Adjustiing/mod'ing digital thermostat on LG window air conditioner

[Dan]

I just bought an LG 8000 BTU window air conditioner, model LWHD8000RY6.
The unit has a digital thermostat, which on its lowest setting
displays 60 degrees. However, it is not possible even on this lowest
setting to get the machine to put out cold air below about 69 degrees.
Note I do not mean the machine does not have the capacity to cool the
space (a bedroom of about 175 sq') below 69 degrees, but rather, the
thermostat shuts the compressor off at 69, even when it is set at "60".
I tried moving the electronic temp sensor (thermistor?) from the front
of the evaporator to a position out in the room, thinking this spot
would be warmer & therefore the unit would run longer. This dropped the
room temp about 2 degrees further, to around 67. My wife & I would
prefer about 65, if not lower, for sleeping. Again, this is not a case
of the unit lacking the cooling capacity to reach lower temps, the
thermostat just won't turn the compressor on any lower. So I am
wondering if there is generally a way of adjusting these digital
thermostats (I had a similar issue with a unit having an old style
mechanical thermostat, the type which can be adjusted be varying the
spring tension on the thermostat, tweaking this I was able to get the
unit to attain a lower temp). Perhaps there's a trimmer pot on this
electronic thermostat which can be tweaked? As a second option, maybe I
could connect a wall mount thermostat of the type used on a central air
unit, which would be more accurate. Does anyone know if this can be
done? I'm guessing the thermostat on a window unit directly turns the
compressor on and off, and therefore has the current switching capacity
required for this, while a wall mount type for a central unit probably
signals a central control board on the furnace/ac, which has a relay
that does the actual switching. Is this the case? I could probably set
up a relay, still we're beginning to get to the point of a lot a
screwing around by that time. Anyone have any ideas?

TIA

Dan

 

[[email protected]]

As a second option, maybe I
could connect a wall mount thermostat of the type used on a central air
unit, which would be more accurate. Does anyone know if this can be
done? I'm guessing the thermostat on a window unit directly turns the
compressor on and off, and therefore has the current switching capacity
required for this, while a wall mount type for a central unit probably
signals a central control board on the furnace/ac, which has a relay
that does the actual switching. Is this the case? I could probably set
up a relay, still we're beginning to get to the point of a lot a
screwing around by that time. Anyone have any ideas?

I also have an LG air conditioner with digital controls and would like
to do the same. Mine is a rather large and expensive unit, so I am
reluctant to butcher it or risk damaging it. I am curious as to what
type of component the temperature sensor is.

If the temperature sensor for the digital controls is a thermistor
then it would be easy to make a circuit involving a central AC
thermostat (you would need a stat that uses a relay output instead of a
triac) and a couple of resistors to emulate the sensor indicating a
high temperature or a low temperature to manually control the
compressor.

If the sensor is some sort of temperature sensitive transistor, it
would be a bit tougher to design a similar circuit. If it's a
thermocouple, it is even worse.

If you were to do something like this you would have to beware of
evaporator coil freeze up, especially at the temperature you wish to
run the unit at, since the temperature sensor is no longer in front of
the coil. Evaporator coil freezup can easily ruin the compressor.

Eric

 

[Dan]

I also have an LG air conditioner with digital controls and would like
to do the same. Mine is a rather large and expensive unit, so I am
reluctant to butcher it or risk damaging it. I am curious as to what
type of component the temperature sensor is.

If the temperature sensor for the digital controls is a thermistor
then it would be easy to make a circuit involving a central AC
thermostat (you would need a stat that uses a relay output instead of a
triac) and a couple of resistors to emulate the sensor indicating a
high temperature or a low temperature to manually control the
compressor.

If the sensor is some sort of temperature sensitive transistor, it
would be a bit tougher to design a similar circuit. If it's a
thermocouple, it is even worse.

If you were to do something like this you would have to beware of
evaporator coil freeze up, especially at the temperature you wish to
run the unit at, since the temperature sensor is no longer in front of
the coil. Evaporator coil freezup can easily ruin the compressor.

