While I’m not an air conditioner tech, I can check the basics of an air conditioning system (air filter, blown fuses, ice build-up, etc).  The skill comes in handy when you contact an HVAC technician. It’s much better to be able to tell them, “I’ve got ice built up on the inside unit” than to simply say, “It’s starting to get hot in the house.”  They’ll be able to give you some potential causes of the problem and expected costs for repair.

So I started checking what I knew to check. Step one was to pull out the air filter, which was soaking wet and was stuck on something inside the unit.  In fact, it was so stuck it wouldn’t come free and I thought continuing to struggle with it might rip it apart.  I decided to open the upper access panel that houses the interior air coil and here’s what I saw.  Problem identified.

We’re no stranger to frozen outdoor air conditioner compressors. In the Winter, it’s not uncommon for an outside compressor unit to freeze up if the defrost cycle on the unit is set to run too infrequently. Freeze-up can also take place if freezing rain or snow accumulates on the fan blades, or is allowed to sit on the exterior of the unit.  Fixing an outdoor frozen heat pump can be as easy as setting the defrost cycle to run a little more frequently, which did the trick for us.

Of course, in the Summer the situation is reversed. The system extracts heat from the inside of the house and moves it outside. In this scenario, the air coils inside the interior air handler get very cold, with evaporated freon moving through them.  Air passes over these coils and most of the time, you get cool air conditioning in your home.

Cause of Ice Frozen Air Conditioner Air Handler

So what causes an interior air handler to freeze up instead of operating normally?

There are two common causes for freeze-up, and one is less expensive to fix than the other.  The first cause is a freon leak in the system. When a freon leak is present, the coils can cool unevenly with some parts of the coil staying extremely cold for a long time.  This leads to build-up of ice on the coil from the moisture extracted from humid air passing over it.  Once the ice starts to build up, it easily persists because it acts as an insulator on the coil, preventing air from passing over the coil and warming it up.

The second cause is poor air flow over the coils and fins, usually caused by an extremely dirty air filter or dirt build up on the coils or fins.  When air flow is restricted, the coils and fins become too cold leading to ice build up.

Since we had just finished that hardwood project, we figured the dust blown around in the house was probably the culprit, and at least worth checking before making a call to the technician.

How to Fix a Frozen Air Handler

The easiest way to melt the ice is to allow the fan to run without the air conditioning on for 24-48 hours.  You must let ALL the ice melt before turning the A/C back on, otherwise the problem will quickly return.

Unfortunately, we were in the middle of a terrible heat wave and didn’t want to wait 24 hours for a solution. So we used the faster method: a hair dryer and two 500-watt halogen lights. The process took 2 hours to get the air handler completely dry.

Note: You should always turn off the breaker to the HVAC unit before working on it.  Also, using a hair dryer and/or heat lights could be a fire risk if you aren’t careful.  So be careful and do this at your own risk!

It is imperative that you don’t disturb or break the coils inside the unit.  One broken coil will mean a much more expensive fix.

The unit dried:

We turned the unit back on and nearly instantly the cold air came rushing through the house.

In the three weeks since the event, we’ve had no recurrence.  It looks like the air filter did the trick, saving an expensive HVAC technician call and confirming that we probably do not have a freon leak. Had the unit frozen back up, we would’ve called our favorite Baltimore County air conditioning contractor to come take a look.

Last year, I wrote about fixing the ice-frozen outside compressor unit for our heat pump.  This winter has been record-breaking for precipitation here in Maryland, however, so I found I needed to readdress the issue with our HVAC guy.  What I learned?  I can adjust the frequency of the compressor’s defrost cycle on my own to keep up with whatever Nature sends us.

With all the freezing rain and snow we’ve experienced this fall and winter, our compressor’s defroster just wasn’t keeping up.  Turns out, it was set to run only every 90 minutes of running time.  An energy-efficient setting, but not frequent enough for this year’s weather. 

Mike showed me where to adjust the settings inside the removeable side-panel on the outside unit.  Yours should look much the same.

We moved the white clip from the 90 minute setting to 50.  If that turns out not to be frequent enough, we will move it to 30 minutes, but so far we seem to be doing fine with 50.

