Most everything you say is true GF if you are trying to achieve the same temps in the different zones. As the demand is for a 20ish degree delta t between them, I don't see the same giant duct disparity that you do. Nor do I see situ's where 1st stage can't handle either zone alone (that's the way I'd set it up). 2nd stage would be for simultaneous calls only, we're looking at a small heat pump here given insulation and demand (if you're not familiar, Morton buildings brag that you can heat them with a candle). Therefore I don't think dumping is automatically indicated. Were I to use a single stage system however, it is a given. I'm never a fan of dumping into returns however as odd pressure situ's could arise (particularly during use of aux. coil). If you have to dump do it into the 50* pole building.
The author's later notes about electric usage suggest we may be overkiling the system any way.
Hopefully we'll have more data to see if geo is even indicated (say a <10 year payback). If that's the case we can save our respective smarts for the next one and agree to disagree here :)
J

agreed , there are allways more then 1 way to get there .Never heard of Mortan

to the author I have learned more from joe then just about any other poster here if you are lucky enough to get him on site Im sure you will end up happy with geo regardless of design

In this unique case I think you are correct - without return dampering it might be difficult to maintain much more than 5 degree diff between zones.

I don't know about your zoning regulations, but a situation involving a garage/storage area, ducted with an apartment would never fly here. Potential for fumes and hazards ,for now or down the road for the usage of that Utility side of that pole barn.

jack,
you are correct in areas governed by the IMC and IRC that there are strict rules about supply or return air to a garage that sharesan appliance with a living space. This is not true of all storage areas or workshops so in a pole building the inspector would generally have to yield to the usage description of the owner (within reason). The easy answer if building is being inspected is to define the apartment area as storage and make other modifications down the road.
J

Sorry, I haven't had a chance to respond to all your postings. Very quickly I will comment that separating the apartment from the building as far as the air returns, is why I thought using automatic dampers on the returns would be the way to go. But from the response I got, it apparently isn't done, or if it is, it doesn't change anything as far as the code is concerned.

Like I said earlier, I had no idea this would be such a challenge. I will supply the requested information as soon as I can. Thanks again for all your responses even though they're not want I want to hear. I am definitely getting an education.

Dampers are not sufficient alone to isolate a garage (or any other space with fumes or otherwise bad air) from a living space.

emj,
The big question is usage.
The thread introduces the pole building without comment as to usage other than the apartment.
If garage usage is intended to the bulk of the building, then I'd say no dice to the code worthiness of a zoned system.
If storage is the thrust of the building then I don't see a conflict.
If your electric rates are resonable, then as I mentioned before, geo may not be the answer at all.
Something like an Amana PTAC, ASHP with aux.(it's like the units in a hotel room) can do a nice job of heating and cooling the apartment for a modest price.
If you haven't poured the floor yet an electric water heater and infloor radiant are one of the many ways to approach the remaining building that has the advantage of no blower (if it is a wood working or paint shop for instance).
Again lots of ways to skin this cat, but if the main building is a "garage" then the codes I enforce as an inspector (2006 IMC and IRC with Michigan amendments) would not allow comingled return air.
J

Sorry I haven't been able to keep up my end of your attempts to help me with this issue. I will try to do better from here on out.

Okay, first of all, the building area will be used mostly for storage. I may do some woodworking in there, but no spraying or other fume-emitting practices and I would be separating my woodworking area from the rest of the building anyway. I also intend to park my vehicle and tractor in there, but will not be working on them inside the building, so the only time they would emit fumes is when I'm moving them in or out. But at those times, the 12' X 12' overhead door would be open, so there would be plenty of ventilation. I really don't see an issue with using one unit for both areas but I'm not an inspector nor a HVAC man. If separate air intakes are used, with automatic dampers not only on the intakes, but also on the output ducting runs, they would be pretty well isolated from each other. I also feel that a unit sized for the apartment would probably be sufficient to heat the building area to 50 degrees. If not, there's always the backup heat which would be similar to what I'm using to heat it now. As for the duct runs, I propose to install the ductwork on the wall of the apartment and place auto-damped vents on both sides of the ducts. When the apartment calls for heat, only the vents going to the apartment would be open. When the building calls for heat, the apartment vents would close and the building vents would open. The same for the air returns.

Having said that, I've also been thinking of an alternative approach to the problem. The only ductwork I would actually need is for the air flow to the apartment in order to heat and cool it evenly. That's standard practice. For heat to the building area, however, I wouldn't really need all that. With the old air handler unit I am using now, I took the A coil out and cut off the lower half of the unit. In the upper half I had left, I cut out another air return and left the resistance heat coils in place at the top. I then constructed a plenum above that with four 6" outlets to which I attached 6" adjustable ells, with manual dampers. I then set the unit up by aiming the ells to different directions and adjusting the dampers for air flow so that the output is around 110 degrees. I have used this unit for the past 4 years and it has worked very well and the building is very evenly heated without running ductwork from one end to the other.

So my question is this: If it's not possible to go with the auto-dampered setup I already described, would it be possible to put in a DX system sized for the apartment, and then install another air handler setup similar to what I described above, with only the A coil in it and circulate the refrigerant through both A coils? When the apartment calls for heat, the blower in the building air handler would not be allowed to run and therefore wouldn't extract any heat needed for the apartment. Only when the apartment is satisfied, would the building blower be allowed to run, during which time the apartment blower would not run.

Again, my thinking is that a DX system sized for the apartment would most likely be large enough to heat the building to 50 degrees if it were only heating the building. By interlocking the two systems, only one would be extracting heat at a time. I do not intend to cool the building. If it's not possible to run the refrigerant through both A coils at the same time, what about installing diverter valves to change the path of the refrigerant depending on which area is being heated?

These may all be dumb ideas, but I thought I'd raise them anyway. Let me know what you think.

Joe, I will get with you as soon as I get a chance. Thanks for your interest.

EarthLinked DX is not capable of having multiple refrigerant coils. If you want more than one air handler from one heat pump, then you'll have to heat and chill water and use hydronic air handlers.