Why Keep Coils and Filters Clean?

If I don’t keep the coils and filters clean, what can I expect?

  • Loss of cooling capacity.
  • Premature component failure.
  • Lack of humidity removal.
  • Compressor failures.
  • Higher than necessary electric bills.
  • Excessive repair bills.

Most modern air conditioners are operating under much higher tolerances than they did 20 years ago.  With emphasis being placed on higher operating efficiencies (known as S.E.E.R.’s), air conditioners are being asked to deliver the MAXIMUM amount of work for the LEAST amount of electrical consumption. Therefore, any deviation from the optimum field conditions can have a detrimental effect on the performance and life of the unit.

If you expect a high-efficiency air conditioner to perform for years, a small investment in preventative maintenance pays for itself — in lower electric bills, in repair costs, and in frustration.

Let’s look at operating cost. When components are dirty (coils, filters, etc.), motors and compressors have to work harder to deliver the air to the space or to condense the refrigerant.  This added work is expressed in higher amperage draw for the motors or compressors.  How does this effect your electric bill?  Let’s say, for example, that a unit running normally will draw approximately 20 amps in the cooling mode.  Now the condenser coil becomes dirty, which causes the compressor to work harder, increasing the amp draw by just 2 amps.  Under the principles of electricity:

                            AMPS × VOLTS = WATTS

The electric bill is based on KILOWATTS (1000 WATTS) consumed. Therefore, if you increase the amperage that the unit draws, you increase the watts consumed — no brainer?

Let’s look at a very simple example, not looking at cycling or S.E.E.R. ratings but just simple math. Let’s say the average unit operates at 230 volts nominal. Using the Ohm’s Law formula above, we multiply the 230 volts times the 20 Amp nominal draw, and we see that the unit will consume 4,600 watts or 4.6 kW.  Now increase the amp draw by just 2 amps and you have 230 volts times 22 amps which now consumes 5,060 watts or 5.06 kW or go one more to 230 volts times 25 amps and the unit consumes 5,750 watts or 5.75 kW.  From the original 4.6 kW, we are now operating at 5.75 kW  — that’s a lot of unnecessarily consumed electricity. Think of how much more it could cost if the amps increased 6 or 7 or more?  This can be a significant savings by just keeping coils and filters clean.

Now, say the average air conditioner runs 7 hours a day. If we use the formula:

                                      kWh = kW × hr

Then an air conditioner drawing 4.6 kW running 7 hours =32.2 kWh and the air conditioner at 5.75 kW running the same 7 hours = 40.25 kWh.  If your electric rate is $0.12 / kWh the first unit cost $3.86 / day to operate and the second unit costs $4.83.  That’s a dollar a day more because the unit was drawing just 5 amps more that the first unit.  This could still be within the unit’s operating range but, clearly the unit is working harder.  Now, if you take that out to 3 months — the difference in operating cost over the season is almost $100.00 more just because of dirty coils.

Now what about life expectancy of equipment?  When the amp draw increases, this means the components are working harder.  When a motor or compressor has to work harder, it is more apt to fail sooner.

I like to use examples to emphasize a point.  Think of your HEART as the compressor.  It is “pumping” fluid through your body just as a compressor ‘pumps’ refrigerant through an air conditioner.  If you keep “stressing” your heart, making it work harder than it has to. you can expect to eventually experience a HEART ATTACK or, worse, HEART FAILURE.  Likewise, if you keep “stressing” a compressor because the condenser coil is dirty or the filters are plugged, the compressor can also experience a FAILURE.

Hopefully, this has made the point why it is important to keep the coils and filters clean for your air conditioner.  This applies to both split systems and packaged units. It WILL reduce operating cost, it WILL prolong the life of the equipment, and it WILL reduce component failures and costly service calls.

Feel free to print this out and use as a sales tool to sell Maintenance Agreements to you customers.


About yorkcentraltechtalk

I have been in the HVAC industry most of my life. I worked 25 years for contractors on anything from residential to large commercial boilers and power burners. For the past 23+ years I had been employed by York International UPG Division ( a division of Johnson Controls) as a Technical support/Service Manager but I am now retired. One of my goals has always been to "educate" dealers and contractors. The reason for starting this blog was to share some knowledge, thoughts, ideas, etc with anyone who takes the time to read it. The contents of this blog are my own opinions, thoughts, experiences and should not be construed as those of Johnson Controls York UPG in any way. I hope you find this a help. I always welcome comments and suggestions for postings and will do my best to address any thoughts, questions, or topics you may want to hear about. Thanks for taking the time to read my postings! Mike Bishop
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One Response to Why Keep Coils and Filters Clean?

  1. Bruce Porter says:

    Trane did a study back in the sixties that a .0003 layer of fouling on the fin could cause a operational increase of up to 18%. That equates to operational resistance to electromotive force, as we all know when refrigerant gets hotter it expands so the energy requirement will go up exponentially. This means wear on bearings of the crankshaft ,rods, valves and everything associated with discharge of expanded refrigerant gas. The beautiful thing about the refrigeration cycle is; when it’s up, it’s up, Increase temperature, means expanded gas, means more amps, means higher discharge temperatures,higher compression ratios, means more superheat at compressor. It is a increase overall. When temps go down everything will go down. Keep it clean.

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