Air Conditioner Woes

I thought Lennox was more reputable than this. No adequately large air unit should be frosting up in an AC application. Indoor temperature only 5 degrees cooler than outdoor is definitely not sufficient. That was completely idiotic. Unfortunately, if you simply fire those dolts, you won't have any better recourse.

I realize that high velocity ducting can economize on duct size, but it tends to be noisy and to increase fan horsepower requirements. In general, it sounds as though your system was based entirely on lowest initial cost rather than on sound AC design. On the other hand, if the overall construction had no room for larger ducts, maybe the HVAC guys did all they could....

Yeah, I thought as much. Hes gone and i have hied another. He did say something about not enough vents though..Also, could it be that the freezing up was due to that, or because the blower is too small. I hope you are wrong about the poor AC design analysis. I will have a full evealuation done . Thankyou!!

Today I noticed a little coolant on the floor.

I don't think that would be coolant; I think the coolant is only a liquid in a closed, pressurized system. Any that escaped would be as a gas.

Did the technician check the air handler section? You might need to clean the coils and flush the drain pan that catches the condensation off the coils. Check the drain (or pump) line that deposits the condensed water outside.

You might consider having the system checked to make sure it is sized properly to your house. Units that are too small or too big won't work properly.

Thankyou!! I have hired another tech. and will ask him to do all the things you mentioned. After, I will post his comments. Its great you people are willing to give informed advice. Thanks again!

Without seeing your AC unit I would say that it is undersized for the size of your home and the ductwork may also be undersized.

The velocity of the air should be stronger than described and the temperature should be more than 5° difference from the outside temperature.

Ensure that your inline dampers are all fully open.

If this is an older unit it may be on it's last legs.

Also if it has been running all of the time,trying to force large quantities of cold air through too small ductwork it may frost up as well as shorten the life of the unit.

Please get an independent pro from the BBB list or recommended by someone you trust to come in and evaluate your system.

Understand if the ductwork is mostly round or oval pipe with a lot of "bends" this will slow the airflow and cause undue stress on your AC unit as each 90° bend = 8 feet of duct.

Good luck

Wow, thankyou...I am having reassessed by another tech. My house is completely finished and the idea of putting in more vents is worrisome. Lets say the unit is the right size. Therefore it is possible that either it is dying, or it being overworked by the lack of vents , and or kinks in pipes etc. Could you just punch a much bigger vent somewhere, and would this lesson the stress on the unit and allow it to work as it should etc-instead of punching a whole bunch of small ones...Also, where exactly are the inline dampers...Thankyou for your knowledge...

Sorry for the delay.

Do you know where the plenum is? Do you know what it is? It is the big metal box around the "A" coil where all of your small ducts come from. Near the beginning of the ducts you should see small handles on the ducts, these control the dampers and should be running in line with the duct lines. If they are "across" the ducts then they are closed. Turn them to open them. You may have to SLIGHTLY loosen the nut on the handle to get it to turn. Be sure to tighten the nuts again.

As far as larger vents...you would need to run a duct to feed a larger vent. Do you have space to do that? You could cut a vent into the plenum (about a 4X10) if you don't mind cooling your basement. But please have a pro do it as he has the tools for this job and is less likely to damage the coil or cut the hole too large.

He told me as long as the temperture inside is about 5 degrees cooler then outside it is working properly. This is not true. The coolant that you're seeing on the floor could very well be compressor oil, in which case, it may be on it's last leg. I live in a two story 1800 square foot house that is cooled by one four ton unit. The experts will tell you that this is more than you need, I disagree, it's 100 degrees plus here in raleigh, and the inside of my house is about 69. Unfortunately, when houses are built the contractors do not necessarily use what is best, but what is the cheapest system they can get away with. I have to tell you, the the best way to keep yourself from getting ripped off is to get online and do some research and familiarize yourself with the basics, there are online calculators to figure unit size, etc. And get multiple quotes from the experts, it may well be worthwhile to replace your vents too if that is feasible. The unit that is right for your particular house will fall within a fairly small set of parameters, amazingly, the so called experts will be all over the map, both in price, and what type of unit you need. Good luck.

online calculators...good idea!!

So, it could very well mean it is undersized..............

Thanks for your comments..I am having 2 different new techs come and re evaluate...

What you say about your 4 ton is interesting...Are you saying a 4 ton might be too small for a 2300 sq. ft. house....

I thought that if it is too big , it can cause problems...

If an AC unit is too large, it will start/stop/start/stop frequently, which is undesirable. If the unit is just a bit small, it will perform nicely most of the time, but on the really hot days your house will get a little warmer, though not so hot as to matter much.

If the ductwork and air flow of your system are adequate, the air off the evaporator should be around 45-50°F, and the evaporating temperature (of the refrigerant inside) should remain above 32°F, so that the coil doesn't freeze up.

