The enclosure sourced for the original design was made in the UK and so had a long lead time. An alternative enclosure with the same dimensions, but lower price and shorter lead time was found from Hammond Manufacturing
A hole for the conduit connector was drilled in the side.
The enclosure we purchase shipped with a gasket intended to be adhered to the lid of the enclosure (shown in the first picture on this page).
Testing revealed that this gasket failed to keep out water, so we constructed a new gasket of SBR rubber.
After the first heated test, the enclosure was allowed to sit underwater overnight to see if any water would get in. A very small amount of water entered the enclosure, and the source of this leak was a wire clamped across the gasket/enclosure interface.
Extra precautions were taken to ensure this did not happen again, and no more water was detected in the enclosure after any other heated test.