unvented hot water cylinders
installation and maintenance instructions
Page 11 / 17
FAULT POSSIBLE CAUSE SOLUTION
Water escaping from the case unit
Compression fitting on hot – draw off not sealing Check/remake joint sealing paste
Cold water at hot taps
Direct – immersion heater not switched on or cutout
has triggered
Check / reset
Indirect – boiler not working
Check boiler – consult boiler manufactures’
instructions
Indirect – motorized valve fault Check plumbing / wiring motorized valve
Indirect – cutout 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 3bar
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 3bar
if necessary. If bladder perished replace vessel
Unit it being back pressurized
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
Water discharges from temperature
& pressure relief valve
Unit has overheated – thermal controls have failed
Switched off power to boiler and immersion heaters.
Leave water supply on. Wait until discharges stops.
Isolate water supply and replace if faulty.
Milky / cloudy water
Oxygenated water
Water from any pressurized system will release oxygen
bubbles when flowing. The bubbles will settle out.
No hot water flow
Cold main off Check and open stopcock
Stainer blocked in pressure reducing valve Isolate water supply and clean
Inlet control set may be fitted incorrectly Check and refit required
Noise during hot water draw off –
typically worse in the morning
Loose airing cupboard pipework Install extra clips
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
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