A Phase Fuse Clip
hydrogen boiler infrared thermal imaging hydrogen boiler visible light
Infrared Thermal Image Visible Light Image
This A phase fuse clip is showing a lot more heat than either the B or the C phase. This is usually an indicator that the fuse clip has lost the spring tension to properly hold the fuse.
The spring starts starts to soften and lose that tension at approx. 200 degrees. This fuse clip should be replaced.