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Hooking an IWB in the shop, to the house OHW boiler?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by oldh2o, Sep 19, 2012.

  1. oldh2o

    oldh2o New Member

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    Hi, I read all I can find, but I have no experience with oil or wood boilers.

    House has 10 yr old OHW boiler, 2 zones, and supplies DHW. about 1400 sq foot house, 2 zones.

    Shop is 103 feet away and will need 120 feet underground piping. A homemade transit, shows that the 2 boilers will be almost dead level to each other, the top of the wood boiler might be 2 feet higher than the top of the oil house boiler unit.

    The indoor wood boiler that will be in the shop, is a 1982 Jensen 24B. Pipes are not hooked up yet, but we test fired it with water jacket filled, about 20 gallon capacity. The combustion blower fan does kick out at the preset temp. This seems to be a closed system, as it says "30 PSI max" and has a pressure relief valve at top. The tag BTU only says: 100,000 MIN.

    I am lost with closed vs. open boilers? and I read that a closed system should have Oxygen barrier PEX? So, I can't order/or install underground PEX yet, until I know how to hook these two boilers together. Also, can I get by with the foil/bubble wrap piping, instead of the foamed Pex?

    I would like it to be very simple for this season, as it's a very late start. I am in the shop all day, so I can monitor it.

    I found this very simple diagram on this site, will this work?

    [​IMG]

    My questions are; is that a closed system? and should the indoor wood boiler circulator pump run 24/7? ...and the "air valve" shown, I would like to know about that.

    I assume I would have to add a second aquastat & circulator on the wood boiler tank to dump overheated water into a loop in the shop? I mainly want to heat the house zones, not the shop, as a priority.

    Thanks for any simple advice you can give.

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  2. Eric Johnson

    Eric Johnson Mod Emeritus

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    Both systems are closed (pressurized), so you can just connect them directly. You can use the wood burner to heat water that you use in the shop and any excess can be pumped into your existing boiler vessel and distributed through your existing zones. You may need an additional (or bigger) expansion tank, pressure relief valve on the wood boiler, etc. You will also need a Class A chimney for the wood side.

    Nothing too complicated.

    Whatever you decide to use underground (and yes, it needs to have an ox barrier), just make sure it doesn't allow outside water to leak in, or your heat will never make it to the house. One common approach is to wrap PEX in insulation and then shove it into pvc pipe, along with wiring, etc. Be aware that any pvc joints are susceptible to leaking, so you want to use the longest runs of pipe that you can. Continuous, flex pvc is probably an even better solution if you can cram all the pex and insulation into it.
  3. Eric Johnson

    Eric Johnson Mod Emeritus

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    The "air valve" in the diagram looks like an air scoop to me. What that does is trap and expel any tramp air that may exist in the system. It's not necessary, by any means, but nice to have over time. It is important to at least have manual vents (or some other way of venting trapped air) from return lines that flow downward. My dad always told me that venting hydronic heating systems is a "black art," but I've found that putting simple vents at all the places you suspect you might have a problem is usually sufficient. One thing that works well are the cast brass "vented 90s" that are typically used with baseboards. Some gate- and ball valves also have vents built in. The diagram looks good to me, BTW. I've always favored installing circulators on the return lines, because the water tends to be cooler and I think it's easier on the equipment. However, current conventional wisdom is that they should be on the supply sides for greater efficiency. I say, "whatever." Works fine either way.
  4. oldh2o

    oldh2o New Member

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    Eric, thanks for the replies. I did forget to ask about which line the wood circulator pump be installed in. My wood circulator pump is still wired to the controls, but the plumbing flanges and pipes were missing, and I thought it might be OK to run the pump on the return side.

    So, that leads to another question on the wood circulator pump;

    -Would this system work OK, if I added a 2nd aquastat on the house oil boiler tank, that would turn the wood circulator pump on, but only when the oil water tank called for heat? (that aquastat would be set at a different temp, than the one that kicks on the oil burner)

    --or should I keep it simple, and run the wood circulator 24/7 through the season? Which would be better, and why?

    -also, I called the local wood boiler parts department about underground PEX, and after I gave the info on my total run lengths, etc, he said "most people would run the 1" PEX, and that should be fine", and he did not think the "much more expensive" 1-1/4" would be needed?

    Thanks again. ... I'm starting to gain some confidence now :)
  5. Eric Johnson

    Eric Johnson Mod Emeritus

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    You could wire the pump to the stat on your house boiler that calls for heat (or for the flame to kick on) and just shut the burner off when you don't what to use it. Or, you can wire it up to a separate aquastat. Either way. I wouldn't' run it 24/7 as there's no point, though it wouldn't hurt the pump and wouldn't draw much additional electricity. However, you don't want to be pumping hot water out of the house and into a cold boiler in your shop, so it's good to have some simple controls. Don't forget to isolate everything important (pumps, boilers, etc.) with valves and, when appropriate, bypass piping.

    Thinking about it, probably what I would do would be to wire the pump up to a stat on the wood boiler, kicking on the circulator any time the boiler temp exceeds, say, 140 degrees. That keeps your wood boiler from overheating and guarantees that you will always be pumping hot water into the house. BTW, you should also design in some way to heat the return water to the wood boiler so that it stays warm--say 140 degrees. I do this by circulating hot water from the supply on my boiler to the return in a loop. And I run that pump 24/7. What it does is warm the return water to avoid thermal shock on the boiler, which will eventually cause it to corrode and fail.

