APR 2018
23
Hot Water Energy Storage
Unvented Cylinders
GB & NI
Installation & Maintenance Instructions for an unvented
hot water cylinder with external thermal expansion
Table 6:
Fault finding
Fault
Possible Cause
Solution
Water escaping from the case
Compression fitting on hot draw-off not sealing
Check/remake joint with sealing paste
Leaking cylinder
Isolate supply and contact us
Cold water at hot taps
Direct - immersion heater not switched on or cut-out has
triggered
Check / reset
Indirect - boiler not working
Check boiler - consult boiler manufacturer’s instructions
Heat pump not working
Check heat source - consult heat pump manufacturer’s
instructions
Indirect - motorised valve fault
Check plumbing / wiring to motorised valve
Indirect - cut-out in dual stat has operated
Reset and investigate cause
Water discharges from expansion
relief valve
If continual - pressure reducing valve (part of inlet control set)
may not be operating correctly
Check outlet pressure from inlet control set is 3 bar
If continual - expansion relief valve seat may be damaged
Remove cartridge - check seat and renew if necessary
If intermittent - expansion vessel charge may have reduced /
bladder perished
Check pressure in expansion vessel. Recharge to 3 bar if
necessary. If bladder perished replace vessel
Unit is being back pressurised
With cylinder cold check pressure in cylinder. If this is the same
as the incoming mains pressure then you are getting backfeed.
Install a balanced cold supply (see page 7)
Water discharges from temperature
& pressure relief valve
Unit has overheated - thermal controls have failed
Switch off power to boiler and immersion heaters.
Leave water supply on. Wait until discharge stops.
Isolate water supply and replace if faulty
Milky / cloudy water
Oxygenated water
Water from any pressurised system will release oxygen bubbles
when flowing. The bubbles will settle out
No hot water flow
Cold mains off
Check and open stopcock
Strainer blocked in pressure reducing valve
Isolate water supply and clean
Inlet control set may be fitted incorrectly
Check and refit as required
Noise during hot water draw-off
-typically worse in the morning
Loose pipework
Install extra clips
Water hammer
Fit a shock arrestor
Hot or warm water from cold tap
If tap runs cold after a minute or so the pipe is picking up heat
from heating pipework
Insulate / re-route
GENERAL
Servicing should only be carried out by competent installers
and only spare parts approved by the manufacturer may
be used. Never bypass any of the safety devices and never
operate the unit without all of the safety devices being in
place and fully operational.
DRAINING
Isolate from the electrical supply to prevent the immersion
heaters burning out. Turn off the boiler. Isolate the unit from
the cold mains. Attach a hose to the draining tap ensuring
that it reaches to a level below the unit (this will ensure an
efficient syphon is set up and the maximum amount of water
is drained from the unit). First open the hot tap closest to the
unit and then open the draining tap.
Warning: water drained off may be very hot!
Important:
After draining the cylinder do not close the hot
tap until the cylinder has fully cooled, failure to follow this
instruction may result in damage to the cylinder and will
invalidate the guarantee.
ANNUAL MAINTENANCE
The unvented cylinder requires an annual service in order
to ensure safe working and optimum performance and to
maintain the guarantee. It is essential that the following
checks are performed by a competent installer on an annual
basis. Commonly this is done at the same time as the annual
boiler service.
1) Twist the cap of the expansion relief valve on the inlet
control set and allow water to flow for 5 seconds. Release
and make sure it reseats correctly. Repeat with the pressure
/ temperature relief valve. In both cases check that the
discharge pipework is carrying the water away adequately. If
not, check for blockages etc. and clear.
Warning: the water discharged may be very hot!
2) Check that any immersion heaters fitted are working
correctly and that they are controlling the water at a
temperature between 55ºC and 65ºC.
3) Check the pressure in the expansion vessel is charged to 3
bar. Turn off the water supply to the unit and open a hot tap
first. The air valve on expansion vessel is a Schrader (car tyre)
type. Air, nitrogen or CO
2
may be used to charge the
expansion vessel.
4) Unscrew the head on the inlet control set and clean the
mesh filter within (some water may escape).
5) The Service Record on page 26 of this manual must be
updated at each service.
Your guarantee may be void without proof of annual
servicing.
SERVICING
