Horne Engineering Ltd

FAULT FINDING CHART

REFER TO

SYMPTOM

POSSIBLE CAUSE

ACTION

SECTION

Temperature setting too

Re-adjust temperature setting

high. Temperature has

4

been set when hot water

with hot water supply at correct

temperature.

supply temperature was too

low

Inspect Check Valve (16) at

cold inlet. If the check valve

Hot water supply has

See Drg. 9309

leaks replace the pipe coupling

Mixed water

migrated into cold water

(15) and check valve

temperature too

supply

subassembly.

high

Thermostat Element has

Replace Thermostat

failed. This can be checked

6.2.1 ­ 6.2.2

Element/Slidevalve

by carrying out a hot or cold

assembly (5)

water failure test.

Remove Valve Cover (9) and

Hot valve face requires

internals and clean Hot Valve

6.3.7

cleaning

Face.

Temperature Setting too

Re-adjust temperature setting

4

low

Feel hot water supply pipe near

Hot water supply

to valve with outlet running.

3.2

temperature has fallen.

Check hot water supply system.

Mixed water

temperature too

Inspect Check Valve (16) at hot

Cold water has migrated

low

inlet. If the check valve leaks

See Drg 9309

into hot supply

replace the pipe coupling (15)

and check valve subassembly.

Cold valve face requires

Remove valve Cover (9) and

6.3.7

cleaning

clean up valve face

Partly blocked strainers

Clean strainers

-

Check all valves are full open.

Unusually high pressure

Mixed water flow

Check Pressurisation unit.

-

drop in supply pipework

rate too low.

Check mains supply

Extra Demand added to

Check pipe sizing

-

system

Thermostat Element/Slide-

Valve assembly (5) is

Valve requires de-scaling.

6.3.5

seized

Mixed water temp

does not respond

Remove HEATSTAT T2 TMV

to adjusting screw

from pipes and reverse

Hot and cold inlets reversed

-

connections. Connect inlet with

red dot to hot pipe

Thermostat Element/Slide-

Valve assembly (5) is

Valve requires De-Scaling

6.3.5

seized

Mixed water temp

Thermostat element has

changes and is not

failed. (This can be

steady

Replace Thermostat Element

6.2

checked by carrying out a

/Sidevalve assembly (5)

hot or cold water failure

test)

Water at outlet

Correct the inlet connections.

Hot and cold inlets are

runs full hot or full

Hot inlet is marked Red.

3.1

reversed

cold

Cold inlet is marked Blue.

Valve continues to

Cold valve face requires

Remove valve cover (9) and

pass cold water

6.3.7

cleaning

service cold valve face

when hot supply is

isolated

Valve continues to

Fouling at hot valve seat

Clean hot valve face

6.3.7

Issue 3 Dec 05

Page 9 of 10