Posted By Rosalinda on 16 Mar 2012 10:24 PM
It is probably also much easier and faster to install air source than ground source and more doable from a DIY standpoint. Given the right floor plan I can see air source as being much more feasible than ground source and the cost difference is huge, definitely in the air source's favor.

Not every system will work in every situation, but with air source becoming more efficient, it definitely should be considered close to the top of the list for heating and cooling systems.

-Rosalinda

While there is less work in installing an air source anything, that does not necessarily make it easier. DIYers are often more comfortable with geo piping than brazing refrigerant lines. Futrther many of the air source products listed are not available to DIYers.

I absolutley agree with the second half of your premise.

Posted By Looby on 17 Mar 2012 01:29 AM

Posted By ICFHybrid on 17 Mar 2012 01:06 AM
Sometimes the terms "Puget Sound" and "Puget Sound and adjacent waters" are used for
not only Puget Sound proper but also for waters to the north, such as Bellingham Bay
and the San Juan Islands region.

Yeah, whatever. Sometimes the term "Philly 'burbs" includes Wilkes-Barre, Scranton, ...

...and Sault Ste. Marie.

Looby

What's the commute time between Sault Ste. Marie and Philly liike, anyway?

The location that promted this thread was and is Wayne PA, the climate comparator I've been using for Port Orchard & Whidbey Island, where I have at least some first & second hand data on mini-splits.  Yep. it's colder/drier in Wayne than the inner waters of WA, but not a lot colder.  Again, the differences are without distinction from a heating degree day or design temp point of view for any of the inland waters inside the Strait of Juan de Fuca, despite dramatic differences in rainfall.

Having spent winters in both the Netherlands and  Bremerton, I'd be inclined to say Bremerton has more of a North Sea climate in winter (albeit less windy) than any mediterranean location.  The weather data bears that out as well (38F average mid-winter temp in Amsterdam.)  Summers in Bremerton can be somewhat comparable to some Mediterranean locations though.

FWIW: Port Orchard had a nice little snowstorm in excess of 14" all in one go this winter- unusual, (record breaking in some locations), but snow, even substantial snow events are not super-rare in this region, despite the relatively warm January temps.

Posted By ICFHybrid on 16 Mar 2012 08:17 PM

do you recall the phrase "troublesome ground loops" that you believe (or just try to get others to believe) are commonplace?

The phrase refers to the ground loops that are a constant source of discussion in this very forum.

In 2 minutes of casual (as opposed to in-depth) searching for problems with mini-split (ductless) systems, I have found the following:

http://www.ductlessguide.com/mini-split-air-conditioner-leaking-indoor-unit.html
http://www.ductlessguide.com/problem-air-conditioner-freezing.html
http://www.ductlessguide.com/mini-split-unit-operates-cool-fix-problem.html
http://www.ductlessguide.com/mini-split-air-conditioner-start.html
http://www.ductlessguide.com/indoor-evaporator-fan-working.html
http://hvac-talk.com/vbb/showthread.php?t=146948
http://www.doityourself.com/forum/air-conditioning-cooling-systems/304994-mini-split-problems-turns-off.html
http://www.thedieselstop.com/forums/f102/amcoraire-mini-split-problem-anyone-know-about-these-258588/
http://appliancejunk.com/forums/index.php?topic=6234.0

So, based on your philosophy, I suppose these (and lots more) problems equally represent the unreliability of ductless systems, eh?

This thread is getting weird. Air source and Ground source are both great.

Mini splits have there place, but it is not in the typical home.

The future of Air source equipment is likely Air to Water units with sealed refrigerant circuits. These units do however require low temp emitters and a sound pumping strategy. If done well they will perform in the northeast winter. Unit life will vary greatly though.

Ground source done well is outstanding in efficiency and comfort. These are thing that are worth paying for. That's why people do it.

Maybe this thread can be steered back towards a healthy debate of where and when air source or ground source might make the most sense.

Posted By Dana1 on 17 Mar 2012 10:46 AM
Yep. it's colder/drier in Wayne than the inner waters of WA, but not a lot colder.

