The original author stated he is experiencing humidity problems in other areas since the new AC was installed. I am trying to help find a possible source of the problem. Once the root cause is identified then the possible solutions can be proposed.

Ray you often state the humidity is about 40% in your house. I think Katy Texas often has high outdoor humidity. Do you accomplish this humidity control solely by cooling with your heat pump or have you installed a dehumidifier?

Same sized AC unit, 5 ton heat pump.

Have you noticed a change in run times? Does the AC cycle on and off for short intervals? What temperature do you set the thermostat and do you measure the indoor humidity?

Currently my Nest app says AC has been running 24hrs a day lately. I attached a chart of power use during the day. Humidity says between 40 and 50 usually. It’s hit in the high 60s at some times.

The AC is running continously even when the sun goes down?

Do you need to look at an app to know that your AC is running?

Mike - yes, 24 hours lately.

Elmer - at times. The new unit is so quiet we don’t hear it.

Temp is set to 70. It won’t hit that (or close to it, maybe 72) until morning when things start boiling again outside. One downstairs room will get there at times. Remote sensor is used in upstairs bedroom so it’s comfortable to sleep.

Hi, Dave,

You may have unrealistic expectations for your air conditioning system. The minimum indoor design temperature for air conditioning systems per the 2018 International Energy Conservation Code is 75F. A rule of thumb is that your air conditioning system should be able to maintain an indoor temperature 20 F lower than the outdoor temperature. You might get a differential of as much as 25F, but I think that's all you should expect from an air-source heat pump or air conditioner. If it's 100F outside, your system should maintain indoor conditions at 80F +/-

Getting back to the water heater - when you have the problem with the heater, is there condensed water on the inside of the cabinet?

Here's the thing: It sounds to me like you have extraordinary humidity outside, a cool unit inside, short vent runs and then the combustion air vents inside the cabinet. It's a perfect storm of issues that cause condensation inside the unit.

The Rheem units work well, but venting combustion air intake inside the cabinet does seem to be a design issue in this situation.

Possible solutions:

1. A different water heater that doesn't vent combustion air into the cabinet.
2. longer vents (I suspect that the condensation happens even while the unit is off because the vents are short)
3. Raising the temp of the heater cabinet so that it's not so cool. This might mean closing off the AC vent to the utility room, for example.

All correct. I’ve considered running a vent into the garage. It’s got an exhaust fan in it for heat and humidity but it’s not a “tight” room. Also have considered boxing in the water heater so it doesn’t cool as much.
It’s in the laundry, dog and hobby room so we want to keep the area conditioned.
I’ll probably move the intake vent. During a (hopefully) rare hurricane, water gets blown into the intake and similarly shuts down the unit, even though the air is somewhat baffled on the way in.

You really shouldn't have to do anything to get an expensive tankless hot water heater to work properly when installed in your home and out of the elements. I don't think you'd have an issue if the combustion air were ducted directly to the blower instead of being allowed to find its way there as it tours the inside of the heater enclosure.

I suggest you get Rheem involved. They ought to do something to help; it's a design issue. If you can move the entire heater into the garage, that should remedy the problem. If that's viable, you might get Rheem to pay for the cost to relocate it.

Charles Ross Homes:

Indeed, it should work and he shouldn't have to do anything... but here we are.

They may or may not offer a fix - even if they "should".

I do think it's a perfect storm of issues that came together to make that design problematic.

It could potentially help to draw the air from the garage if it extends the air intake. I think that the short intake is contributing to the condensation problem. Of course you don't want to vent the exhaust into the garage.

The fix is either to 1.) increase the temperature of the environment in which the heater is located so that it is always above the dewpoint of the combustion air or 2.) to reduce the dewpoint of the combustion air entering the heater to a temperature less than the indoor environment. If the heater is relocated so the temperature of the environment is close to the temperature of the outdoor air (e.g., locate it in an unconditioned garage,) that will do the trick.

If the installation instructions don't restrict the environment in which the heater is installed, I'd lean pretty heavily on Rheem to make it right.

Ray you often state the humidity is about 40% in your house. I think Katy Texas often has high outdoor humidity. Do you accomplish this humidity control solely by cooling with your heat pump or have you installed a dehumidifier?

I have often given ranges of what the humidity level is in my office. I've seen anywhere from around 49% recently to 36% this morning with a recent high of 39% -- these numbers tell you what about "control"?

