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Thread: Bad Dilemma...

  1. #1

    Confused Bad Dilemma...

    Our house is 6mo old. No choice on HVAC contractor.

    House is 2800 SF on two floors in Central NY. House has 4 zones with 7 and 3 vents on 1st floor and 5 and 4 on the second floor. The ducting is 6"; supply plenums are 8x14; two taper to 8x12 for last duct at end of runs. Ducts do considerable meandering...

    Furnace is a Rheem RGRL 90k BTU input (2 stage). Fan will run at two speeds in heat mode but only on High in cool mode. Zonex controls for the zoning. The fan speed can be tweaked a bit but I have no idea if that was actually done or not.

    NOTE: I had a discussion with owner of original mechanicals company and was told that with a zoned system, a variable speed unit (or modulating one) would be a waste of $$. That lead to the Rheem unit cited above.

    Amongst 5 outfits which I have talked to to put in central air; one said the furnace should have been a var speed fan type but simply quoted a 2 stage 16 SEER Carrier unit. All said a TXV value would be used. Three said nothing about current configuration.

    Now enter #5 in the "who-will-install-the-AC" contest. At a minimum, they feel that I need a barometric bypass installed (and it should have been done in the first place) and with that, would offer a 15 SEER single stage 3.5T AC unit.

    The bombshell was that, even with the minimum fix proposed, I will likely face premature component failure (blower fan, possibly compressor especially if 2 stage) and a less efficient operation. Suggests that Furnace be replaced along with a coordinated control system along with adding a 2 stage AC unit (4T/2T). (Carrier Infinity systems.)

    Price to do the full fix will be about double the "get by" fix. (I do possibly have someone I can sell the existing furnace to moderating my $$ hit)

    I am PO'd at the original mechanical outfit for apparently giving completely wrong advice as to using a modulating furnace. I honestly don't think they wanted to have to deal with more complex systems...

    Oh, since this is the retirement home it's not like we are planning on leaving in 3 years to stick the next guy in line. It also means that efficiency is very important - I don't calculate cost benefit on today's prices as I believe they are only going to continue to rise.

    Advice? I simply do not know what to do.

    Thanks.

  2. #2
    Join Date
    May 2008
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    newnan,ga
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    why does the house have 4 zones instead of two. for that small vent count 2 would be suffecient.

  3. #3
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    May 2000
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    Indianapolis, IN, USA
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    First, the blower should only be on high for cooling if you have a 5 ton A/C. If you get a 3.5 or 4 ton, it should be slowed down based on duct pressure.

    Do you have a zone panel that properly stages the gas furnace? Probably not knowing new home methods. Probably the cheapest control they could get.

    As for a new A/C, I wouldn't bother with a high SEER or 2 stage. You won't get the SEER with the standard blower and you won't get proper blower speeds with the 2 stage either. Usually the most you'll get with standard blower is 14 SEER even with "15 SEER" outdoor unit.

    4 zones on a good sized furnace probably does need a bypass damper properly sized & configured.

  4. #4
    Join Date
    Jan 2004
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    Lancaster PA
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    You have a zone with only 3-6" supplies?
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  5. #5
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    Mar 2008
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    chambersburg pa
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    you do need the bypass. irregardless of what else happens to the system and it has to work properly. once the bypass is installed the a/c system is going to need a txv to take advantage of the low cooling needs of the zones. won't work properly without it unless you have freeze protection.

  6. #6

    re: Bad Dilemma...

    When the zone issue came up, the mechanical contractor told me that the additional 2 zones - would cost only a nominal amount (like +$100). Issues of pressure and fans speeds didn't come up and with all the other issues related to building the house I (unfortunately) took his word as good. (BTW: upstairs is more even and works well with our life style) Due to the relative open nature of our first floor - excepting the Den/Office, it came out uneven. We do set the 'stats to run the first floor close to each other.

    In any case, at a minimum, the bypass will be installed and a TXV used.

    Re: BaldLoonie's comment - No one has talked about anything above 4T AC unit - while we have a lot of West facing windows, the insulation job was tight (R23 walls and R60 ceilings along with a lot of foam) I agree the pressure issue needs measurement, That is why I am "considering" replacement of the furnace. As to it's properly staging the furnace, I can tell that after it has been on for a few minutes, there is definitely a step change in sound - I have assumed that was the furnace moving from 70% to 100% firing. I don't know anything about Zonex controls.

    Does your comment on high SEER and/or 2 stage AC apply if the furnace was swapped out with variable speed blower?

  7. #7
    Join Date
    Mar 2005
    Location
    Indianapolis, IN
    Posts
    241
    Wow,

    Why are you crying about the furnace? 95% A.F.U.E 2spd? What is wrong with that? Are you hoping to find 96? So your 200$ heating bill will be 198$.

    Variable speed and TXV is nicer, so what? There is always something nicer and better. So you upgrade to TEV you will recover 0.5 SEER... May be it will amount to 100$ in ten years.


