Free A/C?

Ken_40

In '05 it was German, in '07 it's Czech. It's been a week. The U.S. rep doesn't return calls or e-mails. Corporate in Czech-land either doesn't do English or doesn't care.

Either way I am leery.

I suspect I am on such thin ice, perhaps I should return to plan 'B' - two separate units, HRV in one box - A/C in a ducted mini-split array for the other.

One last resource is FHP (Florida Heat Pump) No one has mentioned them as viable in this regard, except Jeff Lawrence - way back when.

Your comments please?

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Ken_40

Heat Recovery Ventilation + A/C

We have a small abnormally "tight" home. My fellow ASHRAE buds and I are trying to design a combination HRV unit (so far LifeBreath seems to be the HRV "winner") and a radical A/C system into one box. The A/C side will not be a condensor/compressor/evap setup; rather, what amounts to a ground water HX.

A cold water trout stream runs nearby and we are designing a HX in the plenum of the HRV to handle the 5-10 day a year need for A/C. I'm sure someone has done this before, but the totally abnormal house (among the tightest ever built), HRV need and minimal A/C setup are challenges.

Does anyone know of any prior designs that are out there or are we totally on our own?

We already have a viable design, just hate to be so far out on the radical curve as to miss something anyone else may have tried - that either did - or, did not work.

Questions, comments or suggestions anyone?

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Brad White_172

Interesting project, Ken

If you are limited to using your Lifebreath unit (fixed CFM), will that be enough to cool the space? Or do you just want to get out of it what you can? Cool it as low as you can but not freeze the coil?

I would hate to see you expend the effort and get just the edge taken off but not give you full comfort.

The WSHP approach is sound but the Lifebreath folks also make, IIRC, an air handler too. May be chilled water. I am thinking that using a WSHP as a water to water chiller might have an application but would limit your air temperature bottom limit -and hence your humidity extraction potential. At least the air-side evaporator would not freeze.

I wonder what FHP might offer?

Not a lot to offer, just some thoughts.

Tom Hopkins

Mmm.

More to think about. Thanks for the suggestion and ideas.

Having no real A/C or HRV experience, merely aware of the physics involved and things that go bump in the night in general, we have yet to do the various calcs. required to actually devine the potential outcomes - then do a "what-if" review.

We are sure it will work, just not how well, or at what up-front expense - or, over time operating costs eval.

The problem of course, it's 90 out today with humidity to match. By the time we stop thinking and actually install whatever we need to install, it'll be fall - as all "it's not a paying customer, just my home" projects assume.

Given last year's six or seven "too hot to sleep well at night" temps, I cannot complain that loudly. The damage to condensing windows in winter however, is a potential structural impact I must avoid at any cost. Simple HRV would be the answer.

The problems start when I demand the fan and "box" be integrated. No one makes what I want; everyone makes two individual units that work.

Anything you can add would be most appreciated !

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Brad White_9

Ken

Do you have a calculated heat gain figure? At least one place to start.

The thing about any heat recovery ventilator in principle is that, if you use it to generate cooling for the space, you have to incur a loss in the process (exhausting air, throwing it away.) I tend to look at HRV's as a way to make the most of a necessary but parasitic loss, the need to exchange air in a very tight structure. Sure, you can cool this air post-recovery and get some benefit from it but then you are throwing it away.

I would far prefer to see you have a properly sized system (meaning "tight" or slightly undersized) focussed on dehumidification. The HRV will still play a role in reducing the overall direct losses. However, being sensible-only, the cooling recovery effect is only partial.

If you are limited to such a small amount of airflow, work it to death... sort of the Unico approach. Cool it to the high 30's/low 40's F. to dry it out. You can turn 150 or 200 CFM into 0.75 to 1.0 tons of useful cooling- and dry tons at that.

