View Full Version : compressor and room controllers

20-04-2016, 11:41 PM
Danfoss had a really nice thing going with one of their controllers called a "room controller" where it had a small screen where you could read the superheat across the evaporator, temperature of air in and temperature of the air out, pressure in bar and converted to temperature as well as real temperature and core temperature if you had a defrost sensor installed.
The whole thing was door mounted, which was nice, because it could be mounted in the door, so you or the customer could access it without opening the cabinet door.

it was all viewable on a 2 inch screen, with graphic showing the placement of the sensors, and it was so well done that you could just flick through the pages and and just like that, you had the health of that particular room/evaporator.
it was easy to understand for the customer if you were trying to get information over the phone.

I've been looking for pictures of this one, but I can only find pictures of the new ones.

The systems I have been on, this controller has been used to simply control the superheat across the evaporator, and monitor

this controller is now discontinued and has been replaced by a controller that looks like this:

it has to be mounted to a DIN rail inside the cabinet, it's impossible to explain to the customer how to access the information you need over the phone.
While it works as it should, it's utterly useless when something is not working.

So together with a friend of mine, I am working on a solution.

7" touch screen PLC
Base application is 1 compressor unit and freezing room, cold room and cool room.
you can choose PID regulator for all three rooms to maintain superheat, or on/off regulator for the solenid if a TX valve is used (regulates on room temperature)
If cold or cool room needs to cooling, freezing room will also run, unless on defrost, to give the compressor enough load to run.

on screen choice whether HP/LP is pressure switches or 0-10V/4-20mA sensors (HP switch required, if regulations in your country does not require a HP switch, put a jumper in)
same for Oil pressure, on screen selection if it's OP minus LP or OP minus HP or if a differential pressure switch is fitted.

for a basic system like this, the selling price would be around USD 2.500,-
that is for a complete control unit for the whole system, hang it on the wall and connect the wires.

compared to the danfoss EKC controllers, all the settings would be in plain text when you enter the setup menu instead of having to to parameter r12 to change something.
you can go to the settings menu, make changes to the superheat, then straight back to the overview to see the opening degree of the valve, instead of having to wait for the controller to timeout and go back to the main screen...
Not to talk about the EKC or AK-cc controllers where you will end up with callouses on your fingers while trying to keep an eye on all the different measurements... All that will be accessible on one page...

While it's not new technology.

With the selling price being $2.500, is this something that would appeal to anyone?
Having it all easily accessible on a 7" touch screen, compressor control and room control for 3 rooms in one unit (doesn't have to be freeze, cold and cool, from the screen it can be sat to whatever temperature you want :))

And by easily accessible, I mean that it has been designed so that a service person can throw a glance at the screen as he walks by, and have all the information he needs, instead of having to go through five different menus to get information :)

And we are of course accepting any input towards features that is wanted :)

Glenn Moore
21-04-2016, 12:35 AM
Hej Tycho
The controller your talking about is the Danfoss AKC72A Room Controller. I have several of the last batch of these controllers that Danfoss made in my garage.
I sold many of these controllers as you say they were a fantastic controller. I have a few working on coldrooms in St Thomas's Hospital in London.
The problem was that the AKC72A was overpriced as against a more basic but similar control called Coltrec that was on the market. The AKC 72A was superior in every way to the Coltrec but was nearly twice the price.
Danfoss have many controllers for cold room control such as the CC550 which in the UK is fitted to most of the larger supermarkets cases, on both R404A and Co2.
The AKC72A controlled all functions of a cold room or case, plus either TEV or electronic expansion valve. The AKC114A replaced it before that was then discontinued.
The CC550 controller does the same function as the 72A ie one coldroom or case.
The there is the latest animal called an AK CC 750 which can run from 1 to 4 evaporators with either TEVs ,AKV pulsed electronic expansion valves or the ETS Stepper valves. These controllers all talk LON or MODBUS and with a comm card and an interface called an AK SM720, the parameters of the controllers can be viewed changed etc and a running log of the system can be viewed via a pc.

I sat on many Danfoss meetings to dicuss what the new generations of controllers were required to have and each country had there own list, so if you go ahead with this project be careful otherwise it will become over engineered and to expensive as only certain parts will be used by the different countries. In Europe they tend to use temperatures for set points whereas in the UK we tend to use pressure.

I have the full manuals for the 72A if you need them Br Glenn

21-04-2016, 05:44 AM
Full on answer Glenn.

22-04-2016, 02:27 PM
That's the one I was looking for :)

We were looking at using temperature for setpoint, however using pressure and allowing two decimals makes it just as accurate and more versatile instead of having to add pressure temp calculations for all the different refrigerants :)