Mercury climatic evap pressure difference

[marc5180]

I've been working on a Mercury Climatic unit today and found the sytem not running.

I looked in the trend controller and found water system fault was on.

Also in the trend controller the max water DP set point was 32 kpa and min set point is 18kpa but Dp plate was reading -0.8kpa which seemed to be causing the fault.

Evap pressure difference at design is 24kpa

I spoke to another engineer who said they had come across this at a few different sites with the same unit and had changed the sensors on one of them but this didn't work.

The previous company who had the contract left a note inside the panel saying " to reset the fault turn mains power off then back on again" but thats not the answer

Design presssure difference is 3.5psi but not quite sure what it means if the readings drop below or above the figure.
can anyone help

[Grizzly]

Hi Marc.
Just guessing from what you have posted.
But could the software be reading the diff as low because the probes are the wrong way round?
Or even someone has fitted an NTC instead of a PTC?
I would start with proving the digital readings against Analog.
Grizzly

[marc5180]

Hi Grizzly sorry for the late reply, i'm having problems with my internet connection.

I'm pretty sure the sensors haven't been changed on any of these units apart from the one that the other engineer changed because none of them look new and there is nothing in the service records.

When i disconnect the sensors from the trend the data doesn't alter which is strange, normally if i unplug for example the ambient sensor then it automatically reads -50C.

I'm wondering if the sensors could be the wrong way round as you say.

I'm waiting for Mercury climatic to get in touch with me on monday and if i get any furthur then ill update then.

Thanks

[Grizzly]

Hi Marc.
What you describe is strange isn't it?

The issue seems to be that despite whether the sensors are in the wrong place or indeed wrong themselves.

There is no display change when they are disconnected?
I will be intrigued as to how things progress.
Keep us posted.
Thanks Grizzly