Vaillant [F.532] fault codewhat it means and how to fix it

F.532 is the heat pump refusing to run because not enough water is moving through it, and the first thing to establish is which heat pump you have, because the code belongs to one generation. It is in the fault table of the earlier aroTHERM monobloc — the VWL 55/2 to 155/2 A range, and the /3 that followed it — where the installation instructions list it as "Building circuit: Flow rate too low" with the causes heating circuit not fully purged, dirt filter in the heating circuit return missing or blocked, water deficiency, pressure loss in the heating circuit too high, pump cabling defective and pump faulty, and even warn during commissioning that improper purging may cause pump faults due to a low flow rate (F.532). It is not in the fault table of the aroTHERM split or the aroTHERM plus.

On those, the same condition is a status code, S.275 "Building circuit: Flow rate too low", which holds the compressor off without a fault, and the faults you would see instead are F.788 or F.820 on the pump. Vaillant UK’s owner page lists F.532 without saying which range, and treats it differently from most of their codes. For the majority of faults that page says "this is a case for a Vaillant engineer".

For F.532 it says: this is a case for a Vaillant installer in the first instance, as it can relate to how the heat pump is working with the heating system — and they add that while they will attend any fault code, they reserve the right to charge a call-out fee for non-product faults. That is Vaillant telling you the problem is usually in your pipework rather than in their machine. Their published causes bear that out: system water pressure below the normal 1 to 1.5 bar, a blockage or restriction in the building circuit, insufficient flow rate around it, a blocked or restricted filter or Y strainer, a circuit that is incorrectly balanced or a bypass that is incorrectly adjusted, and air or debris. The everyday version of all this is a house where every radiator valve has been turned down, or a zone valve has shut, and the heat pump — which needs a lot of water moving at a small temperature difference — has nowhere to send it. A boiler would have shrugged and run hotter. A heat pump stops and shows F.532.

1. 1

   Read the system pressure. Vaillant give 1 to 1.5 bar as the normal range and low pressure as the first cause; if it is below 1 bar, F.22 is the page to read, and it sets out who Vaillant say may top it up.

2. 2

   Open the thermostatic valves on a few radiators and check no zone has been switched off entirely. A heat pump needs an open path for its water even when rooms are warm enough.

3. 3

   Think about recent work. Anything done to radiators, the cylinder or the pipework in the past few weeks will have let air in, and air is on Vaillant’s list.

4. 4

   Ask your installer when the filter was last cleaned, and book them rather than Vaillant. Vaillant say so themselves for this code, and warn of a call-out charge for faults that turn out to be in the system.

   Cleaning the filter means isolating and opening the primary circuit, and on many heat pumps that circuit contains glycol. Ask for it to be done rather than doing it.