Residential Package unit and Chiller speculation

[motoguy128]

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.

[CraziFuzzy]

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.

If packaged units made sense for homes, there's be more of them out there - it is cheaper to make a packaged unit than a split system. They just don't makes sense the way architects design homes in most cases. If that changes, then yes, a split condenser would make for a very good dehumidifier, especially with a smart control, that way it could seemlessly cycle between cooling mode, and dehumidification mode, while working on the same air stream. That said, since architects DO like split systems (because of freedom of placement), that's the same reason I like chilled water.. :-)

Whd's do make sense when moisture removal is all you are looking for. That said, if you are wanting to use chilled water for dehumidification, you don't actually HAVE to use hot water for the reheat, you can actually use the chilled water return as the reheat. With two chilled water coils, and a 3-way solenoid valves, you can switch them from cooling only, to dehumidification without cooling.

I'm still not convinced that chilled water doesn't work in a small/medium sized home. The only reason it doesn't make sense right now is market, not technical. There just isn't enough small chiller systems on the market for their price to drop. You can custom build a small chiller for very cheap - but a mass produced one would be a lot cheaper, and if you subtract the cost of duct installation and go with a couple small fan coils, it is probably not a lot more than a traditional split system. PEX tubing is the key thing that has changed in the market to allow this.

This exact scenario points to the key advantage of hydronic systems. Once the system's head ends are in place (be it a boiler or chiller), all it takes is coils and valves and that cold/hot water can be manipulated in so many different ways that any comfort scenario can be handled easily.

[jtrammel]

In my market package units are very common in residential, probably 50+% of homes have package units

[CraziFuzzy]

In my market package units are very common in residential, probably 50+% of homes have package units

Are those A/C's with gas heat, or heat pump heating? I'm wondering if that is the difference... as I said, around here in SoCal, gas is so cheap, there are very few heat pumps - just about every home has an oversized gas fired furnace, feeding through a split A-coil.

[udarrell]

I get 18,500 Btus of sensible heat gain and 3,500 Btus of latent gain. I like Ruud/Rheem equipment, and when I look at the specs for their hardware a 2-ton unit does look like enough even for the very hot, humid days we get here in Virginia.

At 85-F ambient, 75-IDB & 63F IWB a 2-Ton Goodman 13-SEER with just a piston metering device; at 700-CFM, it gets 20,200 total at an S/T of 0.73, or 14,746 sensible & 5,454 latent.

You need to figure out what the sensible load is at 85-F ambient & how much air infiltration you have; which will also depend on wind conditions & the ambient humidity level at 85-F.

You also need a room stat that will provide some degrees of temp swing for longer runtime periods; indoor fan should cycle off with condenser & you need a TXV metering device on a 2-Ton evaporator.

I also agree in general with Teddy Bear's statements...

[jtrammel]

Are those A/C's with gas heat, or heat pump heating? I'm wondering if that is the difference... as I said, around here in SoCal, gas is so cheap, there are very few heat pumps - just about every home has an oversized gas fired furnace, feeding through a split A-coil.

probably about 60%gas/electric 35% heat pump 5% dual fuel on residential package equipment

[54regcab]

Package units are typical on older homes in our area that didn't have central heat at the time of construction. Package units aren't used on homes made after 1970 or so in our area.

The home chiller is VERY interesting. A few other bonuses are when it comes time for system replacement the indoor units don't have to be replaced at the same time as the outside unit. No ductwork looses. Easy zoning. Easy to heat cool additions w/o new equipment. The same water used to cool the space could be used to heat it. Heat could come from heat pump or gas/oil. Whole home dual fuel becomes easy. Domestic hot water could be provided by chiller. Geothermal/Miniature cooling towers become practical. The advantages go on, it's just a matter of somebody coming up with a cost effective unit in smaller sizes.

[CraziFuzzy]

Package units are typical on older homes in our area that didn't have central heat at the time of construction. Package units aren't used on homes made after 1970 or so in our area.