Eric

Eric-Thanks for the reply. I agree about the freeze up potential, have
to keep an eye on it at least initially. I have forced it to run longer
by holding the temp sensor between my fingers for a period of time, so
far minimal frosting on the evaporator. On the other hand, it's not
that humid here at the moment. Another option might be to slightly heat
the sensor with something like a low wattage light bulb placed at a
distance, though again this is kind of a PITA, especially in a bedroom
:-/ This particular unit was fairly cheap, about $160.

Dan

 

[Mike Berger]

Are you sure it's not shutting down for another reason, like
condensation or restricted airflow?

 

[Ken Weitzel]

Eric-Thanks for the reply. I agree about the freeze up potential, have
to keep an eye on it at least initially. I have forced it to run longer
by holding the temp sensor between my fingers for a period of time, so
far minimal frosting on the evaporator. On the other hand, it's not
that humid here at the moment. Another option might be to slightly heat
the sensor with something like a low wattage light bulb placed at a
distance, though again this is kind of a PITA, especially in a bedroom
:-/ This particular unit was fairly cheap, about $160.

Dan

Hi Dan...

I suspect you and your wife might like a 5 or 10 watt
ceramic resistor with a half amp or so at 12 volts better than
a light bulb

However, I respectfully suggest that perhaps you and Eric are
asking more of a home cooling unit than it was designed for and
intended to do. Think perhaps you guys liking to sleep at
65 degrees F are in a real minority. Not to mention the
cost on your hydro bill

My car has auto climate control. Switched to "US" mode, the
auto temp will drop degree by degree, until it suddenly jumps
to 50F. I'd assumed that meant that it would run virtually
forever, or until it reached 50 if ever. Not so, just tried
it. Something else shuts it down long before it gets that
cold.

Just my 2 cents, FWIW

Take care.

Ken

 

[Dan]

Are you sure it's not shutting down for another reason, like
condensation or restricted airflow?

Yes, it's the thermostat. After I pulled the sensor from the front of
the evaporator, holding it in my hand momentarily warms it enough to get
the compressor to kick in.

Dan

 

[Dan]

Hi Dan...

I suspect you and your wife might like a 5 or 10 watt
ceramic resistor with a half amp or so at 12 volts better than
a light bulb

A power resistor is a great idea! Why didn't I think of that!?!

However, I respectfully suggest that perhaps you and Eric are
asking more of a home cooling unit than it was designed for and
intended to do. Think perhaps you guys liking to sleep at
65 degrees F are in a real minority. Not to mention the
cost on your hydro bill

Hydro bill shmydro bill ;-) I don't doubt you're correct about our
preference for low temps. We open the bedroom windows in February!
Honestly though, I have met others who also like sleeping in the cold.
I have been able to attain the desired temps with other 8kbtu window
units in another bedroom in a climate with a much higher heat load
applied; hotter weather, higher humidity, less insulation, less shade,
etc. I think the unit is capable of what I want, the thermostat just
doesn't think so ;-)

My car has auto climate control. Switched to "US" mode, the
auto temp will drop degree by degree, until it suddenly jumps
to 50F. I'd assumed that meant that it would run virtually
forever, or until it reached 50 if ever. Not so, just tried
it. Something else shuts it down long before it gets that
cold.

Probably the same thing, the thermostat is killing the car's AC
compressor clutch before it gets to the indicated temp. I didn't really
expect the "degrees" indicated by the unit's digital readout to be all
that accurate, but if they have a scale going down to 60, I really do
think the damn thing ought to be capable of more than 69 when used in a
space of the size etc. indicated by the btu output.

