What does this symbol mean: "-//-" ?

This symbol represents the ‘siphon fill mode’ and is most commonly seen when the boiler is first switched on or if it has been shut down for a long period.

The symbol will flash alternatively with the temperature on the LED display.

The symbol does not represent a fault with the boiler.

When is the ‘siphon fill mode’ activated?

The siphon fill mode is activated by one of the following:

• the electrical isolation switch is turned on
• if the boiler has not activated for 48 hours
• occasionally if the condense trap or pipe is blocked
  or
• will activate when the boiler is put into heating mode (if this is a combination boiler), or central heating and hot water mode (if this is a conventional or system boiler)

More information about the condense trap

If the condense pipe has become blocked then the most common symptom of this is a gurgling sound coming from the boiler. If this is the case then you should consult your Gas Safe Registered installer.

What happens when the siphon fill mode appears?

The boiler will run in minimum mode (around 50°C) for around 15 minutes. This can sometimes take longer if the boiler has been oversized and cannot keep the flow temperature low enough.

Once the boiler has gone through this cycle it will then return to its normal mode.

What if the symbol stays on the boiler for more than 2 hours?

If the boiler has remained in this mode for more than a couple of hours then you should either contact our Technical Support department on 0844 892 3366 or contact your Gas Safe Registered Installer.

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