Too Much Heat With My Coal Stoker

 
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ewstuart
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Stoker Coal Boiler: AHS S130

Post by ewstuart » Mon. Dec. 15, 2008 9:53 pm

Installed a new AHS S-130 in my NH home last month and I’d like to know how to best address the problems I am experiencing. I have a good fire (although my stack temperature runs cool only reaching about 200-250 deg F on long cycles into a 8”x12” clay lined 26’ tall chimney) and the unit seems to be runing well now that I have addressed a few issues. I purchased the unit new this summer with the fan belt drive, thermo-ash monitoring control and the 5 gpm DHW coil (that I am not using yet because I have my hot water on a dedicated indirect zone). I changed my piping layout and switched from one small circulator (Taco 007) pushing water through my Weil McLain oil fired boiler and feeding 4 zone valves to utilizing a Taco 6 zone relay panel with independent zone circulators and a primary circulator as described in the attached .ppt drawing. I have a barometric damper set up to open slightly when the fan is running but will properly adjust it after I set up the Dwyer model 215 manometer which I just purchased used. When I first started the unit I found that my ash grate was not dumping ash although the motor was running. As it turned out, the unit came without the Woodruff key installed on the motor shaft and the upper sprocket was also not secured to the ash grate lever shaft (thanks AHS). I also learned that I did not have enough make-up air coming into the basement where the boiler is located as I drove up my CO level. For now, I just have a small basement window open which draws sufficient air into the space to replenish what is going up the stack. I’m starting to think about what I should do to permanently duct outside air into this space. I wish the AHS unit had an air inlet connection that I could directly hook up to like my oil boiler but it does not. I am open to suggestions on what others have done to address this issue.

My main problem, however, is that I am heating my house too much. On mild days, (~40 deg F or higher) I turn off my zones and have to throttle my supply valves significantly so that I am not pushing too much heat (and thus utilizing more coal than I need to) up to my living spaces. The second floor of my house especially gets too much convection heat. My return lines are not overly hot to the touch but the supply lines are hot (not insulated yet) as the circulating pump used to keep the water flowing through the idle oil boiler (where my aquastat is located) and to maintain correct temperature in the stoker seems to output enough pressure to overcome the wimpy check valve that is integral to the circ pumps my heating guy installed. I know that correctly sizing the pump is best practice but I was letting him decide what pumps to use and when I told him that I wanted check valves in the line he assumed that the integral pump check valves were sufficient enough. I now think differently. He installed Grundfos UPS15-58FC 3 speed pumps and I have them set to their lowest speed but it seems that this is still too much flow in the main line. I am contemplating installing a rheostat to slow down the pump speed on the main pump or to just bit the bullet and purchase a smaller pump with at least half the flow rate. I just don’t know if there is too much restriction in trying to push water through the oil boiler in the opposite direction for which it was intended (again see drawing). I am also thinking about replacing the check valve springs in the zone pump outlets with a stiffer (k) spring to deter the flow in the correct zone direction when the zone is not calling for heat.

I tried to expain this as best I could but I am sure there may be questions for those who might have the experience or know-how on what I could do in this situation. Appreaciate any input the gurus here might be able to teach this ambitious home owner.

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Yanche
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Post by Yanche » Mon. Dec. 15, 2008 11:28 pm

The first test I would try would be to close the return zone valves. This will surely stop any flow. If the house cools to your liking then the problem might be thermal gravity induced flow that as you say lifts the pumps checks valves. I wouldn't change any pumps, at least not yet. If the test indicates it is a gravity flow problem, use the any of your three valves in each zone to throttle back the flow. You should be able to reach a point where the check valve stays closed when the pump is off. Hopefully the flow will still be sufficient when the pump is on to get enough BTU's into the zone.

I don't see a need to run the boiler to boiler circulator all the time especially since you have an indirect domestic hot water heater. I have my zone controls also trigger a running of my common pump. Basically a logic OR, if any zone is on the common pump is also on.

Depending on how your zone returns are piped you may need check valves on each zone return before the header. The zone return need a drop down thermal break or a check valve. The type needed weighted, swing or spring depends on where it is located.

