Buderus 500 - 28/C Servicing Manual page 57

box 172
±70 - 110 Ω
1
Set multimeter to "measure resistance".
Take a reading at the coils to check the internal electrical
resistance of the two gas valve coils. The electrical
resistance between the middle and lower contact must be
Ω
approx. 70 – 110 (item 1). The electrical resistance
between the middle and upper contact must be approx.
Ω
180 – 250 (item 2).
box 173
Fit the power supply plug to the gas valve.
Put the boiler into operation, see box 51, 54 or 55.
box 174 Replace the gas valve
A
DANGER OF FATAL ACCIDENT!
All work on gas pipework and gas-fitting components
must be carried out by a company registered and
authorised for this purpose.
Take the boiler out of operation and close the gas tap,
see box 43, 44, 46 or 47.
Remove the fan, see box 77, 78, 79 or 80.
box 175
1
Pull the gas injector (item 1) out of the gas valve.
We reserve the right to make technical modifications
Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006
±180 - 250 Ω
2
box 176
Fit the gas injector to the new gas valve.
Fit the new gas valve to the fan.
Fit the fan to the boiler, insert the air silencer tube into the
fan, fit the gas supply pipe to the gas valve and insert the
plugs into the fan and gas valve.
A
Fit the air silencer tube to the fan.
CAUTION!
When attaching the gas supply pipe to the gas valve,
ensure that the flat rubber seal is fitted correctly
between the gas supply pipe and gas valve.
Fit the gas supply pipe to the gas valve.
Insert the power supply plug into the gas valve, then insert
the power supply plug and tacho cable plug into the fan.
Open the gas cock and place the boiler into full-load
operation, see box 59, 54, 55 or 13.
Carry out a gas-leak check. Check the tightness of all
components that were loosened during removal of the gas
valve. Use an authorised foam-type leak detection product
for this purpose.
Remedy the cause of the gas leak.
Put the boiler into operation, see box 51, 54 or 55.
box 177 Check the ON/OFF or modulating control
function
Take the boiler out of service and tip the DBA control panel
forwards, see box 43, 44, 47 or 63.
Loosen the six screws and remove the rear section,
see box 70.
box 178
1
Room Controller
2
3
Hot water tank sensor
4
24 VAC 5
6
3-way valve
7
Room Controller
Hot water tank sensor
24 VAC
3-way valve
Bridge the two contacts, terminal 1 and 2.
Buderus Ltd. • http://www.buderus-domestic.co.uk
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