FPX Fire Uneven

[Snakebit12]

Guys,

We have fired up our new FPX 44 as we have been dipping down into the 30's at night. It raised the temperature in the great room to 75 and the nearby rooms to 70 - it really puts out a lot of heat. It also eats a lot of wood!

I am getting maybe 6 hours of heat between loads - as defined by the time the fan is running. I hope to improve on that as I gain more experience.

Some black glass - mainly towards the handles on each door - I hope to improve on that too.

One strange thing...when I reload, the fire ALWAYS initially takes off on the right hand side. It consumed the wood on the right and then shifts over to the left where it completes the burn. This has happened repeatedly. And I am at a loss to understand why.

My fear, of course, is that the cooling vent that connects on the left side has failed which would likely involve tearing out rock fascia and durarock to gain access to the unit - not a good thing.

The fireplace runs north/south - and the side firing up first is south which is the direction of the wind. But with a 28' chimney, I would not think that would be a factor.

Anyone have thoughts?

 

[prezes13]

I am thinking it might be the wood moisture. I have on insert and no matter how I load it it will start from the hottest point which will be the coals and primate air entry but eventually the whole load will take off. With dry wood of course.

 

[Snakebit12]

Thanks - The wood was split about 18 months ago - primarily oak. Fresh splits test just under 20%.

From reading the FPX brochure - "As the fresh air is directed to the primary combustion zone of the fire, it is drawn evenly across the glass by a sophisticated air wash".

I'm not convinced that the air is being drawn evenly across the glass:

1. The right side burns more aggressively
2. The left side glass door has far more black glass than the right side glass door

Could something be wrong with the air wash system...and, if so, can it be fixed with the unit in place?

 

[jeff_t]

That is a really wide firebox. I would say it isn't unusual, but six hours with a 4+ cu ft capacity ain't right. I'd be checking some gaskets.

Did you install it yourself?

 

[webby3650]

I would guess that you have a leaking gasket. Check the door and glass gaskets. These have a flat gasket on the door, if too much cement was used it could have a hard place in it preventing it from sealing good.

 

[Snakebit12]

I did not install this myself - used a local certified chimney sweep who had prior experience with the FPX.

Didn't think about the gasket - that is a very plausible explanation. I will check that once it warms up outside a bit and I can let this baby cool down.

 

[webby3650]

I did not install this myself - used a local certified chimney sweep who had prior experience with the FPX.

Didn't think about the gasket - that is a very plausible explanation. I will check that once it warms up outside a bit and I can let this baby cool down.

Wow, that's a very difficult unit to install. There is a lot to know with this particular unit. I hope he followed the instructions closely.

 

[Snakebit12]

He followed them to the letter...I "supervised" to make sure but he took no shortcuts.

He's been in the business for 20 years has done a hundred or so installations...but just one previous FPX 44.

 

[Isaiah53]

I have been waiting to hear about your experiences with your new 44 Elite. I also see uneven burns at times but it is not consistently on one side or the other. It is a large box so I would imagine a slight imbalance in air distribution could cause it. My experience with creosote formation on the doors is almost opposite yours - heavier in the lower outer corners and also heavier on the right side door. When I add additional wood to a hot fire and there is a lot of degassing and smoke formation in the firebox, I can see a strong air wash coming down from the upper left hand corner across the left door.

I am curious how much you load up the firebox and how low you turn the air down for the 6 hour burns. I do not get more than 6 hours either, but I rarely attempt to load it full except when going to bed at night on really cold nights. The shape of the box and lack of depth does not really lend itself to loading it like a stove. We tend to run it more like a fireplace, adding a few logs or splits as needed to keep the fire going at the minimum air setting I can get by on without heavy blackening of the doors. I would really have to pack it full and turn the air completely down to get the advertised burn times. It will run like a stove with almost no visible flame at minimum air flow, but every time I have tried this, I get a heavy formation of creosote on the doors that is difficult to remove. I seem to get this anytime I turn the air below about 1/4 to 1/3 of max air. If you or anyone else on this forum has discovered a way to avoid this, I would like to hear about it.

 

[Snakebit12]

Hey Isaiah,

Just spewing out random observations and thoughts...

Tonight, I loaded the box to the gills...5 - 16" splits and some shorter pieces to fill in the corners. That is the most that I have crammed in there - I am worried about logs falling against the glass or I probably could have fit one more 16" split. Most of it is oak although there may be a split of crappy poplar in there which really doesn't count (BTU-wise).

I am experimenting and my only "independent" guide is a Condar Inferno Stove Top Thermometer that I have attached at the top of the right hand door above the handle.

After lighting with full air and a disengaged cat, the blower turned on at 200°. This has happened consistently for 5 fires now. My blower is in a ventilated attic drawing in outside air.

At 300°, I engaged the cat and it glowed bright red.

The temperature quickly ran up to 400° when I cut the air back to about half.

The temperature continued to climb to 500° (highest I've seen so far), where cut the air all the way back. I figured that, if I cut back to 25% as some others have done, that I will burn through the load of wood too quickly. Plus, I was a little nervous about hitting 500°!

