My house is 3000sq. log 14"diam.  lots of windows & open loft.  HVAC contractor installed a 3 ton unit. said it would be big enough for this house.  We have a ground loop system. It runs most of the time with not much heat production. Would a 4 ton unit heat and cool  this house right. In theory without knowing the heat loss factor. or do I need a larger unit.  What do you think of the climatemaster units

Before you can tell what size heat pump is needed, you need to know the heat loss of the structure. If you don't know the heat loss, you can only guess. If the heat pump is not keeping the house warm, then either the heat pump is the wrong size or not working properly.

There is no way to know with the little bit of info you have given us.

Climate Master makes good units.

What is the coldest outside temp in your area?

Is your heat pump one or two stage compressor?

Live near Dayton, Oh  it gets 10-20 outside. single stage unit. was a 3phase converted to a single phase compressor. I would say our heat loss is avg.

heat loss is given in terms of BTU/h,  not average or more or less.  

A heat loss report looks like this:

Once we have a heat loss number, then we can tell you if your heat pump is undersized, but not until.

Log homes are always higher heating loads. They have a higher infiltration rate. Just based on the fact that you have a log home and the square footage, I can't imagine that a 3 ton unit would be large enough. However, geodean is exactly right. We have to start with an accurate load calclulation.