Posted By docjenser on 15 May 2012 01:16 AM

Posted By MikeSolar on 14 May 2012 07:04 AM
The principal is the same whether ASHP or GSHP. Close up the dT and the efficiency increases. There are two ways to do this on any given house.....reduce spacing or increase mass. The only down side to having high mass in a radiant system is response time, but if the rest of the house is high mass, the temps don't need to fluctuate quickly. We have done a number of off grid houses with radiant stoves, high mass, and the temps rarely vary more than a few deg, even without supplemental heat.

I have seldom seen a reason for low mass radiant except for a builder who is not willing to wait for gypsum cement to dry out properly.

The response time is a huge issue in higher efficient buildings, which simply don't loose much heat, and usually have much solar gain.
High mass floors are taking hours to heat up and hours to cool down. They don't give you heat when you need it, and then still heat when you don't need it.
May be you can elaborate how a higher radiant mass will increase efficiency? What matters is the conduction from the pipe to the floor above. Yes, spacing is one way. Gypsum and concrete is a bad conductor, aluminum is much better.

Sure, aluminum is a better conduct but that is not a reason to use it, UNLESS, you have no other thermal mass in the house which is typical of most North American homes. I don't put t-stats in homes anymore except to switch over from heating to cooling (30% of the houses I work on have cooling). High mass systems work well with outdoor reset and good control strategies, anticipation of OD temp changes. The problem is that controls here are not built that way and in the land of high mass building (Europe) those controls are more commonplace.

I would have to go back to my old Wirsbo or Rehau manuals from 20 years ago, which show tube spacing and water temps for different construction methods ( I will search for them later) but for the same heat output, you need a higher water temp with gypsum or a 1.5" drypack than with a 4" slab or you need better tube spacing.  I can't give you a technical answer with the math as Dana probably could, but I have worked on 100s of houses over the years and have found it to be true. I understand that there is direct relationship between HX surface area and liquid or output temps, that is the easy part.

Posted By MikeSolar on 14 May 2012 08:42 PM
Dana1, here is a link to the IEA website on the development of the ASHP and GSHP. The report is a final one detailing best practices and in it you can find some system performance data. There are some ASHPs with COPs approaching 4 and GSHPs with COPs near5.

http://www.annex32.net/field_monitoring.htm

The difference, in my mind, between North American HPs and European units is partly one of holistic design. We tend to take heat distribution by forced air system as a given which they don't do. It is considered lowest common denominator in Europe and the floor heating or radiators is included in the building design from day one. Forced air would generally not be considered because it takes up space, is more noisy and uses more energy to move the heat than heating with water.

The people I know over there use, for example, tubing with a 4-6" spacing in concrete which can result in 30C EWT and a 5-7C dT. Very different practice from here.

The link to the full document download is here. 

Thank you for that!  Surveys are by nature lacking in detail, but it would be very interesting to know more detail on the "Average Best Practices" systems bar-graphed in figure 2, p12, eh?

Overall it still looks like the high-3s for the industry average on newer-better/best installations.  In figure 1 p.11 the center of the curve on the slightly older Swiss survey was still 3.5-ish, but with a few 1-sigma outliers in the >4 range.

To be sure low temp hydronic systems will (almost) always beat air-delivered heat on for whole-system COP (true for both GSHP & ASHP.)

Clicking on the markers for a particular "Best Practices" installation on the installed monitoring map then selecting "database" it'll open up a 1-pager that includes system info, including the SPF (average COP).  You'd have to look at other resources to figure out average weather and groundwater temps etc. for any given location, but there are still several "Best Practices" geo systems in northern Europe averaging under 3.  Most where a "design SPF heating" is specified have measured performance that misses the mark by 5-10%, eg:  http://www.sepemo.eu/hp-best-practi...[item]=795 but some are pretty close:  http://www.groundmed.eu/hp_best_pra...abase/411/

The description of the system design and low-temp radiant tubing layout & design for this one is a plausible explanation of what it takes to hit an average COP of 5.  I don't know of any US installations that are as carefully crafted or implemented.  The mean SPF of all systems in the SEPEMO best-practices database is still 3.8, not 4+.

