Danfoss AK-PC 531B User guide

Design guide

Capacity controller

AK-PC 531B

ADAP-KOOL® Refrigeration control systems

Introduction

Application

The controller is used for capacity regulation of compressors and / or condensers in small refrigerating systems. This controller can regulate up to ten compressors. The condenser capacity is step regulated via the remaining available digital outputs and external relay module or variable speed regulated via a frequency converter.

Advantages

• Patented neutral zone regulation

• Sequential or cyclic operation

• Possibility of suction pressure optimisation via the data communication

• Load shedding function

Regulation

Regulation is based on signals from one pressure transmitter for the compressor regulation and one pressure transmitter for the condenser regulation plus one temperature sensor for the air temperature before the condenser.

Functions

• Relays for capacity regulation

• Voltage output for capacity regulation

• Status inputs. An interrupted signal indicates that the safety circuit has been activated and the respective circuit stopped

• Contact inputs for indication of alarms

• Contact inputs for displacement of references or for indication of alarms

• Alarm relay

• External start/stop of regulation

• Possibility of data communication

Operation

All operation takes place either via data communication or via connection of a display type EKA 164. The display can be disconnected after the installation.

2 Manual RS8HG102 © Danfoss 11-2015 AK-PC 531B

Function

Capacity regulation

The cut-in capacity is controlled by signals from the connected pressure transmitter and the set reference. Outside the reference a neutral zone is set where the capacity will neither be cut in nor out. Outside the neutral zone (in the hatched areas named +zone and -zone) the capacity will be cut in or out if the regulation registers a change of pressure “away” from the neutral zone. Cut in and cut out will take place with the set time delays. If the pressure however “approaches” the neutral zone, the controller will make no changes of the cut-in capacity. If regulation takes place outside the hatched area (named ++zone and --zone), changes of the cut-in capacity will occur somewhat faster than if it were in the hatched area. Cut in of steps can be dened for either sequential or cyclic operation.

Sequential (rst in - last out) The relays are here cut in in sequence – rst relay number 1, then 2, etc. Cutout takes place in the opposite sequence, i.e. the last cut-in relay will be cut out rst.

Cyclic (rst in - rst out) The relays are coupled here so that the operating time of the individual relays will become equalised. At each cutin the regulation scans the individual relays’ timer, cutting in the relay with least time on it. At each cutout a similar thing happens. Here the relay is cut out that has most hours on the timer.

Rx = random relay h = number of hours

AK-PC 531B Manual RS8HG102 © Danfoss 11-2015 3

Suvey of functions

Function Para-

meter

Normal display

If the two displays are mounted: P0 will be shown on EKA 165 / EKA 164 (the one with buttons) Pc will be shown on EKA 163

Compressor regulation reference Compressor control

P0 setpoint

Regulation is based on the set value plus an oset, if applicable. An oset can be created from night setback r13 and/or from a master gateway’s override function.

Oset

The set reference may be displaced with a xed value when a signal is received at the DI4 input or from the function "Night setback" (r27). (Cf. also Denition of DI4 input).

Night setback OFF: No change of the reference ON: Oset value forms part of the reference

Reference

The regulation reference is shown here

Set point limitation

With these settings the setpoint can only be set between the two values. (This also apply if regulation with "P0-optimisation function".)

Max. permissible setpoint value. r25 P0RefMax b

Min. permissible setpoint value. r26 P0RefMin b

Neutral zone

There is a neutral zone around the reference. See also page 3.

Correction of pressure measurement

An oset adjustment of the registered pressure can be made.

Unit

Here you can select whether thedisplay is to indicate pressure in bar or in Psig. And temperatures in °C or °F.

0: Will give bar and °C. 1: Will give Psig and °F.

Start/stop of refrigeration

With this setting the refrigeration can be started and stopped. Start/stop of refrigeration may also be performed with an external contact function connected to the input named “ON input”.

Condenser regulation reference Condenser control Pc setpoint

Regulation is based on the set value plus an oset, if applicable. An oset can be created via the “r34” function and/or from a master gateway’s override function.

Oset

The set reference may be displaced with a xed value when a signal is received at the DI5 input. (Cf. also Denition of DI5 input).

