Draft Regulator on Newmac oil/wood combination furnace

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scotify

New Member
Nov 9, 2021
2
Southern Ontario
Hi all, new member and new wood burner here đź‘‹Threads on this site have been really helpful so far!

I recently moved into a rural property and inherited the wood/oil combination furnace heating system. I've figured out that the model is the CL86/96C and the manual is actually available online from here: https://newmacfurnaces.com/multi-fuel

So far, since it's not been that cold during fall, I've been just using the oil side occasionally (which was inspected and signed off on by a gas furnace tech). Just the other day the chimney sweep came out and cleaned and inspected the wood side so I've burned a couple of fires in it. Now that I've used it, I just have more questions! I'm going to limit myself to just a couple for now:

1. The firebricks in the firebox look really rough. I brought it up the cracks to the chimney sweep and he said it's not a big deal as long as they aren't chipping and crumbling. Only after he left, I realized the ones at the back kind of are crumbling. Can I easily replace these myself? As long as it's the same size, is any firebrick material acceptable? I attached pics of before and after, I happened to take a picture of the firebox just after moving in, before I had Iit any fires in it.

(side question - is this level of soot build-up on the bricks normal after 2-3 fires? Should I be cleaning it off?)

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2. I was reading up on oil/wood furnaces and found this article which contains this statement:

"If you mostly use the oil furnace and then switch to using wood, many homeowners forget to check their air damper on the chimney"

Check it for what? The Newmac manual makes constant references to a 'draft regulator' or 'barometric damper' on the flue and says things like:
"Do not set the flue draft above -- .05” W.C."

It's not clear to me what this means. The chimney sweep who inspected it never mentioned anything about flue draft or damper. I went behind the furnace to look at it and it's basically just a hole in the side of the flue pipe with a very loose, flapping piece of metal. Sometimes I hear it 'dinging' as it swings in the wind, on windy days. I attached a pic. I can't see any obvious way to "adjust" it and I'm not sure what W.C means anyway. Is it supposed to be like this? Should I be doing something to it before burning wood? The manual says to "close it" in the case of a chimney fire but I don't understand how I would do that.
I'm wondering if the way it's set up right now could be contributing to less effective burning, since I don't seem to be getting much heat from the amount of fuel I'm putting in it, and I'm getting some smoke out the chimney. I'm keeping the draft fan on practically all the time and burning seasoned hardwood, measured at <20% moisture.

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Thanks in advance - and sorry for the ton of questions at once, I'm a total beginner here and really want to make sure I'm being safe!
 

sleewok

New Member
Jan 27, 2021
48
USA
Hey! Welcome!

Definitely replace the crumbling bricks. Get a measurement from ones that are still intact. I would replace the cracked ones as well . You just swap them out.

Soot on the bricks is nothing to worry about. Just keep the ash under control.

You have a barometric damper connected to the flue. If you flip it open you'll see a weight of some sort attached near the top side of the damper. You adjust the draft by shifting the position of the weight (it unscrews). This changes the balance of the damper which will swing open (this reducing the pressure in the flue) when draft exceeds the setting for the damper. AFAIK The only way to calibrate it property is with a manometer to test the pressure in the flue. You can get cheap ones on Amazon.

The manual is referring to a manual damper on the furnace that should be closed...

The type of wood and how you stack it can impact heat level significantly.

Also, from the manual :

COMBUSTION AIR CONTROL The amount of combustion air allowed to enter into the firebox can be controlled by means of the Draft Control slide on the draft fan mounting plate. Set this slide plate to the position that allows sufficient combustion air in for the type of solid fuel being burned. Normally the setting is in the center between maximum and minimum, then if additional control is needed it can be adjusted accordingly. When burning coal it must be set at maximum, for burning wood it will vary with size and type. DO NOT LET THE COALS/ASHES BUILD UP ANY HIGHER THAN HALF WAY UP THE FIRE BOX LINER.
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,301
NE Ohio
If those are "standard" bricks, you can buy those at the stove shop or hardware pretty easily...if not, then just FYI, you can fix the cracked ones (one or two "tight fitting" cracks) by glueing them back together with furnace cement...it works really well...obviously the ones that are completly exploded, or pieces are missing, those will need replaced...if you have any that are custom cut to fit, then you can cut the new ones easily with a $15-20 diamond blade on an angle grinder.
The new bricks will be broke soon too if you just "chuck" wood in and bounce it off the back of the firebox...place the wood in and they will last a long time.
 
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scotify

New Member
Nov 9, 2021
2
Southern Ontario
Thanks all, I replaced the 4 back bricks that were cracked the worst and cleaned up the firebox with the shop vac, there was a lot of ash all over and looks much cleaner now. Just left the recommended 2-3" layer of ash at the bottom to light the fire on.

Question - after I put the new bricks there are pretty big gaps between them (see pic, mostly on the right there).
I double checked and the bricks I pulled out are exactly the same size as the ones I put in, and same as listed in the parts manual. I think the reason is that before, there were thick layers of ash built up between them.
Is it ok to burn like this or should I try to seal/close the gaps somehow?
Thanks again

PXL_20211120_003415567.jpg
 

sleewok

New Member
Jan 27, 2021
48
USA
Thanks all, I replaced the 4 back bricks that were cracked the worst and cleaned up the firebox with the shop vac, there was a lot of ash all over and looks much cleaner now. Just left the recommended 2-3" layer of ash at the bottom to light the fire on.

Question - after I put the new bricks there are pretty big gaps between them (see pic, mostly on the right there).
I double checked and the bricks I pulled out are exactly the same size as the ones I put in, and same as listed in the parts manual. I think the reason is that before, there were thick layers of ash built up between them.
Is it ok to burn like this or should I try to seal/close the gaps somehow?
Thanks again

View attachment 285890

You're ready to burn. Get some wood <20% moisture and fire it up!