Specifications

ManualsBrandsCarrier ManualsAir Compressor19XRV

the HOT GAS BYPASS/SURGE PREVENTION is off, the

point must pass through the deadband region to the line deter-

mined by the configured values before the HOT GAS BY-

PASS/SURGE PREVENTION will be turned on. As the point

moves from the region where the HOT GAS BYPASS/

SURGE PREVENTION is on, the point must pass through the

deadband region before the HOT GAS BYPASS/SURGE

PREVENTION is turned off. Information on modifying the de-

fault set points of the minimum and full load points may be

found in the Input Service Configurations section, page 55.

The state of the surge/hot gas bypass algorithm on the

HEAT_EX DISPLAY SCREEN (Surge/HGBP Active?).

Corrective action can be taken by making one of 2 choices.

If a hot gas bypass line is present and the hot gas option is se-

lected on the OPTIONS table (SURGE LIMIT/HGBP OPTION

is set to 1), the hot gas bypass valve can be energized.

If the hot gas bypass option is not selected (SURGE LIMIT/

HGBP OPTION is set to 0), prevent the guide vane opening

from increasing. See Table 7, Capacity Overrides. Both of

these corrective actions try to reduce the lift experienced by the

compressor and help prevent a surge condition.

Hot Gas Bypass (Optional) Algorithm — If a

hot gas bypass solenoid valve is present and the HGBP OP-

TION in the OPTIONS table is set to 1 or 2, this operator con-

figurable feature can determine if load conditions are too low

for the compressor and corrective action can be taken.

HGBP OPTION = 0 — The HGBP algorithm is disabled.

HGBP OPTION = 1 (Constant Flow Units with VFD

Option Disabled) — The algorithm determines if corrective

action is necessary by checking the chiller operating point

against an operator configured threshold. The threshold is cal-

culated from a combination of the difference between ENTER-

ING CHILLED WATER and LEAVING CHILLED WATER

and the difference between CONDENSER PRESSURE and

EVAPORATOR PRESSURE.

The operator configured data points in version 8 software

and prior software versions are the MIN LOAD POINT (T1/

P1), the LOW LOAD POINT (T2/P2), the MID LOAD

POINT (T3/P3) and the FULL LOAD POINT (T4/P4). These

points have default settings defined in the OPTIONS screen

and in Table 3. The Default settings use one set of values for

the low, mid, and full load points. These surge characteristics

are factory set based on the original selection, with the values

printed on a label fixed to the bottom of interior face of the con-

trol panel. A line is drawn between these points as shown in

Fig. 25. Sample points for a four point line are shown.

Whenever the ACTIVE DELTA T (actual temperature dif-

ference between the LEAVING CHILLED WATER and EN-

TERING CHILLED WATER) is on the left side of the line plot-

ted in Fig. 25, the algorithm will energize the hot gas bypass

valve to falsely load the compressor. If the ACTIVE DELTA T

falls to the right side of the line plotted in Fig 25 by more than

the HGBP DEADBAND, the hot gas bypass valve is deener-

gized. The HGBP valve is also deenergized if the ACTIVE

DELTA P (actual difference between CONDENSER PRES-

SURE and EVAPORATOR PRESSURE) falls below HGBP

DELTA P1.

If the chiller is used for other than its original design condi-

tions, instructions to configure the MIN LOAD POINT (T1/P1)

and FULL LOAD POINT (T4/P4) are on page 73. Use the T4

value for T2 and T3 also. Use the P4 value for P2 and P3 also.

HGBP OPTION = 1 (Constant Flow Units with VFD

Option Enabled) — The HGBP is only energized if a SURGE

PROTECTION COUNT is registered, the ACTIVE DELTA T

falls below the SURGE/HGBP DELTA T or the VFD LOAD

FA C T O R approaches 1.0 and it is not possible to increase VFD

speed. The VFD speed cannot increase when the VFD TAR-

GET SPEED is equal to VFD MAXIMUM SPEED or if the

VFD TARGET SPEED is FORCED to a fixed value.

HGBP OPTION = 1 (Variable Primary Flow Units with

VFD Option Disabled) — The algorithm determines if cor-

rective action is necessary by checking the chiller operating

point against an operator configured threshold. The threshold is

calculated from a combination of GUIDE VANE POSITION

and the difference between CONDENSER PRESSURE and

EVAPORATOR PRESSURE. The operator configured data

points are the MINIMUM and MAXIMUM SATURATED

TEMPERATURE DIFFERENCE (Surge/HGP Delta Tsmin

and Surge/HGBP DeltaTsmax), the MAXIMUM AND MINI-

MUM GUIDE VANE POSITIONS (Surge/HGBP IGVmax

and Surge/HGBP IGVmin) printed on a label fixed to the bot-

tom of interior face of the control panel. A line is calculated be-

tween these points.

Whe

never the ACTUAL GUIDE VANE POSITION is on the

left side of the plotted line, the algorithm will energize the hot

gas bypass valve to falsely load the compressor. If the ACTU-

AL GUIDE VANE POSITION falls to the right side of the plot-

ted line by more than the SURGE/HGBP DEADBAND, the hot

gas bypass valve is deenergized.

If the chiller is used for other than its original design condi-

tions, instructions to adjust the Surge / Hot Gas Bypass config-

urations are found on page 80.

HGBP OPTION = 1 (Variable Primary Flow Units with

VFD Option Enabled) — The HGBP is only energized if a

SURGE PROTECTION COUNT is registered, the ACTIVE

DELTA T falls below the SURGE/HGBP DELTA T or the VFD

LOAD FACTOR approaches 1.0 and it is not possible to in-

crease VFD speed. The VFD speed cannot increase when the

VFD TARGET SPEED is equal to VFD MAXIMUM SPEED or

if the VFD TARGET SPEED is FORCED to a fixed value.

HGBP OPTION = 2 (Constant Flow and Variable Primary

Flow Units) — This option energizes the HOT GAS BYPASS

RELAY solely based on the ACTIVE DELTA T (actual temper-

ature difference between the LEAVING CHILLED WATER and

ENTERING CHILLED WATER). Evaluation of the ACTIVE

DELTA T begins at the completion of ramp loading. The hot

gas bypass valve is energized if the ACTIVE DELTA T is less

than the HGBP ON DELTA T. The hot gas bypass relay will be

turned off when the ACTIVE DELTA T is greater than or equal

HGBP/SURGE PREVENTION ON

HGBP/SURGE PREVENTION OFF

(10.3, 91)

(7.9, 76.4)

(2.6, 64.4)

(0.9, 41.3)

100

HGBP

DEADBAND

Sample Points are not defaults

0 2 4 6 8 10 12

T (F)

P (psid)

LEGEND

P = (Condenser Pressure) – (Cooler Pressure)

T = (ECW) – (LCW)

Fig. 25 — 19XR Surge Prevention/Hot Gas Bypass

Option 1 (Constant Flow with VFD Option

Disabled)

ECW — Entering Chilled Water

HGBP — Hot Gas Bypass

LCW — Leaving Chilled Water

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