Tom Hopkins

Brad,

In order asked:

1. Yes. The heat gain is ~6,000 BTU's (half a ton)

2. HRV is the primary issue, NOT A/C! I want my cake and to eat it too (:-o)

3. The subject house may be the "tightest" house in VT (about 1 A.C./20 hrs.) as tested twice by blower door test, run once by a contractor I hired to do it, then again by "Energy Vermont" our state agency for such testing.

4. During the 5-10 days we need A/C here, the HRV would have to be modified. We don't want unconditioned air introducing heat and humidity from outdoors, We will recirc ~95%.

5. The design basis, ASHRAE, suggests we need 30 CFM for the size and nature of this home. We need that ventilation rate only in the dead of winter, when exhaust fans are adequate, but create negative pressurization and require doors to rooms normally closed - to be open. The HRV itself is a solution for that need.

6. The "ground source" for summer A/C - as mentioned - is a trout stream 250' from the coil we envision. Water temps will be as high as 65F max during dog-days of August. Implying the HX and flow rates will require oversizing to accomodate the 5-10 day (typically night time only)load.

Totally confused now?

I am!



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Larry C_9

How about NOT integrating?

How about not placing the "AC" unit in the HRV system? Why not a spot cooler made up of a slow speed fan, a cooling coil, and a condensate collection tray. Perhaps a unit that can be stowed away when not needed. Similar in concept to the whole house vacuum cleaner, where the cooling lines are run to various locations in the house, and all you do is plug the spot cooler into them.

Just a slightly different approach.

don_185

This heat gain

of 6000 btu how much is sensible? How much is latent?

I thinking at 65 dergee water it would be impossible to get your coil temps below dewpoint.

I see all to often on tight home that the latent capacity is not address.Trying to control latent capacity with a dry
bulb stat will not work.

Lets not forget that a tight home will reduce the sensible load however..it also increases the latent load.

Good luck!

Tom Hopkins

Well...

I'm not a big fan of the six ducts I'll need already (three supplies, three returns) for the HRV I want.

How does one do "spot" cooling to three needed areas that are on two different floors, two small rooms - separated by walls?

I'm freaking out over clean ceilings and cutting in registers as it is...

Integrated, at least in the attic space is what we need. Sure, I could go buy a split system as well, but distribution would be impossible.

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Tom Hopkins

Don,

The 6,000 is only a sensible load calc. Any de-humidification is merely a plus, not a design parameter.

Not having absolutely "known" trout stream water temps forces assumptions. I would never do this for anyone else. This is our home. Enthalpy may not be a four letter word. But in my application - it is two four leter words: "enth" and "alpy" (:-o)

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don_185

Dont hate me

That statement of not being a design parameter is outdated.

And yes I agree that with a ac its its merely a plus however
its still a issue that has to be address when the ac not running.Even with the ac running it can still be a issue.

Even more so in tight homes.Showering/cooking/fun/fun time,
oversize equipment all lead to humidity issue.

Unknown

From experience...

I worked in a factory once where they tried to use river water to get at least SOME cooling in the plant just as you describe. It was not effective at all and was abandoned. How did I discover this? (You guys will love this) The BOILER water level kept going up and upon investigating I found that they had teed the river water into the heat coil circuit and with the valves incorrectly set it would add river water to the boiler(s).

Brad White_9

6,000 sensible BTUH

If you have 150 to 200 CFM of airflow available, you could absorb that much heat by cooling it from say, 75F down to 38F (150 CFM) or 47.3 F. (200 CFM). Of course this presumes that the air coming out of the HEX is 75 F.

Assuming there is no latent transfer on the HEX, you might get, on a 90 degree day, about 8-10 degrees taken off, depending. Your 90/73 (DB/WB respectively) at 45% RH would come out at about 81/70.5 or 60% RH, no loss of humidity. The dewpoint of that air is about 66 degrees F. Enthalpy would be about 34.6 h.

Remove 6000 BTUH sensible from that 150 CFM air stream and you would cool it to about 44.1F. Enthalpy would be about 17.8 h.

