I need advice on running circuit for portable 240 v heater for an
attached greenhouse for freeze protection. The heater is rated at 240
v 4800 watts and manufacturer suggest 30 amp fuse. heater has a 6
foot cord as follows
p136-49 msha 12 awg 3/c 300 V ul and the Plug is a Nema 6-15 or 6-30
250v. I have installed standard 120 volt circuits special items such
as to frig, computer gear, and extensive home a\v system. I have
never installed 240 v circuit.

The 250 amp circuit breaker box has 5 open slots. I will be running
the circuit through 1 2x4 stud and single brick wall. (about 7 ft.)

The wires will be in a ruberized flex metal conduit.

Please suggest wire gage and breakers to use any positive advice would
be welcome.

stan