Fire Chief FC1500 install

[Mrpelletburner]

What temp is the lower limit switch set at to activate the blower , could this be adjusted to kick on earlier before heat is lost to the flu????

I believe it is ~100 degrees and yes it can be adjusted. Distribution blower is running nonstop.

Trying not to change anything to avoid voiding the warranty.

 

[Medic21]

? How's that? You wire up a timer or something?

Just cycling with the thermostat.

 

[Medic21]

I believe it is ~100 degrees and yes it can be adjusted. Distribution blower is running nonstop.

Trying not to change anything to avoid voiding the warranty.

Mine is on at 150 off at 90. It was set at off 110 and it really extended how long it will produce heat by lowering it.

 

[woodey]

Would adjusting lower limit switch to kick in at a lower temp help by putting more heat to the house and less lost to the flu.

 

[brenndatomu]

Just cycling with the thermostat.

Ah, I think I see what you are doing...I thought about that in the past...some nice outside the box thinking there!

 

[Medic21]

Would adjusting lower limit switch to kick in at a lower temp help by putting more heat to the house and less lost to the flu.

That’s a tricky situation. Cool it off too much early it will lower flue temps and effect creosote buildup. I have to burn for a good 30 min on a cold stove to get it to even kick in. About a hour in it runs on/off about 50% and 1/2 way it will run continuously until the thermostat for the draft motor kicks off.

 

[Case1030]

I should of added this to my last post. My probe is about 6" from the back of my furnace. I'm not sure if that is why I'm seeing a little higher temps than the other guys. My draft speeds are always pretty low when temps are above 20F ( my chimney isn't very tall ) so I generally have to keep a small nail or a paper clip on the front flap to keep the secondaries going which doesn't help either.

How tall is your chimney. I only have a 16ft and find I have to keep a bent grounded down nail any weather above 14f. My flue sits around 350f but low alarm will kick in at 275f in cold weather.

 

[Mrpelletburner]

I would say your return air temp is pretty typical for anyone that does not have return air duct hooked up...just pulling off the floor basically. That plenum temp is not impressive.
Last winter I tried out a Kuuma VF200...when the flue temps were 450*F, the supply duct temp was 200*+!

Yes, I need to draw in that warm air from the basement ceiling. Was thinking of making a box attachment made from fire resistant rigid insulation.

 

[maple1]

Yes, I need to draw in that warm air from the basement ceiling. Was thinking of making a box attachment made from fire resistant rigid insulation.

Not sure how much that will gain you, overall. If it raises plenum temps, it will also raise flue temps. Which are already sky high, BTW - yikes.

Another way of looking at it - you are seeing a 47° rise (dT) through the furnace. What are other furnace users seeing? Chime in, folks.

 

[Medic21]

Not sure how much that will gain you, overall. If it raises plenum temps, it will also raise flue temps. Which are already sky high, BTW - yikes.

Another way of looking at it - you are seeing a 47° rise (dT) through the furnace. What are other furnace users seeing? Chime in, folks.

When everything is warmed up 70 degree airbin and 140-150 out.

 

[maple1]

Another factor is distribution blower speed. And how much that might be varying from setup to setup.

All else being equal, if you move more air, you will lower the dT - but overall heat output would be the same. So dT isn't the only factor here. Which makes it kind of hard to directly compare between setups.

Seems pretty evident the stack temps here are way too high though.

 

[sloeffle]

How tall is your chimney. I only have a 16ft and find I have to keep a bent grounded down nail any weather above 14f. My flue sits around 350f but low alarm will kick in at 275f in cold weather.

It is either 20 or 24 feet. I can't remember if it is 5 or 6 sticks of SS double wall pipe.

24 feet seems more realistic though just from doing some basic measurements in my head.

 

[JRHAWK9]

Another factor is distribution blower speed. And how much that might be varying from setup to setup.

All else being equal, if you move more air, you will lower the dT - but overall heat output would be the same. So dT isn't the only factor here. Which makes it kind of hard to directly compare between setups.

Seems pretty evident the stack temps here are way too high though.

I was just going to mention this, as it's very hard to compare plenum temps between two completely different setups. Too many different factors at play. Not just speed, but volume and duct pressures as well.

Another way of looking at it - you are seeing a 47° rise (dT) through the furnace. What are other furnace users seeing? Chime in, folks.