So like with the ductless systems, I'm encouraged by where the state of the art can take you in well thought out, well executed systems, that report doesn't move my expectations much (if at all).  As with most complex heating systems, the quality and experience of the designer is the biggest risk/reward on achieving actual performance in GSHP, and the even amongst the best-practices monitored systems there are some (relatively) low performers- the bell-curve is wide.

No problem. It just shows how much CAREFUL planning can make a difference but, to be fair, there are some low brow HPs in Europe too but because they are seldom designed for cooling, the heating performance can be optimized. Many manufacturers also include solar thermal right in the design, including the control, not just an add on. The Austrians seem to have the best equipment and the Swedes seem to have the lowest standard heat loss around.

When I am finished outsulating my double brick house, i will have the all the sensors in the walls for monitoring temps, solar production, ASHP run times and current draw. I want to emulate as much as possible the best European practice. I'm a big fan of thermal mass although it is hard to explain why it actually allows for lower liquid temps other than a pure surface area argument....get a thermal mass warm enough and it is another radiator. And, Entering water temps of 35C and LWT of 27C is hard to do in a floor without mass.

We seem to be stuck on stick framing and fibreglas, neither of which i like.

Posted By Dana1 on 04 May 2012 12:04 PM
Directing the air flow at windows makes comfort & window-condensation sense for low performance windows with U values north of U0.34, but adds practically zero advantages with U0.25 & lower windows.

Adding a hard-coat low-E storm window over a U0.34-U0.6 double pane adds more comfort that siting the duct under a window, and is one of many efficiency upgrades that is usually more cost effective than extra geo tonnage to cover the heat loss difference for the lower performance building envelope.

With >=R20+walls and <=U0.25 windows even point-source heating works well, and it hardly matters where registers are located, leading to shorter duct runs.

Comfort is just one reason why I prefer highest-efficiency building envelopes over highest-efficiency heating systems.

But clearly, not being in the HVAC biz I have no idea what I'm talking about (ever!) :-)

Correct!

The old HVAC model of putting registers directly at windows was due to the fact that windows were valued with R-3 ratings or lower. They had horrid convection. Today, one can get windows that have R-Values of R-9 or higher. Add to that the triple pane design and these windows will have warm panes WITHOUT having a duct blowing at it. So the old HVAC model of blowing air at windows is no longer valid or needed.

"Correct!

The old HVAC model of putting registers directly at windows was due to the fact that windows were valued with R-3 ratings or lower. They had horrid convection. ."

It wasn't bad windows in HVAC lore......Carbon monoxide deaths in the late 19th and early 20th century had people going to sleep and never waking up. People took to sleeping with the bedroom window open to mitigate the mysterious "night death". That is why old steam boiler systems have the radiators at the windows (and are grossly oversized).

Posted By joe.ami on 16 May 2012 08:07 AM
"Correct!

The old HVAC model of putting registers directly at windows was due to the fact that windows were valued with R-3 ratings or lower. They had horrid convection. ."

It wasn't bad windows in HVAC lore......Carbon monoxide deaths in the late 19th and early 20th century had people going to sleep and never waking up. People took to sleeping with the bedroom window open to mitigate the mysterious "night death". That is why old steam boiler systems have the radiators at the windows (and are grossly oversized).

Sounds like the perfect rationale for directing geo ducts at windows then, eh? There could always be refrigerant leaks, which could be disaster in a tight home unless you leave the windows open! 

Trade habits & conventions are hard to break, so the rationale for retaining them may shift:  In one era it's night-death, another it becomes window condensation. But at this point it doesn't take state-of-the-art windows to simply dispense with the heat-source-by-window design habit, especially when there are upfront cost and system efficiency reasons for doing so.

