Noobie to pellet stove,how do you adjust air and pellet feed to get max heat out of stove, seems to me alot of heat goes out the vent pipe.I have greenfire g55 stove,
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When you reach the top limits of what your stove will produce you will notice the vent pipe getting hot. Basically you have passed the efficency side of the stove and are making more heat then the stove can recover and the excess is melting the snow outside. So burning a stove at 75% of wide open will be more efficent then burning at 100%.
When buying a stove they are rated at so many BTUs. Basically we know how many BTUs are in a lb of pellets so then we see how much pellets a stove can burn in a given time to determine how many BTUs the stove will produce. The "kicker" comes in when we want to see how much heat is captured and blown into the room versus how many BTUs is being blown out the vent melting the snow outside. This is the part where buying a bigger stove and only burning it at 75% capacity is better then trying for every btu you can get with a smaller unit. You could use the Harman 43 and 68 as a example of what I am saying. Both are good units but if you push the max amount of pellets through a 43 and could measure the wasted heat out the vent pipe versus burning the same amount in the 68 and measureing the wasted heat you would see the 68 is capturing more heat from the same amount of pellets
Harvey Schneider
Minister of Fire
Watch the snow melt where the exh is discharged. It won't melt until the stove is running wide open or if you can put a therm into the exh pipe.
Gary, can you give some more detail on the thermometer? I did a cursory Google search and I'm coming up with a magnetic thermometer that sticks to the front of the stove. I'm not sure that would give us an accurate reading. Most of the front of our stove is glass, so the thermometer won't "stick." Also, the metal surfaces of our pellet stove stay pretty cool to the touch.
We have heat exchange tubes in the top of the fire box; our room air blower pushes air through those tubes and out into the room.
When I've had questions about the temperature of the air being pushed out of the heat exchange tubes I've stuck a candy thermometer (a thermometer inside a glass sleeve) into the front opening of one of the heat exchange tubes. This measures the temperature of the air flowing over the thermometer, while the glass sleeve provides a buffer between the actual thermometer and the metal surface of the tube.
Given that the candy thermometer is glass, I am *very very* careful with this exercise, and obviously I don't leave the thermometer in the tube. Take temperature/remove thermometer/put it away.
I am interested in a device that will help us measure temperature output continuously. We could as you suggest, adjust our damper setting to keep from dumping so much heat out of the vent pipe. I know that the standard advice is to open the damper only until the flame in the burn pot changes from lazy and orange to bright yellow, almost white, and sharp and active. For our stove, that change when the damper is *baaarely* opened, not even opened as far as damper setting #1 out of 5 possible graduations. That doesn't seem realistic to me, and attempts to burn the stove with the damper closed more than about #1.5 out of 5 have resulted in a dirty burn. A thermometer may help, as you've said, to adjust the damper to the optimal setting.
I seem to remember some forum members tracking temps with a thermometer type device... can't remember what it was.
Mpodesta
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Harvey Schneider
Minister of Fire
You could use a thermocouple meter.
(broken link removed to http://www.ebay.com/itm/Dual-Two-Channel-2-K-Type-Digital-Thermometer-Thermocouple-Sensor-1300-C-2372-F-/400542887700?pt=LH_DefaultDomain_0&hash=item5d42376f14)
Even the cheap thermocouple meters are more accurate than you need.
The thin probe wire will not block air flow and is fast to respond.
The one I have pointed to is just an example. I have not used that one.
Be aware that changes in the convection blower speed will have an influence on convection temperature.
The thermocouple can be used to sense combustion temperature which is a better indication of heat extracted from fuel.
I don't really focus on heat, but on pressure difference between inside and outside the house. For example, I used to have a monster wood stove insert where all fresh air intake was from inside the house. It didn't have a fan, but wasn't totally radiant - there was an air heat exchanger built in. Since most of the heated air went up the flue - all the fresh air was drawn in from the house; the vent in the bathroom, windows and doors, outside wall receptacles, even the floor wasn't all that sealed. The result of this was that the colder it got outside, the hotter I would get the stove. The stove would turn dull red and get the living room 90 degrees - while the bathroom with 4" vent would get downright frosty and the bedrooms weren't much better. We were relying on radiant, but beyond that - we were drawing in fresh cold air from other parts of the house - actually making it colder in those areas. The house had negative pressure.
The reason I wanted a pellet stove was to finally have the opportunity to create positive pressure by the stove drawing the fresh cold air in from outside, not from inside the house, and turning all the normal gaps in the house into air exhausts, not intakes. Now we rarely turn the pellet stove up over it's lowest setting, (I'm hoping I've fixed the last negative pressure problem and am looking forward to really cold weather to test it out). My laser thermometer will only go up to 500 degrees, and the ol wood stove would be well above that when cherry red, but the house was much colder then.