So depending on where you’re living, how cold it is, how much precipitation you’re getting in the cold weather, and where your outside unit sits (ours is under our deck – never directly in the sunlight!) you can adjust your defroster settings accordingly.  For those living in the southern U.S., you should be fine with the 90 minute setting.  Our friends in Canada and the northern U.S. states may need it to run every 30 minutes in the winter.

Note that the settings are how often the defroster kicks on during system run-time.  So if your compressor runs for 10 minutes, turns off for a half an hour, then runs again for 15 minutes, that’s 25 minutes of run-time, even though 55 minutes have elapsed.  Ours was going a few hours before it had run for the requisite 90 minutes to engage the defroster and that was too infrequent for our unit this winter.

Running the defroster does, of course, use extra energy, so you don’t want it to run more frequently than you need it.  That’s why we dropped to every 50 minutes rather than jumping straight to a defrost cycle of every 30 minutes of run-time.  Should we have a really mild winter again in the future (as we have most years in the past), I may move the setting back to 90 minutes.  But for this year, it’s not worth the risk of damaging the unit (ice-chunks building up and causing damage to the spinning fan blades and subsequently to the motor) just to save a few cents in energy cost each week. 

Hope this is helpful to someone else out there!  It’s a quick and free first-resort solution for dealing with an iced-over unit that otherwise is in good working condition (and can help trouble-shoot before you call an HVAC repair person and pay for a visit).

Recall that last year our basement was entirely uninsulated. The only thing between us and the elements were cinder blocks with basement waterproof sealer applied to them.

Our first floor flooring was freezing, and the entire house was drafty. Ultimately, we selected closed cell spray foam from a variety of basement wall insulation options.

We had a local spray foam contractor install the insulation and our subjective experience since then has been great. (In fact, the basement is now the warmest room in our house). Until now, we didn’t have any objective proof that the investment was worth it.

Now we do.

This energy bill confirms our subjective experience with facts. Take a look (click the picture to enlarge and make the numbers legible)…

Energy Savings Analysis

Last January (2009), you can see that our average energy use for the house was a whopping 146.6 KWh / day! This January (2010), our energy use drops to an average of 97.7 KWh / day. This represents about a 33% energy savings, despite the fact that this year’s daily temperature average was 1 degree colder.

Our house is in approximately the same shape as last year, with the same number of people living in it. There are a few differences in the house:

• Last year, we had a large aquarium that we also heated throughout the Winter. While the heat from that aquarium ultimately leaked back into the room, there would still be some increased cost. Our estimate is that the aquarium used approximately $25 / month in energy.
• This year, we’ve been using the fireplace almost every night. Fireplaces are notoriously energy inefficient. They steal heat from a house at a rate much higher than they add back with radiant heat. We still like to look at the fire, though, and we’re willing to pay for for the privilege. I estimate we’ve been losing about $10-$20 / month in energy to the fireplace.

Other than these two differences, the house is in approximately the same shape as last year, with the same number of inhabitants. In other words, we think the bulk of the 33% savings is directly attributable to the spray foam insulation.

Tax Savings for Spray Foam Insulation

The best part: 30% of the cost of the insulation material will be refunded to us this year through the U.S. Government’s tax credits for energy program.

This makes our payback period for the insulation less than 3 years, and potentially even less than 24 months, depending on how the foam performs in the Winter.

Rick, Sounds like you’re trying to install a single stage programmable thermostat instead of a two-stage. Without any additional information, I would assume you have an air conditioner & heat-pump system with an auxiliary emergency heat electric furnace back-up system. Your current thermostat is designed to allow independent control of the outside heat pump and the inside auxiliary furnace (two stage on the heat side). This setup saves money by using only the outside heat pump unit when the temperatures are milder, but ensures you have a warm house when the outside unit can’t keep up with the cold temperatures.  Here’s what the wire labels are on your existing t-stat:

• R – Hot side of transformer.
• C – Common side of transformer.
• W1 / Y1 – Heat / Cool Stage 1 (jumper since you have a heat pump that can both heat and cool).
• W2 – Heat Stage 2 (inside furnace).
• G – Fan on/off.
• O/B – Energize to cool (controls the reversing valve).
• E – Electric Heat Override

The thermostat you purchased is designed for a single stage system (such as an air conditioner and a single-stage gas furnace). The E and W2 hook-ups are for the emergency heat relay and auxiliary heat control, respectively. The new thermostat doesn’t have these because it isn’t designed for this type of installation.

