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Posted by Marc O'Brien on August 1, 2007, 9:54 pm
We factory acceptance test (FAT) water chillers typically under
maximum load conditions.
What is a maximum load condition?
A maximum load condition is primarily ambient temperature focused. Not
chilled water temperature focused. It is the condition whereby while
the chilled water temperature's are at the design full load return and
supply points the coincident ambient temperature is at the maximum
specified for a given altitude.
But water chillers fail mostly under lowest load conditions.
What is a lowest load condition?
It is precisely the reciprocal!
What sayeth the PJM's and the other great minds of our industry?
Of course, given the above described limitations that a typical FAT is
subjected to, the imagination, of a technical nature, regarding
SSAT's, is more about extrapolation though mostly about seasonal
timing.
Marc O'Brien
Technical Director
Fridgetech.Com Ltd
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Posted by on August 1, 2007, 10:26 pm
On Wed, 01 Aug 2007 18:54:11 -0700, Marc O'Brien
>We factory acceptance test (FAT) water chillers typically under
>maximum load conditions.
>
>What is a maximum load condition?
>
>A maximum load condition is primarily ambient temperature focused. Not
>chilled water temperature focused.
Bzzt, partially. Efficiency changes with OD ambient, as does
( of course ) load via wall / roof / windows, but in any application
where it's a chiller, it's a commercial structure, and thus the
internal loads are a HUGE factor ( occupants, lights, other equipment
, etc ). IOW, given two days of equal outdoor conditions - one a
Friday ( fully occupied ) and the other a Sunday ( totally empty ),
the system loads are totally different ( under identical weather ).
And, of course, any system spends 95 % of its life at
part-load, so, IMO, 'acceptance testing' would have to include not
merely 'full up / full down', but the stretch in between ( proper
control, stability, no excessive hysterisis, oil return and pressure
at part-load, etc etc.
> It is the condition whereby while
>the chilled water temperature's are at the design full load return and
>supply points the coincident ambient temperature is at the maximum
>specified for a given altitude.
I thought you just said "Not chilled water temperature
focused." I must have been mistaken :-)
>But water chillers fail mostly under lowest load conditions.
You've seen research on that ? IMO, they are more likely to
break during TRANSITIONAL periods, such as ramping up in the morning,
down at night, etc. That's where things can get out of sync,
possibly ( let's say your ramp loop on the chiller is faster than the
ramp loop on the CHW pump ), as well as linkages getting exercised
etc.
>What is a lowest load condition?
>
>It is precisely the reciprocal!
Umm.... so ?
>
>What sayeth the PJM's and the other great minds of our industry?
Urpp ?
>Of course, given the above described limitations that a typical FAT is
>subjected to, the imagination, of a technical nature, regarding
>SSAT's, is more about extrapolation though mostly about seasonal
>timing.
Discovered a new lager, have we ? :-)
--
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Posted by daytona° on August 2, 2007, 6:54 am
What brought this on?
> We factory acceptance test (FAT) water chillers typically under
> maximum load conditions.
>
> What is a maximum load condition?
>
> A maximum load condition is primarily ambient temperature focused. Not
> chilled water temperature focused. It is the condition whereby while
> the chilled water temperature's are at the design full load return and
> supply points the coincident ambient temperature is at the maximum
> specified for a given altitude.
>
> But water chillers fail mostly under lowest load conditions.
>
> What is a lowest load condition?
>
> It is precisely the reciprocal!
>
> What sayeth the PJM's and the other great minds of our industry?
>
> Of course, given the above described limitations that a typical FAT is
> subjected to, the imagination, of a technical nature, regarding
> SSAT's, is more about extrapolation though mostly about seasonal
> timing.
>
> Marc O'Brien
> Technical Director
> Fridgetech.Com Ltd
>
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Posted by Tony on August 3, 2007, 4:43 pm
Mr. O'Brien I am not HVAC person nor do I have any degree
Are you asking why chillers fail mostly under lowest load conditions?
Need verification on this.
And What is a lowest load condition? well from my on experience
up to 200 HP reciprocal compressors, if system properly design
that should not be relevant, system/unit should be abele to operate
from no load to ?????? depend if same water/brine is use for heating.
And I am sorry to say but manufactures often enough are known to
cheat in design of systems, it is not always what they claim to be!
Tony
www.cas-environ.com
> We factory acceptance test (FAT) water chillers typically under
> maximum load conditions.
>
> What is a maximum load condition?
>
> A maximum load condition is primarily ambient temperature focused. Not
> chilled water temperature focused. It is the condition whereby while
> the chilled water temperature's are at the design full load return and
> supply points the coincident ambient temperature is at the maximum
> specified for a given altitude.
>
> But water chillers fail mostly under lowest load conditions.
>
> What is a lowest load condition?
>
> It is precisely the reciprocal!
>
> What sayeth the PJM's and the other great minds of our industry?
>
> Of course, given the above described limitations that a typical FAT is
> subjected to, the imagination, of a technical nature, regarding
> SSAT's, is more about extrapolation though mostly about seasonal
> timing.
>
> Marc O'Brien
> Technical Director
> Fridgetech.Com Ltd
>
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