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Posted by geothermaljones on June 27, 2007, 10:41 am
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%
capacity.
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
slowly resurging.
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
market now.
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)
residential applications.
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
operation mode.
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 extremes.
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
reheats etc..
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...
good luck
geothermaljones
st.paul,mn.
> 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
> gain.
>
> There is one combination where the equipment combinations become greatly
> increased, and that is down around 2.5 Tons w a drastically oversized id
> coil.
>
> .....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
> subsidized!
>
> Zep, I am not trying to Dis you, I am enjoying the discussion.
>
> > 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.
> >
> > --
> > Zyp
>
>
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