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  1. #1
    Join Date
    Aug 2004
    Location
    Great White North
    Posts
    92
    Looking for some thoughts and opinions on having a 1700 square foot bungalow zoned with the intent of using less gas to heat it.

    Thinking of two zones on the main level, one zone for the basement or use as a dump if one is needed.

    Easy split on the main...half is bedrooms and bath, half is living, dining and family rooms. Basement is used very little so it could be kept very cool. Basement is insulated and finished.

    Demo of the basement ceiling would be required to get the ducting reworked.

    Current equipment is Bryant 80% variable, 110K btu.
    Heat loss was calculated at 75,000 btu per hour at -40 deg C/F for the whole home.

    Insulation is R20 walls, R40 ceiling, triple paned glass throughout...not much room to improve any of this.

    Using 200 Gj of gas per year. At current rates, that's $2600 per year.

    Two people (I'm one) live in the home. Gas dryer and heated garage that won't be heated much this winter. Wife does not want to turn the heat down much as she's frozen most of the time...you know what I mean. Typical setting is 72 deg F. Home is occupied almost 24/7.

    If the house was zoned, would there be any worthwhile savings in gas consumption?

  2. #2
    Join Date
    Oct 2005
    Posts
    922

    Zone

    If possible zone sleeping and bath rooms, living space, and eating space separate. Some say different but it is how you use the space that will save you the cash.
    Most people eat, sleep, and some shower at the same time be it morning or evening?

    Programmable T stat can shut down and/or warm up as needed use occurs.

  3. #3
    Join Date
    May 2005
    Location
    columbus ,ohio
    Posts
    228
    I find that zoning is all about comfort and not money savings. I have one customer that was sold on a zone system to cut cost and she said she is not seeing any savings at all. I would try to cut cost by going the programmable t-stat way even though you said someone is home all the time. Even setting it back 2 degrees during the daytime will help.

  4. #4
    Join Date
    Mar 2005
    Posts
    66
    I can see two sides to this question, zoning can be installed for comfort but also can see where if used properly could save you money. Let me ask you a question about how you intend to operate your system? Zoning systems work much better when the maintained spaces are relatively close when it comes to set point. If you intend to have a large temperature swing from one zone to another then it might defeat the purpose you intend for it to solve. Too large of a swing might cause a longer run cycle on the furnace than if you just maintained it say at 72. I would not really reccommend installing zoning other than for comfort, but as a said if run properly it could very well save some money in the long run. I would carefully look at the amount of money it would cost versus potential savings.

  5. #5
    Join Date
    Apr 2004
    Posts
    7,680
    I'M with Mrssb, totaly here.

    To the Original Poster, if you have a 110k furnace and the ultimate demand in -40 (well beyond design) is only 75k then you are already dealing with an oversized furnace, if you now try to cut its workload even more you will surely shorten the life of your machine dramaticly. I simply cannot see a savings there.

  6. #6
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,705
    how old is that WAY oversized heater?? switching to properly sized 94% afue furnace would save a lot more than zoning would.

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,722
    LOL...

    How often does your area drop to minus 40?

    As the others said, get a 90+ furnace, properly sized!

    Also, if your humidity is low, adding a humidifier may allow you to lower your temp setting.
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  8. #8
    Join Date
    Aug 2004
    Location
    Great White North
    Posts
    92
    Guys...my furnace is properly sized and new (2004). It's 110K input, times 80% for efficiency, minus 10% for altitude = 79,200 btu/hr. And it is a two stage so it infrequently runs on high fire. And it has an Aprilaire 600 so the humidity is fine. Also, we have an Evolution control running the show, too.

    I would say that when we see -40 weather, it could be for a week at a time during the night once or twice a winter, but usually warmer during the day but maybe only in the -30's. I discussed this with my tech when selecting the equipment and he said most guys here rate the low temp here to be somewhere just below the 0 deg F range (off of memory). We see plenty of 0 deg F and lower during the winter. He made good sense...if we get a week of -40 and my btu output is based on just under 0 deg F, the the heat loss will exceed the heat input. To me, that equals long run times and a cold house.

  9. #9
    Join Date
    Mar 2004
    Posts
    1,042
    Oops... Sizing problem, yeah. And why on earth a new 80% furnace in that climate?

