Multi-zoning driven by true variable speed air conditioning. Is it finally here?
- Thread starter NeverDie
- Start date
My ducts are square where the dampers are installed and they are close to the furnace/air handler, so you cannot hear them. I certainly do not hear them from any part of my home. The only way you can infer that they are moving is that when a set temp is reached in the larger zone, the algorithm first closes the zone and then modulates the airflow, instead first ramping it down and than adjusting the damper. Consequently sitting in the other zone you would notice a gradual increase in airflow, followed by a decrease. I am quite noise sensitive and this is within my tolerance (I had a condensation sump pump replaced by the dealer as the previous version had 1/3 gallon hold and frequent loud run that was heard throughout the house. It was awkward to call the dealer for it, but they recognize it and put it a larger one. It is still the loudest part of my HVAC system, but runs infrequently.
http://www.carrier.com/homecomfort/en/us/products/controls-and-thermostats/product---thermostats-and-controls---systxccitc01/ano said:
You will find it both under the 'Key Features' and 'Specifications' tabs reference to the SAM. It is not a separate product, rather an option to most thermostats.
Detailed product datasheet and install instruction can be found here: http://www.commercial.carrier.com/wcs/dynamiclit_result/1,2759,CLI1_DIV41_ETI4922_PRD1141,00.html
Note that there is a broadband version with RS232 and LAN ports, and wifi version with RS232 and wifi client, in either case the wired and wireless network part does not work with the newer touch control, but it does with previous not networked thermostats.
please note that the first itteration of this SAM instead of wired or wireless client, it had a 2G cellular client on it, called Skylink, so provided remote access even if homeowner had no internet service at all. I think this version has been now phased out, although some may still be in service.
NeverDie
Senior Member
For anyone curious as to what an ice bank looks like, here's a photo of one from National Geographic's "In Search of Green Air-Conditioning" article:
It's used by chiller's to save chilling capacity by using off-peak electricity and at night when the condenser operates more efficiently because ambient air temperature is lower. It also means that a chiller with less tonnage can be used. By serving as a buffer it could either moderate or possibly eliminate short cycling. You can buy them as standalone units or as integrated with a condenser as a packaged solution. It's too bad there's nothing similar for conventional residential air conditioners....
It's used by chiller's to save chilling capacity by using off-peak electricity and at night when the condenser operates more efficiently because ambient air temperature is lower. It also means that a chiller with less tonnage can be used. By serving as a buffer it could either moderate or possibly eliminate short cycling. You can buy them as standalone units or as integrated with a condenser as a packaged solution. It's too bad there's nothing similar for conventional residential air conditioners....
You'd be amazed. The chiller lines and ice are housed in super insulated containers, like a stainless oil tank with an inner bladder/tank, if you've ever seen them. The engineering I saw stated somewhere around a 20 hour time with zero input from the outside.ano said:
If I get a chance to go back and they have the duct out of the foundation, I'll take a few pics, otherwise it's considered a confined space, no entry without a permit and equipment and you can't break the plane. The vault ceilings are at least 8'-10' below grade, with the floor at least 12' below that. The thermal mass and distance before you even come close to the surface. A chiller doesn't really have to work that hard to get cold enough to start the process.
If you want, I'll see if I can get some guys from the HVAC side of the house to give you the basics on the system.
Its a good idea. Sorta like a hybrid car, but instead of a battery you are using ice. Also like a hybrid car its expensive, and I'm guessing a substantial payback period.DELInstallations said:
In my new house i'm going another route that I have had great luck with. Install LOTS of stone and tiles to make a substantial thermal mass. At night cool the house, and when the rates go up at noon, raise the temps. The mass of the stone and tile does the rest. And completely passive. It has saved over 1/3 of my electric bill in my current house, but it will work even better in my new house designed for that.
On a new build out it really isn't that bad, considering the excavation is still going to happen, and it's either going with cooling towers or economizer layouts or you build the heat sink (lack of a better term) and install some basic hardware and toss some drainage and other similar equipment in. The parts cost is going to be similar within a percentage, however the energy savings (especially in one of the most expensive markets out there) is going to give a good ROI. Factor in a price structure with the utility with demand based pricing, it's going to break even faster.
You both mentioned the thermal mass, can you explain how is this more efficient than a closed loop geothermal heat-pump?
However big the chiller is, will not reach the thermal mass of 400-500 feet of ground.
And as ano mentioned, when the low temperature is ~100 degrees, dumping the heat somewhere to chill your chiller is the issue.
However big the chiller is, will not reach the thermal mass of 400-500 feet of ground.
And as ano mentioned, when the low temperature is ~100 degrees, dumping the heat somewhere to chill your chiller is the issue.
NeverDie
Senior Member
ano said:
In that case, what will really blow your mind is that the particular model of ice bank in the photo above is typically installed in an exposed, unshaded location on top of a roof. Here's a photo of what the installed packaged unit (ice bank plus condenser) from that manufacturer looks like:
On first blush, it seems totally crazy doesn't it?. It has a dark lid that in Phoenix you can probably fry an egg on, and they didn't even bother to paint the whole thing white. So, you're probably thinking it's like a snowball in hell. However, then ask yourself how thick the walls of a styrofoam cup would have to be for your hand to have absolutely no sensation at all that there's boiling water within the cup. It's a roughly similar temperature differential.