Have you considered primary secondary piping for your boilers? They add an additional pump but make the operation of each boiler truly independent.

 
jmmazzy
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Post by jmmazzy » Tue. Dec. 16, 2008 2:10 pm

Easy fix, your circulator with the check is in the wrong location and some minor piping needs to be done. A check valve only stops backflow and your circ. wants to pump to the easiest path of flow just like electricity in the direction of the easist path which are your zones which may have 20 gal. of water compared to your boilers which might have 50 gal. I will get back with a drawing shortly.

Mazzy

 
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ewstuart
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Stoker Coal Boiler: AHS S130

Post by ewstuart » Tue. Dec. 16, 2008 3:15 pm

Hi Yanche, by throttling the supply valves I can moderate the unwanted flow going up to my radiant zones but also it definitely stops flow if I shut the return zone valves. So I am getting too much thermal gravity flow. I was hoping that I could find a different solution other than maintaining this method as I don't want to restrict the flow to the pumps when there is a call for heat as I am afraid that I will end up cavitating or overheating/damaging my zone pumps.

I also tried wiring up my constant on circ pump to energize only when the unit drops below setpoint temperature (which I have set at 170 deg) and the fan turns on. But this caused the loop temperature to drop too much (outside the stagnant water surrounding the fire) and it took too long for the system to return/recover and adequately heat the zones. I also experienced quite a few puff-backs doing this so I went back to the method recommended by AHS which is having the constant flow as I attached above.

I don't know what setting up the piping as a primary or secondary would buy me. Do you have a diagram or layout that you could forward that you would recommend or describe it?

 
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ewstuart
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Post by ewstuart » Tue. Dec. 16, 2008 3:35 pm

Hi Mazzy, I realize that the check integral to the pumps only prevent flow in the opposite direction. I did take a few of the check valves out of the pumps and pulled them apart to see if there was any foreign objects affecting the seating. I found that the spring that holds the valve shut is very light and thus any amount of differtial pressure would be enough to lift it and allow flow in the intended direction which I imagine is ideal for most applications. I'm trying to maintain the flow/temperature in my supply line but not so much that I am forcing flow through the zone pumps up to the zones which are not calling for heat. I thought that most of the flow would circulate through the idle oil boiler when there was no call for heat but between thermal gravity flow and open path flow through the zones which may be less restrictive than the idle boiler I'm heating the radiant house zones too much. I'll look for your drawing post. Thanks.

 
jmmazzy
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Post by jmmazzy » Tue. Dec. 16, 2008 4:09 pm

ewstuart, pumps have a head pressure and a flow rate and want to do there job. Yes the springs are very light and this is not the promblem. Putting in a primary loop will solve the differtial promblem. I have an ahs 130 and find no need to run my system in series so the sketch showes par. and series which would not be a big deal in your case. I have installed many systems (see drawing) this way and never had a promblem. What size supply and return piping do you have?

Mazzy

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beatle78
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Post by beatle78 » Tue. Dec. 16, 2008 4:35 pm

I went through something similar this week. I have 2 boilers and they are plumbed in parallel similar to yours except I have a pump on each boiler.

I needed to connect the supply pipe after the #1 zone down to the return to give a complete loop (not through the oil boiler). This should work b/c you zoned with circulators like I did. The zone circulators will pull the necessary hot water from the primary loop. Without the primary loop completed the force from the boiler pump is pushing water through the flow checks in the zone circulators. (if you/I zoned with zone valves we wouldn't have this issue)

A simpler thing to do would be to slightly close the ball valve after the circulator pump to create less pressure in the system. This could solve your problem and cost you no money. It will take some tweaking though.


 
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Freddy
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Post by Freddy » Tue. Dec. 16, 2008 5:10 pm

Gosh, except that you have more zones, your post could have been written by my buddy that installed his ASH130 about 4 weeks ago. The asher sprocket was loose and wouldn't ash. Easy fix, but thought it odd it got past quality control....and now... two? (we didn't check the woodruff key on the motor as it was only slipping on the top sprocket. Maybe he should!) We fired it up on a Sat afternoon. All seemed fine. The next morning he woke to the entire house at about 85*. The pump that runs 24/7 between the AHS and his oil boiler was pushing open the flo checlks on all his zones. The cure was fast, simple, and free. He did as Beetle just mentioned, twisted the valve at that pump and throttled it down. It took two tries to get it right, but now he get's zero over ride and it works fine.

 
jmmazzy
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Post by jmmazzy » Tue. Dec. 16, 2008 9:56 pm

I hope it works for your friend, Good luck

Mazzy

 
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Post by ewstuart » Wed. Dec. 17, 2008 12:21 pm

Hi Mazzy, Thanks for the drawing layout. Something to consider, although I hate to break into the piping again this winter. I will consider this. I am using 1.25" supply and return piping on the headers and all the way up to the boilers for the most part where I have a 1.5 to 1.25 reducer (some black pipe, some copper).

