Residential Package unit and Chiller speculation

[xarralu]

Yea I've looked into the usual air cooled equipment, but unless you have a good sized buffer/storage tank your still going to have the temperature swings because your still banging compressors on and off...back to square one. Also, even in "quiet mode" they are still very noisy for a residential area. To answer your question, the absorption chiller is appealing in theory but it is way too expensive upfront. I have contacted that company and for what I could have two 3 ton systems changed out, I could buy the GAHP-AR machine! Mind you, it is very efficient but when do you see your ROI? 10 years? 15 years? Plus, who do you know that can work on an absorption chiller? (not me!)

What I would like to do is make ice with something like this. Only problem is they don't sell to the general public, only to utility companies! I believe with that equipment you could vary your CFM in your AHU without having to worry about freezing your coil and maintain setpoint.

[CraziFuzzy]

That seems pretty neat wonder if it cost an arm and a leg but I think that someone already makes a residential chiller.

It's already been mentioned in this thread, but there ARE actual residential chillers in production. Daikin, MultiAqua, ThermalFlow, Unico and WaterFurnace all make residential grade chiller equipment. Waterfurnace markets theirs as a geothermal water heater, but it is the same thing - you just use the 'chilled water' as the source, and the 'hot water' as the load...

[CraziFuzzy]

Yea I've looked into the usual air cooled equipment, but unless you have a good sized buffer/storage tank your still going to have the temperature swings because your still banging compressors on and off...back to square one. Also, even in "quiet mode" they are still very noisy for a residential area. To answer your question, the absorption chiller is appealing in theory but it is way too expensive upfront. I have contacted that company and for what I could have two 3 ton systems changed out, I could buy the GAHP-AR machine! Mind you, it is very efficient but when do you see your ROI? 10 years? 15 years? Plus, who do you know that can work on an absorption chiller? (not me!)

What I would like to do is make ice with something like this. Only problem is they don't sell to the general public, only to utility companies! I believe with that equipment you could vary your CFM in your AHU without having to worry about freezing your coil and maintain setpoint.

Actually, with a decoupling buffer tank, you don't have to have the temperature swings. The air handler can maintain a nice steady temperature control, and the chiller will cycle as needed to maintain the buffer's charge.

[motoguy128]

Yea I've looked into the usual air cooled equipment, but unless you have a good sized buffer/storage tank your still going to have the temperature swings because your still banging compressors on and off...back to square one. Also, even in "quiet mode" they are still very noisy for a residential area. To answer your question, the absorption chiller is appealing in theory but it is way too expensive upfront. I have contacted that company and for what I could have two 3 ton systems changed out, I could buy the GAHP-AR machine! Mind you, it is very efficient but when do you see your ROI? 10 years? 15 years? Plus, who do you know that can work on an absorption chiller? (not me!)

What I would like to do is make ice with something like this. Only problem is they don't sell to the general public, only to utility companies! I believe with that equipment you could vary your CFM in your AHU without having to worry about freezing your coil and maintain setpoint.

The goal is more for zoning and comfort, not direct energy savings.

The compressor can be 2 stage or use multiple compressors and refrigerant circuits. Very easy to split the heat exchanger into 2 circuits.

Why are they noisy? The condenser shouldn't be any different from a residential condenser. Eveen better, the condenser fan on a unit that generates hot water as well, should have a ECM motor and ramp down based on head pressure. At night in particular, it would be running at a pretty low rate.

We're not talking 150T+ screw machines. Those are very noisy.

+1 on the buffer tank. With just 50 gallons of storage, if you have a building that has a max load of 3 tons, and when at just 1/3 load, 12000 BTU's, with an unloading scroll... so 28000BTU output on low, it would cycle on and off in about 20 minute cycles with a 5-6F temperature swing if I did my math right. Now, let say 6000BTU's are used for hot water dehumidification. Now the condenser fan would just be poking along at maybe 50% speed.

[CraziFuzzy]

The goal is more for zoning and comfort, not direct energy savings.

The compressor can be 2 stage or use multiple compressors and refrigerant circuits. Very easy to split the heat exchanger into 2 circuits.

