PDA

View Full Version : Floating condensation,evaporating temperature - some questions







xixxi
28-03-2016, 01:12 PM
Hi colleagues! I hope you well!

I need help in this question.
First of all, I have two shock freezing rooms. 4 evaporators were installed in each room. I want to use electronic expansion valves Carel and fan speed controller like FCS Carel.

As I know, for the correct operation of the EXV we should install suction pressure sensor and temperature sensors (one on an evaporator, and a temperature sensor in the chamber). We should have EVDtwin driver which will manage two expansion valves. It means, I need four EVDtwin for two cold rooms. Can I install only one pairs of temperature sensors in each cold room? Or I should use pair of temperature sensors for each EVD driver? Should I use other sensors?

Another question is what type of sensors I should use for fan speed controllers? As I know I need a sensors which should be installed after condenser, and one temperature sensor for testing free-air temperature. Should I use other sensors? Should I use additional controller like pRack or FCS will manage condensation without it?

Thank you!
Sorry for my English, it's foreign language for me and long time since I practiced in English.

Glenn Moore
29-03-2016, 10:19 PM
Hi
All of the 8 evaporators will need a sensor mounted on their outlet suction pipes, and a pressure transmitter per EVD controller mounted on the common suction pipe, so each evaporators expansion valve will have its own superheat reading from the pressure transmitter (saturated suction pressure/temperature ) and each evaporators suction outlet temperature (superheated suction pipe temperature ) .The evaporator sensors must be placed on the suction outlet pipes where the TEV bulb would normally be placed. Each evaporator will then be controlled individually with a stable superheat control.
On one of the EVD an extra sensor can be fitted for room temperature control in each room.
The Condenser Fan Speed Controller will need a pressure transmitter ,and a temperature sensor to measure the ambient temperature. The Speed controller will need to be set up to measure the discharge pressure and the ambient temperature . In the settings you should be able to set a differential between the ambient temperature and the discharge pressure/saturation temperature so as the ambient temperature floats so the discharge pressure will change automatically.
For your information Danfoss have an electronic expansion valve controller that can control 4 electronic valves from one module , plus evaporator fan control, defrost control ,liquid line solenoid control and room thermostat control . The model is an Danfoss AK CC 750 unit

xixxi
30-03-2016, 05:42 AM
Hi Glenn!
Thank you for answers.
I've got 3 condensers which are connected in parallel. Each condensers with 6 fans (550 mm, 220V). Can I mount 1 fan speed controller on 3 condensers or I should use 3 fan speed controllers?

Glenn Moore
30-03-2016, 10:54 PM
Hi xixxi
Its a bit unusual to have 3 condensers piped in parallel, as this can cause liquid hang ups in the condenser coils due to various pressure drops in each condenser. So the condensers need to have their outlets correctly piped , so that the liquid naturally exits each condenser.
Please confirm how the 6 fans on each condenser are mounted . Are they all in a line

as XXXXXX or as in pairs XXX
XXX

Glenn

Glenn Moore
10-04-2016, 11:28 PM
If the fans are mounted in 3 pairs, I would run the 2 fans nearest the header at full speed and the other 4 on the invertor. Each condenser is set up the same using one invertor for the 3 condensers, that way the condensers should balance out