Now this makes me feel stupid....RE: Humidity

[teddy bear]

The 27

I'm almost ready to take a bullet over this. Who in the hell has low humidity problems in the middle of a humid summer..and we're living in a swamp.

We were all ready to help you take the bullet to.
I hate to bring this up but prepare your self for high humidity during the shoulder season when the a/c runs very little while the outside dew points are high. As the humidity goes +65%RH you will start growing biologicals, mold/dust mites.
You can change the speed of your fan but because it does not enough, no humidity control.
Best bet is get as the best dehumidifier you can afford, set it at 50%RH, and relax. Also have shown your is home is not getting fresh air. I suggest setting up some kind of fresh air ventilator that will introduce 60-70 cfm of fresh air into your home to purge indoor pollutants and renew oxygen. Or you could get a ventilating dehumidifier. It depends on how good of air quality and comfort you want.
Keep us posted.
Regards TB

[Mighty Hd]

I would love to get the house to 50% and hold it there.

Maybe the next step is a humidifier system ?

I realize the low-load season humidity will be an issue; I'm guessing that's why I was advised to get the prestige thermostat to allow humidification control during the low-load times.

As of now there is a data recorder in the house that they left..we'll see what happens I suppose.

[Mighty Hd]

After a few days humidity at night is up from the upper 20% -->mid 30% to around 45%.

The offset is that the unit is short cycling like crazy at night. On exactly for 5 minutes and off for 6. Starts this about 930pm and continues until around 830am.

My Honeywell prestige HD thermostat arrived yesterday as well. Tech is due to be back out to install the thermostat and view the data recorder.


One thing worth mentioning; we had a heavy rain here earlier this week and it brought the outdoor humidity to 92%. I opened up the windows in the house and turned on the exhaust fans for about 45 minutes. Humidity inside climbed to a peak of 78%. In less than an hour it was down to 45% @ 78 degrees. I give Amana credit, it certainly can remove moisture.

For the record a load calc was done and a 3.0 ton was a perfect fit for the house.


We'll see what next week brings............................... :-(

[dan sw fl]

I hate to bring this up but prepare your self for high humidity during the shoulder season when the a/c runs very little while the outside dew points are high.

As the humidity goes +65%RH you will start growing biologicals, mold/dust mites.
Regards TB

Has someone evaluated the house regarding a CURRENT Mold issue?

[Shophound]

A non-pro thought: wish there were some way to focus on the coil temperature. A colder coil will remove humidity to a lower dewpoint than a less cold coil. I have some Trane documentation telling sensible and latent capacity at various conditions, beyond a certain dryness all the capacity is sensible. If I am not mistaken that corresponds to the coil operating at a temperature above the dew point of the return air.

Actually, pstu, the coil operates below the dew point of the return air. If it operated above, it would not extract moisture from the return air. And even in the OP's case, there's still a latent load on that coil. At a lower blower speed it is doing more latent work...that is why his indoor air is pretty dry.

And this is how you can gain a general idea how cold your coil is running when your system is operation. Measure temperature and humidity in your house and then convert the readings to dew point using a pyschrometric chart or psychrometric calculator online. If your indoor air dew point is 55 degrees or less, your coil surface temperature is running less than 55 degrees. The refrigerant saturated vapor temperature generally runs 10 to 15 degrees below the coil surface temperature.

Trane has a psychrometric chart that accounts for coil bypass factor and where the effective coil temperature can be obtained if the return air and supply air dry and wet bulb temperatures are known. Suffice it to say that measuring indoor dew point can give you a thumbnail glance at how well your a/c is dehumidifying the air.

[jegs]

Cold coil (27 degree delta) + compressor power interrupt (low pressure switch). Sounds to me like it's low on refrigerant.

[Mighty Hd]

Has someone evaluated the house regarding a CURRENT Mold issue?

What mold issue? I never said there was a mold issue and there has not been in the past either?

