AA130 - Circ Pump Question...

 
mikeandgerry
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Post by mikeandgerry » Thu. Jan. 01, 2009 1:52 pm

Good News.

I had some time to review your friction loss. I found a friction loss chart for pex at http://plomberie.per.free.fr/Documents/PPFA%20200 ... ndbook.pdf. I was using a chart for "plastic pipe", i.e. unknown type. Although, I don't know if pex-al-pex is signigicantly different as far as friction loss goes.

I also used the hazen-williams calculator on engineeringtoolbox.com. It looks like your friction loss in the piping is about 23 ft., not the 30 ft that I suggested earlier. Your taco 011 is working fine which would confirm that figure. http://www.houseneeds.com/shop/HeatingProducts/Hy ... Curves.htm

Also, the best news, is that your system will flow about 10-11 gpm which will allow you to deliver the maximum capacity of the anthratube through that pipe!

Woohoo! I was worried for you earlier that the pipe was too small. Actually, 1-1/4" would have been a better choice. It would have saved electricity and pump replacements but I think changing that now would be cost prohibitive.

Good luck and Happy New Year


 
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OldAA130
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Post by OldAA130 » Thu. Jan. 01, 2009 8:47 pm

MikeandGerry wrote:
Woohoo! I was worried for you earlier that the pipe was too small. Actually, 1-1/4" would have been a better choice. It would have saved electricity and pump replacements but I think changing that now would be cost prohibitive.


This whole episode has been just gut wrenching from start to finish. When I saw your earlier post I started having flashbacks of my wife on the back porch waving her fist at me as I tore up the back yard with a backhoe. I never win the lottery but I thought about playing tomorrow because I feel pretty lucky today not having to change tubing. Thank you for the information you provided. I hated to buy another pump ($300 with the valves and fittings) but I don't think the 0009 would've made it through the end of the week. She was running extremely hot and turning the green paint brown. I've heard once you let the smoke out of a motor it's real hard to put it back in.

Flyer5 wrote:
Do you have good drainage under the corigated pipe or could the ditch be filled with water ?


No drainage under the corrogated drain line. I'm not too concerned about it though. The ditch is sloped all the way to the basement... :cry:
I am beginning to see the effectiveness of the insulation I used. With the AA holding around 190deg, the temp gauge on the oil boiler is holding just over 185deg. I don't think that's too bad (about 4deg loss). I expect some temp drop due to the lines being next to each other in insulation for 150'.

I talked to a fella today who used windshield washer fluid in his system mixed 50/50 with water. At 20% the cost of glycol it made the decision easy for him. He was not aware of the heat trasfer comparison to straight water though. I guess if a line splits you can throw heat transfer out the window. I'm real close to going glycol. I'm still experiencing coal feed issues.

 
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Post by Flyer5 » Thu. Jan. 01, 2009 9:43 pm

I was worried there was water at the bottom of the ditch around the pipe ,that will suck a lot of heat out . But 4 degrees is great for the distance . I have heard of people using RV antifreeze as well probably safer than ww fluid which contains alcohol .

 
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Post by Freddy » Thu. Jan. 01, 2009 11:16 pm

The coal feed issue.... maybe the coal is damp & is freezing, causing bridging? I assume that you're burning pea size? What brand is it? AA sells an "agitator" that is driven off the gear on the end of the shaker shaft. It has a rod that goes to the end of the auger in the bin & tickles the coal. They say it is seldom needed, but if the coal is particularly ugly it'll keep it from bridging. Of course it won't help if it's frozen.
When someone says that antifreeze is less efficient, they don't mean it takes more fuel, they just mean it doesn't transfer heat as quickly.
As for shutting it down if the fire goes out, consider a heat sensor in the stove pipe. The air will change temp faster than the water. Here's a pic of a hot air furnace switch that would work.

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mikeandgerry
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Post by mikeandgerry » Fri. Jan. 02, 2009 1:28 am

OldAA130 wrote:This whole episode has been just gut wrenching from start to finish. When I saw your earlier post I started having flashbacks of my wife on the back porch waving her fist at me as I tore up the back yard with a backhoe.

I am beginning to see the effectiveness of the insulation I used. With the AA holding around 190deg, the temp gauge on the oil boiler is holding just over 185deg. I don't think that's too bad (about 4deg loss). I expect some temp drop due to the lines being next to each other in insulation for 150'.

I talked to a fella today who used windshield washer fluid in his system mixed 50/50 with water. At 20% the cost of glycol it made the decision easy for him. He was not aware of the heat trasfer comparison to straight water though. I guess if a line splits you can throw heat transfer out the window. I'm real close to going glycol. I'm still experiencing coal feed issues.
Sorry to have scared you and...I know that the fear of the wifey is always greater than the fear of failure ! I am truly happy for your outcome.

With that minimal heat loss everything is dry and snug in the ground. Of course, then again, 190 degree water is hard to cool down!

As for antifreeze, if your depth is greater than 3 ft in Pa, you have little to worry about. If you are just under the surface you should have a hefty concentration. This web site has some great charts:

http://www.engineeringtoolbox.com/propylene-glyco ... d_363.html

Don't use ethylene glycol or RV antifreeze or windshield washer. Spend the cash and get the boiler type propylene glycol.

