Faults

TacoTherm Dual ZEPTO

11.2

Fault repair

Fault description

Cause

Remedy

Personnel

No hot water at the

taps.

Ball valves are closed.

Open the ball valves.

Operator

Primary energy supply is

not reliable.

Check whether there is hot water at the

heat exchanger. If there is no hot water

at the heat exchanger, check the central

heating.

Operator

Heat exchanger is defec-

tive.

Replace the heat exchanger (

Ä Chapter

11.3 ‘Replacing the heat exchanger’

on page 54).

Heating and

sanitary techni-

cian

Primary circulation pump

defective.

Replace the primary circulation pump

(

Ä Chapter 11.4 ‘Replacing the pump’

on page 54).

Heating and

sanitary techni-

cian

Backflow preventer defec-

tive.

Replace the backflow preventer

(

Ä Chapter 11.5 ‘Replacing the backflow

preventer’ on page 55).

Heating and

sanitary techni-

cian

Controller defective or

power supply discon-

nected.

Check the power supply (

Ä Chapter 1.2

‘Other applicable documents’ on page 8).

Electrician

Insufficient hot

water at peak times.

Temperature sensor or

flow rate sensor defective.

Replace the temperature sensor or flow

rate sensor (

Ä Chapter 11.7 ‘Replacing

the temperature sensor’ on page 57,

Ä Chapter 11.6 ‘Replacing the flow rate

sensor’ on page 56).

Heating and

sanitary techni-

cian

Black water at the

taps.

Heat exchanger is defec-

tive or cold water supply is

contaminated.

Replace the heat exchanger (

Ä Chapter

11.3 ‘Replacing the heat exchanger’

on page 54).

Check the water quality.

Heating and

sanitary techni-

cian

Insufficient water

pressure at the taps.

Calcified water tap at the

taps.

Unscrew the water tap and decalcify.

Operator

Calcified pipes in the heat

interface unit or in the

entire pipe system.

Check the water quality and, if neces-

sary, take appropriate measures to

comply with country-specific regulations

regarding water quality.

Heating and

sanitary techni-

cian

Safety valve blows

off.

Pressure or temperature

on DCW/DHW or secondary

heating are too high.

Check the temperature or pressure and,

if necessary, regulate it.

Heating and

sanitary techni-

cian

Safety valve defective.

Check the network pressure and, if

necessary, replace the safety valve.

Heating and

sanitary techni-

cian

No heat transfer

despite open control

valve and demand

by the controller.

Dirty heat exchanger due

to incorrect flushing and

unclean heating water.

Flushing or replacing the heat

exchanger.

Heating and

sanitary techni-

cian

V03 06/2025 Item no. 215250 EA no. 1292

Operating instructions

53