Rocket heater, basement location.....

This concept has probably come up before, but I could not find a previous thread into which it would neatly splice.....if one exists, please feel free to move it  there.

Rocket heater without mass, in an existing basement and "co-ported" with the exhaust of the oil-burning furnace.  In the past, I was interested in adding a wood-burning stove or one of those hybrid oil/wood furnaces, but the exhaust from a standard wood-burner would violate the code for the age of the (unlined?) brick chimney.  But a rocket heater with either direct porting to the chimney or after a few 'turns', at basement floor level, before entering the chimney at the same location as the furnace would be pushing already 'cooled' air into the chimney.  At the same time, I notice that the furnace installer had placed a pressure-triggered baffle in-line with the exhaust pipe before it reaches the chimney brick....is this to mix the furnace exhaust with cooler air before sending it up the stack?  At any rate, it would seem that this would also cool off any too-hot air coming from the Rocket heater.

The objective would be this:  It's an old, drafty farmhouse.  When the furnace turns on, there is good draft into the basement from many points, both outdoor and indoor (there is no 'piped' air coming into the furnace for combustion).  In sub-zero (F) weather, we prefer to have the furnace run a lot because we don't want the water pipes in the basement to freeze.  But if a rocket heater were in the basement, warm air could be generated that not only would warm the basement, it would pre-warm the air being taken into the furnace.  Between this an any warm air rising up through the floor registers from the basement to the main floor (where the thermostat is located), would this not reduce the amount of time the furnace ran (saving fuel), yet keep us from worrying about basement pipes freezing?  Thanks for any responses.

Well if you were to put a RMH into the basement, and have the exhaust leave the house, then you could embed an air intake into the thermal mass that provides your furnace with pre-warmed air. The mass would also radiate heat into the space, keeping it warmer for the pipes. Are there air return registers in the house? You could place the mass near that to warm it up. If there isn't and the furnace is creating positive air pressure in the rooms with the vents, and a negative air pressure in the basement, then I would consider adding an air intake from outside.

So you would build the typical RMH with a thermal mass as a long bench, and 1 pipe exhausting out the air used for combustion. Then a second pipe feeding outside air into the basement, so the mass will heat up that intake air before it reaches the basement, and is drawn in by the furnace. I hope that makes sense? I have no idea if it would help or work, just a suggestion  

The real issue is with the two appliances connected to one chimney, which is against code everywhere as far as I know, and a bad idea. If you could positively ensure that they don't run at the same time, it would be safe (but probably still not to code); that is what happens with combined oil/wood furnaces (my wife's daughter has one).

The draft damper on the furnace exhaust is probably to keep the chimney from pulling too hard on the furnace in case of wind gusts. I believe the oil burner wants its designed amount of air, no more, no less.

Glenn Herbert wrote:   If you could positively ensure that they don't run at the same time, it would be safe (but probably still not to code); that is what happens with combined oil/wood furnaces (my wife's daughter has one).

The draft damper on the furnace exhaust is probably to keep the chimney from pulling too hard on the furnace in case of wind gusts. I believe the oil burner wants its designed amount of air, no more, no less.

Thanks for your responses here.  There are indeed floor registers that allow unimpeded air flow between the main floor and the basement, so some of the warmed air circulates back down there when the furnace fan starts blowing.  Also, yes...Glenn....it does appear that the draft damper modulates wind gusts as it 'flutters' in a windy day.  In case you happen to recall, do you know if your wife's daughter has a Yukon dual-fuel furnace....they are made in northern Minnesota, but recently saw that they were suspended from sales until some kind of UL listing got put back into place....here it is, from their website: "Due to an EPA Regulation that went into effect on all large wood burning furnaces on May 15, 2017, our furnaces will not be available or for sale until we obtain an EPA certification for emissions and obtain review by Underwriter's Laboratories for Safety."   I was interested in those units, but was also thinking about the rocket heater as an alternative.  More food for thought....thanks for the info here!