Hi, I bought a Lennox heat pump last summer - it is an add on to an existing oil furnace. Since purchasing I have had nothing but porblems. The service techs have been back at least 8 times. The majority of the problems occur when I switch between heating and cooling. The heating now seems ot work fine, but whenever I switch to cooling, cool air blows for a few minutes, then the pipes going to the inside of the furnace accumulate significant frost and the cool air doesn't blow. Before getting the service people hear yet again - does anyone have any suggestions. Thanks in advance. P.S. I have replaced my furnace filter, and shut the breaker off/then on again to reset the system.