I'm not sure how thick the insulation is on their standardized ice bank, but it's probably at least a couple inches of foam insulation, and I'm guessing more like 3 or 4 inches, and probably the only thermal bridging is the pipe that makes the connection. I would agree that it's not immediately intuitive, but I can also see how a sufficient amount of insulation could tame even Arizona heat.
I was interested about this and found this video that explains the ice banking.
So perhaps it is best described as an electrical demand management, where the peak demand is shifted to off-peak hours.
Overall, the additional freeze/thaw cycle likely has some minimal losses, but pays for utility and consumer by shifting demand.
As a residential customer, I pay the same price regardless when I use the power, the only factor is the amount of power used, that is the more I use, the more I pay even in unit price. So such a unit would not save me any, unless the utility would put it on a separate meter, and manage its curtailment for their purposes. For the amount of power a residential home uses this likely is cost prohibitive.
http://www.youtube.com/watch?v=FnQSURnzPHQ
So perhaps it is best described as an electrical demand management, where the peak demand is shifted to off-peak hours.
Overall, the additional freeze/thaw cycle likely has some minimal losses, but pays for utility and consumer by shifting demand.
As a residential customer, I pay the same price regardless when I use the power, the only factor is the amount of power used, that is the more I use, the more I pay even in unit price. So such a unit would not save me any, unless the utility would put it on a separate meter, and manage its curtailment for their purposes. For the amount of power a residential home uses this likely is cost prohibitive.
http://www.youtube.com/watch?v=FnQSURnzPHQ
NeverDie
Senior Member
That's probably the main selling point for commercial customers. Like you, my electric rates are flat, so it's not compelling for me. However, there may be other benefits, and the first directly relates to this thread (which is why I brought up the topic in the first place):lleo said:
1. Matching between cooling demand and supply. If just one small zone or even a larger number want to be cooled, you can do it from the ice bank. You don't need to start up the condenser as you would in a non-chiller system. So, potentially, less short cycling.
2. You can use a smaller condenser and just run it longer. IIRC, for single speed condensers, the 2 or 3 ton units are more efficient than the 5 ton units. I'm not sure what the efficiencies are of the two-speed and variable speed systems, but I'd like to find out.
3. The ambient air temperature is cooler at night, so it should take less energy to run the condenser at night than at the peak heat of the day.
Are these significant enough to move the needle significantly on the NPV calculation? I'd actually like to know. A case study would be useful. It doesn't look easy to figure or even estimate the answer, and it obviously depends on the specifics of what the costs are and local climate.
The ice bank in the first photo above looks elegant. There are less sophisticated ice banks that are just insulated tanks filled with liquid filled plastic spheres. Those look to be a lot cheaper. I presume they don't work as well, but maybe they work well enough.
I've been lurking on this topic for awhile - interesting "additions" in the area of variable speed condensors and control systems. I say "additions" because I have yet to see a study that provides actual numbers on energy savings.
On the latest topic:
Reduced ambient air temperatures at the condensor result in lower system pressures and a direct reduction of power.
Couple of articles that focus on EER vs condensor temperature:
http://www.fsec.ucf.edu/en/publications/html/FSEC-PF-302-96/
https://www.aceee.org/files/proceedings/2010/data/papers/1924.pdf
My turn for a question - Why not ground source heat pumps? Is there something about the soil structure that prohibits their use in the Southwest?
I love these things from a technical perspective - they just don't make much sense in my area where 90% of my cost is heating. Natural gas is still a much better bang for the buck. I would think these would provide a decent ROI in the Southwest where cooling predominates. What am I missing?
On the latest topic:
Reduced ambient air temperatures at the condensor result in lower system pressures and a direct reduction of power.
Couple of articles that focus on EER vs condensor temperature:
http://www.fsec.ucf.edu/en/publications/html/FSEC-PF-302-96/
https://www.aceee.org/files/proceedings/2010/data/papers/1924.pdf
My turn for a question - Why not ground source heat pumps? Is there something about the soil structure that prohibits their use in the Southwest?
I love these things from a technical perspective - they just don't make much sense in my area where 90% of my cost is heating. Natural gas is still a much better bang for the buck. I would think these would provide a decent ROI in the Southwest where cooling predominates. What am I missing?
NeverDie
Senior Member
At least in lleo's case (though he's not in the SW), the cost of boring the hole was a stumbling block. Do you have other datapoints on that?IndyMike said:
On the preceeding topic of ice banks, I'm now realizing there's going to be inefficiency in producing the colder temperature needed to make ice versus the less cold temperatures for chilling air. So, it may still be a win, but it's not the easy win it might have been in terms of making a very simple and efficient system.
I ran some back-of-the-envelope numbers today on the relative cost of running a natural gas powered ammonia chiller, and so I had to plug-in my utility rates to do the calculation. I'm paying about 10.4 cents per kilowatt-hour and last month's rate for natural gas was $0.51/CCF. My electricity rate is rock steady, but my natural gas rate bounces all over the map and has varied from about $0.31/CCF to $0.61/CCF over the last couple of years. For whatever reason, I hadn't noticed these rate variations until I looked at an archive stack of utility bills all at once. Have you guys noticed similar fluctuations in your NG rates? Looks like I'm paying whatever the spot-market rate is for NG each month. I'm surprised it's not rock steady like my electricity rates.