A 40/60 mix of propylene glycol to water will give you about 10% reduced heat carrying capacity. Your Axeman has an output of 113k btu/h so it is reduced to 102 kbtu/h. Your boiling point will be raised to 219 (at sea level pressures, higher in your closed boiler). The freeze point would be -8 degF.

A 50/50 mix yields -29 degF freeze point, 222 boiling pt, and 15% reduction in heat carrying capacity.
Last edited by mikeandgerry on Fri. Jan. 02, 2009 1:41 pm, edited 1 time in total.

 
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Post by Freddy » Fri. Jan. 02, 2009 6:03 am

One other thing, does the pump run 24/7? The reason I ask is that if it doesn't then the AA can easily get it's temperature up to 200....210...220. At some point we start to worry about Pex failure. Your Pex is rated at 190 (mine only 180). I spoke with the manufacturer and quizzed them pretty hard. They said it's not only the temp above the rating that can cause the failure, but the time it stays at the high temp. Of course he had to say "never go over 180" to me, but did say there is a certain amount of leeway. Time wise he thought 8 minutes was the magic number. After 8 minutes the tubing has come to the same temp as the water in it. As for how much over 180 (190 in your case) it could maintain, he wouldn't say, but when I pressed him, he cringed at 20 degrees over & thought there would be failure. I added mixing valves in the boiler room so my Pex will never see over 180. It works fine for me, but the water temp to the pipes actually rarely goes over 170.

 
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OldAA130
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Post by OldAA130 » Fri. Jan. 02, 2009 12:16 pm

The fire was out again this morning... I shut the unit down and drained. I also called Berverly at AA and order the parts for the agitator.

I was also concerned about the tubing and pressure/temp ratings this morning. I checked the spec sheet again for pex-al-pex and here's what I found.
From the Zurn Pex-al-Pex spec sheet: "Temperature and pressure ratings shall be 200 PSI at 73°F, 125 PSI at 180°F, and 100 PSI at 200°F."
I called as well and talked to tech support. The temp points listed are the ASTM required points for this type of tubing. Zurn does not test at any other point. I asked if there was a point where at a certain temperature the working pressure of the tubing just drops off. The answer was officially, "use the ratings in the specification sheet". Unofficially, the pressure rating would drop off gradually with increased temp but there was strong sentiment against operating for long periods of time above 210deg.

A couple other things... the main circ pump operates 24/7 and with the two boilers tied together and the new larger pump installed the variation of the temp in the AA has slowed a bit (likely due to the increased flow). I have not yet installed the heat runs in the shop (source of the freeze worries) but when I do I will use this as my heat dump. The Pex is tied in after this heat run branches off so I could divert the hottest water away from the pex tubing. I should look into this in the short term but with out freeze protection I cannot. I will be looking into freeze protection before bringing the unit back online.

Something else... I burried an 8-conductor cable and t/c cables from house to shop with the intent of bringing signals into the house such as overtemp conditions. I have added a water temp switch set at 220f to one of the empty ports in the top of the boiler and plan to put an audible in the house. Now I will use the flue temp switch (good idea Freddy!) to watch for fire out conditions with an audible. Some other plans... I scarfed a 8-input digital chart recorder out of the trash at work a few years back. I will use this to trend inputs such as water temp, ash temp, when the unit is firing and ashing. I also want to install a proximity sensor to sense coal in the transfer head to let me know when the feed system is getting behind. (all current needs but future work...) Trending this information will allow me to tune the unit to maximize heat rate.

Wow, we've covered a lot of ground with this thread! I really appreciate all of your input and tech web sites etc. I am learning a great deal!

Tom


 
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Post by mikeandgerry » Fri. Jan. 02, 2009 2:01 pm

OldAA130 wrote:The fire was out again this morning... I shut the unit down and drained. I also called Berverly at AA and order the parts for the agitator.

I was also concerned about the tubing and pressure/temp ratings this morning. I checked the spec sheet again for pex-al-pex and here's what I found.

Tom
Your coal bin is outside....I assume it is covered. It cannot be wet coal. The anthratube only likes dry coal. Without that agitator it simply will not feed wet coal. What happens is that the fines collect near the pickup area and turn to a paste that prevents the peas from entering the tube.

Even with the agitator, it won't feed frozen coal. Your bridging problem may not be solved by the agitator. When coal is placed in an unheated bin and not given time to dry it may be a continual problem. Fill your bin in the spring and allow it to air dry. It would be better to put the bin indoors or close in the bin and allow the air to "communicate" with the boiler. Or.....heat the bin with a loop!

Take heed of Freddy's advice on the pex. I have no experience with that but it does have a limitation that the AA can flirt with easily. I see a mixing valve in your future!

 
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Post by Freddy » Fri. Jan. 02, 2009 3:38 pm

oops.. Double post, deleted this one.
Last edited by Freddy on Fri. Jan. 02, 2009 3:40 pm, edited 1 time in total.

