Passed the Acid Test

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Eric Johnson, Jan 4, 2008.

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  1. Eric Johnson

    Eric Johnson
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    I was anxiously awaiting our first real cold snap to see how the new boiler was going to perform under actual battlefield conditions. So here's the deal:

    On two consecutive below-zero nights, I loaded the boiler up around 11:00 p.m and went to bed. At 7:00 the following mornings, I had a house in the mid 70s and a firebox full of hot coals. Plus I'm heating half of a single-pane glass greenhouse, which I didn't do before.

    This compares to our old wood boiler, which on below zero nights would have needed to be loaded full around midnight, then again at 4:00 a.m., resulting in house temps in the mid to low 60s, and a long day of firing it hard to get back up around 70.

    So I'm pretty happy.
     
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  2. wdc1160

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    Do you have any evidence that heat may have been wasted eg. the boiler idled??
     
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  3. Eric Johnson

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    I think a lot of the heat from the old boiler went right up the stack. I tried everything from dampers to an add-on cat, but as an indoor boiler, I think it was "designed" to provide a larger share of radiant heat, which didn't do me much good in the small boiler room out in the barn. So that was wasted, too. Another problem was that I had glycol in the old system, so I had to use a flat plate hx to transfer heat into my house system. Every time that water made the loop, any inefficiencies in my piping and insulation were magnified accordingly. The old boiler was rated at 150 Kbtu/hour.

    The new gasifier is rated at 205 K, so it's got more ooomph, right off the bat. Plus, it's really well insulated. The only other difference is that I got rid of the glycol and piped it direct. I think that makes a huge difference. I don't have my tank working yet, so it does idle, even when it's below zero.

    But the bottom line is that I'm heating more space and keeping it warmer, while burning less wood and doing it cleanly. The old one was a smoke dragon. That's where the rest of the energy went.
     
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  4. wdc1160

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    In the midwest we all got to acid test our boilers two -5 days in a row, but it will be 60 degrees in Indiana by SUN. If you don't like 60 degrees in the midwest wait awhile it should be back to -5 in a couple of days

    Eric, you think you could have loaded it at 9:30 PM and still had a warm house?? I guess I am trying to quantify how much in the way of additional burn capacity you had at those cold temps. Clearly the old setup wasn't up to par with this.
     
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  5. henfruit

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    eric why did you have glycol in your old unit and not in this one? we had -10 at midnight here in new hampshire. ihave green wood 100 not burning round wood.i got a good seven hour burn keeping the house at 68.but the blower on the air handler ran most of the night.
     
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  6. Eric Johnson

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    That's a good question. Yes, an extra hour and a half wouldn't have made a big difference. There might not have been many coals in the firebox the next morning, but probably enough to get it going again with a few chunks of wood. And I didn't jam as much wood in the firebox as I could have. It was a little too cold out there to be screwing around.

    With the tank working, I'm guessing I could buy another 5 or 6 hours of warm house at those outside temps, assuming a tank up to temp and a firebox full of wood at bedtime.

    I can't tell you how nice it is not to have to get up at 4 o'clock and go out there when it's -10 to fill the boiler. That and not having to get up to a cold house.
     
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  7. Eric Johnson

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    Sometimes you get hung up on ideas that don't make a lot of sense, but you get married to them and plow ahead anyway. The glycol was one of those. Since the boiler and much of my piping is in otherwise-unheated space, I thought the glycol was a prudent precaution against freeze-ups. But glycol is more trouble than it's worth, IME. You'd be better off putting your money into better insulation and a piping strategy that would accomplish the same thing, just cheaper and easier all around. That's what I did this time.

    I think piping the water from my gasifier directly into the gas boiler vessel was the single most important improvement I made on this upgrade, other than going from a conventional wood boiler to a wood gasifier, of course. That's what the heating supply house guy told me four years ago when I was buying all the pipe and pumps and stuff. I made note of what he said, but did it my way. Turns out he was right.

    What's wrong with heating system glycol?

    1.) Costs like hell;
    2.) Can go acidic on you over time and eat up your components;
    3.) Hard to put it back into the system if you have to drain it off for maintenance;
    4.) Retards heat transfer (so I hear);
    5.) Requires the use of a heat exchanger between two pressurized systems if one doesn't have glycol in it. My house has 16 cast iron radiators, so even I'm not stupid enough to try to fill the whole thing with 40 or 50% glycol.
    6.) Needs replaced every 5 or 6 years.

    That said, I will be creating a glycol loop for my greenhouse, simply because it's a lot more likely to freeze up, and that would be catastrophic. Plus, I have the old flat plate hx laying around unused, so I might as well get some use out of it.
     
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  8. wdc1160

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    Eric. Can you elaborate a little on what your talking about here. If you have made mention of it in another post I havnen't seen I appologize. Point me in the right direction.

    Thanks Bill
     
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  9. Eric Johnson

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    OK.

