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  1. #1
    Join Date
    Dec 2003
    Location
    45th Parallel
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    957
    My Wife and I are building a house this spring and I have been kicking around ideas on the HVAC system.
    We live in the country so, no Nat. Gas available, electric only. Looking at a heat pump with electric strips.

    What do you guys think would be better:

    1. Package unit with economizer, would like the free cooling it offers. Gets down to low 60' upper 50's at nite hear in the summer. But then I am not real impressed with the quality of workmanship on the Precedent units. Mainly in the economizer section, IE: Damper sealing,and smoothness of operation.

    OR,

    2. Split system heat pump with OA damper at indoor coil to utilize OA if cool enough. I realize it would be more work and controls, but may be worth the money in reliability.

    What have you guys seen in the residential arena, I do not do residential service, so I am all ears. Do you see economizers at all, or am I going down the wrong track? Thanks for the input.



    [Edited by drivewizard on 02-11-2006 at 01:42 AM]

  2. #2
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,429
    Originally posted by drivewizard
    so, no Nat. Gas available, electric only.

    What do you guys think would be better:
    1. Package unit with economizer, would like the free cooling it offers. Gets down to low 60' upper 50's at nite hear in the summer.
    OR,
    2. Split system heat pump with OA damper at indoor coil to utilize OA if cool enough. I realize it would be more work and controls, but may be worth the money in reliability.

    Do you see economizers at all, or am I going down the wrong track? Thanks for the input. [drivewizard on 02-11-2006 at 01:42 AM]
    1. Location ?
    .. $avings?

    2. Would it cost > several $100s
    to add a ~500 CFM OA fan with outdoor t-stat set at 63'F in series with indoor t-stat set at ~70'F?

    ie. Model FX12
    http://www.fantech.net/fx2.htm

    + run A/C with humidistat
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  3. #3
    are you talking ddc controls or what. youll need a humidistat and controls to operate the oa damper because there a point in which to much humidity would be introduced with outside air. residential companys do not do ddc controls. except for canned packages maybe but i doubt it.
    also dont go with anything less than variable speed on the inside unit. you cannot get above 13 seer without realisticaly, and if 15 yrs down the road want to go higher seer than 13 youll have to replace the inside also.

  4. #4
    Join Date
    Mar 2004
    Location
    Vancouver, BC
    Posts
    125

    The envelope

    The most cost effective bang for the buck is to design the house envelope and windows properly first to minimize the heating and cooling loads in the first place. The envelope is the primary HVAC system of the building- design it to minimize thermal bridging in the walls and roof, eliminate infiltration, use high performance windows with shading that will keep out the summer sun, but allow winter sun in for passive heat, and then start looking at applicable HVAC systems. Once the heating and cooling loads are minimized, the cost of an HVAC system is going to be a lot lower, you'll use much less on-going energy, and you will have a lot more options for indoor comfort systems (not HVAC systems).

  5. #5
    Join Date
    Dec 2003
    Location
    45th Parallel
    Posts
    957
    I am not as concerned about energy savings with the economizer as I am with air quality. My wife says she needs fresh air, cuz I fart to much!
    I have a used 20 point PCM that I could use for the control of dampers.
    How does a variable speed indoor fan work? Does it monitor Condensing pressure? How would you keep head pressure within limits if fan speed was to low?

    As far as humidity, our RH levels are very low when it is warm/hot outside. Our RH is only high in winter when it is to cold for cooling anyway. Oregon, Willamette Valley area.
    I would probably just have a minimum position during high RH times. I could incorporate a Temp/RH transmitter into the PCM as an analog input.

    Thanks for the Fantech link, now you got me thinking about HEPA filters. Do you see many of those used, in Residential? Any issues to be aware of, other than monitoring pressure drop. How much if any do you need to upsize fan size to overcome additional press drop?





  6. #6
    Join Date
    Jan 2002
    Location
    East Grand Forks, MN
    Posts
    1,375
    Now, when you say OA, do you need to cool the house down? you did say cost was not important, what about mechanical cooling instead.

    secondly, maybe you just need the OA for fresh air FA instead of free cooling? is this right, you did say your wife wants FA.

    I suggest HRV/ERV with a Heatpump. You get your fresh air and energy efficiency at best especially out there in the green country.

  7. #7
    Join Date
    Dec 2003
    Location
    45th Parallel
    Posts
    957
    "Now, when you say OA, do you need to cool the house down? you did say cost was not important, what about mechanical cooling instead.

    secondly, maybe you just need the OA for fresh air FA instead of free cooling? is this right, you did say your wife wants FA.

    I suggest HRV/ERV with a Heatpump. You get your fresh air and energy efficiency at best especially out there in the green country."

    Yes, I will need to cool the house down, If it is 60 deg outside, and I need cooling why run the heat pump if I could bring in OA, also would like to be able to bring in some fresh air each time the unit runs in Htg or clg. Will need some fresh air as I plan on making sure house is very tight.

  8. #8
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,429

    Overall H V AC Requirements ?

    Originally posted by drivewizard
    I am not as concerned about energy savings with the economizer as I am with air quality. My wife says she needs fresh air, cuz I fart to much!

    As far as humidity, our RH levels are very low when it is warm/hot outside. Our RH is only high in winter when it is to cold for cooling anyway. Oregon, Willamette Valley area.

    I would probably just have a minimum position during high RH times. I could incorporate a Temp/RH transmitter into the PCM as an analog input.

    Thanks for the Fantech link, now you got me thinking about HEPA filters. Do you see many of those used, in Residential? Any issues to be aware of, other than monitoring pressure drop. How much if any do you need to upsize fan size to overcome additional press drop?

    House size __ ?

    Merv 8 to 11 filter should be MORE Than sufficient for
    nearly ALL health concerns.

    Very simple to have a nice, simple Outside Aire set-up in your mild environment.
    Recommend

    ..Fantech at ~ 400 CFM
    + 40% efficient filter
    + speed controller
    + pre-heater to provide ~65'F air.

    Q= CFM * dt * 1.08
    = 400 CFM * (65'-35') * 1.08 =
    = 12,960 BTU
    = 3.79 kW for pre-heater capacity

    or

    Whole House Fan
    http://www.farreys.com/ventilation/v...an_direct.html

    OR "Guardian Plus" if you really need a
    complex filtration system.

    http://www.farreys.com/ventilation/b...ier/index.html

    FIRST STEP
    Study SALEM, OR Weather
    Heating Degree Days (H.D.D)
    Cooling Degree Days (C.D.D)
    Year H.D.D C.D.D
    2005 4,567 316
    2004 4,334 382
    2003 4,220 435
    2002 4,710 320
    2001 4,732 199
    2000~4,700 300
    1999 4,726 262

    In other words, Heating is MUCH MORE Signficant
    load than Cooling.

    Send plans & window schedule
    (.DWG file via e-mail = most convenient) if you need a specific heat pump sizing.

    [Edited by dan sw fl on 02-11-2006 at 04:00 PM]
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  9. #9
    Join Date
    Dec 2003
    Location
    45th Parallel
    Posts
    957
    Dan, I appreciate your enthusiasm, but right now I'm just lookin at general ideas.
    I am getting the impression that economizers are not used much, or at least not by the guys reading these posts.
    Also, that in line HEPA filters are probably not advised due to high delta P, and increased fan HP required. But possibly a side stream HEPA would be OK. Thanks for the links, probably would be more cost effective to go with a Whole house fan for the free cooling and fresh air(as needed). Then just go with a good split system heat pump for the rest of the usage.
    Thanks, for the help, I think I have enuff info to get me going down the right path now.


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