With high performance windows and moderate-R walls the placement of either supply or return duct registers relative to window locations shouldn't much matter from a comfort point of view. Placing the return near a window may ensure that the coolest air in the room is what's headed for the HX, but the temperature differences near the floor anywhere in the room with R20+ exterior walls and U0.25 or lower windows won't be huge. Maybe directly under a very tall window it might be worth it, to vaccum up the convecting cooler air. But still, with the window surface temp above 60F in a 70F room you won't get the gusher-cascade of falling cool air that you might otherwise see with a much colder U0.6 window.

But the supply/return register locations relative to each other of course does matter.

My bad shouldve said furniture isnt likely to block widows. That said you'd be suprised how often consumer v hvac pro determines placement and even design.
Delivering adequate cfm to a room in even a new code minimum house with a ecm blower goes a long way to evening out temps.

Perhaps I was misunderstood. I certainly do not advocate placing supply ducts directly over windows, rather I have them set well back into the room so that the air stream travels over occupants heads, entrains air near ceiling, and pushes the whole mass down along windows, outside walls and doors.

Of course, being in a cooling-domiinated climate, I favor supplies and returns in ceilings. Two bonuses derive from that - furniture placement is relatively less of an issue, and high returns pick up less floor debris and animal hair.

I do favor positioning registers under windows in cold weather climes, although Dana's points about ever-better building assemblies and components make sense. One can worry less about point loads and more about merely circulating the air. Merely circulating the air becomes steadily or challenging as loads, system capacity, and airflows steadily drop on a conditioned square foot basis.

I'm not sure if ICF is unaware or being deliberately obtuse, but air from a supply register directed tangentially along a window neither impacts the glass directly nor fails to entrain surrounding air.

Oh well.

I'm not sure if ICF is unaware or being deliberately obtuse, but air from a supply register directed tangentially along a window neither impacts the glass directly nor fails to entrain surrounding air

Of course. I was just responding to where you said;

"It ain't rocket science - the basic idea is to have supply air "attack the load" which generally means directing supply air at windows and exterior walls while not subjecting occupants to drafts."

Posted By joe.ami on 04 May 2012 06:49 PM
My bad shouldve said furniture isnt likely to block widows. That said you'd be suprised how often consumer v hvac pro determines placement and even design.
Delivering adequate cfm to a room in even a new code minimum house with a ecm blower goes a long way to evening out temps.

True, dat!  Continously variable air speed is THE standard for comfort in any air-delivered heating.

Have continuously variable ECM drives become most common sort of air handlers used  in GSHP systems, or is it mostly 1 or 2 speed?

you almost have to go out of your way to get a PSC motor in geo anymore.

I can't imagine bying geo with a PSC blower.

PSCs are pretty much reserved for code minimum air source systems these days

The price of an OEM replacement for a variable speed blower is quite high so if I have folks looking at furnaces for a modest sized home and they have no air flow complaints, we will use psc's there, but I don't remember the last time I sold one on a geo.

Posted By Dana1 on 07 May 2012 11:39 AM

... Have continuously variable ECM drives become most common sort of air handlers used  in GSHP systems, or is it mostly 1 or 2 speed?

For my WaterFurnace 2-stage ECM variable speed Envision units, circa 2007, it's in between "continuously variable" and "1 or 2 speeds."

For my 3 ton unit with 3 zones, blower speed is one of 5 pre-selected speeds.  Actual speed chosen depends on tstat settings for all 3 zones combined, using the algorithms programmed into WaterFurnace's IntelliZone zone controller unit.

For my 5 ton unit with no zoning (one tstat), blower speed is one of 3 pre-selected speeds.

Parenthetically, in a zoned situation, WF's IntelliZone produces a pulse width modulated signal to control the ECM blower fan's speed.  So, theoretically, someone could build an alternative controlling unit that supplies a continuously variable PWM signal, to achieve an 'out of the box' continuously variable ECM drive.