Windows are the source of most of our cooling loads, so I'll continue to aim cool air at them, although from well back in the room, circumstances permitting.

Posted By docjenser on 14 May 2012 12:22 AM
Let me clarify this.==== to lower refrigerant pressured and higher COP. Thus radiant floors can be more efficient in heatpump applications than forced air.

Agreed IF and ONLY IF I am reading your head pressure gauges lower than the forced air refrigerant readings..., and a forced air that is high-efficiency distributed. Again, fire another thread.

Who has other curves or  tables of what was asked in the first question?

Nice comments by so many !

T's Mike:

-Have to just be cutting to the chase  though.

1)
Put a compressor in between a 35 to 55% over sized air coil, and 55% oversized water coil as is the ratings mentioned, and there is the 4+ in AHP IF the energy exchanged Ex is that much greater at the over-old-standard 1:1 exchanger sizing.

Watch for the Climatemastering 40SEER, just like Hydro-Temp has IQ now... BIG Ex at having BIG HX coils....

Dana 'tis true, those putting 4 ton GT multi-multi stagers in and on 2.1/2- ton heating loads at ~ 15 to 20 above and with then 35- to 37 degre ground loops hitting 3+ gpm/the 4 tons is going to (without variable WILO pumps on the flow center, or grundfos ALPHA's on little ones, etc) get near COP 5's ONLY at the relatively leveraged mega dollar heat exchanger over-sizing. just in coldwater heating up the head pressures can be at (chilly) 85-88 degrees and suctions above 33-34 deg...  getting all that with a single 180-200 watt pump on the loop side. That is why I have metered under 8000 KWH for all HW and Heat and Cooling as well on 3500-3700 what I called 'typical' sub zero homes.
What is so interesting too is they had 80-100 dollar electric bills with propane or oil and now, with UNISULATED basements, still , have budgets under 130-134/month !!! Electric co other charges dropped with the higher kwh usage disproportionately.

2)
Mike: How many (high or low mass) steady-state Ex have you been able to see in , ugh- typical 6" wet-cellulose, wall, r-50 attic, under 35% glass northern homes are there really going to be 4+ AHP's in normal sub zero winters?  I am just asking nicely...

3)
Any 11-btuh to 11.3-btuh/sqft for comfortable 71-72 air temps? I have heard other testimony, but finding 11 btuh/sqft in more efficient HVAC forced air heating: Are there any you see way below that 11/sqft, in homes of  below zero weather, with open stairs to basement to rec area and large vaulted main floors above? About a few homes measured, but 'typical' for good air distribution and comfort is why I would like to compare to others data. (Having high return-air's)

Posted By knotET on 18 May 2012 02:27 AM
T's Mike:

-Have to just be cutting to the chase  though.

1)
Put a compressor in between a 35 to 55% over sized air coil, and 55% oversized water coil as is the ratings mentioned, and there is the 4+ in AHP IF the energy exchanged Ex is that much greater at the over-old-standard 1:1 exchanger sizing.

Watch for the Climatemastering 40SEER, just like Hydro-Temp has IQ now... BIG Ex at having BIG HX coils....

Dana 'tis true, those putting 4 ton GT multi-multi stagers in and on 2.1/2- ton heating loads at ~ 15 to 20 above and with then 35- to 37 degre ground loops hitting 3+ gpm/the 4 tons is going to (without variable WILO pumps on the flow center, or grundfos ALPHA's on little ones, etc) get near COP 5's ONLY at the relatively leveraged mega dollar heat exchanger over-sizing. just in coldwater heating up the head pressures can be at (chilly) 85-88 degrees and suctions above 33-34 deg...  getting all that with a single 180-200 watt pump on the loop side. That is why I have metered under 8000 KWH for all HW and Heat and Cooling as well on 3500-3700 what I called 'typical' sub zero homes.
What is so interesting too is they had 80-100 dollar electric bills with propane or oil and now, with UNISULATED basements, still , have budgets under 130-134/month !!! Electric co other charges dropped with the higher kwh usage disproportionately.