    I have four zones coming out of the 1958-vintage Weil-McLain natural gas boiler in my basement. It's rated at 193 Kbtu of output. Since the circulators are all piped into the return lines of the (2) manifolds coming out of the bottom of this boiler, I don't have the option (or any desire) to bypass it. The downside on that is that by heating up the pressure vessel with the wood-heated water, there's the potential for much of the heat to go right up the stack. So during the heating season, I turn off the power to the gas boiler, turn off the gas and block the chimney.

    With the old boiler running glycol, I got heat into the Weil-McLain through a flat plate hx that circulated into the top of the boiler. This summer I repiped the wood side, running the one-inch line from the wood boiler into one of the one-inch tappings on top of the gas boiler. So now hot water from the EKO flows directly into the gas boiler and back out through the return. (I also have a 3/4-inch line looping between the greenhouse and the EKO, and there's also a leg that goes into the gas boiler if I want to bypass the greenhouse. I piped the heat storage hx for my tank with both 1" and 3/4" connectors, so that in the summer I should be able to dump the entire output of the EKO into the tank for DHW. At least, that's the plan).

    It seemed to me that with the flat plate hx on the gas boiler, it took a long time to get the heat transferred. Now that it's a direct link, there's a lot hotter water in the gas boiler vessel, so the response time is a lot faster.
     
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  10. wdc1160

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    Is this it?
     

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  11. Nofossil

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    So Eric, how much wood have you gone through so far? By my calculation, we're just a bit more than 1/3 of the way through the season.
     
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  12. Eric Johnson

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    Pretty much, except that it actually runs through a sidearm hx on my hot water heater before going into the gas boiler.

    In a couple of weeks there will be a big tank between the EKO and the gas boiler. I've got that piped with two hx units--one for storage and one for recovery, with a bypass.
     
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  13. Eric Johnson

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    I don't know. More than you burn in a season. Let's just say it's a small fraction of what I have available.
     
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  14. Bartman

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    I'm kinda out there on the fence about the glycol, I'm leaning toward the glycol as a better choice, although I don't have it in my system, (I'm usually draining once or twice a year for one reason or another). As in a car, glycol increases water's boiling point, but it also makes water wetter. Glycol allows water to stick to everything and flow better, and transfer heat better because of it's ability to flow onto metal. Drop water onto a dish, or a piece of steel. Does it bead up? Now "amend" the water by adding soap or glycol, the water won't bead up and cover the whole piece. It's one of the reasons a car will overheat with water only, not just because it raised the boiling point. Since my system has been mostly replaced, I think I will throw some glycol in to see how it performs. By using glycol, I have a feeling controls way work faster also, (aquastats). Just a few thoughts on the matter.
     
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  15. atlarge54

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    Bartman are you sure glycol helps heat transfer? I've always been told the opposite. "I was right once--- but it was a mistake."
     
  16. Bartman

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    Maybe a test would be in order to either prove or disapprove that theory.
     
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  17. sparke

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    Water is a better medium to transfer heat then glycol... I used to be a Plant Engineer at a local college. We had a glycol system feeding an airhandler. Yes Glycol is a pain in the arse.
     
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  18. Bartman

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    Well okay then, we heard from the expert. One question though, how much glycol was used, percent wise?
     
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  19. sparke

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    I am not sure what the percentage was. I was concerned with #'s , oil consumption , and payback times for system upgrades. I had the Gycol system looked at by 3 contractors. Johnson Controls, Seimens, and a local heating contractor. All three contractors told me water was a better transfer medium. They are the experts and I believe them...
     
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  20. Bartman

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    I will too, but I still might experiment, but just enough to add as a surfactant to the water.
     
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  21. Eric Johnson

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    It's usually around 40%.
     
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  22. Bartman

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    I was only thinking of maybe 10% for my system.
     
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  23. Eric Johnson

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    What the bucket say:
     

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  24. Bartman

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    Guess that eliminates that stuff. Although my system is totally indoors, and I have really no need for antifreeze protection, my train of thought comes from my automotive frame of reference. Ethylene glycol is more on the line of what I was thinking of using, but that may also cause some deteriorating effects on heating system components. There is a product called "water wetter" using in high performance applications that is supposed to increase water's thermal efficiency for cooling, so on that train of thought, would it work for a boiler? Or am I just wasting time thinking about it? Is it worth the trouble? I'm all for the phrase "keep it simple stupid", and use it regularly, perhaps this is just one of those times it should be used.
     
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  25. Eric Johnson

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    One of the big problems with automotive glycol is that if your system has a domestic water feed, as most do, you need some pretty special protections against backflow. More than just a check valve. You need a valve that will dump the water before it will allow it back into the system. It's not just to protect your family, but everyone else on the pipeline. Backflow is pretty unlikely in any event, but it is possible and therefore precautions are necessary. The stuff that came in that bucket is nontoxic heating system glycol. Costs like hell. I spilled some on my lawn last summer and it killed the grass.

    If you don't need freeze protection, there's no reason to use glycol in a heating system. It's less than useless.
     
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