Without additional information, the best solution is to purchase a thermostat designed for your HVAC system–likely a two stage on the heating side (or in some districts your utility will provide you a thermostat for free). You should be able to check the manual that comes with the inside unit and select a thermostat using that. Be aware, different manufacturers use the same wiring ID labels to mean different things (e.g., in your picture you can see that some of the terminals have multiple labels for multiple system types). Be sure you are following the wiring diagram for your system.  Of course, you can always call an HVAC repair technician for help.

Either way, it is a great time of year to clean your heat pump’s coils in preparation for the winter. You’ll get better performance from your system all winter long . Coupled with a thermostat upgrade, you’ll be all set.  Thanks for the question. Cheers!

Electric Baseboard Heating Systems

Electric baseboard heating systems generate heat resistively, by heating up wire coils inside the unit and radiating the heat out using a reflective coating on the inside of the unit. Baseboard systems come in a variety of wattages and lengths to suit just about any wall space.  In general, they benefit from the following advantages:

Advantages of Baseboard Heaters

• Can be installed anytime on any open wall.
• Depending on wiring, may be able to run on existing circuit.
• Relatively inexpensive installation ($25-$70 per unit), especially if no electrician is required for an additional circuit.
• Suitable for all types of flooring installation, including high-insulation floors such as high-pile carpet.
• Easy DIY installation.

Disadvantages of Baseboard Heaters:

• Heat can be blocked / uneven depending on furniture placement in the room.
• Unsightly heaters lining the walls of a room.
• Hazard for pets and children who could be burned by the unit.

Electric Radiant Floor Heating

Electric radiant floor heating systems are wire mesh eletrical wires installed beneath the surface of the floor.  Due to their built-in nature, they must be planned with the original design of the room. They always require dedicated eletric circuits.

Advantages of Electric Radiant Floor Heating

• Even distribution of heat throughout an entire room, reducing overall energy costs.
• More comfortable, even heating.
• No visible heating source in the room (heating is fully concealed).
• Heats from the floor-up; making it an excellent choice for basement installations where a cold floor is a disadvantage, like in basements and bathrooms.

Disadvantages of Radiant Heating:

• Some electric radiant floor systems will limit furniture placement by requiring low R-value surfaces to avoid damaging the heating wire (e.g., no solid-base furniture can be installed on some systems).
• High installation cost (as much as $12/ sq. ft., or about $6/sq ft. for DIY installation).
• Limited floor surfaces.  (Carpet is not an option.  Tile and wood are OK, but will dictate differing systems).
• Moderate / hard DIY installation.

What do you think? If you were designing a new room, would you put in baseboard or radiant floor heat?

Most homes feature ductwork to deliver conditioned air throughout the house. Energy Star states that leaky ductwork can account for up to 30% of a homes total heating and cooling costs. There are several different ways to seal ductwork, but applying mastic is the best option.

Benefits of Sealing with Mastic

Mastic is a gummy adhesive. It will stick to just about anything making it easy to apply. It dries solid, forming an airtight seal over gaps and holes, but can still bend and flex as ductwork expands or contracts. Unlike foil tape which can loose its hold over time, mastic will stay fixed in place.

Recommended Mastic

Not all mastics are the same. I suggest using a water-based mastic as they release less fumes. Look for the UL-181 seal of approval. These mastics are more flexible, longer lasting, and adhere to ducts better. Choose a mastic that is reinforced with fiberglass for additional strength. Also look for water resistance, a low flame spread and a low smoke-develop rating.

Where to Apply Mastic

The short answer to this question is wherever air is escaping. Feel around ductwork while your HVAC system is active to find leaks. Here are some specific areas you should target:

• Transitions - Wherever one piece of ductwork is butted up against another. This can occur when ductwork changes size or shape, but there may also be in-line transitions. Also, check out any flexible duct connections.
• HVAC unit – Big culprits here are where the indoor coil connects to the furnace and/or ductwork. Look for leaks around freon lines and wiring. Don’t mastic any access panels – use foil tape instead.
• Register boot – Ductwork often turns a sharp corner just before terminating at a register. These are common problem areas.