This same principle is used by commercial buildings and "grab and go" cooler cases at the store; by maintaining positive pressure inside something, you can maintain the temperature. If you had enough positive pressure you could take the front door off the hinges all winter and stay toasty warm - even standing in the opening. Not very efficiently though! But that's how stores can have big gaps in their doors and be above outside temp.
I used to use a Magnehelic all the time when doing HVAC work - mostly to check filters. They measure pressure differential. I'm not going to go out and buy one, don't need the accuracy, just need some way to gauge positive and negative pressure and loosely how much. I seal up the house as best I can and use a strip of paper to test, (rip a thin 4" strip from a single ply of two ply TP). Crack a window open a little and hold the paper up to it - is it going in or out? How much? I want it to go out a little, not too much, just slightly for good efficiency. It took a little effort, but I finally achieved positive pressure with my pellet stove, the only time going negative when the bathroom fan is on - I'm good with that. Now if I want to know if the stove is working I'll feel the output. Is it hotter than the room? Yes? It's working. I've spent way too much money over the years on thermometers for the wood stove - I should pull one out and check the pellet stove. I know I can touch the output on it - something that would be crazy to do on the red hot woodstove. I can't believe we raised three toddlers with that thing in the house - used to sleep with one eye open.
The reason I wanted a pellet stove was to finally have the opportunity to create positive pressure by the stove drawing the fresh cold air in from outside, not from inside the house, and turning all the normal gaps in the house into air exhausts, not intakes. Now we rarely turn the pellet stove up over it's lowest setting, (I'm hoping I've fixed the last negative pressure problem and am looking forward to really cold weather to test it out). My laser thermometer will only go up to 500 degrees, and the ol wood stove would be well above that when cherry red, but the house was much colder then.
This same principle is used by commercial buildings and "grab and go" cooler cases at the store; by maintaining positive pressure inside something, you can maintain the temperature. If you had enough positive pressure you could take the front door off the hinges all winter and stay toasty warm - even standing in the opening. Not very efficiently though! But that's how stores can have big gaps in their doors and be above outside temp.
I used to use a Magnehelic all the time when doing HVAC work - mostly to check filters. They measure pressure differential. I'm not going to go out and buy one, don't need the accuracy, just need some way to gauge positive and negative pressure and loosely how much. I seal up the house as best I can and use a strip of paper to test, (rip a thin 4" strip from a single ply of two ply TP). Crack a window open a little and hold the paper up to it - is it going in or out? How much? I want it to go out a little, not too much, just slightly for good efficiency. It took a little effort, but I finally achieved positive pressure with my pellet stove, the only time going negative when the bathroom fan is on - I'm good with that. Now if I want to know if the stove is working I'll feel the output. Is it hotter than the room? Yes? It's working. I've spent way too much money over the years on thermometers for the wood stove - I should pull one out and check the pellet stove. I know I can touch the output on it - something that would be crazy to do on the red hot woodstove. I can't believe we raised three toddlers with that thing in the house - used to sleep with one eye open.
This is one of the very best, most concise but comprehensive real world examples of why a pellet stove with an OAK is a better alternative than many other wood burning devices that I've ever seen written up. This is, IMHO, a really good explanation of why an OAK works. I've seen lots of people explain that the stove will pull combustion air from *somewhere,* and if you don't provide it with an appropriately installed OAK, it's going to turn every crevice and leak in your house into an OAK, but this is a stunning example of negative vs. positive pressure and how it works in real life.
I will use this opportunity to admit that I broke down and bought a Smart Sensor AR-320 infrared thermometer last night on a discount web site for $13.42 (I got these discount points when I put the thing in the online cart, so I used them immediately to knock an additional 20 cents off of the purchase price) with free shipping. We thought about getting an infrared thermometer when we first got the pellet stove, to help us figure out how to set the damper for the most efficient burn, but at that time we couldn't find an infrared thermometer for less than about $35. We were fresh off of paying for the pellet stove, the hearth pad, the installation, the vent pipe, the thimble, the OAK, and three tons of pellets, SO NO WE WEREN'T GOING TO PAY ANOTHER $35 FOR A THERMOMETER THANKS LET'S GET SOME RETURN ON THIS INVESTMENT ALREADY. I'm just now getting back to this idea and in the meantime it seems that prices have dropped in IR thermometers- or at least there are some available on discount web sites.
So I'll spend this season playing with the thermometer vs. the damper (that's about all there is to do on our stove- we have a "most efficient feed rate" and a variable convection/room fan adjustment and that's all) and we'll see what we see.
http://www.tmart.com/Infrared-Thermometer-for-AR-320-Orang-Black_p170464.html
Thanks for the Kudos - just a few thoughts developed while freezing in the bedroom at night.
