I’ve been reading the forum on and off for a couple of years and very thankful for all the helpful information that has been posted by everyone. I’ve been getting a great education!

I have a few estimates for a geothermal system and would like some advice/input to help make the best decision. I am using the forum’s shopper’s checklist before making any final decisions. This is preliminary so far. Sorry in advance for the long post.

We are in a suburb of Baltimore, MD. The house is 4,100 square feet, contemporary with lots and lots of glass. It’s 33 years old, but the windows are tight, ceiling insulation R-30, walls R-19 plus 1” styrofoam. The house is on a wooded lot and gets a ton of shade on all sides during the summer – about 5 hours direct sunlight daily.

2 years ago I did a manual J using HVAC-Calc residential 4.0.
Total Heat Gain – 77,745
Total Heat Loss – 74,626
Outdoor Summer temperature – 89
Outdoor Winter temperature – 17
Indoor Summer temp – 75
Indoor Winter temp – 67

Replacing 2 oil furnaces, along with a 4 ton and 2.5 ton ac units.

We have a problem with one section of the house that takes forever to heat/cool adequately. This section is on top of an unheated garage. The garage ceiling has 6” of fiberglass insulation. There are 3 rooms fed by one 8x8 main supply duct. The floor registers are fed by 6” round ducts. There are returns in all the rooms.

Estimate 1 – 4 ton and 3 ton Waterfurnace Envision, 3 bores, 380 feet deep, with 1-1/4 inch diameter pipe. 2 inch pipe run from bores to home. Use existing 2 zone system ductwork. Aux heat included kw not specified

Estimate 2 – The sales rep offered 2 WF options for me to choose from –
Option 1: 4 ton and 3 ton with the same vertical well specs in estimate 1. 10 kw aux heat each unit

Option 2: 6 ton with 3- 320’ wells - 1-1/4 pipe. Both systems tie into the house using 1-1/4” pipe. Use existing 2 zone ductwork – with dampers adapted to one unit. 15 kw aux heat

Estimate 3- 6 ton WF - 3- 320’ wells. Pipe size not indicated 4 zone system using existing ductwork 20 kw aux heat

I got a separate estimate for the well drilling and loop installation from the well driller used by 2 of the companies. According to him this area has good rock that is 20-40 feet below the surface. I am also getting other estimates for the HVAC portion of the job. Loop estimate specs 3 – 320’ wells with 1” pipe 1¼” pipe tie into house

Some questions:
Will a 6 ton unit handle the heating load without relying too much on aux heating?
Is 1” or 1-1/4” pipe more efficient for the wells?
How much difference does the size of the tie in pipe make? 2” versus 1-1/4”
If a 4 zoned system is designed properly can it correct the problem we’re having in the one section of the house?

Thanks for taking the time to read all this.