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COP/SEER question Geoman 06-23-2007
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Posted by Geoman on June 27, 2007, 7:57 pm

> Thanks,
> 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
> as well.
> All of these indoor units can be used on the single phase 4 ton unit
> PUMY048
> (S-series)
>
> Check out mehvac.com under VFRZ CityMulti for submittals, tech, install,
> etc...
>
> 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%
> connected capacity.
> 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...
>
> goodluck
> geothermaljones
> st.paul,mn.
>

I will certainly check those things out after this summer rush.

BTW, welcome to the group.

Rich
>



Posted by geothermaljones on June 29, 2007, 7:04 pm
Been here for years...
Just got sick of a few feuding idiots...


>
> > Thanks,
> > 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
> > as well.
> > All of these indoor units can be used on the single phase 4 ton unit
> > PUMY048
> > (S-series)
> >
> > Check out mehvac.com under VFRZ CityMulti for submittals, tech, install,
> > etc...
> >
> > 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%
> > connected capacity.
> > 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...
> >
> > goodluck
> > geothermaljones
> > st.paul,mn.
> >
>
> I will certainly check those things out after this summer rush.
>
> BTW, welcome to the group.
>
> Rich
> >
>
>



Posted by Geoman on June 25, 2007, 10:52 am

> 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
> friction.
>
> 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.
>
> --
> Zyp

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
for sure.

So, to continue, with the current refrigerants, what do you see the maximum
SEER/COP obtainable?

Rich



Posted by Bob Sisson on June 25, 2007, 12:25 pm
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...

Bob Sisson




Posted by Zephyr on June 25, 2007, 9:52 pm
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
consistent.

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.

--
Zyp

> 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...
>
> Bob Sisson
>
>
>



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