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Starting capacitors in place on an air conditioning compressor (C) InspectAPedia.comAir Conditioner / Heat Pump FAQs

INDEX to Q&A on air conditioner & heat pump inspection, installation,
Troubleshooting & Repair procedures,
Find parts, manuals & codes for A/C or Heat Pump Units

Questions & answers on how to buy, diagnose, repair air conditioners & heat pumps:

This air conditioner & heat pump inspection, installation, diagnosis & repair FAQ series lists questions & answers sorted by major air conditioning or heat pump topic.

Page top photo: a pair of start/run capacitors on the outdoor compressor/condenser unit of an air conditioning system.

This article series describes how to inspect and repair all types of residential air conditioning systems (A/C systems). Information for home buyers, owners, and home inspectors about A/C or heat pump system problems.

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Air Conditioning or Heat Pump System FAQs Master List

The questions and answers immediately below were posted originally

at AIR CONDITIONING & HEAT PUMP SYSTEMS - home. Be sure to see the recommended topics and articles given on that page.

Image: a Supco RLC051 "dry" trap for HVAC condensate lines can reduce clogging problems. We discuss this waterless trap as an alternative to P-traps in a reader Q&A below on this page.

Here we list all the HVAC A/C and heat pump FAQs ( often these pages also containing their own index to additional detail).

Article Contents


What's the Residential air conditioning industry construction standard for the supply duct downstream (i.e. located after) a refrigerant coil

What is the residential air conditioning industry construction standard for the supply duct downstream (i.e. located after) a refrigerant coil. ?

If there are flex ducts that are installed on top of the refrigerant coil, wouldn't that be an inappropriate location to achieve full airflow from the cooling coil? Commercial air handling units have at least 12" - 18" from the fan discharge to the opening of the supply ductwork. - On 2020-10-11 by AlexEnergy5

Reply by (mod) -

DUCT SYSTEM DESIGN SIZE & DEFECTS - home - includes in the references section of each of the pages in that article series, citations of codes and standards.

You're right that good HVAC duct design usually provides an adequate main trunk to give velocity and volume to the conditioned air before it's branched off into individual distribution lines. hvacsales.com says that

"... the minimum recommended plenum size would be -- width: 2 x 16 or 32 inches; length: 1 x 36 or 36 inches wide. The depth of the plenum is always the same depth as the supply trunk."

Can a Goodman AVPTC49c14 be installed in a doublewide mobile home"

Can a Goodman AVPTC49c14 be installed in a doublewide mobile home. - On 2020-06-11 by LISA

If so would anything have to be modified?

Reply by (mod) - check the manual: it MUST say "approved for mobile home use" or "approved for manufactured home use"

If a heater is not listed and approved for mobile home installation, modifying it would be unsafe.


Rusty bad ductwork blamed for failure to cool some rooms: what's the fix?

Badly rusted HVAC ductwork (C) InspectApedia.com Josh

Went into crawl space to investigate cause for two hot rooms. I found it.

Main supply duct has at least two large leaks and is quite rusty. I’m guessing the ducts weren’t replaced when the system was updated from swamp cooler.

The supply trunk that main sits on is sagging from weight as well. How do I fix this? New main supply and replace rusted trunks? - On 2018-12-16 by Josh

Reply by (mod) - Replace badly-rusted metal HVAC ductwork

Josh If my HVAC system had ducts in such poor condition, I'd replace them.

And I'd want to find and fix the sources of crawl space moisture to reduct the mold and other damage risks therein.

Followup by Josh

Thanks Dan, I work in the plumbing department of a MEP company.

Hoping the boys in AC can help me out as I have no clue about duct work.

Reply by (mod) -

Ok Josh. Keep me posted. Also I'd like to see photos of the duct interior.


Is there an ambient temp safety sensor to protect the compressor in cold weather?

Do any AC systems have an ambient temp safety sensor that wont allow to compressor to turn on below a preset outside temperature? - On 2018-11-10 by robinsoninspections @gmail.com

Reply by (mod) - Yes, for example the SUPCO freeze protection switch, opens at 35 degF.

SUPCO Sealed Units Part Company Freeze Protection Controller 35 degF retails for about $20. USD. - shown at Inspectapedia.com (we do not sell anything) and available from HVACR suppliers or from SUPCORob

Heat pumps use outdoor temperature sensors for several purposes including switching the compressor motor OFF and switching to backup heat mode if outdoor temperature falls below the safe (or efficient) operating temperature of the unit (typically around 25-30 degF for most units).

An air conditioner unit, that is one that ONLY provides cooling, again depending on age and model, may NOT have any such outdoor temperature controllers.

Such units should be left turned off in winter.

If some fool tries to turn on the air conditioning at the indoor thermostat and if the outdoor unit runs in freezing weather it might be damaged by liquid refrigerant slugging in the compressor.

THose AC units do often include a crankcase heater to prevent liquid refrigerant slugging; that's why we leave power to the unit ON for 24 hours before actually asking the compressor motor to run at lower outdoor temperatures.