2)
Mike: How many (high or low mass) steady-state Ex have you been able to see in , ugh- typical 6" wet-cellulose, wall, r-50 attic, under 35% glass northern homes are there really going to be 4+ AHP's in normal sub zero winters?  I am just asking nicely...

3)
Any 11-btuh to 11.3-btuh/sqft for comfortable 71-72 air temps? I have heard other testimony, but finding 11 btuh/sqft in more efficient HVAC forced air heating: Are there any you see way below that 11/sqft, in homes of  below zero weather, with open stairs to basement to rec area and large vaulted main floors above? About a few homes measured, but 'typical' for good air distribution and comfort is why I would like to compare to others data. (Having high return-air's)

The houses i have worked on have not used wet cellulose but just about everything else (tires, straw bale, old jeans, foams, etc) but it is not unusual to have sub 10btu/ft2 in some of the houses i have worked on as a heating/solar contractor. 35% glass is in the passive solar range and there have been quite a few of those but unfortunately I only get anecdotal evidence of actual heating costs in these houses but i can say, that with really low distribution temp needs, I doubt you will find many people happy to sit beside 78F air but for a lot of the year you can heat with less than 78F water if done right. 

I don't know of any ASHP that can produce a MEASURED COP of 4 at below freezing temps but I don't see why an ANNUAL 3.5 cannot be achieved with the right tube spacing and careful HP coil design AND I believe that with the solar/ASHP setup we are now designing, we will be able to get an annual COP of 5. I won't be able to report on that till this time next year, unfortunately. I am not holding my breath but if it comes in I will be quite happy. All this and the installed budget (solar included) will be about 65-70% of GSHP. That is the goal.

Zounds great the heating with 78 water.  Our basement rec slabs hold 71-73 with 75-78 respectively, but 5-6" first 4 runs from perimeter to 14-16" spaced in center low loads.

SOLAR boosted AHtP, as my cousine from Austrailia put it in 1981, were all for him government grant boosted and air to HW heating as well. He saw the pictures of the TETCO 1-ton w:w water heatersunder 40 gal amtrol tanks (inside DX of 4 (?30") columns of little ~2"dia.CuCoils run inside of that water vessel, a Dave Heart design of '79). Cous' is now an Engineer with directing some of the State of Victoria's Solar. Same year'81, an auto vocational teacher in Massilon near the Football Hall of fame (Canton) hybrid-looped in drain-down collectors on a ss tanker vessel -top 6- ft deep. Moist clay soil held temps down sow it was more effectual below 55 water (well water buffer, only). He believed 2) 3x6's delivered over 4500 btuh each on working on 45F waters.  

What do you think if you just raise the air temps through air solar collectors of high heat transfer, very low mass, low collector-heat-storage- capacity Air-Collector for some installed cost efficiency?  Boosting 1/3 at or in about 70% of a compressor (inside-labled) rating of 2 tons ::) then 18kB to ?20kB Ex cold-conditions might be such that we may corollate to solar air additions of near:

(ignoring constants)~  10F x 600 cfmuhmmm..! Then by a peanut Sol-Air-movement.
Seems that's under 1/6hp blowers similar to units re-capturing the heat off of gas-pool-water heaters power-vents (final stage HX pool water flowing heat-recovered) within those experimental add-on FanCoil, thin SS boxes.

200-300 watt blowers for a near 2 kw Solar Booster design of one collector in ? 10- to -10F air intake, getting over to AHP outdoor section ?

Posted By knotET on 18 May 2012 07:58 AM
Zounds great the heating with 78 water.  Our basement rec slabs hold 71-73 with 75-78 respectively, but 5-6" first 4 runs from perimeter to 14-16" spaced in center low loads.

