FAQs on repairing Indoor air handler or blower unit for A/C or heat pump or furnace systems, set #2:

More Q&A on AHU or air handler unit / blower unit troubleshooting and repairs.

This article series explains how to inspect & repair the indoor components of air conditioners and heat pumps: the air conditioning system indoor air handler units, blower units, or AHU's, (also called fan coil units) including the air conditioner blower fan, the indoor cooling coil or "evaporator coil", air conditioning system filters, and the causes, cures, and prevention of air handler leaks that lead to rust, damage, and mold contamination in the air conditioning system.

Air Handler / Blower Unit Diagnostic FAQs 4

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These questions & answers were posted originally

at AIR HANDLER / BLOWER UNITS - home - be sure to see the diagnostic help given there.

Article Contents

• AIR HANDLER / BLOWER UNIT FAQS
  • AIR HANDLER / BLOWER UNIT FAN REPAIR FAQs - too slow, too fast, other
  • AIR HANDLER / BLOWER UNIT REPAIR vs REPLACE FAQs - replace the evaporator coil, replace the whole unit?
  • AIR HANDLER / BLOWER UNIT WON'T START FAQs - or won't keep running
  • AIR HANDLER / BLOWER UNIT WON'T STOP FAQs  - also see FURNACE or AC BLOWER FAN WONT STOP FAQs
  • OTHER AHU BLOWER FAQs - below on this page, consolidation in process

Air Handler Noise FAQs

Rattling noise in attic air handler

I have a brand new Lennox a.c. And handler installed. The handler located in the attic rattles why On 2019-09-14 by Rocco

by (mod) -

Roc

Rattles at the air handler unit can be as trivial as an inspection door not latched, loose hardware, loose duct connections, or as troublesome as a blower motor that's failing with bad bearings. You need to ask your service tech to take a closer look. Tell us what you're told by the tech and we may be able to comment further.

Also either search InspectApedia.com (using the search box just above OR in the ARTICLE INDEX just above see HVAC NOISE DESCRIPTIONS for a complete diagnostic procedure for just about every noise type.

Air Handler Blower Fan Run Direction FAQs

Rheem Air handler blower fan run direction keeps switch backward & forward

Hi I have a Rheem air conditioner 2014 year. The air handler comes on and then immediately stops and goes back and forth each direction everything seems to be working except fan it does the same when put on just fan on any help would be appreciated On 2019-02-16 by Dave

by (mod) - Air handler blower fan runs backwards - causes, effects

A fan that is reversing and running backwards can be caused by a power surge that damages a control board or relay or on occasion even the motor itself.

On systems that require cooling by a fan such as the outdoor condenser unit, a backwards-running fan will also permit overheating - the system may shut down on thermal overload.

On indoor air handlers a backwards running fan or a squirrel cage blower that's mounted backwards will mean weak air flow through the duct system.

More details are at ELECTRIC MOTOR RUN DIRECTION - backwards

by Dave

It doesn’t run backwards but 1/4 turn then goes other direction and keeps doing that never spinning I did replace board with exact same one no different

by (mod) -

Possibly the fan is mis-wired or a dip switch set incorrectly but I'd belooking first for a loose wiring connection or control board connector or even a bad control board fan circuit or contactor/relay.

Also you'll see in the article problems with run direction related to a bad start/run capacitor.

by Eric W

Dan, I’ll check what you said. The thing that is baffling is why it turns on when a length of wire is attached to just the red wire and the other end isn’t connected to anything.

It’s not completing the circuit so it can’t be shorting out on anything and when that length is disconnected the fan won’t turn on.

by (mod) - fan runs with control wires disconnected

That's crazy. We must be missing something. What the heck? Electromagnetic fields?

More likely we're wiggling something on a control, connector, or board;

Air Conditioner / Heat Pump System Odor FAQs

On 2018-11-06 by George A/C smells like dust - very irritating

Air-Handler appears to be very clean - have professional maintenance twice a year and have 3" pleated filters - however, twice a year (spring and fall) the smell from the air-handler after using the heat and the next day requiring A/C smells like dust - very irritating - A/C company says it is a microscopic build up on the coils -

it goes away once we use either the Heating or Cooling on a consistent basis but is always there during the switch over weeks in Spring and Fall - what can be done to control this??? A/C company claims that they have new coil materials that stop this - but why pay for a coil change out - any thoughts???

On 2018-11-06 by (mod) - cleaning the blower unit

George,

What you are being told is consistent with my experience.

You would need to have the coils cleaned before turning on your air handler after a period of dis-use if you want to avoid the initial dusty odor and if you don't want the (costly) change-out to a dust resistant evaporator coil.

I'd also have the tech check the cleanliness of the squirrel cage blower fan itself. A small amount of dust on the blades can significantly reduce airflow, increasing system operating costs for both heating and cooling.

In addition, that dust, if it's normal house-dust, contains organic material including skin cells and some fabric fibers that, in the presence of moisture, can support mold growth that might also contribute to odors.

There are UV systems that can knock down biological materials on air handler surfaces that may also reduce odors but I don't recommend that in your case as you're complaining about what sounds like normal house dust odors.

If you can obtain the name of the dust-resistant coil products your tech has in mind I'd be glad to do further research.

FYI, experts like Siegel (2002) assert that dirt on coils makes a less than 10% reduction in air flow, while noting that "in extreme conditions" the effects may be much more significant.

In my nearly 50 years of inspecting air handlers and blowers and participating in the cleaning of some of them, I have seen an enormous change in air flow rates following cleaning.