There are also "freeze protection kits" from Amana, Goodman, Supco, and others that provide an outdoor temperature sensor and that prevent the compressor from running at low outdoor temperatures.

Those can be retro-fitted to an A/C (i.e. not a heat pump) if needed. There are similar protection devices that can be fitted at the indoor coil to detect coil icing or freezing in that location, like the Amana FSK-01A kit.

Shown above SUPCO freeze protection switch, opens at 35 degF.


Debris coming out of HVAC vents after ceiling leak

Insulation or ceiling tile blowing out of AC supply registers (C) InspectApedia..com PattiMy ceiling has been leaking for 3-4 months.

Housing Authority said they patched it.

Now when my air conditioner blows threw vents, pieces of ceiling tile, ( insulation) comes out & is blacken - On 2018-06-22 by Patti

Reply by (mod) -

Patti

I can't make an assessment from your note and photo, but certainly from what you describe there could be a risk that the air conditioning system is mold-contaminated and certainly there is damage somewhere if it's spitting out debris.

A more subtle but more dangerous problem can occur if debris is drawn right into the air handler or blower assembly where it could cause a jam-up, a blower motor overheat, and then a building fire.

You might pass on your concerns to your housing authority, in writing.

 

My air conditioner takes too long to cool down my condo. Why?

My HVAC is around 15 years old. I have lived in my condo for 3 years now, so I wasn't living here when it was installed. It always reached the set AC temperature within a few minutes and I always leave the thermostat on "auto".

Recently it started taking hours to reach the set temperature and until it reaches that temperature, it doesn't turn off and on even though it's set on auto. It does run cold though. I also recently had the capacitor replaced. I asked the technician who replaced the capacitor why it's doing that, but he just said I need a new HVAC and couldn't tell me why it's doing that.

Do you happen to have any idea why it's taking so long to reach the set temperature? I don't want to have it replaced until it stops working altogether. On 2018-06-06 by Jill

Reply by (mod) -

I would start at LOST COOLING CAPACITY

https://inspectapedia.com/aircond/Air_Conditioner_Diagnosis.php

for help in diagnosing and repairing the trouble ypu describe

Check air flow and temperaturee drop across the cooling coil.

Followup by Jill

And I just used the word "compressor" as being the problem when it could be the motor or something else (I read several things about it, but since I can't get on the roof, I can't check those things).

At this point, I just basically would like an opinion on whether or not I should continue to run it on auto until I have to have it replaced or would just letting it run continuously extend its life any? Thanks.

Thanks for the suggestion, but I don't know how to check things myself and part of it is on the roof, so if I decide to use the AC until it breaks down completely and I have to get a new one, am I better off leaving it on auto or just let it run all the time as far as if the compressor happens to be failing goes?

I say that because now it seems to be having more trouble starting up after it has been off between cycles.

Reply by (mod) -

Right - not even the service techs use consistent language. And yes, stay off the roof.

Check for reduced air flow at the supply registers

Check then for a dirty air filter


Check then for blocked, disconnected air ducts

 

Thank you to our readers for their generous comments

Trung Tâm Kỹ Thuật Điện Lạnh Sudiho said:

Thank you very much for your post, this is very useful for me! We are providing the air conditioner repair service in Hanoi-Vietnam \

Thanks to your blog that I was able to understand more about the air conditioner heat pump inspect and repair.

Thank you very much! Looking forward to such blog posts! On 2018-09-12

Jack said:

Thank you for a very useful article. I'm afraid to repair the air conditioner myself, so it's better to ask for help from specialists

I had a bad experience trying to repair AC myself. I repaired it, but after a while it broke down anew, and it was not possible to repair it and it was necessary to change it completely.

If you are not sure what you can fix, better find a contractor.

Well, now they can be ordered anywhere, even on the Internet you can choose by the price and reviews. - On 2018-04-12

Jack said:

Reply by (mod) -

Jack

A homeowner can sometimes find and fix certain problems with air conditioners and heat pumps such as a blocked or dirty air filter or can diagnose others such as leaky, damaged ductwork.

But work that involves more complex diagnosis of a compressor motor, refrigerant metering devices, finding refrigerant leaks, or charging a system require special training and equipment.

That's also the case for installing new air conditioning equipment excepting portable systems such as a window A/C that is simply brought home, installed in a window with proper support, and plugged-in.

 

What if my indoor unit has a higher BTU rating than my compressor?

What if my indoor unit has higher BTU than my compressor? i suspect the installer has fixed the wrong unit - 011-08-06 by Alan

Reply by (mod) - check with the manufacturer after getting the actual BTUh numbers

Alan, if the numbers are close the system may be adequately balanced;

I'd write down the data tag information from both the compressor/condenser unit and the air handler unit, then give the manufacturer's customer support line a call to ask their opinion.

Let us know the specifics of what you read on the data tags and what the manufacturer says.


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