Why are they noisy? The condenser shouldn't be any different from a residential condenser. Eveen better, the condenser fan on a unit that generates hot water as well, should have a ECM motor and ramp down based on head pressure. At night in particular, it would be running at a pretty low rate.

We're not talking 150T+ screw machines. Those are very noisy.

+1 on the buffer tank. With just 50 gallons of storage, if you have a building that has a max load of 3 tons, and when at just 1/3 load, 12000 BTU's, with an unloading scroll... so 28000BTU output on low, it would cycle on and off in about 20 minute cycles with a 5-6F temperature swing if I did my math right.

Really, the buffer's capability is a function of the system's delta-t between chilled water supply and return. Larger delta-t, the greater amount of cooling the buffer can hold. With oversized coils, you can run with a very large delta-t (20°F+) and get a lot of buffering from your storage. A tall-skinny insulated storage tank would be perfect for this, as it would allow the tank itself to maintain some stratification. cold water at the bottom, warm water at the top. A couple temperature sensors over the length of the tank to determine the thermocline level would be the indicating factor in controlling the chiller's cycling (or staging).

[motoguy128]

So you put the storage on the return side. I'm used to primary/secondary system where the storage is the point where the 2 loops combine together. I figured in this case, the storage woudl be on the supply side and you'd store cold water. I do see how it's better to store return water and create a heat sink and have a wider temperature swing. The downside, is that the RWT would be lower on average at the chiller.

If you have a zone system, you would end up with a primary/secondary set-up anyway, sicne you'd want ot maintain water flow across the chiller, but wouldn't need as much flow to the zones.

Using delta T is a good way to modulate or stage a chiller.

[CraziFuzzy]

So you put the storage on the return side. I'm used to primary/secondary system where the storage is the point where the 2 loops combine together. I figured in this case, the storage would be on the supply side and you'd store cold water. I do see how it's better to store return water and create a heat sink and have a wider temperature swing. The downside, is that the RWT would be lower on average at the chiller.

If you have a zone system, you would end up with a primary/secondary set-up anyway, since you'd want to maintain water flow across the chiller, but wouldn't need as much flow to the zones.

Using delta T is a good way to modulate or stage a chiller.

No, I am talking about the storage being the decoulper between the primary and secondary, just as you describe. I'm just talking about using it as a stratified tank, using the stratification as the indicator of energy storage, and use THAT to stage the chiller.
Example:
Attachment 314291

[xarralu]

Actually, with a decoupling buffer tank, you don't have to have the temperature swings. The air handler can maintain a nice steady temperature control, and the chiller will cycle as needed to maintain the buffer's charge.

Exactly my point. You just basically said the same thing I did.

[Dallas Duster]

Exactly my point. You just basically said the same thing I did.

But don't you add the need for an extra chilled water pump? I think the important thing to do is keep it simple and straight forward lets not try to over think this. How was your training class?

[xarralu]

The goal is more for zoning and comfort, not direct energy savings. .

Correct, I was referencing the absorption chiller when I said that.

Why are they noisy? The condenser shouldn't be any different from a residential condenser. .

Not the machine that Dallas Duster posted the picture of! It would be too noisy for residential use.

[xarralu]

I just PM'd you Dallas. Without being able to quickly draw it out, I would only use one pump. I would use a three way valve at the chiller and the storage tank and maintain CHW delta T across the FCU(s). Give me a few and I will whip up my drawing

[CraziFuzzy]

While yes, it WOULD work with a single pump, it is not as flexible as a 2 pump system. This difference is even more significant when dealing with multiple 'secondary' zones. So, yes, decoupled would require a different pump, but with the 3-speed pumps on the market not costing much more than a single speed, I think I'd rather run a 3-speed pump on the secondary with a 3-stage t-stat, and no valve at all, than a single pump and 3-way valves. Remember, it's important that the system maximizes the delta-t to maximize the effectiveness of the buffer.

[xarralu]

If was able to do it, this is how my setup would look. Minimal amount of equipment to buy and maintain.