The air conditioner is principally for cooling.
It is not uncommon for houses to need a dehumidifier to keep humidity below 60% RH.

Do you have a blower door number for your house? Perhaps you have high infiltration?

 

Haven’t had an official blower door number, but I would say it’s on the moderate side. Newer windows, very well insulated. My hvac and ducting is in the attic though.

My single stage would consistently keep the humidity at or under 50% RH. Now with the new system I’m at 65% RH. Coil is draining well, charges were checked. Everything was triple checked.

There is a ton of settings on the E30 thermostat such as you can put it in comfort or normal cool mode. Normal or max dehumidification mode. Any suggestions?

My thermostat is wired to the dehum terminal of the furnace. You can also add a discharge air sensor to the thermostat. Do you think that would help?

 

I recently had a dual fuel system installed in my home. Lennox ML180V furnace with EL18XPV heat pump. I have been battling high humidity ever since the system was installed. Houston Climate. 4 ton system, replaced a 4 ton single stage.

They have adjusted fan speed to 1050 cfm on first stage and 1460 cfm on second stage with a conventional thermostat. My ac company just installed an E30 thermostat to see if it would help with the high humidity. The outdoor unit is variable and adjusts to cooling load. Could this be causing the problem? It runs in low stage most of the time and I can barely hear the outside unit run most of the time. Any advice or thermostat settings would be very helpful!

Define High! > 55% or 67% or _ _ R.H. ?_?? for Each stage.

AHU : T in - T out = dT. Is dT > 20'F?
T in = 76'F ?
Diffuser Supply Air Temp.: _ _ _ 'F ?

Houston is nowhere close to BEiNG HOUSTON !

https://weather.com/weather/tenday/...anonicalCityId=e7763a6187b4cb5fd0f85ad30c23f37f320bfe7e910e6fdbe90b501f206d265c

 

Duct leakage test?

 

Haven’t had one done. I had the ducts replaced when new system was installed. Maybe I should get that done.

 

High as in 65% RH in the house after the system gets down to 70 degrees. It seems like it removes humidity great in 2nd stage blower speed and high speed on outside unit with a 20 degree drop across the coil. In 1st stage it seems like it is adding humidity gradually. Not sure what the temp drop across the coil is in 1st.

 

I think you put your finger on the problem. You need a 25^F temperature drop across the evaporator to have aggressive humidity control with both stages. This will get your <50%RH during significant cooling loads. During evenings and rainy days with +55^F outdoor dew points and adequate fresh air changes to have a pollutant free home with optimum oxygen levels, plus moister producing occupants, you need +4 lbs. of supplemental dehumidification per hour.

Pass this along to your tech. Measuring air flow is difficult, follow by measuring the coil temperature and the supply temp/%RH/dew point as a final check on air flow. After you decide the temperature and %RH that you want the a/c to maintain, adjust the temp/dew point that the coil supplies at the grill. If want 75^F, 50%RH, a 55^F dew point in the home, target the dew point of the air from the evaporator at a minimum of 5^F lower than the return air from the home. For this condition, go for a <50^F supply dew point. These setting will remove +-3 lbs. of moisture per ton per hour of cooling. Keep in mind, on/off cooling may not remove any moisture.

Evenings and rainy days during the mild seasons of the year will have day time high evening outdoor dew points, yet a healthy home needs an fresh air change in 3-4 hours as per ASHRAE/American Medical Ass. to purge indoor air pollutants and renew oxygen for health and comfort when occupied. Keep in mind that most recommend eliminating fresh air as the first fix for high humidity in a home. Even leaking homes need supplemental fresh filtered air during the mild temps/calm wind seasons.
Always check the a/c supply for a +5^F reduction in dew point after any service or install to assure the a/c's setup/function is correct. It is comparable to taking the pulse of a person for life.

Now we have an a/c that should maintain <50% during significant cooling by removing 3 lbs. of moisture per ton, per hour of sensible cooling, if not now is the time to find where all the extra moisture is coming from. Bring on the blower door and duct testing.