To do that, your total heat required would be about 11,200 BTUH or roughly a ton. Practically a 0.50 sensible heat ratio. The really good news is, depending on how much you and The Lovely Jaye perspire, (or glow), your RH will settle in the low 40's, high 30% range.

Why do I say 150 CFM? Some HRV's fall into that category and it does not seem too low versus coil freezing. Close but not quite.

Tom Hopkins

Not sure I mentioned this but...

At my insistence, the two bathroom exhaust fans are more than adequate to provide way more than design needs ventilation when everything is tightly closed - and, the A.C./hr. Adequate vetilation is already in place. We merely want to switch/augment the manner in which we achieve that.

Blower door testing confirms our programmable, timer-controlled high-end Panasonic bath fans pull 500-600 CFM of actual air flow from the window and door chinks.

Bottom line, we have a view. We have far more moveable glass than most 1,600 S.F. homes - and we have windows open whenever it gets between 40 and 90. We are now dealing with 5-10 days a year we want A/C (and the attendant de-humidification).

Given a cooling load of half a ton, and given our ultra conservative trout stream temps of 65F (in reality 55 is far more likely - even on the "mother of all mother" heat waves), and lack of glass on the south and western exposures, we know an undersized A/C "system" is far better than one oversized.

Any other advice is most appreciated!

Tom Hopkins

???

Brad,

I sort of "get" your assessment and design ideas conceptually, but not the significan nuances of how I could get 40F output from brook water in the 50's.

I suspect you slid into real air conditioning design rather than direct from brook link to a HX coil with condensate pan and drain.

Your design may be required regardless. My design is purely predicated on NOT using conventional means, rather all "home made" cooling.

My design is based on child-like logic: e.g., leaving the house as is is fine. Cooling and dehumidification would be a good thing, REGARDLESS OF HOW POORLY IT PERFORMS. This, based upon the notion that ANYTHING that removes one grain of humidity and drops the air temp one degree is better than what we have now. Which is nothing.

One impactful detail I left out. We now pay 16-cents /KW here in northern VT. We already know further rate hikes are in store. We believe the cost/KW will be close to 20 cents/KW by next spring. Even having won the prestigious "Energy Excellence Award" from the State - and being among the most energy efficient homes in the state (probably the entire country), our electric bill approaches $100 now.

Doi you have a website in mind where a few of these designs you contemplate might be purused?

Again, I thank you for all your help!

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Brad White_9

It is coming together in my mind now Ken.

What I have offered so far is that you would use a semi-conventional means but using the trout stream as a condensing source. Florida Heat Pump (FHP as it is commonly known) has a wide variety of devices using all manner of medium. Air to air, water to air, air to water, water to water...

The fluid you use (applied directly to any cooling coil, I mean) would have to be about ten degrees colder than your desired leaving air temperature. Thus most DX systems have a 40-45 degree saturated suction temperature and chilled water enters in that range also (with counter-flow).

What I am hoping is that by using the trout stream as a condensing medium you can achieve a high efficiency on the CHW side or use the refrigerant produced efficiently also. The trout stream ought to be a lot more efficient than condenser water at 85-90 degrees or air temperatures at 95 degree rating points.

If you *do* use the trout stream directly (as a chilled water source), then you may lose humidity control and cool without ever getting below space dew-point. This will shoot your RH positively into the "check into a motel" range. I would not want that for either of you (unless it is a special occasion of course!)

I guess all of that Green Power bought by the CV including Quebec Hydro has not given the promised savings has it? At least you know your hands fit nicely around your ankles.

Tom Hopkins

Strange...

I was so sure I could get some form of A/C and a small amount of dehumidification merely by pumping cool water through a HX coil in a simple air handler w/condensate pan in my attic, I now find the dream being challenged by equally simple "thermodynamics."

Last time I checked, a water flow rate of 3 GPM with a dT between incoming water temps of 60 and leaving at 75 comes out to ~22,500 BTU/HR. I only need 6,000.