SOLAR boosted AHtP, as my cousine from Austrailia put it in 1981, were all for him government grant boosted and air to HW heating as well. He saw the pictures of the TETCO 1-ton w:w water heatersunder 40 gal amtrol tanks (inside DX of 4 (?30") columns of little ~2"dia.CuCoils run inside of that water vessel, a Dave Heart design of '79). Cous' is now an Engineer with directing some of the State of Victoria's Solar. Same year'81, an auto vocational teacher in Massilon near the Football Hall of fame (Canton) hybrid-looped in drain-down collectors on a ss tanker vessel -top 6- ft deep. Moist clay soil held temps down sow it was more effectual below 55 water (well water buffer, only). He believed 2) 3x6's delivered over 4500 btuh each on working on 45F waters.  

What do you think if you just raise the air temps through air solar collectors of high heat transfer, very low mass, low collector-heat-storage- capacity Air-Collector for some installed cost efficiency?  Boosting 1/3 at or in about 70% of a compressor (inside-labled) rating of 2 tons ::) then 18kB to ?20kB Ex cold-conditions might be such that we may corollate to solar air additions of near:

(ignoring constants)~  10F x 600 cfmuhmmm..! Then by a peanut Sol-Air-movement.
Seems that's under 1/6hp blowers similar to units re-capturing the heat off of gas-pool-water heaters power-vents (final stage HX pool water flowing heat-recovered) within those experimental add-on FanCoil, thin SS boxes.

200-300 watt blowers for a near 2 kw Solar Booster design of one collector in ? 10- to -10F air intake, getting over to AHP outdoor section ?

75-78 is not so hard in a basement with a slab but harder to do upstairs with more heat loss so the tube spacing has to be max 6"

The solar boost is not for the air side. Too much fluctuation and no storage. My system uses the solar thermal to up the evap temp.

I think it is better to have 3 low efficiency flat panels than 2 very high efficiency flat or tube panels. panels last longer, so does glycol

Not sure what this below means:

"Boosting 1/3 at or in about 70% of a compressor (inside-labled) rating of 2 tons ::) then 18kB to ?20kB Ex cold-conditions might be such that we may corollate to solar air additions of near:

(ignoring constants)~  10F x 600 cfmuhmmm..! Then by a peanut Sol-Air-movement.
Seems that's under 1/6hp blowers similar to units re-capturing the heat off of gas-pool-water heaters power-vents (final stage HX pool water flowing heat-recovered) within those experimental add-on FanCoil, thin SS boxes.

200-300 watt blowers for a near 2 kw Solar Booster design of one collector in ? 10- to -10F air intake, getting over to AHP outdoor section ? "

Posted By MikeSolar on 18 May 2012 01:17 PM

Not sure what this below means: ..."Boosting 1/3 at or in about ..."

Maybe because you don't speak Klingon?

Posted By engineer on 17 May 2012 10:00 PM
Windows are the source of most of our cooling loads, so I'll continue to aim cool air at them, although from well back in the room, circumstances permitting.

The vast majority of the heat gain through windows is radiated, not conducted, even with low-E windows.

Radiated heat passes through cool air just as readily as through warm air-  the net effect of aiming the cool air at the window is negligible, whereas shading that window on the exterior has a huge effect.

isn't he just the cutest thing I wonder if he can read an answer questions at the beginning anyway .. thanks for your real effort mike and the rest what I was doing as I was estimating 1 third of the total load of absorbed heat outside ahp might need at the evaporator through the entire discussion as it was regarding solar boosting at the evaporator mode of the outdoor condensing unit a lot of people just called that condenser units section. it was merely a proposed guess to just see where they ending results would be about cfm . I wonder how many have experienced floor heating of the low mass upper level with less than 80 degrees that's great that you get something like that . Solar boosting has been discussed before I read in. 1980 Seems promising. I really wanted to pull out of the hat some things you may have come across mike so feel free to share with us as you seem to be in a 99 percentile sufficienttly enjoying this thread . I also believe blocks of ice are also part of referring to as the experienced as w.ell as a qualified technician to set things up . experience similar hardships in the humid winter weather belowlake erie. Mike--- I wonder more of what you mean by temperature differential and some other basis for your discussions about that as I read more of your responses I will understand your picture better . 'k-nough4now

Posted By Dana1 on 18 May 2012 05:11 PM

Posted By engineer on 17 May 2012 10:00 PM
Windows are the source of most of our cooling loads, so I'll continue to aim cool air at them, although from well back in the room, circumstances permitting.

