OBSERVATION INTERNAL BY-PASS

Set Appliance State:

CH Demand

Position temperature probe to center of plate heat exchanger
Ensure plate heat exchanger is cool, this is achieved by turning the gas off
& running boiler with DHW demand

WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure

Mains Power On

Observation:

If required, reset boiler, Press Mode and Ok simultaneously.
Allow boiler to run for central heating.

vm vitodens 25 kw combi dis ch flow temp ignited .jpg

Compare the boiler flow temperature (display) and temperature of the plate heat exchanger.
Is the plate heat exchanger temperature cooler than the flow temperature or is plate heat exchanger temperature approximately the same or greater than the flow temperature, signifying the auto bypass is passing or open.