Controls, Start-Up, Operation, Service and ... - Climayoreo
Controls, Start-Up, Operation, Service and ... - Climayoreo
Controls, Start-Up, Operation, Service and ... - Climayoreo
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NOTE: “Error” is clamped between –10 <strong>and</strong> +50 <strong>and</strong> “Error<br />
rate” is clamped between –5 <strong>and</strong> +5.<br />
This “SUM” will be compared against the “Z” calculations<br />
in determining whether cooling stages should be added or<br />
subtracted.<br />
Z Calculation — For the “Z” calculation, the control attempts<br />
to determine the entering <strong>and</strong> the leaving-air temperature of the<br />
evaporator coil <strong>and</strong> based upon the difference between the two<br />
during mechanical cooling, determines whether to add or<br />
subtract a stage of cooling. This is the adaptive element.<br />
The entering-air temperature is referred to as MAT<br />
(mixed-air temperature) <strong>and</strong> the leaving-air temperature of the<br />
evaporator coil is referred to as EDT (evaporator discharge<br />
temperature). They are found at the local display under the<br />
TemperaturesCTRL sub-menu.<br />
The main elements to be calculated <strong>and</strong> used in the calculation<br />
of SumZ are:<br />
1) the rise per percent capacity (R.PCT)<br />
2) the amount of expected rise for the next cooling stage<br />
addition<br />
3) the amount of expected rise for the next cooling stage<br />
subtraction<br />
The calculation of “Z” requires two variables, Z.PLU used<br />
when adding a stage <strong>and</strong> Z.MIN used when subtracting a stage.<br />
They are calculated with the following formulas:<br />
Z.PLU = Z.GN * (10 + (4*(–ADD.R))) * 0.6<br />
Z.MIN = Z.GN * (–10 + (4*(–SUB.R))) * 0.6<br />
Where:<br />
Z.GN = configuration used to modify the threshold levels used<br />
for staging (ConfigurationCOOLZ.GN)<br />
ADD.R = R.PCT * (C.CAP – capacity after adding a cooling<br />
stage)<br />
SUB.R = R.PCT * (C.CAP – capacity after subtracting a cooling<br />
stage)<br />
Both of these terms, Z.PLU <strong>and</strong> Z.MIN, represent a threshold<br />
both positive <strong>and</strong> negative upon which the “SUM” calculation<br />
must build up to in order to cause the compressor to stage<br />
up or down.<br />
Comparing SUM <strong>and</strong> Z — The “SUM” calculation is compared<br />
against Z.PLU <strong>and</strong> Z.MIN.<br />
• If “SUM” rises above Z.PLU, a cooling stage is added.<br />
• If “SUM” falls below Z.MIN, a cooling stage is subtracted.<br />
There is a variable called SMZ which is described in the<br />
reference section <strong>and</strong> which can simplify the task of watching<br />
the dem<strong>and</strong> build up or down over time. It is calculated as<br />
follows:<br />
If SUM is positive: SMZ = 100*(SUM/Z.PLU)<br />
If SUM is negative: SMZ = 100*(SUM/Z.MIN)<br />
Mixed Air Temperature Calculation (MAT) — The mixedair<br />
temperature is calculated <strong>and</strong> is a function of the economizer<br />
position. Additionally there are some calculations in the control<br />
which can zero in over time on the relationship of return<br />
<strong>and</strong> outside air as a function of economizer position. There are<br />
two configurations which relate to the calculation of “MAT”.<br />
These configurations can be located at the local display under<br />
ConfigurationUNIT.<br />
ITEM EXPANSION RANGE<br />
CCN<br />
POINT<br />
DEFAULTS<br />
UNIT UNIT CONFIGURATION<br />
MAT.S MAT Calc Config 0 - 2 MAT_SEL 1<br />
MAT.R Reset MAT Table<br />
Entries?<br />
Yes/No MATRESET No<br />
52<br />
MAT Calc Config (MAT.S) — This configuration gives the<br />
user three options in the processing of the mixed-air temperature<br />
(MAT) calculation:<br />
• MAT.S = 0<br />
There will be no MAT calculation.<br />
• MAT.S = 1<br />
The control will attempt to learn MAT over time. Any time<br />
the system is in a vent mode <strong>and</strong> the economizer stays at a<br />
particular position for long enough, MAT = EDT. Using<br />
this, the control has an internal table whereby it can more<br />
closely determine the true MAT value.<br />
• MAT.S = 2<br />
The control will stop learning <strong>and</strong> use whatever the control<br />
has already learned. Using this setting infers that the control<br />
has spent some time set to MAT.S = 1.<br />
First set MAT.S = 1. Then go into the <strong>Service</strong> Test mode,<br />
turn on the fan <strong>and</strong> open the economizer to a static position for<br />
5 minutes. Move to several positions (20%,40%,60%,80%). It<br />
is important that the difference between return <strong>and</strong> outside<br />
temperature be greater than 5 degrees. (The greater the delta,<br />
the better). When done, set MAT.S = 2 <strong>and</strong> the system has been<br />
commissioned.<br />
Reset MAT Table Entries? (MAT.R) — This configuration<br />
allows the user to reset the internally stored MAT learned<br />
configuration data back to the default values. The defaults are<br />
set to a linear relationship between the economizer damper<br />
position <strong>and</strong> OAT <strong>and</strong> RAT in the calculation of MAT.<br />
SumZ Overrides — There are a number of overrides to the<br />
SumZ algorithm which may add or subtract stages of cooling.<br />
• High Temp Cap Override (H.TMP)<br />
• Low Temp Cap Override (L.TMP)<br />
• Pull Down Cap Override (PULL)<br />
• Slow Change Cap Override (SLOW)<br />
Economizer Trim Override — The unit may drop stages of<br />
cooling when the economizer is performing free cooling <strong>and</strong><br />
the configuration ConfigurationECONE.TRM is set to<br />
Yes. The economizer controls to the same supply air set point<br />
as mechanical cooling does for SumZ when E.TRM = Yes.<br />
This allows for much tighter temperature control as well as cutting<br />
down on the cycling of compressors.<br />
For a long cooling session where the outside-air temperature<br />
may drop over time, there may be a point at which the<br />
economizer has closed down far enough were the unit could<br />
remove a cooling stage <strong>and</strong> open up the economizer further to<br />
make up the difference.<br />
Mechanical Cooling Lockout (ConfigurationCOOL<br />
MC.LO) — This configuration allows a configurable outsideair<br />
temperature set point below which mechanical cooling will<br />
be completely locked out.<br />
DEMAND LIMIT CONTROL — Dem<strong>and</strong> Limit Control<br />
may override the cooling algorithm <strong>and</strong> clamp or shed<br />
cooling capacity during run time. The term Dem<strong>and</strong> Limit<br />
Control refers to the restriction of the machine capacity<br />
to control the amount of power that a machine will use.<br />
Dem<strong>and</strong> limit control is intended to interface with an external<br />
Loadshed Device either through CCN communications, external<br />
switches, or 4 to 20 mA input.<br />
The control has the capability of loadshedding <strong>and</strong> limiting<br />
in 3 ways:<br />
• Two discrete inputs tied to configurable dem<strong>and</strong> limit set<br />
point percentages.<br />
• An external 4 to 20 mA input that can reset capacity back<br />
linearly to a set point percentage.<br />
• CCN loadshed functionality.<br />
NOTE: It is also possible to force the dem<strong>and</strong> limit variable<br />
(Run StatusCOOLDEM.L).