 
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Post by Freddy » Fri. Jan. 02, 2009 3:39 pm

What's the price of the agitator? Just curious. I got one by saying "I do", but she doesn't help much with the coal. ;)

I'm not sure how I'd create a way to tell if coal is reaching the head. It does NOT stay full as you might think. Sometimes it does fill, but often the feed tube that goes from the head to the fire pot will only be partially full. They designed it pretty close, it truly only delivers the amount of coal needed. Sometimes it's a close call and the tube get's close to empty, other times it catches up and the tube will be full to the top.
Let's say the fan just shut off. Now the fan is not running, the coal continues to burn and as it burns, it settles. The coal in the tube falls down to take up that space, but the auger is not turning. If it's a warm day & the boiler only runs it's one minute per hour, by the time it gets a call for heat and the auger runs for a while, the tube can be close to empty. A proximity switch might show it empty when actually it's just doing it's normal thing.
You know how they say if it's full and augers extra, that the extra just goes down the center of the auger? Well, I've opened mine several times and have never once caught it FULL, at least not to the point it's dropping back down the center of the auger.

 
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Post by mikeandgerry » Sat. Jan. 03, 2009 2:55 am

Yes, the total cost of an agitator is quite high but there are a few benefits too. :D

Freddy, have you been sitting next to the anthratube with the coal head cover off, a beer in one hand, and the site tube cover in the other.....again ?!?

I know I have been....just curious if there were others doing it. :D

 
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Post by Freddy » Sat. Jan. 03, 2009 6:57 am

The people that have missed the two hour movie "Auger" just haven't lived. I can watch it over & over. Here's a snapshot of the opening scene. :)

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Post by whistlenut » Sat. Jan. 03, 2009 8:44 am

I used to have the bridging problem many years ago, especially with a winter delivery and we had to refill the 9 ton coal bins.Yes, it flows from the truck, but freezes quickly when inside. I did the agitator thing and while helping in the short term, I decided to just add a heat loop under the bin using return water. There hasn't been a feed issue in 29 years now, so perhaps that will give you some perspective. The need for more mechanical things like an agitator adds more complexity to service, especially since you need to get to the doghouse to install it. Bet your bin won't empty easily this time of year. If you have means of adding some form of heat to the bin area, try that first. Even with the many years of experience on the forum, sometimes no simple answers come forth. I like the KISS philosophy. The reason truck bodies, truck fuel tanks and lines are heated is a no brainer. I also know that the operational temps of pex al pex, and fostapex are safe below 200 degrees. An overshooting (runaway) boiler pumping out 240 degree water isn't safe for anyone. I have an EFM 900 heating an 82' by 130' with 22" ceilings using a 5 zone primary-secondary with a radiant floor. There are nearly 2 miles of 300' loops and the primary runs at 180 degrees and the secondary's at 130 max. Using Taco 008R's as our means of circulation, however you need to overcome height and friction issues we don't. My vote is to try to get some heat under the bin as a first response. I don't like outfires either. Insulate the area you are going to heat and you will not even see any additional demand. PS: use only antifreeze designed for hydronic heating systems. It is safe. Not a good place to save a few bucks.

 
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Post by LsFarm » Sat. Jan. 03, 2009 9:33 am

I have to laugh, as I was reading through this thread, and read about outfires I was thinking about suggesting what whistlenut posted above: heat the coal bin.
My coal bin has some heat by accident, my Pex-al-Pex pipe runs through the coal hopper, so it does tend to keep the coal warm.. just an accidental plus of the design. However. if the fines accumulate at the bottom of my hopper I can see that the fines could block the feeding of coal to the end of the auger..

OldAA130: take a look at the end of the auger, is the end of the flighting worn or bent in?? Mine was, I just used a cressent wrench and bent the last 1" out a bit so it could 'rake' the coal as the tube rotated.. If the end of the flighing is bent in or worn away, there is no aggitation of the coal, and ONLY gravity will feed the auger..

You could make an electrical aggitator cheaper than the AA agitator. Find an old, slow electic drill, 1/2" chuck, and make an aggitator with a lenght of 1/2" steel rod, with a bend in the end, or make a tee on the end, or any form of a hook to stirr up the coall. Theis aggitator rod would be like a heavy-duty paint stirrer. Set up the drill motor in a jig to hold it in place, and use a timer to run it for a minute an hour. It should keep the coal moving.. The AA agitator is a gear-driven version of what I describe, the gear is on the end of the notched gear that moves the ashing grate . The parts from AA are not cheap..

PM Matthaus, he may have a agitator from one of his AA rebuilds.

For the benefit of the other AA owners, could you start another thread on the topic of: AA boiler Outfires,, coal feed problems... I think you will get more responses as well.

Greg L

 
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Post by Freddy » Sat. Jan. 03, 2009 11:16 am

Are the AA agitators expensive? I have no idea, my gut says $100, but from the sound of things they must be much more. If one had just the gear to mate to the ash gear, the rest could be home made easily I'd think. The electric drill idea is good.
My bin is insulated and heated. I didn't have freezing coal in mind at all. I did it to keep frost from lifting the slab. It seems I accidentally did something right!


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