Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by alltherage, Dec 7, 2012.
Yes which as why my mention of the 8 core was off topic.
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oh - I had it backwards! I get it now.
There going to block-off air flow, which would raise the temp anyway?
Can you elaborate on your basement setup...how big a 1st floor and how big a basement? finished basement? do you have a openings for the warm air to rise, like an open cellar door etc, or does it radiate?...I know it's been talked about on here a bunch regarding the difficulty in accomplishing what you're doing so i'm interested to hear a success story..thanks
I'm pretty sure that there is a high temperature sensor on the stove so you probably won't overheat it and melt it down. Before and after air temps (even using a oven thermometer) while running the covection fan at the same speed might be interesting, but they would be higher because cfms would be down using the sinks. I suppose the cfms loss could be calculated and the fan speed increased so the test would accurate. Obstructing the air flow may have some negitive effect on your motor. I'm sure that one of resident electrical gurus can tell us if creating a back pressure will damage the motor. Only after conducting these (and probably more) tests can we say that the efficiency of the stove has been increased and by how much. If your only gaining 1% its probably not worth it. If your gaining 5% it probably is. At the present time we have no idea whether your house is warmer because its not as cold outside, your door hasn't been opened as many times today, or your stove works more efficiently a lower cfm across the exchanger. That said good thinking, you may have something.
If any air flow actually gets blocked off (and that likely isn't the case at the moment from what I'm seeing). But a few measurements would tell us for certain.
What I would like to see is what tj did in the way of measurements on the exhaust temperature side. Before and after the addition of the heat sinks.
Yeah it may have slowed the air flow down a little. Hard to say how much with out a flo meter test before and after. Slowing it down may not be such a bad thing. It should allow the air to pickup more heat. All i know is the aluminum I placed in the lil Englander got hot. So its pulling heat from the stove. And as the convection air passed over it the heat is then being transfered to the air. I'd say its gotta increase the effiency, Even if its just a small amount. We did not measure stack temps. That is a sure indicator if the stack temps dropped at the same heat range.
Yep, The heat sinks are going to add some extra cleaning time to the unit. I'd add cleaning them to the schedule. And probably safe to say it will be close to the same interval as the convection blower wheel cleaning cycle.
jdempsey, Did you cover the hole you cut to put these heatsinks in? I would just to try and keep as much air passing over the heatsinks. Another way would to maybe add a removable face plate that would allow installation of these. Either way with the 10cpm you'd be cutting something. The 25 Ip has a removable grille so I didn't need to mod the stove.
Keep us posted on how it goes.
Basement is 900 sq ft. (finished except floor is bare concrete) Upper level is about 1300. I leave the basement door to the stairwell open. I did not have any luck at all getting heat upstairs by doing all the usual things. Alot of you all push or pull heat with fans positioned at different places. Did not work in my situation. I mean i spent hours and days trying to get it to work. I gave up. And decided to try something different.
Now, My setup is not typical.I finally decided to run duct and direct the heat to locations upstairs. Several other guys on here do the same. I did cut holes in the floor to attach the duct. But i did not want to cut random holes all over for return air. But here is what i did bit different.
I installed three 6 inch 425 cfm inline duct fans. They are all connected to the variac in the picture. I can throttle the speed up or down. I usually keep them between 60-80 volts. This provides good flow and cuts down on noise. The fans are connected to a ductstat. This turns them on and off when there is no heat. The metal duct boot that you see on the front of my stove was made by cutting three floor ducts and taping and sealing back together. I applied high temp silicone to the face of the duct to create a rubber seal. I made a latch that secures this to the heat oulet holes on the front of the stove. No air leaks. Or sucking air. Tried this without sealing and the air being sucked was cooling the heated air a bit.
The reason i seal this. Well those inline fans when running almost full speed can suck more powerful than any shop vac. Another reason to throttle those down. The fans can pull so much air the heat exchanger drop temps considerably. I finally got this all running optimally and it works really well.
But if i had to do over i think i would have just put another stove up stairs. Been thinking about an insert for my fireplace. Not really because i need it. But it would be nice having the glowing of a fire upstairs instead of being hidden in the basement. The best advice i have ever got on this forum. Put the stove where you want it or buy a pellet furnace.
Yes i did cover the hole. I use hi temp silicone to a 1/4 inch piece of steel to seal it up. There is still about 3\4 of space between all the heatsinks and top of the metal plate and 1\2 to 1inch space on the sides of the heatsinks. There is plenty of space and im sure no restriction of airflow.
My inline fans help draw the air from the heat exchanger also. So i have a constant push, pull of heat.
Still looking for my temp probe so as to get some measurements.
In for one mod in for several don't let Mike see that.
Dang!! nice...you have more patience and drive than me!! well done
Any time you place something in an enclosed duct you restrict the air flow. Example: one heat sink 4 sq.in. duct, 40 sq. in. result duct size reduced by 10%.