    I agree that 1-inch pex is probably plenty of capacity for a boiler of that size (100K btu). That's what I use on my boiler, which is 205K. You could probably get away with 3/4, but might as well go for the one-inch stuff in case you ever upsize the boiler.
  6. willyswagon

    willyswagon Burning Hunk

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    This is exactly how the contractor set up and explained my system when he plumbed it on Thursday.
    He said that once I get over the fact that the pump is running all the time that the aqua stat is over 145, I'd love this set up.

    He did say the key to its success was to insulate the pipes to death.
    Incuding all piping in the existing boiler room.
    They also put a relay on the existing boiler so that if the wood circ pump is operating(only when above 145) that the oil boiler will not fire
  7. rkusek

    rkusek Minister of Fire

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    Read the sticky above by Tennman about UG pex lines. I wouldn't use anything but spray foam in trench or Thermopex brand if you want a ready to install solutions and don't mind paying a little more.
  8. oldh2o

    oldh2o New Member

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    Thanks for the replies. I have had more input from local people also, so we think we have a plan for the wood circulator pump.

    There is no place that I can see, to put a second aquastat on the oil burners water tank. So, we will run a test season with the wood circulator running 24/7.

    Hopefully, the wood boiler can keep up to the house demands, but if it needs a bit of help on coldest nights, the oil burner can still assist automatically, because those controls won't be changed right now.

    ^ If this is poor planning, please let me know. We plan to start on this project this week, digging, etc, as well as installing the wood boiler in the shop.

    I will be always working in the shop, near the wood boiler all during daylight hours, 7 days a week, so I can monitor any issues. Thanks again.
  9. Eric Johnson

    Eric Johnson Mod Emeritus

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    You just want to be careful that you're not pumping oil-heated water into the shop--at least I think you don't want to do that. You might find that you can simply shut the burner off and just heat everything with the wood. That's fewer headaches. Whatever you do, it shouldn't affect your digging and other installation plans. It's how you set it all up that makes the difference, and you can change that to meet your needs.
  10. oldh2o

    oldh2o New Member

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    Just an update.

    I am on wood heat for 1 week now.

    I did add an expansion tank and an automatic air scoop valve on the wood boiler. I run the wood circlator 24/7.

    The first night was a problem. My son was monitoring the wood boiler every hour and it was OK till 2 am when temp went to 260 and 30psi pressure. That was caused by the combustion air blower door flap letting the draft run too strong. (the blower does turn off at 180, but the draft continued)

    We now do not ever use the blower and also have closed that flap permanantly.

    We made a new manual adjustable draft control on the wood loading door, and run it like a woodstove.

    We still had the oil boiler fire up every 45 minutes, but it ran for only 45 seconds to 1.5 minutes each time. The problem was cured by insulating all the copper 3/4" pipes in the cellar. The pipes were getting cold if the zones were off, and when a zone came on, the cold water degraded the water temps in the oil boiler. Now it's good.

    I did read the thread on the guy who lost power in the hurricane Sandy and had his Pex melt and fail. I need to follow the advice on using a new valve that opens when power is lost, that will dump heat to a new home brew radiator made from finned baseboard pipe. I would also like to add a similar power operated draft control flap, that will shut tight if the power is lost.

    After a stressful week, I can say that a person with zero experience with oil boilers and wood boilers, can get a system to work. I just need to keep following the advice on this forum, to make it safe and stable.

    Yes, I'd like a hot water storage tank, but that will be next season, if I can run without in real cold weather. Just have other things to do in life right now. Thanks for the help so far.
  11. flyingcow

    flyingcow Minister of Fire

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    Congrats. You'll be tweaking things most of the winter. This is a good group on this site. You're addition/experience to it will be nice.
  12. smurphy

    smurphy New Member

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    Hi

    I have a 1981 Jensen 24b 100,000 btu want to know if anyone has the same thing and what size fan is on it. Last person changed fan 1/30 hp 1550 rpm.

    Thanks Shawn
  13. oldh2o

    oldh2o New Member

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    I have a Jensen 24b in use. My blower was new when I got the boiler. It works good, so I will look for a tag on the blower today and post what it says.

    By the way, in warmer weather, with the blower flap door open, the boiler can overheat, even with the circulator pump running 24/7 hooked into the house oil burner water storage tank. The problem was that the front flap door on the wood feed door, fits way too loose and draws in additional combustion air. I removed that cast iron flap door, and sealed it with a thick steel plate. Now, I can leave the blower flap door open all the way, and it won't overheat, even if outdoor temps are above freezing, and the house zones are not calling for heat. Works good now.
  14. oldh2o

    oldh2o New Member

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    Just looked at mine:

    Dayton Model AL-440
    Number 7021-3466

    3030 RPM
    1/125 HP

    Right now, my son has set the blower to come on at roughly 135-140, and off at 155-160 ...going by the actual temp reading on the gauge up front. He experiments for duration of burn capacity, while maintaining decent domestic hot water temps.

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