[Mighty Hd]

Cold coil (27 degree delta) + compressor power interrupt (low pressure switch). Sounds to me like it's low on refrigerant.

He checked the refrigerant as that was his first thought, said it was dead on?

A summary:
1. Fan speed increased to High- unit now short cycles at night. It certainly moves some air through the house; vents sound like a hurricane.
2. Humidity is now 45% steady, occasionally 47% but quickly drops back and holds at 45%.
3. Compressor overheated; suspected cause was a power surge making the compressor run in reverse. A time delay will be installed this upcoming week.
4. Air filter was changed from a MERV 9 media to a cheapo pleated filter.
5. Current thermostat is several degrees off of the indoor temp readings on his gauge and my cheapo humidistat/thermostat.
6. Honeywell prestige HD thermostat ordered and arrived.
7. Data recorder was left in the house next to the thermostat; will record for 7 days.

When the prestige thermostat is installed, he is planning on wiring in several relays to control humidity on the low-load days using the a/c and a lower fan speed. Remember I had the problem with the ultra-high humidity in the house during those times? Now with a heavy load it's the opposite.

45% humidity is very uncomfortable at night for us; dry/cracked sinus and nose in the morning when we get up. It's MUCH better than the 20-30's we were at. I am hoping to get a target of 48%-55%.

My best guess is this:
1. The old Lennox B25 series that I had was installed by a hack job in 1994. It sucked in a LOT of outside unfiltered air through horrible supply duct work. My 8 month old son could have done a better job.
2. The old lennox ran nearly 24/7 in the summer. Fan was on high on this unit as well. Sucking in the humid outside air and running 24/7 kept it comfortable inside at 50-55% humidity all the time.
3. The new Amana unit is a 3-ton and is sized perfectly for the house. It is properly sealed without any unfiltered humid air getting inside.

Maybe other adjustments can be done to the unit, who knows..I certainly don't. Maybe a humidifier added? Or a fresh air intake? Can the temperature of the coil be lowered with an expansion valve adjustment?

Thank you all kindly again for the tips and the things to ask/suggest to the tech. I know this all seriously sounds like I'm smoking crack and it's a line of sh*t, especially in Florida... :-(

[Shophound]

Lowering the temperature of the coil increases humidity removal, the opposite of where you wish to go.

Fresh air intake will cause longer run cycles and may leave your humidity levels about the same, or slightly increase it. It will, however, result in a better purging of indoor air pollutants, which may be contributing to your respiratory ailments.

[dan sw fl]

Actually, pstu, the coil operates below the dew point of the return air.

If your indoor air dew point is 55 degrees or less, your coil surface temperature is running less than 55 degrees.

Suffice it to say that measuring indoor dew point can give you a thumbnail glance at how well your a/c is dehumidifying the air.

Your system is performing well when
air handler differential temperature is > 17'F < 24'F
and Supply Air Dew Point is < 55' F.

......................... DEW POINT
.................. Relative Humidity
Dry
Bulb_ 40%- 45%- 50%- 55%- 60%
72- 46.4 - 49.6 - 52.4 - 55.0 -57.4
73- 47.3 - 50.4 - 53.3 - 56.0 - 58.4
74- 48.2 - 51.4 - 54.3 - 56.9 - 59.3
75- 49.1 - 52.3 - 55.2 -57.8 - 60.2
76- 50.0 - 53.2 - 56.1 - 58.7 - 61.2
77- 50.9 - 54.1 - 57.0 - 59.7 - 62.1
78- 51.8 - 55.0 - 57.9 -60.6 - 63.0
79- 52.7 - 55.9 - 58.8 - 61.5 - 64.0
80- 53.6 - 56.8 - 59.8 - 62.4 - 64.9

x
x

A/C System Summer Performance is suspect when Relative Humidity is consistently > 56%.

x
x

[Mighty Hd]

Still waiting for the tech to return to pick up the data recorder and swap the thermostat.