Best regards,

Bill

 

Posted By a0128958 on 08 May 2012 02:19 PM
For my 5 ton unit with no zoning (one tstat), blower speed is one of 3 pre-selected speeds.

Same with all single zone Envisions -- three pre-selected speeds, and one of
those is only active for a few seconds on startup. The other two speeds are
hard-associated with the compressor mode, one each for stage1 and stage2.

Although the motor is capable of "continuously variable" operation, it's not
at all clear (to me) what benefits that might offer. Specifically, if I wanted to
design a '"smart" (single zone) fan controller, what logical rules should it
follow? What conditions would call for varying the fan speed -- other than
compressor switching between stage1 and stage2?

...just curious,

Looby

@ Looby. I'd definitely think to correlate lower speed blower with higher humidity to wring more out of the air.

Hi Dana:
You have AGAIN managed to not discredit, nor berate a theory or practice or slight the experience or past of a practitioner (other than that blasted word 'tepid' which means 88-90 for of any and all post-postings too per/of and by my references).
Alright all:

So I can now better-see an example of what I can reword about an original question:

At a fixed 90F- about ENERGY at a mini-s's  (or any on-high heat with an air speed -any 20+seer Air-Ht-Pump, but in the heating  cycle)---
 variable speeding to a slowing of air VOLUMES (I suspect just about a total thermal energy (Ex)  out===) now again- at (if we could) a fixed 90F,
and a GT also at a fixed 90-out=== (Ex)
if we could see all,
----
what would the Ex be on a SAME compressor in each tested, as the ambient outside drops from 47  to average humid  mid PA area 12-to 10F above, that I am asking: what % ROUGHLY would  the GT out-perform possibly ( est: around that 5800-6000 HDD in normal peaking -3 to-5 winters) ?

Is there an outside temperature curve ?
Is ther a related curve where someone can get a comparison?
Ducting was referenced as 'no-loss' in the house interiors where energy is received, like just Ex floating in joists areas about the duct tubing, not lost to much at all.

2) Today a manufacturer gave a verbal about how a humid Cincinnati winter temperature of at 15 degrees outside ambient could really be very near the limit for a most usable 16 SEER high speed - 20 SEER low speed mini Air Ht Pump. They mentioned dry winter times may work to 5 above for EX of but below 60% of a 47F rating. -all indoor air controlled outlet temperatures the same , just the blowers slowing down, yielding less EX output.

Thirdly ( I dare comment )
I have read of why the slick skin of an aircraft is NOT slick at lower speeds of below 60 knots like a feather is.  And that the porpoise skin is "slick" in water although straingly was rough to the touch a little bit at when I felt it. What I remember is a discussion of the 'sticky' laminar 'fluid dynamics' of air that is  also in ducting discussions about inside air layers on the inner walls of the metal during use . In solar collectors I ask about in another post, it was seen a 3/4" gap specification between top solar glass and a clear barrier to a collector. With ceiling fans I am told to not disturb the hot ceiling under the roofs or under the attic areas and to leave those fans off while cooling.
I ask about this too: Do the mini's and console units blow ON the walls? I have seen that done in pool areas about condensate, and on some very low air flows directed to sky light windows at times many years ago.
Isn't it such a like-situation of that in  a physics of all considered- if we move air more than not, and about and across a flat plate heat exchanger we will then move just more Ex?

knotET,
your ramblings are getting longer and more incoherent with every contribution. why not try short and sweet.

btw if Dana has an axe to grind it's about insulation first heat plant second. characterization of anti geo simply shows ignorance to the body of work.
j

Posted By joe.ami on 09 May 2012 10:44 AM
knotET,
your ramblings are getting longer and more incoherent ...

Hmm...

- Final rant storm from gtjp: 28 Apr

- One day rant fest by GEOjp: 30 Apr

- First appearance of knotET: 01 May

"24 hours in a day, 24 beers in a case. ...Coincidence?"
- Steven Wright

is there a graph of that I am asking about, leaving all that long duct commentary behind, just an answer to a first question?

