Central Heating Repair
This article is about Central Heating systems using hot water as a heat-carrying medium. (Warm-air systems are sometimes found in the UK but their design and installation is not covered here. There is a discussion on updating existing warm-air systems here)
The article is about diagnosing and fixing a faulty central heating system.
There are separate articles about:
- Central Heating Design which will help you understand what sort of system you have
- Central Heating Operation for help operating a working CH system.
This article is a skeleton: the main points to be covered are listed but some or all still need to be expanded
Fault-finding
- No CH or DHW
- boiler working? - boiler fault-finding guide (Ed?)
- No CH, DHW OK
- conventional
- programmer, room stat or zone valve prob
- combi
- programmer or room stat, (diverter stucK?)
- conventional
- CH OK, no DHW
- conventional
- programmer, cylinder stat or zone valve prob
- combi
- diverter valve if PHE design, flow switch or scaling if combined heat exchanger
- conventional
- DHW OK, some parts of CH not working
- rad(s) compeletely cold
- balancing - try turning off other rads
- stuck TRV - take head off pull up pin (carefully - can pull out and leak on some)
- completely full of air - bleed & find cause
- rad(s) lukewarm
- balancing
- faulty TRV
- rad(s) cold at top
- bleeding
- rad(s) cold at bottom
- sludge
- rad(s) compeletely cold
- CH on when should be off
- All rads on
- timer? room stat? zone valve?
- Some rads on
- reverse circulation
- rad on DHW circuit - often in bathroom: may be design "feature"
- All rads on
rads constantly need bleeding
- air or hydrogen in system? (lighter test - with care!)
- corrosion:
- inhibitor?
- vented system? - pumping over?
- air
- pinhole leaks?
- vented system? - pumping over?
- corrosion: