NO Condensate, all drains clear, hi humidity

[CarlL]

I have a Lennox HS21 and an old Lennox G14 with a 3 speed blower. A relay was put on it to allow the speed to vary based on what the thermostat is calling for. There is no condensate flowing down the clear drain tube, ever. The drain is absolutely clear and the A/C cools the house very well. There are no signs of water leakage, either inside or outside the furnace. Humidity on the Honeywell thermostat is showing 68%, outside temp 92 degrees with high humidity in Kansas City.

A tech was out yesterday and says that he is stumped on how the system is cooling so well without putting out any water. He said that the A-coil is operating in the 55 degree range. Tech plans on discussing with owner and other repair people today and maybe with Lennox.

Anyone have any ideas where the condensate is??????

[54regcab]

Is the fan actually running on low speed? You may be oversized.

[mchild]

I have a Lennox HS21 and an old Lennox G14 with a 3 speed blower. A relay was put on it to allow the speed to vary based on what the thermostat is calling for. There is no condensate flowing down the clear drain tube, ever. The drain is absolutely clear and the A/C cools the house very well. There are no signs of water leakage, either inside or outside the furnace. Humidity on the Honeywell thermostat is showing 68%, outside temp 92 degrees with high humidity in Kansas City.

A tech was out yesterday and says that he is stumped on how the system is cooling so well without putting out any water. He said that the A-coil is operating in the 55 degree range. Tech plans on discussing with owner and other repair people today and maybe with Lennox.

Anyone have any ideas where the condensate is??????

What is the tonnage of the A/C? What is the CFM at the 3 speeds of the blower and what speeds did they set the relay up to activate based on the stage of the A/C? It could be several things that are causing the problem. One could be the blower speed. Too high a blower speed will reduce the A/C ability to effectively dehumidify.

[CarlL]

Thx for the replys. I am a non-technical old homeowner, so I may not have the right answers, but here goes.

The tech said that the blower runs on high speed when the thermostat calls for high on the compressor (HS21-036-1P). He said the relay cuts the speed to the same as the heating cycle when the A/C is on low. Something about Y1 and Y3, I believe.

He also said that the coil is not freezing up or dirty. The air flow into the unit is good, through a SpaceGuard air filter that I believe is Merv 13.

[mchild]

Thx for the replys. I am a non-technical old homeowner, so I may not have the right answers, but here goes.

The tech said that the blower runs on high speed when the thermostat calls for high on the compressor (HS21-036-1P). He said the relay cuts the speed to the same as the heating cycle when the A/C is on low. Something about Y1 and Y3, I believe.

He also said that the coil is not freezing up or dirty. The air flow into the unit is good, through a SpaceGuard air filter that I believe is Merv 13.

Without knowing what the CFM is of those two speeds we don't really know whether air flow is the issue. How did he determine the airflow into the unit is 'good'?

For a 3 ton A/C unit the high speed CFM should be in the 350 - 400 CFM per ton range. The lower CFM is better for de-humidification. That would equate to 1050 - 1200 CFM in high stage cooling and about 70-75% of that in low stage. Do you have the full model number of your furnace?

[heatingman]

Is the a/c unit brand new? As in a few days new? What temperature exactly does it maintain?

[CarlL]

The furnace is a G14-Q4-80 and the blower is rated at:
Hi-1793, Med-1295, Low-1050 cfm at 0 external static pressure.

Neither the furnace nor the A/C are new. Except for this condensate problem, they have run faultlessly for many, many years. The only reason I had the repair man out was that the A/C quit. Found some ants had fried the low speed contactor.

FYI-This is a 30 year old super insulated home with R-65 walls, R-80 double insulated attic, 3 pane or double 2 pane windows, passive solar, air lock entry, crawl space under basement rock heat storage and totally wrapped in plastic. House is 6500 square feet with separate bedroom wing and living wing HVAC systems. 800 gallon propane fill provides cooking, water heating and fuels both furnaces for a year.

[Dr.phil]

I might check for an overcharge.

[CarlL]

Forgot. We keep the A/C at 72 and it has no trouble with that. I believe it can go much lower. My wife messed up the new thermostat for the other, bedroom A/C last summer and I returned to find the temperature at 62 degrees with the outside temperature in the high 80's. The house is that insulated.

My wife's hair dryer will actually raise the temperature by 2 degrees in the winter and we stopped using the gas log blower system in the fireplace because it quickly became too hot.

[CarlL]

Charge was checked twice. A week ago when he came out to diagnose the contactor problem and again yesterday. Charge is correct and is still the 10 year old original charge. No leaks, additions or reductions.

[mchild]

The furnace is a G14-Q4-80 and the blower is rated at:
Hi-1793, Med-1295, Low-1050 cfm at 0 external static pressure.

Neither the furnace nor the A/C are new. Except for this condensate problem, they have run faultlessly for many, many years. The only reason I had the repair man out was that the A/C quit. Found some ants had fried the low speed contactor.

FYI-This is a 30 year old super insulated home with R-65 walls, R-80 double insulated attic, 3 pane or double 2 pane windows, passive solar, air lock entry, crawl space under basement rock heat storage and totally wrapped in plastic. House is 6500 square feet with separate bedroom wing and living wing HVAC systems. 800 gallon propane fill provides cooking, water heating and fuels both furnaces for a year.


The CFM at a more typical static pressure of .60 will be lower than what you have stated here but I'll use your numbers.

As mentioned before the high stage A/C should be in the 1050 CFM range and from you have said it is 1793. That is very high for that size A/C unit (about right for a 5 ton unit). Even the lowest speed may be too high for the low stage cooling as it should be close to 700 - 735 CFM. Your A/C unit will have a hard time de-humidifying the space with that much air flow.

Other issues, as suggested by others, such as refrigerant charge and metering devise problems can cause these problems too.

[HAP2]

Depending on the existing humidity level, it may take quite a while for condensate to develope/flow. Low humidity = low condensate flow. I know I have seen up to 45 minutes in 50% for condensate to start flowing on a dry coil.

[mchild]

Charge was checked twice. A week ago when he came out to diagnose the contactor problem and again yesterday. Charge is correct and is still the 10 year old original charge. No leaks, additions or reductions.

Has the A/C ever produced condensate? If so when did it change and what preceded it with regards to any changes to the system?

[mchild]

Depending on the existing humidity level, it may take quite a while for condensate to develope/flow. Low humidity = low condensate flow. I know I have seen up to 45 minutes in 50% for condensate to start flowing on a dry coil.

.

[mchild]

Charge was checked twice. A week ago when he came out to diagnose the contactor problem and again yesterday. Charge is correct and is still the 10 year old original charge. No leaks, additions or reductions.

Did the tech take sub-cooing and super heat readings? Did he leave them with you?

[CarlL]

No supercooling or superheating measurements were taken

To our knowledge, the lack of condensate has always been a problem.

The system seems to be the correct size for the large house is cools. It does not short cycle. The house is nearly 100 feet long, so there are long duct runs off of this furnace. That may be why the blower needs to push more air than in a smaller house.

I will await a call from the repair company and share all of the good info you have provided thus far.

Again, thank you very much.

[mchild]

No supercooling or superheating measurements were taken

To our knowledge, the lack of condensate has always been a problem.

The system seems to be the correct size for the large house is cools. It does not short cycle. The house is nearly 100 feet long, so there are long duct runs off of this furnace. That may be why the blower needs to push more air than in a smaller house.

I will await a call from the repair company and share all of the good info you have provided thus far.

Again, thank you very much.

If sub-cooing and super heat measurements were not taken then they have not confirmed the refrigerant charge. Taking running pressures alone can not confirm proper charge.

I'm seeing a trend here. They set the high stage cooling blower excessive high and they do not know how to check the charge. You may need a different contractor.

[teddy bear]

Forgot. We keep the A/C at 72 and it has no trouble with that. I believe it can go much lower. My wife messed up the new thermostat for the other, bedroom A/C last summer and I returned to find the temperature at 62 degrees with the outside temperature in the high 80's. The house is that insulated.

My wife's hair dryer will actually raise the temperature by 2 degrees in the winter and we stopped using the gas log blower system in the fireplace because it quickly became too hot.

With 72^F, 68%RH, the dew point inside the home is 58^F. A 55^F coil temp will not remove much moisture. If you want 50%RH with 72^F temp which is 49^F dew point, you need a <45^F coil temp. If the unit has the right refrigerant charge, have tech consider slowing the air flow to allow the cooling coil to be colder.
REgards TB

[talbot3]

I am just a home owner but this is my 2 cents:

If your house is at 72^F and 68% RH and your coil temp is 55^F, lets take a guess at your supply air temp: 57^F and 99%RH. This would mean you have a change of enthalpy in the air of about 5.4 BTU/LB. If your system is operating at 400 CFM/ton, the change in enthalpy should be around 6.67 BTU/lb (a tip picked up from UDarrell). A lower change in enthalpy could indicate too much air flow or the system is not removing its rated BTUs.

Being that your system has no problem controlling temperature (high sensible BTU removal), I would suspect that the fan is pushing to much air on the high setting. BTW the Q4 in your furnace model means the fan is can work with 4 ton units so it can move 1600 CFM at the furnaces maximum external static pressure.

If your system is removing its rated 36000 BTUs and the change of enthalpy is 5.4 BTU/lb, then the airflow would be about 1480 CFM which is almost 500 cfm/ton. I think you need to ask your tech to measure the airflow and adjust the fan if needed. If the airflow was too high, then the charge will need to be adjusted once the airflow is corrected.

[CarlL]

Turns out my memory is not as sharp as I thought. The furnace is not a Q4, it is a G14Q3-80. The blower speeds are a little lower at 1585/1382/980. By dropping the temperature on the thermostat to 64 to force the system to run on high and running the blower at its lowest speed, I was able to get a trickle of condensate out of the hose. Could not let it run that way too long or the house would turn into a refrigerator.

So, it does look like the blower speed is too high for really doing any dehumidification. As I said in an earlier post, this will have to be weighed against the need to push air out to some pretty long runs, without in-duct fans.

I will discuss with the service company owner today and think about the option of adding a dehumidifier to the system. All of this has to be balanced with air quality needs in a house that is a little like living inside an air tight box. Yes, we are set up to mix fresh air in.

Thx again for all your help.

[teddy bear]

Turns So, it does look like the blower speed is too high for really doing any dehumidification. As I said in an earlier post, this will have to be weighed against the need to push air out to some pretty long runs, without in-duct fans.

I will discuss with the service company owner today and think about the option of adding a dehumidifier to the system. All of this has to be balanced with air quality needs in a house that is a little like living inside an air tight box. Yes, we are set up to mix fresh air in.

Thx again for all your help.

Using a whole house dehumidifier because your a/c's cooling coil is not cold enough is not recommended because the results will be higher cooling cost. The dehu will have to remove all of the moisture in the home and will add to cooling cost. I would expect an extra hour of cooling during hot weather.
You will need a dehumidifier to provide <50%RH when you do not have a significant cooling load and the outdoor dew points +60^F.
Slow the a/c blower and re-direct the amount of cold air to the hotter parts of the home. Leave interior doors open as much as possible. Operate the a/c blower after the a/c has been off for a hour, to mix up the hot spots.
Regards TB

[kls-ccc]

Forgot. We keep the A/C at 72 and it has no trouble with that. I believe it can go much lower. My wife messed up the new thermostat for the other, bedroom A/C last summer and I returned to find the temperature at 62 degrees with the outside temperature in the high 80's. The house is that insulated.

My wife's hair dryer will actually raise the temperature by 2 degrees in the winter and we stopped using the gas log blower system in the fireplace because it quickly became too hot.

It sounds to me like the system has been oversized form the start and the duct was not properly sized and balances to allow for the long runs.

Was a load calc done when the house was built? Ultra high insulated/tight houses require a lot more attention to details than a regular house in HVAC layout and design.

[mchild]

Turns out my memory is not as sharp as I thought. The furnace is not a Q4, it is a G14Q3-80. The blower speeds are a little lower at 1585/1382/980. By dropping the temperature on the thermostat to 64 to force the system to run on high and running the blower at its lowest speed, I was able to get a trickle of condensate out of the hose. Could not let it run that way too long or the house would turn into a refrigerator.

So, it does look like the blower speed is too high for really doing any dehumidification. As I said in an earlier post, this will have to be weighed against the need to push air out to some pretty long runs, without in-duct fans.

I will discuss with the service company owner today and think about the option of adding a dehumidifier to the system. All of this has to be balanced with air quality needs in a house that is a little like living inside an air tight box. Yes, we are set up to mix fresh air in.

Thx again for all your help.

A properly designed and installed duct system will not have these issues. As you have found out trying to account for that by making other changes just makes the problem move to another area.

Find a contractor that truly understands air flow issues and has the ability to correct what you have. It may be as simple as adding dampers to each of the branch runs and then adjusting them so each branch is delivering the amount of air where it needs to be. It will allow the restriction of the air going to the closest branches and so more air is available in the farther locations. This should be done with an eye on the total level of restrictiveness of the duct system. Otherwise, you will have other problems.

While this will allow for a low blower speed to help with de-humidification, your blower does not have a low enough speed for the first stage cooling.

[tedkidd]

Sounds like an awesome place, where is it?

What they said.

When built equipment and contractor knowledge was 30 years away. Understanding homes like this is just starting to trickle to mainstream. Oversized was misunderstood and bigger was always better, not worse as we know today. Hvac contractor, if doing any calcs at all, didn't really know the house.

Time to start planning for, and spec'ing new equipment. Stuff is really awesome now, and if your back isn't against the wall, you are less likely to make mistakes you'll regret.

[Shophound]

. Could not let it run that way too long or the house would turn into a refrigerator.

So, it does look like the blower speed is too high for really doing any dehumidification. As I said in an earlier post, this will have to be weighed against the need to push air out to some pretty long runs, without in-duct fans.

All of this has to be balanced with air quality needs in a house that is a little like living inside an air tight box. Yes, we are set up to mix fresh air in.

.

Let me ask you this: with the blower on low speed, are there any rooms in the house served by the system in question that become too warm? If not, you do not have an air distribution problem. You have a dehumidification problem.

I'm surprised Teddy Bear hasn't recommended a whole house dehumidifier for the type of house you live in...well insulated and very tight. This is where such a device really shines...it can give you your required fresh air changes and handle humidity levels simultaneously.

Traditional central a/c systems installed in houses of average construction, when sized and installed correctly, work well for most cooling and dehumidifying needs because the house over the course of the cooling season has a fairly high sensible heat (heat you can feel) and latent heat (heat contained in moisture) gain. Your house differs from this profile being that it's well insulated, thereby reducing your sensible gain, and well air sealed, thereby reducing moisture intrusion from outdoor air leaking uncontrollably into your house.

One thing I must ask, does your furnace have a fresh air intake on it so your tight house can get its required fresh air exchanges? Or do you use an ERV or HRV? How do you get fresh air into the house?

[teddy bear]

[QUOTE=shophound;10473742]Let
I'm surprised Teddy Bear hasn't recommended a whole house dehumidifier for the type of house you live in...well insulated and very tight. This is where such a device really shines...it can give you your required fresh air changes and handle humidity levels simultaneously.

Traditional central a/c systems installed in houses of average construction, when sized and installed correctly, work well for most cooling and dehumidifying needs because the house over the course of the cooling season has a fairly high sensible heat (heat you can feel) and latent heat (heat contained in moisture) gain. Your house differs from this profile being that it's well insulated, thereby reducing your sensible gain, and well air sealed, thereby reducing moisture intrusion from outdoor air leaking uncontrollably into your house.
QUOTE]
I suggested that he should get his a/c straighten out and then add the dehumidifier. Yes, the ventilation feature should be used in any well built home.
Putting in a dehumidifier before fixing the a/c problem could lead to a unhappy dehumidifier customer. When the a/c has a significant cooling load like several hours, the house should be dry. Depending on the dehumidifier for all of latent heat removal requires a bigger dehumidifier and increased cooling cost.
Regards TB

[Shophound]

TB, it was after I posted that I realized you said in an earlier post what you said to me above. Sorry you had to restate it for me. :)

[CarlL]

The house is 30 years old. It is called an envelope home. Picture a house built inside another house. There are two walls separated by a foot of airspace on the north side. The "basement" is really an underground level. It does not have a concrete floor, but has 4 feet of crawl space under it with rock heat storage over fiberglass reinforced plastic. The south side is a nearly 100' x 12' solar room that draws air from the rock storage through ducts in the 12" concrete floor pad. The walls in the solar room are covered with brick to store additional heat. The doors, windows and 10 roof windows can open to vent the room in summer. The roof windows have awnings that can cover them in summer and the overhang was computer generated for our exact latitude to shade the windows when the sun is high.

Each of the two walls is 6" with double pane windows. Then there is Tyvek (one of the first uses) and 2" foam board on the outside. The house is covered in brick. The inside wall has an additional layer of plastic sheeting under the wallboard and all holes through the plastic were caulked or sealed. The attic has two levels, each with more than 15" of insulation over fiberglass reinforced plastic. The area between the two attic levels forms a plenum that allows heated air from the solar room to flow around the house to the front, where it drops between the front walls as it cools and deposits heat in the crawl space. The air then is drawn back up through ducts to the solar room. When it is below zero on a sunny day, the living space in the "inner house" sort of thinks it is 60 or 70 degrees out, because that is what the envelope is. That is why the A/C does not work very hard and we have lived through an area wide power outage for a week in sub freezing temperatures with the house never getting below 68 degrees.