Dana does not seem to be "grinding" anything, as he shared "not up close" , that I did understand.
Do you have helpful answer?

what is  is it was a question.

Posted By joe.ami on 09 May 2012 10:44 AM
knotET,
your ramblings are getting longer and more incoherent with every contribution. why not try short and sweet.

btw if Dana has an axe to grind it's about insulation first heat plant second. characterization of anti geo simply shows ignorance to the body of work.
j

I'm definitely not anti-geo.  I'm  anti-overbuying, and prefer to see the money spent where it buys the most comfort & efficiency for the money. Sometimes that's geo, but given the low average envelope performance of the existing single family housing stock many times the money is better spent on the building.

To be clear, the higher comfort of a building-upgrade + ASHP solution has nothing to do with the temp of the heating air delivery- it has everything to do the higher-R/lower-U building envelope, with it's warmer walls, windows &  floors, and essentially no drafts.

In my neighborhood ground source heat pumps cost something on the order of 9 grand/ton for 3 to 5 ton systems (and sometimes more.) In many retrofits it's cheaper to peel off 25%-30% of the heat load with judicious envelope upgrades than it is to buy the marginal increase in geo it takes to support the higher load.  In homes under design or in homes undergoing major renovations a 50% or greater reduction can be often done on a more cost-effective basis than buying bigger geo. The life cycle of most building envelope components are on the order of a century (with the exception of ultra-high performance windows) and the operating & maintenance costs of that "missing geo" is effectively zero, so even if you're paying 10-12 grand/ton in load reductions via envelope improvements, it may still work out better in a 25 year net-present-value analysis, and better still on a total lifecycle cost basis.

When loads can be reduced to the 2 tons or less range, higher efficiency ductless air-source heat pumps (with inverter drive & variable refrigerant volume) becomes a viable option for US climate zone 5 or lower. The state of the art has improved dramatically over the past decade, rising from HSPFs in the 7s and very low 8s now hitting the 10+ range.  This makes them efficiency-comparable with geo in US climate zone 4 or lower, if still lagging in zone 5.   It's fair to say that I'm bullish on the dramatically-improved ASHP technology where it can be applied, given it's comparatively low cost (and low design risk) compared to 1-2 ton geo.

Even in cooler climates where it's efficiency is in the mid to high 2s as opposed to mid to high 3s, the cost delta may not always be worth the higher efficiency.  In Sweden, which now has building codes based on energy use performance rather than prescriptive R & U values, air source hydronic system sales have boomed, swamping geo sales (with quite a range of offerings compared to what's available N. America). But when simulated and tested in a Swedish climate (and in-situ) they're still only running seasonal COPs in the 2s.  With performance based energy use codes, the pressure is on the envelope & systems designers to come up with lowest-cost solution that actually delivers the energy use performance (there are penalties for building non-compliant buildings.) See: http://www.energimyndigheten.se/Glo...gram_1.jpg 

Geo is far from dead in Sweden, but it's market share has shrunk to something like 20-25% of the market, whereas a dozen years ago GSHP numbers dominated (and this is despite a subsidy for GSHP, though not as rich as the US subsidy.)  If it were cheaper to build a crappier house and go with bigger more efficient geo, you can safely bet the market share of heat pump type would be flipped the other way.  Hydronic air source heat pumps are not cheap either- 2x the cost of air-to-air ductless, but cheaper than GSHP, and lower-risk. Southern Sweden's Baltic-tempered climate is comparable to US climate zone 5 for winter temperatures, but much cooler in summer. Northern Sweden's winter temps are more like US climate zone 6, yet air source dominates the market.

