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No, you would not need a separate dehumidifier with a properly controlled chilled water system. The key is having reheat after the cooling (which is the only thing that makes a dehumidifier different than an air conditioner). With dehumidifiers, it used condenser heat for the reheat. With chilled water, it can use hot water, of chilled water return. As mentioned earlier, chilled water is NOT common YET in residential construction (not by the volume numbers). But it is used often enough in larger or higher dollar that require many zones, and the components are available. Recirculating water (hydronic) systems are very common in homes, so most the components are made in very high volumes. The difference is most of those hydronic systems are used for heating instead of cooling. Most the components are universal between heating and cooling (pumps, tanks, valves, etc). The only difference is the temperature of the water flowing through them. The manufacturers that make the chillers (multiaqua, unico, etc) also make the other 'specialty' components required - the 4-pipe (for cooling and reheat) fan coils, and/or air handlers. Controls on a system like this is going to be a 'custom' - albeit relatively simple - design - but it's the controls that directly give you the comfort gains.Originally Posted by Bear_in_HOU
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I oversee equipment for an art museum where humidity control is crucial to protect the collection. We do almost all of it with chilled water. The only place we don't is in a cold vault kept at 20 degrees, where we use a desiccant wheel instead. So yes, you can control a building's temperature and humidity nicely with chilled water. It's all in how you set everything up to do it.
Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.
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Fresh air should go through the AHU or a dehumidifier first to condition it before it hits the space. A slight positive pressure helps keep infiltration rates down. Infiltration is outside air that does not go through the unit first and is a source of heat gain/loss, drafts, and humidity. It's better to remove the humidity before it can work into furniture, paper, clothes, etc in a room.
Zoning with air is an option with chilled water but you may get better diversity for outdoor unit size reduction out of FC units. Also, another thing to consider is that piping is a more efficient form of energy transfer than ductwork by far (look at the size of a pipe verses a duct to carry the same btuh).
Look at circulators like the Grundfos Alpha that can adapt flow as the units are satisfied and valves close. This eliminates the need for or can reduce the size of a bypass valve on a small chilled water system and saves energy by reducing rpms automatically as flow is reduced. Reduces or eliminates the need for balancing the system other than a basic setup.
http://www.pexsupply.com/Grundfos-59...irculator-Pump
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are cost differences between water cooled and mini split close
or would cost be closer to regular hvac system?
I'm reading & learning too. the only water cooled centrals I've
seen in resi is freus units. more in commercial and of course larger
setups.
just trying to get an idea of cost comparisms without violating rules.
great postings crazifuzzy & all.
The cure of the part should not be attempted without the cure of the whole. ~Plato
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Agree on both of these last points.
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You might notice that I keep mentioning equipment diversity as a potential for cost savings with the mini chiller setup. I had a high mass building with 18" thick uninsulated walls that I designed a mini chiller system for. I performed a Life Cycle Cost Analysis of the mini chiller, VRF, and thru window AC units, (ducting was not an option due to lack of ceiling space, so a central station AHU was not an option).
The existing system was 12 (1/2, 3/4, 1 ton) window units over 3 floors totaling about 9 tons connected load approximately 5 tons actual with diversity and varying peak times, infrastructure for window units was all in place (electrical connections, window supports etc). So window units won hands down as the lowest equipment cost first cost option. VRF allowed us to use a 7.5 ton outdoor unit (diversity allowes for up to 130% connected load on a VRF system), the chilled water calculations showed that as long as the system was allowed to operate fairly continuously 24/7 and included a buffer tank, we could add 2 rooms for a total of 6.5 tons actual load and 11 tons connected load and reduce the outdoor unit to a 5 ton heat pump chiller, becoming the lowest life cycle cost option and the system that was installed. With the thick walls contributing flywheel effect and a small buffer tank, the system operates just fine.
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If I remember correctly, the equipment costs are similar for equally sized VRF and mini chiller, but the mini chiller sales guy claimed lower installation costs, especially if PEX piping is used.
He also claimed lower maintenance costs because VRF systems are largely proprietary and much of the service and parts have to come from the equipment vendor using factory certified technicians. These mini chillers are not as complicated. They just make cold water, not precisely meter out refrigerant as needed.
The Mechanical contractor for my chiller installation mentioned above kept telling me he loved the mini chiller system, by the way.
