Electronic controller probes wired wrong

[Electrocoolman]

Hi all....here's one for the future to note.

Recently, I've had two brand new counter units from different manufacturers where the Cabinet and Evaporator probes have been cross wired...which isn't immediately obvious!

One was a gravity bunker coil meat counter in my local butchers....everything looked fine but as summer kicked in, he started complaining that product temperature was not cold enough, despite display being -5deg C.
Unit was sited next to the doorway so drafts were thought to be cause (warm air blowing into cabinet).
Measuring the air off evap and cabinet temps showed that there was indeed a discrepancy with display temperature. Refrigeration system checked out OK and bunker coil had full frost line. Keeping the door closed improved matters a lot.
Anyway... some time later the compressor failed....upon replacing compressor and recharging I was amazed at how quickly the empty cabinet pulled down to temperature...the compressor then started to cycle frequently, running for 3-4 mins each time. Again the cabinet temperature was in error....finding the probe and warming it showed the way forward as the penny dropped! The controller was sensing on the evaporator probe and not the cabinet probe.

The second cabinet was a fan blown unit with electric defrost. On first starting up I noted that the fans would not run, but this can be down to time/temp delays. Eventually they did kick in and all seemed well. Not having any info for the controller, I was unable to access the parameters to check or change this.
The next problem to manifest itself (several weeks later) was a 'tinkling' noise from the fans. Ice was suspect and after leaving cabinet off overnight all seemed well, but problem returned a few weeks later! Pulling cabinet apart to get at evaporator revealed little....heater was OK and evaporator was clear. Checked TEV superheat and valve operation whilst access was available.
In the mean time, summer appeared and out came the fans to cool the staff.....along with the complaint that now the cabinet wasn't cold enough and display was wrong!
Suspecting drafts as large fan was sited feet away from cabinet...the ladies were instructed to point them in the opposite direction!
One of the probes then started to play up occasionally, giving error messages on the controller accompanied by aural warnings from the alarm.

Investigation of this last problem identified that the probes were cross wired....and guess what....all the other problems disappeared as if by magic!!

Fortunately I had not supplied either cabinet so I didn't have to pick up the bill under warranty!

Why can't manufacturers use different coloured sheaths on the two probes??

MORAL: Don't assume that because its new its wired up correctly.

Regards Adrian

[Brian_UK]

Aren't you the lucky one ?

Getting both Friday made units in your patch

Glad that you sorted it out in the end and thanks for the heads-up.

[unloadedinher]

Hi.

thats why i like LAE controllers, they have differant colours for there probe, Black probe for temperature sensing and White/grey for evapourator sensing temperature.

the only thing to trust on any cabinet is that you will cut your self...

Lets go back to the good old days, of mancanical-thermostats and pressure switchs, time clocks and contactors.

[anuraruna@gmail]

Hi.



Lets go back to the good old days, of mancanical-thermostats and pressure switchs, time clocks and contactors.

And also to the old thermostatic valves if interested in modifications.