The next challenge is to decide if we want a healthy and comfortable home during calm days, evenings, rainy days, and occupancy. If yes, provide mechanical fresh, filtered air circulated throughout the home with supplemental dehumidification to maintain <50%RH to provide comfort and control of the various biological growths high humidity causes. The most practical method is adequately sized whole house dehumidifier with the filtered fresh air option. Units like the Santa Fe Ultra, Broan, Trane, etc are ideal for this application.

Enough, keep us posted on what you do or additional issues with your contractors.

Regards Teddy Bear

 

It is impossible for an air conditioner to ADD humidity. It simply cannot make water.
Relative humidity may increase, but it is a measurement of moisture relative to temperature.

If you have to cool the house to 70°, I suspect your system is oversized.

 

From what I've seen from watching my psychrometer probes is the supply RH is always higher than the return RH. There's less water in the air, but the air is colder.

But in 1st stage the dehumidification should be higher than in 2nd stage, assuming same coil temp.

I'm not familiar with that heat pump, but the Bosch has dip switches and you can change the target evap temp. One position lets the coil temp vary more (warmer) and the other position keeps it cooler.

 

Have you checked if the blower runs after the thermostat satisfies, i.e. blower running without the A/C running. This can re-evaporate the water that the system has already removed that hasn't drained from the coil yet.

 

Checked that and blower shuts off about 30 seconds after compressor turns off. Would 30 seconds cause a problem?

 

I'm really not a fan of these non communicating inverter setups, which vary compressor speed without varying indoor airflow. It seems to me situations like this are inevitable with them. I believe that your system, on a first stage call, is turning the compressor down much more than indoor airflow is being turned down, leading to a high SHR and this poor dehumidification.

I would normally suggest switching to the communicating iComfort thermostat for full airflow control, which this outdoor unit supports, but unfortunately your furnace is the entry level Merit series and won't support communications.

 

Do you know how the equipment interface modules work with the Lennox communicating system? I read at one point that I might be able to add an equipment interface to my furnace to communicate with the S30 thermostat. Would this control my blower at true variable speed? Right now the furnace really only has two blower options. 1st stage and 2nd stage, but has a variable speed motor for the blower.

 

Tell me if I am wrong, but I took a temperature reading between the return and supply on the unit and I am only seeing a difference of 18 degrees in the 1st stage blower operations which should be like 20 degrees or more for the Houston air. First stage cfm is set for 1050. I set the outside unit to the comfort setting. That seemed to help a bit.

 

Tell me if I am wrong, but I took a temperature reading between the return and supply on the unit and.
I am only seeing a difference of 18 degrees in the 1st stage blower operations
which should be like 20 degrees or more for the Houston air. .

First stage cfm is set for 1050. I set the outside unit to the comfort setting. That seemed to help a bit.

Houston is nowhere close to Being HOUSTON !

https://weather.com/weather/tenday/l...0b501f206d265c

The A/C system needs to operate > 10 hours / Day
to achieve < 56% R.H. at 76'F indoor temperature.
One should not expect > 10 hours/ Day until the highs are consistently > 90'F.

 

If I lived in a area that had humidity I'd have two or three humidifiers installed.

So I could walk into the house on the worst days and have the house comfortable in a very short time.

I live in California. Forest fire smoke, and my wife has allergies in Spring. I have a Trane Clean Effects electronic filter system on my ducted system. Running 4" filters in 3 return airs. Have two Hepa systems ducted into the upstairs and controlled by a separate thermostat. Have another hepa for the downstairs and controlled by a thermostat.

I checked the filter in my mini split a few days ago. It's been installed and running daily for close to a year and a half. Filter wasn't even dirty.

Your home is where you come to get away from all the sh*t life throws at you. It's your sanctuary. Make it comfortable. Quality of life will be better.

Sent from my SM-G998U using Tapatalk

 

If I lived in a area that had humidity I'd have two or three humidifiers installed.

. __________________ ___ ___ ___ ___ ___ TYPO: .... DEhumidifiers