It has been burning now for 2.5 hours, the temperature is slowly dropping - at 375° now - and it is 73° in our family room - this thing does pour out serious heat. And no smoke in the house at all (so far). The cat is no longer glowing. No flame at all on the left - just flaming red logs. Slight flame on the right but I think that I have a gasket issue on that side (which initiated this thread). Not sure if I cut back on the air too soon or not - but the glass is clean so far.

Now, with the lower temperature, I moved the lever left so that the left edge of the slide aligns with the left edge of the right hand door - maybe 1/4 open?

I don't have a recipe here - just trying out different techniques. It would be nice if we had an FPX owner with a Stove Top Thermometer who could advise on the temperatures that he/she adjusts the two controls (cat & air).

I don't see getting more than 6 hours out of this load. My wood is fairly well-seasoned...split 18 months ago. The FPX does have a healthy appetite for wood. But I do have quite a bit stockpiled.

Going below freezing tonight so I may try and refill before I go to bed. It is supposed to warm up this week giving me a chance to vacuum up a lot of ash and do the "dollar bill" test on the right side gasket.

This is a great fireplace but I'd sure like to get an additional 2 hours out of a burn. It will be fun to play around with this all winter.

 

[Isaiah53]

I may pick up a surface thermometer for comparison. I had not thought of doing that. I would really like to know what the cat temperature is, but I am not going to alter the fireplace to know that. I rarely see the cat glowing except when it is being fired very hard. I can run the air down where the left edge of the slide bar is maybe 1/16" past the right side of the door with minimal creosote formation. Much beyond that, it tends to get ugly. I can get it down to small flames, but not no flame like the Blaze King stove I have downstairs.

I think you may have to figure a way to get more wood than 5 splits in the box to get significantly longer burn times. I agree that piling the wood up high is concern with it falling on the doors. I have thought about stacking a lot of short pieces north south and see what the results would be. I am not as concerned about the actual burn time, but I would like to use less wood. I probably went through 5 cords last winter. My wood is mostly smaller diameter pine and Douglas Fir. The high altitude (9000 ft) and low humidity tends to dry it very well. It is very light compared to oak and burns quickly. The blower goes out relatively early at night, but the house will still generally be in the low to mid sixties in the morning when we reload and light it off again. I don't know how much of this is due to the mass of the fireplace and how much is due to the insulation on the house, but even when it shuts down near midnight the house does not get that cold. There seems to still be a fair amount of coals and heat left in the fireplace when the blower shuts down. It does take about 30 minutes of high fire to get it to come on when the unit is cold.

 

[weatherguy]

How long are the splits you guys burn in this unit? Isnt it like 30 inches long?

 

[Snakebit12]

Weatherguy,

The 44 will take a 32" log towards the front tapering back to maybe 22" in the back. I cut my wood to 16" for no particular reason other than it is the most common length. Filling the unit is a bit like working on a jigsaw puzzle.

Isaiah,

I think that it would be great if you got a thermometer - it would give us a constant frame of reference during our "trial and error" sessions. I bought my Inferno at Condar's website - $23 delivered. I like it.

 

[begreen]

Good idea to check the door gaskets with a dollar bill test every 6 inches. Also, it sounds like the air could be closed down a bit more aggressively, once the fire is burning robustly and the cat has been engaged. Try closing until the flames get lazy, but don't go out. Repeat if the fire regains vigor after a few minutes.

 

[Isaiah53]

I also try to cut my wood to about 16-18", but the wide box does cause me to be a bit lazy. It is very convenient for taking odd and oversized logs near branch connections that I do not wish to take the time to properly cut to size.

Snakebit, I ordered the same thermometer. I will probably not get a chance to experiment with it until Thanksgiving week, but I will let you know what I find.

 

[Snakebit12]

I also try to cut my wood to about 16-18", but the wide box does cause me to be a bit lazy. It is very convenient for taking odd and oversized logs near branch connections that I do not wish to take the time to properly cut to size.

Snakebit, I ordered the same thermometer. I will probably not get a chance to experiment with it until Thanksgiving week, but I will let you know what I find.

Excellent! Look forward to comparing notes.

 

[Got Wood]

Been running the 44 for around 5 years now and despite lots of tinkering have not had much luck getting past the 6 "ish" hour mark. The glass issue was greatly reduced when my wood was better seasoned. My biggest beef with the 44 is its functionality when the air is turned down all the way (lever all the way to the right). Seems its sweet spot is left edge of the lever just a tiny bit past the center mark of the doors (roughly 75% closed). More than that and the fire seems to choke out, heat production drops, glass gets black....not pleasant.
I have resolved that it is was it is and take the great looks and heat production. Just a hungry beast that likes to be fed.

 

[Got Wood]

BTW - the best way I found to clean the glass is to dip a damp paper towel in the ash and use that to scrub the glass.

My guess on your original question is a gasket issue. I have found though that the flame of the fire does rotate around the wood in the box but havent noticed a pattern to it.