Despite your best efforts to fudge the numbers, the 99% design temps
for the Philly area are nearly 15°F lower than for Seattle and environs.
Here are the figures from the source that YOU referenced, upthread:

West Chester, PA ................................. 13°F
Reading, PA ......................................... 13°F
Philadelphia, PA (AP) ......................... 15°F
Philadelphia (Willow Grove NAS) ......14°F
Wilmington, DE .................................... 14°F
Lancaster, PA ......................................... 8°F

Bremerton, WA ...................................... 25°F
Seattle, WA (CO) ................................... 28°F
Seattle, WA (Boeing Field) .................. 28°F
Seattle-Tacoma AP ............................... 26°F
Everett-Paine AFB................................. 25°F

WRT degree days, although Philly is colder, Seattle's
winters are significantly longer. Again, according to
the Weatherspark.com source that YOU posted:

Blue Bell, PA: "Cold season lasts from Dec 2 to Mar 3."

Bremerton, WA: "Cold season lasts from Nov 13 to Mar 3."

A longer milder winter IS_NOT_EQUAL_TO a shorter colder winter.

A statistician (or an air-source jihadi) can have his head in an oven
and his feet in ice, and he will say that on average, he feels fine.

the technology sounds great and seems to work well in a dry testing lab at sub freezing temperatures, it really becomes problematic when low ambient temperature occur together with high humidity conditions, or rain.

I'll just refer back to the part of the OP that seemed to be the thrust of what was being said. I quoted it above.

In terms of cold conditions AND humidity, the Pacific Northwest is a very good location to examine how air source heat pumps perform. We hover just above freezing for much of the Winter and there always seems to be moisture present. When we have drizzly rain at 34F in the winter, it is not uncommon to meet a resident of Fairbanks who is pining for his more comfortable home where the temperature is almost certainly sub-zero. The difference, of course, is the humidity. That having been said, heat pumps perform well here despite the fact that the outdoor coils are at an even lower temperature than ambient. Heat pumps such as the Daikin Altherma which I have installed, have a reversing cycle that operates seamlessly to keep the outdoor unit from freezing.

Even though I have accessible acreage on this build, I am pleased that I don't have to have a ground loop. It just adds another layer of issues. Not too far from here is another home that a Daikin unit (instead of a geo unit) went into after talking to us. We've had a lot of "extreme" weather this winter and that unit is performing even beyond the estimates and they saved HUGE on what would have been a difficult ground loop to begin with.

A gshp muhajidin can have his head in his a** and .... well, enough said.

The future of Air source equipment is likely Air to Water units

IMO, the present and future of air source heat pumps is air to air units (in terms of number of units sold).

I'm late to this party, but I'd like to add some fuel to the fire.

1) The great strenghth of ductless is the lack of duct losses associated with duct air leakage and heat loss / gain through the duct walls wherever ducts exist in unconditioned spaces (Ductwork in unconditioned spaces is lunacy, but I digress...)

1a) A corollary of that is greatly reduced blower power associated with near zero static pressure, giving rise to very high SEERs EERs, and COPs

1b) The moment a ductless system brand is asked to act like a ducted system, pushing a bit of air a few feet through a duct to an adjoining room, SEERs plummet to the mid teens despite only providing a few hundredths to a tenth of an inch or so of available static. Ductless simply won't cut it in broken up houses wherein we need 20 CFM into a pantry, 15 CFM into a commode closet, 30 CFM into a walk in closet, etc.

2) The minisplit manufacturers have clearly better integrated control of compressor speed, indoor blower spped, and possibly outdoor fan speed in order to optimize performance at temperatures well below freezing as well as providing capacity turndown far in excess of the 70% / 100% capacity split offerred by a typical two stage system. Split system manufacturers have finally taken notice - the Nordyne IQDrive and now the Carrier GreenSpeed offer variable speed compressor. Carrier's system is especially noteworthy in that it offers HSPFs up to 13.