The home chiller is VERY interesting. A few other bonuses are when it comes time for system replacement the indoor units don't have to be replaced at the same time as the outside unit. No ductwork looses. Easy zoning. Easy to heat cool additions w/o new equipment. The same water used to cool the space could be used to heat it. Heat could come from heat pump or gas/oil. Whole home dual fuel becomes easy. Domestic hot water could be provided by chiller. Geothermal/Miniature cooling towers become practical. The advantages go on, it's just a matter of somebody coming up with a cost effective unit in smaller sizes.

It would take less innovation than you might think. All it takes to turn a conventional outdoor compressor/condenser unit into a chiller is to connect it to a TXV and heat exchanger (either shell and tube, or brazed plate). The chilled water system itself is also not anything new, as cheap fancoils are already made and readily available in sizes small enough match residential uses, including nice small ceiling mount concealed units, that just need power, t-stat, chilled/hot water, and a condensate drain. Circ pumps, expansion tanks, control valves, are already used in hydronic heating systems. Even conventional hot water tanks makes a very good chilled water buffer tank to avoid excessive chiller cycling. Not the easiest retrofit to an existing home, and some of the savings aren't there, but in a new construction, I don't think I would ever have a home built with conventional ducting at this point.

[54regcab]

It would take less innovation than you might think. All it takes to turn a conventional outdoor compressor/condenser unit into a chiller is to connect it to a TXV and heat exchanger (either shell and tube, or brazed plate). The chilled water system itself is also not anything new, as cheap fancoils are already made and readily available in sizes small enough match residential uses, including nice small ceiling mount concealed units, that just need power, t-stat, chilled/hot water, and a condensate drain. Circ pumps, expansion tanks, control valves, are already used in hydronic heating systems. Even conventional hot water tanks makes a very good chilled water buffer tank to avoid excessive chiller cycling. Not the easiest retrofit to an existing home, and some of the savings aren't there, but in a new construction, I don't think I would ever have a home built with conventional ducting at this point.

My wife used to work at a place that manufactured fan coil units. House I was living at didn't have central heat/air. Got a 600CFM "lab unit" for free and hooked it to the existing gas water heater. The unit had a 5 row coil, 2 rows for hot water, 3 rows hooked to a TXV and a 1.5 ton condenser. System was still in service when I sold the house. Front of the coil is VERY easy to get to on these units, making them easy to clean. The guys at my wife's work thought I was nuts, but were surprised when they saw it work. Now if they would only market to residential customers like FirstCO does...

[CraziFuzzy]

My wife used to work at a place that manufactured fan coil units. House I was living at didn't have central heat/air. Got a 600CFM "lab unit" for free and hooked it to the existing gas water heater. The unit had a 5 row coil, 2 rows for hot water, 3 rows hooked to a TXV and a 1.5 ton condenser. System was still in service when I sold the house. Front of the coil is VERY easy to get to on these units, making them easy to clean. The guys at my wife's work thought I was nuts, but were surprised when they saw it work. Now if they would only market to residential customers like FirstCO does...

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.

[motoguy128]

It would take less innovation than you might think. All it takes to turn a conventional outdoor compressor/condenser unit into a chiller is to connect it to a TXV and heat exchanger (either shell and tube, or brazed plate). The chilled water system itself is also not anything new, as cheap fancoils are already made and readily available in sizes small enough match residential uses, including nice small ceiling mount concealed units, that just need power, t-stat, chilled/hot water, and a condensate drain. Circ pumps, expansion tanks, control valves, are already used in hydronic heating systems. Even conventional hot water tanks makes a very good chilled water buffer tank to avoid excessive chiller cycling. Not the easiest retrofit to an existing home, and some of the savings aren't there, but in a new construction, I don't think I would ever have a home built with conventional ducting at this point.

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.

[jtrammel]

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.

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

[motoguy128]

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.

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