This morning I knew it was gonna be warm and I sent the wife a text saying we will be under a "low draft watch" today.. Knowing she didn't have work I didn't prepare the furnace for a low draft condition. Well she went out shopping for a few hours and when she came home she sent me a message saying that the low temp alarm (set for 130) for the flue pipe was beeping (on my handy remote BBQ thermometer
). I immediately told her to go into the basement and look at the mano and sure enough, it was below 0 and the basement reeked of sulfur. SO, I had her hit the override switch for the draft inducer and took it up to a .03" WC. So no harm, no foul
My normal procedure for a warm day trying to idle the fire back is too -
1. Cut primary air to a sliver to keep a low and slow fire..
2. Open the MPD. (I usually leave it open unless its really cold and the baro can't keep my draft down to a .03"WC)
3. Open my secondary (over the fire air valve) to 50 - 100% depending on conditions outside.
*I've found that when I cut the primary air and give it more secondary it maintains draft. The secondary air doesn't aid much with combustion when running a low fire, but instead is just more heated air mass that goes up the chimney and keeps the draft. I've also added vents on two sides of the basement. These vents compensate for any (if any) stack effect going on in the basement from warm air going up thru the floor. The vents more or less keep atmospheric pressure between outside and the basement balanced since any negative pressure in the basement would cannablize draft pressure.
I'd like to hear what my other fellow coal burners do to keep a chimney draft under warm day outside conditions