Horne Engineering Ltd

FAULT FINDING CHART

POSSIBLE CAUSE

ACTION

REFER

SYMPTOM

TO

SECTION

Mixed water

Temperature setting too high.

R e-adjust temperature setting

4

temperature too high

Temperature has been set when the hot

water temperature is too low

Hot water has migrated into cold water

Inspect Check Valve at cold inlet

3.6.1 to

supply

If the check valve leaks replace

3.6.6 See

the strainer body and check valve

Drg.6355

sub-assembly

Thermostat Element has failed. This

Replace element (6)

6

can be checked by carrying out a hot or

cold water failure test.

Mixed water

Temperature Setting too low

R e-adjust temperature setting

4

temperature too low

Hot water supply temperature has fallen

Check hot water supply system

3.2

Cold water has migrated into hot supply

Inspect Check Valve at hot inlet If

3.6.1 to

the check valve leaks replace the

3.6.6See

strainer body and check valve

Drg 6355

sub- assembly.

Cold valve face requires cleaning

Remove valve Cover (3) and

6.4.7

servic e valve face

Mixed water flow rate

Partly blocked strainers

Clean strainers

6.2

too low.

Unusually high pressure drop in supply

Check all valves are full open.

pipework

Check Pressurisation unit Check

mains supply

Extra Demand added to system

Check pipe sizing

Mixed water temp

Slide-Valve (7) is seized

Valve requires de-scaling

6.4.5

does not respond to

adjusting screw

Hot and cold inlets reversed

Remove HORNE 20 TMV from

pipes and reverse connections.

Connect inlet with red dot to hot

pipe

Mixed water temp

Slide-Valve (7) is seized

Valve requires De-Scaling

6.4.5

changes and is not

Thermostat element has failed (This

Replace element (6)

6

steady

can be checked by carrying out a hot or

cold water failure test)

Hot and cold inlets are reversed

Hot inlet is marked with Red dot

Water at outlet runs

Cold inlet is marked with Blue dot

f ull hot or full cold

Valve continues to

Cold valve face requires cleaning

Remove valve cover (3) and

6.4.7

pass cold water

serv ice cold valve face

when hot supply is

Fouling at hot valve seat

Clean hot valve face

6.4.7

isolated

Valve continues to

Slide-Valve seal is damaged

Replace Slide-Valve Seal (10)

6.3.4 &

pass hot water when

6.3.5

cold supply is

Element has failed

Replace Element (6)

6

isolated

July 2004

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