Decrease room/start temperature

[kappl01]

Hello members of the Forum,

Being a newbie with airconditioning and in this forum I want, after unfruitful searches, ask you advice on the following.

A member of the family has a split unit Dailin airco (rather old I think, type T22LVEFW).
It cools a bedroom. Starting temperature of the unit is approx 24 degree C, this is the minimum temperature setting of the 5-position switch on the control unit. He would like to have the unit to start at a lower temperature of 18 degrees C.

Is this a "normal" temperature? Beinig an electronic engineer, I saw in the control unit a themistor which I think is in a measuring bridge. I think I can experiment with this. In advance I want to ask your opinion on this matter.

Thanks in advance,

Kind Regards,

Ko (Netherlands)

[Peter_1]

Welkom op ons forum vanuit het zonovergoten België.

If you go to low, then your coil can freeze up. But you could give it a try by switching another thermistor in serie or parallel, depends on the type (NTC or PTC)
We've done it many times on newer Mitsubishi units where we have to maintain 4°C (vending trucks vegetables)
It's possible that going that low that the thermistor in the evapoartor coil will interprete this as a frosting up of the coil and that this will energise a defrost cycle.

[taz24]

Welkom op ons forum vanuit het zonovergoten België.

If you go to low, then your coil can freeze up.

It's possible that going that low that the thermistor in the evapoartor coil will interprete this as a frosting up of the coil and that this will energise a defrost cycle.


I agree with Peter.

The evap temp will be a little lower at 18degC.

At 18degC the evap would still be above freezing so you should be OK and as Peter says the auto defrost may kick in and defrost the evap.
Try it but just be weary about the defrost issues.

Cheers taz.

[kappl01]

Peter and Taz,


Thanks for your replies/ideas.

So it must be possible, but I have to notice the defrost issue.
In the meantime I measured the thermistor with different temperatures.
24 degrees is 2.3 kohms, 18 degrees is 2.950 kohms. My idea is to fool the control unit
thinking it is 6 degrees warmer in the room, so I want to place a resistor in parallel with the thermistor which lowers the total resistance. Placing 8.2 kohm in parallel decreases the value 2.950 kohm @ 18 degrees to the value of 24 degrees ( 2.3 kohm).

I think with the parallel resistor I shift the range 6 degrees higher resulting in faster start (at 18 degrees) of the airco.

I let you know what the results are.
If you have comments on my ideas please let me know.

Regards, Ko(NL)

(@Peter: Bedankt voor je welkom)

[Peter_1]

Kappl01, yes I have a comment and that is that it will work this way.
Let us know your progress.
This is the same way I'm doing it with the Mitsubishi's, fooling the controller.

[taz24]

I think with the parallel resistor I shift the range 6 degrees higher resulting in faster start (at 18 degrees) of the airco.

I let you know what the results are.


Regards, Ko(NL)

(@Peter: Bedankt voor je welkom)


I'm not sure I have understood your post correctly.
Do you want to adjust the temp of the room to be lower overall or are you adjusting the stat in an attempt to cool the room quicker?

If you want to run the temp of the room lower then you should be ok.

If you are doing it to increase the speed in which the room pulls down to temp then you will not achieve any benifit.

Could you confirm why you are adjusting the temp sensor?

Cheers taz.

[Peter_1]

Tazy, the minimum allowable setpoint of the thermostat is not low enough fo our Dutch friend, so he will only make an offset to the sensor.
This will work.

[taz24]

Tazy, the minimum allowable setpoint of the thermostat is not low enough fo our Dutch friend, so he will only make an offset to the sensor.
This will work.


Thanks Peter :) .

Cheers taz.

[kappl01]

OK Peter and Taz,

Only offset is what must be done.

Keep you informed,

Regards,

Ko

[kappl01]

Because of a holiday of the owner of the unit Regretfully I cannot do my experiment.

Within 2 weeks I'll report on the results.

Regards, Ko