ice block built up

[Kevin Yeo]

Hi all,

Good day. For supermarket refrigeration with 60% cold room and 40% display case for Medium Temp system. If compressor rack is set at -15 deg C SST and no suction pressure regulator is installed for cold room suction line, would it cause ice block built up only at the bottom of cold room evaporator coil? However, at the same time, this system also has its oil overcharged. Any opinion?

Which is the cause for ice block built up. Defrost system is ok

TQ

Rgds
Kevin

[littleyapper]

what temp are the rooms and cabinets set for ...-15 deg c evap seems a bit low to me .

[Eeram]

Why -15 deg. C suction? What type of controls are used? Where is the sensor/bulb location of thermostat/controller? Is there a solenoid valve? What is ok for defrost? What is the coil superheat? Why is the oil overcharged?

We need information!

[chillin out]

Is the system hot gas defrost?

I take it the drain pan is not blocked up?

Chillin

[Kevin Yeo]

Dear all,

I'm sorry for not providing sufficient information..my apologies...

- Room Temp Setpoint : 0 deg C ( 25 kW )
- Multideck Temp Setpoint : -2 deg C ( 25 kW)
- Danfoss EKC 202C thermostat for evaporators, EKC531 for compressor manager (3 compressors). Input to EKC531 is pressure tranducer
- 2 temp sensors, 1 at return air, 1 at evap coil
- Each evaporator is fitted with Solenoid valve individually
- Evaporators superheat are not measured, TXV sensing bulb located at 4 0'clock position, TXV equilizer located after sensing bulb. We hv only checked visibly that no liquid flooding back
- Off cycle defrost is used for all showcase and cabinet

Maybe I should put my question more accurately. Cold rooms evaporators are selected using 7K TD. Therefore, required evaporating temperature for the rooms are -7 deg C. However, since suction pressure regulator is not fitted and main line SST is set at -15 deg C, the delta P across TXV (mech type) is higher. Would it cause the rooms to ice up faster and what is the mechanism that cause icing rapidly?

TQVM
Kevin

[RANGER1]

Its colder so will attract more moisture from your humid weather .
Defrost at 0 deg C would have to be heaters or hot gas .

[Eeram]

You still need to know the superheat on the coldroom evaporator coil that keeps on icing at the bottom part. Knowing that, you should be able to determine if the expansion valve is correctly set or the valve strainer is blocked. Check for drain pan blockage as well. Move the EKC202 sensor to the air off side of the evaporator to read and measure true temperature. +2 deg. C on air on could result in -5 deg. C at air off, which could result in icing up of the coil and with no electrical defrost, it could ice up the coil. Where is the defost probe (sensor) mounted on the evaporator coils?

With the multi deck running at -2 deg. C, which is obviously the coldest cabinet on the system, I would change the suction setpoint (r23) on the EKC531 controller to -10 deg. C and saving unnecessary consumption. Also, a cabinet running at this low temperature, needs some form of defrost, other than off time.

What is the neutral zone on the EKC531 set to? What is the + and - Regulation parameter setting for the zones?

Sorry for asking so many questions! I can't see the system.