Why reefers are different
Insulated walls and the machinery end shorten and narrow the floor. SeaCube lists a 20 ft reefer at 5,454 × 2,294 mm inside, against Leman's 5,898 × 2,352 mm for a 20 ft dry container. CN lists its 53 ft refrigerated domestic container at 50 ft 1 in × 97 in, against 52 ft 4 in × 98 in for its high cube.
What that does to euro pallets
Width is what matters for the EPAL 1: at 2,294 mm or 2,280 mm, two 1200 mm sides do not fit across, and three 800 mm sides need 2,400 mm. So reefers usually run the mixed pattern of one across lengthwise and one crosswise. See the per-container tables linked above for the computed counts.
Air flow
Reefers need air to circulate through the load. Floor counts here are geometric and do not reserve space for air channels; follow the carrier's loading guidance.
Pallet choice
New EPAL pallets are chamber-dried to a maximum of 22% residual moisture under EPAL's classification. For moisture-sensitive cargo, ask for new or confirm the condition of used pallets.