apperson energy management

                        MORE ON YOUR FURNACE FILTERS

The last couple of weeks we’ve been talking about the filter in your furnace. That rectangle of paper or fiberglass in a frame stretched across the airflow in your furnace plenum, which, if it’s doing it’s job, is causing chunks of debris to stick to it instead of passing on to clog the system or continue to exit a supply register and be breathed in by you. We covered the cheap “rock stopper” filters, and what a “MERV” rating is. If a person wants to go beyond the simple pleated paper filter and venture into an area where the sky is the limit as far as filtration power and spending, it can be done. The simplest filter after the pleated paper is known as the “electrostatic” filter. They can cost up to $200 and there are a number of types, but the common thread is the in the way it works. It captures dust by using the static electricity generated by the air moving through the filter media. The air passing over and around the material that makes up the filter puts a static charge on the filter material. This static charge attracts duct particles which are then held in place until the filter is taken down and washed. Some of these electrostatic filters are excellent because they create no drag or resistance on the system, however some designs create lots of drag and if not cleaned often can pose a problem of back pressure on the system when clogged with debris.
                                                    ELECTRONIC FILTERS

Next up on the filter line-up is the electronic filter. It’s pretty much the same as the electrostatic filter that works on static electricity, but this one comes with a plug which makes it a bit stronger. It has grids and you open it like a book. These get a bit pricier and run up to maybe $400, although some of the furnace manufacturers make proprietary models that filter and clean the air down to fractions of a micron and cost multiples of thousands of dollars and can be almost as large as the furnace itself.  And if you have trouble breathing they can be worth every penny. Some of these employ the well-known “HEPA” filter. HEPA stands for “High Efficiency Particulate Arrestance” and in order to be called a HEPA filter it must capture 99.97% of all particles down to .3 microns or less, 300 times smaller than a human hair. These filters are used in clean rooms and hospitals. You hear the term “HEPA” used all the time but it may not be used correctly. It takes a strong filter to really qualify as a HEPA filter. One very important thing about these high performance filters is the “stronger” the filtration, or the closer the weave of the media that catches or filters out the particulate matter, the less air can flow through that filter. Even with some of the better HEPA filters in new, clean condition your furnace can have a hard time sucking air past the filter. And then when you start getting particles trapped, which happens quickly with the stronger HEPA filters, the air pathways are blocked further and now your furnace has an even harder time getting air back to be reheated. 

So, it is very important, the higher the filtration, the more often you must clean or replace them. VERY IMPORTANT, I can’t say it enough. You can destroy a $5,000 piece of equipment by not changing a $5.00 filter. 

                                                 THE ULTRAVIOLET FILTER

Our last, most extreme example of “get the air you breathe clean filter” is the duct mounted, ultra-violet germ cooking air cleaner. This isn’t technically a filter because it doesn’t “filter” anything out but it does kill germs as they pass through the path of an ultra-violet beam of light in the duct. This is achieved using tiny mercury vapor lights and it can kill molds, virus, yeasts, funguses, and is especially beneficial to people who have asthma or respiratory illness or have a building with “sick building syndrome” All of the above were professed by the sellers of the systems. The UV light also cures or kills influenza, the common cold, snoring, nasal congestion, headaches, asthma, allergies, fatigue, depression, and studies have shown that people who have these in their duct systems have newfound energy!

So, I don’t know where the real benefits end and the hype begins. I’m kind of thinking that if the UV air cleaner really performed as advertised we would be seeing them in every home and business everywhere. A fairly simple system that just mounts right inside one of the ducts and it cures the common cold and asthma and gives you newfound pep and energy,  I think I would like to see some kind of proof before I spent the several hundred dollars it takes to buy and have one installed. And if the UV light kills that many germs where do the piles and piles of them go? Do they send someone around twice a year with a scoop shovel and a 55 gallon drum? Or do they get stuck in your filter, which you now have to replace weekly?  Food for thought, so to speak.

                                                  FURNACE  FILTERS

Last time out we were discussing the central furnace and the fact that if it has ductwork that air comes out of, then it will have a filter somewhere, and that filter will need to be changed or cleaned at regular intervals or the furnace will cease to function in a professional manner. You can either call an HVAC service tech and have them show you where the filter is located and how to change it or, if it’s just not something you want to do, you can enter into a “maintenance agreement” with the HVAC company and they will drop by at pre-arranged intervals and change the filter and make sure the other parts of the furnace are behaving.

So, on to the filters. Since I am not an expert in the field by any stretch, I thought I had better do a bit of research. I was amazed by the amount of information and different types of filters on the market. And unfortunately it is hard to distinguish between information and hype, but we shall try.

