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Thread: Hybrid Oil

  1. #40
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    If your going to zone it.
    Then I would get the 2 stage unit.
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  2. #41
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    Quote Originally Posted by beenthere View Post
    If your going to zone it.
    Then I would get the 2 stage unit.
    After he mentioned zoning, I was thinking the same thing. Thoug the SEER is only 13.50, the advantage is the staging. Maybe that's why the Infinity 16 was recommended in the first place. The HSPF isn't bad at 8.70 with the CNPVP4821A** coil.

  3. #42
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    Zoned, he'll get better efficiency from the 16 SEER then the single stage 15.

    Won't short cycle or trip the DATS like the 15 will. So less chance of short cycling.

    Improved moisture removal over the single stage.

    Be able to use first stage at higher and lower outdoor temps.

    EWC zone panel can be set not to use second stage unless both zones are calling.
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  4. #43
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    Quote Originally Posted by RyanHughes View Post
    After he mentioned zoning, I was thinking the same thing. Thoug the SEER is only 13.50, the advantage is the staging. Maybe that's why the Infinity 16 was recommended in the first place. The HSPF isn't bad at 8.70 with the CNPVP4821A** coil.
    The plan is (was?) to keep the single-stage furnace.

    What led me to zoning is that the register airflow on one side of the house -- the side with the bedrooms(!) -- is rather weak. The design of the house precludes fixing it within any even remotely reasonable cost*, which is why the two-zone solution was recommended -- running a single zone at a time should increase airflow (at least to some degree) within that zone.

    I don't know if that makes sense with a single-stage furnace, but that was the thinking behind it.

    - V

    * We might as well replace the house at that point; long story, but let's just say that airflow isn't the only reason we would consider tearing down and building anew. We would need to win a lottery, though. And since we don't buy lottery tickets, the likelihood of winning a lottery is ... rather small. Which means we'll be in this house, as currently designed, for a while. Which brings me back to putting in a two-zone hybrid system....

  5. #44
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    Zoning is commonly used as a solution to poor air flow in a section of the house. It also commonly creates other problems when misapplied for that use.

    Zoning may or may not be a good solution.

    If its all the supplies on that side. Make sure your contractor checks that side, to make sure it won't short cycle the oil furnace too much, before he installas the zoning system.
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  6. #45
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    Smile

    Quote Originally Posted by beenthere View Post
    If its all the supplies on that side. Make sure your contractor checks that side, to make sure it won't short cycle the oil furnace too much, before he installas the zoning system.
    A very valid concern. So here's some background information, and (ultimately) how we got to the two-zone thing:

    The "main" trunk (supply) from the furnace is a pretty good size; the one that serves the other side of the house (where the bedrooms are) is about half the size (in cross section). There is no means by which its size can be increased. Where it splits off the furnace, the design "favors" the main side (i.e., there is less inherent resistance, _before_ accounting for duct cross section). IOW, the cards are stacked in favor of strong air flow to the main side, and weak air flow to the BR side. When we moved into the house, the air flow into the main side was terrific, while air just sort of limped out of the registers on the BR side.

    There are two returns from each side of the house (four returns total).

    In order to better balance the air flow in the house, I removed (fully removed) one of air returns from the main side, and inserted my own damper in the main supply line (i.e., cut a slice in the side of the duct, inserted a piece of sheet metal, and used aluminum tape to lock it in place). I also manually dampered several of the supplies to individual registers on the main side.* And fully removed one individual supply (to a register) on the main side and one on the BR side, as those registers were unnecessary.

    I also moved the thermostat from the main part of the house to ... well, essentially to the border between the two sections.

    As a result of these changes, air flow to the BR side of the house has increased substantially, with the net result that the temperature in the house is much better balanced (in both seasons). It is quite amateurish, but it works. And the oil furnace doesn't seem to be short-cycling (as long as I keep a clean air filter in there -- with the changes that I made, the furnace is now MUCH more sensitive to the cleanliness of the air filter, and will tend to short-cycle if the filter is dirty).

    When I brought in the first prospective contractor for the hybrid job, I discussed the air flow issue with him, and my desire to implement a (hopefully) non-amateurish solution. He recommended either a two-zone system with a bypass, or replacement of the entire system (i.e., install a new HP and furnace). He recommended against replacing the furnace -- which was installed in November 2003, and, according to all who have looked at it, seems to be a reasonably efficient single-stage model. The first contractor said that the bypass will reduce the tendency of the furnace to short-cycle.

    I could replace the entire system with a much higher efficiency, multi-stage model, but the expected savings in annual oil usage will be minimal, and thus isn't really economically viable. (Yes, there's also summertime AC savings, but our current roughly-8-SEER air conditioner doesn't run all that much as it is (lots of trees keeping the house shady), so I suspect that a change from 15 SEER (proposed system) to 19 SEER (multi-stage system) won't pay back too quickly, either.)

