CUSTOM DIY GEO AC need help from fellow members !!

Discussion in 'HVAC Heating & Cooling' started by Jin, Jul 28, 2012.

  1. Jin

    Jin New Member

    Jul 28, 2012
    Firstly, hi all!
    Very very nice and informative forum! wish i would've found this one earlier in my new house history :p

    I will try to stay brief on an otherwise very long thought and list of details so my thread is readable for others.

    I have design/built my house, started approx 4 years ago ( started design actually 6 years ago i believe )
    Did not thought much of the AC, but i managed to get 2 loops of ~ 1000' of 1/2" o2barriere PEX at 6' of depth
    while we were excavating the front ( it is laid in a S pattern in a 6' depth trench of approx 40' wide by 100-110' long )

    house is a pretty large ( almost 2Ksq ft floors ) isolated concrete forms from bottom to top
    with alot of large windows ( 3 panes double low 2 double argon )
    but we are surrounded by large and high trees ( the highs are all deciduous, and lower are coniferous
    i have yet to install all sunshades, but some are already installed which seems to help a little

    Until we hit the 26-28C mark of day temp at the begining of this summer,
    the house was extremelty comfortable with a super stable temperature oscillating between 19c during high and 23c during daytime

    then we hit the hot days, and it has been very hot since ( a month now ) slowly cooling from cooler days

    i rushed to start up my simple AC using the geo loops, which i thought would be good for at least the 25c days and cooler
    but it is barely

    so now i must add up some cool input and that is where i need inputs from fellow members, so make sure i take the correct decision

    here is a summup of the current installed system :

    - Heating is all electrical infloor, so we need not to take care of the heating ... ac only

    - geo system recirculates 1000liters ( 250g ) of water ( will change liquid once i am set .. alcool or glycol ??? )
    through the 2 pumps in the 2 ground loops ( i know,,shoyuld've installed 3/4" ..but i had this 2000' of 1/2 pex laying around when i decided back then .. )

    - water is circulated in a furnace radiator ( 20"X20" X 3-4" thick...150K BTU for heating..but not used for that here..but looks efficient enough )
    with a circulatory pump, from the 1000liter reservoire

    - incoming air from basement is sucked through filter / radiator by 6 4" Vortex fans that lead to different rooms and sections of the house through white 4" PVC piping
    ( no heat so i can use pvc and its good insulation properties :)

    My design goal was/is to be able to control flow for different rooms through the thermostats located in each rooms
    ( i've got heat/cool Zwave thermostats in each rooms )
    so we can strive to get a good balance of temperature in different situations instead of having a colder basement
    and too hot rooms on 2nd floor
    some rooms share the same 4" duct, but will install some 12V servos that will work an induct restrictor plate that will help direct higher flow to the room
    that will require it ...
    also fans will be dual speed controlled ( circulating speed always on, and goes to full speed only when a room in this line requires cooling ..cycling it using cascade of relays )

    i've got a Venmar air exchanger that i have yet to decide how to install
    will need input on this also please

    So i thought i could either do the followings :

    - get some water chiller ( or use a copper coil with a regular AC compressor ) and cool down my 1000liter energy dump
    so i can fully use the radiator effectiveness, and the current system with fully independent room functions

    -or add on a 4-5ton AC either before or after the radiator ( shall discuss this later ...installing it after radiator will be much more work for me because of current space issues .. )
    which would somehow limit the seperate room control but would cool all of the house

    -or add 2 3ton AC independently , one for 2nd floor box ( i already have a seperate manifold for 2nd floor lines ) and 1 for first floor
    which would at least give some better control of first vs 2nd floor temps

    Currently, the setup is not fully done so i use the air in the machine room and garage ( don't cars in there yet ..still full of tools and plywoods :p )
    and i leave the door open to basement for the air return
    so air gets in the system at 24c-26c
    and leaves it at 20c-22c
    water temp in the reservoir was in the 12-13c range a few weeks ago
    but now with accumulated heat from 2-3 weeks at 28-30c outside, it only gets down to ~ 14-15C during night
    and up to 18c during daytime when the system is in use

    obviously, i dump something like 3-5C of air temp at approx 800cfm in the heat dump system only

    could obviously be much better if water temp was lower ( seen 18-19C output when water temp was 12C in reservoir )

    but enough talk,
    i will let some helpfull souls digest all the info
    and will put some pictures of the system in the next post

    Please let me know what you guys recommend i do !

    I favor comfort before anything else,
    but i am no dumb, and i hate overpaying for simple things i can do myself

    cheers all! :)
  2. Jin

    Jin New Member

    Jul 28, 2012
    image008.jpg image002.jpg image003.jpg image005.jpg image009.jpg
    here are some quick pics
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  4. Ralphxyz

    Ralphxyz New Member

    Jul 28, 2012
    Long Island, NY
    Hey Jin, interesting concept!

    What is the water heat gain across your heatexchanger?

    Water input temp/output temp?

    Have you done any thing to maximize the heat gain (gpm flow/speed)?

    Then what is your heatexchange rate of you air flow?

    Sorry if you said this and I missed it.

    Obviously you have to maximize you heat exchange to get what you can from your existing setup then you can look at adding additional equipment.

    Have you thought about a ground source heat pump?

  5. Jin

    Jin New Member

    Jul 28, 2012

    approx 800CFM

    heat gain ?

    i'll state exchange as an example :

    outside temp from 21C to 30C
    intake temp @ 25C
    water temp starts in morning at 13C gets up to ~18C in evening
    output air temp from 20C to 23C

    so i basically get from 2 to 4c of cool gain
    @ 800cfm

    not enough for the summer time
    enough for all other

    Right now i'm looking to purchase 2 condensors and 2 evaps from younits dot com
    reliable site??

    probably goodman or amana

    would be 2 3ton kits at 14seer

    would install 1 kit asap on the 2nd floor duct
    and next year would install second kit on 1st floor duct

    so air would come through intake,
    pass through my geo setup radiator ( loose 2-4C degrees )
    all the time

    and when AC is required AC would turn on and air would get cold for either first, second floor or both

    would control rooms with fan speed and servo traps

    good idea?

    simple and cheap on my side !!

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