LL AA-220 Max Draft Burn With Power Vent Please Help!

 
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swyman
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Post by swyman » Sun. Nov. 29, 2015 8:05 pm

WNY wrote:I assume you're measuring the draft between the baro damper and stove. ?

Try covering up the baro damper with aluminum foil and see how much the draft on the stove goes up or not? it should go up. make sure you have the weight on the baro damper on the correct side (vertical vs. horz. mounting).

if you power vent is running full, it should pull a good draft on the stove and then adjust the baro accordlingly for optimum draft at full burn.
Yes between stove and baro

I guess I never thought of this, could I just take it right out and adjust draft with my combustion fans? That's what I'm doing now but I would gain by eliminating the baro TEE. How would it react when it goes into idle fire?

I can't put a full burn on the boiler, currently I can overpower my power vent with opening the combustion fans too far


 
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SWPaDon
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Post by SWPaDon » Sun. Nov. 29, 2015 9:18 pm

Maybe I don't know what I'm talking about as I've never used a stoker or a boiler or a powervent, but when I see an 8 inch pipe, necked down to 6 inch using an end cap with a hole cut in it I get a little alarmed.

Your combustion blowers are forcing air right into that baffle between the 2 different sized pipes. That, I beieve will cause all kinds of back pressure in the flue system. Looking at it this way, I can understand the drop in your draft from .035 to .02.

Do you have a CO detector near the barometric damper? I would expect to see a reading there.

 
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Post by lzaharis » Sun. Nov. 29, 2015 11:58 pm

swyman wrote:Here is a pic of the best I can do with settings. I also noticed that as the fire got hotter my draft went down. I was .035 when I set everything this morning and now down to .02 but is not getting any moisture in the hopper so I may leave so I have a hotter fire? If I just run 1 burner wide open it does not have enough heat to maintain.
=========================================================================================================

At this point I would slow the feed rate on the two stokers and open the
air shutters on the combustion blowers where they recommend per
the picture in the LL manual as you appear to have too little air entering
the two stokers fire beds and too much coal feeding from what I can see of the image.

I would also try putting aluminum foil over the barometric damper as well.

What you need to tell us and the folks at LL is what the fire looks like-
1. how much raw coal is on the stoker bed-length of unburned coal on stoker bed before fire
a. how thick/deep the coal bed is as it is burning
2. how big the fire is in TOTAL length
a. how tall the fire is-it should be near the top of the firebox
3. how much ash there is on the stoker bed-length of ash bed on stoker

OK NOW

Raw coal length + burning coals length + ash bed length - you need to explain to Matt what the stoker bed looks like when its burning.

4. is there a regulating gate/coal flow control gate for both stokers to control
the feed rate of the coal entering the stoker fire beds?
If there is a pair of gates too regulate the flow of coal you may just need to lower
them and then open the air shutters to the recommended width to allow more combustion
air to enter the stoker beds.

Don't give up on the rice coal yet as your stoker needs to be adjusted.

 
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Post by swyman » Mon. Nov. 30, 2015 3:21 am

Iza, great post, those are some really good things I need to pay close attention to! I will put foil over the baro as soon as I get home from work, will be interesting but may be a temp fix. That is my biggest dilemma right now as I cannot open the air shutters anymore than what it is because the power vent won't pull enough draft. Hopefully the foil will cure this. This unit does have an adjustment on the shovels for coal flow. Here is a pic of my current flame, it's hard to see but flame is about 6-8" high. I know that is not enough because when I shut one burner down and run just 1 I can turn it up and WOW it will shoot a flame near the top just like you said. If I could get both to do it then I will have something! Maybe full burn rate will solve all my issues since it won't have to play catch up?

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Post by swyman » Mon. Nov. 30, 2015 9:02 am

Here are the numbers:
At boiler off the digital aquastat 161* ............. inside house 158*
off analog on boiler 140*
boiler return 118* ............. return to boiler inside house 130*

Before I called for heat the boiler was in idle mode at 185* on aquastat, 170* boiler analog, 166* at boiler return.

So I'm losing about 4-5* with everything at idle which is very good considering I will loose some off the 2 coils (1 house, 1 garage) plus exposed pipe at boiler. I get the temp gauges between the house and the boiler are all over the place but they are consistent with each other while running with each reading in the 20's of temp loss if you read both sets of analog gauges. I did put foil over the baro but still could not open the blower gates hardly at all staying within .03-.04 on manometer. My ashes are about 1 1/2"-2" from falling into ash pan, ash/coal is about 1 1/2" deep. Burning/glowing area is about 2 1-2" to 3" long and flames are around 6" high.
During this run I dropped 20* in boiler temp (didn't keep track of time) maybe 8-9 minutes. When I turned thermostat in house down I noticed how rapidly the boiler started to climb. This is a sign of hope seeing that I am only running this thing about half of what it can do. So now I wait for Matt to return my call so we can move forward on what to do with this direct vent????

