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[dwneast77]

I think I'm looking at adding a 30 or maybe even a 50 plate exchanger to my system.  Long story short, if possible, I have 2 OWBs plumbed together.  The problem I have is that I have a hard time keeping the water level between the two equalized.  One boiler or the other may and sometimes do overflow.  I have a constant balancing act to keep them within reasonable levels.  Both have 0014 Taco pumps.  Last year I had them both pushing water direct to my main manifold (two hot supplies, and two returns, one of each to each boiler).  Worked ok that way.  This year, I still have that option, but I changed the piping a little so that I can run the boilers in a series.  Hot water comes from boiler A to manifold, Cold returns to boiler B.  Hot from boiler B goes into cold return of Boiler A to complete the circle.  I've even gone so far as to connect a hose to the drains of each boiler to act as an equalizer line, which does help, but not enough. 

The 2 boilers have been holding pretty well equalized for the last couple of days, but today my family and I wanted to spend the afternoon at my parents.  At this time I only have one boiler burning, the CB E2300.  For some reason, and this is somewhat common, the boiler did not start gassifying for a cycle and it began losing water temp.  Fortunately I have a camera aimed at the guage so I can monitor it via the internet.  I knew there was a problem.  I drove home, thought I got things going good and went back to my parents.  I monitored and found that it began losing temp again.  We stayed for dinner, knowing that the oil burner would kick in and keep my plants alive (1 greenhouse running so far).  Upon arriving home, water temp down to 152, I noticed that the ground was very wet.  I also heard some air bubbles moving through my manifolds.  The water sight guage on the CB was at a good level, but apparently a lot of water from the other boiler had overflowed the CB. 

I'm open to suggestions.  There are a lot of smart guys out here.  But I'm thinking a plate exchanger between the two boilers is my best option.  Anybody know where I can get a reasonable price on a bigger plate exchanger??  I was thinking the bigger the better so my thought is on a 50??  CB boiler is rated at 170K btu.  Wood Doctor is rated at 280K btu.  I want as much heat transfer as possible. 

Thanks for any input in advance.

Jeff

[RSI]

Why are you running in series instead of parallel?
How close do you want the temperature to be between the two sides of the plate? It is normal to see 20 degrees less on the secondary side.

From what you have described, I am thinking you will be putting the plate on the second boiler with a pump pushing water through the plate and right back in and the water from the other boiler flowing through the other side? That should work fine and you would probably want to use a 007 pump on the short loop.

I would probably go with at least a 60 plate. It would be about $350.

[dwneast77]

It's hard to explain my current setup and a picture is even confusing.  This is a quick sketch I drew for my dad this evening to give an idea of what I have in mind.

I asked my CB dealer about it at the time and he spoke with a guy at the factory about it and they suggested running in series last year.  I chose to run parrallel last year with both boiler feeding direct to my manifold.  This year I added the option to run in series to give it a try.  I did attach a picture of my manifold, but it is from last year before I changed the piping to have the series option.

My thought is that my sketch is actually a bad idea, but rather I need to tie into the return (left) end of the bottom manifold to get all the water flowing through the plate.  Then have the water from the Wood Doctor flow through the other side of the plate and back to itself.  There is already a 0014 pump in place so there will be plenty of supply water and the pump supplying the manifold is also a 0014. 

As you look at that picture (to clarify), the 2 hot lines are come up the left side to the top manifold, flows accross to the other side to a wrap-around pipe down to the return manifold and back to each boiler from the bottom manifold.  I did a strange thing by using twin 1" lines when I added the Wood Doctor.  If I did my math correctly (and I'm no expert) 2 - 1" lines has a slightly higher capacity than 1 - 1 1/4" line, so I thought I would be safe that way.   And it was a lot cheaper and faster than ordering the 1 1/4" line. 

$350 seems pretty reasonable for a 60 plate.  What is the BTU rating on it?? just out of curiosity.  And dimensions??


Thank you very much for your input.

Jeff

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[RSI]

Ok, so you have two sets of insulated lines going to the building? Do you need both or would one handle it? Are the two boilers close together?

[dwneast77]

First of all, please disregard my mess, I'm in the process of cleaning things up.  Here is a new picture of my lines.  This shows 2 main hot lines (one from each boiler) coming in to the top manifold, and 2 main return lines coming out of the bottom manifold on the left end.   My latest thought would be to isolate the Wood Doctor boiler from the Central Boiler.  Central Boiler is the primary and those pipes would not be changed.  But I think I would disconnect the Wood Doctor pipes (which are the ones coming out the front of each manifold and tie in the HX there to the return line of the Central Boiler underneath the thermostatic valve.  That would ensure that the thermostatic valve would not interfere with heat exchange from the Wood Doctor if the water temp should drop that low in the CB.

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[RSI]

If it were mine, I would probably just run supply/return pipe from one boiler to the other so they stay mixed and then parallel the pipes so it all comes from the same place and returns to the same place. I am not sure if that would still cause a problem with the overflow but I would think it should work.