Last edited by vangoghsear; 06-25-2013 at 05:29 PM.
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How big of a buffering tank did (do?) you use and are there any specific kinds of insulated tank that are better for this? Quick math seems to indicate that a 50gal tank provides about 10K BTU of reserves with a 72*F setpoint. Of course, there will be standby losses, and I'd expect to want/need a decent reserve for the hottest days. A very interesting idea!
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Heck, I would just appreciate an invitation to the party when the installation begins, this will be one of those "seeing is believing" installs no doubt "if" it all works out. Of course the a/c system cost may tower over the complete home build cost by the time it's all said and done, but what the heck, it's only money and you can't put a price on comfort, right?
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“Experience is a hard teacher because she gives the test first, the lesson afterwards" ~ Vernon Law
"It's what you learn after you know it all that counts." ~ John Wooden
"When the teachers become unteachable we're all in trouble" ~ Mr. Bill
"Remember "Pro" is only a name, it's not always a mindset determined to do everything correctly" ~ Mr. Bill
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So what part of the system is going to add this exorbitant cost? This is not some experiment in new technology, it's applying tried and true technology to a different sized envelope. Thermodynamics work regardless of the size.Heck, I would just appreciate an invitation to the party when the installation begins, this will be one of those "seeing is believing" installs no doubt "if" it all works out. Of course the a/c system cost may tower over the complete home build cost by the time it's all said and done, but what the heck, it's only money and you can't put a price on comfort, right?
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Famous last words! My first question might be, were is he going to find someone in Houston to do this? after you answer this, I have another question for you.
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“Experience is a hard teacher because she gives the test first, the lesson afterwards" ~ Vernon Law
"It's what you learn after you know it all that counts." ~ John Wooden
"When the teachers become unteachable we're all in trouble" ~ Mr. Bill
"Remember "Pro" is only a name, it's not always a mindset determined to do everything correctly" ~ Mr. Bill
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Just about any insulated tank should suffice. There is no reason it couldn't be a standard hot water storage tank. The sizing would simply affect the cycle time of the chiller, ideally. Larger tank, longer cycle times. Comfort levels would be unaffected either way, just so long as it is piped correctly. (Ideally, the air handler would always see the ~42°F water). The amount of buffer for a given sized tank is a function of the difference between the chilled water supply and return temps. Larger temp difference, and the more BTU's a given gallon of storage will provide. A taller/skinnier tank will provide a better stratification between the cold supply water at the bottom and the warm return water at the top.
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We did already discuss that in this very thread. The goal would be to find a company that does both residential and commercial work - that would at least get a residential tech that isn't afraid of water. He also already contacted unico (who actually specialize in this exact same thing) to find a dealer in his area. You are proving the exact reason (a completely non-technical reason) why there is little chilled water in the residential market - if the pro's don't even understand why it should be used, the manufacturers aren't going to jump onto it.
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So it's my fault, if I am just asking questions about some non existent "in Houston", hypothetical system, that probably has less than 1% of the market, and not even the city of Houston inspection crew would even know how to inspect? You don't know me well enough to judge me, I have built computers of all kinds as a hobby for the past 20 years, just because I do like to stay on the cutting edge of modern technology, stereotyping folks never helps any progress period.
__________________________________________________ _______________________
“Experience is a hard teacher because she gives the test first, the lesson afterwards" ~ Vernon Law
"It's what you learn after you know it all that counts." ~ John Wooden
"When the teachers become unteachable we're all in trouble" ~ Mr. Bill
"Remember "Pro" is only a name, it's not always a mindset determined to do everything correctly" ~ Mr. Bill
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So we are responsible for creating the demand? I don't have the advertising dollars to do this, who/what created the demand for conventional a/c systems? I would say the heat did, not us.
