Temperature clamps on a plate HEX

[Matt0029]

If using temperature clamps on a plate HEX. To diagnose if it's blocked. Are you ment to have a large DT. As the plate is transferring heat when it's unblocked?

 

[John.g]

Attached are numbers from someone who posted them after renewing the PHEX on a WB 36CDI, the boiler was tripping on a high primary HEX temperature I think. The numbers in yellow were taken from the boiler data itself, the other numbers are my calcs.

 

[ShaunCorbs]

The return back to the burner and the hot water outlet should be no more than 5dc apart