Danfoss Superheat Controller, type EKD 316,084B8040 introduction

EKD 316 is a superheat controller for the stepper motor valve that can be used where there are requirements for accurate control of superheat in connection with refrigeration.The controller and valve can be used where

there are requirements for accurate control of superheat in connection with refrigeration.

Applications:

ƒ Processing plant (water chillers)

ƒ Cold store (air coolers)

ƒ A/C plant

ƒ Heat pumps

ƒ Air conditioning

Danfoss Superheat Controller, type EKD 316,084B8040 Advantages

The superheat is regulated to the lowest possible value.

ƒThe evaporator is charged optimally – even when there are great variations of load and suction pressure.

ƒEnergy savings – the adaptive regulation of the refrigerant injection ensures optimum utilisation of the evaporator and thus a high suction pressure.

Danfoss Superheat Controller, type EKD 316,084B8040 Main features

ƒ Regulation of superheat

ƒ MOP function

ƒ ON/OFF input for start/stop of regulation

ƒ Relay output to alarm

ƒ MOD bus communication

ƒ Safety features and

ƒ Alarm indications

Danfoss Superheat Controller, type EKD 316,084B8040 Function overview

Minimum Stable Superheat (MSS)

The controller will search for the minimum stable superheat

between an upper and lower boundry. If the superheat has been

stable for a period, the superheat reference is decreased. If the

superheat becomes unstable, the reference is raised again. This

process continues as long as the superheat is within the bounds

set by the user. The purpose of this is to search for the lowest

possible superheat that can be obtained while still maintaining a

stable system. The superheat reference can also be fixed, in which

case this function is disabled.

Maximum Operating Pressure (MOP)

In order to reduce the strain of the compressor, a maximum

operating pressure can be set. If the pressure comes above this

limit, the controller will control the valve to provide a lower

pressure instead of a low superheat. The limit for this function

is usually a fixed pressure, but it is possible to offset the limit

temporarily.

Stand-alone function

EKD 316 is designed to operate in conjunction with a system

master controller, which will control the EKD 316 via MODBUS or

analog signal. It is however possible to use it in a standalone mode

using one temperature and one pressure transducer.

Manual Control as a valve driver

The valve can be controlled manually by setting the desired

operating degree using MODBUS. Alternatively, the controller may

also be started and stopped externally using the analog signal 4 to

20 mA/0 to 10 V d.c., /1 to 5 V d.c.

Forced opening during startup

In some applications it is necessary to open the valve quickly when

the compressor turns on to prevent suction pressure becoming

too low. This is ensured by setting a fixed opening degree and

a startup time for the controller. Note that this will give a fixed

opening degree for the duration of the start time, regardless of the

superheat value.

Relay

The relay for the alarm function is an alternating relay. In the event

of an alarm, the relay will close, which may, for instance, be used

for an alarm buzzer.