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Knowledge Hub

Ground source heat pump support

Here you’ll find some information on potential NIBE ground source heat pump problems, along with some tips on how to diagnose and repair them.

NIBE 1145-1245 alarm troubleshooting

TL/TB alarm 52

This occurs when the built-in immersion increases flow temp too high (usually after legionella purge). It has to be manually reset. To do this, turn the heat pump off, remove the cover and push the reset button using the smallest electrical screw driver available in hole FD1-SF2. More information can be found on page 17 of the NIBE 1145 installation manual.

If this is recurring, it could be a flow issue. If towel rails are fitted on a DHW primary coil, ensure signal wire to the DHW zone valve is taken from terminal 11 on 1145 PCB as per A14 docking drawings (page 3 of 4), and not terminal 7 as it was on old drawings.

Motor protection alarm/Phase fault

Possible unsteady voltage has been supplied to the unit, meaning the motor protection trips to protect the compressor. It has to be manually reset by removing the front cover and locating rotary switch FB1. More information can be found on page 17 of the NIBE 1145 installation manual. The switch should be in the horizontal position.

HP Alarm

This could be high pressure in the refrigerant, caused by poor flow on the waterside of heat exchanger in the heat pump so it overheats.

Things to check include: dirty inline filter on return to heat pump, air in system (check silver air scrubber), and are all valves fully open?

No heating or hot water – no alarm logged

Compressor symbol (blue piston symbol) showing on menu 3.1 and on page 19/24. If hot gas, liquid line and suction gas temps are all room temperature then it is possible this is a soft start failure.

Ground loops/LP alarms

0 bar pressure in ground loops is OK as long as Glycol is present in the vessel. It’s best to be running at 1 bar in summer, this will drop though in winter as brine cools.

If there is no pressure and no Glycol, it could be a leak – most probably on a connection in the manifold pit. An installer can investigate this issue.

LP alarms are common with leaks and occur due to low pressure in the refrigerant due to poor flow on the brine side of the heat exchanger, effectively cooling it right down.

Things to check as well as leaks: check inline strainer on ground loops is clean and check all valves are fully open, brine pump running so brine in/out temps have 3-5°C differential.

Need more help to resolve a NIBE ground source heat pump problem? You can contact our Technical Support Team via techsupport@nu-heat.co.uk or give them a call on 01404 540745 between 8am and 5pm, Monday to Friday.



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