I have 3 quotes for geo systems.  None of them ran a manual J, and are suggesting sizes based upon my existing AC units, so I just ran my own manual J using HVAC-Calc and got the following results:

1st flr  1243sf,   SC=11,073  TC=15,013    Heat=39,444
2nd flr 1381sf,   SC= 9,495   TC= 11,321   Heat=21,705
Total   2624sf,   SC=20,568  TC=26,334    Heat=61,149

Based on these numbers my current AC units seem to be way oversized at 3 ton up and 2.5ton down.

If I go with geo units, I could go 4 ton down and 2 ton up, and meet most of my heating load, but the Cooling is still way above what I need so I'm concerned about adequate dehumidification as the geo SC is way above the load SC.  Does this look right?

Start with new contractors and get good advice. You need something more along the lines of 3.5-4 tons (total) based on those numbers. What is your foundation (basement, crawl, slab)? Are both units in a common mechanical room?
J

Any chance of zoning a single system?

Based on you heat loss, if accurate, your sizing with a good loop field, you will be able to satisfy the home in the heating mode with no elec heat. The downside is the dehumification ablilities may be limited if you live in a humid climate. 2-stage heat pumps could help in this scenario as well.

If you could zone the home with one 5 ton, that may also be a possibliity. Give us more info, location, type of loopfield considering, ect.

Dan

Where are you located? That can make a difference. Large differences between heating and cooling loads are common and can be a complicating factor in your system design. As has been said go talk to a competent HVAC contractor who will do a real Manual J for you. Room by room differences will impact your design as well as the total load.

If it were my situation I would look hard at using a storage tank for the heating & cooling buffer. That way you can design the heat delivery/extraction part of the system to match the space load and still use a heat pump larger than you need for cooling. That lets the HP run at its most efficient point but still lets the system deliver/extract the heat to match the loss/gain of the living space.

Am located in Maryland.
House has a basement, insulated but not heated and was not included in my numbers. The last contractor wants to use 4 ton up and 4 ton down.
the first floor unit is located in the basement, this ductwork is currently uninsulated, but the basement walls are insulated.
The upstairs unit is located upstairs, insulated ductwork in the attic. It might be possible to zone with one unit, but will have to cut thru a concrete wall and go up 2 floors to the attic.
I am planning on horizontal loop field. My concern is the dehumidification issue caused by the larger unit size required for heating. I definitely will go with 2 stage, which helps this.
I am considering getting the RightJ program and seeing how it compares. Even if I ran the manual J as very leaky, the increase is only 1/2 ton more.
The house is tyvek wrapped, Anderson windows, 3.5" walls with R13 insulation. R30 in ceilings. I entered 4 people load, but did not add any additional for the kitchen.
At least one of the contractors mentioned using my existing boiler as a preheat for the loop water for backup heat.

Ok,
figuring your basement as un heated or heated doesn't change the number much so as long as you put something in there..... you're good. Do not spend any more money on soft ware. Use the time to find a competent contractor with good advice. You want to shoot for about 95% of your requirements (adequate BTU's 95% of the winter) I believe that is going to put you into as little as 3 tons (total) and definately no more than 4. I'm not a fan of 1/2 ton sizes on closed loops as you tend to get less for about the same price.
Solving the problem of your two zones is also best left to a local artisan (he may see something that doesn't occur to us).
Keep looking for a local expert and be cautious not to design the system yourself or have us do it remotely. You want the contractor that you pay to be on the hook for everything...size/design/
performance.
J

I appreciate all the comments. 

Joe, Why only 3 to 4 ton?  I'm starting to think more like 3 ton down and 2 ton up or ducting a single 5 ton unit to best match my heat load. 
I'm talking to another company this week, but with the quotes I've gotten so far, geo is a no deal.  With the prices I'm getting so far,  I'm better off burning $5/gal oil.  My last quote was over $50K for two 4 ton CM tranquility units.

Well I think we've already determined that the folks you've spoken with don't know what they are doing so the prices they gave you don't matter much. You need other looks.
Regarding sizing, again you do not want to try to get 100% of your requirement filled by geo. We shoot for 95% which means that 95 out of 100 heating days you need ___BTU's. Oversizing your equipment costs big bucks on the installation, can be too big for the ducts and often costs about as much to run (due to higher compressor consumption).
I'll again caution you against doing your own design, not only are you already off track, but the contributors here (all good people) are not all hvac pros. All bring their own agenda........mine being "right-sizing equipment and the economy of auxiliary coils" (on this occasion). We will often disagree but to a man or woman, none of us will be responsible for the operation of your equipment.
j

Joe, thanks, I appreciate all the insight you and others bring to this forum.