To me those numbers don't demonstrate control... those number are the direct result of how I run a Bosch Inverter AC. (not your father's air conditioner)

"control" is where you buy a dehumidifier "properly" sized and you control it from a dehumidistat. An air conditioner will not do what a dehumidifier does. An air conditioner is predominantly geared to dropping temperature. But a dehumidifier is more cost, cost further more to run it, more to repair it, more to replace it.

Why I chose the Bosch Inverter AC. (my light bill went down, along with humidity levels -- that doesn't mean "control" though.) I'm a control freak, so I think I'd know what control is or was.

Thermostat humidity control (via an air conditioner) is limited to a 3-5F temperature band *typically* (this does little to nothing for a climate with elevated humidity) --- again this comes from 'knowing' controls and what they do (as well as what they don't do)... not just yacking by those who can't be bothered with purchasing refrigerants or those home owners like mike_home who live in mild climates with really short summer AC season with too much time on their hands.

People love to chase gimmicks, just as much chase their tails listening to people on the internet that think they know what they are saying 'without doing anything to prove it.' Talk is cheap, words on the internet are a bargain.

Questions for key board warriors to ask Themselves: If thermostat humidity controls with a 3-5F temperature limitation dehumidify band and some tomfoolery of slowing blower speeds is or was enough to dehumidify for my climate of Katy, Texas??

Why oh why then did I install the Bosch Inverter AC for more money?

1. I knew it would cut operational costs. (upto 50% compared to previous 14 SEER single speed AC)

2. I knew it would drop humidity as a function of how it runs. (he's a stallion.)

3. over 50 compressor speeds vs 1 or 2? It's not even a race ok?

*control* is what triggered me on this thread -- call it a fact check if you want. I am not here to argue that an air conditioner will or won't provide *some* dehumidification. An Air conditioner's primary job is to drop temperature. DESIGN -- all day everyday.

I'm in homes all summer long with poor HVAC designs built by builders who "thought" they knew air conditioning. --The builders aren't coming back.

I service the Katy, Texas area.

Homebuilders are responsible for the performance of homes they build, but blaming a poorly-performing HVAC system on a homebuilder is like blaming the builder for a poorly-performing electrical system or a poorly-performing plumbing system. Those are designed and installed by specialty contractors. If the builder specifically directs the specialty contractor to do something they know to not meet that applicable code or to result in poor performance, it's incumbent on the specialty contractor to educate the builder and to say "no." In my experience, it's more typical for the builder selecting trades based on price to get exactly what they pay for: low quality components which are poorly installed.

Dehumidification is indeed an important function for any air conditioning system, except in dry climate zones. Air conditioning systems can be designed to control (limit) relative humidity by design. That's why the code lists both a dry bulb and wet bulb design temperature. Where I live in coastal Virginia, the outdoor design relative humidity per code is a slightly higher than it is in Houston, TX. I have a single-stage air conditioning system on the 1st floor of my home and a two-stage compressor paired with a variable-speed air handler on the 2nd floor. Both floors are set to maintain 74F which is the same temperature it currently is outdoors this morning (a welcome change after a long heat wave.) Indoor relative humidity in my home is currently 39% on the 1st floor and 46% on the 2nd floor vs. 76% outdoors. I never see relative humidity greater than the low 50% range except in shoulder seasons when there is no demand for air conditioning. I have a dehumidifier installed on each level of my home for those periods.

Comparing Houston, Tx to Coastal Virginia is like? _______________ (lets argue, change the subject -- common fodder for builders if I had to fashion a guess.)

While you like to think Katy, TX has a unique climate, Ray, there are plenty of other locales with similar HVAC climate design criteria per the 2018 International Residential Code (IRC.)

Simply, stated, that means air conditioning systems in those locales need to perform under similar conditions to yours, albeit for fewer months in the year. Here's how your area compares with the design criteria for mine:

Houston, TX 94F d.b. 79F w.b. (62% relative humidity)

Norfolk, VA 91F d.b. 78F w.b. (66% relative humidity)

You don't need a sophisticated, inverter-controlled air conditioning system to maintain indoor conditions including relative humidity within the comfort zone. You can do it with a properly designed single-stage system, like mine, for example.

My cooling season is shorter than that of Katy, Texas. But I assure you there are days when humidity rises above 90%. This happens when the temperatue hits 95 degrees followed by thunderstorm and temperature drop. I think keeping the humidity between 42% - 45% is good under these conditions. This is what i typically see in my house. I suppose this range is too wide to say my AC is contolling the humidity. I dont think most people notice a 3% variation in humidity.

