[Greenbuilding] [BULK] Re: Air Conditioning for Phoenix

Sat Feb 3 11:36:03 CST 2007

Yes, I use R410a (ODP=0, GWP~1890) systems as often as possible, for the 
same reasons. And yes, I agree completely about the GWP issue -- I 
believe in Europe they use many systems that use either 
propane/isobutane as a refrigerant (ODP=0, GWP ~ 11), or C02 (ODP=0, 
GWP=1 by definition). R410a tends to create very efficient, 
extended-temperature-range heat pumps due to it's properties, but is an 
HFC with a GWP=1300. Of course, one is not supposed to be releasing 
refrigerants, so this is all very different from say Tigerfoam, where 7+ 
lbs of R134a are released for every 600 board feet, = 9100 lbs 
equivalent CO2 or nearly 5 tons of CO2 released, = about a year of 
driving or heating your home typically

Refrigerants are like insulation: there's a huge industry behind them 
that makes at least 1/2 of what you read suspect... Propane refrigerants 
were used in this country for decades, I believe, without a single death 
by explosion or fire (so I've heard -- this is in the 30's and 40's I 
think) and yet the refrigerant industry has helped create regulations 
that disallow combustible refrigerants entirely in most applications. 
They are used in large numbers in Europe, which is not typically way 
behind the health and safety regulations of this country (not any more, 
anyway!), and also doesn't appear to be going up in flames (I'm not sure 
the same can be said of this country)...

I know even less about CO2 refrigerant systems, so I'll stop there.

Disclaimer: I'd love to learn more about all this -- this is as much as 
I've put the story together so far. I'd be very interested in further 
information/corrections.

It's fascinating to me, BTW, how hard it is to get high SEER systems 
installed: Most installers will try to talk you out of them, and then 
tell you they are unavailable, if you ask for more than 17 SEER or so. I 
realize that the economics are sketchy up there, due to diminishing 
returns of high SEER systems, but it still fascinates me... I struggled 
to find an installer for a 15 SEER system 7 years ago, and that's still 
about as good as it gets on the ground. All the companies advertise 19 
and 21 SEER systems, but they are H*** to actually find. And this is 
still true after I say "I don't care what it costs, at least give me a 
quote." Very weird.

