Here we have an obvious loose conenction on the B Phase
hydrogen boiler infrared thermal imaging hydrogen boiler visible light
Infrared Thermal Image Visible Light Image
Here we have an obvious loose connection on the B Phase.
 
This will not heal itself. It will only incraese in heat until this problem is resolved or it gets hot enough to melt down.
 
This connection should be pulled and cleaned then reinstalled making sure that all wire connections are clean and tight.