The ASHRAE-defined indoor comfort zone is 68F to 74F d.b. temperature in winter; 72F to 80F d.b. temperature in summer with relative humidity in the range 30% to 60% By definition, relative humidity is temperature dependent. If you're controlling temperature within the comfort zone and maintaining relative humidity within the comfort zone, your system is providing the appropriate control of indoor conditions.

The minute we start comparing actual temperatures between two so called similar locations saying that there isn't any difference?

click to enlarge:

I ran an AC trouble call yesterday after noon -- where actual air temperature was over 102F in the shade.

That age old classic... let's talk about the weather. (argue more like it)

Consult your local builder for his 4 day forecast.

Ray,

You apparently never learned the difference between "weather" and "climate." HVAC systems are designed based on temperature data gathered over long time periods--not the temperatures during any given week. This enables a HVAC system in Newark, NJ to produce the same indoor conditions as one in Houston, TX when the outdoor conditions are the same, even though that might not occur all that often. The air conditioning design temperatures for 97 1/2% conditions are listed in the International Residential Code. Here they are for both locales:

Houston, TX 94F d.b., 79 F w.b.

Newark, NJ 91F, d.b., 76F w.b.

The design of systems for both locales would be similar, albeit the length of cooling seasons and the life-expectancy of the systems is different.

Hey guys, this was about a water heater - let's not have this pissing match (again).

Hey guys, this was about a water heater - let's not have this pissing match (again).

Too late. LOL. Y'all choose the direction. I'm just here drinking my morning coffee dispelling daily myths of those who will bang on a keyboard all day long for things they don't do themselves. (I only come here in the early morning doesn't matter to me what the discussion is as long as it's in HVAC -- it's what I "actually" do.)

If you want to argue about the weather / argue about refrigerants certain builders don't purchase / argue about heat transfer / nexus of the universe condensate drainage problems / etc.

The one thing Charles is really good at is finding nails to beat to death. When a nail is too tough he'll change the subject. ~called it look directly below this post...

For the record I wouldn't call an argument over the weather a pissing match. I've provided concrete evidence why my stance on the subject is where it is.

Charles probably doesn't even know what 102F in the shade at 5pm central time feels like if I had to place a bet. Here have a look at a national map. (click to enlarge)

I provide you proof as to why... (context for keyboard warriors I like to call it.)

It's hot in Texas, Ray. I get that. I've lived there on two occasions in two different cities. But the temperatures this week in either of them isn't the basis for designing an HVAC system anymore than it is in Katy.

But the temperatures this week in either of them isn't the basis for designing an HVAC system anymore than it is in Katy.

Charles this thread isn't about designing an HVAC system. There was one reason I got involved with this thread...

Do you even remember what it was?

We've gone from humidity to the weather to comparing different locations weather in comparison to where I live...

NOW let's change the subject again? Because Charles has no where left to go...

The OP related humidity problems with their recently installed air conditioning system. They stated " A few other areas of humidity problems have popped up with the new AC. The condensation problem was occasional before but it’s more frequent now. The AC has been tweaked some to eliminate more humidity. Better but not perfect." A portion of this thread was intended to help in that regard,

A portion of this thread was intended to help in that regard,

I wouldn't consider anything you've put in this thread as helping Charles.

An air conditioner's primary function is to drop temperature. It will not "control" humidity.

I put quotes around the operative word for a reason... what do you suppose that reason is?

(this should be common sense, but common sense isn't so common unfortunately. Especially in the realm of those that can't be bothered with purchasing refrigerant or actually do a job they like to claim is so easy to suggest it's not rocket science.) We'll call this helping for what purpose?

Why it's not helping in my dictionary. (you the reader get to choose -- I'm only here highlighting why you might be having the trouble to begin with.)

The above misinformation explains why so many homeowners suffer the consequences of improperly-sized systems which cool indoor air too quickly and fail to adequately de-humidify it. The result is that indoor temperature may control to setpoint, but the indoor conditions are cold and clammy. Here's what Carrier Corp. says about an air conditioner's function:

"An air conditioner provides cold air inside your home or enclosed space by actually removing heat and humidity from the indoor air. It returns the cooled air to the indoor space, and transfers the unwanted heat and humidity outside." https://www.carrier.com/residential/en/us/products/air-conditioners/how-do-air-conditioners-work/#:~:text=An%20air%20conditioner%20provides%20cold,unwanted%20heat%20and%20humidity%20outside.

A properly-designed air conditioning system deals with both the sensible and latent (moisture) heat loads. To this end, the design dry bulb temperature, design wet bulb temperature, and the desired indoor relative humidity are all inputs for calculating the cooling load following ACCA Manual J methodology.

My job is to fix your AC in a high heat climate long after the builder is long gone.

