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I have a Trane XV95_060 for furnace and Trane XR15-018 for AC
I would like to know if the speed of the blower can be adjusted (increased)

Before I had a 1ton AC and that was all right for the house That was replaced with the above 1.5 ton and apparently it can not cool the house as needed. I am not sure what is wrong but I am trying to understand why it is not working better than before

Edit: OK After reading more I realized that my problem might be the opposite and that is that the air goes too fast through the coil and it does not cool enough. I have 15C at the register level. There is not much condense and I do not see any change in the RH when I run the AC for longer periods of time

Here is what I had before

enter image description here

and here is what was configured on my current unit enter image description here

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  • It would probably help to have a look at the (new) motor and squirrel cage or fan. Commented Jun 28, 2016 at 19:49
  • Can't really touch it, it is under warranty, I am just trying to see what I need to ask the guys to do
    – MiniMe
    Commented Jun 29, 2016 at 0:51
  • A difference at the register of 15 °C is ok. I'm not sure I understand what you mean by, "there is not much condense". Most AC units have anti-condenstion coatings to prevent condensation. Do you have a separate dehumidifier, or is this AC supposed to be acting like a dehumidifier? Commented Jun 29, 2016 at 13:46
  • Well I explained the sales guy that I want a slightly smaller unit (he suggested 2ton) so I can also remove some humidity. I did not know that these things have an anticondense coating. The dehumidifying effect was supposed to be a secondary effect of cooling the house by running the AC longer (since it was slightly undersized)
    – MiniMe
    Commented Jun 29, 2016 at 13:55
  • Do you have a separate dehumidifier? I still can't really explain how a 1 ton unit out-cooled a1.5 ton unit; they don't make 'em like they used to I guess. Commented Jun 29, 2016 at 13:59

1 Answer 1

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When you asked to increase the blower, what you are really asking to do is increase the fan speed (amount of air), right? You could ask the the tech to check/verify that you are getting 1600 CFM (cubic feet per minute) and if you truly are, and if that's not enough, ask them if it is possible to increase it (it might be adjustable). But I am thinking that may not really be the issue.

Your real problem is that it's not cooling the house. I'm not sure if this issue is truly the result of a weak blower (insufficient CFM); it's very possible, but honestly, a 1.5 ton unit is pretty small. For a 1,000 square foot house, I might recommend at least one 3 ton unit or preferentially, two 2 ton units, depending on your lattitude (summer temperature). Below is a map and chart. I would generally recommend double the what they recommend on the chart below, because you will only use what you need.

In case you didn't know, having more (AC tonnage) doesn't mean that you will use more. If you set the thermostat to say 70 °F, then the AC will turn off when the house is at 70 °F. If you have fifteen 3 ton units, you will use the same amount of energy to cool the house to 70 °F as one 2 ton unit (give or take maybe 5% energy).

enter image description here

Map source:http://www.acdirect.com/ac-package-unit-learning-center-ac-sizing-calculator

Edit based on comment that the AC is actually a dehumidifier:

Dehumidifier? Well, that's a key piece of information. The old unit may not have been well designed as a dehumidifier; if the newer unit has been set up to be more like an actual dehumidifier then that would explain the question. The older unit was probably designed (more) for cooling. The newer unit might be a more for dehumidifying.

The difference between an air conditioner and a dehumidifier is that the air in a dehumidifier first passes through the cooling coil and then back through the heating coil (basically, there will be little change in room temp) and then back into the room as dry air. In fact, the temperature might be higher.

Unfortunately, this means that the answer is to install an actual air conditioner or re-engineer the dehumidifier to make it an air conditioner.

Edit2 Okay it's not a dehumidifier. It's a regular AC and you have a separate dehumidifier. Regular AC units have protective coatings to help prevent condensation on the evaporating/cooling coil. That protective coating usually doesn't last forever which is why older AC units often collect water. Typically, you don't want the AC to collect water (that causes rust and mold issues). For a regular AC unit, having the blower on high is okay. Lower speeds (lower CFM) may cause condensation to occur (depending on all the bells and whistles).

The dehumidifier is where you do want condensation- to remove moisture. Cooling the air should help your dehumidifier to operate, because as the temperature is lowered, the relative humidity will increase. When measuring the relative humidity, the temperature is a/the factor. For example, say that you have 44% humidity at 70 °F; it has about 0.26 grams of water/vapor per cubic foot. At 50 °F the relative humidity of 0.26 grams of vapor per cubic foot would be about 92%. A dehumidifier should be able to operate more efficiently at 92% RH than 44% RH... so that's why an AC unit can help a dehumidifier.

I suspect that when you measured the RH in the basement it was higher than you expected (maybe about the same as the RH outside), but if the temperature was lower in the basement (than outside), then having the same RH means that you actually have less water vapor in the basement, where it's cooler.

To recap: The service technician might be able to increase (or decrease) the blower speed, but that would probably lower the AC's cooling efficiency. Your new AC unit is not collecting water (yet) because the anticondensation coating hasn't been compromised (yet); and that's a good thing. A 1.5 ton AC unit may not be large enough to cool the basement. Cooling the basement should help the dehumidifier. And remember, the relative humidity is based on the temperature.

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  • The AC was undersized to run longer in order to dehumidify a humid basement. How can you explain that an older AC was OK at a lower capacity but the newer one with a higher capacity is not OK
    – MiniMe
    Commented Jun 29, 2016 at 13:07
  • I updated my post too
    – MiniMe
    Commented Jun 29, 2016 at 13:30
  • You got it wrong, this is an AC unit but according with the specialists running the AC longer helps with dehumidifying the air in the space that is being cooled
    – MiniMe
    Commented Jun 29, 2016 at 13:33
  • @MiniMe Based on your edit, indeed, slowing the air down will allow more vapor to condence on the evaporating/cooling coil. Also, lowering the room temperature (running the AC longer) helps with dehumidifying the air in the space that is being dehumidified. Commented Jun 29, 2016 at 13:54
  • Ok so now that we are clear on that how do I slow down the blower when the AC is running. I learned that the AC has the Confort settings which purposely runs the blower slower in the first 5 minutes of the cycle in order to dehumidify ... Is it possible to do that for longer? I also learned that this might lead to coil freezing so I guess a balance must be reached
    – MiniMe
    Commented Jun 29, 2016 at 13:58

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