Residential Package unit and Chiller speculation

[CraziFuzzy]

That's a good point. For R410a, you'd have to get a HE rated for I think around 500psi however... and install the proper PRV if it's rating needs to be lover than the PRV at the compressor.

I wonder if you could even use an indirect tank as the heat exchanger. Then you'd have an evaporator and storage together. It would hurt efficeincy slightly, since you wouldn't have the higher tmep return water ging to the coil first. Although you'd still have soem stratification in hte tank where hte top of hte tank is warmer than the bottom.

Standard Refrigeration sells 'chiller kits', which include the shell and tube evaporator, txv, and controls, that can easily be installed to a standard condenser/compressor unit. they are all rated for R-410A pressures. (http://www.stanref.com/pdfs/CBChille...itBrochure.pdf). I think Alfa Laval also sells kits based on their brazed plate exchangers as well. Thermal Flow (http://www.thermalflow.net/greenm.htm) market a residential chilled water system no idea on the details though. Unico has started marketing a residential chiller system (calling it UniChiller). Many parts of the market ARE starting to take notice - I think the biggeset thing preventing the spread at THIS point is the lack of chiller/chilled-water knowledge of residential techs.

Carrier makes commerical air handlers down to 400 CFM nominal and can be had with chilled water and hot water coils. It looks like they have 2 returns, so you can use up to 100% outside air for economizing. The blower looks like it's after both the chilled and hot water coils. http://www.docs.hvacpartners.com/idc...it/39s-3pd.pdf

Of course there are plenty of commercial air handlers using chilled and hot water - the problem is that they are BUILT as commercial units - which means, in most cases, they are way over-built for residential use, and consequently, way too expensive.

[tedkidd]

Right on. The free cooling can double the amount of moisture removed the compressor verses conventional cooling.
The heat is 1050 btus per lbs. of moisture removed + 3414 btus per KW used = btus added to the air. The high efficiency of the deh means less heat added to the space. Keep in mind the heat from the dehu only occurs when the properly set up a/c is cycling on/off. So dehu does not add to the cooling unless reheat is needed to extend a/c dehumidification.
Regards TB

Now I'm feeling completely lost. It'll have to be dummed down for me to understand. Sorry.

I wonder if any of the major mfg's would ever consider modifiying their split systems to be packaged units with split condensers coils only, so you could reheat the air and even do as Ultra-Aire does and use a heat exchanger to increase moisture removal. THen it's jsut a matter of modulating the amount of vapor going ot reheat vs. the condenser coil.... which of course would require EXV's.

Then again, by the time you've done all that, you might as well just buy a chiller, keep your coil 45F and make hot water for reheat. A chiller eliminates the need for a dedicated dehmidifier, since airflow can be independant of system capacity. I know Crazi is on board with chillers for residential use. Though a WHD is still going ot be a little more economical in a small and medium sized home.

I think Climatemaster offers an optional reheat coil.

[motoguy128]

Now I'm feeling completely lost. It'll have to be dummed down for me to understand. Sorry.

You have ot think about surface tmepratures of the coil and heat exchanger. FOr efficeincy, you want a big coil area. But to get low dewpoints, you need a small surface area to get lower coil temps. So you put is a propoertionally larger coil, and you end up with lets say 50F surface temps and 55F air discharge. Efficient, but not a very good dehumidifier. Now, what if you flow that air across a heat exchanger and cool it to 55F. Now you flow the incomming air across that coil first. So now you're dropping the dewpoint of the incomming air. Further, that air is now dryer and cooler, so the evaporator will now be even colder, but you still retain that large surface area. The result is that for the same CFM, you will be able to use an even smaller compressor with the same coil size and achieve the same level of moisture removed.

It's in a sense liek the economizer or the secondary heat exchanger in a condensing boiler or furnace.

[tedkidd]

Air path:

In through HE - the other side of which sees evap exhaust

Precooled air through evap

out he as mentioned above

finally through condensor.

That it?

[motoguy128]

Air path:

In through HE - the other side of which sees evap exhaust

Precooled air through evap

out he as mentioned above

finally through condensor.

That it?

You got it.

Or... you needed the air even more dry without much more energy use, you'd add a dessicant wheel and run the incomming air across the condenser coil first to preheat it and drop the RH, then across the regen side of hte dessicant wheel, then the HE, evap, then the dry/regenerated side of the wheel. That would get your dewpoints around 0-20F. Add heat strips for the regeneration and you can see -60F dewpoints.

[dan sw fl]

Chillers are obviously used EXTENSIVELY in condos / high rises, retail and institutional.

[CraziFuzzy]

Chillers are obviously used EXTENSIVELY in condos / high rises, retail and institutional.

Of course they are. We're talking about smaller scale though - as in the <6 ton level.

[54regcab]

FirstCo only makes DX cooling coil units, no chilled water. Multiaqua makes some great looking units, including full whole-house 4-pipe air handlers to replace a conventional furnace/a-coil setup. This great thing about that particular unit (CWA4) is that it properly does the chilled water coil first, then the blower, then the hot water coil, allowing for dehumidification via simultaneous cooling and reheat.

The ones that my wife's used to sell were configured as 4 pipe units. For DX use they just added a TXV to one set of pipes. No distributors, just 1 circuit.

[motoguy128]

That's a good point, you could use a DX coil for chilled water, but you might have less capacity because of overall pipe size I think.

[CraziFuzzy]

The ones that my wife's used to sell were configured as 4 pipe units. For DX use they just added a TXV to one set of pipes. No distributors, just 1 circuit.

Yeah, I found them on the firstco site. They were listed only in the commercial section, as I should have expected - again, there-in lies the problem...

[jtrammel]

http://www.aquaproducts.us/home/reve...e-chiller.html

[jtrammel]

Yes, some company makes one, not sure of brand but we installed one at a church for a single fan coil unit when we converted the rest to dx. It was not feasible to get duct to this area and piping was already there. They make the condenser on a stand with the hx and storage tank built into stand, pretty neat set up

http://www.aquaproducts.us/chillers/...-chillers.html this is what we installed

[motoguy128]

I think they are stretching with the claim taht it will be more efficient that natural gas heating. How much better COP does the water cooled evap give you? Can you even get 120F water when it's 10F outside?

I thought the advantage of air cooled chillers was having a single central plant along with the dehumidification and building control benefits of chilled water... which is improtant when you are drawing in a lot of outdoor air for ventilation. Not as much the direct energy savings.


The nerd is me really would love to put on of these in when I replace my downstairs system in the next year or two, still install a furnace, but with a hydronic coil and use it as a dual fuel system and use an outdoor reset to adjust the hot water temeprature setpoint for capacity control and maybe even modulate chilled water temperature for humidity control.

I bet I don't even want ot see the prices. I'm guessing a carrier Greenspeed hybrid is looking competitive with it.