    A better alternative would have been a 94% efficient Bryant with a 90k input; 94.1% AFUE. Low stage output 49,000, high stage 75,000. Nothing wrong with having a small furnace and long run times- it's good for efficiency and good for comfort. You get steadier temperatures and typically more even temperatures from room to room (and within rooms, too).
    In my book going one size smaller would have been just about perfect. It would just barely keep up while running nonstop on high stage on those -40 nights. Either way, you are close to peak efficiency when it's ultra-cold; the problem is that by having that much capacity, it runs much less efficiently when things aren't so extreme, which is most of the time.

    Do you know what the heat loss for your area is for the normal design temperature (or what the design temp is in the first place?).

    It would take 15% less gas with a 94% furnace, based on the AFUE difference (94.1%/80%) alone. With the sizing difference, it would be a bit more difference than that in the real world. I'm really surprised you ended up with an 80% unit in that climate at all. The bottom line, though, is that living where you do and wanting to keep warm, that takes a whole lot of heat, and there's little you can do to change that.

    Infiltration: I'm going to assume the furnace is in the basement or some other heated space in the house. Is there a combustion air intake provided for the furnace, or is it sucking in ultra-cold air through all the cracks and crevices in the house to feed its fire? That might be one area for improving on what's there, since it doesn't make sense to rip out the brand new furnace. You don't want it depressurizing the house and causing cold drafts; that alone may be responsible for one or two degrees of why your wife wants 72. Adding an outdoor air intake to serve the furnace could make it feel OK to use a lower thermostat setting, and also improve the thermal efficiency of the house itself.

    Can you at least convince your wife to set the thermostat back some at night, when she will be asleep and under the covers?

    Infinity/Evolution type zoning isn't going to hurt the furnace, and heating less than the whole house all the time will certainly cut down on your heat loss, especially with such a large differential between indoor and outdoor temperature. There will be some countervailing efficiency loss because the furnace will have to run shorter cycles while doing less work to heat parts of the house, but you should still end up ahead overall.

    I'd look for at least three zones. At that point you can keep the basement a little cooler (maybe 65 all the time?), set back the bedrooms during the day (maybe 60-65), and ideally set everything back at night (living spaces and basement 60, bedrooms 65-68). Your heating cycles will be shorter while maintaining a setpoint, but you will at least get some nice long (efficient) cycles while recovering from the setback periods. The effective furnace efficiency might drop a little, but you'll lose a lot less heat through the walls, windows, and ceilings. Depending on the layout of the house and the way you use the other two bedrooms, you may want to make them a zone separate from the master bedroom, too.


    [Edited by wyounger on 11-03-2005 at 05:58 PM]

  10. #10
    Join Date
    Aug 2004
    Location
    Great White North
    Posts
    92
    Originally posted by wyounger
    Oops... Sizing problem, yeah. And why on earth a new 80% furnace in that climate?

    ***How can I have a sizing problem? The next smaller furnace in the mid-efficient range is a 88K btu input which will only out put 63k btu. Way below what we'd need (73,581, to be exact) on a -40 night. As I mentioned previously, if you have more btus going out than coming in, the thermostat would never be satisfied. Currently, we are experiencing adequate run times...about 20 minutes at slightly below freezing outside. We can't be that oversized if at all

    80% is still the normal install in brand new homes, here. I'm sure that's soon to change if it hasn't already. When we were spec'ing out our equipment, the price of natural gas was only a few bucks a Gj. That translated to $600 a year for gas. Now it's almost $13 a Gj or $2600 a year. I guess if we could read the future, we'd all be rich.***

    A better alternative would have been a 94% efficient Bryant with a 90k input; 94.1% AFUE. Low stage output 49,000, high stage 75,000. Nothing wrong with having a small furnace and long run times- it's good for efficiency and good for comfort. You get steadier temperatures and typically more even temperatures from room to room (and within rooms, too).
    In my book going one size smaller would have been just about perfect. It would just barely keep up while running nonstop on high stage on those -40 nights. Either way, you are close to peak efficiency when it's ultra-cold; the problem is that by having that much capacity, it runs much less efficiently when things aren't so extreme, which is most of the time.

    Do you know what the heat loss for your area is for the normal design temperature (or what the design temp is in the first place?).

