First of all, Hello to all, finally i've found a place where i am likely to get specific guidance.

Hi, I'm no refrigeration engineer, but its a subject which is of much interest.

I am planning on converting my split ac unit (1.5 ton) (indoor and outdoor unit) to a heat pump?

I am planning on using the existing outdoor unit, replacing the condenser part with a large condenser coil buried underground and hope that this will increase the cooling capacity so that i can attach more indoor cooling units to this single compressor unit. Will this increase the cooling capacity (if so give any advice on the condenser coil size etc) or am i just going to waste my money. The work is to be carried out by an unqualified but experienced refrigeration engineer.
If i am going to suggest anything I need to know myself. I.ve got the above idea from reading about heatpumps with condenser pipes buried underground.

Urgent help is needed as I am starting work tomorrow!