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We reserve the right to make technical modifications
Buderus Ltd. • http://www.buderus-domestic.co.uk
64
Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006
box 220 Check the Buderus 24V AC external
3-way valve – power supply cable
A
CAUTION!
To prevent damage, do not insert the measuring
electrodes of the multimeter too far into the holes of the
plug-and-socket connection.
z
Take the boiler out of operation, see box 43 or 44.
z
Remove the power supply plug of the servomotor of the
Buderus 24V AC external 3-way valve, see box 213.
z
Remove the connection of the power supply cable of the
Buderus 24V AC external 3-way valve at the boiler.
z
Set multimeter to “measure resistance”.
z
Check the power supply cable of the Buderus
24V AC external 3-way valve for breaks. The electrical
resistance measured at each individual wire must be
approximately 0
Ω
.
z
Check the power supply cable of the Buderus
24V AC external 3-way valve for internal short circuits. The
level of electrical resistance, measured between two wires
chosen at random, must be infinitely high.
z
Insert the power supply plug of the Buderus
24V AC external 3-way valve.
z
Connect the power supply cable of the Buderus 24V AC
external 3-way valve at the boiler.
z
Put the boiler into operation, see box 54 or 55.
box 221 Check the Buderus 24V AC external
3-way valve – drive mechanism
z
Take the boiler out of operation, see box 43 or 44.
z
Remove the servomotor of the Buderus 24V AC external
3-way valve, see box 218.
box 222
z
Check to ensure that the drive mechanism of the Buderus
24V AC external 3-way valve is running smoothly. This is
done by gradually pushing the spring fully home by hand
and allowing the spring to return gradually to its home
position.
box 223
z
Refit the servomotor, following the above procedure in
reverse order.
z
Put the boiler into operation, see box 54 or 55.
box 224 Replace the Buderus 24V AC external 3-way
valve – drive mechanism
z
Take the boiler out of operation and drain the heating
system, see box 48 to 51.
z
Remove the servomotor of the Buderus 24V AC external
3-way valve, see box 213 or 218.
box 225
z
Remove the drive mechanism of the Buderus
24V AC external 3-way valve using the wrench supplied
with the drive mechanism.
A
CAUTION!
Note that water will squirt out when the drive
mechanism is removed.
Have a bucket and a supply of dry cloths to hand.
box 226
z
Fit the new drive mechanism to the Buderus
24V AC external 3-way valve.
z
Connect the servomotor of the Buderus 24V AC external
3-way valve by following the above procedure in reverse
order.
z
Fill the heating system, vent it of air and place the boiler
into operation, see box 52 to 58.
box 227 Check the Buderus 24V AC external
3-way valve – installation
z
Use the letters marked on the 3-way valve to check
whether the Buderus 24V AC external 3-way valve is
correctly fitted:
A
= flow of storage-type water heater
B
= CH flow
AB
= boiler flow