Thoughts, comments please!

 
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Post by lzaharis » Mon. Nov. 30, 2015 10:12 am

Slow the feed rate of the stokers down to the minimum then wait an hour or two for it to catch up.

 
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Post by swyman » Mon. Nov. 30, 2015 8:22 pm

lzaharis wrote:Slow the feed rate of the stokers down to the minimum then wait an hour or two for it to catch up.
I thought ideally you want the hot coals about a inch or so away from falling into ash pan?


 
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Post by KLook » Mon. Nov. 30, 2015 8:57 pm

Your combustion blowers are forcing air right into that baffle between the 2 different sized pipes. That, I beieve will cause all kinds of back pressure in the flue system. Looking at it this way, I can understand the drop in your draft from .035 to .02.
He is pulling on the firebox, that is the issue. He is using a power vent sold by LL to handle all the combustion blowers will put out.

How about that power vent? I had one once and it could be shut down on the outside to prevent backflow of air to blow out a pilot light. I installed my bro in laws Pioneer from LL, before they bought the company, and it was power vented. I do not remeber how it handled the backflo issue. Could it be not running at maximum velocity because of settings?

Kevin

 
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Post by SWPaDon » Mon. Nov. 30, 2015 9:28 pm

KLook wrote:
Your combustion blowers are forcing air right into that baffle between the 2 different sized pipes. That, I beieve will cause all kinds of back pressure in the flue system. Looking at it this way, I can understand the drop in your draft from .035 to .02.
He is pulling on the firebox, that is the issue. He is using a power vent sold by LL to handle all the combustion blowers will put out.

How about that power vent? I had one once and it could be shut down on the outside to prevent backflow of air to blow out a pilot light. I installed my bro in laws Pioneer from LL, before they bought the company, and it was power vented. I do not remeber how it handled the backflo issue. Could it be not running at maximum velocity because of settings?

Kevin
In other posts, it is shown that the furnaces combustion blowers are putting out more air that the power vent can handle. Not to mention that the flue is necked down from 8 inch to 6 inch. That neckdown is immediate, with no tapered conversion to condense the airflow.

I'm looking at this from a car exhaust standpoint. If you take a car, that is designed for a 2.5 inch exhaust and throw on a 1.5 inch exhaust system, bad things will happen quickly. First is going to be a severe loss of power, which is what we see with this furnace. Second will be the increase in fuel usage, which we see with this furnace. Third on a car, will be blown gaskets trying to unload the pressure from the system.

Or maybe I'm way off base.

 
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Post by KLook » Mon. Nov. 30, 2015 9:40 pm

A car is all push.....his power vent is that necked down area and is pulling.

Kevin

 
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Post by SWPaDon » Mon. Nov. 30, 2015 9:47 pm

KLook wrote:A car is all push.....his power vent is that necked down area and is pulling.

Kevin
That's the part I've been trying to explain..........his 2 combustion blowers are pushing and the powervent is only able to pull the air from one of them effectively.

His furnace is a twin stoker.

 
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Post by KLook » Mon. Nov. 30, 2015 9:52 pm

But it was a combination sold to him my LL. They usually get it right. I was suggesting that something is wrong with the vent also.
Just not the pipe, but maybe he got the wrong vent.
Kevin

 
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Post by SWPaDon » Mon. Nov. 30, 2015 9:58 pm

KLook wrote:But it was a combination sold to him my LL. They usually get it right. I was suggesting that something is wrong with the vent also.
Just not the pipe, but maybe he got the wrong vent.
Kevin
That is possible.

I'm not keen on the 8 to 6 inch conversion. I don't see where a fan big enough to pull the amount of airflow needed for the 8 inch pipe and dual stoker, could be shoved into a 6 inch pipe. :confused:

 
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Post by KLook » Mon. Nov. 30, 2015 10:26 pm

The combustion fans are low cfm's, just enough to fire up the coal. The vent is much more about volume so it doesnt produce a lot of suction and just pull air in by the combustion blowers. It is a balancing act for sure and something is not doing its job.

Kevin

 
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Post by swyman » Mon. Nov. 30, 2015 11:25 pm

Yes you guys are exactly right, the direct vent will not pull enough exhaust out for me to maintain the correct draft. I cannot open the combustion blower doors even half way. I cannot believe that this setup will not support the boiler as this was a package deal through the company. I did not get a call back from LL all day so maybe they are out of town? At this point I think it will be best if I just install a chimney and I hope they give me my money back from the direct vent. Another thing I don't like about the direct vent is it is always running wide open. That pulls a lot of air out of the room when the boiler is in idle fire. The baro door is wide open and still immediately pegs the manometer. Hope I can talk to Matt in the morning. Burned another 4 bags last 24hrs with temps in the 30's.


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