Jotul old F 118 vs New F 118 CB

[blacksheep1998]

I have an old (1976) Jotul F 118. I was able to find the owners manual online. After converting all the measurements from MM to inches, it looks like for CTC the manual states 31.49 inches. Looking at the manual for the new F 118 Black Bear, the required clearance from the back to combustibles is only 9 inches.

What is the difference between the 2? Looking at the manuals for both, I don't see any additional plates in the firebox area that would account for this reduction in clearance. Now the top of the 2 units are diferent as the new one has the extra air inlet and baffles to meet EPA regs.

Anyone have any insight to this?

Thanks,
Pete

 

[BrotherBart]

The Black Bear now includes side and rear exterior heat shields that probably weren't supplied with the earlier models. Look at the parts list in the manual for the CB model.

 

[blacksheep1998]

Right it does include them, Page 12 / 13 of the new manual has all the diagrams.

According to the new manual stove with NO heat shields single wall pipe 35" side, 9" rear, 26" corner. With the heat shields on back and side the clearances are reduced to side 18", rear 4" corner 12" again with single wall pipe.

And this is where I am at a loss to figure out why with no extra heat shields on the interior, or exterior installed the clearance is so much less.

Thanks,
Pete

 

[Corie]

The old stove had nothing in the rear of the fireplace but a wear-plate. The new stove has the secondary combustion and flash fire package installed at the back, which I assume is acting as a heat shield within the firebox which prevents the back wall of the stove from getting nearly as hot.

Basically, the clearances on the new stove can't be used on the old stove; the exterior looks the same, but the similarities end at that.

 

[wg_bent]

The old stove had nothing in the rear of the fireplace but a wear-plate. The new stove has the secondary combustion and flash fire package installed at the back, which I assume is acting as a heat shield within the firebox which prevents the back wall of the stove from getting nearly as hot.

Basically, the clearances on the new stove can't be used on the old stove; the exterior looks the same, but the similarities end at that.

so if the back wall, and side walls don't get as hot, yet the stove retains the same BTU output (an assumption on my part), where does the heat come out of the stove. Only the top? Doesn't that make the top awfully hot?

I mean, the heat's gotta go somewhere.

 

[blacksheep1998]

Here's an interesting bit of Info:

New 118:
# Maximum heat output: 55,000 BTU/hr
# Heating capacity: Up to 1,600 Sq.ft
# Overall efficiency: 73%

Old 118: (From Jotul resource book, Nov 5, 1974)
# Maximum heat output: 44,500 BTU/hr when burning 11 pounds per hour
# Overall efficiency: 76% burning 3.1 pound per hour (22,500 BTU/hr)

So why should one buy a new unit, with slightly more heat output, and less efficiency

 

[begreen]

The older Jotuls were good heaters. Used correctly with dry wood, they burned quite cleanly. Be sure to keep it in good shape and watch for any warps or cracks with the interior plates. The plates should seat tightly against each other. I added a thick steel back plate to the interior rear of our 602. It made a very noticeable difference in the rear heat. This is a weak point of the older 602 and the plate solved the problem.

 

[blacksheep1998]

Yeah I already have all new gaskets on order for the stove before I fire it up. Still trying to figure out what kind of protection to put on the walls no responses yet to my other thread tho :-(

I also wonder if I fabricate a rear heat shield will that allow me to move it closer to the wall. I am sure I could make some kind of standoffs and use a piece of sheet steel to make a heat shield.

Pete

 

[begreen]

Yes, there are options for non-combustible standoffs. Our 602 had durrock with ceramic spacers and a metal skin, but in retrospect the durrock firring strips is simpler.

I believe that 12" is the closest you will be able to get with a shield, regardless of insulation. So I would keep it simple. Will the stove have double or single wall pipe? If single wall, it will need a heat shield all the way up. However, this can attach to the pipe if you don't want to extend the wall shield all the way above the stove.


This thread might be of help:

https://www.hearth.com/talk/threads/7159/
or
https://www.hearth.com/talk/threads/6654/

 

[blacksheep1998]

Thanks for the link, yeah the same debate seems to be going on there too, as to ways around code, or interpetation of the code.

I just want the easiest way to reduce clearance possible, that does not look like garbage. 50% reduction will be 15.75", and 66% reduction will be 10.71" The difference between the 2 is not very much. So I am open to either of the options offered by code. Just not sure what 1" of glass fiber is. Is that fiber glass insulation, or is it Micor or Fiberfrax? And if that is the case why would the code specify 1/2 insulation board, then 1" of another insulation board?

I guess the real problem is all the contractors around here don't know squat. One guy does only chimneys, the other only sells stoves (or $400 stove boards) the inspectors office has not returned any calls.........

Pete