AC Thermostat\Setup problem?

I was measuring the power consumption of an air conditioner and ran into what seems like a problem with the thermostat.
Background: This is a 1.5 Ton Mitsubishi Mr.Slim Xtreme. Thermostat is set at 26 degrees Celcius via remote. The unit is installed in a 14x13 feet room. There are two indicator lights on the unit, one of which goes off when the ac has been running for some time. Its my understanding that this indicates when the desired temperature has been reached and the ac is on maintenance mode (I don't have the manual handy, the unit is like a decade old now). The AC does seem to stop lowering the temperature further when this light goes off, though I don't have a room thermometer to verify this. The power meter is working fine(checked with rated appliances).
It turns out that my ac consumes 1140 Watts, even on maintenance mode (second light off). I observed the reading for like an hour and it didn't fluctuate more than 20W around that value. I am no expert but I think that the unit should consume significantly lower energy when on maintenance mode.
Here are pics from after 33 minutes of usage. I got around the same consumption for the entire hour before load shedding kicked in.
Is there something wrong with the thermostat, or the indicator light, or with the room-setup or is my understanding of maintenance-mode wrong? Also anyone know where I could grab a good digital room thermometer to check this.

Mitsubishi AC indicator lights are a confusion. One thinks when one light goes off, the set point temperature has been achieved and compressor has stopped. Unfortunately this is not the case. Depending upon your exact model, one light will turn off approximately 3 degrees before the set point temperature has reached. For example if you had set the temperature to be at 26C, one light will go off at about 29C while AC will be still running at full power.

During this maintenance mode, the power consumption is not lowered. Remember this is ON/OFF control of compressor, so it is either stopped or running at full capacity.

Now 1140 watts is something to check for a 1.5T AC. Either your measuring instrument is not correctly measuring, or your AC is low at gas. My Mr. Slim (0.75T) consumes this much power of about 1000W.

[quote=", post:2, topic:22109"]

Mitsubishi AC indicator lights are a confusion. One thinks when one light goes off, the set point temperature has been achieved and compressor has stopped. Unfortunately this is not the case. Depending upon your exact model, one light will turn off approximately 3 degrees before the set point temperature has reached. For example if you had set the temperature to be at 26C, one light will go off at about 29C while AC will be still running at full power.

During this maintenance mode, the power consumption is not lowered. Remember this is ON/OFF control of compressor, so it is either stopped or running at full capacity.

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Thanks, I wonder why they do this, maybe its to give the impression to users about mitsubishi having fast cooling speed or something. The problem however remains, my AC doesn't cool the room within the hour, and it gets interrupted due to load shedding ... so its essentially working non-stop, is there anything I can do to fix this? Could the potential low gas pressure have something to do with this?

[quote=", post:2, topic:22109"]

Now 1140 watts is something to check for a 1.5T AC. Either your measuring instrument is not correctly measuring, or your AC is low at gas. My Mr. Slim (0.75T) consumes this much power of about 1000W.

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So to be sure I recheck the meter on three rated appliances, a 24W Energy Saver, an old 100W filament bulb, and a microwave rated at 1400W:

With an electronic meter I suppose there is always some margin of error, but I believe its fairly low as shown above. How off am I from the expected wattage for a 1.5T AC at full power? I'll be sure to have the gas checked though.

Your measuring instrument seems reasonably good.

Before we draw any conclusion on why your 1.5T AC is drawing too low power, let;s check the following.

1) What is the model number on the silver sticker on the indoor unit ? It should be something like MS12xxx or similar.

2) To verify the the gas, you will need to approach the outdoor unit. After running the AC for about 20 minutes, you should check the bigger copper pipe (going into the room) to feel if it is cold. If bigger pipe feels cold, the gas is OK.

Now if the gas is also OK, I think you don't have a 1.5T unit. A 1.5T is 18000 BTU/Hr and should easily consume about 12-15A current.

Check this PDF (page 8) for power consumption of 1.5T outdoor unit.

http://www.mitsubishipro.com/media/214355/ob%20274%20ms-t%20tech.pdf

[quote=", post:4, topic:22109"]

Now if the gas is also OK, I think you don't have a 1.5T unit. A 1.5T is 18000 BTU/Hr and should easily consume about 12-15A current.

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Captain-Picard-Facepalm.jpg

I have another, 'supposedly' smaller 1 or 1.25 T Mitsubishi unit that looks just like this one. Epic Mixup maybe?

The model number for the AC we are considering is MS-C13VC. The plumbing coming out of the outdoor unit is all covered in insulation and tape, though near the entrance to the unit there is a very small bare patch. I don't have a good view right now, but I can feel the wire, a fairly thin metal pipe, and a bigger stiff piping that is covered in thick rubbery insulation. I'll do the temperature check in a couple of days and update here.

The other unit has a model number MS-C18VC, do the model numbers tell which one is which, because I can't find an online manual for these.

MSC-13VC is not 1.5T, I think it is 13000 BTU/Hr, a little over 1.0T

[quote=", post:6, topic:22109"]

MSC-13VC is not 1.5T, I think it is 13000 BTU/Hr, a little over 1.0T

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^ Switched during installation it seems, funny way to find out. I am surprised though that there is no mention of BTU or Tonnage on the unit stickers,I actually managed to find the original manuals today, and they don't mention a word either (though they confirm what you said about the indicator lights, they are meant to turn off at 2 Degrees above the required temperature). The only indication of tonnage that I managed to find was a set of hand-written invoices that suggest that the AC in question was sold labelled as 1.3T, dealers ... meh!

I am hoping that 1140W is reasonable for a 1.0T-1.3T AC, or should I have the gas checked regardless?

You are right, Mitsubishi manuals don't say anything about power consumption or BTU/Hr.

1140W seems good for a 1.1T (your MSC-13VC is not 1.3T but 1.1T). Now coming back to checking the thermostat, you can check at some higher room temperature. It is,in fact, difficult to AC to reach 26C in hot summers. Best is to set the AC at 28-29C and then check through your power meter if compressor really turns off and on.

In case of 1.1T at 1140W, I believe gas is not an issue. Also I hope the installer did not swap the indoor units with each other (1.1T with 1.8T, both are physically different sizes)