How to Apply Mastic

Begin by inspecting your duct work. Make sure everything is secured and fix any poor connections. For large gaps, you may need to secure sheet metal with self-tapping screws and then mastic the seams. The mastic should fully cure in about 24 hours.

• Wipe the duct clean before applying. Dust and dirt can prevent the mastic from creating a strong seal.
• Apply the mastic with your hand, paintbrush or trowel. Choose whatever is most convenient for you but be careful of sharp edges and corners. Wear heavy gloves to protect your hands.
• Use enough mastic to create a continuous coating with a ½″ overlap around any hole or joint. Lightly work the mastic into cracks and joints. You don’t need a very thick coating, just enough to fill all gaps.
• Mesh tape is useful for reinforcing areas with gaps between ¼” - ½” and joints. It’s applied much like drywall tape.  Make sure the tape is compatible with the mastic you have selected.

What do you think? What tips can you offer for applying mastic?

Let me start by saying, this project is not for DIYers. There’s a lot of specialty equipment and specific know-how for properly managing freon. I know this task was beyond me, and recommend you find a reliable HVAC contractor for this job. If you’re looking for a contractor in the Baltimore area, I can pass along a name and number.

Installing a New Indoor AC Coil

The install began by trapping all the freon in my outside unit. Next came the demolition. Here’s a picture of my old HVAC setup.

This picture shows the front panels removed from the furnace and the old coil removed.

Here’s a picture looking down into the furnace.

The new coil was a different size, so they had to construct a ductwork seat that would account for the change. This picture shows them installing the ductwork reducer.

And here’s the new coil seated on top of the ductwork. Just about everything was secured with self-tapping sheet metal screws. An impact driver makes it easy to screw into sheet metal.

The new coil also features a front access panel. I was excited to learn that if I’m ever suspicious of my indoor coil, I can remove a few screws and take a look. You may not be able to see it very well, but the new coil also has a plastic drain pan (meaning it won’t rust). The new coil is seated level on the ductwork as the drain pan is already sloped to direct water toward the drain.

This picture shows the ductwork elbow that is installed above the new coil. This elbow is curved, rather than a sharp 90° angle. That’s beneficial because it helps keep air moving in the right direction.

Freon lines are flexible copper. This picture shows the new line connecting to the existing copper freon return.

Here’s another feature I was excited about. It’s a clear drain trap. Not only can I see if water is moving through it, but I can also use the brush to remove any clogs.

This is a picture of a freon filter. Whenever you cut freon lines, a filter should be installed to remove particulates.

And here’s a picture of the new indoor AC coil installed. Notice all the foil tape to help prevent air loss.

What do you think? Ever replace your indoor AC coil?

Diagram of Indoor HVAC System

It’s important to understand the different parts of your HVAC system before you begin poking around. You don’t want to accidentally make any problems worse. Here’s a labeled picture mapping out the main parts, using my HVAC system as an example. Arrows indicated the direction of flow.

Air flows from the house into the air return. This air travels past burners (to heat air in colder months) and an indoor air-conditioning coil (to cool air during warmer months), then back out through duct-work to different parts of your home. My home features a gas furnace and has gas supply lines. Electric heaters won’t have these gas lines.

Water Pooling from HVAC

You can see in the picture a small pool of water on the concrete slab just in from of the furnace. It’s not much water but after removing the front access panels I could see more water leading all the way up to the indoor AC coil. I speculated that the leak was condensation that wasn’t making it out through the drainage pipe.

Fix a Clogged HVAC Drainage Pipe

Most HVAC issues are not really within the realm of most do-it-yourselfers and I strongly recommend hiring a contractor. Better yet, make a friend in the HVAC business. These are the steps I followed with the help of a buddy.

