outdoor to gravity conversion

Betz

I have an old gravity converted hot water system that I added an outdoor wood burner to. I'm still having problems with my indoor water going to the outdoor boiler and cooling off the water too much. The cold water makes the burner call for heat, and I go through a lot of wood. The manufacturer is telling me that a heat exchanger will make it worse but I'm thinking that if I don't directly mix the two systems together there won't be as much cooling of the water. My heat loss calculates to about 110,000 btu at 0 degrees. Even if I miscalculated it by 50% I should have plenty of hot water to heat with. My outside burner holds 400 gallon of water and I'm not sure how much water I have inside the house. I guess my question is: if I use a large heat exchanger and separate the two systems, so my burner isn't directly plumbed to the inside, will I lose all the heat so fast from the burner? I'm getting so confused now I'm not even sure what I'm asking anymore. I've had a boiler professional look at the system and I can't get anyone who can really answer any questions. There has to be someone who knows what to do here...Thanks for any help you can be.