However if you place all heat sinks in line you will reduce the overall signature. You are also creating turbulence within the duct this will also lead to a loss in cfms. My only concern with the project is whether the resulting back pressure will prematurely cause fan failure. Other than that I am watching with interest, but, I'm pretty sure this has been tried by Englander. I'm sure this is being monitored by Mike and it would be interesting to hear what he has to say.
I usually don't run the stove at night. Just set the heat pump on 69. Better sleeping that way. But the stove has been running since 6 am this morn.
As stated earlier im getting the same heat at one feed rate lower. Its been 32 most of the day running feed rate 3. Its now 29 and I bumped up to rate 4. Usually at these temps I'm running on feedrate 5. The temp upstairs is 73.
I'm no engineer but the inline fans would help ease any restrictions as they are pulling the air from the heat exchanger steadily. And thus helping the convection blower.
I work at home in my basement and only sit several feet from the stove and monitor it closely.
The turbulence slows the air slightly and increases its interaction with the walls. This improves heat transfer. I doubt that this will cause any problem for the blower, other than to decrease the amount of air being drawn in for combustion.
Not on the combustion side Harvey completely on the convection side.
I,m not to sure if Mike is running to home depot to get boxes of flex, fans, alum angle, digging in computer trash for heat sinks. (Englander Pellet Furnace for 2013) LOL.
I asked about that a few years back. Still nothing in the works. I'd be on the check it out list. But if it doesn't have a real heat exchanger? Then nope!
Figure I can get a couple more years out of my Omega~mini furnace~stove. But I'm looking!
A company the size of Englander has probably tried putting heat sinks (simple cheap cast iron) in the convection duct. The reason they don't is the one that interests me (and they are not likely to tell us). Was it a minimal increase in heat (say less than 5%), or an increase in production cost per unit that nixed it. I believe that there higher end units have tubes which are more efficient but cost more to produce. For an increase of 5% I may be willing to try it.
Yes, Tubes would be more costly. But accordian would be a minimal cost adder. IMHO, They need to do something to increase the area of the heat exchangers. "Every little bit helps" rule should apply here! Even if its a minor cost adder.
There is probably a table/chart put out by the fan manufacturer that gives you the cfm value for the duct size (area). On the stove we have 9 speeds on the fan, you would be looking for the average duct size that fits with all the speeds. It would show as nonlinear on a graph, over laying the 9 speeds would give you a peak efficiency. Putting an accordion would decrease the size of the duct and increase length. Or we could just spend more money and buy a stove with a more efficient heat exchanger, but that wouldn't be much fun.
There are several things that keep companies from implementing product "improvements".
High volume products are extremely sensitive to cost of goods sold. That cost includes not only the cost of materials, but also includes assembly labor. While popping a hole and dropping some objects into the air path may work for an individual it isn't a manufacturable design.Then in addition to cost of goods considerations there are design test and certification issues. Running a product through test labs (UL, CSA, ETL, etc.) is a very expensive endeavour. I have taken many of my designs through the process and have always been astounded at the final total cost.
When it comes down to it, Engineering and product design are not profit centers, they are cost centers. Marginal improvements in the performance of a successful product are unlikely to gain the approval of the people responsible for seeing that the company remain profitable. Will a 5% improvement in efficiency cause enough of an increase in sales to cover the cost of development and yield a return on investment profit?
That is not to say that improvement of a stove is not a worthwhile thing to do. You have to keep in mind, however, that you invalidate all of the safety testing that has been done on the product and probably are violating local codes as well as voiding your home owners insurance. If you feel that your smoke detector and CO detector give you enough time for a comfortable escape, who am I to suggest that you are foolish to cut holes in your stove and place objects of unknown melting temperature in contact with a wall of the fire box (most aluminum alloys melt at between 865 - 1240 deg F).
Nothing is ever as simple as it seems on first glance.
I am just trying to be the voice of reason.
Fan manufacturers do not produce any tables/charts that gives you airflow (cfm) related to duct size. The longer the duct run, the more resistance there is on the fan (external static pressure) resulting in lower airflow. They should however have "fan curves" that plot the cfm vs. total external static pressure.
All industries give out specs on their product, while there are formulas available to calculate the size, rpm, and volume no one has the time or inclination to calculate them. When I design a water or filtration plant I'm buying a product that is worth millions. All engineering disciplines have associations that publish data sheets. Harvey Schneider is right when he says it may not be economical to produce. He is also right when he points out that by altering the stove you remove your home insurance liability. As a exercise for increasing your stoves efficiency this thread is interesting, but, it should be carried out in a manner were no one is at risk from the out come of the experiment. All test should be carried out in the appropriate safe environment.
There are published cfm ratings given various static pressures, places like Grainger list them in the details for the blowers.
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