I know what the two are, my question however is this,
What actually effects the ratings the most?
I'm under the impression its in this order:
I really don't think for A.C and Heat pumps that the compressors have
changed that much, have they? I'm speaking of course of r-22 units. What
has really changed from lets say 10 seer to a 12 seer? I see a larger coils
and due to that a smaller compressor, but did the compressors actually
Coils have grown to be enormous, compressors I don't think are changing that
much, and ID blower efficeincy (VS).
I am waiting for the new compressors they are using in the ductless, to be
used in regular split systems. Maybe the more engineering related posters
on here could input on the possibilities of that.
The same thing is happening with furnaces.
Trane is coming out with their new furnace next month, all they did was add
another heat exchanger pass. I think they are going to call it the XV95,
XV90's will be obsolete.
Several things occurred over the years.
1. Larger condenser's resulted in lowering the head pressure and raising
the sub-cooling some. This allowed for less horsepower needed. An increase
in sub-cooling gives better performance at the evaporator because of a
better adiabatic exchange. [Less latent heat].
2. The advent of the scroll compressor has reduced the power requirements
increasing the EER. The scroll has less moving parts and a scroll design
that allowed less liquid / vapor refrigerant to flow over those parts. Less
3. The return to TXV control has given the evaporators better performance
[although many refrigeration tech's have always known that TXV's give better
load / performance resulting in better superheat control. [Better superheat
control gives the compressor less compression ratio's and less oil sludging
from higher ratio's.] Also the use of "equalized port" gives better TXV
performance, and the use of positive shut off valve [keeps the liquid in the
condenser where it belongs on shut down.]
4. The increase of use for 2-speed compressors [staging is generally
referred but not necessarily correct.] This allows for lower power draw
during those days when air conditioning demand is relatively low.
"Geoman" < email@example.com> wrote in message
Great post! The only thing I question is the 2 stage compressors being a
true energy saver. I think they are more geared towards comfort issues than
anything else. They're savings over a 15-16 SEER singel stage system is
nominal during a cooling season, and their HSPF usually a little lower.
Interesting thread as I had been thinking about this for some time, but
got beaten to the punch in asking. I know the mfgs have gotten all the
"easy gains" they're going to get. Not mentioned yet is getting optimum
air flow through the condenser coil (ok- outdoor coil in the case of HP)
with the minimum power usuage by the motor, including using ECMs
outside. I have been wondering though, how much more efficient new
recips are compared to older and even REAL old ones, as in the old slow
speed Tecumseh B and JE models among others. Of course I have a
Frankenstein project in mind-- for my own use. Thanks Larry
The savings of 2-speed / 2-stage comes two fold.
1. Not having the equipment start and stop saving on high "in rush" current
during start up with each cycle.
2. When smaller amount(s) of cooling capacity is required, the compressor,
[and current draw] can match the load more closely.
What the manufacturer's have done commercially is make available 'staging'
compressors by 'unloading' cylinders. Why can't they do the same
residentially? They can and have. The problem though is cost. They can
"separate" the scroll plates and reduce capacity. They can unload recip's
cylinders and reduce capacity. But the cost currently on the resi market is
too high to do that.
Somewhere around the early 70's one manufacturer [G>E] produced a condenser
with two small compressors. The indoor section had two evaporators. One
furnace [air handler.] The only problem was cost. Energy was cheap. They
sold quite a few, but alias, the $$$ won and the design was scraped.
"Bob Pietrangelo" < firstname.lastname@example.org> wrote in message
With a two compressor system, I believe you will have more inrush,
especially during design temps. I am comparing overall capacity and
efficiencies between a 3.5T XL14i, and a 4T XL19i. The 19 has about 5000btu
higher capacity at 47 degrees (comparing heating cycle of a heat pump
system, cooling is slightly different but not dramatically), the capacity of
both at 17 degrees give the edge to the XL14i. The HSPF of the two is only
a difference of .01HSPF. I didn't compare the COP.