    ***No, I don't. All I know is the heat loss for my home based on -40 outside, 74 inside***

    It would take 15% less gas with a 94% furnace, based on the AFUE difference (94.1%/80%) alone. With the sizing difference, it would be a bit more difference than that in the real world. I'm really surprised you ended up with an 80% unit in that climate at all. The bottom line, though, is that living where you do and wanting to keep warm, that takes a whole lot of heat, and there's little you can do to change that.

    Infiltration: I'm going to assume the furnace is in the basement or some other heated space in the house. Is there a combustion air intake provided for the furnace, or is it sucking in ultra-cold air through all the cracks and crevices in the house to feed its fire? That might be one area for improving on what's there, since it doesn't make sense to rip out the brand new furnace. You don't want it depressurizing the house and causing cold drafts; that alone may be responsible for one or two degrees of why your wife wants 72. Adding an outdoor air intake to serve the furnace could make it feel OK to use a lower thermostat setting, and also improve the thermal efficiency of the house itself.

    ***House is rated as "tight". We have combustion air to the furnace room as well as fresh air into the return. Per code in this area***

    Can you at least convince your wife to set the thermostat back some at night, when she will be asleep and under the covers?

    ***It's happening. We've dropped the night temp to 68 and the day is down to 71. As she acclimatizes to this, I'll drop the day temp down to 70.***

    Infinity/Evolution type zoning isn't going to hurt the furnace, and heating less than the whole house all the time will certainly cut down on your heat loss, especially with such a large differential between indoor and outdoor temperature. There will be some countervailing efficiency loss because the furnace will have to run shorter cycles while doing less work to heat parts of the house, but you should still end up ahead overall.

    I'd look for at least three zones. At that point you can keep the basement a little cooler (maybe 65 all the time?), set back the bedrooms during the day (maybe 60-65), and ideally set everything back at night (living spaces and basement 60, bedrooms 65-68). Your heating cycles will be shorter while maintaining a setpoint, but you will at least get some nice long (efficient) cycles while recovering from the setback periods. The effective furnace efficiency might drop a little, but you'll lose a lot less heat through the walls, windows, and ceilings. Depending on the layout of the house and the way you use the other two bedrooms, you may want to make them a zone separate from the master bedroom, too.

    ***the more I think of zoning, the more I think that a modulating furnace would be a better fit for zoning instead of the two stage I currently have***

    ***thanks for the discussion***


    [Edited by wyounger on 11-03-2005 at 05:58 PM]

  11. #11
    Join Date
    Oct 2005
    Location
    Minneapolis
    Posts
    22

    This discussion is confusing to me. It makes no sense for installers to be selecting 80% efficient furnaces in a climate as cold as you suggest. And your profile says Pennsylvania. Where do you live? If you live in Pennsylvania I think you are nuts to size a furnace based on -40 F or C temps. If you are in the north central part of Canada that would make sense but then why would the local installers primarily suggest 80% AFUE furnaces?

    Jon (newbie non-professional)

  12. #12
    Join Date
    Mar 2002
    Location
    Beautiful British Columbia
    Posts
    1,242
    garryb,
    Great white north, does that mean northern Canada, and if it is a lot of these guys are giving you the straight goods, you should have used a 90+ furnace, which could have been 2stage variable speed, make really doesn't matter as long as it is one of the top brands and has a decent warranty. Maybe your contractor is not comfortable installing a 90+ some installers are intimidated by them because they need to be installed properly and set up properly when first fired up. For the price of zoning and the destuction of your basement maybe you can make a deal with the contractor to change the furnace to a 90+ and it may end up being cheaper and save you a lot more money. I usually only sell zoning as a comfort and convience thing rather than an energy saving product.

  13. #13
    Join Date
    Aug 2004
    Location
    Great White North
    Posts
    92
    Thanks for the discussion. To clarify..."the great white north" is indeed Canada, not Pennsylvania.

    Also, at the time of selecting the 80% unit, the price of natural gas was not an issue at $2 per Gigajoule. Now it's almost $13 per Gigajoule. Some of you seem to be overlooking this point.

    I am going to consult with the contractor about us getting a high efficiency unit installed. I hope to heck there is a market for a slighly used mid-efficient unit so I don't have to take a big hit.

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