Warmly, Keith

George J. Nesbitt wrote:
> Thank you Keith.
>
> Perhaps I was too concise.
>
> SEER rating is better suited for the more humid east (north and south) 
> coast, where dehumidification is more of a concern, and outdoor 
> temperatures aren't as high as in the west. EER is more important out 
> west where dehumidification is less of a concern, and outdoor 
> temperatures can be 95 deg F and higher. 2 machines with the same SEER 
> can have very different EER's.
>
> I did not mean CFC's. When we switched from CFC's to HCFC's and HFC's 
> we reduced the Ozone depletion potential, but didn't reduce the Global 
> Warming potential (I posted on this some time ago). The exception is 
> R-410, I didn't realize this is a HFC (I am EPA Certified, but that 
> doesn't mean I know and understand the chemistry), that you for 
> correcting me.
>
> Unfortunately I am installing 2ea R-22 air conditioners rite now, my 
> supplier didn't stock R-410 TXV models, and I don't want to have to 
> replace them, and couldn't wait to order them. I would like to use 
> R-410 only in the future.
>
>
>
> Keith Winston wrote:
>> Hi George! You make a lot of concise, good points. A couple 
>> additions/modifications (I know you know most of this, it might be 
>> helpful to others):
>>
>> Your EER/SEER comment is a good one. The Fujitsu 21 SEER mini-split 
>> heat pumps I mentioned are 12.5-14.5 EER, depending on size and mode. 
>> Which is respectable. Also, Lawrence, they are high efficiency heat 
>> pumps in heating mode (HSPF 10.5-11), which helps with your heating 
>> problem... They work down to very cold temperatures, so in that 
>> climate they aren't even working hard in heating mode. I see that 
>> they're only rated to cool to 115, though when I look at the 
>> performance curves I imagine they'd work above that, but they are 
>> already derated to 75% capacity at 115. I can send those to you if 
>> you want, it was hard to get them. Okay, end of advertisement!
>>
>> R410a is a near-azeotropic HFC blend (maybe you meant "No CFC"?). 
>> Which is about as good as you can do, refrigerant-wise. It has no 
>> scheduled phase-out, since it has no Ozone Depletion Potential (ODP), 
>> but it still has a Global Warming Potential (GWP) of about 1600, 
>> which means that if a bit over a pound escapes, it's equivalent to a 
>> TON of CO2. (Note: there are a lot of regulations covering the 
>> release of refrigerants. So this issue is not the same as, for 
>> example, Tigerfoam that I wrote about a couple weeks ago, where 7 lbs 
>> of R134a [HFC, 0 ODP, 1300 GWP] is NECESSARILY released for each 600 
>> board feet of product, with a GWP of 1300 resulting in about 5 TONS 
>> of CO2 equivalent, or as much as many of us release in a year of 
>> driving, give or take). R22 is of course an HCFC, which is scheduled 
>> to be phased out for new uses in 2010, and all uses in 2020.
>>
>> I'm not intending to be nit-picky, just clarifying.
>>
>> Keith
>>
>>
>> George J. Nesbitt wrote:
>>> *GREEN COOLING*
>>>     Fix the *building shell* first as much as possible.
>>>        1. Cool roof would be high on my list, but if you need 
>>> "approval" then it might not happen. If you insulated the roof 
>>> underneath then the benefit is too society in reducing the "heat 
>>> island effect".
>>>        2. Radiant Barrier, if you have to have a darker roof and if 
>>> you don't insulate the roof, than I absolutely recommend a radiant 
>>> barrier (help keep the attic and ducts cooler). Roofing is starting 
>>> to be made in darker coolers that have reasonable cool roof properties.
>>>        3. Insulate the roof, to bring the attic and ducts into 
>>> conditioned space, either by placing rigid (polyisocyanerate) on the 
>>> roof deck, or spraying foam (cellulose would also work in phoenix) 
>>> on the underside of the roof deck.
>>>        4. Windows, add low e film, overhangs, trees, replace, etc. 
>>> to reduce unwanted summer heat gain.
>>>        5. Air leakage reduction never hurts. Build tight, ventilate 
>>> right.
>>>        6. Paint the house walls a light color.
>>>        7. Insulate the walls if they aren't already.
>>> Now for the *mechanical.
>>>        1. *Manual J or ASHREA 90 room by room load calculation 
>>> (accurate).
>>>        2. Manual S equipment sizing calculation, don't add size, if 
>>> anything the load calculation is as much as 1/3 to large. Don't 
>>> oversize.
>>>        3. Manual D duct design.
>>>        4. Manual T grill/register design.
>>> Now for the *equipment.
>>>        *1. Swamp cooler, the oasis is the best, direct, indirect 
>>> evaporative cooling. Developed with funding from the California 
>>> Energy Commission, and Davis Energy Group.
>>>        2. There is another one, but can't think of it's name at the 
>>> moment.
>>>        3. Split system refrigerant cooling. Forget SEER, it is 
>>> tested at 82deg F outside temperature, and 50% RH, you want a high 
>>> EER, tested at 95 deg F (still cool for Phoenix). The higher the 