The amount of energy used to cool a space utilizize a 2 T compressor or a 4
T compressor is not much different That pretty much negates the energy
savings other than moving up in SEER about 1.5 points. The benefit of the 2T
is that it will run longer and make the house more comfortable, rather than
running at full capacity and not allow the system to properly cool all parts
of the house.
I strongly feel that the only benefit is on a comfort level to adapt to heat
There is one combination where the equipment combinations become greatly
increased, and that is down around 2.5 Tons w a drastically oversized id
.....and I think that is across the board with most manufacturers. Once you
get up in the 3.5-5 capacities they all fall into a more even playing field
efficiency wise, unless you are using aftermarket coils with false ratings.
I also find it comic that Carrier is touting the most efficient unit in the
industry, with Geothermal on the market. They are pricing their equipment
so close to Geo, life should be good. If only we could get loops
Zep, I am not trying to Dis you, I am enjoying the discussion.
The 14i is a single compressor single stage unit,
the 19i is a dual compressor 2 stage unit.
the 16i is a single compressor 2 stage unit that unloads approx 30-35%
The 16i wins on the HSPF factor per mfgrs lit.
I'm thinking this is because of the larger heat rejection from a single
compressor built to unload...
The HSPF is basically a seasonal COP calculated off the actual performance
of the unit as the outdoor temp varies throughout the season, though I'm
unsure what/where they're basing the design temps of the "test season"
The big change in compressor technology has been around for decades & is
Trane & Westinghouse both had inverter driven compressors years ago, in fact
Westinghouse had a system that was quite close to the modern Variable Flow
Refrigerant Zoning systems that Mitsubishi, Diakon, & Toshiba have on the
The combination of a soft starting inverter driven compressor & the linear
expansion valves that meter refr. flow to meet the actual load requirements,
means the flow is constant & the compressor idles along at a constant rate.
I've worked extensively with the Mitsubishi City Multi system commercially &
have even seen a couple of the R-series units used in large (very large)
The R-series incorporates a single outdoor unit that can serve up to 24
indoor units, w/sizes from 1/2 a ton up to 8 tons. The indoor units can
operate in either heating or cooling mode regardless of the other units
This allows for simultaneous heating & cooling off a single outdoor unit.
By routing the hot gas or cold liquid, via the branch controller, to the
calling units, the outdoor unit can idle down to approx 15% of rated
capacity, it can also be overdriven up to 130% of rated capacity to cover
The systems in operation throughout the US are showing a 25-30% savings in
cost of operation vs. roof tops & standard Nat. Gas & A/C airhandlers, VAV
The best part is, the City Multi line now includes a single phase 4 ton unit
that can support up to 8 indoor units with a connected capacity of 5 Tons.
Although this system is an "either/or" heat/cool unit that can only operate
in one mode at a time.
I'm hoping they'll incorporate a cupronickel coaxial watersource heat
exchanger that can be connected to a
geothermal loop system, & the industry will never be the same again...
Excellent post, thanks
I've never heard of a linear expansion valve, I might have them in the field
on some of our equipment and haven't noticed because nothing has failed.
As to the 8 indoor units, I'm assuming these are all split wall mount units,
The linear expansion valve has multiple positions (near 60, I think) & can
be monitored to
analyze the systems operation. Position of the valve will settle in to near
constant position as long as the load remains constant. As loads shift due
to solar loads or migrating students etc... the valve adjusts to the need &
the outdoor unit can ramp up or down as needed.
As for PTAC, Nah.
The wall mount unit is one of numerous indoor units.
There's a 1 way & 4 way ceiling cassette either recessed or suspended.
Serviceable from below & w/ built in condensate pumps (near 30" vert lift).
There's the wall mount, a ceiling surface mount, exposed & recessed wall
cabinet units, and ducted units from 1-8 tons. There are more styles coming
All of these indoor units can be used on the single phase 4 ton unit PUMY048
Check out mehvac.com under VFRZ CityMulti for submittals, tech, install,
3 Phase outdoor units, either R-series (simultaneous heat & cool) or
Y-series (either heating or cooling)
start at 72,000 btuh & go up to 234000 btuh.
They must have at least 50% connected capacity to operate, & can have 150%
They can overdrive about 30%, but the connected can be higher to cover the
shifting peak loads etc...