    I would talk to original HVAC contractor and fix duckwork, install bypass. Complain to the builder to get your heating/cooling issues resolved. No builder will not pay for gormet, "cool" looking furnace and ac. Zonex includes LET sensor, so I would not be worried to much about "I will likely face premature component failure (blower fan, possibly compressor especially if 2 stage) and a less efficient operation."

    If you are so afraid of zoning, disconnect the panel. Problem solved.

  8. #8
    Join Date
    Aug 2007
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    MN
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    2,677
    Quote Originally Posted by browntigerus View Post
    Wow,

    Why are you crying about the furnace? 95% A.F.U.E 2spd? What is wrong with that? Are you hoping to find 96? So your 200$ heating bill will be 198$.

    Variable speed and TXV is nicer, so what? There is always something nicer and better. So you upgrade to TEV you will recover 0.5 SEER... May be it will amount to 100$ in ten years.


    I would talk to original HVAC contractor and fix duckwork, install bypass. Complain to the builder to get your heating/cooling issues resolved. No builder will not pay for gormet, "cool" looking furnace and ac. Zonex includes LET sensor, so I would not be worried to much about "I will likely face premature component failure (blower fan, possibly compressor especially if 2 stage) and a less efficient operation."

    If you are so afraid of zoning, disconnect the panel. Problem solved.
    I'm not sure on carriers but on Trane you need VS for 2 stage A/C a standard blower will result in premature compressor failure. bite the bullet now and upgrade the whole system, sell the Rheem to a friend who needs a new furnace
    You can't fix stupid

  9. #9
    Join Date
    Dec 2007
    Location
    Ohio
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    2,876
    Quote Originally Posted by browntigerus View Post
    Wow,

    Why are you crying about the furnace? 95% A.F.U.E 2spd? What is wrong with that? Are you hoping to find 96? So your 200$ heating bill will be 198$.

    Variable speed and TXV is nicer, so what? There is always something nicer and better. So you upgrade to TEV you will recover 0.5 SEER... May be it will amount to 100$ in ten years.


    I would talk to original HVAC contractor and fix duckwork, install bypass. Complain to the builder to get your heating/cooling issues resolved. No builder will not pay for gormet, "cool" looking furnace and ac. Zonex includes LET sensor, so I would not be worried to much about "I will likely face premature component failure (blower fan, possibly compressor especially if 2 stage) and a less efficient operation."

    If you are so afraid of zoning, disconnect the panel. Problem solved.
    WOW....yeah man....just disconnect it...no problem there

    First of all....the OP is talking about making a very long term investment....or didn't you get that?? If the OP would like to upgrade his furnace to a variable speed, then he should do just that! Afterall, its about the OP's comfort... I would have to say the the OP DID NOT come on here whining about efficiency, but to ask some good questions and hopefully get some good answers.....yours however was not.

    OP - You will not be able to "fight it out" with the builder....they used the "cheapest" installers they could. Any installer that puts in a 3 vent zone and never adds a bypass is not very schooled in the art of zone systems.

    But that of course is just MHO.
    I need a new signature.....

  10. #10
    Join Date
    Jan 2004
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    Lancaster PA
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    If he goes with 2 stage VS, then he can have an A/C running in first stage when one of those small zones calls, and have less chance of freezing the coil, and a lot less short cycling.
    This home owner is trying to think ahead, and get a good functional and reliable system.

    If he's lucky, that Zonex panel might have the ability to be set not to call for second stage unless 50% or all of the zones are calling.
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  11. #11
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    May 2008
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    newnan,ga
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    Need to have bypass on each zone so the air that would be flowing to those zones while there closed are directed back to the return side for reconditioning.

  12. #12
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    or one central.
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  13. #13
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    Indianapolis, IN
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    Quote Originally Posted by I_bend_metal View Post
    WOW....yeah man....just disconnect it...no problem there

    First of all....the OP is talking about making a very long term investment....or didn't you get that?? If the OP would like to upgrade his furnace to a variable speed, then he should do just that! Afterall, its about the OP's comfort... I would have to say the the OP DID NOT come on here whining about efficiency, but to ask some good questions and hopefully get some good answers.....yours however was not.

    OP - You will not be able to "fight it out" with the builder....they used the "cheapest" installers they could. Any installer that puts in a 3 vent zone and never adds a bypass is not very schooled in the art of zone systems.

    But that of course is just MHO.
    The furnace is a furnace. With proper ductwork 2spd will heat just as well as variable frequency drive. With 95AFU it is obviously extremely efficient. I don't like Zonex, nor tiny zones and no bypass. Combining Zones into two, adding bypass, or get rid of zones all together resolves most issues. I disagree that this is not a GC issue. When something not installed per spec - builder is responsible. Call builder and ask nicely to fix this mess at no cost to you. Ask them to use different contractor.

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