3) The Achilles heel of any air source system has to be the need for defrost cycles. In all the wrangling over climates above scant heed seems to have been paid to winter humidity. I gotta figure a cool damp climate, say one with dewpoints in the 30s and drybulbs in the 20s will cause more and longer defrost cycles than drier climates, even those with lower dry bulb temperatures...comments anyone?

Posted By ICFHybrid on 17 Mar 2012 01:20 PM
Even though I have accessible acreage on this build, I am pleased that I don't have to have a ground loop. It just adds another layer of issues.

Posted By ICFHybrid on 08 Feb 2011 05:49 PM

BTW, I do own a geothermal system and have now installed the field all by my lonesome in the bitchiest weather in recent history.

ICFHybrid, lie or withhold pertinent information much?

Perhaps you would enlighten everyone as to the troublesome loop problems you experienced by installing your own loop with your personally subcontracted, piecemeal, geothermal help which you spoke so highly of (from a cost saving standpoint) in the thread "Why do Geothermal Systems cost so much"?

scant heed seems to have been paid to winter humidity.

Isn't that why someone introduced the examples from the Pacific Northwest? We seem to excel in winter humidity.

a cool damp climate, say one with dewpoints in the 30s and drybulbs in the 20s will cause more and longer defrost cycles than drier climates

Daikin is one company that publishes integrated performance values for it's air source heat pumps. The integrated values go all the way from nominal performance levels down to performance levels at -4F for the Altherma unit, for example. Integrated values show performance which takes into account the defrost cycles. With the tables, you don't have to speculate about it.

Curt, let me ask your thoughts on this. I have a sealed 5x5x20 shaft ducted to pull air out of my great room and circulate it to three rooms and two baths. 6 inch ducts, all in conditioned space. Low speed continuous fan up to 200 cfm. Manual adjustment. The purpose is mitigating passive solar overheating but I am thinking why not put a ductless indoor unit in there as well. I need cooling for three months -- dehu really because thermal mass handles sensible pretty well. I need heat for six weeks or so in the fall before the leaves drop. There are no hot spots in the house and conditioning changes slowly because of all the concrete in the house. No reason air to air trickle charging wouldn't work as well as radiant heat if an inverter Hp works in this scenario.

we need 20 CFM into a pantry, 15 CFM into a commode closet, 30 CFM into a walk in closet, etc.

Put your HRV exhausts in these small places to draw household warmth in before discharging.

Posted By toddm on 18 Mar 2012 08:25 AM
I need cooling for three months -- dehu really because thermal mass handles sensible pretty well. I need heat for six weeks or so in the fall before the leaves drop. There are no hot spots in the house and conditioning changes slowly because of all the concrete in the house.

Well I'm not Curt but.....
I don't think any of us are suggesting minisplits don't work todd, the debate has more to do with efficiency and efficacy in certain conditions.
Worse case scenario is a minisplit may have to use auxiliary strips. In no case are they non functional.
Yours may be the perfect application for this technology.

Interesting thread...
On my new build to be starting soon, I have been down all of these roads, a dozen different times. Mechanical units, shell types, etc. Everything from Double stud, SIPs, thick foam and ICF. Mini splits, standard furnace, typical air to air and geo. Location is north eastern Iowa, zone 6. Design temp is negative teens, but winter temps hang out in the single digits most of the time and low 20s. I have settled on ICF and probably geo. Yes, I realized I have selected most likely the highest costs combined system possible, but there are reasons. Obvious the air tight and efficiency of ICF is nice, but the sound and strength (been in 10 tornados in the last couple years, including an F5 a few years ago was just 2 miles away). But geo because it is pricing out to be CHEAPER then a 16+ SEER air to air HP. I have ruled out the mini splits due to the need for multiple hyper heat units and heads, plus a ducted HRV, made the price only a couple k below the net geo price.
The net geo price after fed credits and local rebates works out to be about $10,500 for a 3 ton waterfurnace unit with vertical wells. The financing has worked out with the bank to include the net cost in the home loan, and we will do a line of personal credit for the difference. Once the rebates arrive, the line of credit is paid off thus we are not increasing the mortgage cost due to the geo. Settled on this not only because of the price, but the efficieny at all out door temps is there as well as the comfort. This will be well worth the couple extra k spent.
Not system is perfect as it has been clearly pointed out here. Pros and cons will be with anything in this world. Geo for a heating dominate climate can make good sense, however mainly to credits and rebates offered. If they did not exist, then obviously the air to air route would win even with cheap gas prices in our area.
The point is

