major humidity problem with new home

[pooli0]

We moved into a new home last year and also transferred our AccuClean filter system to the new house nearly a year afterwards. Everything was fine but thought it was the right thing to do. Turns out that as soon as it was installed we experienced humidity levels go from 40% to 70%. I called another company to just put the original Honeywell box back in, hoping that we would be back where we started. Unfortunately that was not the case. 3 weeks later humidity levels are still in high 60's. all I can think is that they must have change the blower speed to accommodate for something with the AccuClean. It's a new house, new everything. I made a horrible decision and need to bail out of it somehow. I took photos of the current blower wiring and also the Owners manual. something looks suspect to me. I feel like the A/C is not running long enough to remove humidity and maybe the blower is wired for the "high" setting. The house still cools but humidity is high. Please help if you can.

[BBeerme]

Something looks hinky. Looks like the yellow is supposed to go to the spare, and the blue is supposed to to to the heat. What happened to the grey wire that is supposed to go to the cool?

[pooli0]

I think the grey wire is the one on the far left that actually looks black. There's an official black wire that is not in the photo but farther down the board.

[BBeerme]

In a 'normal' system, the high speed on the blower is used in cooling, and the low speed on the blower is used in heating.

Can you tell by just listening at the registers what speeds the blower is running when in heat and cool?

It's possible that they want the blower to run on low speed all the time for better air filtration. But you're not going to get any dehumidification without the A/C running or a dedicated de-humidifier. That being said, I have my blower set to run on the low speed for cooling in part for better de-humidification, but if you do that without knowing what you are doing you can cause very expensive problems down the road.

[pooli0]

I haven't tried listening on the heat side since it's warmed up over here in Houston already. On the cool end, it really seems to be a strong flow. If I had to guess, I'd say that the blower is running on high for cool. This is a carrier unit probably within 2 years old.

[BBeerme]

It is 'normal' for the blower to be on high speed when in cooling, but here is one of the most common reasons for an A/C to not dehumidify properly:

An over sized system.

You want long run times to continually suck the moisture out of the air. An over sized system will satisfy the thermostat quickly and shut off. Which means no more dehumidification can take place.

I haven't tried listening on the heat side since it's warmed up over here in Houston already. On the cool end, it really seems to be a strong flow. If I had to guess, I'd say that the blower is running on high for cool. This is a carrier unit probably within 2 years old.

[jtrammel]

The blower is on medium speed for cooling which should help dehumidify better than if it was in factory high speed. It should have been commissioned on install and set to the proper speed to achieve the CFM your outdoor unit needs to work properly.

New houses take a while for all the building materials to off gas and dry out. Do you have any fresh air ventilation to help with this?

I'd say it has nothing to do with changing the filter box and everything to do with low sensible cooling load with high outdoor dew points. Having an oversized ac doesn't help this problem but even a correctly sized ac won't fix the problem since there is little to know cooling load.

The best remedy is a stand alone whole house ventilating dehumidifier.

[pooli0]

The house is just over a year old. It was at the perfect humidity level prior to the AccuClean filter system being put in. Once we saw the humidity skyrocket and realized that the AccuClean may not be the right specs for this home, I had another company remove the AccuClean and put the original Honeywell filter back in. But not we can't get the humidity under 60%. I've thrown some cash in the trash for sure. I mentioned a whole-home dehumidifier and my wife is like "but it was fine before we screwed with it". Not good for me!

[BBeerme]

Yeah, never good when the wifey isn't pleased.

Think I've seen comments on this forum stating that Texas was going through some heat / humidity.

When the humidity was okay in the house, how was it outside compared to now?

How long does your outdoor unit run? Time on and amount of time off?

The house is just over a year old. It was at the perfect humidity level prior to the AccuClean filter system being put in. Once we saw the humidity skyrocket and realized that the AccuClean may not be the right specs for this home, I had another company remove the AccuClean and put the original Honeywell filter back in. But not we can't get the humidity under 60%. I've thrown some cash in the trash for sure. I mentioned a whole-home dehumidifier and my wife is like "but it was fine before we screwed with it". Not good for me!

[pooli0]

I'll start timing the run times. there were no issues all last summer with indoor humidity. Houston is always 100% humidity during the summer months and we didn't see any issues inside the new home. We're positive that whatever they did to try and get that AccuClean installed most likely messed something up along the way. Going back to the original filter didn't reverse the situation. It's been about 4 weeks now and we're stuck at 60 + humidity still.
I need to figure out if those wires are where they're supposed to be. I feel like that AC crew did something in that area.