__________________________________________________ _______________________
“Experience is a hard teacher because she gives the test first, the lesson afterwards" ~ Vernon Law
"It's what you learn after you know it all that counts." ~ John Wooden
"When the teachers become unteachable we're all in trouble" ~ Mr. Bill
"Remember "Pro" is only a name, it's not always a mindset determined to do everything correctly" ~ Mr. Bill
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We had a lot of system volume contributing as well. We used oversized 2" headers all through the 1st floor and had quite a length of run outs (light institutional project). I think it was about a 30 gallon tank, but overall we ended up with around 10 gallons per ton, which is okay capacity for comfort cooling when precise control is not important. Don't try for as much diversity as I used I had major load shifts, a dining hall, meeting rooms, and 18" walls in my building, when people were in the dining hall they weren't in their offices. A large tank allows you to run the temp down in the system water during nighttime when it's generally cooler and no sun load on the building. You may be able to set the controls to take the tank water down extra low at night before the load increases again.
Most of the companies I would use for equipment such as the tank would be commercial, such as Wessels, or John Wood. These are going to be ASME rated and require PR valves (my commercial customers require it often even when not required by code, I'm not familiar enough with residential to know at what size it becomes a requirement).
There may be some mechanical contractors that do hydronic solar, that may also do this type of installation in your area. The components including the storage aspects, expansion and air control and freeze protection requirements, are very similar.
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I think before we call in NASA for theirwe should move off track a bit to operating costs, with a single-phase system. Of course this idea is great were you have a 600 volt 3Ph system or even a 440 volt 3Ph available. Maybe operating costs might be such a contrast, between water and conventional systems on the 1Ph market, might be why the mfg. have not invested R&D into this application. There must be some reason, I am not buying it's us.
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“Experience is a hard teacher because she gives the test first, the lesson afterwards" ~ Vernon Law
"It's what you learn after you know it all that counts." ~ John Wooden
"When the teachers become unteachable we're all in trouble" ~ Mr. Bill
"Remember "Pro" is only a name, it's not always a mindset determined to do everything correctly" ~ Mr. Bill
Professional Member*
Your comment directly creates a negative demand effect. You make the assumption that it is too expensive to come to reality, implying it would cost more than the house. When I challenged that assumption, and requested clarification, you got even more sarcastic, stating that the customer will never find anyone in houston to do it (when there are likely 100's of thousands of chilled water systems purring away in the greater Houston area). High end A/C systems are sold by small companies and the techs that install them.
Those consumers who visit this board, and especially those who are interested in the building science, should be encouraged to ask the questions that will further the market along, not to settle with what has already been the answer given to every uneducated potential customer by lazy minded salesmen for the last 40 years. Most of the advances in residential systems for the last 20 years (2 stage/variable speed compressors, mini-splits, kludgy zoning systems, whole home dehumidifiers, and so on) are all workarounds to the flaws in DX cooling. All flaws that are not an issue in chilled water based systems. I have not even brought up the nationwide problems of peak electrical demand, and the ease of load shifting the acceptance of chilled water provides.
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Are you thinking this is installing a 400 ton centrifugal chiller here? The only component that is different between a residential mini-split, and these chiller systems, are the evaporator. The pumps used in these system are highly available - even in the exotic 120V-60Hz-1ø found in homes - made by large companies (watts, Taco, B&G, etc). Again, you are making assertions that it will be expensive, and stating high operating costs, without saying WHY you feel that way. This is a classic example of how FUD affects the marketplace, and the advancement of technology.I think before we call in NASA for their
I feel the biggest reason the 'old school' techs are against this, is because the chillers themselves are too much of an appliance, with no refrigeration work required for the install - which means if they DO make it into the market, joe handyman will be able to easily install them.
Perhaps you should contemplate the meaning of your signature: "The critic is a prisoner to his own experiences and perspectives, erroneously believing his limited experiences are the sum of all truth".
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And I agree! but if it were me no matter how scientific I was about it, I would like to see both the pros and cons of something like this, so I could make a decision based on my ability to understand. I am not saying this application will not work in a residential application, I just would like to know why it has not been implemented into the market more, and as I said I am not buying it's our fault. If the application is really worthy of all your fuss, and is more economical, and just makes better sense than all the newer technology conventional systems, maybe you should petition the White House to get your message out. They might even make up some high paying job to give you, this is what they do anyway right?
__________________________________________________ _______________________
“Experience is a hard teacher because she gives the test first, the lesson afterwards" ~ Vernon Law
"It's what you learn after you know it all that counts." ~ John Wooden
"When the teachers become unteachable we're all in trouble" ~ Mr. Bill
"Remember "Pro" is only a name, it's not always a mindset determined to do everything correctly" ~ Mr. Bill
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