Thermocontrol

[all night moe]

https://www.hearth.com/talk/threads/thermocontrol-vs-traditional-wood-furnace.158207/

Dragging up this old thread for a visual. I have the same furnace only bigger. Tag says rated for 200K BTUs. made in '78.
My current oil furnace is outdated and the duct work sucks. Oil hasn't been fired in close to 20yrs. I wouldn't use it if I could. I am not filling the 1000k gal tank, especially with current oil price hikes.

The automatic damper control on the front door is gone. It is now manual and the furnace is run like a wood stove. 24''x24''x4' deep firebox devours wood. Air plenum around the furnace reaches 160* and the fan limit switch cycles the fan untill temps drop to 100*. I know I can adjust the limit switch and I did last year. I dropped the cut off down to 100 from 120* in effort to keep blowing heat a little longer. I'm wondering if I could switch from natural draft to a forced fan air intake.

As is, it's a constant short cycle action. The house never warms up, save the closet ducts to the furnace. Partially due to the residual heat lofting through the floor from the furnace.

 

[brenndatomu]

. I'm wondering if I could switch from natural draft to a forced fan air intake.

Don't do it...if you think it uses a lot of wood now, wait until you turn the forced draft on!

As is, it's a constant short cycle action.

Can you slow the blower down? Is it belt, or direct drive?
Can you close all the registers some, or close some duct dampers off some to raise the static pressure on the system? That will make the blower run more and increase heat to the house greatly...BTDT! You could also put a higher MERV filter in...that will slow the air down some too...

 

[all night moe]

Don't do it...if you think it uses a lot of wood now, wait until you turn the forced draft on!

Can you slow the blower down? Is it belt, or direct drive?
Can you close all the registers some, or close some duct dampers off some to raise the static pressure on the system? That will make the blower run more and increase heat to the house greatly...BTDT! You could also put a higher MERV filter in...that will slow the air down some too...

It is a direct drive. I bought the new parts to replace the natural draft auto controls. I was just thinking if it was forced draft it would fire up and run hotter, and longer when the thermostat called for heat. When idling it would smolder and not consume the wood. Just like the natural draft is supposed to work, only this would end the short cycling.

It consumes wood like any other furnace either way. I'm looking for heat. Furnace is in the front of house. Aproximately 60ish feet away from the living room. Uninsulated duct work in a crawl space for the first addition. Did I mention I detest forced air?

 

[brenndatomu]

I was just thinking if it was forced draft it would fire up and run hotter, and longer when the thermostat called for heat

Yeah, it sounds great...but in the real world it doesn't pan out very well...I've had several forced draft units and I quit using the draft blower...ran it like a big whole house stove...and everybody I know that has a forced draft wood furnace does the same...can't think of one person that has a forced draft wood furnace that likes it.
Part of the problem is that you have to close the intake flapper on the draft blower a lil more if using it, than if you are not using it (to keep flue and supply temps in check) so then what happens is the fire is starved for air when the blower shuts off....just smokes and smolders until the next call for heat (filling the HX and chimney with creosote) and as a bonus, sometimes it will back puff and fill your house with smoke...so much fun...not!

Uninsulated duct work in a crawl space for the first addition. Did I mention I detest forced air?

Nothing wrong with forced air...its just like anything else, it has to be installed properly...you are losing a ton of heat to the ground if there is no insulation on the duct or crawlspace! Its no different than someone cheeping out and using poorly insulated underground line on an OWB...not gonna heat the house well...not the OWB fault, it was not installed properly.
The cheapest thing you could do to increase your heat is insulate that ductwork.

 

[all night moe]

The cheapest thing you could do to increase your heat is insulate that ductwork.

All understood.
Insulating the duct work is far to much trouble than it's worth. Literally I would have to slide around on my belly. Crawl space is just a phrase here for most of the space. Then to go through all that just to have rodents nest there way in there looking for a warm place.
Some of the ducting actually dead ends due to the remodeling.

I don't see how the auto-damper natural draft could keep the plenum hot enough, long enough, to keep the limit switch in the active rang.
Guess I'll find out next season.

 

[all night moe]

Updates.....
Using the same forced air wood furnace this season. I learned more about it. The bypass damper was inoperable and it was actually laying on the firebox floor, beneath the secondary burn chamber. This chamber is a vertical box at the back of the primary fire box. I fixed this at the end last years season. I'm burning less wood this year. Score for one step in the right direction.

I've studied the ductwork closely, as of late. FUBAR is a polite way to describe how this wood furnace, was connected to the existing ductwork. The wood furnace has 2 cold air returns. One from the house and one near the oil furnace blower. I'm not sure if the blower side is a positive charge or a "natural" air flow. It looks to be before the blower. The supply from the wood furnace is almost the same size of the plenum on the oil furnace. It is way to large.

If I use this furnace next season, I will fix these issues.
1. Eliminate wood furnace returns.
2. Down size the supply to a 8x10'' feed into the top of the oil furnace plenum.
3. Install a sealed divider below the supply feed in the plenum, and supply air to the wood furnace below the divider with more ducting.
4. There is an additional 6'' supply duct of the top of the wood furnace surround, with a blower and aquastat, ducted into the supply duct, a few feet downstream of the oil furnace. The blower does not work. I will be eliminating this.
If I'm correct, this should put a positive charge into the wood furnace surround, and out the supply into the house ducting.

If I reach my fall goal this year, an OWB, I'll seal off the holes made from the wood furnace ducting, and install a 22x22'' water to air HE in the oil furnace plenum. At some point, while remodeling this 183yr old house, I will eliminate the ducting and convert the 1st floor to radiant floor heat. I do not have access for 2nd floor radiant floor heat. My plan there is to run 1'' lines, from the OWB 1 1/4'' supply lines, up into the attic. Loop this around the perimeter with 3/4'' drop legs into each room. 2nd floor rooms will get cast iron rads. I grew up with these and love their efficient performance. It is almost a toss up for me to use them downstairs as well.

My journey with an OWB will be a separate future thread in this forum.