    I haven't quite given up entirely on the idea of replacing the oil furnace. But it's difficult to justify at this point. Especially to my wife, who would MUCH rather have a new kitchen than a hybrid heating system, but at least recognizes that the hybrid system will pay for itself within some period of time, while a new kitchen will not. :-)

    - V

    * This begs the question, "Why not just close off the register instead of inserting a damper into the duct?" Good question -- and I initially tried that. But the air flow was *so* unbalanced that air still poured out of the registers even when they were closed off. Installing dampers in the ducts was the only effective means of reducing the air flow.

  7. #46
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    Hopefully you told the contractor all of this also..

    What you did, is covering up the problem. And ceating one that your not reconizing as a real problem at the moment.

    Your riding just under your furnaces high limit temp, which is why you notice the chort cycling if you don't keepo after the air filter.
    You are risking burning out the HX if you continue to use it like this.

    Open that return back up!

    Have your contractor check if your furnace can be down fired.
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  8. #47
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    Quote Originally Posted by beenthere View Post
    Hopefully you told the contractor all of this also..
    Oh yeah -- that and more. (You guys got the expurgated version, believe it or not.)

    Quote Originally Posted by beenthere View Post
    What you did, is covering up the problem. And ceating one that your not reconizing as a real problem at the moment.
    Yes, it's covering up the problem -- although the only way to PROPERLY solve the problem involves a lot of drywall work. With that said, though, you've really shed quite a bit of light on the problem ... the two-zone solution with a multi-stage blower is sounding like the best option right now (without going the new-drywall route).

    Quote Originally Posted by beenthere View Post
    Your riding just under your furnaces high limit temp, which is why you notice the chort cycling if you don't keepo after the air filter.
    You are risking burning out the HX if you continue to use it like this.
    I didn't know that; I figured it was okay as long as it wasn't short-cycling. Interesting. This is moving the peg closer to the new-furnace option.

    Quote Originally Posted by beenthere View Post
    Open that return back up!
    No, that return was in a really dumb place to begin with. If I need the air volume, I'd have a new return installed in a different part of the house. More drywall involved, though.

    Quote Originally Posted by beenthere View Post
    Have your contractor check if your furnace can be down fired.
    That sounds like it might be a good option if I decide to keep the current furnace. I need to do some more research into this, and also get some additional quotes, to see where it comes out in the cost-benefit analysis.

    Many thanks for the info!

    - V

  9. #48
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    You need that returns additional air.
    Open it, or relocate it.
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  10. #49
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    Quote Originally Posted by beenthere View Post
    You need that returns additional air.
    Open it, or relocate it.
    The first guy to look at the job did some quick (back-of-the-envelope style) calculations and concluded that I'm okay without that return. However, a different prospective contractor is sending his "duct guy" over sometime this week to price the two-zone configuration; I'll have the duct guy take a look at the situation and see if I need to relocate the return. (Opening it back up is not an option. If you could see the house, you'd look at that return and ask what the installer was thinking when he put a return there.)

    Speaking of which, any comments or differences between Ultra Zone dampers and Honeywell dampers?

    Muchas gracias. I'll let you know what the duct guy has to say....

    - V

  11. #50
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    I use EWC mostly, so I am partial to them.

    If, I was going to use honeywell dampers, I would also use the Honeywell W8835 comunicating zoning system. Which is someting you may wish to consider.
    It could help your system. It will open the damper to the other zone at times to prevent the zone that isn't calling. From calling 5 minutes after it satisfies teh other zone.


    Your first guy did his calcs wrong then. An oil furnace is NOT suppose to ride its high limit. A 50 to 70° temp rise across the heat exchanger is what you should have.(varies alittle with model and brand) If its shutting off on its high limit. And you have the stat set at 70, then it has closer to a 140° temp rise across the coil.
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  12. #51
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    Quote Originally Posted by beenthere View Post
    If, I was going to use honeywell dampers, I would also use the Honeywell W8835 comunicating zoning system. Which is someting you may wish to consider.
    It could help your system. It will open the damper to the other zone at times to prevent the zone that isn't calling. From calling 5 minutes after it satisfies teh other zone.
    Pretty slick! I'll look into it. Thanks for the pointer.

    Quote Originally Posted by beenthere View Post
    Your first guy did his calcs wrong then. An oil furnace is NOT suppose to ride its high limit. A 50 to 70° temp rise across the heat exchanger is what you should have.(varies alittle with model and brand) If its shutting off on its high limit. And you have the stat set at 70, then it has closer to a 140° temp rise across the coil.
    It looked like he calculated duct sizes (in and out). We didn't discuss temp rise -- and though I should have mentioned short-cycling, I did not. I was focused specifically on airflow to the registers.

    - V

  13. #52
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    I used 84,000 BTU output, but you can see it doesn't take much of a air flow restriction to increase temp rise.


    BTU output, Temp rise CFM

    84000-----50----- 1,556
    84000-----55----- 1,414
    84000-----60----- 1,296
    84000-----65----- 1,197
    84000-----70----- 1,111
    84000-----75----- 1,037
    84000-----80----- 972
    84000-----85----- 915
    84000-----90----- 864
    84000-----95----- 819
    84000-----100----- 778
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