Why AC air handler is Electric Furnice?

Discussion in 'HVAC Heating & Cooling' started by Bratan, Jul 29, 2014.

  1. Bratan

    Bratan Member

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    New York
    My AC air handler is in the attic. I was just there (and fell thru the ceiling but that's another story) and noticed that it says "Electric Furnice" on it. I'm very curious why it says that? My house is heated by oil boiler in the basement. Can heater be hacked into part of AC or it's can be both?
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    It is not uncommon for an air handler to have auxiliary resistive heating elements in it. Now, whether they are actually there and hooked up is another story. They're more common when you have a heat pump for when it is too cold for the heat pump to generate enough output - then, the backup heat turns on. If yours actually has those, it will have some pretty hefty wires going in, and some large circuit breakers back in your panel.
  3. Dana

    Dana In the trades

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    Putting air handlers & ducts in attics above the insulation is a lousy practice. It guarantees higher cooling( or heating) loads, and duct/air-handler leakage drives air infiltration ballistic (an even bigger load.) Taping all of the seams of the air handler with FSK tape (aluminum duct tape), and sealing all of the duct seams/joints with duct mastic takes some (but not all) of the sting out of it. Air sealing the duct penetrations through the ceiling is necessary (and often difficult, in a retrofit).

    At the recent years oil & electricity pricing heating with heating/cooling heat pumps is quite a bit cheaper than heating with oil, even in colder areas. But that's true only if the ducts are all inside the pressure & thermal boundary of the house. (Since you have a basement, running the ducts in the basement would make more sense.) Ducted heat pump systems are rarely as efficient as ductless mini-split type technology, but it's still cheaper than heating with oil. (Heating with an electric furnace is going to be more expensive than heating with oil in most locations.)
  4. DonL

    DonL Jack of all trades Master of one

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    Can you come to Texas and change the code ?

    Most homes here are built just as you describe.

    When I first seen it I was in shock.

    That house may have Aux heat, but the electrical service may need updated to use it on 240V. My guess is that the blower is 120V.

    Many older houses that had oil heat were wired for 98-110V in the day.


    Can You still get Oil ?
  5. Dana

    Dana In the trades

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    I can come to Texas, but it's not within my power to change the building codes there. (If I could, I surely WOULD though- it's a crummy way to build, and Texans deserve better!) The popularity & economy of slab-on-grade construction make attics a cheap & easy place to route HVAC ducting, but routing any part of the duct system outside the thermal & pressure envelope of the building comes with a big uptick in cooling & heating cost.

    Sealed & insulated crawlspaces would be a better place to route the ducts, but it's more expensive to build that way (another set of joists, with more expensive floor.) A slightly less expensive option is a dropped service cavity below the air-sealed & insulated attic floor, which can use much smaller/cheaper framing lumber, since it's only holding up the ceilings, electrical routing, & ducts. But since few builders are familiar with how easy that can be, with no market to drive it, that's not how most homes are being built. A lot of higher performance houses are now built this way, along with housed insulated at the roof deck, making it a conditioned attic. But insulating at the roof deck typically involves more expensive insulation & air sealing.

    Oil heating (both boilers & hot air) is still fairly common in the northeast, particularly in locations that are off the gas-grid, since it's cheaper per BTU than propane, and outside design temps are below where many heat pumps won't operate (or won't operate efficiently.) The heat pump solutions are getting better year on year, both on efficiency and l0w-outdoor-temp capacity, but electricity is pretty expensive in much of the region. Ductless mini-split heat pumps still beat oil for heating costs by a huge margin, even in those higher-priced electricity markets. But even dual-fuel units with propane burners as the second stage ducted heat pumps or air source heat pumps with auxiliary heating strips are substantially cheaper to heat with than an oil boiler.

    In smaller houses with open floor plans adding just ONE ductless mini-split can sometimes cut the heating costs by more than half, even if they keep the oil-boiler in place as backup for when it hits negative double digits. This testimonial video by a couple who live in Presque Isle ME (US climate zone 7, a-yuh, pretty damned cold!) put out by Efficiency Maine may be an outlier case, but it's not an extreme outlier.
  6. clocert

    clocert New Member

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    Location:
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    You can not build basement in Texas. There is too much water underground. therefore, the air handler and also water heater are all located in the attic. We of course understand the attic's heat load, but this is the best choice interms of $$. If you want to put the air handler somewhere else, in another utility room, of course, you just have to pay for the room, and all engineering redesign work, etc. we can do it. but so far no one asked me to do that yet. I built houses in NY in early years, houses there all have basement.
  7. DonL

    DonL Jack of all trades Master of one

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    I am lucky not to have a water heater in the attic. Very dumb place to put it, I think.

