Englander 28-3500 Backflow Damper Question

bigdgsr Posted By bigdgsr, Nov 7, 2018 at 11:50 AM

  1. bigdgsr

    bigdgsr
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    Nov 7, 2018
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    Got a question for the HVAC guys. Brought my 28-3500 with me to the new house. It worked wonders in my old raised ranch with ductwork built just for the stove. The new house is a 2 story colonial. House has existing oil/central air with 2 zones. Since I want to avoid any issues with the AC coil in the furnace plenum I'm going to tee off my 28-3500 and run a 8" feed to main trunk that feeds the 2nd floor and a 8" feed to the main trunk that feeds the 1st floor. Going to put dampers on both these runs. Stove will be the main source of heat 99% of the time. Should I put backflow dampers or manual dampers? I am going to have to run the furnace blower at the same time to help distribute heat to the 2nd floor. Is it possible to use a backflow damper in this situation or will the furnace blower be fighting the stove blower and push the backflow damper closed?
     
  2. FaithfulWoodsman

    FaithfulWoodsman
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    Nov 17, 2015
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    I have a very similar setup with the same stove. Where are the dampers exactly going and why are you using them? I guess I'm not clear on that. I have a large backflow damper in the main furnace trunk preventing backflow into the furnace from the 8" stove line and I have a manual shutoff damper in the 8" stove line to close that off during cooling season. No issues. However, I do not use the furnace fan to help push the warm air much, but haven't had any issues the few times I did. I installed all of it.
     
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  3. bigdgsr

    bigdgsr
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    Nov 7, 2018
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    No backflow damper in the main furnace trunk because I would be connecting my 2 8" feeds away from the plenum. Since on occasion the furnace might be used during heating season, I was hoping to put 8" backflow dampers on my 2 8" feeds instead. That way if the stove was off and I kicked the furnace on, I wouldn't have to manually go down and close the dampers. I just didn't know if I try to use the furnace fan with backflow dampers would it be enough force to close those backflow dampers even if the stove blower was on too.
     
  4. FaithfulWoodsman

    FaithfulWoodsman
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    Nov 17, 2015
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    My guess would be no, although the exact answer would require cfm's, linear length and such. However, if you are worried about backflow and enough pressure from the furnace, I don't think that would be an issue. The only reason the damper wouldn't close is that there is enough pressure from the stove fan, but that wouldn't effect furnace pressure and should only increase overall pressure. Plus Englander recommends dampers in the line, but does not recommend running a furnace fan strong enough to close the damper completely for very long for overheating reasons. Sounds like backflow dampers would be fine to me.
     
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