Won't argue with what Joe wrote on my behalf

Hard to know what might work w/o more information...5x5x20 shaft...5,5,and 20 whats??? Off the top of my head it will take an itty bitty mini split (do they make micro splits?) able to be happy with sub 200 CFM of air.

lzerarc - if there is a question buried in all that, let us know, preferably in a dedicated thread. Other than that, your reasoning seems sound. It is a pleasant luxury to be able to start from scratch and pick all the good stuff available in new construction these days. My house (2008) is similar to what you describe except that it is in North Florida. 3400 SF heats and cools for $40 / month; total energy bills around $1300 per year, including well and septic pumps (no water or sewer bills, either)

no question really, but I see my response was cut off at the end for some reason.... Really just comments was all, from a cost perspective. Geo is not always really expensive...in my case, cheaper then a standard air to air.

Posted By Dana1 on 16 Mar 2012 02:29 PM
In regards to COP increases with modest oversizing, see figure 5, page 10 of this document.  

At 17F at mid speed it hits COP about 0.5 higher than running fully flat out. 

At 35F at low speed it hits a COP about 0.5 higher than running at mid-speed

In the sample location under discussion the  outside design temp is 15F, the average mid-winter temp about 33F.

If  25%-50% oversized for the heat load at 15F it will run between low and mid-speed at 33F, and between mid and high speed at the 15F design temp.

If sized exactly for meeting the heat load at 15F it'll only pull a COP of 2.1 at design temp rather than 2.5+, and at the average 33F winter temp would only pull 3.5 compared to 4+.  If oversizing a half-ton is even possible, it's worth it.

If you grossly oversized it (which is hard to do, if you have anything but a super-insulated house) you'd get a COP of nearly 5 at 35F by only running at low speed, but between the wind chill of the higher cfm  blowers on the interior heads  at min-flow and the short-cycling, would make it less comfortable.  These are fully modulating systems, but the turndown ratio isn't infinite.   When oversizing a ductless for higher efficiency 50% would be about the limit of what makes sense from a comfort/effciciency point of view.  br />

First I was looking at the document you had cited. And figure 5, page10. It compares a 1 ton heatpump under certain load conditions. it shows that the same heatpump with the same compressor load runs more efficient, because the power to run the fan higher outpaces the higher efficiency with higher air flow. So what is new? That does not mean that if you now take another, larger unit (oversized) that it will run more efficient.
PLus there is so much inconsistency in the figure, that I actually question the results and the accuracy of the measurements.
Lets say the intermediate compressor with the low fan at 47F has higher COP that the same intermediate compressor with low fan at 63F. Makes no sense.
Or there is no difference for high compressor/high fan between 7F and 17F. Very unusual.

The next report you throw in starts with "Now that this horse has been kicked thoroughly to death and then some" and you cite a engineerings bureau report to NYSERDA which describes a house with an air source heatpump system with a gas backup, which now means you are paying for 2 systems upfront (page 19). It makes the point that the heatpump itself is not able to keep up with the house load at lower outside temperature, thus the need for the additional furnace. The best here is that this is not meassured performance, but calculated by the engineering bureau based on manufactures' data provided and the bin data. Even further, certain things like the frequency of defrost cycles are "assumed". None of that is data, it is not even an anecdote!

Please check things you cite as evidence before you post them so we can take them for granted.

My initial take on over-sized, variable speed heat pump efficiency is simply that over-sized heat exchangers are more efficient.

Doesn't it depend on the design of the individual heat pump. If a larger heat exchanger makes a heat pump that much more efficient, why don't they design and build with a larger heat exchanger to begin with?