My question, how can this NOT work?

Obviously, I know nothing about A/C, in theory it must work. You suggest in reality it can not?



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Unknown

The thing is,,,

Removing humidity is the key to comfort. Your trout stream water will probably not be cool enough to cause humidity to condense on the coil and be removed from the air. You may achieve some actual reduction in air temp but without removing humidity you will still not be comfortable. Of course you ARE up in VT, if I recall correctly, so you MAY have somewhat cooler river water than we do down here in CT. My thoughts are the expense may not be worth the results but there's only one way to find out for sure...

Brad White_9

MPF Nailed It

It is exactly that, Ken. You have to have the temperature well enough below the dewpoint to wring out the moisture.

BTU's are BTU's but for them to work there has to be a temperature difference. You will "cool" the air, sure. But it will not dehumidify.

Think of it this way- you can flow your 3 GPM at a 15 degree delta-T as you suggest, but suppose that temperature range is 85 degrees rising to 100- still the same BTU's, right? But no cooling will take place suitable to you because of the temperature range.

In your case, the temperature difference you are seeking is between the water temperature (average coil temperature you can generate) and the dew-point temperature of the air you are cooling, more specifically the dew-point of the space conditions you seek.

Trivia: The reason that "55 degrees" is the rough default for air conditioning supply air is that the dewpoint of that air is the same or less than a space at 75 degrees and 50% RH. Lower is better.

I hope that helps explain it better!

Brad

Tom Hopkins

Indeed..

it does.

One point I want to clarify/determine: What temperature is the practical design "limit" the system could function "properly" at? This, in regard to brook water temperature?

I always use "CYA" projections/data. Realistically and FYI, the actual stream water temps are unknown as yet. I recall walking down there on an outrageously hot, humid day a few years ago and finding my bare feet getting numb in under 5 minutes - making me conclude the temps must be under 65F! The absolute hottest air temp I ever saw for more than 8 hours here was 94F. Of course the R.H. was full saturated.

Because the value of the envelope is ~ R-40, with one air change every 10+ hrs, I'm not worried about any heat gain, once we turn the system on and close the windows. Hell, the load on a 30-below design day is only 25,000BTU's.



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Brad White_9

The envelope of your house

obviously limits your load (really has little effect). Your biggest load then, is the outside air you are introducing. You have to cool it to below your tolerable space dew-point. This would be for most people, no higher than 58-60 degrees. Any time the dew-point is over 60F is considered "muggy" by most folks.

Here is the kicker with what you are proposing: Without wringing out the air you are bringing in, but rather only cooling it "as much as you can", you will positively raise the RH in the space. Take outside air at design temperatures of say, 90F and 74 wet-bulb. That is about 48% RH believe it or not.

You would have to cool that air down to 67 degrees to get it to even start dropping of moisture. It will be 100% RH at this point, to start. Then you have to continue sub-cooling it to 55 degrees to get the dew-point down. If you do not do that last part, the RH in your space will climb. This is because you are simultaneously reducing the space temperature which raises the RH by default.

With water at 65F, you might, at best, cool that air down to room temperature (75F, ten degrees above your EWT depending on your coil number of rows). So you will only get a few drops on the surface of the coil but no real dehumidification.

Chilled water which we use in commercial/institutional buildings has to be at least 45 degrees if not cooler to work well. We are replacing all of the piping in a 100,000 SF school because they used 48 degree CHW to save energy instead of the 42 degree RH required to dehumidify. The result? Climbing space RH and condensation on the pipe under the insulation. Rotted off in layers. Just an example.

Unknown

yes,,,

45* seems to be the magic number. I thought the RH would go up if you cooled without dehumidifying but wasn't sure. It's obvious to me now though. Go out to the stream and take the temp of the water.

Tom Hopkins

I know it's hard...

to recall all my rants and data but the o.d. air was a winter-only considiration. If we have 5% o.d.a. and 95% recirc. I'd be extremely happy.