 

[Snakebit12]

Hey Got Wood,

Thanks for your feedback.

Used the damp towel with ash trick this morning - worked splendidly!

When I called it a night last night, the blower had been on for 7 hours but I was basically down to a heaping pile of coals I actually did shut the air down down about 75% for most of the burn - exactly where you stated - and noted that the coals glowed brighter and seemed to keep the unit hotter after the flames had died down than when I shut down completely. I didn't hear the fan kick off so I am guessing 8 hours of fan time - which would be my best so far.

I've been using the grate but will try without to see if I can jam a bit more fuel in there and lengthen the burn.

On the gasket, the dealer will send a technician by when they are in the area the next few weeks. We live in the middle of nowhere. Last night, it was flaming more on the left side so who knows. It will be good to have them check it in any event.

Warming up this week - actually hit 72° today in beautiful Middlebrook VA - so it's a good time to vacuum out the ashes, remove the grate, do the dollar-bill test and get ready for next time. I did double-check my wood and discovered that the logs I had were cut last September and split last December. So maybe it is not quite as seasoned as I originally thought. But it's all I have. I did pick up a cord of red oak that came down during the Durecho (June 2012) for this winter - it was cut and split last month and I still read 22-24% moisture internally which surprised me after 30 months. I put it at the tail end of this winter's supply hoping it drops below 20% in the next few months.

You're right - it is a wood hog. But it keeps things pretty toasty and is a absolute pleasure to view.

The boss loves it so far. That will change if I ever let smoke in the house. So far, none. People have visited and not known that we were having a fire until they saw it.

 

[Grisu]

I did pick up a cord of red oak that came down during the Durecho (June 2012) for this winter - it was cut and split last month and I still read 22-24% moisture internally which surprised me after 30 months.

That low moisture content surprises me after just being split a month ago - especially for red oak. Usually oak needs to be split and stacked for 2 to 3 years to dry properly and does not really dry when still in rounds, not to mention logs.

I would leave some ash in the firebox. That insulates against the bottom and will keep the firebox hotter for a better and cleaner burn.

 

[Got Wood]

A strong word of caution - dont vacuum out the ashes! You will burn your house down one day. The embers in the ash bed can stay warm for days. I use a shop vac to clean up the mess OUTSIDE of the fireplace but the only time I use it in the fire box is during my preseason "clean up" getting ready for the heating season when I know there wont be any hot embers still in there. What I do is shovel out the ashes into a metal pail and let that sit outside and dump in a safe area where it has no chance of catching fire.

I took the grate out shortly after I started with the 44 and never put it back.

 

[Snakebit12]

Already vacuumed out the box with a shop vac - spread the ashes in the horse pasture (which needs lime).

I re-checked the moistures:

• Oak rounds cut last summer and split last December: 16%
• Durecho oak split two months ago: 22-24%

Two moisture meters get the same readings. BTW, I store my firewood on pallets in a metal barn.

Assuming a target of <20%, I am burning the 16% firewood now. Not sure if the Durecho wood will reach 20% this winter.

 

[Snakebit12]

A strong word of caution - dont vacuum out the ashes! You will burn your house down one day. The embers in the ash bed can stay warm for days. I use a shop vac to clean up the mess OUTSIDE of the fireplace but the only time I use it in the fire box is during my preseason "clean up" getting ready for the heating season when I know there wont be any hot embers still in there. What I do is shovel out the ashes into a metal pail and let that sit outside and dump in a safe area where it has no chance of catching fire.

I took the grate out shortly after I started with the 44 and never put it back.

I do not understand your concern about vacuuming out the ash. We just shoveled it out and it was a bit dusty, which is not a concern when you vacuum. SWMBO prefers to vacuum unless I can come up with a compelling reason otherwise.

Is the concern that we would vacuum the ash - including some buried hot embers - and leave them in the vacuum? Our plan was to immediately take the vacuum outside, dump it and spread over the pasture/garden when cool. Granted, we could leave a bit in the bottom for insulation purposes.

 

[Isaiah53]

My wife used to vacuum out the ashes with a shop vac until one morning it pulled in some buried embers and flames came shooting out of the exhaust port. You are pulling in a lot of fresh combustion air into the vacuum and there are likely other combustible materials inside the vacuum in addition to the embers. I guess it was fortunate it flamed up immediately. Leaving it smoldering in a vacuum stored away in a closet with a delayed ignition would have been much worse. It is too easy to shovel the ashes out. Even then you have to be careful where you store or spread them.

 

[Got Wood]

My wife used to vacuum out the ashes with a shop vac until one morning it pulled in some buried embers and flames came shooting out of the exhaust port. You are pulling in a lot of fresh combustion air into the vacuum and there are likely other combustible materials inside the vacuum in addition to the embers. I guess it was fortunate it flamed up immediately. Leaving it smoldering in a vacuum stored away in a closet with a delayed ignition would have been much worse. It is too easy to shovel the ashes out. Even then you have to be careful where you store or spread them.

I could not have explained it better