If there are any air filters in the system, clean or replace them so that air flow remains adequate.

If you noticed a leak on the floor and this is recent, then it can only be compressor oil.

Now, if this is true, it means that somewhere along the pipes (near the leak, or follow the leak...) there is a punkture... loosing gas... can sometime produce a low pressure suction and freezing of the evaporator! that depends on the extent of the leak. If this carries on, the unit will not cool enough but the freon piping fromthe evaporator to the compressor will be icing.

This also can be due to a wrongly sized capillary (from condenser to evaporator) or a bad expantion valve ( any one of these could be on your unit... depends on age or maker etc).

Setting it up to run intermittently: Why? If the system return pipes are freezing, then Gas &/Or expantion valve(or capillary) problems. The unit is supposed to have a thermostat in the rooms and High + low pressure switches on the gas pipes to the compressor. He did not solve the problem and has no clue. Otherwise he would have explained to you what was wrong and then agree on the repair (you then can have a learned decision to make!).

frosting on the evaporator can be a low charge caused by incompetent service or a leak. in you case you list low air velocity which will also cause the frosting. this problem can be a dirty evaporator, inadequate return system, dirty filter, dirty blower wheel or in some cases the blower motor. these can be checked with a visual inspection and corrected as needed. it could also be that your blower is overloaded due to duct design. the actual external static ppressure of your system can be determined with a simple manoneter reading accross the blower section. then call the manufacturer with the model and serial number of your air handler and ask for the rated capacity. if esp is over, you loose airflow. this should be done with a wet evaporator.

normal evap temperature is 45'f, normal super heat accross the evap is about 14-17'f, easy to check. normal temp drop of air can be anywhere from 16-30'f. ashrae calls for sizing to provide 16'f indoor below ambient. in raleigh this should translate to 76'f indoors and 92'f outdoors which is never followed and you are normally up sized to keep you from complaining. you can run a manual j on your home and compare to the rating of your compressor to verify sizing.

this is the start. you could always go to the nate website and look for a local certified tech with and efficieny analyst certification and he can go through the whole system in about 2 hours and give you the correct answers but ask to see the cert on his nate id card before you waste your time and money. any tech that gets out of his truck with a manifold set and tank of refrigerant before he has analyzed the system problems should be asked to leave imediately. as long as your system does not rust away it could last longer than you with a little luck.

Systems like this should have an air handler designed for about 3-4 times the pressure that a "normal" home system operates with- normal home = about 0.15 to 0.2 inches w.g., high velocity unit 0.5 to 0.75 inches w.g.

These systems also usually supply air much like an automobile- around 40F- to compensate for the reduced overall airflow with the same overall cooling load.

The discharge plenum COULD be leaking a lot of air, causing reduced flow to the home.

The fan COULD be undersized or has gotten dirty (more likely) reducing airflow but still sustaining reasonable pressure- causing the frosting/freeze up of your coil.

First- check condition of your fan- use a brush (like a baby bottle brush) to clean out the forward-curved blades. Vacuum up any droppings to keep them from being sent down stream. I assume that your unit is a draw-through style (coil upstream of the fan) but, either way- you need to vacuum it from the incoming side (use the hand brush attachment) and, if possible, use a wet-dry vac on the inlet while spraying outlet side with hand-held spray bottle set for coarse spray.

If this does not solve your issues call the manufacturer of your unit on their customer service line (should be able to get from their website) with model AND serial number of your air handler and you condensing unit. If no customer service number, call the main telephone number and ask to talk with VP of engineering. Tell them about your problems and ask if the right machinery is in place. If it is not right, ask what you can do to make it right.

I will check the specs for the air handler...and search out someone who is a certified efficiency analyst.................this should get me on the right road......

I have never cleaned the fan. I presume one needs to shut things down first.

I need someone who can actually walk the talk.................like many of you!!!!

Much thanks again....

I am a Certified Energy Manager- and I have cleaned my furnace fan and my neighbor's A/C coil.

It is not hard, just time consuming.

A lot of really good advice here. I would definitely find out what leaked out of the unit. Any leak is bad news.

After fifteen years the coils on both locations are due for a professional cleaning. Cleaning evaporator coils takes a special cleaner, someone willing to get to the coils,(which on some units requires upside down work), and lots of spraying and rinsing.

Condenser coils can literally corrode away, or get so clogged with corrosion on the fins that they don't cool anymore.

I have seen blower fans so dirty and rusty replacement was the best idea. A clean new fan will have better balance and performance. Just rust will affect performance.

things to consider, condenser and evaporator clean and the right size, compressor the right size and charged properly and there can be no leaks (closed system). Moisture and / or liquid getting back to compressor WILL destroy it. Two systems, one system putting inside air across the cold coils and into the registers, (what is the distance from the farthest vents to the coil/s ? enough CFM or too much?) and the coil cold enough "off cycle" (second system). Also be concerned about condensation in the ducts during the heating/cooling cycles. The system should run on a "heat/cool demand" automatically

One thing that hasn't been covered is the air flow balance. Open the ceiling ducts in the upstairs during the summer and close the basement. Then reverse this in heating season. Make sure the SO hasn't placed furniture in front of the return air ducts.