The vast majority of the heat gain through windows is radiated, not conducted, even with low-E windows.

Radiated heat passes through cool air just as readily as through warm air-  the net effect of aiming the cool air at the window is negligible, whereas shading that window on the exterior has a huge effect.

For a west facing window, what is the lowest SHGC that you would recommend for a window?

The lowest you can get, consistent with tolerable visual light transmittance and budget. A load calc lets you model the effects of various values of SHGC. Spending more than a few extra bucks on a window with more favorable coefficients rarely pays back in a reasonable time.

Down here I push for SHGC in the 0.2x range for south and west glass unless there is excellent shade.

Posted By engineer on 18 May 2012 10:05 PM
The lowest you can get, consistent with tolerable visual light transmittance and budget. A load calc lets you model the effects of various values of SHGC. Spending more than a few extra bucks on a window with more favorable coefficients rarely pays back in a reasonable time.

Down here I push for SHGC in the 0.2x range for south and west glass unless there is excellent shade.

Where are you located at?

So even with the south facing windows, you want 0.2x on the SHGC level?

While it is considered a "mild" climate where I will build (Chino Valley/Prescott, AZ). I am going to go with 0.48 SHGC on the south windows to make use of the passive solar during winter.

I know anything below 0.40 for the VLT, it starts to seem like tinted glass.

Posted By Looby on 18 May 2012 04:46 PM

Posted By MikeSolar on 18 May 2012 01:17 PM

Not sure what this below means: ..."Boosting 1/3 at or in about ..."

Maybe because you don't speak Klingon?

I tried klingon, nearly lost my vocal cords. Big fan of proper punctuation though.

Posted By knotET on 18 May 2012 06:51 PM
isn't he just the cutest thing I wonder if he can read an answer questions at the beginning anyway .. thanks for your real effort mike and the rest what I was doing as I was estimating 1 third of the total load of absorbed heat outside ahp might need at the evaporator through the entire discussion as it was regarding solar boosting at the evaporator mode of the outdoor condensing unit a lot of people just called that condenser units section. it was merely a proposed guess to just see where they ending results would be about cfm . I wonder how many have experienced floor heating of the low mass upper level with less than 80 degrees that's great that you get something like that . Solar boosting has been discussed before I read in. 1980 Seems promising. I really wanted to pull out of the hat some things you may have come across mike so feel free to share with us as you seem to be in a 99 percentile sufficienttly enjoying this thread . I also believe blocks of ice are also part of referring to as the experienced as w.ell as a qualified technician to set things up . experience similar hardships in the humid winter weather belowlake erie. Mike--- I wonder more of what you mean by temperature differential and some other basis for your discussions about that as I read more of your responses I will understand your picture better . 'k-nough4now

I concentrate on heating over cooling, which is why I call it an evaporator. Just trying to be accurate. I don't have the numbers to say yet what the gains from solar heat injected into the evap will be but I suspect that as long as it is not snowing out, there can be some gain.

There is a large time frame, during lighted hours, when the panel temp is below that needed to heat DHW at all but it could boost the evap from, for example, -10C to 0C. This alone is a great improvement over the standard ASHP. The big issue is controls and this is where no existing package unit will work as they have a pretty rigid programming. You have to be capable of DDC controls to make it work to the best efficiency.

To top it off, Ontario has time of use electrical rates. Peak is around $12/kwh and off peak is $.07/kwh. At night when we cannot use the solar gain directly, we are heating at a reduced cost. Win/win in my estimation.