Author Topic: HVAC - humidity issue  (Read 501 times)

secondcor521

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HVAC - humidity issue
« on: August 13, 2019, 11:12:46 AM »
Hi all.

I have a 15 year old house with the original HVAC unit.  I don't have anyone check it annually, but I do regularly change the filter.

As is typical around here, the AC unit is outside near the garage, and the furnace/blower part is in the garage.

This summer has been a typically hot Idaho summer.  Maybe a bit more humid outside than usual.

The AC has been able to keep the temperature cooled per the thermostat setting.  But the last few weeks, the air inside my house has been more humid than normal.

Before the last few weeks, the AC unit has been working just fine for the past 12 years I've lived here.

A google check suggests that the most likely cause is that the coils are dirty or that the lines have leaks.

Questions:

1.  Any other likely causes?

2.  Can I clean the coils myself, and if so how? [ETA:  Nevermind, I can Youtube/Google this pretty well it appears.]

3.  How much would it cost to have someone come out and check this out and fix it if it's the lines?

4.  Does the humidity problem at all imply the need for a new AC unit or that the existing unit is failing (vs. just needing maintenance)?

Thanks for any advice.
« Last Edit: August 13, 2019, 11:22:25 AM by secondcor521 »

Jon Bon

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Re: HVAC - humidity issue
« Reply #1 on: August 13, 2019, 12:01:18 PM »
You probably have a leak, it happens. I assume wtih the hunidity the AC has not been keeping the temp down as well?

1. It could be frozen up, but you would notice the ice on your coils. Could be something in the coils or condensor. But your best bet is a small leak somewhere in terms of cost

2. Sure, its not hard

3. The check should be cheap. <100, but he is probably gonna be like well your AC is empty, so I gotta add 6 pounds at $50 a pound. So $100 for the call, $150 to fix the leak (if small) and $300 to fill it up. Or something like that. There are 2 types of refrigerant. R-22 (expensive and old) and r-410 your outside unit should have a sticker saying which. Sometimes the leak is in the coil itself so it has to be replaced ($500 or so on top)

4. Probably not, just a leak.

Age of your unit is probably getting up there. Id put it at >$500 is the replacement line. A new AC unit and coil should be about 3k where I am. Get a few quotes or better yet find someone with rental properties and ask them who they use.  Im not an HVAC guy, but I own lots of them and they break all the time. Needless to say I got a good guy who works on my AC's and I am probably funding his kids college.


secondcor521

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Re: HVAC - humidity issue
« Reply #2 on: August 13, 2019, 12:29:26 PM »
Thanks, @Jon Bon.

It has been keeping the temperature down successfully.  So I don't think it's iced up but I haven't looked.

Of course, 74 and mildly humid isn't as comfortable as 74 and low humidity, but again, it is maintaining temperature.

The outside unit is a Carrier "High Efficiency" unit using R410A and POE oil, whatever that is.  It would have been installed in 2004.

I did find where my condenser coils are, FWIW.

Jon Bon

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Re: HVAC - humidity issue
« Reply #3 on: August 13, 2019, 01:29:58 PM »
Huh, that is strange then. I am no expert on thermodynamics and all. But if the temp is down the humidity MUST be down too. Your AC really cools down the air (like COLD over the coils) and cold air CANT hold moisture like hot air can. So if its keeping it cool, you must be getting humidity from somewhere else?

I guess its possible you have a leak, and its cooling the air down to say 65 degrees on the coil rather then 45 degrees at the coil. Its able to cool the house down but does not remove enough heat to remove all the moisture?

Yeah coil is suppose to be down about 40 degrees according to google.

Have someone look at it, im just speculating.


Adam Zapple

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Re: HVAC - humidity issue
« Reply #4 on: August 13, 2019, 01:52:22 PM »
I don't know jack about HVAC but this just happened to me and my condensation line was just clogged up and not flowing properly.

secondcor521

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Re: HVAC - humidity issue
« Reply #5 on: August 13, 2019, 03:17:20 PM »
Thanks, both of you.

To expound a little further:  Before a few weeks ago, the AC could cool the house to 74 degrees F and pretty much 0% humidity.  Now it cools it to 74 degrees F but more like 15-20% humidity (just guessing).

