Monday, October 30, 2006

How Often Do We Need To Have Our Furnaces Cleaned

For those people who live in area's of the country that gets cold, it's time to think about your heating equipment. With the technology new furnaces have today there isn't much to do on them as far as setting them up for winter. In the old days (10 years ago and before) we were told to have our furnaces and boilers checked once a year. But now furnaces and boilers have electronics doing most of the work. There are only a couple of things that a service tech needs to do in today's furnaces and boilers as far as a "clean and check" goes.

The old days:

In the old days when a service man (politically correct term today is "service tech" this term started about 21 years ago) when out on a "clean and check," he had all kinds of things to do. First he pulled out all the burners and blew them out with co2, then he checked the heat exchanger for cracks using a mirror, then vacuumed up any dirt he found. He also changed the "thermocouple" (on a standing pilot, where the pilot flame burns all the time, the thermocouple tells the gas valve there is a pilot light, and it's ok to open, and start the heat sequence) on the "pilot light" and blew out the pilot light assembly to make sure it would burn clean and that the pilot flame was positioned correctly on the thermocouple, and on the burner pilot runner.

After that he pulled the blower, and if it was a belt drive blower, oiled the squirrel cage bearings, motor bearings, and checked the belt for cracks . On a "direct drive blower" all he had to do was just oil the bearings on the motor.

Now all the burners are cleaned and the heat exchanger has been checked for cracks and everything is back in place, including the blower.On to the next step.

Now, if the service man was worth his salt, he checks the most important part of the furnace, the "limit switch". There's a limit switch in every; gas, oil, electric, or propane furnace, or boiler. It's main function is to turn on the blower (usually 200') and shut it off (around 110 or 100' any cooler, and you would feel like there was a draft) and the most important job it has is to tell the "gas valve" to shut down the burners incase the blower fails. It keeps the furnace or boiler (boilers also have a "safety relief valve" like hot water heaters) from over heating and starting a fire.

What the better guys did was pull the blower wire off the limit switch and start the furnace burners. With the blower wire pulled off the limit switch, the blower can't start, and when the furnaces gets to about 200 degrees, the burners should shut off and not relight again until the furnaces cools and lowers it's temperature to about 140 degrees. Some guys just checked the limit switch by rotating the dial on the limit switch and blower settings until the burners shut off. I liked taking the wire off the limit switch and testing it that way because it was more real life working conditions in the event of blower failure.

One of the last things, and just as important as checking the limit switch, was to check the "flue pipe" to make sure it, or the chimney, hasn't been blocked by soot or birds. It wasn't uncommon to find dead birds in the flue. Some even made it into people's basements. This doesn't happen anymore with the new furnaces. And the very last thing that was done was to check for gas leaks.

Furnaces 10 years ago to the present:

Today's furnaces and boilers don't need the kind of attention from the service man like furnaces of the past did. On most modern furnaces all that needs to be checked is the "flame sensor". The furnaces of today pretty much watch themselves. The burners almost never get dirty now a days because they are working in a mostly closed (80 plus furnaces are not, but the 90's are) environment. The blower, gas valve, and all the safety controls (including the "limit switch" and "blower switch") are run by a circuit board. The blowers are all sealed now too. They don't even need to be oiled!

So how often do we want our furnaces and boilers checked?

That's a tough question. It all depends on the environment your furnace is running in. It your furnace or boiler is running in an environment that has a lot of dust or animal hair, then it mite be worth it to have your furnace checked once a year. If your furnace is running in a relatively clean environment, you can probably get away with 2 or 3 years of not having to have to spend the money to have a clean furnace checked.

Don't forget that these new furnaces shut down when they spot the slightest problem. Some tech guys feel the only real time for home owners to have their furnaces ( don't forget where're talking new furnaces not the old clunkers) checked, is when they don't start. They don't think the cost justifies what your getting in return.

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Removing Particles from Air-Conditioning Systems

Do you know that air-conditioning involves more than controlling the temperature of the air? For stringent climate control, the relative humidity, smells and dusts are also controlled.

Today's topic is on air conditioning filters. These are the tools to control dust particles from entering the air-conditioned space. "Dust" could be a misnomer when we enter into the world of cleanrooms. Even tobacco smoke and bacteria are particles that can be filtered off!

Prefilters

Having efficiencies ranging from 50% to 85%, prefilters are used for protection against accumulations of textile fibres and insects. They are ineffective in separating smoke, pollen and staining particles like soot, oil mist.

Those with efficiencies above 85% are able to collect pollen and have some limited effect against smoke and staining particles. These are used in dehumidification systems.

In textile industries, prefilters are used in air-conditioning systems to protect heat exchangers, humidifiers and fans. Window mounted air-conditioning units use them for protecting the evaporator coils. Those with 85% efficiencies are used to control dusts from entering food handling premises and kitchens.

Fine filters

Fine filters are those with efficiencies ranging from 40% to 98%. Those in the 90% to 98% range are very effective against staining particles like soot and oil mist. They are also very effective against bacteria.

Their users includes air-conditioning for schools, kitchens, filing rooms, light engineering workshops, restaurants, and air curtains for food shops.

The higher ranges are suitable for operating theatres, laboratories, and computers.

Absolute filters

Absolute filters are the most efficient filters around with efficiencies ranging from 85% to more than 99.97%

They are highly efficient in collecting bacteria, radioactive dusts and all kinds of smoke and aerosols.

They are used for constant climate precision measurement or calibrating rooms, special clean air laboratories, operating theatres, sterilization rooms, and clean rooms.
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