Well, I have located 2 techs who are familiar with the high velocity system and the Lennox AC. One has done the number crunching and looks like the sizing of the gear is in line with specs. However, this does not eliminate the elements of my house which might be adding to problem, and, or, whether they are working to capacity, or whether it is due all the other varibles that you all have mentioned.Tomorrow the first tech will be coming.

Oh, a tech told me I should not close off any vents as this will be detrimental. Is this so...........

If the freeze-up is due to low airflow (very likely), closing ANY vents will only make a bad situation WORSE.

Let it breathe.

The chance of the airflow balance being perfect are slim. In a two story house with questionable insulation if all the ducts are "open" then there will be a potentially large gradient between the basement and second floor. By tweaking a little more cool air from the second floor vents in the cooling season and vice versa in the heating season you knock down some of that gradiant. It is all about comfort and sometimes that compromises theory.

It may be a little hard to do but you need to get a look at both sides of the indoor coil, make sure they aren't plugged. Also the indoor blower squriel cage make sure its not plugged, and v-belt?

Hi I am back with added situations etc...................

Tech tried to do test on condenser unit, but said he could not as fluid(gas) was coming back at him...............he said it was finished!!............actually, it was making alot of rackid when I first started using it this summer.............evidently it just stopped all together......................

okay, now the tech did an air flow test on all 32 vents................not surprising, the differences in velocity are quite extreme(500s all the way to 1400 and everything in between)

(I WILL OUTLINE SOME SPECS FOR ANYONE TO CRUNCH)- maybe someone has a solution. It has been suggested that a 5 ton would help things alot. Some have said that the rule of thumb is 8 vents per ton. I have only 32. I understand that this would lead to freezing again. A tech has said with the added solar load and design issues, the house would benefit with a 5 ton. Someone suggested improvising some kind of outlet in the utility room to offset extra velocity. Basement is all finished and does not lend itself to adding more etc.

There are 21 vents on main floor, 9 on 2nd floor and 2 in basement. Also, the condenser is a 4 ton. Square footage is as follows:1454 main floor, 972 second floor, and 1490 basement. There is large entrance facing south which is on basement level and extends up to ceiling of first floor.(the solar load here is huge-even with blinds.There are 4 vents at about 8 ft) Also, there is another large area-facing west-which also extends up from basement to first floor ceiling. There are 5 vents in this area which are low on the velocity scale(approx 620) As you can imagine, an accurate analysis of the square footage is hampered by these 2 large areas-and the 2 solar loads. In addition,the problems with the high velocity system not outputting equally compounds things!

The 2nd floor velocity is stronger as expected averaging at 1194-fluctuating from as low as 915 to a max. of 1460)

The main floor average velocity is 789-fluctuating from as low as 530 to 960.

Basement average is 622.

I guess it is safe to say that the needs was underestimated, the velocity system has problems-due to improper installation, or lack of output, or someother factor.

I am having another tech look things over again. It sounds to me that the last condenser was undersized, and so the number of vents is as it is. Could a person put a 5 ton in, rig something up-without tearing the house apart...Also, this fan apparently is capable of pushing a 5 ton. However, because there is so many inconsistencies with velocity, could I put a newer-higher output blower to get more air out............I understand that being oversized will cause freezing.Some guy said that high velocity systems always freeze up. This cant be true...........is it...........

I am hearing many negatives about the early days of this system..anyone care to comment..

Last year I did have a certain degree of cooling.However, it was never that sufficient in extreme tempertures(75-80s) Maybe, because of my dilemnas, it will always be marginalized..........

I generated a reply at about 130 am last night but it somehow never made it to the post. So- here we go again.

First- The "standard" sizing method for most reasonably insulated homes is 600 SF per ton of cooling. You have just over 2400 SF in your two main floors and call the basement 25% of actual, so another 375. The team that installed your current system probably took it short to keep costs down- which might explain some of you other operating issues.

That MIGHT indicate 5 tons, BUT it is always better (for comfort and for operating cost) to be a little small rather than a little big. IF the system cannot hold temperature, it will at least remove moisture, so you will still feel reasonably comfortable- and a house that is 76F when it is 96F outside is still pretty good, all considered.

Second- You DEFINITELY need the 5-ton fan-coil air handler (and the 5-ton coil) with the highest pressure fan you can get. The air flow is critical for two reasons- first, it will prevent frozen coils which have NO airflow and second- you can really use the circulation to assist in personal comfort issues.