I'm going to take a look at the condensation line also.

Wrenchturner

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Re: HVAC - humidity issue
« Reply #6 on: August 13, 2019, 04:13:48 PM »
Clean the evaporator fins, check the condensation drain line.  You should have a 10f difference(at least) between intake and output air temp.

If your a.c. is simply running less frequently that will allow humidity to climb as well.

Run it for a while manually, then check on it and see if you're getting ice up or condensation build up.

secondcor521

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Re: HVAC - humidity issue
« Reply #7 on: August 13, 2019, 04:16:07 PM »
Clean the evaporator fins, check the condensation drain line.  You should have a 10f difference(at least) between intake and output air temp.

If your a.c. is simply running less frequently that will allow humidity to climb as well.

Run it for a while manually, then check on it and see if you're getting ice up or condensation build up.

What should I use to clean the evaporator fins with?

geekette

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Re: HVAC - humidity issue
« Reply #8 on: August 13, 2019, 05:32:51 PM »
We live in the hot, humid south.  45-50% indoor humidity in the summer is about as good as it gets here (but we only cool to 78). 

The more your a/c runs, the more water it can remove.  If your weather has been cooler lately, or you're cooking more, or taking more showers, then that will mean higher indoor humidity.

secondcor521

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Re: HVAC - humidity issue
« Reply #9 on: August 13, 2019, 06:26:23 PM »
We live in the hot, humid south.  45-50% indoor humidity in the summer is about as good as it gets here (but we only cool to 78). 

The more your a/c runs, the more water it can remove.  If your weather has been cooler lately, or you're cooking more, or taking more showers, then that will mean higher indoor humidity.

It's pretty dry and hot up here.  We haven't really had any changes in our routines, and, as I mentioned, it's been a typical hot summer here and the AC has been running regularly every afternoon into the evening.  It probably runs 4-6 hours per day.

The only thing that I can think of that might be different that way is that it has been a more humid summer weather-wise.  Maybe that has some sort of effect.

Papa bear

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Re: HVAC - humidity issue
« Reply #10 on: August 13, 2019, 07:44:54 PM »
Do you leave the fan on or on auto?

Keep it on auto.  Apparently, if you keep the fan running constantly, you donít allow all the water to drip off and you start recirculating the moisture back in. 




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secondcor521

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Re: HVAC - humidity issue
« Reply #11 on: August 13, 2019, 08:22:26 PM »
Do you leave the fan on or on auto?

Keep it on auto.  Apparently, if you keep the fan running constantly, you donít allow all the water to drip off and you start recirculating the moisture back in. 

Sent from my iPhone using Tapatalk

Right, I had read that also.

We vary between fan and auto depending on time of day and who is home.  Probably on Auto more than Fan.

I'm not sure if we've changed our behavior relative to that setting in the past couple of weeks, but I'll have to think about it more.

BudgetSlasher

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Re: HVAC - humidity issue
« Reply #12 on: August 14, 2019, 05:40:30 AM »

This summer has been a typically hot Idaho summer.  Maybe a bit more humid outside than usual.

The AC has been able to keep the temperature cooled per the thermostat setting.  But the last few weeks, the air inside my house has been more humid than normal.

Before the last few weeks, the AC unit has been working just fine for the past 12 years I've lived here.

Questions:

1.  Any other likely causes?


With any system that suddenly changes in performance I recommend making sure there is nothing wrong and performing basic maintenance and inspections; which you seem to have been advised to do already.

But, I want to offer a different perspective. The increased outdoor humidity without an increase in temperature is allowing more moisture into your house than your A/C can remove at it current settings.

Dehumidification is a byproduct of cooling with an A/C, the longer the A/C runs the more moisture it will remove. (A significantly oversized A/C will remove less moisture than a correctly sized or likely even an undersized unit). It is possible that the extra humidity outside (that finds its way inside by various means) is simply more than you A/C can remove, given that it is running the same amount of time to cool (same temperature as last year and I assume you haven't set it cooler) your house.