 

[J. Clarke]

I just bought an LG 8000 BTU window air conditioner, model LWHD8000RY6.
The unit has a digital thermostat, which on its lowest setting
displays 60 degrees. However, it is not possible even on this lowest
setting to get the machine to put out cold air below about 69 degrees.
Note I do not mean the machine does not have the capacity to cool the
space (a bedroom of about 175 sq') below 69 degrees, but rather, the
thermostat shuts the compressor off at 69, even when it is set at "60".
I tried moving the electronic temp sensor (thermistor?) from the front
of the evaporator to a position out in the room, thinking this spot
would be warmer & therefore the unit would run longer. This dropped the
room temp about 2 degrees further, to around 67. My wife & I would
prefer about 65, if not lower, for sleeping. Again, this is not a case
of the unit lacking the cooling capacity to reach lower temps, the
thermostat just won't turn the compressor on any lower. So I am
wondering if there is generally a way of adjusting these digital
thermostats (I had a similar issue with a unit having an old style
mechanical thermostat, the type which can be adjusted be varying the
spring tension on the thermostat, tweaking this I was able to get the
unit to attain a lower temp). Perhaps there's a trimmer pot on this
electronic thermostat which can be tweaked? As a second option, maybe I
could connect a wall mount thermostat of the type used on a central air
unit, which would be more accurate. Does anyone know if this can be
done? I'm guessing the thermostat on a window unit directly turns the
compressor on and off, and therefore has the current switching capacity
required for this, while a wall mount type for a central unit probably
signals a central control board on the furnace/ac, which has a relay
that does the actual switching. Is this the case? I could probably set
up a relay, still we're beginning to get to the point of a lot a
screwing around by that time. Anyone have any ideas?

If I may venture a stupid question, are you sure that the thing isn't simply
defective?

 

[[email protected]]

If I may venture a stupid question, are you sure that the thing isn't simply
defective?

Or even if that's the way that particular unit was made, since the OP
just bought it, why not just take it back and get one from another
manufacturer? I would think someone must make one that goes below 68.

As a kludge, it sounds like the small power resistor secured to the
temp sensor and controlled by a thermostat located elsewhere would
work. You'd have to do the math, make sure the thermostat could
handle the current or use a relay, use low voltage (12V) for safety,
etc.

 

[Rheilly Phoull]

I just bought an LG 8000 BTU window air conditioner, model
LWHD8000RY6. The unit has a digital thermostat, which on its lowest
setting displays 60 degrees. However, it is not possible even on this
lowest
setting to get the machine to put out cold air below about 69 degrees.
Note I do not mean the machine does not have the capacity to cool the
space (a bedroom of about 175 sq') below 69 degrees, but rather, the
thermostat shuts the compressor off at 69, even when it is set at
"60". I tried moving the electronic temp sensor (thermistor?) from
the front of the evaporator to a position out in the room, thinking
this spot would be warmer & therefore the unit would run longer. This
dropped the room temp about 2 degrees further, to around 67. My
wife & I would prefer about 65, if not lower, for sleeping. Again,
this is not a case of the unit lacking the cooling capacity to reach
lower temps, the thermostat just won't turn the compressor on any
lower. So I am wondering if there is generally a way of adjusting
these digital thermostats (I had a similar issue with a unit having
an old style mechanical thermostat, the type which can be adjusted be
varying the spring tension on the thermostat, tweaking this I was
able to get the unit to attain a lower temp). Perhaps there's a
trimmer pot on this electronic thermostat which can be tweaked? As a
second option, maybe I could connect a wall mount thermostat of the
type used on a central air unit, which would be more accurate. Does
anyone know if this can be done? I'm guessing the thermostat on a
window unit directly turns the compressor on and off, and therefore
has the current switching capacity required for this, while a wall
mount type for a central unit probably signals a central control
board on the furnace/ac, which has a relay that does the actual
switching. Is this the case? I could probably set up a relay, still
we're beginning to get to the point of a lot a screwing around by
that time. Anyone have any ideas?
TIA

Dan

I'd be thinking of a pot in parallel or series with the thermistor.
Assuming you dont want to open up the controller to find adjustments.

