Gas Furnace upgrade with inline wood stove.

[chiraldude]

I have an old Lennox Pulse furnace and am thinking about upgrading. The thing is still working but seems to be an energy hog. Gas efficiency is fine but I notice that the blower uses a lot of electricity. Measuring current draw of the motor I calculate about 900 watts from the blower motor alone. I am hoping that a newer furnace with a variable speed blower would be able to reduce this a lot.
Also, I have a wood "furnace" that is ducted inline with the gas furnace. What I have read is that the the lower speeds of a variable blower are only useful if the duct work has a fairly low resistance to flow. Any truth to that?
If this not so much of an issue, I could have the blower motor replaced with a new variable speed motor instead of replacing the entire furnace.

As for the wood furnace, is it possible to configure the ductwork so that it is not inline? Put an additional blower on the wood furnace and have it blow air into a plenum shared with the gas furnace? I could add a couple of extra ducts for it on the first floor but no easy way to add ducts to the second floor. (both heat sources are in the basement)

[HVAC_Marc]

There was a variable speed pulse a long time ago. your duct system needs to be properly designed for low velocity applications, yes, for a variable (or any other system) to work properly.

I dont know about adding a VS blower to a furnace. There's lots of wiring and board changes. Probably not worth it.

If you dont have the wood inline, after the furnace, you will need a damper/baffle to close off the return of the furnace when you are not using it. And then switch that to the wood heater when you are not using that one. It prevents the heat from going where it doesnt belong