Right now I am throttling the outlet side of the constant on circ pump as Beatle78 and Freddy mentioned above and that seems to be working although I have yet to run long enough to determine if it could be a long term fix or if its something I have to keep tweaking based on outside temp. Is there any possibility of shortening the lifetime of the pump by doing this? Is connecting a rheostat to the pump and slowing it down electrically another viable option? I also like Beatle78's suggestion of connecting my supply header cap-off to the return header cap-off to complete the loop. I actually thought about doing this already but thought that I would not get enough flow through my oil boiler and its aquastat to give me an accurate temperature reading and this might affect the overall operation. I may do this in copper so I can insert a check valve and isolation valve to that line.

Regarding my situation with the ash grate. I was also surprised it made it through quality control and now even more surprised reading about another case. I was also dissapointed from the lack of AHS's timely response to rectify the situation since I could not find the right size Woodruff key in my area (had to use a temporary solution for a while). But all's well now.

 
ART52
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Post by ART52 » Wed. Dec. 17, 2008 12:58 pm

Hello ewstuart
I would suggest you turn off constant circulator, and also turn off the oil boiler supply if there is a valve available. or if there is a valve on the outlet side of the oil boiler turn it off. but to not turn both off. disconnect the oil burner . nothing else except the burner.
I do not know what you're circumstances are or if you are keeping oil boiler for a back up this may not be the right thing to do.
I have been running A coal stoker over 50 years the only back up that I ever needed was a generator for power out .
Art52

 
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beatle78
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Post by beatle78 » Wed. Dec. 17, 2008 1:33 pm

ART52 wrote:Hello ewstuart
I have been running A coal stoker over 50 years the only back up that I ever needed was a generator for power out .
Art52
:shock: :shock: :shock: WOW! Art that's awesome!!!!

Art,

So you use coal heat/hot water exclusively?

That is AWESOME!!!

 
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coal berner
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Post by coal berner » Wed. Dec. 17, 2008 1:42 pm

beatle78 wrote:
ART52 wrote:Hello ewstuart
I have been running A coal stoker over 50 years the only back up that I ever needed was a generator for power out .
Art52
:shock: :shock: :shock: WOW! Art that's awesome!!!!

Art,

So you use coal heat/hot water exclusively?

That is AWESOME!!!
Nothing New about that if you are from the Coal Region. At one time everyone heated with Anthracite in and around the Coal Region ;)

 
jmmazzy
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Post by jmmazzy » Wed. Dec. 17, 2008 1:49 pm

ewstuart, I totaly agree with art52 and I would go that way until summer. You don't need to run in series w/oil boiler, I don't. and I have a large system (11 zones) and with the piping dia. I posted and it is piped just like that to switch over from coal to oil I only have to open one valve and close one, switch power off on coal and on for oil and thats it.

Getting back to your questions, throttling shouldn't harm the circ. and using a rheostat is not a promblem,I have installed viable speed systems using taco 007's with no promblems, and yes beatle78's suggestion to install a byepass equalizing line is a good one, I'd do it with at least a 1" line.

Again I would go with art52 suggestion for the season.

Mazzy

 
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coal berner
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Post by coal berner » Wed. Dec. 17, 2008 1:57 pm

ART52 wrote:Hello ewstuart
I would suggest you turn off constant circulator, and also turn off the oil boiler supply if there is a valve available. or if there is a valve on the outlet side of the oil boiler turn it off. but to not turn both off. disconnect the oil burner . nothing else except the burner.
I do not know what you're circumstances are or if you are keeping oil boiler for a back up this may not be the right thing to do.
I have been running A coal stoker over 50 years the only back up that I ever needed was a generator for power out .
Art52
Art I Notice in your avatar you had a EFM 46 years And now a Keystoker Do you still have the EFM and would you like to
sell it :?: if so PM me


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