△T of 47° is very good, IMO. My 75K BTU LP furnace, for comparison's sake, using the -low- speed tap on the blower motor sees a max △T of 48°. Using the medium-low speed tap that drops the △T to 42°. The acceptable △T range for my LP furnace is 35° - 65°. It was originally setup using the medium-high speed tap but I changed that last year because the △T using that faster tap resulted in a △T of only 35°. My HVAC buddy told me to put the △T in the middle of the acceptable range to balance the longevity of HX vs efficiency.

To me this furnace seems to act more like a cleaner burning version of the old school inefficient ones. Consuming lots of wood (if you want to keep a fire going), great heat output, short burn times and high stack temps.

 

[sloeffle]

Last winter I tried out a Kuuma VF200...when the flue temps were 450*F, the supply duct temp was 200*+!

Brenndatomu's Skunk Works ????

 

[maple1]

I was just going to mention this, as it's very hard to compare plenum temps between two completely different setups. Too many different factors at play. Not just speed, but volume and duct pressures as well.



△T of 47° is very good, IMO. My 75K BTU LP furnace, for comparison's sake, using the -low- speed tap on the blower motor sees a max △T of 48°. Using the medium-low speed tap that drops the △T to 42°. The acceptable △T range for my LP furnace is 35° - 65°. It was originally setup using the medium-high speed tap but I changed that last year because the △T using that faster tap resulted in a △T of only 35°. My HVAC buddy told me to put the △T in the middle of the acceptable range to balance the longevity of HX vs efficiency.

To me this furnace seems to act more like a cleaner burning version of the old school inefficient ones. Consuming lots of wood (if you want to keep a fire going), great heat output, short burn times and high stack temps.

But - your LP furnace dTs, I suspect, are achieved with MUCH lower flue temps?

So - we have here a burner that burns and makes heat (fairly uncontrollably, it seems) way faster than it can exchange it. Can't slow the burn, can't up the exchange.

Double-whammied.

If the burn could satisfactorily be slowed, and warmer return air supplied, we would likely have an improved situation. But warming the return air would actually lead to less exchange (maybe insignificant, not sure).

Huh, a slinky commercial just popped into my head....

 

[brenndatomu]

Brenndatomu's Skunk Works ????

https://hearth.com/talk/threads/uh-oh-whats-this.172989/

 

[JRHAWK9]

So - we have here a burner that burns and makes heat (fairly uncontrollably, it seems) way faster than it can exchange it. Can't slow the burn, can't up the exchange.

yep, what i was getting at when I mentioned inefficient comparing it to the old school ones. It's making heat too fast and almost impossible for it to exchange it.

Not sure how much that will gain you, overall. If it raises plenum temps, it will also raise flue temps.

I agree, as the larger the △T the more efficient the heat transfer should be as more heat should be stripped.

however....... (o boy, this may get long winded....again. )
My wood furnace warm/cold air supply setup is definitely NOT a conventional setup. All I know though is that it heats this sieve of a house pretty damn well now and -MUCH- better than it did with the out-of-the-box conventional setup I had originally. In fact some of what I have done to achieve better results may actually go against conventional methods/thoughts/practices and may not even make sense as to how I'm seeing the results I'm seeing and may not even work for others. I'm seeing them though, so that's all that matters.

Here's a prime example. When I first installed the furnace I did it according to standard procedure. Using an open staircase, I was taking the cold air directly off the cold concrete basement floor and heating it, using the low speed blower tap. Simple snap switch on/off blower. With the furnace on low I was seeing a △T of ~30° IIRC. Taking in 65° - 68° basement floor air and sending out ~95 - 100° supply air. I found out soon after installation I pretty much had no duct static pressure so that didn't help, as I was moving high volumes of air so fast through the air jacket it may not have had "time" to extract maximum heat. I was sending out high volumes of 95° air. The very first fall of burning I was pretty much burning 24/7 already and temps really were not all that cold yet. The furnace vitals were always fine, it was burning great, going on pilot for extended periods, good stack temps, great burn times, etc. I chalked it up to the house being that bad....which I knew it was seeing we averaged ~1,300 gallons of LP a year over a span of 5 or 6 years.

Fast forward to today.

I have been, for the past few years now, taking the warmer air off the basement ceiling AND also mixing some of the reclaimed hot radiant heat off the face of the Kuuma before it gets heated. In essence I'm taking in 80°-85° "cold air" and sending it through to be heated. I would probably see even lower stack temps if I was sending through cooler 70° basement "cold air", but it would not heat the house better. The warmer "cold air" directly resulted in warmer supply temps.