Better grade air-to-air ductless tends to beat the average in Swedish performance table for hydronic ASHPs in climates as cool as Stockholm/Uppsala.  This has been measured both in labs and in-situ over many installations in eastern WA/ID for a program run by the Bonneville Power Administration.  While in some of US climate zone 5 regions the in-situ COPs were averaging 2.4-ish, the BPA analysts conjecture it that this was due to a preponderance of slightly older units with lower HSPFs in that sub-region, a reasonable guess given that the average in other regions of comparable or cooler weather were averaging above 2.8 with newer-model, higher HSPF mini-splits.  The numbers of units monitored in-situ are still pretty small, but it's not onesie-twosie type data with possibly large measurement error.  In the US marine zone 4 regions in the study the measured in-situ COPs were over 3.  See the metered COP column of Table 33, p.50 (p.63, in .pdf pagination).  A map of the sub-regions in that table can be found on p.8 (p.21, pdf pagination.)  Basically, everything east of the Puget Sound & Willamette is US zone 5 (with a very few installations in zone 6.)

The final report for the NW Ductless Project is due out in July of this year, but I doubt that anything in it would dissuade me from the notion that in US climate zone 5 often (but not always) better to take the first $25K of the $35K one might otherwise spend on 4 tons of geo and use it to reduce the load to something like 2-2.5 tons, then spend the remaining $10K on a 3-4 head 2.5-3 ton ductless.  The tighter higher-R building is more comfortable and durable than the higher-efficiency GSGP solution, and the annual power use is comparable.  This solution isn't always going to be possible or practical- I'm not expecting GSHP to disappear any time soon (quite the contrary), but at the same time I expect to see a surge in high performance ductless installations, as well as deeper energy retrofit upgrades on buildings going forward.

In zone 5 New England at current prices, displacing propane use with ductless pays for ductless in about 3 years even with 15 cent electricity, even assuming a lowly average COP of 2.5.  With oil heated houses it pays for itself in 5.  This is where I would expect the market to start driving installation numbers locally, but consumer awareness isn't fully there yet, just as it isn't in the Pacific Northwest.  (Ductless accounts for ~90% of the home heating market in Asia, where home sized and heating loads are smaller than in the US.)

We're still looking for that high performance ASHP forum, eh!

SO Dana thanks again:
if I am getting a 44% savings over condensing propane, with hi mass slab radiant or same type of forced air heating with GSHP multi staging, heating MODULATING blower keeping 92 or 96F outputs, what would you throw out as a % savings with mini's?
THere are no duct losses in the equation. Right statements can be accessed about ducting, but there are none in this event.

I found the graph as a table of results of the nearly 5 years of BristolCompressors.com v-Star, IQ ver rfg which is now IN GSHP for sale 60-days ago with same modulating heating blower- by temperature controls by sensor in blower cabinet. The results appear to be a 4 ton mini works like a 3.3 ton GSHP at a humid 15 deg ambient (under PA by lake Erie winter) and does barely hold CP above 2 for the ver rfg mini vs 3.4- 3.6 ALL PUMP (one) inclusive 180 w COP's of the GSHP on a needed load of about 40,000 btuhs at that 15 deg ambient. If that research holds the mini= ver-rfg AHP with propane cycling on at 7 degrees to 10, throughout to average 0-deg winters, would comparatively save about only 22-27% on the dollars, that GT is saving well over 44%. now add HW budget, and related, seems to leave still GT at ROI's over 8 years in that example at about 65oo/ton installed here, for 100% HW and GT ahd the ver rfg IQ... the dual compressor would have a quicker ROI but less dollars in 12 years savings est.

Eh! You are absolutely right, ASHPs have made a big leap forward. And they are a great bang for the buck. But you get all excited about COP in the mid 2s to 3s, when we are at COPs in the mid 4s with GSHPs, including the 230 watts for the loopfield circulator averaged over the season. So a small load in a big room, sure, mini splits are a good alternative. But whole house heating still needs a distribution system. We have to keep the comfort in mind here too. Don't you want other rooms heated, too? Once you have to put one high wall unit in each room, the cost goes up. Sure inverter technology is a big leap forward, that is why they are getting introduced in GSHPs.

Your posts on the subject are very long, and very repetitive!

deleted double posting

Posted By knotET on 09 May 2012 09:51 PM
with hi mass slab radiant ... what would you throw out as a % savings with mini's?

What makes you think that high mass radiant is in any way associated with energy savings?