Meaning the 72 unit can have as few as 36000 & up to 108000 connected with a
max 93600 load...
The 234 unit, which I really like can go from 117000 up to 351000 (29.5
tons) & max oper. cap of 304000 btuh.
They've even got a couple water cooled units of 72000 & 96000 btuh.
They're brand new, but I've seen a little lit. on them.
Again, I'm waiting for a geoloop system interface & life will be good...
Great reply, and I might add these where my same conclusions. Technically, I
would love to see the manufactures get back into Hot water recovery on their
units with fan cycling to obtain higher seer's. Is there a manufacturer
that has this with an air source unit to date?
I further think that the next energy savings will not be coil size since
there is a limit as to how low you can get the high side pressures with
existing refrigerants. I think the next substantial savings will be a new
type refrigerant, one that will allow even lower head pressures and still
allow for maximum BTU removal with little circulation per pound.
Besides the scroll, I didn't think there was really a great difference in
compressor designs. If Danfoss can improve the electronics and magnets then
maybe they can get the cost down to move on with their bearingless
compressor for residential. I was told at ASHRAE in Chicago they have in
prototype a 5 ton unit that will fit in the service mans pocket! Amazing
So, to continue, with the current refrigerants, what do you see the maximum
What about new refrigerants that have different properties?
If memory serves, thermal efficiency has something to do with Delta-T....
and most of the systems today spend a LOT of energy moving the working
fluid/gas from one state to the other....and getting a high Delta-T. I
would think that by using a different fluid that didn't need as much force
to move from one state to the other, but using MORE of it...you could drive
efficiencies up more... Or not even do a state change... keep everything in
gas form, just hot/high pressure and cool/low pressure....
I can see some drawbacks... dehumidification would be one.... the other is
that you migh need to change the system overall pressure/charge from season
to season to move the ideal temperature points.... Thats another flaw of
the working fluid today, too wide a working zone... Ground source is an
example of the efficiencies that can be obtained if the working temperatures
are kept in a closer range...
Just some more fodder for discussion...
You are right Bob S. The stable ground temperature is what makes the ground
source heat pump work well, especially in colder climates. The COP is more
I honestly think what will come as "new" and "efficient" will be the
"electronic" heat transfer using the bubble effect of the electron. No
refrigerant needed. Currently you can find something along these lines at
the local auto store sold as a small ice box for your car. You just plug
'er in to the cigarette lighter and away she goes. If you reverse the plug,
you can create heat in the little box too. Efficient though? I don't think
right now. But maybe someday.
"Bob Sisson" < email@example.com> wrote in message
Very limited and very in efficient....
They use them commercially with slab chambers for coroner labs. I suppose
one reason is getting someone that would climb into one of those chambers to
weld a leak!
Seems that Borg Warner was the originator of the first ones out.
More about them here
I'm guessing Bob doesn't understand the reation that occurs during the flash
For Bob: --->Adiabatic change means that there is a change of state WITHOUT
the expense [cost] of energy. No energy is lost or added, just a change of
state with a change in heat from a sensible to a latent heat. So when the
flash point occurs, and the liquid is flashed, about 25% of the liquid
changes state to cool the remaining 75%. But with a high sub-cooling
effect, then there is less change. Somewhere around 20% flashing to
vapor... instead of 25% giving better performance. The big energy cost is
the compressor pumping the heat latent refrigerant back up to condensing
pressure to bring out the superheat. Check out a Mollier [my spelling may
be off] chart on your favorite refrigerant. You'll see what I mean.
Has anyone heard about those "superchargers" that used a small amount of
liquid to "refrigerate" the liquid before entering the metering device
giving a higher sub-cooling effect? There were some out in the early 80's
but I haven't seen any on the market. The theory then was the denser liquid
would provide better performance. Anyone?
Are you smoking dope? JUST KIDDING!!! Seriously, I haven't heard of the
'superchargers', but the
principal I assume is the same as a heat exchanger, to elliminate flash gas
at the TXV outlet to improve capacity/efficiency.
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