This is a problem we encountered, especially in the spring and fall where little to no A/C is actually needed, but the humidity can spike into "is that mold?" territory. Our ultimate solution after a few years in a row of extra humidity summers was to add a central dehumidifier. We find it has done 2 things; one, it is take the humidity out of the air during the times when the A/C runs only a-little-to-none-of-the-time, and two we find the reduced humidity comfortable enough that we use less A/C (both in terms period of time it is turned on and temperature it is set to when it is running).


Wrenchturner

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Re: HVAC - humidity issue
« Reply #13 on: August 14, 2019, 06:35:31 AM »
Clean the evaporator fins, check the condensation drain line.  You should have a 10f difference(at least) between intake and output air temp.

If your a.c. is simply running less frequently that will allow humidity to climb as well.

Run it for a while manually, then check on it and see if you're getting ice up or condensation build up.

What should I use to clean the evaporator fins with?
Just vacuum them, they shouldn't be really dirty, just possibly obstructed. 

BTDretire

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Re: HVAC - humidity issue
« Reply #14 on: August 14, 2019, 08:41:06 AM »
We live in the hot, humid south.  45-50% indoor humidity in the summer is about as good as it gets here (but we only cool to 78). 

The more your a/c runs, the more water it can remove.  If your weather has been cooler lately, or you're cooking more, or taking more showers, then that will mean higher indoor humidity.

 No kidding, what we would do for 15% to 20% humidity!
Mine runs around 41% on a hot day when the air conditioner is running a lot. Right now in the morning the humidity is 48% temp is set at 78*. We cleaned the carpet 3 days ago, I think they are dry, but could be a little extra moisture coming out of the carpet still. I looked shortly after cleaning the carpet and the humidity was up to 52% at 78*.
 With my old air conditioner (it did not DEhumidify as well) I occasionally ran a dehumidifier, it would get the humidity low enough (below 40% that I was still comfortable at 81* or 82*.
 Then I got a recall on my dehumidifier that it was a fire hazard. :-(
They paid me $75 to cut off the power cord and send it to them.

BTDretire

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Re: HVAC - humidity issue
« Reply #15 on: August 14, 2019, 08:48:29 AM »
Clean the evaporator fins, check the condensation drain line.  You should have a 10f difference(at least) between intake and output air temp.

If your a.c. is simply running less frequently that will allow humidity to climb as well.

Run it for a while manually, then check on it and see if you're getting ice up or condensation build up.

What should I use to clean the evaporator fins with?
Just vacuum them, they shouldn't be really dirty, just possibly obstructed.
Usually they need more than vacuuming, they get a scale buildup. Go to a heat/air supply store and get a bottle of coil cleaner. Be delicate, you don't want to bend the fins, which would block air flow.
 Note: It can be difficult to get to the coils on some units.
 On my unit, the filter is on the bottom, I remove that, put something under to catch the drippings and spray the coil cleaner.

geekette

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Re: HVAC - humidity issue
« Reply #16 on: August 14, 2019, 08:55:54 AM »
We live in the hot, humid south.  45-50% indoor humidity in the summer is about as good as it gets here (but we only cool to 78). 

The more your a/c runs, the more water it can remove.  If your weather has been cooler lately, or you're cooking more, or taking more showers, then that will mean higher indoor humidity.

 No kidding, what we would do for 15% to 20% humidity!
Mine runs around 41% on a hot day when the air conditioner is running a lot. Right now in the morning the humidity is 48% temp is set at 78*. We cleaned the carpet 3 days ago, I think they are dry, but could be a little extra moisture coming out of the carpet still. I looked shortly after cleaning the carpet and the humidity was up to 52% at 78*.
 With my old air conditioner (it did not DEhumidify as well) I occasionally ran a dehumidifier, it would get the humidity low enough (below 40% that I was still comfortable at 81* or 82*.
 Then I got a recall on my dehumidifier that it was a fire hazard. :-(
They paid me $75 to cut off the power cord and send it to them.
From what (little) I understand about dehumidifiers, they cool the air to remove the water, then warm it back up again as it's blown out.  Good for cold, damp basements, but not the best choice for summer in the south.

We paid a (non-mustachian) bit more to have a thermostat with an integrated humidistat.  We set the maximums at 78 degrees and 50% humidity.  If either goes over, it calls for a/c.  On extremely muggy days, it will run it down as far as 76 degrees to reduce the humidity.

The cheaper version of that would be to do a temporary decrease in temp on the thermostat on muggy days.