That has been on the particularly-dirty blower assemblies. But on a 15 or 20 year old AHU blower fan it is very common to see the curvature of the individual blades filled to nearly-flat by dust and debris.

The fan spins at the same old RPM but its ability to move air is, IMO, and only subjectively-determined, very significant.

Here's a list of cleaning topics to review with your technician as steps to reduce odors from the air handler:

1. Clean the AC evaporator coil itself

2. Clean the blower fan and blower fan compartment

3. Replace the air filter monthly for each month that the system is in use in heating or cooling

4. Consider improved filtration such as an electrostatic air cleaner and, if the air speed and blower an handle it, HEPA filtration

5. UV treatment (which I'm not recommending for your case)

6. Also inspect for any mis-handling of condensate such as dirty condensate tray or blocked or slow condensate drain that can splash or spray condensate downstream in the air handler - inviting mold growth

7. Check that the AHU air speeds and system sizing are correct; an over-sized fan, for example, may keep blowing condensate off of the cooling coil and downstream into the duct system

8. Inspect to confirm there have been no other floods or leaks into the duct system

9 Inspect the home for other odor sources or mold reservoirs that might, by being close to the air returns, pick up and send odors or mold through the building. (Search this site for ODOR DIAGNOSIS for details).

Siegel, Jeffrey, Iain Walker, and Max Sherman. "Dirty air conditioners: Energy implications of coil fouling." American Council for an Energy-Efficient Economy 529 14th Street N.W., Suite 600 Washington, D.C. 20045-1000 Phone: (202) 507-4000, Residential Buildings: Technologies, Design, Performance Analysis, and Building Industry Trends - 1.287 (2002).
[PDF] retrieved 2018/11/06, original source: aceee.org/files/proceedings/2002/data/papers/SS02_Panel1_Paper23.pdf

You can also get a copy here: inspectapedia.com/aircond/Dirty-Air-Handler-Blower-Effects-Siegel.pdf

by George - Trane has new alloy that resists air handler odors?

Thank you for your quick response - My units are Trane and the dealer claims that the metals are at fault for the smell during the change over period claiming they do not smell when completely wet or completely dry - says Trane has a new alloy for their indoor coils - can find nothing to substantiate this claim

On 2018-11-08 by (mod) - dirty sock smell or gym sock smell in air conditioning or heat pump systems

I have reviewed several Trane documents without finding reference to a new alloy - it would be most helpful if your dealer could point us both to an information source.

www.novellcustom.com/wp-content/uploads/2017/01/the-trane-difference.pdf - discusses using properly-selected metals to avoid corrosion problems, not odors

www.trane.com/Commercial/Uploads/Pdf/1028/coil-ts-2.pdf does not mention the word metal nor the word odor.

http://www.trane.com/WEBCACHE/AH/COILS%20(COIL)/SALES/COIL-SLB006-E4_01012014.PDF - discusses concerns with corrosion and vibration damage, does not mention odors.

Watch out: as I discussed earlier, some mold contaminants in HVAC systems, including in the ductwork, in the air handler, or on the cooling coil, can indeed produce unpleasant odors that include a variety of smells, some of which are described on occasion as "the smell of gym socks" or "the smell of dirty socks" - which in fact are mold odors.

Steps to reduce mold odors sometimes focus on trying to reduce mold growth in the system, using UV or using special coatings on the coil itself.

In my OPINION, while all of those steps are fine to take, they're band-aid approaches where what we want is to avoid mold growth in the HVAC system in the first place.

This problem was discussed in an industry publication: ACHR News on 13 March 2006

A New Solution Found for Dirty Sock Syndrome original source: ACHR News: https://www.achrnews.com/articles/97993-a-new-solution-found-for-dirty-sock-syndrome

A copy is also here: https://inspectapedia.com/aircond/Dirty-Sock-Odors-in-HVAC.pdf

Also see this paper on the effects of dirt in AHUs by Siegel

https://inspectapedia.com/aircond/Dirty-Air-Handler-Blower-Effects-Siegel.pdf

Compressor Rotation Error Code FAQs

On 2018-07-31 by John Compressor Fault: Rotation Error Message

My fault code keeps coming up with a rotation error

On 2018-07-31 by (mod) - Compressor Startup or Rotation Error Diagnostic Flowchart - Samsung Error Codes E461 and E467

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John,

Typically a "rotation error" pertains to an air conditioner compressor motor, and often the first diagnostic step is a power-on reset of the system.

But knowing not a shred of a microdot of information about your system, I am flying more blind than Mr. Magoo.

Start by looking at the compressor unit, note the brand name, then look at the data tag and note the model number and serial number. Then find the service manual for your specific model and there you will find a table of error codes and names as well as the recommended diagnosis and repair steps.

Or see MANUALS & PARTS GUIDES - HVAC https://inspectapedia.com/heat/HVAC_Manuals_Air_Conditioners_Boilers_Furnaces.php for help downloading the manual for your unit if you don't already have one.

Above is an EXAMPLE page diagnosing rotation error codes for certain Samsung split system AC models.

This flowchart helps diagnose Compressor Startup and Rotation Error Codes E461 and E467.

Adding: if your unit had a power surge or lightning strike a motor may be running backwards.

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Continue reading at BLOWER FAN OPERATION & TESTING - home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

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AIR HANDLER / BLOWER UNIT FAQs-4 at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to AIR CONDITIONING & HEAT PUMPS

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