjusting
the temperature of D.H.W. with a setting range from 35°C
to 60°C. This system offers a double advantage:
1) the boiler adapts perfectly to any type of D.H.W.
system, whether the mixing system is a mechanical or
a thermostat-controlled type;
2) the thermal output is dosed according to the temperatu-
re required, which means a considerable saving in fuel.
NOTE: In order to avoid any misunderstanding plea-
se the remember that the value obtained by the pro-
duct of temperature difference (in °C) between D.H.W.
output and input into the boiler by the hourly flow rate
measured on the tap, where hot water is drawn off
(l/h), cannot be higher than the useful output develo-
ped by the boiler. For measurements and checks on
flow rate and temperature of D.H.W., use suitable
instruments, taking into consideration any heat
dispersion along the stretch of piping between the
boiler and the measuring point.
3.1.2
Adjustment of D.H.W. flow rate
The
“MURELLE”
boilers (except for
“20 R - 20 BFR”
models) have a three-way hydraulic valve of the pressure
switch type (Fig. 28), which, when at rest, keeps the
system delivery flow open, whereas it switches instanta-
neously to the recirculation position, shutting off heating,
upon demand for D.H.W. To adjust the hot water flow rate,
use the flow-rate regulator (2) on the pressure switch valve.
Remember that the flow rates and corresponding tempe-
ratures of use of hot water, given in Table 2, have been
obtained by positioning the selector of the circulation
pump on the maximum value.
NOTE: Should there be any reduction in the D.H.W.
flow rate, the filter (4) installed on the inlet to the pres-
sure switch valve will need cleaning.
To gain access to the filter, first close the shutoff cock
for cold water intake located on the fixing jig and then
loosen the brass swivel connection (5).
3.2
DISASSEMBLY OF EXPANSION VESSEL
To disassemble the expansion vessel, proceed as follows
(Fig. 29):
– make sure that the water has been emptied out of the
boiler;
– unscrew the connection (1) connecting the expansion
vessel to the boiler;
– unscrew the screw retaining the bracket (5) to the
frame assembly, remove the bracket and the expan-
sion vessel (2).
NOTE: Before refilling the system, using a pressure
gauge attached to the valve (3) make sure that the expan-
sion vessel is preloaded at a pressure of 0.8 to 1 bar.
KEY
1 Pressure switch valve
2 Flow-rate regulator
3 Microswitch
4 Filter
5 Swivel connection 1/2”
6 Gasket ø 11,5/18,5
7 Water pressure switch
Fig. 28
KEY
1 Connection 3/4”
2 Expansion vessel
3 Expansion vessel
preloaded valve
4 Screw M5x16
5 Fixing bracket
Fig. 29