    When Texas had the freeze in the 90s most everyone around here had busted water pipes in the attic. I had to heat my attic and was able to save my house. I used a 100,000 BTU heater to protect my pipes.

    You could not buy any PVC pipe at that time, and a lot of homes that did not have flood insurance were not covered. How can a insurance company do that ?

    Nice Post Dana, I am going to look into a split system, I am a bit confused on the best brand to go with.
    Have you played, or do you know anything about Solar Cooling ? I would like to play with a Ammonia system.

    You can have a basement in Texas, But it is not cheap to do it right. I have seen many underground shelters and bunkers. I have also seen them flood because they had no redundant power or pumps.


    I hope I did not get too far off topic, I was just being DonL...
  8. Dana

    Dana In the trades

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    With all due respect, it's only "...the best choice interms of $$..." for the builder or very short-term owner. It takes no rocket science to frame a bit taller and install it all below the pressure & thermal boundary of the building envelope, and both reducing system losses and loads by significant double-digit percentages. If electricity were free, or mechanical systems had far more efficiency than real-world versions it might not matter. But if you plan to live there for an extended period there's serious payback in building with the ducts inside the building envelope. (Half of all home-owners in the US have lived in their house for more than a decade.)

    Also, while water tables may be high in some parts of Texas, that condition is far from universal. I iknow folks in Texas who have basements.

    [edited to add]

    Don: I have zero experience with ammonia systems or solar cooling. Better split systems these says have variable speed scroll compressors & blowers, and utilize variable refrigerant volume valving like the "inverter drive" ductless systems do. Carrier Greenspeed looks pretty good for 2-3 ton systems but there are others, and bigger. Some friends just installed a 4 ton Lennox XP25 last fall (which took some getting used to on their part, having previously only heated with hydronic boilers and a high mass masonry wood-burner.)
    Last edited: Aug 4, 2014
  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    There are a lot of places in west Texas that would love to have a ground water problem! In El Paso, their municipal water wells are nearly 4,000' deep! Big state, big variations in conditions. In lots of parts of Texas, digging a hole for a basement is almost like trying to dig through rock...a slab is SO much easier, and that makes things less expensive.
  10. clocert

    clocert New Member

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    Location:
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    I don't know much about El Paso or west Texas. I only build houses in Houston area. In almost all subdivsions, basement is not allowed by code. We have more then 100 builders in this city, the competition is so strong that I have to keep the price down and build something that people want to buy, believe me every dollar counts, buyers want to see nice kitchen, bigger bath room, high ceiling living room, 2-story fireplace, surrond sound movie room, etc.. the location of AC is not important at all, no one even care where the AC is located. Of course there are exceptions, I have seen custom built houses, they don't follow these rules, but they cost a lot more, and there are not that many people can afford of custom homes anyway.
  11. Dana

    Dana In the trades

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    The fact that it's allowed by code doesn't mean it's a good idea. I get that it's a cheaper way to build and has become pretty much the standard. But it's a lousy practice, even if it's modestly cheaper to build. It simultaneously lowers comfort levels and increases the utility costs.

    The fact that the market doesn't understand or care about that doesn't make it the "right" way to build, but in a sharply competitive market I understand why it's done, and why changes in the code are probably going to be the only way to improve upon a lowest-common-denominator approach that has become a standard.

    I understand why basements aren't built and may be actively disallowed in the high water table hurricane/flood susceptible areas like Houston, but are crawlspaces (conditioned or otherwise) similarly disallowed there?
  12. clocert

    clocert New Member

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    Location:
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    You don't konw Houston. There is no crawlspace in the houses here. one major reason is there are too many bugs in the ground, ants, termites, snecks, mice. wasps, etc.. at least 20 different kinds, and all year around. No one will buy a crawlspace house here. As I said we have more then 100 builders here, we are not dumb, we know what we are doing. I don't know where you are, or if you are in this trade, Hope you can come here and build a few houses. Theory is one thing, right or wrong, you have to be able to survive first.
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Houston is a totally different world than the high desert in western Texas...El Paso's municipal wells are around 4,000' deep...I'd bet you'd hit water at 10' or less in Houston! You do what you have to.
  14. DonL

    DonL Jack of all trades Master of one

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    Deleted

    Too far off topic
    Last edited: Aug 7, 2014
  15. clocert

    clocert New Member

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    Location:
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    This is too far off the topic, we need to stop here.
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