Pc reference variation 1: No change of the reference. Regulation based on set setpoint. 2: Outdoor temperature forms part of the reference. The outdoor temperature

is measured with Sc3. When the outdoor temperature drops one degree, the reference is lowered one degree. Setting 1 and 2 operate with a PI regulation. If the system is unstable and the PI regulation not satisfactory the I element may be left out, so there will be P regulation only.

3: As 1, but with P regulation 4: As 2, but with P regulation

The regulation reference is shown here. r29 Cond ref. b

The mean temperature dierence across the condenser at maximum load (dim tm K) r35 Dim.Tm K

The mean temperature dierence across the condenser at the lowest relevant compressor capacity (min tm K)

Set point limitation

With these settings the setpoint can only be set between the two values.

Max. permissible setpoint value. r30 PcRefMax b Min. permissible setpoint value. r31 PcRefMin b

Parameter by operation via data communication

P0 b (bar) Pc b (bar)

r23 Set Point b

r13 Night oset

r27 NightSetBack

r24 Comp ref. b

r01 Neutral zone

r04 AdjustSensor

r05 (In AKM only bar or °C is used,

whatever the setting)

r12 Main Switch

r28 Set Point b

r34 Press.oset

r33 Pc mode

r56 Min tm K

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Correction of pressure measurement

An oset adjustment of the registered pressure can be made.

Compressor capacity Compressor pack cong.

Running time

To prevent frequent start/stop, values have to be set for how the relays are to cut in and out.

Min. ON time for relays. (The time is not used if the relay cuts an unloader in or out).

Min. time period between cutin of same relay. c07 MinRecyTime

Setting for neutral zone regulation

Regulation band over the neutral zonen c10 + Zone b

Time delay between step cut-ins in the regulation band over the neutral zone c11 + Zone m

Time delay between step cut-ins in the regulation band over the "+Zone band". c12 + + Zone m

Regulation band under the neutral zone c13 - Zone b

Time delay between step cut-outs in the regulation band under the neutral zone c14 - Zone m

Time delay between step cut-outs in the regulation band under the "-Zone band" c15 - - Zone m

Compressor conguration

Here you set the combination of number of compressors and any unloaders.

1 = One compressor, 2 = two compressors, 3 = three, 4 = four....10 = ten.

See page 9. Selection of coupling mode (See also the overview page 9)

1. Sequential: First relay 1 cuts in, then relay 2, etc. Cutout takes place in the opposite sequence. (”First in, last out”).

2. Cyclic: An automatic operating time equalisation is arranged here, so that all steps with motor connection will have the same operating time

r32 AdjustSensor

c01 Min.ON time

c16 Compr mode

c08 Step mode

Denition of condenser and number of fans

Here you set the number of fan steps with which regulation has to be carried out (but max. eight). 1-8: All fans are cut in and out with relays. The rst vacant relay number is assigned to fan 1, the next to number 2, etc. Steps after DO10 must be executed through connection of a relay module type EKC 331 to the analog output. Cf. drawing on page 9.

9: All fans are controlled via the analog output and a frequency converter. 10: Not used 11-18: Total number of fan relays which are to be connected with alternating start-up.

Read temperature at sensor Sc3 u44 Sc3 temp Read temperature at sensor Sc4 (sensor is only used for monitoring) u45 Sc4 temp

Read temperature at sensor "Saux" u03 Saux temp Status on DI3 input u87 DI 3 status Status on DI4 input u88 DI 4 status Status on DI5 input u89 DI 5 status

Regulation parameters for the condenser regulation P: Amplication factor Xp (P = 100/Xp)

If the Xp value is increased, the regulation becomes steadier

I: Integration time Tn

If the Tn value is increased, the regulation becomes steadier Cutin condenser capacity with manual control. See also “n53” n52 FanManCap% Manual control of condenser capacity (when ON, the value in “n52” will be used) n53 FanManCap

c29 No. of Fans

- - - - Comp. Cap % Read cut-in compressor capacity

- - - - Cond. Cap % Read cut-in condenser capacity

n04 Xp b

n05 Tn s

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