[dwneast77]

I would think that if I did it that way, I would have to pump from boiler A to boiler B and then have another pump pushing water from boiler B to boiler A.  Any time that I shut the pump off on one boiler, within seconds, that boiler is overflowing because it is not pushing any water out but return water is coming in.  And this happens in either direction.  If I shut off the pump on boiler A then boiler A over flows and the same if I shut off boiler B pump, boiler B overflows.  So right now, if I do shut a pump off I have to very quickly close the valves on the supply/return lines and isolate it.

[dwneast77]

Another important thought,....  If one pump fails, that boiler would overflow quickly leaving the other boiler with the working pump at dangerously low water levels, which could in turn burn out the second pump.  Central Boiler has low water float switch, but it is currently disabled because it failed and has not yet been replaced.  Wood Doctor has no low water float switch.  Maybe I can figure out a way to fix that.  In any event, I think the smartest thing to do is isolate the boilers.  As long as I get sufficient heat transfer between the two via plate exchanger I'm happy and things are safer. 

[Scott7m]

 I like the idea of the plate exchanger myself, my buddy has a woodmaster pellet burner outside, and a elite 200 inside, when he leaves and the water temp drops from the elite 200 the pellet stove takes right back over.  Of course your situation is different, but I think the principle will work

[RSI]

Another important thought,....  If one pump fails, that boiler would overflow quickly leaving the other boiler with the working pump at dangerously low water levels, which could in turn burn out the second pump.  Central Boiler has low water float switch, but it is currently disabled because it failed and has not yet been replaced.  Wood Doctor has no low water float switch.  Maybe I can figure out a way to fix that.  In any event, I think the smartest thing to do is isolate the boilers.  As long as I get sufficient heat transfer between the two via plate exchanger I'm happy and things are safer.

I was suggesting using the extra ports on the boiler, not teeing into the the main boiler loop. If large enough pipe was used it shouldn't raise the water level in either but it is hard to say what exactly will happen. Using a heat exchanger would remove any chance of overflowing though.

[willieG]

im jumping in here kind of late but  if you hook one boiler's return water to a plate exchanger and the other boiler to it also (i presume this is to help keep return temps up?) wouldn't this just prolong the agony of low return temps a little while? the boiler that is heating the return water would likley heat the return watr high enough that the boiler feeding the system would not come on untill the  "reheat" boiler ran low on wood then the 'system" boiler would agian have  to kick in  and you would be back to low tem return  temps. If that is what yu are talking about?
If so you need a bigger boiler...hook both boilers to a reservoir tank that they can both work together to heat this tank...then  hook your system to this tank..yo uwill still have low temp returns to the reservoir but you will now have 2 fires in paralell to heat the water quickly and recover?

maybe i am way off onwhat is trying to be achieved..if so...sorry

[dwneast77]

Willie, what you are saying makes sense and I like your idea about the reservoir tank.  It all comes down to the "cubic dollar" as I've heard it referred to.  I have the system I have and I'll have it for a while until there is enough funds to replace it with better.  For now it's just a matter of making the system I have run a little better and safer (for it's own sake).  As far as boiler 2 reheating the return water of boiler one, I see what you are saying about it keeping boiler 1 from running.  I think I can get past that problem by adjusting the aquastat on boiler 2 to run a little cooler than boiler 1 so that boiler 1 still has to work???  It may take some tweaking, I understand that.  But I'm constantly tweaking the way things are now.  The overflow problem is just so unpredictable.  And I can't seem to pinpoint what causes the sudden change in flow. 

I just want to make sure those of you who are following this post understand what I've done.  The supply and return lines on boiler 1 are 1 1/4".  On boiler 2, there are 2 - 1" hot lines and 2 - 1" return lines  (4 lines total) tied together at each end with 1 1/4" black pipe.  If my math was correct at the time, the two 1" lines held a touch more volume over the 1 1/4" line, that's why I felt comfortable with what I did.  Both boilers are within 25' of the main manifold system.  Both boilers have a Taco 014 pump pushing the water to the manifold.

Oh, RSI -  Where you quoted me in your last post, that was not directed at your earlier post really.  I was just trying to make sure you guys understood what is currently a problem/concern.   


Thank you all for your thoughts and suggestions.  It is greatly appreciated. 

Jeff

[RSI]

Where are the pumps mounted? If not at the boilers, that may be the cause of the overflowing.

What I suggested was pretty much the same as using another tank. I am assuming at least one of the boilers has an unused set of ports on it. This is where you would connect the pipes. If you tie into a line with another pump / water source you will still have problems with the water going to the wrong place.

I would have it setup so the pump was between the two boilers. Then for the return to the first boiler use a larger pipe. Any back pressure on it will raise the water level. Also, I would use a pump with a real low head rating. If they are close enough together and you use large enough pipe, a 007 should work.

I think your pumps might be fighting each other the way it is now. You might be able to use just one of the 0014 pumps and the 1-1/4" lines and get enough heat. Those 0014 pump are probably moving over 20GPM with that short pipe. (assuming no restriction after the manifold)

[willieG]

how about split the manifold in two and have each OWB feed a smaller system?