[VTP99]

Did I here someone say "switch it to high speed and see what happens" ?

[BaldLoonie]

The comments that it should be on high for cool are dead wrong. A GOOD tech would take a static pressure reading and use the blower performance chart that came with the unit to set the CFM for no more than 400 CFM per ton. If you want more dehumidification, you want 350 CFM per ton. That looks like an X13 motor so there are 4 speeds plus constant fan on low. Someone should set the blower speeds correctly and see what happens. Do NOT run the blower constantly.

[pooli0]

I appreciate everyone's input here. I'm going to pass this along to our local A/C technician. This A/C guy is working with our home warranty so hopefully they'll compare the wiring in my home with the wiring that they do for the other homes around us. they came out last week but didn't find anything (they didn't check blower speeds).

[teddy bear]

The comments that it should be on high for cool are dead wrong. A GOOD tech would take a static pressure reading and use the blower performance chart that came with the unit to set the CFM for no more than 400 CFM per ton. If you want more dehumidification, you want 350 CFM per ton. That looks like an X13 motor so there are 4 speeds plus constant fan on low. Someone should set the blower speeds correctly and see what happens. Do NOT run the blower constantly.

This is good advice. You need an a/c coil temperature about 30^F below the return air temperature, the temperature in the home. 75^F, 50%RH, which is a 55^F dew point. When the outdoor dew point is +60^F, nothing to de with outdoor %RH, you need dehumidification in the home. First a cold coil a/c, next extended sensible cooling load. Like 4-6 hours per day to remove 4-8 lbs. per hour of moisture removal per hour.
The fan should be in the "auto" mode.
During hours of low/no sensible cooling and high outdoor point, supplemental dehumidification will be needed. In addition when the space is occupied, add 1-3 lbs. of moisture load.
If you want good air indoor air quality, you need a fresh air change in 4-5 hours when the home is occupied.
During cool damp weather, conventional a/c is unable to remove moisture without over cooling the home. Overcooling the home results in higher indoor %RH and the need for additional supplemental dehumidification.
At the extreme over-cooling leads to mold growing on the damp cold side the drywall and on the damp side of ducts. Sensitive occupants will affected.
You would do better to allow the home to warm when unoccupied which allows the condensation evaporates and dryout the materials. This interrupts mold growth.
A properly setup a/c will dryout the home during a 1-2 cool down.
Finally, to deal with wet cool weather, you will need an adequately sized whole house dehumidifier to get you <50%RH during low/no sensible cooling loads and high outdoor dew points.
You had a record rainy period in TX. The homes with a ideal setup a/c and whole house dehumidifiers maintain 50%RH during all of this.
You can not count of weather.
Keep us posted. Ma be hot dry weather will returns to TX. Watch the outdoor dew point, not the %RH.
Regards Teddy Bear

[pooli0]

This setting did the trick. I think it disables outside air from entering. Ventilation Type=NONE

[Brian8383]

Did they set the fan to run continually thinking that more airflow over the filter is better? This will raise the humidity level in the house.

Or, did they do a good job sealing the ductwork when they swapped out the filter assembly. Is it possible there is an air leak pulling humid air from wherever the air handler is?

[teddy bear]

Fresh air is way over rated. Indoor pollutants are not that bad, right. During calm weather natural infiltration declines, pollutants build, and oxygen declines. This fan "on" verses fan "off" is a biggy.
Seriously, during peak cooling loads, an a/c with correct blower speed will remove remove the moisture from occupants and adequate fresh air ventilation. Measure the supply air temperature/%RH, calculate the dew point, should be 5^F below what you want in the space. 75^F, 50%RH, is a 55^F dew point. The a/c supply should be <50^F to maintain 50%RH..
When you home is occupied, a fresh air change in 4-5 is a must if you value your health, long term.
When the sun goes down or on a rainy day, the a/c does not run much. Therefore no moisture removal, therefore no humidity control.
If the dew points outside are plus 60^F, you are breathing, how do any of you expect to maintain low %RH.
Am I missing something?
Keep posted on how humidity control can work when a/c loads are low and outdoor dew points are high for a couple days.
Regards Teddy Bear