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View Full Version : First time install of external VSD - Need some advice in how to connect components







The Red Krawler
10-09-2014, 04:01 AM
G'day,

This is our first install where we'd like to utilise an electronic TX valve, variable speed drive and water cooled compressor.

We bought the lot as a package from a local wholesaler and were assured it was compatible, but now their technical guy has disappeared on holidays and we're stuck trying to work out how things go together - and in my opinion it simply won't work as advertised.

The components are a Carel EVD Evolution (electronic TX valve), a Vacon VSD and a Bitzer compressor. The control is a Carel Mastercella.

In my mind, the electronic TX valve is stand alone, and is based purely on superheat. It doesn't connect to anything and will react purely on suction pressure (via a transducer) and temperature (via a sensor) to open and close the valve, regardless of room temperature or compressor operation.

The compressor is simply connected to the VSD output. No problem.

The MasterCella needs to turn the compressor on and off based on room temperature and defrost requirement. But the trick is... how do I make the VSD "work"?

I can easily connect the MasterCella to purely act as a "start" command to the VSD, but that will just make it a very expensive soft starter as without any speed instruction it will just go to maximum RPM. What I need is to send ramp up / ramp down commands based on load.

Should the electronic TX valve provide the ramp up/down commands to the VSD? There's a set of RX/TX/GND terminals that provide serial (RS485) connectivity, but what is it actually outputting? The manual shows it being connected to a Carel pCO control but we have a MasterCella. Can this go directly to the VSD and be programmed using some kind of standard, or is it Carel proprietory stuff?

The VSD has RS485 settings that allows protocols of "Modbus/RTU", "N2" and "BACnet MS/TP". What does Carel use?

Should there be another transducer in the suction side that controls the speed of the compressor / VSD output? The VSD seems to be able to accept input from 0..20mA or 0..10V as an analog input.

The MasterCella has a serial (RS485) connection, but it just says "To Supervisor" which I assume is a mimic panel of some kind for reading output, not accepting input.

I'd appreciate any help on this as I'm kind of lost here.

frank
10-09-2014, 04:40 AM
Maybe that the vsd is for controlling a pump on your water cooled condenser?
The vsd speed output is proportional to the 0-10v input and depending on the settings.

HVACRsaurus
10-09-2014, 08:31 AM
Hi Buddy,

I reckon you are pretty much on the money..

I'd think the EXV is stand alone, but may interlocked with the Carel mastercella - cooling output from carel to "enable" the EXV (and consequently stop EXV regulation during defrost / off cycle).

I would suggest that the VSD requires another pressure transmitter (sometimes transmitters can be "shared" but it's usually easier to just put another one on). Some VSD's may need a controller, but I think most modern units can scale the analog input (pressure in this case) and control / ramp according to setpoint.

As for run / stop command for VSD - perhaps via carel?

I wouldn't think that it is common to use the modbus / 485 comms in this application.

Perhaps Bitzer could help out with a few suggestions?

Glenn Moore
10-09-2014, 12:46 PM
Hi RK
Sounds like you have the makings of a good energy efficient system. I have designed many systems such as this when I was Tech manager for Danfoss. I have a little experience of integrating Carel and Danfoss controls but you are basically correct in your thinking of the set up of the system.
The Mastercella will simply give a volt free go signal to both the EVD controller and the VSD. The Mastercella is set up to control the system. When the controller calls for duty the EVD expansion valve is enabled along with the VSD. The EVD simply uses a temperature sensor and a pressure transducer to give superheat information to the EVD controller and drives the EEV to control the valves opening degree to control the superheat at the evaporator.
The VSD is set up to control the compressors speed ie MIN Hz and MAX Hz that the model of compressor can operate at, normally in the region of 35hz to 85Hz (Confirm with Bitzer.) Then a seperate pressure transducer connected to the suction line is then connected to the VSD . The Transducer type ie Volt or ma signal is connected directly to the VSD and the transducers range and signal type is entered into the VSD. A few other settings such as ramp up and down times are entered into the VSD along with the desired suction pressure set point which is the lowest evap temp/pressure to achieve cut out via the Mastercella
So the Mastercella starts both the EVD and the VSD . The VSD starts and ramps up to full speed depending on the suction pressure, and the EVD opens the valve to control the s/heat as the suction pressure drops the compressors speed starts to slow down as it approaches set point as the temperature in the room falls to set point the MAsercella stops the EVD and VSD ,Normally the VSD can operate a pump down via its settings .
The EVD superheat set point should be able to control at 4-6 K , I used to set the Danfoss controllers at 4k and they gave a very stable superheat/suction condition in most instances