Third- and here it gets really interesting- Since it appears that you will need a new system, you should have a commercial installer put in the new system rather than a residential installer. The reason is (this will sound a little off-the-wall, but it is totally solid technologically) because you should install TWO condensing units- One a very high efficiency 3-ton model and the second a standard efficiency 1-1/2 ton model.

The condensing units will be connected together by each discharging into a commercial high pressure receiver tank. The receiver will then be connected (using a single set of piping- sized for the full 4.5 ton capacity) to the expansion valve and 5-ton coil at the fan-coil. The receiver can be located on the pad between the two condensing units. Make sure that the discharge of each unit does not come near the inlet of the other.

You will need a two-stage cooling thermostat, with stage one set for the temperature you desire to maintain and controlling the 3-ton unit. Stage 2, set for about 1 to 2F higher than "optimum" will control the other 1-1/2 ton unit. The reason for standard capacity on the 1-1/2 ton unit is that it won't run THAT often and will cost about 60% per ton of the cost of the 3-ton unit. A commercial installer will be very familiar with receiver tanks and will have no problem setting it up and charging the units properly.

Finally- try to install some form of awning over the south entrance- during summer, the sun is very high above the horizon, so even 4 to 5 feet of extension will make a tremendous difference providing shade on the windows. As an alternative, you could plant a couple "pear" trees on either side of the entrance. They grow quickly to about 12-15 feet tall and spread about 30 degrees, then don't grow much after that or a lot slower. Any way- a couple suggestions.

You might want to plant some bushes around your new condensing units, or be ready to explain to the neighbors that it was suggested by a Certified Energy Manager with 35 years of experience and tell them about how much more comfortable you are and how much your utility bills have fallen.

Good luck.

I would be interested to know what the temperatures of the air are into and out of the evaporator, and the total cfm in the main duct. Then the refrigerant and the evaporating and condensing pressures. Your problem could be as simple as a plugged filter/drier cartridge, or a misadjusted expansion valve. Racket in the compressor could mean return of liquid to it; gas would not be a problem. Is there a liquid sight glass/moisture indicator in the system? If so, what do you see?

when it was working I did notice bubbles sometimes...................it would happen every few minutes................

Some occasional bubbles like that are probably not a problem. That can happen from normal pressure fluctuations in the system. Prolonged or continuous bubble streams, however, would suggest low system charge or a partially plugged filter/drier upstream of the sight glass.

I work with large ammonia systems with a different set-up, so it would be good to get experienced "freon" input.

hi yall:))

first off: if your condensor unit is freezing over on large refrigerant return line, and if service person has gassed unit properly, you are NOT moving enough air across cooling coil.

my house is not insulated enough(1972) , but difference in outside temperatur vs. inside max low temp is approximately 18 degrees. as outside temp goes up, so goes inside temp period..

any leakage , may be from cooling coil condensate drain . had same thing long time ago, mold/mildew scum built up and blocked line. rodded out, poured chlorine bleach in line each year, no problems since. had to repaint sheetrock twice, though.

if cooling coil has been slowly stopped up, by using cheap air filters or not changing filter on regular basis, this can be checked on the input side of return air at cooling coil. normally the blower motor is installed behind the cooling coil, so it blows into the coil. the service person should show you whats what in that area.

if your duct outlet temperature is not very cool, your could be freezing over at condensor from too little refrigerant or low air flow.

if service person uses clampon ammeter to check electrical load on compressor, and

if its about 95 degrees f. outside, the nameplate data for compressor fla(full load amperage) should be close to reading on ammeter at least around memphis,tn.

IT ALL DEPENDS ON PROPER REFRIGERANT CHARGING, AND PROPER MOVEMENT OF AIR ACROSS COOLING COIL.

these two things are the most important,

gerald b.

hi yall:))

first off, you should not have to add freon, unless you have a leak...

the a/c should run until setpoint is satisfied. this insures humidity removal and comfort level.

second: at what location, did it freeze up?

in another to same problem, mentioned normal difference(my house) is 18 degrees. if its 100 outside, inside normally is 82 f. (my house needs more insulation)

tech dont know but from hole in ground registered is misnomer

liquid on floor probably from plumbing or condensate from cooling coil drain pan. had same problem while back. ruint sheet rock. rodded out drain line, poured chlorine bleach, each year from then on to now, no more problems.

AS SAID IN ANOTHER POST:

IF FREON IS CHARGED TO PROPER LEVEL, YOU ARE NOT MOVING ENOUGH AIR ACROSS COOLING COIL. could be input side of cooling coil, restricted. ( reason cheap filters, changed between too long period of times.)

need more info on where freezing up.

have you tried turning boiler system off, because it could adding heat; taking away cooling effect.

THIS IS ASSUMING IT IS NOT A NEW HOUSE. when did problems begin?

gerald b.