That's a really good price on the thermometer. It really is a must have tool. Some of the odd ball stuff it can do; check belt and pulley/sheave wear, check bearing wear on electric motors, find how efficient a steam trap is working, find a loose connection inside your breaker box without having to stick your hands in, and before the heat melts the wiring insulation for a visual clue. Best thing ever was knowing where a fluorescent ballast is in a fixure before getting a ladder and looking.
That's a really good price on the thermometer. It really is a must have tool. Some of the odd ball stuff it can do; check belt and pulley/sheave wear, check bearing wear on electric motors, find how efficient a steam trap is working, find a loose connection inside your breaker box without having to stick your hands in, and before the heat melts the wiring insulation for a visual clue. Best thing ever was knowing where a fluorescent ballast is in a fixure before getting a ladder and looking.
I am not looking for my thermometer to be precise, I just want it for comparison. I agree that my thermometer is not that accurate but I can tell at a glance if something is awry. It tells me things when I change pellets or even when it's time to do a good cleaning. I get some sort of a base line to go on and not just THINK that a new pellet is not good or whatever the situation. If you want 1% accuracy an inferred heat gun is only about $50.00 and you may be able to use it for other things.
I have to admit that tweaking is half the fun of owning a pellet stove. Sort of like owning a hot rod
Hi, Gary! I wasn't trying to bust your chops over your thermometer accuracy. I was trying (ham-handedly, sorry) to say that I don't know where I'd stick a magnetic thermometer on this stove that would even begin to record a representative temperature of the air it is pushing into the house. The portion of the stove that conducts heat is the glass, and the heat exchange tubes which are internal at the top of the firebox. The top and the sides of the stove are cool to the touch when the stove is running.
Per above I found an IR thermometer online for a few bucks- prices seem to have come down quite a bit since I last looked at them. My hope is that I can learn to use it to adjust the stove's damper, to keep from dumping any more heat out of the exhaust pipe than necessary. Per above, again, our flame changes from lazy and orange to bright yellow/white, sharp and active at an unbelievably closed damper setting. Kinda makes me doubt my own eyes... so learning to use the IR thermometer vs. the heat coming out of the heat exchange tubes may confirm what I'm seeing happening in the burn pot vs. the damper setting.
The bottom line is getting the maximum amount of heat out of the stove- and yes, fiddling with it is a bit of a fun experiment!
You know... I have a question about a wood stove vs. an OAK, positive vs. negative pressure. Is there any way to hook up an OAK to a wood stove? Do any wood stoves have them?
Sorry for the late reply - busy trying to get all my welding done before the freeze! (Uninsulated garage)
I'm not sure if they make wood stoves with OAK. There were two small intakes for the exchanger on the old stove I had that channeled up to the top. I had thought about fabbing up my own OAK, to them, (I experimented one time by shoving a hair dryer into one of the holes - it blew out quite a bit of heat). The intake size of an OAK to the firebox of a woodstove would be fairly large - woodstoves just aren't that efficient inside the house. Maybe outside w/exchanger.
One happy thought - We've had cold weather the past few days and I've really had a good time testing out the house's positive pressure. Right now it's 16 degrees outside; the pellet stove has been on for an hour and maintaining 67 in the main part of the house with 65 degrees in the back bedroom - this is with the stove set on the lowest setting, 1 and 1. A plan came together! The past few days I've been monitoring things - basically with the current insulation in the house and positive pressure, the stove has no problem getting the inside temp up to a 54 degree temperature differential from the outside temp with it set to the lowest setting. I played around with keeping the bathroom and bedroom doors open and closed - the only difference it makes is the time it takes to heat things up. One thing I've noticed with the positive pressure is I need to work on the door going to the garage - if I don't make sure its latched, the pressure will blow it open about an inch. I can feel a little cold air coming in the bottom 6" of the crack, but above that I can't feel a thing when I put my hand to it.
In contrast, the past two years without OAK and positive pressure, we would turn the stove setting to 2 or 3 when the outside temp would drop to freezing and the bedrooms/bath would be cold. When the temp would drop to the teens we would keep the stove almost full blast in the morning to get things warmed up and then to 3 or 4 to maintain. 100% different this year, I'll save a ton of pellets. Now I just have to work on insulation. The house maintains a 30 degree temp differential for quite awhile, but I'd like to improve that.
Harvey Schneider
Minister of Fire
Just a thought about monitoring stove effectiveness.
Monitoring the actual stove temperature really tells you little about what is going on. What you really need to know is:
Think of it this way.
