Technical information

Combi 70 & Combi 90 Oil Boilers

Fig. 37 - Boiler components (plinth and pipework cover removed for clarity)

5 Close the primary return isolating valve (B) and the

pump isolating valve (D). Refer to Fig. 38 or 39.

6 Remove the spring circlip holding the microswitch

assembly to the diverter valve, and separate the

microswitch assembly from the valve.

7 Unscrew and disconnect pipe unions 1,2 3,4,5 & 9.

See Fig. 38 or 39. Remove the vertical 15 mm pipe

from the boiler to gain access to pipe union 6.

Unscrew the union and remove the plate heat

exchanger with diverter valve attached.

8 To separate the plate heat exchanger from diverter

valve, unscrew the two union nuts 7 & 8. See Fig.

38 or 39.

9 Re-assemble and refit using the reverse procedure,

ensuring all sealing washers are correctly fitted.

10 Open the cold water inlet valve (A) and primary

return isolating valve (B) and pump isolating valve

(D). Refill the central heating system as described

in section 5.2, checking for leaks.

11 Open a hot tap and check that the diverter valve is

activated and operates both microswitches.

9 - REPLACEMENT OF BOILER COMPONENTS

8 Fit a replacement pump using the reverse of the

above procedure, ensuring the sealing washers are

correctly fitted in the pump unions, and that pump

flow direction (as indicated by arrow on pump

body) is correct. Set the pump speed selector

switch to maximum.

9 Open the pump isolating valve and the primary

return valve, then refill the central heating system

as described in section 5.2, checking for leaks.

1 Unhook the expansion vessel from the front of the

boiler and lay to one side.

2 Unscrew and remove the single burner fixing nut

(located above the burner, in the middle of the

mounting flange) and withdraw the burner from the

boiler and lay it to one side.

3 Close the cold water inlet isolating valve (A). Refer

to Fig. 38 or 39.

4 Manually operate the safety valve on top of the

boiler heat exchanger to de-pressurise the boiler. It

is not necessary to drain down the heating system.

Plate heat exchanger & diverter valve

9.2