>>> outdoor temperature the lower the EER (or SEER for that matter). 
>>> Stay away from the 2 stage condensers, they aren't as efficient on 
>>> high. (better to under size and let it run longer). Install an air 
>>> handler (furnace?) with a ECM variable speed motor. Install a return 
>>> duct to the outside for fresh air, and run air handeler 24/7 (or a 
>>> percentage of the time) on low speed (60-80 Watts).
>>>        4. Water cooled split system. Consider the Freus, and there 
>>> is at least one other, hight EER even at higher outdoor temperatures 
>>> (although some loss).
>>>        5. No HFC, HCFC refrigerants, use R-410A (Puron is one trade 
>>> name). The Freus is R-22.
>>> Now for the *Installation*.
>>>        1. R-8 duct insulation, especially if the ducts are in the 
>>> attic, R-4 if they are in conditioned space.
>>>        2. Insulate the plenum's, and the air hander too.
>>>        3. Install the ducts and test to less than 6% of design 
>>> airflow (400cfm/Ton cooling, ie 12,000 BTU's).
>>>        4. Test the airflow with a Trueflow to check for 
>>> 400-450cfm/Ton cooling.
>>>        5. Braze the refrigerant lines with an oxy-acetylene torch, 
>>> using 15% silver solder, and run nitrogen in the lines.
>>>        6. Put the refrigerant lines under a vacuum to 500 microns, 
>>> and not less than 800 after 15 minuets.
>>>        7. Verify the charge using Subcooling (install a TXV).
>>> Now for the *operation.
>>> *       1. Use a programmable thermostat, try to live with not less 
>>> than a 78deg F indoor temperature.
>>>        2. Enjoy comfort without breaking the bank, or killing the 
>>> planet.
>>>
>>>
>>>
>>> Keith Winston wrote:
>>>> Hi there,
>>>>  
>>>>> I'm going to push the limits of what he can handle as it is.  A metal
>>>>> roof makes a lot of sense in Phoenix, and that is the second part of
>>>>> this project that I didn't mention.  Living roofs are great, but 
>>>>> involve
>>>>> structural mods that I'm not willing to consider on someone else's
>>>>> house.        
>>>> What about: put your metal roof on purlins (not all mftrs allow it, 
>>>> but some do) to create an air channel underneath, vented top and 
>>>> bottom (hopefully it's a simple roof -- include insect barriers in 
>>>> the vents). Use a radiant barrier under it, pointing up.
>>>>
>>>> Insulate the roof from within the attic with spray foam, in the 
>>>> meantime sealing up the attic so if there are any ducts in there 
>>>> they are inside the envelope. Sorry, he has to move the nesting 
>>>> dolls. Check with your local foam contractor to see how 
>>>> willing/able he/she is to work around crap, but probably it needs 
>>>> to be empty. Hire a few young people to clean it out! Leave the 
>>>> insulation that is probably already on the floor, to make the attic 
>>>> a lightly conditioned space. Then you get the reflective metal 
>>>> roof, a radiant barrier properly installed, a convective air space 
>>>> to keep the whole assembly from getting TOO hot, a tightly 
>>>> insulated roof, interior ductwork... have I missed anything?
>>>>
>>>> Say, did you ever find indirect evaporative coolers? We can't 
>>>> really use them here in DC, too humid. I see that Mastercool has an 
>>>> indirect modification available 
>>>> http://www.adobeair.com/masterCool.html, I can't find it on their 
>>>> website but call and ask them. The other one is here: 
>>>> http://www.oasysairconditioner.com/, which looks impressive.
>>>>
>>>> Another possibility is a Freus water cooled evaporative air 
>>>> conditioner, quite different from a direct or indirect/2 stage 
>>>> evaporative cooler. It is a compression-cycle machine that uses a 
>>>> spray of water on the condenser coils to improve performance.
>>>>
>>>> http://www.freus.com/
>>>>
>>>> They don't have a good website. You'll probably gain more 
>>>> information here:
>>>>
>>>> http://www.toolbase.org/TechInventory/TechDetails.aspx?ContentDetailID=793&BucketID=6&CategoryID=6 
>>>>
>>>> http://ezinearticles.com/?Evaporative-Water-Cooler---This-Water-Cooled-Condensing-Unit-Is-No-Swamp-Cooler&id=269729 
>>>>
>>>> http://www.ecosmartinc.com/productdocs/1-Freus-Overview.pdf
>>>>
>>>> I'm not sure whether it makes more sense to use less electricity, 
>>>> or spray the Ogalala into the air to be whisked away...
>>>>
>>>> Also, I have used/installed the Fujitsu 12RLQ mini-split heat 
>>>> pumps, which are 21 SEER units. If you have an open floor plan and 
>>>> can get away with just one or two sources, it's a good prospect. Of 
>>>> course, you may need to consider ventilation, though with swamp 
>>>> cooling it's part of the picture. See if an HRV is justified in 
>>>> there, it might remove a bunch of the moisture while still cooling 
>>>> makeup air. I like the Venmar units.
>>>>
>>>> Warmly, Keith
>>>>
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>>>>
>>>>   
>>

-- 
Keith Winston
Earth Sun Energy Systems
Hyattsville, MD 20781
301-980-6325
send me mail at 
keith at the company below
www.EarthSunEnergy.com