good luck
Glenn

Grizzly
10-09-2014, 06:42 PM
Hi RK
Sounds like you have the makings of a good energy efficient system. I have designed many systems such as this when I was Tech manager for Danfoss. I have a little experience of integrating Carel and Danfoss controls but you are basically correct in your thinking of the set up of the system.
The Mastercella will simply give a volt free go signal to both the EVD controller and the VSD. The Mastercella is set up to control the system. When the controller calls for duty the EVD expansion valve is enabled along with the VSD. The EVD simply uses a temperature sensor and a pressure transducer to give superheat information to the EVD controller and drives the EEV to control the valves opening degree to control the superheat at the evaporator.
The VSD is set up to control the compressors speed ie MIN Hz and MAX Hz that the model of compressor can operate at, normally in the region of 35hz to 85Hz (Confirm with Bitzer.) Then a seperate pressure transducer connected to the suction line is then connected to the VSD . The Transducer type ie Volt or ma signal is connected directly to the VSD and the transducers range and signal type is entered into the VSD. A few other settings such as ramp up and down times are entered into the VSD along with the desired suction pressure set point which is the lowest evap temp/pressure to achieve cut out via the Mastercella
So the Mastercella starts both the EVD and the VSD . The VSD starts and ramps up to full speed depending on the suction pressure, and the EVD opens the valve to control the s/heat as the suction pressure drops the compressors speed starts to slow down as it approaches set point as the temperature in the room falls to set point the MAsercella stops the EVD and VSD ,Normally the VSD can operate a pump down via its settings .
The EVD superheat set point should be able to control at 4-6 K , I used to set the Danfoss controllers at 4k and they gave a very stable superheat/suction condition in most instances

good luck
Glenn

Hi Glenn
No-one told us that you had retired, no wonder that getting a straight technical answer is so difficult now.
You must be missed at Danfoss!
I did wonder at the recent posts you had been placing lately whether you were the one and only Glen more!
Welcome to the forum!
You will be a valuable member.
Grizzly

Glenn Moore
10-09-2014, 09:07 PM
Hi Grizzly
I still get calls from around the country and have set up a little company doing troubleshooting and training .The boys at Deano,s still call for advice so im still around .I have just finished an article on condensers and condenser control which I have presented at a couple of Fridge society do's.
So still keeping my hand in its difficult giving up an enjoyable industry and working with the great bunch of guys who keep our industry going
All the very best
Glenn

Brian_UK
10-09-2014, 09:16 PM
I would suggest that you carry spare EEV spares such as a stepper motor coil and the pressure/temperature sensor.

I maintain a four compressor chiller with Carel EEVs and do need regular replacement of the sensors plus a few coils. Good superheat control though.

The Red Krawler
10-09-2014, 11:28 PM
Thanks for the incredibly useful replies. Good to hear I was on the right track too... well, mostly :P I'm keen to get involved in more VSD stuff, but I'm basically starting from scratch. Our exposure thus far has been pretty limited.

The way I see it is the MasterCella will close a digital input on both the electronic TX valve and the VSD as a "go" signal when cooling is required, and the VSD speed will be controlled by a pressure transducer in the suction line.

Safety controls will operate as an alarm signal (another digital input on the VSD) to shut everything down.

I'll post an update once it's finished, might even throw in a picture or two if I don't balls it up too badly ;)

Glenn Moore
10-09-2014, 11:50 PM
Youve got it spot on. This is the future for all new fridge systems
My regards to Skippy

The Red Krawler
23-09-2014, 03:43 PM
Okay, so it turns out wiring up the VSD, electronic TX valve and MasterCella wasn't actually too bad although I did need some advice from the VSD supplier regarding a loop you have to add in to use the specific transducer we had. I even sorted out the programming on my own, including changing the scale and ramp profile and even managed to lock out some frequencies that were causing the oil seperator float to vibrate like crazy. I felt like Bill Gates tapping away and making it do cool things.

The hard part was actually turning the mechanical control circuit and alarms in to voltage-free electronic control alarm. There was bloody diodes and capacitors and random wires all over the place on the mechanical setup. Government installation originally, so everything was over the top. Anyway, it works now.

Before (not the exact unit, but it was practically identical to this): http://i.imgur.com/M81sEiS.jpg

Afer: http://i.imgur.com/eAW2dby.jpg

frank
23-09-2014, 07:23 PM
Well done that man...nice job

Glenn Moore
23-09-2014, 11:53 PM
Hi RK
Nice to hear and see good energy efficient plants being installed . I have many Fruit storage systems in Kent that use EEVs , Pack controllers, invertors etc which have reduced energy consumption on some systems by over 30% without any negative effect to the product. The Farmers actually demand this type of equipment now as it makes good economic sense
Keep up the good work Kr Glenn

Peter_1
24-09-2014, 06:59 AM
We do it exactly the same way but we use Invertek instead of Vacon VFD's.
Very nice job. One very small remark: don't insulate the suction accumulator. You need heat to evaporate the liquid in it.
Was this a R502 replacement? Those good oll' days

The Red Krawler
25-09-2014, 11:36 AM
One very small remark: don't insulate the suction accumulator. You need heat to evaporate the liquid in it.