• Open up any access panels and check internal drainage lines. They are probably flexible tubing with plastic collars securing them in place. Makes sure all the lines are well-connected and feel around for any drips. If you don’t find anything amiss, you may have a clogged drainage pipe.
• Your drainage pipe is probably PVC. Setup a pan below and cut the line. Make a smooth, clean cut in a place that you can repair later. Straight-aways are best because you can glue a PVC sleeve around both sides restoring the line.
• Examine what (if anything) comes out. If water rushes out, the clog may be farther down. You can attempt to “snake” the line or swap it out. PVC is inexpensive making it easy to simply replace the rest of your drainage line.
• In my case, a small trickle of water came out, meaning the clog was further up the line. We used a bent coat hanger to poke around and dislodge the clog. Be very careful not to damage your coil. The coat hanger worked well and a lot of water poured out.
• I love using my flexible fiberscope and this was a perfect opportunity. I fed the scope in and looked around. We discovered a lot of rust! Small chunks were actually clogging the drainage line causing water to pool (and ultimately find another way out).

Indoor Air Conditioning Coil Drainage Pan

Your indoor air conditioning coil sits on an angled pan. This pan collects condensation and directs it to the drainage line. Gravity takes effect and the water goes about it’s merry way. Over time, my pan lost it’s angle allowing water to pool. It still drained but only when the water level got high enough. This went on long enough for my coil to rust and ultimately cause the clog.

What do you think? Ever work on your HVAC system?

Solar or Electric Attic Fan?

In the original article, I wrote that solar attic fans were more costly up front ($300-500), while electric versions were much less ($150-200). Solar versions tend to move less air because they run at low power.  To sum up what we said, here’s a quote from the other article:

There are several varieties of attic fans including solar and electric varities.  As a general rule, solar fans operate at a lower wattage and thus can’t cool as much area.  Check the CFM and appropriate square footage rating on the fan.  If you already have electric in the attic, we recommend installing an electric fan.  It will run much faster, and its cheaper.  If you decide to go with a solar fan, make sure you will get sufficient air flow.  It may be a waste of your investment if you don’t.  Consider running electric if you don’t have it to avoid the solar option.

Peter (a commenter) argues that the solar attic fan is actually cheaper.  His analysis:

Hi Fred,

Here’s a rough payback calculation:

A top of the line 1300 cfm solar attic fan will run you around $600, installation (no electrician required) another $300, so total installed cost is $900 minus your $270 Federal tax credit = $630 out of pocket cost.

An electric attic fan of similar capacity will cost around $125, installation $400, so the total installed cost = $525 out of pocket.

First cost differential: Electric fan is $105 less expensive.

Solar fan is free to run.

Electric fan uses 0.5 kw per hour of operation. If electricity is $0.12/kw-h, cost to run the fan is $.06 per hour.

So the electric fan will run for 1,750 hours on $105 worth of electricity. Say the fan runs only when the solar attic fan would run, 6 hours a day. The breakeven point or payback period is 292 days!

While I think Peter is good natured (and perhaps making some bucks off of solar attic fans), this analysis strikes me as misleading.

Energy Use: Solar vs. Electric Comparison

Most premium solar attic fans run 10 or 20 watt motors.  We’ll say 20 watts to get the 1300 cfm Peter claims in his example. Peter argues that an electric fan will be require .5 KW (or 500 watts). It simply doesn’t make sense that a 20 watt solar-powered fan moves anywhere close to as much air as a 500 watt fan. A more fair comparison would be to assume the 20 watts produced by the solar panel had to instead be drawn from the grid… a 20 watt vs. 20 watt comparison.

At 20 watts, assuming 14 hours of use each day, that’s .02 KW * 14 hours = .28 KWh per day. At $0.12/KWh, that’s about $.04 / day. Assuming the break even point happens at $105 as in Peter’s example (we think that part of his analysis is correct), that gives us 2,625 days. Assuming the attic fan would run only 5 months (155 days) out of the year–generous, actually, because it would probably only run for 3.5 months–the payback period is an astounding 17 years… much longer than Peter’s claimed 292 days (which would be about 3 years since the fan only runs in the Summer).

Now, most electric fans will run a higher wattage that 20, but they will also move more air, and thus do a better job of cooling.  Variable speed fans may be adjustable down to a 20 watt consumption level which would make our analysis valid.

Which is Greener?

Of course, one could argue that by using solar energy to save electric energy is better for the environment.  This may be true, but its also hard to know whether you could actually save more electricity by installing an electric fan…  In our estimation, there’s too many variables to make a good prediction on which is better for the environment.

