Category Archives: Air Conditioning

How to Fix Sweating Copper Pipes


How to Fix Sweating Copper Pipes

What you will learn from this article:
1) one of our readers submitted the question, How to Fix Sweating Copper Pipes – and we will answer her question.
2) a description of the problem with the sweating copper pipe
3) the name of the copper pipe causing the problem and why it is sweating
4) the repair of the sweating copper pipe to stop it from sweating
5) what you need to know about sweating pipes and any moisture problem in your house
6) lots of resource and related links to help you learn

How to Fix Sweating Copper PipesHow to Fix Sweating Copper Pipes – Richard, we have an air handler in a finished attic closet. We use the attic for our home office and TV room. I noticed the last time I went in the closet the copper pipes that go into the air handler were sweating and dripping on the floor. It is a wooden floor but I think if this continues it will eventually ruin the floor and possibly the ceiling down stairs. What can I do to fix this problem of sweating pipes? Does it mean there is a problem with our air conditioner? Will I have to call a my HVAC service guy to fix this or is it something I can fix myself? We have used your site for many years to answer questions about our HVAC system. Thanks and I look forward to your reply. Joanna K. Hibernia FL

Joanna, You are talking about the suction line that goes into the air handler. Somehow it lost its insulation and is sweating in the closet. The suction line typically operates below the dew point. When you have something that has a temperature less than the dew point temperature then it will sweat. The moisture in the air is condensing. Changing from a vapor to a liquid. A very good example of this is a glass of ice water sitting on the table. The temperature of the glass is so cold it is below the dew point temperature. The glass sweats and leaves a wet spot on the table. Thankfully someone invented coasters to protect wood from cold drinks. Now we need to invent a coaster for that sweaty copper pipe you have there. LOL.

Related Link: Another problem with an air conditioner and a leak (opens in a new window)

Anyhow Joanna, this is something you can fix yourself very easily. Find your local hardware store and ask them for Rubatex pipe insulation. It a black foam insulation. It is better if you get the kind with a split on the side and on the side of the split is a type of adhesive with a protective plastic strip on it.  You will trim the length of Rubatex you will need to cover the bare copper pipe and then peel the protective plastic off of the adhesive strip after placing the insulation over the pipe. Line the split up and make sure the adhesive glues the Rubatex split together. You want to create a vapor barrier to keep the humidity out and away from the pipe. That should fix your problem of the sweaty copper pipe.

Related Link: An Air Conditioner caused severe water damage (opens in a new window)

It is important for you to know a few things about this repair to your air conditioner lines:

  1. If the pipe has been leaking long enough then it is possible that some of the moisture dripped down the pipe and went into the chase where the pipe runs. Sometimes, especially in new construction, the installer will use the void in the wall as his chase to run the pipes to the condenser. If that moisture got inside the walls it is possible it created a problem with mold and mildew. Mold and mildew loves dark, moist areas.
  2. It is important that you only insulate the suction and not the liquid line. The suction line is the bigger of the two pipes that run to your condensing unit. Even the part of the suction line that runs in the chase should be insulated with Rubatex and have a good vapor barrier quality of insulation on it otherwise you get the problem described above in number one. Never insulate the smaller pipe. It should never sweat. If it does sweat it would defy physics.

If you suspect mold or mildew in your walls then you will have to probably call a professional to look into it. Most HVAC companies in Florida are well aware of these problems as the humidity in Florida is something they have to deal with sometimes. At least the problems that come with high humidity and removing it from a conditioned space.

Related Link: Indoor Air Quality in your home or business (opens in a new window)

How to Fix Sweating Copper Pipes | HVAC Cooling Repair – Conclusion

There are companies that specialize in water damage and sometimes that includes dealing with the mold and mildew inside closed spaces. I know these companies use a special spray that kills the mold and mildew and prevents it from coming back anytime soon. I know that some molds and mildews are not good for health especially not breathing it everyday. I know there are some people with severe allergies to mold and mildew so make sure you protect yourself. In this case of the sweating pipe it is easily fixed. Or at least I hope it is easily fixed. Good Luck Joanna!!! I hope this helps!!

