Heating with a wood burner - converting to Boiler of sorts - need help

Looking for some guidance on an idea I have rolled around in my head for 6 years. I want to heat water with my big wood burner. 

Some background: The house is a 70s era build with a single story plus 3/4 basement. The wood stove is a Fischer unit, and its the larger of the three Fischers, and it is located on the main floor. The house layout is circular in build, so a fan near the wood burner pushing air down the hallway, and cold air back into the burner room does a pretty excellent job keeping the entire house warm when I'm running the stove. The issue is the basement. In the Covid era, SWMBO is working from home, so we built her a nice 12x25 office in the basement. The basement is heated with the central heat/air, which is all electric (5 coils @ 20AMPS ea). Problem is, when its cold enough outside to burn the stove, (it needs to be under 30* outside or it just gets too hot upstairs), then the basement gets frigid. 55* is not uncommon when its 20* out and we've been burning for a day or more. We have tried running the furnace fan only to help circulate the air, and while that does help, it's still to cold for SWMBO. This last months electric bill was $480, and the bill breaks down the heat usage to over $350 of that. $350 for 4 months is flat out unacceptable. It's also noteworthy that I get wood absolutely free from the family farm, which has an endless supply, as pops gets his retirement exercise splitting wood and selling it on the side. 

To summarize: When its cold enough to burn, my basement gets cold. I want to somehow transfer the wood burner heat to a coil in the air handler so I can heat the entire house with it, not just the 1st floor. 

My 1st thought was a simple coil in the furnace, after the A-Coil for the A/C, that I could install and remove easily each season, this way it doesn't hamper A/C performance in the summer. I would use a standard boiler circ pump (5-10GPM) to push water from that coil to the wood burner, where it would somehow scavenge the heat, and plumb it back to the coil. I would need to have a pressure regulator with a water supply to keep the system under a static pressure, and a pop-off that would prevent over-pressurizing. I am on well, so water is essentially free, and while I would be running my A/H fan and a pump 100% of the time, thats still 1/40th of the energy my heat draws on any given day. 

ok, enough background. on to the questions:

1. Whats the best way to steal the heat from my wood burner? The pic below isn't my actual burner, but it is damn close. I thought about replacing a section of stove pipe with a heat exchanger designed for this exact thing, but have had no luck finding anything. Plus, as I have this chimney swept every other year, I don't want to make that process harder.

2. What water flow speed would you all recommend? Is floor board/floor heater circulating speed correct, (5-10 GPM) or is that to slow?

3. I am happy to spend $500 on this, because if it works correctly I can save that in two months. I could probably even sell $750 to SWMBO, assuming someone on here supports this idea in a way that would ease her concerns of safety and effectiveness.

4. Am I crazy? This is kind of important...

5. How do i manage internal pressure? 20PSI regulator in, fed from house water (filtered, of course), 30PSI regulator out to sump drain?

6. What exchanger coil? There is plenty of them for sale, but I'm not sure of the characteristics I should look for...

Let me know what you guys think. This is the basics of what I was thinking:

simple copper coil around flue pipe?

I watched a video a while back about a wood fired pool heater.  They initially ran the coils inside the fire box, but as I recall they became suited up and he thought it would be more efficient to run the new ones in the outside. 

Here’s the link: https://youtu.be/wPRIWStGjGE

i don’t know if there is helpful info there for your project.

we had the same problem growing up, near the stove awesome and warm, upstairs away from the stove, freezing!

I have nothing really to add but to say Fisher stoves are spectacular, mine will easily make my house 90 degrees.

I'd probably go more for fans pushing air around rather than water myself, less moving parts

Run a duct near the ceiling above the stove, run it through the floor down into the floor of the basement. Get a duct fan to pull the hot air near the ceiling  down to the floor of the basement,  if you really want you can hide the duct work in the wall cavities. 
     Her feet will still be cold. So put an  electric heat mat under the desk. 

If you did this I would probably look at a non-pressurized system.  Yes this limits temperature to 212F, but it also prevents violent expansion.  You could basically heat a tank of water sitting on the stove.  Otherwise a typical heat exchanger design is multiple loops of u bent small diameter pipe that you ciculate water through.  

If you proceed to make a boiler please follow boiler Pressure Vessel codes/standards for piping, joints, and such.  

Coils on the flue can cause issues with lowering flue temperature.  This may be ok but you want to keep it hot enough to avoid buildup of creosote.  

Are there any wood burning boilers you could model it after?  

A few points. You'll NEED a way to control pressure down to almost nothing for safety, easiest being to use an open system circulating hot water. Investigate boiler water treatment, as even at boiling temperatures, regular water can be corrosive. You'll also need to consider potential scale buildup issues. You'll want to get a sample of your water analyzed to help answer that. Depending on your water, you might need to run distilled water to control scale buildup.

Easiest solution is probably to duct some warm air from right by the fireplace down to the basement, or put a space heater in that office space.

Mom and dad's house uses a tempering tank beside the stove.  It's basically a big 40-ish gallon aluminum tank.  Its far enough away that it can't boil, but it works well enough that they sometimes have to flush a couple toilets or run some water before they shower because the water is too hot even on full cold in the morning.  Theirs is set up as a pre-heater for the water heater, but water conducts heat so well that it more or less heats all the water in the pipes.

No pressure worries, no boiling worries, no maintenance worries.

The only problem I see with your diagram is that your system has no choice but to be the only means of keeping the water temps below 212 degrees.  I think it will constantly be opening the pressure valve and just dumping gallons of water in the sump.  Otherwise you will have to rig a thermostat to kick on the HVAC fan if the water gets too hot, so instead of heat on demand, you'll have heat when the WATER needs it, not when the air needs it.  It won't matter if its 95 degrees in the house, you have a fire in a box with water about to boil, it's gonna either have to turn on the heat or things will explode.  I also think your water circ pump would have to run 24/7 as long as there is a fire.

And I agree... never take heat from the flue.  Cooling the vent will likely cause rapid buildup of creosote which can become a chimney fire very quickly.

In your diagram, you're taking heat from air, putting it in water, transporting the water, then putting the heat back into the air.  I think the easier solution is to just move the air.  How about a selectable air return?  Put an air door in the HVAC return so you can choose the normal return in the summer and a duct above/near the stove in the winter?

My thoughts: