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HVAC Discussions - Heating, ventilation and air conditioning.
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Posted by Fred on February 15, 2008, 8:27 pm
I'm wondering if anyone can offer some advice on the best approach to
get hot water for slab heating (say, 25C) in winter, and chilled water
for dehumidication and slight slab chilling in the summer from an air
source heat pump. The project is a small (10,000 sq.ft.) commercial
building. We'd be best to size off of chilling capacity of 25 tons,
which will require some supplemental heat (likely oil-fired boiler) as
heating exceeds cooling in our climate. Anyway my problem is that the
project's HVAC engineer has experience only with air source heat pumps
that connect to air handling units and is a loss as to what to connect
to generate heated/cooled water. I'd appreciate any direction.
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Posted by Noon-Air on February 15, 2008, 11:46 pm
> I'm wondering if anyone can offer some advice on the best approach to
> get hot water for slab heating (say, 25C) in winter, and chilled water
> for dehumidication and slight slab chilling in the summer from an air
> source heat pump. The project is a small (10,000 sq.ft.) commercial
> building. We'd be best to size off of chilling capacity of 25 tons,
> which will require some supplemental heat (likely oil-fired boiler) as
> heating exceeds cooling in our climate. Anyway my problem is that the
> project's HVAC engineer has experience only with air source heat pumps
> that connect to air handling units and is a loss as to what to connect
> to generate heated/cooled water. I'd appreciate any direction.
You really need to re-think the idea of chilling the slab in summer....
think "dew point"
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Posted by Bob Pietrangelo on February 16, 2008, 11:40 am
>
> You really need to re-think the idea of chilling the slab in summer....
> think "dew point"
>
Steve,
With proper dehumidification it is easily done. I wouldn't do it up my way,
or down in your neck of the woods with out dehumidifacation, but in really
dry climates it is really starting to come into vogue.
This guy needs a HVAC com, or engineer versed in GEO.
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Posted by on February 16, 2008, 6:32 pm
Condensation in slab is a major concern, and the dehumidification
system may not compensate.
And I do agree with Bob, there are plenty of geo companies out there
willing to do the engineering for you (but they are selling their
product). The Litmus test comes down to climate, energy management
and how much your IAQ is going to suffer. You would need heat
recovery or fresh air intake.
Maybe because I live in a rain forest...just wouldn't do it..no way.
Use a HP??? Boy, I do have some other ideas I have been thinking up.
Would anyone like to start a thread on "theory"???
Where I am now: Need ductwork, heatpump and ERV to serve IAQ
requiriements and local codes on mild load days (assuming best case
Manual J scenerio). Boiler for supplemental heat in slab, using a hi
effic condensing boiler, Because slab heat runs at lower temps
without mixing valves or bypass pump. You can cool slab with heat
pump in dry climate but ...I just am not too sure if willing to loose
my IAQ, have wet carpet, have slip and falls on tile or
concrete...Obviously, I do not know what purpose this space is to be
used as or where?
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Posted by on February 16, 2008, 12:04 am
wrote:
>I'm wondering if anyone can offer some advice on the best approach to
>get hot water for slab heating (say, 25C) in winter, and chilled water
>for dehumidication and slight slab chilling in the summer from an air
>source heat pump. The project is a small (10,000 sq.ft.) commercial
>building. We'd be best to size off of chilling capacity of 25 tons,
>which will require some supplemental heat (likely oil-fired boiler) as
>heating exceeds cooling in our climate. Anyway my problem is that the
>project's HVAC engineer has experience only with air source heat pumps
>that connect to air handling units and is a loss as to what to connect
>to generate heated/cooled water. I'd appreciate any direction.
It's called a flat plate heat exchanger. It would simply go
where the indoor coil is now.
http://www.flatplate.org is one source.
I'd recommend he get experienced design help, you don't just
turn the unit on and off like you do in an air handler system. You
need a buffer tank.
As Noon said, do not cool the slab unless you pay close
attention to dewpoint - dew / mold issues.
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