What Does Wikipedia say about Mold and Mildew Problems?

High Performance HVAC

How to Fix Sweating Copper Pipes | HVAC Cooling Repair


Supply Vent Myth – Does Closing Supply Vents Save?


Supply Vent Myth – Does Closing Supply Vents Save?

What you will learn with this post:
1) How modern duct systems are designed
2) How closing the supply vents effects the static pressure in the duct work
3) How closing supply vents effects modern HVAC equipment
4) How to save energy and therefore money
5) Where to obtain the books and/or software to learn how professionals design duct systems and do load calculations for sizing heating and cooling systems
6) How heating and cooling equipment ie furnace, air conditioner, or heat pump can be effected by closing off supply vents
7) Alternative methods used in commercial HVAC
8) Alternatives for residential HVAC

The Supply Vent Myth – Does Closing Supply Vents Save? The Grand Myth

Supply Vent Myth – Does Closing Supply Vents Save? – A myth many people believe is that they can close off some of their supply registers and save money. Supply Vent Myth - Does Closing Supply Vents Save?This may be true if you only close off less than ten percent. The system installed in your home is designed for a certain amount of airflow. If this airflow is restricted in any way it causes the system to function improperly and could cause system failure. This myth most likely goes back to the early days when people would close off most of their large home in the winter to save on coal and wood usage. Today’s modern HVAC systems are designed specifically for a certain amount of airflow and if you restrict that airflow, whether it be by a dirty air conditioner filter or closing off supply vents, problems will occur. Open those supply vents, closing too many off is the same as a dirty or restricted filter.

 Supply Vent Myth – Does Closing Supply Vents Save? – Static Pressure

By design modern HVAC air delivery systems use static pressure for duct work design. It is how designers size the duct work. A certain amount of static pressure in a given size duct work system will deliver the appropriate amount of CFM’s needed or required for a given house or apartment. The designer designed the duct work for the air conditioner or cooling system. It is a little complex to describe the process of designing and sizing a duct system as there are several factors in that process either required by code or using the Manual J Residential Load Calculation and the Manual D Residential Duct Systems but the system is sized for a certain amount of airflow and static pressure. When you close off the supply vents you change the static pressure and the amount of air delivered to other vents in the system. Coupling too many supply vents closed off with a slightly dirty filter and you begin causing problems with air conditioner and even the furnace if it is winter time. The final answer to the question of: Supply Vent Myth – Does Closing Supply Vents Save? is no in the long run for a modern HVAC system you are causing problems with your air conditioner and possibly causing problems with your heating system.

Duct Pressures and Leaks

supply vents and duct workA good designed and sealed duct system is balanced and does not leak. That is by mechanical code (for new systems but always check with your local code enforcement agency for details) and in ideal situations. In the real world, according to the Department of Energy, the average duct work system leaks more than 20% of the air. That is 20% lost that your air conditioner or heating system worked hard to produce.  Lost energy unless you like paying to heat or cool a crawl space, basement or attic. Most people do not want to heat or cool those places so aside from the air lost the homeowner or business owner is also losing the dollars it take to produce that 20% of lost conditioned air.

Related Link: What does the Mechanical Code say about duct systems and duct leaks? (opens in a new window)

In most commercial new construction projects and in residential duct work installations some states require a DALT or Duct Air Leakage Test where the newly installed duct work is tested for leaks. This test is typically witnessed by a third party and/or Code Inspectors to ensure the new duct work is leak free and meets all requirements of the code.

If you close off those supply registers it will increase the pressure inside the duct system and force more air out the leaks in the duct work if in fact your duct does have leaks. When was the last time you had your duct work inspected for leaks? This will also cause more air velocity to flow out of the registers that are not closed. In the summer a slight draft or breeze is good but in the winter a slight draft or breeze makes you feel cooler and most of the time in the winter we do not want to feel colder. Yet another reason why you do not want to close off your supply vents.