Remember, I already have two hi-end bath fans that are capable and do ventilate the space; to the tune of 750 cfm each, fully programmable.

If we had no o.d.a., I wouldn't care at all.

We're talking about 5-10 days an entire year here!

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Brad White_9

Ken- Two Words:

Window Shaker.

For that few days, I think it will work fine for you if the load is that small. A 8-9,000 BTU unit will take the edge off. As you said, it is only 5-10 days. That is the cheapest $300 you could spend, IMHO.

Don't hate the messenger :P

Tom Hopkins

I hear ya...

The problem becomes as follows:

My walls are SIPS and ~8" thick. Windows are all casements. My bed ridden mother-in-law now lives in the second BR, how does one direct a "shaker" into any form of "balance" between the three distinct areas we ned that 10-day A/C? Once we get into even a cheapo thru-the-wall unit with 13 SEER, we're into the $500+ range, without any control other than opening doors...

I'm not real keen on trying to run a line-voltage extension cord to the unit. Being SIPS construction, pulling wire is not an option now.

We found a very small, ducted mini-split system from EMI might work. True, it too is ~ 13 SEER, but for 10 days??? So what!

My desire to integrate HRV AND A/C seems to be unrealistic at this point.

Stay in touch; it's going to get better (;-o)

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Jeff Lawrence_25

Window shaker?

We have them down here for about $100.

I have a 110v 9K one that we lend out to customers when their AC goes out once they sign a contract. One gent complained that 'one unit isn't enough' and went to Wally-world and bought 2 more and returned them when wee got the AC back up and working.....

Ken_40

Costco as well...

A hundred bucks. Unfortunatly, the depth is good for windows only, not TTW. And since I have ~8" thick walls, need a $500 unit with the same capacity, just TTW style, I'm going with a ducted mini-split I suspect.

HRV's and A/C is so alien to my water based tunnel vision, I need all the help I can get here.

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Dave Yates (GrandPAH)_2

If a picture is worth 1,000 words.......

Ken,

The attached is from ISH in 05. Hope it helps a bit. Sounds like a fun project.

Ken_40

Who has one in the U.S. ?

This is excatly what we need!

http://www.airflow.de/Luftungsgerate/luftungsgerate.htm

The trout stream looks bleak. Not as a ground/water source, but as a direct chilled water medium...

For the 5-10 days a year we may need the A/C, ground/water surce is too costly.

Now the big question: How does one buy this thing here in the U.S.?

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Dave Yates (GrandPAH)_2

Try these outfits!

U.S.A F Kanomax USA Inc
P O Box 372
219 Route 206
Andover
NJ 07821 Tel: 973-786-6386
Fax: 973-786-7586
Email: info@kanomax-usa.com

U.S.A. V,F Innovative Products & Services LLC
211 Center Road
East Stroudsburg
PA 18301 Tel: 570-213-0470
Fax: 570-213-0480

Ken_40

Home Run?

The PA guy is history. The Andover guys are viable, but have no clue. They're instrument guys with a euro connection that looks excellent.

Here's the link: http://www.atrea.cz/?page=d1_intro_en

It appears oversized, but bypasses and recirc. may do the trick.

Thanks for all your help. I'll keep you in the loop. This is one helluva learning curve!

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Ken_40

As was the case with all reps, manufacturers, and dealers...

We have selected the parameters, models and make. It is made in the Chech Republic. The U.S.rep and manufacturer have become silent, don't return calls and we cannoty get a quote or ship-date.

I cannot believe the lack of response by wholesalers, manufacturer's and design people. If I knew half as much about HRV and A/C as I do about wet heat, this would have been home made, installed and running a month ago.

I hate depending on others for this kind of stuff. How many times have you tried to put $$$ is someone else's pocket, only to find they never return a call, much less order and deliver the goods.


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Henry_6

Free Cooling

> We have selected the parameters, models and make.