                                                    FILTERS BY MERV

According to the EPA we inhale something like 32,000 pints of air each day, which contain 1,120,000,000 dust particles of 3 microns or smaller. A human hair is about 70 microns for comparison. Our lungs are basically filters and filter about 2 gallons of air every two minutes. The EPA also says indoor air can be as much as 4-5 times more polluted than outside air with about 40 pounds of contaminates generated per 1,500 sq. ft. of building area per year, including about 40,000 dust mites. With our children being more susceptible to airborne problems than adults, we have a high incentive to want to filter the air we breathe. As we discussed, the “rock-stopper” fiberglass filter supplied with your furnace is put there to avoid damage to the furnace, not damage to you and yours. But if you remove that filter and don’t replace it you will be causing a problem. Dust and dirt will be allowed to build up on parts inside the units that aren’t supposed to have dirt built up on them, like the evaporator coil. It’s kind of like a car radiator and when clogged it will ice up and damage will occur. It won’t happen over night but it will happen. So replace the filter with a better one or at least go to one with a pleated surface. The pleats allow for more surface area which allows for more filtration area. What you are looking for in a filter is one that filters the air but doesn’t cause back pressure. It’s a delicate balance. The quality of the filtration is measured by the MERV rating of these simple pleated filters. This stands for “Minimum Efficiency Reporting Value” and was established by ASHRAE. The ratings range between 1 and 16 and the higher the number the better the filter. Most common are the 1 to 4 MERV filters which stop particles down to about 10 microns, then the 5 to 8 MERV range found in residential and commercial and filter to about 3 microns, then we have the high performance 9 to 12 MERV rated filters which are used in commercial and industrial applications and get down to 1-3 microns but must be changed very often or the systems will burn out, and the most effective are the 13 to 16 MERV for hospitals and clean rooms which get particles to .3 microns.

Most of the better filters in the above list will not work in the standard furnace systems you and I have in our homes. In order to get those high filtration ratings they must be thick. The filter slot that comes with your furnace will usually only handle a filter 1” wide and these high MERV filters can be up to 6” thick. You can use them but you first have to get a sheet metal guy to make an adaptor able to handle a filter that thick. And you have to make sure your furnace fan motor can handle bringing the air through that much more filtering material. It’s all possible but you have to ask the right questions first, not just stick some huge filter on the end of the duct and then sit back and wonder why the fan motor smokes. So, there’s some basic information on simple pleated filters and now you know what a MERV rating is. We’ll take this up again next time, there is still a lot of information on furnace filters.

                                    KEEPING ONESELF WARM

 Since the thermometer has taken it’s wintertime plunge into below freezing territory, it seemed like a good time to discuss that appliance in your home that keeps you comfortable and warm while all is frozen outside. While some households still rely on a wood fire for winter heat, and some may even have converted to wood pellets, the majority of us have a furnace of some type, with either a switch or a thermostat on the wall and the most thought we give to that piece of equipment is to decide whether or not it should be activated at any particular moment. For most of us the furnace is like the refrigerator or your septic system, we just don’t think a lot about it until it doesn’t work and then we realize how important it is to us.

                                                      WHAT THEY RUN ON

The majority of furnaces here in our area are fired by natural gas, supplied by PG&E.  We also have quite a number that burn propane gas, in areas where PG&E has not yet run their lines, and some furnaces that heat using electrical resistance. My understanding of electrical resistance heating is you shove electricity through a wire that is actually a bit too small for the amount being shoved and the result is the wire gets hot in protest. That heat is then transferred to air which is supplied to each room in the home (if it’s a central system) or to just one room (if it’s a single room heater).

We also have a few oil burning central furnaces that run on diesel fuel. This type of furnace is very common in the Eastern part of the Country and uses the same diesel that you use in your SUV, except it comes to you dyed bright red. This is so you won’t be tempted to siphon it out of the furnace tank and into the SUV tank, since Hiway taxes are a major part of the cost at the auto pump, furnace diesel oil is cheaper than SUV diesel oil. The red dye not only announces itself immediately in the tank, but as legend has it,  all your engine parts become dyed bright red also. All things considered, diesel oil has more BTU’s per gallon than any other commonly used fuel. When we adjust for the different prices diesel still comes out to be the least expensive fuel, at this moment. Electrical resistance heating, of course, is the most expensive. And it’s not only the most expensive way to heat the air, it’s the most expensive way to heat water, and dinner, and wet clothes. It wasn’t too long ago that you got a little medallion to place next to your front door if you built an all electric home. 

But anyway back to the furnace, even though for the most part they just silently stand there and do their job they really do need some attention at regular intervals. And this is important stuff. If you are not mechanically inclined or too busy, make some calls and have someone do this for you, don’t just ignore the routine maintenance your furnace requires or you know it going to go out on the absolute coldest night, a Friday night of a four day weekend.

                                              WHAT A FURNACE NEEDS

The main thing for a central furnace is to change the filter. No matter which type of fuel yours uses, if it has air flowing through ducts then it has a filter somewhere that needs attention. When your furnace was installed it came with a cardboard frame with a thin piece of fiberglass stretched across it as a filter. You can see through it. These are known in the trade as “rock-stoppers”, and they are put in the airflow to protect the furnace from large particles (rocks), not your lungs from anything. Even though these filters don’t stop much, if left unattended over months or years they can become impacted to the point of causing harm to the furnace due to a lack of airflow. You know how you can visualize some kid sucking on a plugged straw until the top of his head dents in? Well that’s the kind of strain your furnace is under when it can’t pull enough operating air though a clogged filter. Even though that type of filter is not much good for filtering it’s better than nothing, and since they cost less than a dollar it would be considered unwise to let a $4,000 machine burn up it’s fan motor (dent it’s head in, so to speak) because a $.98 filter wasn’t replaced in a timely manner. There are many different kinds and types of filters and filtration systems for a central FAU. Next time we’ll discuss some of them. We’ll look at media filters, HEPA filters, MERV ratings, UV filters, charcoal filters and others. In the mean time walk over and take out the old fiberglass filter, take it to anywhere that sells building supplies, and get several replacements. If you can’t handle it call one of our local HVAC companies and they’ll do it for you, but they will have to charge you because it takes a couple hours of their time counting there and back.