It originally wasn't insulated, but there was enough condensation to leave water on the floor come Monday (after leaving it on test over the weekend - the job was finished Friday but the hire freezer was still there until Monday so we took the opportunity to let it run for ~72 hours before loading it up) that we ended up insulating it. That's why it looks a bit different to the rest of the insulation.




Was this a R502 replacement? Those good oll' days

Yes, it was on 502. We recently changed an evaporator on a coldroom unit in that same plant area and it was on R12 :-\

The Red Krawler
25-09-2014, 11:45 AM
reduced energy consumption on some systems by over 30%

I'd believe that, no problems at all. I never checked the current draw of the original unit before we started pulling it apart, but the original overload is set for ~20% higher than the maximum current of the current compressor, and we pull near half the compressors FLA in low load situations.

Thanks again for the replies to my questions. Getting this one done has given a lot of confidence for the next install so I can see it quickly becoming the norm rather than the exception.

Does anyone have a good source of 'best practice' guides for VSD sizing and installation, especially in regards to HVAC? I really want to learn more about it and get all the good oil on what works and what doesn't, and why things should be done a certain way over another.

Glenn Moore
26-09-2014, 07:04 PM
Hi RK
Go on the Danfoss website and join the Danfoss E Learning forum, it allows you to enter their training school in which you can take the many short training sessions . Most are on various refrigeration aspects, from basic valve operation to system design , co2 etc. There are also several sessions on Invertor drives ,what they can do how they work , how to set them up and the various benefits of fittings an invertor to a system, such as the energy savings, soft starter function, how to skip frequencies that make the compressor noisy, how to overide the invertor function and jump to a fixed frequency. Im sure you will find it extremely thought provoking
Best regards Glenn

Tycho
26-09-2014, 08:06 PM
G'day,

This is our first install where we'd like to utilise an electronic TX valve, variable speed drive and water cooled compressor.

We bought the lot as a package from a local wholesaler and were assured it was compatible, but now their technical guy has disappeared on holidays and we're stuck trying to work out how things go together - and in my opinion it simply won't work as advertised.

The components are a Carel EVD Evolution (electronic TX valve), a Vacon VSD and a Bitzer compressor. The control is a Carel Mastercella.

In my mind, the electronic TX valve is stand alone, and is based purely on superheat. It doesn't connect to anything and will react purely on suction pressure (via a transducer) and temperature (via a sensor) to open and close the valve, regardless of room temperature or compressor operation.

The compressor is simply connected to the VSD output. No problem.

The MasterCella needs to turn the compressor on and off based on room temperature and defrost requirement. But the trick is... how do I make the VSD "work"?

I can easily connect the MasterCella to purely act as a "start" command to the VSD, but that will just make it a very expensive soft starter as without any speed instruction it will just go to maximum RPM. What I need is to send ramp up / ramp down commands based on load.

Should the electronic TX valve provide the ramp up/down commands to the VSD? There's a set of RX/TX/GND terminals that provide serial (RS485) connectivity, but what is it actually outputting? The manual shows it being connected to a Carel pCO control but we have a MasterCella. Can this go directly to the VSD and be programmed using some kind of standard, or is it Carel proprietory stuff?

The VSD has RS485 settings that allows protocols of "Modbus/RTU", "N2" and "BACnet MS/TP". What does Carel use?

Should there be another transducer in the suction side that controls the speed of the compressor / VSD output? The VSD seems to be able to accept input from 0..20mA or 0..10V as an analog input.

The MasterCella has a serial (RS485) connection, but it just says "To Supervisor" which I assume is a mimic panel of some kind for reading output, not accepting input.

I'd appreciate any help on this as I'm kind of lost here.


All this is solved it seems, but I only saw it now, but from personal experience I want to add a few things and ask a few more questions to enlighten myself :)

I do have some questions about the regulation (no mean questions, purely out of curiosity).

I'd like to start off with "you should have gone with a Danfoss VFD" but that probably wasn't your choice :)
Danfoss VFD's are so user friendly that all they don't do is pat you on the back when you set them up correctly" :) if you have a problem, their user manual covers it all.
Vacon VFDs may be good, but their user manual leaves a lot to be desired, you need to be an electrical engineer to understand half of what is written :)

Anyways...