 

[Dan]

Or even if that's the way that particular unit was made, since the OP
just bought it, why not just take it back and get one from another
manufacturer? I would think someone must make one that goes below 68.

As a kludge, it sounds like the small power resistor secured to the
temp sensor and controlled by a thermostat located elsewhere would
work. You'd have to do the math, make sure the thermostat could
handle the current or use a relay, use low voltage (12V) for safety,
etc.

Not a stupid question at all. I'm planning to at least swap out this
one today, I just wanted to get some input in case the 2nd example
performs the same way. The problem is this wasn't a typical double hung
installation, the window is a large (tall but narrow) panel which swings
out vertically, I had to remove the window (large, heavy, 2nd floor, no
outside access) & make & install a plywood panel of the right dimensions
to go above the unit. In other words, taking the damn thing out &
putting it back in is a major PITA. I could try another brand, but I'm
not guaranteed it won't behave the same way (it's been at least 7 years
since I had to deal with a window AC, I thought perhaps this was "just
they way they are now", that maybe they won't go any lower for energy
concerns or something) and if its size is different it may require
modifying what was a fairly troublesome installation, especially if it's
shorter & I have to cut/paint another longer plywood panel. Too bad the
mother couldn't just WORK the way I wanted out of the box, (really, I
don't think expected lower than 69 is too much to ask) but alas things
don't seem to go that way for me too often... ;-)

Thanks also for the suggestions on a work around.

Dan

 

[Andy Cuffe]

I just bought an LG 8000 BTU window air conditioner, model LWHD8000RY6.
The unit has a digital thermostat, which on its lowest setting
displays 60 degrees. However, it is not possible even on this lowest
setting to get the machine to put out cold air below about 69 degrees.

I suspect they are limiting it to 69 in order to save energy (probably
an EPA regulation). The simplest solution would be to buy an A/C with
an analog thermostat. It's probably possible to modify the digital
thermostat, but you'd have to figure out how by tracking the circuit
and looking for data sheets for any ICs. It's probably custom to that
A/C and it will be impossible to find a schematic. It might be as
simple as a jumper to switch it to non-EPA mode, or you might have to
modify the temperature sensor circuit. If you modify the temperature
sensor, you'd have to live with an inaccurate temp display (eg. it
still shuts off when it thinks it's 69, but it's actually 65).
Andy Cuffe

[email protected]

 

[Dan]

I'd be thinking of a pot in parallel or series with the thermistor.
Assuming you dont want to open up the controller to find adjustments.

I thought of that as well, easy enough to check but at the moment I'm
not sure it IS a thermistor...

Dan

 

[GregS]

I thought of that as well, easy enough to check but at the moment I'm
not sure it IS a thermistor...

Round bulb in center of evaporator? I'm just listening. I am going to try
and set mine to below the mark tonight. Mine just has a 9.7 rating.??


greg

 

[larry]

I thought of that as well, easy enough to check but at the moment I'm
not sure it IS a thermistor...

Dan

my 5K gold star window air:
bg5200er
limited schem on top of black plastic control box)
sensor - thermistor(non polar) in black epoxy glob:
oF ohms
212 = 1.2k
finger(98) = 6.6k
warm room(82) = 7.8k
32 = 26k

negative factor (hotter = lower resistance)

draw a linear chart, see if my numbers are on the line

use ohms law

have fun

-larry / dallas

BTW- if anyone trashes one of these, I would like to buy
your circuit board and keyboard/display. I have a GE I want
to teach new tricks ;-)

 

[Dan]

my 5K gold star window air:
bg5200er
limited schem on top of black plastic control box)
sensor - thermistor(non polar) in black epoxy glob:
oF ohms
212 = 1.2k
finger(98) = 6.6k
warm room(82) = 7.8k
32 = 26k

negative factor (hotter = lower resistance)

draw a linear chart, see if my numbers are on the line

use ohms law

have fun

-larry / dallas

BTW- if anyone trashes one of these, I would like to buy your circuit
board and keyboard/display. I have a GE I want to teach new tricks ;-)

Thanks Larry, very interesting info. If the sensor in mine also turns
out to be a thermistor (a likelihood) it really simplifies tweaking. In
the case of your figures, you could fool the thermostat into thinking it
was 98 when it was actually 82 by shunting the thermistor with 42,900
ohms. Since the range of actual thermistor values over real room
temperatures would be fairly narrow, something along these lines would
probably be safe (only down side is the temp readout would be wrong, but
since it is anyway (says 60 when it's 69) no loss there). Also very
easy/cheap to implement.

