F7 may be caused by a faulty float level switch on any Hurlcon Astralpool Viron gas pool heater. This is an OEM replacement float switch rated for higher temperatures than generic parts. These can be very difficult to remove when corrosion is present. 

Part 78140, number 53 in diagram.

Notes:

• Heater base must be checked for corrosion or other issues. This is best done using an borescope.
• If condensate tank is corroded, replacing the float switch will not resolve issue. Heater will likely need replacing.
• OEM part. To be fitted by qualifed persons only.