For a fixed convection blower speed, stove temperature gives some indication of effectiveness. What can be misleading is that if the house is cold the stove will be cooler, if the house is warm the stove will be hotter. This is because a heat exchanger's function is based on the difference in inlet to outlet temperature, and they are pretty close to linear in our area of interest.
Sorry,
This may be more than anyone is interested in knowing, but I keep seeing people trying to optimize their stove based on the wrong information and the Engineer in me cringes.
Monitoring the actual stove temperature really tells you little about what is going on. What you really need to know is:
- The difference between exchanger inlet and outlet air temperatures
- The volume of air moving through the heat exchanger
Think of it this way.
- If the convection blower is off, the heat exchanger gets very hot but, there is no heat being transferred. High stove temperature but not heating the house.
- If the convection blower is moving a lot of air, the stove temperature is low, but the product of CFM and delta degrees greater, so there is more heat being delivered to the house.(The implication of this is that you always want the highest convection speed that your ears will tolerate.)
For a fixed convection blower speed, stove temperature gives some indication of effectiveness. What can be misleading is that if the house is cold the stove will be cooler, if the house is warm the stove will be hotter. This is because a heat exchanger's function is based on the difference in inlet to outlet temperature, and they are pretty close to linear in our area of interest.
Sorry,
This may be more than anyone is interested in knowing, but I keep seeing people trying to optimize their stove based on the wrong information and the Engineer in me cringes.
That's a good point about air density and inversion. I see a lot of posts about people setting up box fans to move air around. I used to do that when I had the wood stove to try to make use of the radiant heat that thing gave off, (high heat transfer, low CFM). The pellet stove throws off very little radiant heat. I have to stand right in front of the output to feel much on a cold morning. When the room is cold, standing on either side of that warm air flow just feels like room temp.
Using a ceiling fan in the living room with the wood stove helped. When I put the pellet stove in, I noticed the airflow from the stove basically shot straight out about 6 feet and then turned vertical the next two feet to the ceiling. I moved my ceiling fan to this point on the ceiling, (actually 7' out - to the center of the airflow and this is where the stud lined up, lol). This probably had the biggest effect of making the living room, and the adjacent rooms have even heat. It's not quite centered as before, but it doesn't look odd and does a lot better job of equalizing air density.
Helps with the wife, too. She missed the radiant of the woodstove when I made the change. Her chair sits next to the stove. Now, once I get the house up to temp, I just click the ceiling fan switch so it blows down. This throws things off as far as getting rid of inversion, but gives her more of that "woodstove" feel she likes, (drives me nuts when I'm on the couch - way too hot).
Using a ceiling fan in the living room with the wood stove helped. When I put the pellet stove in, I noticed the airflow from the stove basically shot straight out about 6 feet and then turned vertical the next two feet to the ceiling. I moved my ceiling fan to this point on the ceiling, (actually 7' out - to the center of the airflow and this is where the stud lined up, lol). This probably had the biggest effect of making the living room, and the adjacent rooms have even heat. It's not quite centered as before, but it doesn't look odd and does a lot better job of equalizing air density.
Helps with the wife, too. She missed the radiant of the woodstove when I made the change. Her chair sits next to the stove. Now, once I get the house up to temp, I just click the ceiling fan switch so it blows down. This throws things off as far as getting rid of inversion, but gives her more of that "woodstove" feel she likes, (drives me nuts when I'm on the couch - way too hot).
It's not a bad idea to buy a cheap infrared thermometer like the one beca mentioned (above in thread, with a link). I use one from Harbor Freight that's similar. Then create yourself a simple spreadsheet, with damper setting down one axis (Say, L / LM / M / MH H, to not setting from Low to Medium to High). On the other axis put labels for your pellet feed settings (I use the same labels, Low to High). Then just start experimenting, using the same brand of pellets... I stand at a certain point in front of the stove and point the laser dot of the thermometer on exactly the same place where the air blows out of the stove (from convection, not combustion, blower). And I record the temp at various combinations of the settings. I use the convection temp because if the fire looks "healthy" (color, size, speed of movement, etc.) then all I really care about is the amount of heat I get for the lowest possible pellet feed rate.
Now, none of this really works as well with an "automatic" stove like my Quad MVAE. But it works well for a stove with more manual settings like my old Whitfield Quest.
Just a thought on a process that works for me...
Harvey Schneider
Minister of Fire
An infrared thermometer will give you the temperature of the metal at the port. That is reasonably a good indication of air temperature but not the same thing. If you want to be a purist about measurement, nothing can beat a thermocouple suspended in the air flow.
With cheap infrared thermometers there is a symbol on the bottom that indicated how big the area being measured is and it's about 10 to one. So if your 10 feet away the area being measured is one foot. At one foot it's 1.2 inches. Just in case your interested. That is all.
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