"Heliotrope Smith" wrote in message
...

Filling:
1. Close drain valve, and open cold water feed.
2. Anything else???

Open hot tap and leave open until all air is expelled.

Do these things come with an instruction book? If so, I have no idea
where
ours is, assuming that the builders ever left it.

Ah, many thanks! I eventually tracked down the installation manual, which
says this (just in case somebody else needs to know at some time in the
future):

8.4 DRAINING THE MEGAFLO UNIT

Switch off the electrical supply to the immersion heater(s) and shut down
the boiler on

indirect units. Turn off the mains water supply to the Megaflo unit. Attach
a hosepipe to the drain

cock having sufficient length to take water to a suitable discharge point
below the level of the unit, at

least one metre below the unit is recommended. Open hot water tap nearest to
the Megaflo to relieve

the system pressure. Open drain cock. If water fails to drain from the
Megaflo vent the unit by

manually opening the Temperature/Pressure Relief Valve.

8.5 DESCALING IMMERSION HEATER(S)

Open the cover(s) to the immersion heater housing(s) and disconnect wiring
from immersion heater(s).

Remove the thermostat by carefully pulling outwards from the immersion
heater. Unscrew immersion

heater backnut(s) and remove immersion heater from the unit. A key spanner
is supplied with the

Megaflo unit for easy removal/tightening of the immersion heater(s). Over
time the immersion heater

gasket may become stuck to the mating surface. To break the seal insert a
round bladed screwdriver into

one of the pockets on the immersion heater and gently lever up and down.

Carefully remove any scale from the surface of the element(s). DO NOT use a
sharp implement as

damage to the element surface could be caused. Ensure sealing surfaces are
clean and seals are

undamaged, if in doubt fit a new gasket.

Replace immersion heater(s) ensuring the lower (right angled) element hangs
vertically downwards

towards the base of the unit. It may be helpful to support the immersion
heater using a round bladed

screwdriver inserted into one of the thermostat pockets whilst the backnut
is tightened. Replace the

thermostat(s) by carefully plugging the two male spade terminations on the
underside of the thermostat

head into the corresponding terminations on the element.

Rewire the immersion heater(s) in accordance with Diagram 8. Close and
secure terminal cover(s).

8.6 REFILLING SYSTEM

DO NOT switch on the immersion heater(s) or boiler until the system has been
completely refilled.

Close the drain tap. With hot tap open, turn on mains water supply. When
water flows from the hot

tap allow to flow for a short while to purge air and to flush through any
disturbed particles. Close hot

tap and then open successive hot taps in system to purge any air. The
electrical supply can now be

switched on.