I was asked this morning if there is an issue with adding a woodburner to a geo system. The definitive answer is....it depends.
A free standing stove or fireplace insert; no problem.
A paralell ducted, wood furnace with it's own blower; not my favorite, but okay.
A wood boiler with hydronic fan coil; be very careful......
With wood boilers, many are franchised to folks that are other than heating professionals and they sell oft times to do-it-yourselfers. The most common situations we see, when we follow this chain of inexperience, is restriction. Restriction is not a friend to refrigeration.  Not only do they often have a one size fits all approach to the hydronic fan coil market, but it is often a small and modestly restrictive device that occasionally cycles gas appliances on limit.
An undersized hydronic coil on a geo system would be extremely unfortunate and could cost the user more money than they save. Remember geo is the least expensive system to begin with so the prize would be feeding a wood burner all month to save maybe $200. A restriction in the ductwork could cost the homeowner efficiency of their heat pump, in so doing it could derate the btu capacity and tax a very expensive variable speed motor costing hundreds/yr in maintenance and energy usage.

The Question for the experts here today is: would you advise customers against a wood boiler with a package 2 stage heat pump or...what would the criteria be that didn't void your warranties (i.e. static pressure)?
 
Yep, I said void warranties. If you jam a crappy hydronic coil in my return and run that heat pump with a restriction, or heat air upstream of a heat pump without a priority lock out, you would definately run the risk of losing your warranty protection with us.
The main thing is always...always get with your (geo) installer before putting anything in your duct system or modifying your heat pump's operation.

Joe,

Not to take away from your org. question but what would be a good way to help spread the heat of a wood stove/pellet stove thought the house? Second set of return duct the pull hot air from above the stove?

Thanks,

I'm actually glad you asked.
In areas that I inspect (MI) there are 2 rules pertaining to return air around a solid fuel appliance (or other gas appliances).
The first is a 10' rule (return air openings not to be within 10' of appliance).
The second is that it can't be a central return in the same room (it must be one of many not the only return air opening for that furnace).
The rule seems to sensibly try to preclude back drafting (or sucking smoke back down the chimney) and circulating it around your home.
Neither rule applies if the appliance is direct vent which means it draws it's combustion air from outside and is sealed to the room it is housed in (many pellet burners are like this as are many gas fireplaces).
Thanks for bringing it up g.
Joe

I'd change the air filter and then gather ESP and fan power data for all modes of operation - zones / stages as applicable. A properly specified and installed hydronic coil might still be able to keep the blower within limits. I know that a couple WF models (3 and 4 ton, I think) allow selection of a higher static 1 HP ECM blower. Bumps the ESP spec from 0.50 to 0.75. That might suffice in some circumstances.

Data in hand, I 'd lay it on the line for the HO. Blower power is gonna rise, and if the blower's ESP rating is exceeded, then all warranties as to efficiency, capacity and durability are out the window.

I'd push for the insert / freestanding option and assist with 'out of the box' ways to better distribute heat from the stove / insert - alternatives such as floor grates, short ducts connecting rooms, perhaps with small thermostatically controlled fans or blowers.

I acquired a couple decades of supplemental wood heat experience before I came to my senses and moved to FL. In Pennsylvania I stretched a single tank of heating oil out over 3 winters by fanatical use of a freestanding wood stove.

Wood heats you seven times: While you fell it, buck it, split it, carry it, stack it, carry it again...and finally when you burn it.

You forgot number eight- when you have to clean up after it.

Maybe it's just me, but the one place I don't scrimp is on my heating or cooling. I figure I work hard so that I can be comfortable when I get home. The last thing I care to do is haul logs around to make this happen (I actually removed a woodburner from my home when I bought it). It's not that I don't understand folks who do want to save a buck, or those that find splitting wood relaxing. It just isn't my thing.
....or maybe it's because the more extreme the weather, the more money I make, the less I worry about an extra hundred on the heating or cooling bill....
j

Folks factor solid fuel burners as cost of the burnables only when comparing operating cost. Has anyone come up with a fair way to evaluate actual cost of that heat (time and energy consumed to feed and clean the beast). It seems like we ought to be able to assign an honest cost to solid fuel heating to better compare operating costs.
Perhaps those of you using pellet or woodburners could offer btu's achieved, fuel costs and hours consumed rounding up fuel or maintaining appliance. If we use that and a fair laborer's wage then we ought to be able to ball park a price/btu.
J