Air Temperature extremes in Katy, Texas 6pm in the shade Aug 20, 2023 (click to enlarge)

Does Charles have any clue what 104F air temperature means / or feels like... nope.

click to enlarge heat extremes map showing US areas number of days over 100F.

Where Charles is located --clearly marked on the map-- I could provide you cooling he only talks about --- with one arm tied behind my back.

Charles will twist and squirm and probably try to change the subject yet again. He has to... no where left to go.

In Katy, Texas we've had these extremes OVER 20 days now... Another hot one incoming.

I stand at the ready... calling your builder is not advised.

How about an old review from my refrigerator?

Yeah it was hot then too... over 100F.

I service the Katy, Texas area.

No one is disputing that it's hot in Texas, Ray. Nor the length of your most recent heat wave. What is at issue are your claims that the primary function of an air conditioner is to decrease temperature and that it doesn't control relative humidity.

The primary function of an air conditioning system is to maintain occupant comfort. That includes controlling both temperature and relative humidity. ASHRAE research established a comfort zone with a temperature range of 72F to 80F in summer and an upper limit of 60% relative humidity (there is no lower limit in summer, but there is a 30% lower limit for relative humidity in winter.) Relative humidity is a function of temperature-- so controlling indoor temperature affects relative humidity, too. Limiting the indoor relative humidity to 60% at 80F only requires that the dewpoint be 65F or less; limiting the indoor relative humidity to 60% at 72F only requires that the dew point be 57F or less. Either condition can be maintained by a properly-designed air conditioning system. A case in point: Conditions here in coastal Virginia this morning are 72F and 94% relative humidity. My (1st floor) single-stage Carrier air conditioning system is maintaining indoor conditions of 73F and 41% relative humidity.

What does control mean Charles?

You (the operator of the system) is able to set a predetermined number for the system to shoot for?

What number? Temperature? To control what?

Temperature.

What number / what instrument is used to "control" humidity? It's displayed in percentage isn't it?

Not Temperature.

Simple logic even a builder "should" be able to understand. I use the word "should" with extreme caution... Charles has proven me wrong more than at least a half dozen times by now.

Limiting relative humidity to 60% is control. It's a by-product of controlling temperature.

Charles it's quite easy when your purported Humidity is significantly under what you proclaim it to be. oopsie.

Click to enlarge.

so a 6% drop inside running an air conditioner... sure. That doesn't mean control by any stretch of the imagination.

Let's watch Charles squirm some more... see if he changes the subject again?

Now you want to debate the weather conditions outside my home? Really?

You're a builder aren't you Charles? Blowing smoke is 90% of your profession. (after the structure is built, prior to that 90% is beating nails to death. -- ask me how I know. LOL)

You wanted to debate weather condtions here? oopsie. Now when the shoe is on the other foot? You Charles have a problem? oopsie, oopsie.

Ray,

According to weather.com, the current temperature in Williamsburg, VA is 73F and the dewpoint is 72F, that's a relative humidity of 95% You're welcome to verify it on weather.com Honestly, Ray, if you worked half as hard at knowing your stuff as you do badmouthing and trying to discredit those who disagree with you, you'd be genius.

If you're not testing, your guessing Charles.

Badmouthing? another term for when the shoe is on the other foot.

Do as I say, not as I do? Isn't that right Charles? (The nexus of universe must have shifted to Norfolk, Va.) ---recalibrating.

another source from yesterday:

humidity 60% above

a 3rd source...

humidity 66%

All of these other sources are considerably lower than yours Charles.

But hey, let's call this badmouthing? Sure Charles.

Ray,

Norfolk, VA is the closest city to us for IRC design temperature data, but I don't live there. If you'll look on the map, you'll find Williamsburg midway between Norfolk and Richmond, VA. The weather can be drastically different in any of the locales. This morning Norfolk and Williamsburg are both 71F d. b., 67F dew point and 93% relative humidity. You can check weather.com if you like. The indoor relative humidity on my 1st floor is 41% at a d.b. temperature of 73F courtesy of my Carrier single-stage air conditioner.

if that's the case Charles you may want to set up a weather balloon outside your door, then beam the live info into Houzz. Sounds like nexus of the universe kind of readings.

If it varies this much around those parts no telling what your actual readings are right outside your door. You want accurate info don't you?

It's like you posting averages for Houston and comparing this (inaccurate info due to current conditions) to that areas avg. when we are in the midst of an over 20 day record heat wave.

All this and you still haven't given us your 4 day forecast? (shame -lol)

Ray,

You are wont to dismiss whatever you don't understand as false and that's a lot of stuff.

