FAULT FINDING

72 L.......A

(OVERHEAT ERROR)

Can the overheat condition be reset by pressing the boiler reset button when the system is cold ?

YES

Is the boiler and CH system filled with water and all isolation valves open ?

YES

Does the pump setting give a differential across the boiler in excess of 25 oC ?

YES

Increase the pump setting.

Is differential now below 25 oC ?

 

 

 

NO

 

 

 

YES

 

 

 

 

 

 

 

 

 

 

 

Replace the system pump

 

 

OK

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NO

Replace overheat thermostat

 

NO

Fill and vent the system and open all

 

 

isolation valves

NO

Set CH control knob to maximum.

If the overheat trips again measure the flow temp:

Over 90 oC Check control thermistor (Refer to Frame 71) .

Under 90 oC Replace overheat 'stat

Note.

With V9 Primary Control PCB, overheat LA/HA or H9/L9 when reset will display 3 horizontal lines and will not attempt to refire until the temperature in the heat exchanger drops below 50oC.

73 L....8..... (FAN ERROR)

Is nominal 330 V DC present across

YES

Is 14V DC present

YES

 

across yellow and pink

red and blue at the fan connector as

 

 

 

at the fan connector?

 

reset button is pressed?

 

 

 

 

 

NO

 

NO

 

 

YES

 

 

 

 

Check wiring harness for continuity. Is there continuity?

 

 

 

NO

 

Replace fan

Replace PCB

Replace harness

FAULT FINDING FAULT FINDING FAULT FINDING

74 H.....1

(FLOW THERMISTOR ERROR)

Remove the boiler flow thermistor from the CH flow

pipe and disconnect thermistor wires.

Check resistance, using a suitable multimeter connected across the thermistors terminal pins

At 25 oC

expect

9,700

- 10,300

Ohms

At 60 oC

expect

2,400

-

2,600

Ohms

At 85 oC

expect

1,000

-

1,100

Ohms

FINDING FAULT FINDING

Are the thermistor values correct ?

NO

Replace the thermistor

YES

YES

 

Is there continuity between the

 

PCB and the thermistor ?

NO

 

Replace PCB

Check and replace wiring as necessary

FAULT

icos - Installation & Servicing

47

Page 47
Image 47
IDEAL INDUSTRIES HE15, HE24, HE18 72 L.......A, Overheat Error, 73 L....8..... FAN Error, 74 H.....1, Flow Thermistor Error

HE12, HE15, HE18, HE24 specifications

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