Your Heating and Cooling Equipment and Supply Vents

What happens to your heating and cooling equipment by closing off too many supply vents? It really depends on what you have and if you are heating or cooling:

  • Air Conditioner – low air flow is not good for an air conditioner at either the condenser or the evaporator. Low air flow on the evaporator coil leads to a frozen air conditioner. Whenever I get a call and the customer tells me the air conditioner is frozen I automatically think of two things. Either the system has low air flow across the evaporator coil or the system has a refrigerant leak and has a low charge of refrigerant. Either way the first thing I check when I arrive at the customers house is the air flow. Sometimes I find the customer closed off too many supply vents in conjunction with having a dirty filter. This problem is easily corrected however if left to continue this way you could possibly cause severe damage to the compressor. And replacing a compressor is not cheap in any regards.
  • Since a heat pump uses the refrigeration process to heat and cool the heat pump can be damaged in much the same way the air conditioner is damaged when the heat pump is operating in the cooling mode. In the winter time when the heat pump is operating in heat mode low air flow will cause the pressures inside the refrigeration system to rise. Another way to possibly cause damage to refrigeration components in your heat pump.
  • a Cracked heat exchanger for a gas furnace

    a cracked heat exchanger for a gas furnace

    A gas furnace on the other hand needs the air flow to keep the temperature inside the heat exchanger at engineered temperatures other wise you will begin causing problems with the limit switches and causing the furnace to quit operating all together. Other possible problems from this is damage to the heat exchanger in the form of cracks because it was operating outside of its designed and engineered temperature ranges. Blower motors are also sized for a certain amount of air flow. When the air flow is reduced the motor will operating at a higher than normal temperature which means it will reduce the life of the motor.

Another aspect other than what is mentioned above is cold/warm air infiltration through tiny cracks in windows and other places. When you close the vent in a particular room the cold air (winter time) and the warm air (summer) slowly creeps into the room making it cooler or warmer than normal. Since it is unlikely that the inner walls of the building (home or office) have insulation then the that will cause a higher than normal load in the house if you would of otherwise left the supply vent in service and kept the room at normal temperatures.

So you can see by trying to save a few dollars on the heating or cooling bill you can actually cause bigger problems that will end up costing much more than you can save by closing off your supply vents.

Alternatives Used in Commercial HVAC to Modulate Supply Vents (Supply Air)

In commercial HVAC there are older systems called VVT’s or Variable Volume Terminals and these systems used modulating dampers and rudimentary controls along with barometric dampers to modulate dampers to supply ducts and registers. The problem with these systems was everything was hooked up to a constant volume air handler or roof top package unit. So while the supply dampers modulated open and closed the air conditioner or gas pack continued to run at 100 percent. So when the system really did not save anything for energy efficiency purposes but it did reduce air flow to supply vents based on the control variable in the controller and what the thermostat input was to the controller. When the dampers closed off enough the excess coming from the air handler or roof top unit was vented out a barometric damper typically in a plenum above the ceiling. These systems went by the wayside because they really did not save energy.

Next comes the pneumatic VAV or Variable Air Volume Systems. These systems did save money but required special HVAC equipment to work properly. An air handler with modulating vanes on the blower so air flow could be reduced along with either several compressors that would unload so when the system was calling for less air the compressors would unload and the modulating vanes would reduce the air flow. The compressor unloading was designed to match the air flow so the evaporator coil would not freeze. Vice versa for when the system needed more air. The compressors would stage up and load the vanes would modulate to increase the air flow. While these systems can be old and clunky they worked to save energy and some still continue to work in some buildings. This is simply an example of one of the types of systems I have worked on. In commercial systems there are several other ways to modulate the cooling and the air flow.

Modern VAV or Variable Air Volume Systems use direct digital controls and variable frequency drives along with complex algorithms inside the microprocessor controller to modulate the systems up and down based on demand and these systems save a lot of money. None of these alternatives are currently viable in residential systems unless you have a huge house or can afford to pay several thousands of dollars to have a system like this installed in your home. While it would save energy and which correlates on the money you spend monthly on energy the return on investment would be several years and there are other residential alternatives to installing a commercial type system in a residence.