In the meantime I found a leak and I'm not quite sure if this may contribute to the low humidity?

The AH is in a closet, the closet is essentially a negative pressure "room". The AH sucks air through the return cools and discharges from the top into the duct that runs into the attic.

On one side of the AH that is inaccessible the cool air blowing out has a leak which in theory would recirculate an unknown amount of already cooled air to get cooled again and again.

The blower is setup on high now and the vents throughout the house sound like a hurricane. Airflow is not a problem at all.

With it cooing and re-cooling the leaking air over and over again, is there a possibility that this is contributing to the low humidity?


Also--I have tried leaving the fan on this morning. It has held a steady 40-45% all week, but the unit short cycles at night and is able to hold the temp during the day fine without short cycling. While the fan is on the humidity will go from (for example) 45% to a peak of 58% during the off cycle. The compressor will turn on, cool the house and the humidity is quickly back down to 45% within 10 minutes.

That sure does sound like one hell of a humidity removal ability........

[dan sw fl]

In the meantime I found a leak and I'm not quite sure if this may contribute to the low humidity?

The blower is setup on high now and the vents throughout the house sound like a hurricane. Airflow is not a problem at all.

It has held a steady 40-45% all week ,

but the unit short cycles at night and is able to hold the temp during the day fine without short cycling.

While the fan is on the humidity will go from (for example) 45% to a peak of 58% during the off cycle. The compressor will turn on, cool the house and the humidity is quickly back down to 45% within 10 minutes. ........

______________ 45% = PERFECT
What is the room temperature ? 76'F


It seems like
You have a perfect system
except for the leak.

Low humidity ... consistently < 35%

Short cycling at night -
set CPH to 2 (or 3).

[Mighty Hd]

______________ 45% = PERFECT
What is the room temperature ? 76'F


It seems like
You have a perfect system
except for the leak.

Low humidity ... consistently < 35%

Short cycling at night -
set CPH to 2 (or 3).

That's comforting to know now.
Indoor temp is 78.

What about the short cycling? Is there a way to control it? I was looking at the Honeywell Prestige HD manual and I believe I read something about a delay to start?


Here are my cycle times during the evening hours and one day last weekend when we were home and I was able to make a note of the times.

07/28/10

On: 828
Off: 836

On: 842
Off: 849

07/29/10
on 807
off 816

7/31/10
Off 322p
On 326

On 854
Off 905

On 910
Off 921

On 926
Off 938

8/1/10
On 1pm
Off 110pm

On 118p
Off 135p

On 141p
Off 148p

On 155p
Off 2:07p

On 811pm
Off – 819p

On 825p
Off 833p

On 840
Off 845

On 855
Off 904p

On 910p
Off 918p

On 923p
Off 929p

[dan sw fl]

That's comforting to know now.
Indoor temp is 78.

What about the short cycling? Is there a way to control it? I was looking at the Honeywell Prestige HD manual and I believe I read something about a delay to start?

Here are my cycle times during the evening hours and one day last weekend when we were home and I was able to make a note of the times.

5 to 8 minute cycles is definitely NOT where you want to be operating.

The temperature tolerance may be set too low and the CPH too high.
CPH - Cycles per Hour should be set to 2.

15 minute On- Off cycles would be more beneficial.

http://www.alpinehomeair.com/related...ers_Manual.pdf

[Mighty Hd]

5 to 8 minute cycles is definitely NOT where you want to be operating.

The temperature tolerance may be set too low and the CPH too high.
CPH - Cycles per Hour should be set to 2.

15 minute On- Off cycles would be more beneficial.

http://www.alpinehomeair.com/related...ers_Manual.pdf

I will see what the tech suggests or does and will update.

Thanks for the reply.

[beenthere]

If your current stat uses CPH. You want to set it lower then what it currently is. Looks like its set to 6 cycles per hour. Which is way too many.