Glen Moore pretty much summed it up, I have no experience with the VFD working in tandem with the room and superheat controller.

Usually on older retrofitted systems with a danfoss VFD we set it up with a pressure sensor on the compressor suction and let the compressor work independent of the superheat and room temperature.
so the compressor works on a set minimum suction pressure, and when that is reached, the compressor stops no matter what the room temperature or superheat is.

However, we make our own PLC programs (yay for us :)) and we take into account the room temperature, the room setpoint, the superheat, the compressor speed and the compressor capacity, and we have sensors on all of these points, so for example is the setpoint in the room is -20C and the superheat on the EXV is 2C and the real temperature in the room is 15C and the suction pressure on the compressor is -30C
You will get a warning saying "room temperature high - superheat low - suction pressure low"
if you click on it it will give you "reasons" for this condition and points to check, and all our systems has a black box that is paired with another black box in our office, and as long as you have an internet connection, we can monitor or watch the system live :)

Pretty handy when they call from a ship in the middle of the north sea and have an issue, we just connect the box ad we can see whatever the on board technician can see live on our computer :) *brag brag brag* :D

Hi RK
Sounds like you have the makings of a good energy efficient system. I have designed many systems such as this when I was Tech manager for Danfoss. I have a little experience of integrating Carel and Danfoss controls but you are basically correct in your thinking of the set up of the system.
The Mastercella will simply give a volt free go signal to both the EVD controller and the VSD. The Mastercella is set up to control the system. When the controller calls for duty the EVD expansion valve is enabled along with the VSD. The EVD simply uses a temperature sensor and a pressure transducer to give superheat information to the EVD controller and drives the EEV to control the valves opening degree to control the superheat at the evaporator.
The VSD is set up to control the compressors speed ie MIN Hz and MAX Hz that the model of compressor can operate at, normally in the region of 35hz to 85Hz (Confirm with Bitzer.) Then a seperate pressure transducer connected to the suction line is then connected to the VSD . The Transducer type ie Volt or ma signal is connected directly to the VSD and the transducers range and signal type is entered into the VSD. A few other settings such as ramp up and down times are entered into the VSD along with the desired suction pressure set point which is the lowest evap temp/pressure to achieve cut out via the Mastercella
So the Mastercella starts both the EVD and the VSD . The VSD starts and ramps up to full speed depending on the suction pressure, and the EVD opens the valve to control the s/heat as the suction pressure drops the compressors speed starts to slow down as it approaches set point as the temperature in the room falls to set point the MAsercella stops the EVD and VSD ,Normally the VSD can operate a pump down via its settings .
The EVD superheat set point should be able to control at 4-6 K , I used to set the Danfoss controllers at 4k and they gave a very stable superheat/suction condition in most instances

good luck
Glenn

Don't believe I've come across you before Glenn, if I can call you that, I'm from Norway, and the company I work for deal in 99.99% danfoss VFD or FQD as I call them.. the service personnel in Norway seems to be technically knowledgeable, but lacking in the department of "practical application" of the FQD's.
Long story made short, I had a VFD where the amp reading would spike to three times the motor current limit, and the VFD wouldn't notice it fast enough, but our PLC registered it and decreased load on the slide valve on the compressor to protect the motor from overload.

I spent 3 weeks back and forth trying to dig my way into this and find the cause (tried the 4-20 mA output with the filter back and forth, if I sent speed out on that output it was dead stable, but with amps it would spike over 100%).
second time I was on board I was on the phone with the "superdooper" VFD guy in oslo after being on the phone with him for 45 minutes the only thing I came away with was "Don't ever stand in front of a VFD when you power it up".

So i brought my computer and connected it and logged 1 hour of running the compressor in the MCT10 software, I did a log of the compressor running with amps on the output and speed on the output.

with the speed output, it was a straight line for 30 minutes.

with amps as the output it was like a the heartbeat of a teenage girl at a jerry lee lewis concert

Danfoss never came out with a fix (since they had done nothing wrong ;)) but a service bulletin announcing a new firmware to be loaded into the VFD drive came, and for some strange reason, "problem solved" :)

Glenn Moore
26-09-2014, 10:20 PM
Hi Tycho
Your showing your age with Jerry Lee lewis, you should say Justin Bieber haha. Yes your right the new Danfoss refrigeration range of drives are so easy to set up for us fridges. I worked with Danfoss for 37years in a technical back up roll in the refrigeration dept, a great bunch of guys there but most have retired now.
But I know there have been several software updates to over come site conditions and improve the safety of the drives and the latest is for controlling Permanent Magnet Motors (PMM's) like the Maneurop VZH scroll machines , nice machines that range from 25 to 100Hz absolutely magic.
Keep up the good work
Glenn