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Lennox XL20 has 85% humidity coming out of vent when compressor is on

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Chris_deepfrees

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Discussion starter · #1 ·
Hello, I’m new,

We recently bought a new Lennox 20 seer variable speed and it was installed with new ductwork which is all airtight and on the intake the relative humidity is 60% and in output vent relative humidity is 85%. The whole house humidity is usually over 60% and that is with a separate dehumidifier running at all times. It’s a 2 1/2 ton unit in a 1600sq ft house with a crawl space. My last ac kept whole house humidity at about 35% with no dehumidifier necessary. 85% humidity coming out of the vent seems high and we are very disappointed. Does anyone know if this high humidity coming out of the new ac vent is normal?
 
Discussion starter · #6 ·
Return rh is 62% which is about the same as the whole house rh. Not sure how I’m supposed to reply here but would like to know if something can be done to get the unit to dehumidify my house down to at least 50%
 
#7 ·
What size was the equipment that was replaced was it also two and a half ton?. Also are you measuring relative humidity in the same location, with the same sensor as you used to.
Pretty sure 35%rh would not be attainable in summer so I think maybe the instrument readings aren't accurate.

Sent from my SM-G950U using Tapatalk
 
Discussion starter · #8 ·
I’m sure you’re right, I only checked it once a couple years ago. Nevertheless, my paint is coming off the walls around the vents since I got the new unit installed and my shoes and clothes have mold growing on them which never happened before. I should note that the humidity was even higher for a while, over 70% till the installer figured out the condensate was running up into the plenum. After that was corrected the humidity went down to around 60%, it’s 66% right now and it’s 75% humidity outside now. Does anyone know what a reasonable rh inside should be?
 
#9 ·
Chris_deepfrees said:
Return rh is 62% which is about the same as the whole house rh. Not sure how I’m supposed to reply here but would like to know if something can be done to get the unit to dehumidify my house down to at least 50%
Click to expand...
A properly sized unit hooked up to proper duct system will do it. That rarely happens, usually the equipment is oversized and the ducts are undersized.

If your in a warm humid climate a whole house dehumidifier bringing in outside air makes a huge difference.
 
Discussion starter · #10 · (Edited by Moderator)
pecmsg said:
A properly sized unit hooked up to proper duct system will do it. That rarely happens, usually the equipment is oversized and the ducts are undersized.

If your in a warm humid climate a whole house dehumidifier bringing in outside air makes a huge difference.
Click to expand...
I definitely know I can spend more money on dehumidifiers and have a more expensive electric bill. One of the reasons I bought a new high seer Hvac system was so I could save money on my electric bill and pay for the unit over time. Now I feel like a fool because my house is constantly humid. My old system dehumidified my house just fine. Never had any problems with it. Now I have mold growing all over the place and none of my doors will close and paint is peeling off my walls in front of all my vents. Had to grind away at my front door today just so I could open it again. It’s hard to accept that after spending $xx,xxx on this HVAC system that I’m going to have to buy more equipment just so my electric bill will be the same or more that it was before. Are these new high seer systems just not as good at dehumidifying as old Freon systems?
 
#11 ·
Chris_deepfrees said:
I definitely know I can spend more money on dehumidifiers and have a more expensive electric bill. One of the reasons I bought a new high seer Hvac system was so I could save money on my electric bill and pay for the unit over time. Now I feel like a fool because my house is constantly humid. My old system dehumidified my house just fine. Never had any problems with it. Now I have mold growing all over the place and none of my doors will close and paint is peeling off my walls in front of all my vents. Had to grind away at my front door today just so I could open it again. It’s hard to accept that after spending $****** on this HVAC system that I’m going to have to buy more equipment just so my electric bill will be the same or more that it was before. Are these new high seer systems just not as good at dehumidifying as old Freon systems?
Click to expand...
If you want to save money on electric tighten the envelope.

How was the system sized, like for like?
Was a full start up and commissioning performed? (Doubtful)

Get the contractor back and tell them your not satisfied with the performance of the new system.
 
#13 ·
85 percent is actually a little low.
Should be more like 90.
Your getting fooled by the relative part, of relative humidity.

This has been asked a few times, and I'll repeat it.

How was the unit sized?
How was it started and commissioned?

Blower speeds checked?
Refrigerant checked?
 
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Discussion starter · #14 ·
hvacvegas said:
85 percent is actually a little low.
Should be more like 90.
Your getting fooled by the relative part, of relative humidity.

This has been asked a few times, and I'll repeat it.

How was the unit sized?
How was it started and commissioned?

Blower speeds checked?
Refrigerant checked?
Click to expand...
The unit was sized like for like, yes the refrigerant was checked, don’t know about the blower speed, but the contractor(a very large company) has been out many times trying to fix the issue to limited success and they have gone over the system several times. Don’t know what you mean when you ask how was it started and commissioned? I can say that the system blows a lot harder than the old Freon system we had before. I kind of think the paint wouldn’t have peeled off the walls so bad if it didn’t blow so hard.
 
Discussion starter · #16 ·
Chris_deepfrees said:
The unit was sized like for like, yes the refrigerant was checked, don’t know about the blower speed, but the contractor(a very large company) has been out many times trying to fix the issue to limited success and they have gone over the system several times. Don’t know what you mean when you ask how was it started and commissioned? I can say that the system blows a lot harder than the old Freon system we had before. I kind of think the paint wouldn’t have peeled off the walls so bad if it didn’t blow so hard.
Click to expand...
I don’t know if they checked the blower speed.
 
#18 · (Edited)
Perfectly normal to have high humidity from supply vents, but vents must also have proper throw or face velocity. You could have the blower speed raised to reduce supply temperature Δ.
This is another reason why I question variable speed blowers. Air speed can get too low in attempts to dehumidify.
 
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#19 ·
It definitely sounds like the system was not commissioned properly and that you're moving too much air. That will cause the system to not dehumidify properly.

Generally speaking, the largest companies have the poorest technicians and do the shoddiest work. Not always, but far too often.

If a commission report had been done and properly filled out, the data would point to the problem. It's like a startup diagnosis.
 
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#20 ·
I don't see an "XL"20 in Lennox's product offerings. I see an "XC" and an "XP" which is a heat pump. Either way, they only come in 2, 3, 4, and 5 ton. This is true with every manufacturer of variable speed units that I know of. So, unless I'm missing something, you don't have a 2.5 ton, probably its a 3 ton.

This adds to the confusion when the people who sold it to you and installed it don't even know what size it is.

The airflow can be adjusted for 2.5 tons and the unit will modulate down to match it.

Since I'm not a Lennox dealer, I don't know all the adjustments or programing required.
 
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