> It is made in the Chech Republic. The U.S.rep

> and manufacturer have become silent, don't return

> calls and we cannoty get a quote or

> ship-date.

>

> I cannot believe the lack of

> response by wholesalers, manufacturer's and

> design people. If I knew half as much about HRV

> and A/C as I do about wet heat, this would have

> been home made, installed and running a month

> ago.

>

> I hate depending on others for this kind

> of stuff. How many times have you tried to put

> $$$ is someone else's pocket, only to find they

> never return a call, much less order and deliver

> the goods.

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 504&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_



Hi Ken:
Maybe I missed a response, but why not use 1-2 gpm of well water at 49-50 degrees f through a cooling coil. While its not as good as chilled water, I am familiar with north/central Vermont and the well water is approximately that temperature. If your well is low output, you can recirculate the water back to the well and drain 10-15% to a drywell. You will find that your well temperature will not rise very much and since you are not running a compressor, your cost will be minimal. This would work well for the 5-10 days that you need it and as long as your home is as tight as you indicate, the dehumidification will happen as long as you do not introduce too much ventilation air when the RH is high.

Henry_6

Free Cooling

Hi Ken:
Maybe I missed a response, but why not use 1-2 gpm of well water at 49-50 degrees f through a cooling coil. While its not as good as chilled water, I am familiar with north/central Vermont and the well water is approximately that temperature. If your well is low output, you can recirculate the water back to the well and drain 10-15% to a drywell. You will find that your well temperature will not rise very much and since you are not running a compressor, your cost will be minimal. This would work well for the 5-10 days that you need it and as long as your home is as tight as you indicate, the dehumidification will happen as long as you do not introduce too much ventilation air when the RH is high.

Henry_6

Free Cooling

> We have selected the parameters, models and make.

> It is made in the Chech Republic. The U.S.rep

> and manufacturer have become silent, don't return

> calls and we cannoty get a quote or

> ship-date.

>

> I cannot believe the lack of

> response by wholesalers, manufacturer's and

> design people. If I knew half as much about HRV

> and A/C as I do about wet heat, this would have

> been home made, installed and running a month

> ago.

>

> I hate depending on others for this kind

> of stuff. How many times have you tried to put

> $$$ is someone else's pocket, only to find they

> never return a call, much less order and deliver

> the goods.

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 504&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

Henry_6

Free Cooling

Hi Ken:
Maybe I missed a response, but how about using artesian well water(1-2 gpm) through a cooling coil (4 row is better than 2) and set up a low airflow system to minimize the Delta T. With 5-10 days of usage and average water well temps in Central Vermont at 49-50 F, you could run this system and do Some dehumidification for almost nothing. If you have a prolific well, a fountain could be a landscape detail. If your well is limited, you could recirculate all but 10-15% back to the well, with the small quantity being discharged to a drywell. If you minimize the ventilation, you can get sufficient comfort for the cooling load that you describe. I am a big fan of using geothermal applications for heating and cooling and your description is a perfectly reasonable use of the technology. Contact me directly if you want to pursue this concept.

Ken_40

Artisian well?

Who's paying for that item? For 10 summer days a year?

If the trout stream's 60F temps won't allow dehumidification adequately, the Chech unit noted above is the ultimate solution.

Did you get a chance to see it?

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Ken_40

It now appears the euro unit...

is only 50 HZ, no 60's as options - yet.

May be a deal breaker. Although, DC motors are available.

The rep is supposed to get back today.

We'll see.

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Paul B_5

What is the cheapest way to dehumidify if your using water for cooling???

Ken_40

I'll bite?

Dehumidifier?

Dessicant?

Small nuclear device?

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Henry_6

Free A/C

> is only 50 HZ, no 60's as options - yet.

>

> May

> be a deal breaker. Although, DC motors are

> available.

>

> The rep is supposed to get back

> today.

>

> We'll see.

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 504&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_