UL certificate for heat exchangers

Hi,

One of my customers is building units, to be exported to US.
We deliver components who have a UL certificate. For the condensor (air cooled) he uses a coil comming from an other supplier with copper tubes with a thickness of 0,28 mm; the MWP is (according to the coil supplier) 33 bar.
Now the UL inspector says that to get an UL certificate, a minimum wall thickness of 0,65 bar is required.
Does anyone know if this is correct? Is there a minimal wall thickness requirement in UL? (Or is it a pressure test requirement ...)

Best regards

Bescie, this is not a real answer to your question but perhaps this can help http://www.ul.com/hvacr/refrigeration/categories.html

I personally think that they only can demand for a pressure test whatever the thickness may be of the copper.