BTDretire

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Re: HVAC - humidity issue
« Reply #17 on: August 14, 2019, 09:28:12 AM »
We live in the hot, humid south.  45-50% indoor humidity in the summer is about as good as it gets here (but we only cool to 78). 

The more your a/c runs, the more water it can remove.  If your weather has been cooler lately, or you're cooking more, or taking more showers, then that will mean higher indoor humidity.

 No kidding, what we would do for 15% to 20% humidity!
Mine runs around 41% on a hot day when the air conditioner is running a lot. Right now in the morning the humidity is 48% temp is set at 78*. We cleaned the carpet 3 days ago, I think they are dry, but could be a little extra moisture coming out of the carpet still. I looked shortly after cleaning the carpet and the humidity was up to 52% at 78*.
 With my old air conditioner (it did not DEhumidify as well) I occasionally ran a dehumidifier, it would get the humidity low enough (below 40% that I was still comfortable at 81* or 82*.
 Then I got a recall on my dehumidifier that it was a fire hazard. :-(
They paid me $75 to cut off the power cord and send it to them.
From what (little) I understand about dehumidifiers, they cool the air to remove the water, then warm it back up again as it's blown out.  Good for cold, damp basements, but not the best choice for summer in the south.
I wasn't sure about the rewarming of the output air, but that is how they are set up. But even if it didn't rewarm the output air, you still have the heat that is taken out of the evaporator and moved to the condensor. So, yes all dehumidifiers will heat the air in the room it is in. It might seem to be an adiabatic process, but the motor created heat and the water in the container has heat removed that goes into the room.
  The excess heat is the reason the dehumidifier fell out of favor in my home, the hallway we put it in became very warm. If that heat could have been exhausted to the outside, that would have been great.
Quote
We paid a (non-mustachian) bit more to have a thermostat with an integrated humidistat.  We set the maximums at 78 degrees and 50% humidity.  If either goes over, it calls for a/c.  On extremely muggy days, it will run it down as far as 76 degrees to reduce the humidity.
I would like that very much, it would drive my wife nuts, she would see the temp at 76* and say we need to fix that., she would be turning up the thermostat.
Quote
The cheaper version of that would be to do a temporary decrease in temp on the thermostat on muggy days.

secondcor521

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Re: HVAC - humidity issue
« Reply #18 on: August 14, 2019, 09:49:10 AM »
We cleaned the carpet 3 days ago, I think they are dry, but could be a little extra moisture coming out of the carpet still. I looked shortly after cleaning the carpet and the humidity was up to 52% at 78*.

This could be another piece of the puzzle.  In fact, it could be all of the puzzle.

I did have the carpets cleaned a few weeks ago, and now that I think about it, the indoor humidity wasn't as bad before that time and has been bad since that time.

I knew it would increase humidity for a while, but I *assumed* it would just be for a few days.  I suppose it could last longer.

Will also clean the fins soon.

Jon Bon

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Re: HVAC - humidity issue
« Reply #19 on: August 14, 2019, 01:43:00 PM »
Lol yeah, like 50 gallons of water spread throughout your house might have something to do with it!

IME AC is usually 1 or 0, working or broken. So if yours is still keeping the house cool you are probably in good shape.

There are some things you can do for efficiency mentioned above and it sound sliek you are on top of those. One I will mention is make sure your lines are well insulated. Especially outside. If your refrigerant line has a bunch of condensation on it that is hurting your efficiency.


secondcor521

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Re: HVAC - humidity issue
« Reply #20 on: August 14, 2019, 02:11:30 PM »
Lol yeah, like 50 gallons of water spread throughout your house might have something to do with it!

IME AC is usually 1 or 0, working or broken. So if yours is still keeping the house cool you are probably in good shape.

There are some things you can do for efficiency mentioned above and it sound sliek you are on top of those. One I will mention is make sure your lines are well insulated. Especially outside. If your refrigerant line has a bunch of condensation on it that is hurting your efficiency.

Heh.

The refrigerant lines are insulated.  From all I can tell I had a decent builder, although one or two of his subs made some mistakes here and there that I'm finding out about as I learn to maintain my home.  Not big deals in the scheme of things.

Thanks.