The temperature data I posted above are 97 1/2% design temps taken from the IRC code. Those are the temperatures which are used as inputs in an ACCA manual J calculation of cooling and heating loads. They don't represent the peak temperatures in a locale and we don't design air conditioning systems for peak temperatures. If they were, they'd be even more oversized than they typically are.

The design temperatures are 97 1/2% temperatures based on 30-year averages. That means temperatures should be less than or equal to the summer design temperature 97 1/2% of the hours in a given year based on 30-year averages. Summer temperatures will be greater than design temperatures and winter temperatures will be less than design temperature 2 1/2% of the hours in a given year.

As we are subject to more severe weather, it may be appropriate to revisit the use of 30-year average temperatures for determining IRC design temperatures. If you'd like to advocate for that, I'm sure the International Code Council would be delighted to hear from you. Don't forget to direct them to your videos, they're sure to enjoy those, too.

I'm still here! Ignoring nonsense... but did see one more thing that I had a question on. The install manual says that the condensation line should not be under water, and it should be open to the atmosphere. I do have a condensation pump on the drain line and the tip of the drain line appears to be about an inch under water. I could cut it shorter (and probably will... leaving it long enough to stay tucked into the pump reservoir but not be under water.)

I'll now return to my bucket of popcorn.

Dave

Hey Dave,

You can always put the condensation line to a 5 gal bucket for now just as a test to see if being open changes anything.

After it's shut off because of a "leak", when you open it up is there actually condensation inside the unit?

Condensation within the enclosure is a function of the temperature vs. dewpoint temperature--not the condensation removal rate.

The temperature data I posted above are 97 1/2% design temps taken from the IRC code. Those are the temperatures which are used as inputs in an ACCA manual J calculation of cooling and heating loads. They don't represent the peak temperatures in a locale and we don't design air conditioning systems for peak temperatures. If they were, they'd be even more oversized than they typically are.

Charles you speak codes like they are end all be all. I've been doing HVAC for just over 30 years now... in that time use your imagination how many times the codes have changed?

Code can vary from one area to another... what is allowed and what isn't. The net effect more often than not are increased prices and or restrictions to building. People complain there is no affordable housing down to -- there is no housing available at all, then scratch their head and wonder why.

As we are subject to more severe weather, it may be appropriate to revisit the use of 30-year average temperatures for determining IRC design temperatures. If you'd like to advocate for that, I'm sure the International Code Council would be delighted to hear from you.

So Charles this will mean all the dribble you posted is irrelevant?

Yeah I'd do it just to spite a builder, my revenge of 30 years correcting fine dining and fine accommodation / contractual obligation type ways.

Still no 4 day forecast, no weather balloon emitting correct hourly weather information out of Norfolk, Va. shame, shame, shame. -lol-

-------------------

I do have a condensation pump on the drain line and the tip of the drain line appears to be about an inch under water.

Dave it won't matter that much in my opinion. Without proper care and maintenance the reservoir of the condensate pump will become a sludge bucket. Due to gravity going into the condensate pump the condensate will find it's way into the reservoir.

As long as the pipe feeding the reservoir is above the bottom of it, not much to worry about except for the previously described maintenance above.

CR Homes, you may want to consider doing what I've done and what the good folks of Katy, Tx do - pretend he's not there.

Rheem qualified plumber came out. There are issues with the condensation reservoir. There is media in reservoir to neutralize the condensate and it has a drain. None of it is mentioned in documentation when troubleshooting or included in maintenance information. Media probably needs replacing (on order with reservoir.) Draining it had very dirty and thick yellowish fluid.

Plumber told me to drain it every few months. The valve is shown but not described in any documentation I’ve seen.

Hi, Dave,

Like any hot water heater, your tankless-type hot water heater requires periodic maintenance. If the condensate neutralizer maintenance isn't described in your homeowner's manual, it may be because the manufacturer expects it to be performed by a qualified technician along with other routine maintenance such as flushing the heat exchanger. That said, problems with a condensate neutralizer don't correlate with outdoor relative humidity and aren't consistent with your original problem description. If the condensate neutralizer was a problem, it would produce an error code at the display on your heater or remote.

I have the same unit - and so do several other people I know.

Draining that neutralizer tank isn't a regular maintenance item and it should not be clogged up.

(It's basically a plastic tank with limestone in it). It exists because some jurisdictions require the condensate to be neutralized before discharge.

You might have to replace it after 20 years or something - but it's not a regular item.

I think it clogged somehow - although I don't know how that happened.