Radiation Enclosure convergence issues in THERM7.6

[John]

I am attempting to use a radiation enclosure in THERM7.6.1.0.

Are radiation enclosures supported in THERM7.6?  If so, is there a document which provides the detailed process for modeling them?  

I referenced the forum post, "Radiation enclosure in chimney simulation" for guidance on how to model the enclosure and how to set up the associated boundary conditions.  However, I have not been able to get a simulation to converge, even with a very basic geometry (refer to attached Test0_R1.THM). I get the following error message: "Solution failed to converge.  Try changing relaxation parameter or decrease convergence tolerance in ConRad."  I am limited in my capacity to change these settings, as I need to abide by the NFRC Simulation Manual as closely as possible (refer to attached THERMSimSettings_R1.jpg).

Ultimately, I hope to model a radiation enclosure with two radiation boundaries, as I need to simulate the combined effect of a radiant heating panel (120 deg. F) and the environment (75 deg. F) on a window sill's condensation performance. (refer to attached Test1_R1.THM)

Thanks,

John