The Bottom Line on Solar Attic Fans

In our view, solar attic fans just don’t make sense.  Are we missing something?

(photo credit: muffet)

Attic Fans vs. Whole House Fans

As Todd notes in his article, an attic fan is different from a whole house fan.  A whole house fan is normally installed in the ceiling of the topmost floor of the house, between the topmost floor and the attic.  While an attic fan only circulates air in and out of the attic, a whole house fan pulls air through the house and out of the attic.  This essentially creates a draft throughout the house.  Air enters the house through open windows, wall cracks, outlets, and other places, and leaves the house through the attic fan which blows the air up and out.  A whole house fan creates an artificial chimney effect in the house that cools it down.

Whole house fans are great in climates where you don’t need to use air conditioning.  If you use air conditioning, a whole house fan will waste the energy by pumping the A/C out of the roof of the home.  Whole house fans and air conditioning should not be run together.

Why Attic Fans Work

In the Summertime, the attic can heat up to 40-60 degrees hotter than the ambient outside temperature.  In extremely hot climates, this means that an attic could reach 160 degrees F.  This heat is transferred to the house via radiation (heat energy transferred as electrmagnetic waves), and convection (heat energy transferred as the hot air contacts the insulation and other ceiling materials).

An attic fan can reduce the temperature of the attic by as much as 40 degrees F or more.  If an air conditioner is trying to keep the house at 75 degrees F, a reduction of 40 degrees in the attic may save as much as 30% off the energy required to cool a second floor, while requiring only a fraction of that energy to run itself.  Plus, it will keep the second floor feeling much cooler than may otherwise be possible.

Solar Attic Fans vs Electric Attic Fans

There are several varieties of attic fans including solar and electric varities.  As a general rule, solar fans operate at a lower wattage and thus can’t cool as much area.  Check the CFM and appropriate square footage rating on the fan.  If you already have electric in the attic, we recommend installing an electric fan.  It will run much faster, and its cheaper.  If you decide to go with a solar fan, make sure you will get sufficient air flow.  It may be a waste of your investment if you don’t.  Consider running electric if you don’t have it to avoid the solar option.

Attic Fans Extend Roof Shingle Life

Attic fans can also increase the life of the shingles on your roof by preventing cracking damage due to extreme heat and cold cycles.  By reducing the extreme temperatures, shingles can last up to 20% longer on roofs with attic fans.  Since a 20% longer life equates to a 20% cost savings on roof replacement, an attic fan pays for itself when considering only this facet alone.

Avoid Roof Leaks During Installation

You may want to have an attic fan professionally installed, especially if you aren’t comfortable working on the roof.  During a typical shingle replacement is the best time to have a unit installed, but they can be installed anytime.  Make sure that the shingles overlap the base of the fan and that appropriate flashing is installed to avoid roof leaks around the fan.  Roofing mastic can be applied around any edge gap.  The fan will come with detailed installation instructions.  If you aren’t comfortable working on a roof, you’ll definitely want to pay for installation.

Attic Fans vs. More Insulation

One alternative to an attic fan is to add additional insultation.  The advantage of insulation is that it works in both the Summer and Winter, whereas an attic fan only benefits the homeowner in the Summer.  Each installation is unique, and so determining whether a fan or insulation is the better route is not always easy.  That said, an attic fan probably won’t be nearly as expensive to gain a lot of performance in the Summer.  If you’re attempting to “go green”, we suggest over-insulating and adding the ventilation fan.

Attic Ventilation Fan Cost & Pricing

Attic fans can run anywhere from $100-$500 dollars depending on the model.  Decent models command between $150-300, and may run quieter and last longer than their less expensive counterparts.  Solar attic fans will be on the high end of the spectrum (another reason to avoid the solar option if possible).

Attic Fans Running All the Time / Won’t Come On

Most attic fans are controlled by a temperature regulator and turn on and off automatically.  It is possible for an attic fan temperature probe to go bad and need replacement.  You should watch your attic fan on very hot days and make sure it is turning on when the sun is hitting the roof, and turns off during the evening.

What do you think? Have you installed an attic fan?  Will you?

(Photo: MaryTClark)