Horne Engineering Ltd

FAULT FINDING CHART

SYMPTOM

POSSIBLE CAUSE

ACTION

Mixed water temperature too

Temperature setting too high.

Re-adjust temperature setting

high

Temperature has been set when the hot water

temperature is too low

Hot water has migrated into cold water supply

Inspect Check Valve at cold inlet

If the check valve leaks replace the strainer

body and check valve sub-assembly

Thermostat Element has failed this can be checked

Replace element (8)

by carrying out a hot or cold water failure test.

Mixed water temperature too

Temperature Setting too low

Re-adjust temperature setting

low

Hot water supply temperature has fallen

Check hot water supply system

Cold water has migrated into hot supply

Inspect Check Valve at hot inlet

If the check valve leaks replace the strainer

body and check valve sub-assembly.

Cold valve face requires cleaning

Remove valve Cover (5) and service valve face

Mixed water flow rate too

Partly blocked strainers

Clean strainers

low.

Unusually high pressure drop in supply pipework

Check all valves are full open.

Check Pressurisation unit

Check mains supply

Extra Demand added to system

Check pipe sizing

Mixed water temp does not

Slide-Valve (9) is seized

Valve requires de-scaling

respond to adjusting screw

Hot and cold inlets reversed

Remove HORNE 15 TMV from pipes and

reverse connections.

Connect inlet with red dot to hot pipe

Mixed water temp changes

Slide-Valve (9) is seized

Valve required De-Scaling

and is not steady

Thermostat element has failed (This can be checked

Replace elements (8)

by carrying out a hot or cold water failure test)

Water at outlet runs full hot or

Hot and cold inlets are reversed

Hot inlet is marked with Red dot

full cold

Cold inlet is marked with Blue dot

Valve continues to pass cold

Cold valve face requires cleaning

Remove valve cover (5) and service cold valve

water when hot supply is

face

isolated

Fouling at hot valve seat

Clean hot valve face

Valve continues to

pass hot water when

cold supply is isolated

Slide-Valve seal is damaged

Replace Slide-Valve Seal (13)

Element has failed

Replace Element (8)

Issue 3 8/05

9