Yes, your AC units are grossly over sized. BUT, you have to size based upon your largest need which in this case is heating (or expect to use lots of resistance heating which defeats the purpose of geo). Keep in mind that a 3 ton unit provides ~36,000 BTU of cooling at design but provides ~42,000 - 45,000 BTU of heating. Why the difference? Heat from the fan/compressor.

Obviously you need a 2 speed system if you have humidity issues (or you need to install a dehumidifer). Remember to look at the the unit's performance at the design temperatures. Also, there is nothing wrong with going slightly undersized and paying a little bit for resistance heating costs 3-8 times a year.

Every Heat Pump brand that I know of gives less  in heating mode than in cooling.

Which brand have you been looking at?

remember, we never-Never- size for 100% of the heating load. That is the yankees advantage over the south. we can easily make up the last few % of the heating requirements (the few days a year you need it) with the auxiliary coil. This might cost you a few dollars a year but save you thousands in install cost.
Unfortunately our rebel (southern) bretren have to size for 100% of the load in cooling dominated climates.
j

An update on my Geo Journey:
One of the companies I have a quote from invited me to an install job site today.  Very similar sized house to mine, they were installing 4 ton down and 3 ton up.  Installers were very friendly, and the work looked real neat.  They will invite me to another site later when they do the well drilling and grouting.

I've also talked to the local CM distributor, who actually ran their design SW for me and sent me part of the results, which shows expected operating costs and trench lengths.  They did  not include the loop lengths.

Friday I visit with comfort-aire rep.

FWIW....
In northern climate I was told IGSHPA recommendation, for 2 stage systems, to design to Heat load.  Since most units are 1 ton increments, use nearest value without going significantly over.  Cooling will be oversized, but since it's 2 stage will always run on lower stage.  I understand the other view also, since larger size = more cost, and larger CFM, larger ductwork.   One of the brands I'm looking at, the cost delta between 3 ton and 4 ton is $400, wholesale.

The bottom line is Geo is an awesome way to heat and cool.

One 5 ton 2spd installed properly should meet all your heating/cooling requirements and be way easier on the pocket book , 7 tons is grossly oversized

5 tons is oversized. It is seldom good advice to design to 100% of heating load.
J

I'm still debating which units to go with.  Let me review.  My total heat load is 61K btuh.

Upstairs load is 22K btuh.  The 2 ton unit is rated 22.2K btuh at 30* EWT, 2nd stage, so it is slightly over 100%, but is the smallest size they have available.

Downstairs load is 39K btuh.  The 4 ton unit is rated 37.3K btuh at 30* EWT, 2nd stage, so it is  at 95% of load.  If I go with a 3 ton unit for downstairs, rating is 30.3K btuh 2nd stage, or 78% of load.

With the 2 ton + 4 ton = 59.5 btuh   98%
with the 2 ton + 3 ton = 52.5 btuh   86%  I'm leaning towards this 5 ton solution.

If I connect the upstairs duct to the downstairs, which would be a PITA to do, the 5 ton unit is rated 48.1 btuh at 30* EWT, or 78% of both up and down, which is slightly worst than the 2+3 ton units, but a significant unit cost savings for the same loop cost. 

One 4 ton unit only would only support 61% of my  heat load which seems way undersized.

I'll let you know what I decide.

Ok,
Again,
95% of the heat requirement is not a fraction of the heating load, it is the requirement 95 out of 100 winter days(ish). In other words somebody in your neck of the woods might find that a 30K output machine covers 95 out of 100 day's requirements for a 60K peak load. Meanwhile our new friend from Edmunton requires 6 tons to achieve the same 95% with a similar load.
I don't want you to feel that I'm picking on you, but do you suppose your requirements are the same as Edmunton? I think not. It's not your fault that you don't get this it is the people you've invited to bid the job that are the problem.
I already suggested your original estimators were unknowledgeable, tell us what the experts you meet suggest.
By the way 2 ton is not the smallest available unit.
Agin, not trying to sound adversarial, but you came here for good advice.
J

buckeye,
If you really want to get a good idea of how your heating and cooling load varies hourly throughout the day, week, month, & year go to http://mackintosh.aud.ucla.edu/heed/ and download the HEED program. It's free and good, a rare combination! You should be able to obtain and load in climate data for your area. The main aspect of the program is it uses 30 year hourly temperature data to calculate the loads for your house on an hour-by-hour basis. You can change the system capacity and it'll tell you what percentage of time your system will be over or under capacity. It calculates whole house load only, not room by room. Lot of options available for heating systems and building construction.

As Mikey says, "Try it, you'll like it!"