I also have my blower speed controlled and slowed WAY down. The slower the blower, the warmer the supply temps are once again. I have dramatically reduced the volume of air being passed through the air jacket and into the house, but dramatically increased the temp of it. I'm sending it maybe 70V when in the middle of a burn with the computer on low....it's cutting out at around 98° when the blower is only receiving 45V or so. My △T now, with the computer on low is still ~ 30°. Taking in 80°-85° air and sending it out 115°-118°. I have yet to have to take it off minimum burn this year. Guessing I will be seeing 125-130° max plenum temps on max burn......so a △T of around 40° - 45°. Seeing it's speed controlled, the warmer the supply temps are the more volume of air being supplied. It's a win-win.

So I'm sending out much lower volumes of warmer air and it's heating the house better in ALL weather, even below zero. The slower I slowed the blower down the warmer the supply temps, the better the results were. In the temps we have been seeing this winter so far (warmer than average), I'm still not able to keep a fire going 24/7 w/o over-heating the house. Seems I need 50+ HDD's before I can burn 24/7 consistently. A far cry from what I was seeing at first.

I also added an OAK to the BD as well as to the basement floor for makeup air. Was worried about it contributing to the "stack effect" of the house, but don't think it has. This has also seemed to have made a positive difference.

Anyway, the whole point of this rambling is everyone's house and setup is different. Don't be afraid to try different things. They may or may not work, but you won't know till you try them. I've tried things in the past which made things worse, but I wanted to try them. I was also unsure about the OAK on the BD, but it seemed to work out just fine.

Brenndatomu's Skunk Works ????

yeah, pretty much!

 

[sloeffle]

@JRHAWK9 are you measuring your T at the register or in the plenum of the wood / gas furnace ?

I too also noticed that my house heated better when my fan is on speed 2 vs speed 3. It heats a lot better when the fan speed controller and the fan is on speed 2.

 

[Mrpelletburner]

What is “BD”?

 

[maple1]

Barometric Damper.

 

[Mrpelletburner]

Ok... OAK?

 

[maple1]

Outside Air Kit

 

[JRHAWK9]

@JRHAWK9 are you measuring your T at the register or in the plenum of the wood / gas furnace ?

On the LP furnace the cold air was measured about 5' vertically upstream of the LP furnace's air filter and the supply temp was measured in the main supply duct 12' downstream of the plenum, not including the height of the plenum. So about 14.5' including the height of the plenum.

Wood furnace....the cold air temp was measured inside the blower box. The supply was measured in the same spot in the main supply line which happens to be the same 12' from the wood furnace plenum. Again, not including the vertical rise/height of the plenum. The same 14.5' if including the vertical rise of the plenum. I also use a Thermoworks Smoke BBQ thermometer to be able to remotely monitor plenum/stack temps. When things are all up to temp and are cruising, the plenum temp from the BBQ thermometer (which is right at the very top of the plenum) matches the temp in the supply duct 12' downstream.

I have an analog HVAC temp gauge permanently mounted in the supply duct in that spot 12' (in horizontal duct length) from both furnaces.


I also have a gauge up on the ceiling right at the intake of cold air of the wood furnace. This allows for me to see the △T between the air at the ceiling and the air being sent into the air jacket to be heated, which includes the air being injected from the face of the furnace.

Also have the same HVAC temp gauge stuck into the 6" duct right before the BD to see what temp the air is I'm mixing with the flue gasses to send up the chimney. Lowest I've seen was 20°.....when it was around 0 outside IIRC. This was late last year.

 

[JRHAWK9]

$hit I'd at least hope you have fans to push that heat down out of the peak. Not really any easy solution to better insulate your roof without having an attic.

yeah, we have two ceiling fans running 24/7/365.

Here's an example of what I mentioned above.
We got 4-5" of snow overnight. Temps dropped to 14° overnight and when I went out to blow snow this morning I looked up at the roof and this is what I saw.

 

[JRHAWK9]

I have learned plenty in he short time I have been on this forum and am sure to learn more yet thanks to the more knowledgeable members chiming in. If someone is having shorter than desired burn times,temps spiking to above 80 in the house and distribution blower running constantly( which seems to be some of issues Mrpellettburner is having to deal with)- In theory if the lower limit switch was moved from 100 to 120-125 shouldn't this allow for a lower BTU output causing the distribution blower to cycle off and on and help to extend burn times????

IMO, from a strictly delivered efficiency standpoint. you want the distribution blower running as much as you can. Otherwise you are just wasting BTU's. It won't be able to strip anything off the flue gasses if the blower is not running.