Residential Alternatives for Saving Energy Versus Closing Supply Vents

Quick and simple but expensive options for you are:

  • Geothermal heat pump – these systems are very efficient especially the modulating systems. You can even find one that will heat and cool plus make hot water for you. There are special requirements for having a geothermal heat pump system and this includes either having lots of land (more than an acre), a large body of water adjoining your land or a couple of dependable wells on your property. If you are interested call a company that specializes in geothermal systems.
  • A few manufacturers are making very high SEER completely modulating air conditioners, heat pumps and gas furnaces. These types of systems have the ability to run between 20% and 100% based on demand and this is really what you are looking for when you are thinking of closing off the supply vents.
  • A lot of ductless minisplit air conditioners or heat pumps are fully modulating and I have to say this is how they do it in most of Europe. If you decide on this option make sure you get the fully modulating type as some of the cheaper units are not fully modulating and therefore not as energy efficient.

So open up those supply vents so you don’t create new problems with your HVAC system. Unless of course the system is more than 30 years old but then again I would caution against restricting the airflow on any given type of system even if it is ancient.

High Performance HVAC

Supply Vent Myth – Does Closing Supply Vents Save?


Air Conditioner Causes Water Damage


Air Conditioner Causes Water Damage

Air Conditioner Causes Water DamageAir Conditioner Causes Water Damage Question – Hello, We need to ask you about water damage and how an air conditioner can cause this kind of damage. The whole ceiling in one of rental properties just fell into the living room. All the drywall and insulation from the attic fell and caused damage to our tenants furniture. Thank God the tenants were not at home and injured when the ceiling fell in. The insurance adjuster came out and looked at it and said the problem was because the filter was clogged and air conditioner froze up inside the air handler. When the air conditioner turned off the ice melted and overflowed the pan. It continued to slowly overflow the pan for a few hours until the ice completely melted. The water logged the drywall in the ceiling until it eventually fell in and caused the damage it caused. The insurance adjuster seemed to be very knowledgeable about things like this and I was wondering if a dirty filter could cause such a problem and make the air conditioner ice up? We look forward to your answer. Thanks, Val


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Replace HVAC Compressor for Air Conditioner Repair


Replace HVAC Compressor for Air Conditioner Repair Decision | HVAC Refrigeration Question

Replace HVAC Compressor for Air Conditioner Repair – Question – Richard – I am an HVAC technician and have read all of your articles on refrigeration and compressors. Great information and it has helped to hone my skills and offer better service for my customers. Thanks! I was wondering what your experience is with replacing compressors. How do you arrive at the decision to replace a compressor technically speaking of course? Do you recommend repairing the air conditioner by replacing the compressor or replacing the central air conditioner? I look forward to reading your answer. Brett Des Moines, WA


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Air Conditioner Condensing Unit Frozen | AC Repair


Air Conditioner Condensing Unit Frozen | AC Repair

Richard – Early last month we turned our air conditioner on and it worked fine for a few days. Then I noticed it was getting a little warm in the house so I went around and checked the Air Conditioner.

Air Conditioner Condensing Unit Frozen | HVAC Troubleshooting

Old Condenser

Of course I checked the thermostat first and then the air filter. I went up into the attic to look at the air handler. I did not notice anything out of the ordinary that I am not used to seeing but I am not an expert. Then I went out to the the condensing unit on the back patio and I saw some ice inside the condensing unit. The compressor and the all the pipes connecting to the compressor were a block of ice and frozen solid. I turned everything off and called the HVAC contractor I am used to dealing with. They told me they would send someone out to take care of it. A few hours after making the call I got a call from the technician. He told me there probably very little he could do for me now as we would have to let the ice melt before he could properly troubleshoot the problem. We agreed for him to come the next morning to check it out. He told us to leave the air handler blower fan on but make sure the condenser was off. He told me to go to the breaker box and turn the condensing unit off and use the thermostat for Fan Only operation. We did exactly as he said.


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MONDAY, May 25, 2015

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