We do have outside air to both furnaces and ducts that can bring fresh air into the house.

The extra costs of this construction were recouped years ago in energy savings. Plus, the huge solar room grows plants the year round.

As far as the duct work, yes it was carefully designed for the house, with a large number of runs, graduated ducts, careful sealing and taping, returns in every room.

When I started this, I might have given the impression that it was a major problem. It is not, just something I thought would be interesting. Lowering or raising the temperature in this house is not a major money issue. For 6500 square feet of conditioned space, our electric bill is under $1000 per year and our gas bill is about the same. That is with my wife having her office at home with multiple computers and a few big servers that run 24/7, a freezer and giant refrigerator.

[Shophound]

You might want to invest in a separate humidity sensor from what the thermostat reads. A Testo H2 Humidity Stick is a little spendy but it's a great tool. Otherwise just get any decent digital relative humidity sensor from a home center or discount store. And then walk around the house, room to room, and note what the average temperature and relative humidity readings are. Convert them to dew point using an online coverter for that purpose. If your dew point levels are below 55 degrees, and your average room temps are between 72 - 78 degrees, your a/c is removing sufficient moisture. If you find your dew point readings over 55, you have more work to be done.

[heatingman]

If you have two a/c's in a house like that, shut one off for good, and just run the fan on a timer to circulate the cool air from the other system. If the floor plan is fairly open, this should work fine.

[CarlL]

I like the idea of checking the humidity in each room. Will do that this weekend, as the expected temps are in the 90's.

heatingman - The house was specifically designed for two HVAC systems as backup for the solar. The floorplan is not an open one. Also, the bedroom wing is insulated from the living wing by an insulated wall and a pocket door. The thermostats are set so that the living area system is active from 10 AM to 10 PM and the bedroom from 10 PM to 8 AM. They do not overlap. Shutting down one system would not work as the ductwork is separate and the only path between the two areas is through the single doorways on the upper and lower floor.

I have sort of come to the conclusion that, with the two speed A/C nearly always running on low and the minimum speed of the blower at 920 rpm, the small trickle of condensate is all I am going to get. In truth, I am quite comfortable at 72 degrees, or even 74 degrees if I am not doing a lot of physical stuff. Just trying to keep the wife happy. I showed her that the A/C is putting out water by putting the hose in a pail for 24 hours. It put out about a quart or so. Maybe seeing that will psych her into feeling cooler

[mchild]

I like the idea of checking the humidity in each room. Will do that this weekend, as the expected temps are in the 90's.

heatingman - The house was specifically designed for two HVAC systems as backup for the solar. The floorplan is not an open one. Also, the bedroom wing is insulated from the living wing by an insulated wall and a pocket door. The thermostats are set so that the living area system is active from 10 AM to 10 PM and the bedroom from 10 PM to 8 AM. They do not overlap. Shutting down one system would not work as the ductwork is separate and the only path between the two areas is through the single doorways on the upper and lower floor.

I have sort of come to the conclusion that, with the two speed A/C nearly always running on low and the minimum speed of the blower at 920 rpm, the small trickle of condensate is all I am going to get. In truth, I am quite comfortable at 72 degrees, or even 74 degrees if I am not doing a lot of physical stuff. Just trying to keep the wife happy. I showed her that the A/C is putting out water by putting the hose in a pail for 24 hours. It put out about a quart or so. Maybe seeing that will psych her into feeling cooler

Carl,

When you posted the revised CFM figures you did not state at what ESP those figures were for. If they were for less than about .5 - .6 ESP it is likely your actual CFM will be lower than those figures. To really know what your actual CFM is you will need for a service tech to take the readings. It would be a good bit of information to have.

The next thing you may want to consider doing is having an automated damper installed on the return side of the blower that will reduce the amount of air the blower can pull through the return and over the cooling coil when there is a call for cooling. The damper would have to be fully open for a call for heating. It should not be too difficult for your contractor to it set up to partially close the damper when in cooling mode to reduce the air flow over the coil to 325-350 CFM per ton. Caution: This will not work with a variable speed ECM blower, in fact would probably ruin the blower. It is only being suggested as your furnace has a PSC type blower. If you take this path the refrigerant charge should be rechecked at the revised CFM to make sure the sub-cooling and super heat are correct.

And finally, it seems like the high stage cooling blower speed should be set for to the mid blower speed not the high speed but this should be confirmed once the ESP readings have been taken (at each blower setting) to verify actual CFM.