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bbaker90
HVAC Wall Air Filter Question
bbaker90

During a recent semi-annual HVAC maintenance, the techs said we did not need the fiberglass filters at the wall since we have the electrostatic filters in the air handler in the attic. They stated that the fiberglass filters increase air drag on the unit motor(s) causing increased energy usage and shortening the life of the motor(s). Is this true? Of course, they also were trying to sell us on duct cleaning and a Knight Air ultraviolet cleaner (for $900). What is the truth? Is it time to find a new HVAC maintenance company?

dj1
Re: HVAC Wall Air Filter Question
dj1

A central A/C unit can run efficiently on one filter.

I use thin filters, placed in front of the blower, and replace them every month, when being used. I don't go for the thick filters or HEPA filters - they will shorten the life of the unit. I also don't believe in running the unit with a filthy filter - again, it will shorten the life of the unit.

About duct cleaning service: if your ducts are old, have holes, get clogged easily, have bad connectors and blow dirty air - a cleaning service would be a waste of money. You need to replace them. New flex ducts come wrapped with insulation and are easy to install.

bbaker90
Re: HVAC Wall Air Filter Question
bbaker90

Thank you. Our duct work is in very good shape and have read in the past that duct cleaning is a waste of money with good duct work. Sounds like clean the electrostatic filters in the air handler every month or two and not having the wall filters will be ok for the system, correct?

A. Spruce
Re: HVAC Wall Air Filter Question
A. Spruce

On duct cleaning, it is only necessary if your ducts are dirty. Do you have dirt tracks coming out of your vents? If so, then duct cleaning should be considered. If not, then I wouldn't worry too much about it. You can check your ducts yourself by removing the registers and looking inside, again, if full of dirt, time to clean, if not, don't bother. Dirty ducts come from not using or replacing filters frequently enough. Since you've got an electrostatic filter, you are probably ok, however, what is the condition of this unit? Is it ever cleaned, has it ever failed?

As for filters in the walls, IMHO it depends on the location, if your return air inlet is at the floor, then placing a thin mesh filter here will absolutely be beneficial by catching large debris before it can enter your system. If the return air is at the ceiling, then no filter is necessary. As DJ1 said, restricted air flow will affect performance and lifespan, however these mesh filters really offer no resistance, particularly if you change them as needed, which will depend on your environmental conditions. Also, electrostatic filters don't offer any resistance, so what little an auxiliary filter at the return inlet would have will be of no consequence.

IMHO, a good contractor doesn't try to sell you anything, whether you need it or not. Their job is to make recommendations based on their findings and your requests, and show you why. As for the UV unit, this is not something that is integral to the function of your system. UV is used to kill mold and bacteria and reduce allergens, if you do not have any of these issues, then you do not need a UV unit unless YOU want one. If it were me, I'd look for a new HVAC company.

Fencepost
Re: HVAC Wall Air Filter Question
Fencepost

The air resistance of a filter on the intake reduces the atmospheric pressure in the plenum, which reduces the load on the motor. A filter on the intake cannot overload a blower motor. However, if the airflow is reduced too much, the motor can overheat.

The air resistance of a filter on the output will increase the atmospheric pressure in the plenum, which increases the load on the motor. However, overloading the motor even with a completely blocked plenum is unlikely. What is more likely is that reduced airflow will lead to overheating of the motor.

Mastercarpentry
Re: HVAC Wall Air Filter Question
Mastercarpentry

Fencepost is on the money. I like a cheap filter at the return to catch larger debris and help silence the sound of airflow somewhat when the unit operates. It should rarely need changing as it's not going to collect much. Electrostatic filters are very good at filtering with minimal airflow restriction as long as you keep them cleaned.

I'm with all on you not likely needing the UV filter, but that 'sales pitch' alone may not be a good reason to dump an otherwise good and knowledgeable company, as the next one you try could be worse. I would speak to the company owner and see if that attitude came from the top or was just the service tech trying to 'score points' on their own. If the latter and a good company, the owner will make sure that does not happen again, to you or anyone else. If the owner tries to sell you on the UV filter too then it probably time for a new company.

Phil

HoustonRemodeler
Re: HVAC Wall Air Filter Question
HoustonRemodeler

Add one more vote for the blue, cheap, thin filters and replace them at the first of every month.

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