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Posted by Lloyd E. Sponenburgh on June 1, 2007, 7:27 am
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> ** Attention**
> Do NOT listen to Lloyd. No matter what he thinks........
> Expansion valves do NOT TALK!
> Bubba :-)
WAIT a minute, Bubba! Even you have heard one SING once in a while! <G>
LLoyd
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Posted by Noon-Air on May 31, 2007, 1:27 pm
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> This is an extension of my question a while back out variable speed
> compressors.
> (Does anyone make a residential variable speed compressor in the 4 tonn
> range)
> (Not 2-speed or multi-compressor, true multi-speed like some of the
> ductless, or commercial)
Copeland has a 2 stage scroll compressor that is used in all of the 16SEER
Rheem/RUUD Prestige Series systems.
show/hide quoted text
> How does the expansion valve deal with variable liquid flow rates? I
> would thing that at one flow you would get good expansion, but at too
> higher or lower you might have problems. How do the commercial units deal
> with the change if flow rates through the expansion valves, as I thought
> the expansion valves were tied to the flow, which would be tied to the
> compressor....
Rheem/RUUD uses microprocessors to control ECM fan and blower motors to
compensate for the refrigerant flow rates.
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> I know that several manufactures make a big deal about their expansion
> "metering" values and was wondering how they fit into the grand scheme of
> the system.
They are designed to work with specific applications.
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> Bob
>
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Posted by Tony on May 31, 2007, 5:46 pm
> This is an extension of my question a while back out variable speed
> compressors.
Copeland Scroll Digital technology provides infinitely variable capacity
modulation and is ideal for commercial applications with widely varying
loads and a need to maintain precise temperature and humidity control. It
offers an innovative way to modulate the capacity of the compressor from 10
to 100 percent, so that the output precisely matches the changing cooling
demand of the room, and it does this without changing the speed of the
motor. This approach to capacity modulation is as much as 30 percent more
efficient than traditional hot-gas bypass and is capable of holding a
precise temperature to within half a degree Fahrenheit. The innovative
design allows for a quieter, more efficient, and highly controllable unit,
enhancing a system’s performance and providing a quality product for
contractors and end-users alike.
"Extract from Copeland advertisement"
My opinion to what I can understand here manufacture came up with excellent
control of compressor pumping capacity, however they are neglecting to tell
you
that by reducing pumping capacity it also reducing compressors efficiency
Air Condition utilize this compressor at 100% capacity "example" it has 18
SEER
by reducing pumping capacity to 10% will become now 5% SEER
Pay attention motor is running at constant speed capacity is control by
closing
intake yes amperage drop some but far way from staying efficient to maintain
18 SEER
Unless you can cut power input, power consumption all this hypo about multi
and
variable speeds is in plain language lots of crap unless you are looking
specifically for comfort and money is no object.
Tony
www.cas-environ.com
show/hide quoted text
> (Does anyone make a residential variable speed compressor in the 4 tonn
> range)
> (Not 2-speed or multi-compressor, true multi-speed like some of the
> ductless, or commercial)
> How does the expansion valve deal with variable liquid flow rates? I
> would thing that at one flow you would get good expansion, but at too
> higher or lower you might have problems. How do the commercial units deal
> with the change if flow rates through the expansion valves, as I thought
> the expansion valves were tied to the flow, which would be tied to the
> compressor....
> I know that several manufactures make a big deal about their expansion
> "metering" values and was wondering how they fit into the grand scheme of
> the system.
> Bob
>
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Posted by gerry on May 31, 2007, 6:38 pm
[original post is likely clipped to save bandwidth]
On Thu, 31 May 2007 12:57:57 -0400, "Bob Sisson"
show/hide quoted text
>This is an extension of my question a while back out variable speed
>compressors.
>(Does anyone make a residential variable speed compressor in the 4 tonn
>range)
>(Not 2-speed or multi-compressor, true multi-speed like some of the
>ductless, or commercial)
>How does the expansion valve deal with variable liquid flow rates?
A better question is "how does the compressor supply a variable amount
of liquefied refrigerant as required by the system"
gerry
--
Personal home page - http://gogood.com
gerry misspelled in my email address to confuse robots
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Posted by Jake on May 31, 2007, 7:03 pm
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> A better question is "how does the compressor supply a variable amount
> of liquefied refrigerant as required by the system"
>
> gerry
>
Gerry,
A Digital Scroll is not the best design... in my opinion. It has a
solenoid valve that displaces the scroll (screw) enough that pumping
capacity is reduced to 10 percent. It is NOT linear-modulated... you
either get 100 percent or 10 percent... and nowhere in between. It's
also a mechanical operation, and I'd rather rely on electronics these days.
Copeland claims the energy savings are at least 20 percent. Frankly, I
don't buy that. The motor is energized and running constantly.. while
the pump starts working and stops working on demand... something like a
clutch on a vehicle.
I realize a lot of field techs have trouble with electronics, and
solenoids are a lot simpler to diagnose than a VFD that takes analog
inputs from microprocessor-processed data. However, I'm a big believer
in VFD's because I seem them save huge amounts of money with fans and
pumps using them... as well as screw air compressors. Fifty percent is
not unusual.
Tony's claim that a VFD system only helps comfort is baloney. A properly
designed and setup system is not ON/OFF... but usually variable from
40-100 percent capacity. It's true there is some loss of efficiency by
the drive itself... but not much... for good drives less than 2 percent.
A VFD system might be more expensive... but it is worth it. We have
several RTU's running VF coupled to our own SCADA system and the power
cost is about 40 percent less than it would be with a traditional setup.
Jake
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> Do NOT listen to Lloyd. No matter what he thinks........
> Expansion valves do NOT TALK!
> Bubba :-)
WAIT a minute, Bubba! Even you have heard one SING once in a while! <G>