I need an Air Con expert for some sane advice.....

There might be a simple remedy/explanation for this but I am confused;

We?ve just moved villa in the same area.
3 floors, 7 Air Con controls/thermostats in total.
Been having a bit of a nightmare as trying to find any sort of expert in any field in this country is a task.
Whatever the query, the stock answer is always negative.

Anyway, AC has been a mess as soon as we moved in.
Outside temp here is 113f at the moment so it's no joke.

Now starting to get somewhere as the engineers have been here daily.
One thing I cannot get these guys to understand is an issue with some of the room stats. I?ll set the control at 23c. That?s fine, AC comes on and off as it should most of the time. Until?.it won?t click on and the room temp for sure is around 26c. If I press the button which shows the current room temp this displays 18 or 19 (which the room definitely isn?t) which is why the AC wont fire up.
If I override the stat by clicking on manual, within a minute the room temp display shows 25! Then the AC is working OK for a while then we start all over again.
Now I?ve said that the control unit in the room is faulty but they are having none of it. What baffles me is that 3 other rooms have the same problem.
Can they all be faulty with same issue? Villa was built in 2006.

Any ideas before I murder someone?

Re: I need an Air Con expert for some sane advice.....

Need to know what kind of system it is...Is it a multizone unit with DX cooling, or chilled water with fan coils, or a citymulti mini split with 7 different air handlers...Is the system taking an average of all the sensors to decide when to turn on the compressor? There isn't enough info to make an intelligent comment...

Re: I need an Air Con expert for some sane advice.....

Thanks for the quick response my friend.

As far as I can make out, there are 7 AC units on the roof (split system?) this is the manual for the system:



All independently controlled by one of these:



Does this help?

Re: I need an Air Con expert for some sane advice.....

If you have controllers doing the same thing wrong on different units, you have to think what is common to all of them...They could have the temp sensor bad and be reading wrong...If there is a hole in the wall for the wire to run into the sensor, is the hole to big and is there air coming though the back causing the stat to read wrong(usually would cause it to read higher and run longer) or is it operator error...Basically any DX coil is going to run a certain duct split(difference between supply air and return air) at 30-40% humidity its going to be 18-22 degrees...Higher humidity it the split will be lower...Lower humidity the split will be higher...If the split is way wrong you could have a charge problem...Those units aren't very complicated(except for the remote control/thermostat)...

Re: I need an Air Con expert for some sane advice.....

Is this a new installation....or a new building? i.e. has the system always had this problem?

Are there any obvious "oooops" with the ductwork? Warm air returns too close to cold air inlets?....cold air inlets blowing on T/stats?...etc.

Re: I need an Air Con expert for some sane advice.....

Tim Frank said:

Is this a new installation....or a new building? i.e. has the system always had this problem?

Are there any obvious "oooops" with the ductwork? Warm air returns too close to cold air inlets?....cold air inlets blowing on T/stats?...etc.

Click to expand...

6 years old Tim no obvious "oooops" whatever they are!

hrdwrkingacguy said:

If you have controllers doing the same thing wrong on different units, you have to think what is common to all of them...They could have the temp sensor bad and be reading wrong...If there is a hole in the wall for the wire to run into the sensor, is the hole to big and is there air coming though the back causing the stat to read wrong(usually would cause it to read higher and run longer) or is it operator error...Basically any DX coil is going to run a certain duct split(difference between supply air and return air) at 30-40% humidity its going to be 18-22 degrees...Higher humidity it the split will be lower...Lower humidity the split will be higher...If the split is way wrong you could have a charge problem...Those units aren't very complicated(except for the remote control/thermostat)...

Click to expand...

No holes in the walls for air to seep, got the engineer to change a stat for a new one, same model, same problem.
I have since singled out that this issue is only if the stat is on auto fan mode, and it's when this control switches the ac off when it's reached set temp, that's when the problem occurs.
If I leave the fan on manual, running all the time, cooling mode, no problem except that the fan is running all the time and wasting power.

I have 3 modes on this system, Cooling, Soft Dry and Auto (AI) Can you explaiin the 'AI' mode

Re: I need an Air Con expert for some sane advice.....

I need an actual model # of the indoor unit and model # of the condenser on the roof to help any further...Auto mode is going to look at humidity and sensible temperature and ramp the fan and possibly the compressor based on enthalpy...

Re: I need an Air Con expert for some sane advice.....

hrdwrkingacguy said:

I need an actual model # of the indoor unit and model # of the condenser on the roof to help any further

Click to expand...

Thanks my friend.
I'll try and get these this weekend.

hrdwrkingacguy said:

Auto mode is going to look at humidity and sensible temperature and ramp the fan and possibly the compressor based on enthalpy...

Click to expand...

So are you saying don't use AI-Auto mode?

'enthalpy'......now there's a word I've never heard before. Obviously for intelligent people to use:facepalm:

Re: I need an Air Con expert for some sane advice.....

Enthalpy

Re: I need an Air Con expert for some sane advice.....

hrdwrkingacguy said:

Enthalpy

Click to expand...

Wiki, first thing I did. Like I said.....for clever people to use!