We are currently building a greenhouse, and I need to run about 240 foot of wire from the pole to the greenhouse breaker box. The greenhouse will have 2- 115/230V fans drawing 6.0 amps each, 3- 1/3hp sump pumps not sure of the amperage yet but will be 115v, LP gas instant hot water heater, 10 heater coils. Heater coils are 115v but the motors do not say how many amps they draw, just that they draw less than two amps each. So my question is, what size wire do I need to buy for this project? Mainly just the service wire from the main box and meter to the new box in the greenhouse. Also I would like to run this service underground. Thanks for the help,
Randy

As a close minimum,#1 aluminum XLPE cable just exceeds the max of 3% voltage drop for a feeder , 240 feet, and assuming 80 amps of load. If your load would not exceed 50 amps, then #1 is fine.

However sounds like you may want to expand later, so I would like to suggest you use #4/0 URD cable, it is very popular and a good investment, and eliminate Vd till the load gets to 150 amps

If money is no object, then go the next size down, but bury the copper immediately as it is very popular with thieves.

For such a long run, through farm or rural setting,
Use 4" PVC DB conduit,
use handholes every 75-100 feet as pull points, and at direction changes,
use Sch40 PVC for exposed conduit,
use Sch40 in urban areas, and Sch80 in drive or truck roadways.

If it may be needed, lay a separate spare conduit, the largest you can afford, no less then 2".

Rural, bury 24 " deep , use a bed of sand 6" top and bottom in rocky soils
Heavy urban, go 36".
Lay warning tape over the entire length 12 " below grade.

Hope this helps.

Thanks for the help!