Dan

 

[Ken Weitzel]

Thanks Larry, very interesting info. If the sensor in mine also turns
out to be a thermistor (a likelihood) it really simplifies tweaking. In
the case of your figures, you could fool the thermostat into thinking it
was 98 when it was actually 82 by shunting the thermistor with 42,900
ohms. Since the range of actual thermistor values over real room
temperatures would be fairly narrow, something along these lines would
probably be safe (only down side is the temp readout would be wrong, but
since it is anyway (says 60 when it's 69) no loss there). Also very
easy/cheap to implement.

Dan

Hi Dan...

With all this great info, seems you can't go wrong!

Another suggestion might be to consider using perhaps a 100k
variable rather than a fixed resistor.

A bit of tweaking might let you make the readout "wrong" by
10 degrees F, so that for instance you could more understandably
have 65 degrees read 75, etc.

Take care.

Ken

 

[Dan]

Hi Dan...

With all this great info, seems you can't go wrong!

Another suggestion might be to consider using perhaps a 100k
variable rather than a fixed resistor.

A bit of tweaking might let you make the readout "wrong" by
10 degrees F, so that for instance you could more understandably
have 65 degrees read 75, etc.

Take care.

Ken

I agree a pot is the way to go, after calculating a ballpark figure.

Thanks!

Dan

 

[Mike Berger]

The very energy-efficient models do work like that, and take
forever to cool down a space. For your purposes you would
probably be happier with an inefficient model, and you might
need to size it up.

 

[[email protected]]

I just bought an LG 8000 BTU window air conditioner, model LWHD8000RY6.
The unit has a digital thermostat, which on its lowest setting
displays 60 degrees. However, it is not possible even on this lowest
setting to get the machine to put out cold air below about 69 degrees.
Note I do not mean the machine does not have the capacity to cool the
space (a bedroom of about 175 sq') below 69 degrees, but rather, the
thermostat shuts the compressor off at 69, even when it is set at "60".
I tried moving the electronic temp sensor (thermistor?) from the front
of the evaporator to a position out in the room, thinking this spot
would be warmer & therefore the unit would run longer. This dropped the
room temp about 2 degrees further, to around 67. My wife & I would
prefer about 65, if not lower, for sleeping. Again, this is not a case
of the unit lacking the cooling capacity to reach lower temps, the
thermostat just won't turn the compressor on any lower. So I am
wondering if there is generally a way of adjusting these digital
thermostats (I had a similar issue with a unit having an old style
mechanical thermostat, the type which can be adjusted be varying the
spring tension on the thermostat, tweaking this I was able to get the
unit to attain a lower temp). Perhaps there's a trimmer pot on this
electronic thermostat which can be tweaked? As a second option, maybe I
could connect a wall mount thermostat of the type used on a central air
unit, which would be more accurate. Does anyone know if this can be
done? I'm guessing the thermostat on a window unit directly turns the
compressor on and off, and therefore has the current switching capacity
required for this, while a wall mount type for a central unit probably
signals a central control board on the furnace/ac, which has a relay
that does the actual switching. Is this the case? I could probably set
up a relay, still we're beginning to get to the point of a lot a
screwing around by that time. Anyone have any ideas?

I didn't note the model # but I just bought an 8000 BTU at The Home
Depot.
I tested it and it goes to 60 deg. I put a thermometer near the sensor.

gs