Carrier Infinity a/c UV light and dehumidifier questions

Den6265June 17, 2012

I'm puzzled. I have a 2 year old Carrier Infinity system in south Florida, and have a two part question. The system was installed with an optional single UV light add-on; the light just went out after two years, which I understand is normal. A new light is about $235, and only lasts the two years. The service tech said the single light system is inadequate, anyway, and would eventually cause the coil to collect so much gunk that it would need to be removed and cleaned to the tune of about $650; he was suggesting an upgrade to a $1075 two bulb UV system, guaranteed for 10 years, but still requiring a $200 bulb replacement every two years. First question: any thoughts on the UV system? Is it really necessary? My other, older, ordinary a/c systems in other homes didn't have UV lights, and there were never any coil issues. I've checked with Carrier and the 10 year warranty on the Infinity is not dependent on the UV system at all. Next question related to the dehumidifier: I've set the dehumidifier in the thermostat setting to the maximum 65%, yet the reading on the thermostat says 44-45%. I've also gone into the advanced settings and turned the dehumidifier to OFF, and the humidity reading went up to 51%. So ..the question is this: does turning off the dehumidifier run the risk of corroding or collecting mold/stuff on the coil? Can anyone help me understand the connection with the UV light - is it really necessary - and the coil - will it really corrode if I don't replace the UV light or upgrade to the two light UV system? Otherwise, I think the system is performing quite well. Any information will be helpful. Thanks!

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mike_home

I had Carrier Infinity systems installed in 2009. I recevied quotes from four Carrier Factory Authorized dealers. None of them recommended installing the UV lights. In my opinion they are a waste of money. If you change your filter on a regular basis you will have a clean coil.

There is no built in dehumdifier. The air is dried by running the AC at the low speed for periods of time. Ideally you want the humidity level to be in the 45-50% range. If your AC is running periodically, the air will also dry out. The humidity setting on the thermostat is the maximum humidity limit. The AC will not attempt to dry out the air if the reading is below the limit.

Why are you setting the humidity level so high?

    Bookmark   June 17, 2012 at 8:14PM
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Den6265

I do change the filter every 6 months. I wanted the higher humidity setting because my wife has 'dry eyes' and the eye doctor said higher humidity might ease the symptoms. It's not critical to get to the high setting, just something we thought we'd try. Okay...I get the a/c running will dry out the air, just like all the old systems do. So the setting on the thermostat is just to give the unit a maximum humidity limit? and turning it OFF doesn't really make a difference if the humidity is staying in the 40-50% range anyway? Appreciate your response!

    Bookmark   June 17, 2012 at 8:27PM
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saltidawg

You said:

"I've set the dehumidifier in the thermostat setting to the maximum 65%, yet the reading on the thermostat says 44-45%. I've also gone into the advanced settings and turned the dehumidifier to OFF, and the humidity reading went up to 51%"

And then you concluded:

". So the setting on the thermostat is just to give the unit a maximum humidity limit? and turning it OFF doesn't really make a difference if the humidity is staying in the 40-50% range anyway?"

Does this make any sense?

    Bookmark   June 17, 2012 at 8:53PM
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Den6265

Sorry if my confusion doesn't make sense. Guess that's why it's called 'confusion?'

Overall, my initial concern involved the UV light, the humidity percentage, and the impact on the coil from higher humidity setting and no UV light. It might seem simple to those of you who understand a/c units, but I had to learn by asking.

Thanks to an earlier reply from Mike, and discussion with another knowledgeable a/c person, I think I can say my questions have been answered. The coil will not be negatively impacted if the UV light is not replaced, assuming regular replacement of filters. The humidity will be removed by the a/c unit regardless of the setting on the thermostat, assuming normal functioning of the system.

Thanks again for the replies.

    Bookmark   June 18, 2012 at 8:35AM
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saltidawg

"The humidity will be removed by the a/c unit regardless of the setting on the thermostat..."

So why does your thermostat even have a Humidity setting- with a Maximum setting of 65%? (The setting when you turned it off the humidity rose a lot and you made no mention of temperature not being controlled...

I'm missing something.

    Bookmark   June 18, 2012 at 9:18AM
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mike_home

The Carrier Infinity controller has a humidity sensor. In the summer you can set a maximum humidity limit as well as a maximum temperature. Normally the humidity will drop with the temperature as the AC cycles on an off. On days where the outside temperature is in the 70s, and there is high humidity, the controller may turn on the AC to lower the indoor humidity. This is known as cool to dehumidify. If it is very humid, the controller may go below the thermostat set point up to three degrees in order to reach the desired humidity level.

    Bookmark   June 18, 2012 at 9:31AM
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Den6265

Saltidawg,

"So why does your thermostat even have a Humidity setting- with a Maximum setting of 65%?" That was EXACTLY what I was wondering. What I learned is this: The maximum setting tells the system to go to work - if the maximum setting of 65% were ever reached, it would cause the system to work more to pull the humidity down. By turning the thermostat humidity setting to OFF, I removed simply the maximum setting from the equation. My misconception was in thinking I could set the humidity to 60 or 65% and it would go UP to that level. Not so. And now that I understand just a bit better about the setting and what it's for, I will turn the Humidity setting to ON, and not concern myself about it as long as it's comfortable in here.

And, yes, the temperature was controlled just fine as the humidity went from 45 to 50%. The Carrier Infinity brain controls so much of what goes on, it's hard for mere mortals to know what it's doing and why.

I think the biggest thing I learned is that service techs are trained as sales people, too, (at least where this Carrier Infinity system is concerned) and to question whatever advice they give before purchasing anything. I would have spent more than $1000 on an unnecessary UV system if I had listened to the tech without question. Caveat emptor! Buyer beware!

    Bookmark   June 18, 2012 at 9:37AM
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Den6265

Mike,

Thanks for your knowledgeable reply. Just learned more about the system and what the humidity setting on the thermostat does. Appreciate the help.

    Bookmark   June 18, 2012 at 9:41AM
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saltidawg

Thanks for your un derstanding.

So you'll set the Humidity Control to "On" and, say, 45%?? Lol

    Bookmark   June 18, 2012 at 9:41AM
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Den6265

Saltidawg,

I'll set the humidity control to ON, with the maximum humidity up to say 60%, and let the system do the rest. It's been keeping it in the 45-50% range without my interference! I just wanted to know WHY and HOW, at least to understand it a bit better. Mike's answer helped clarify that for me.

    Bookmark   June 18, 2012 at 9:44AM
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mike_home

Depending on you your climate, but may save some money and be more comfortable by setting he humidity at 50%. I am in NJ where we tend to get summers with temps in the 85-90 degrees with high humidity. I am comfortable with the temperature in the 78-79 degree range and the humidity at 45-50%.

Humidity above 50% could cause mold problems. Don't let the humidity get too high.

    Bookmark   June 18, 2012 at 10:37AM
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Den6265

Mike,

Sound advice. South Florida is high humidity nearly all year. We set the temp at 80 during the day, 76 at night, and the humidity stays in the 45-50% range. Comfortable enough, and no mold issues.

    Bookmark   June 18, 2012 at 1:53PM
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ionized_gw

The UV bulb can't be that hard to replace if you decide to keep the system operating. The lamps themselves are not that expensive and neither are the ballasts. If you are not all thumbs, you should be able to replace them yourself. They can be had at any lighting supplier. If they need to be ordered, get enough to last a few years.

Unless they illuminate a significant portion of the evaporator, I don't see how they can do anything significant.

    Bookmark   June 18, 2012 at 1:53PM
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