Undersized A/C unit?

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1

Originally Posted By: bduckworth
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Does anyone report on undersized A/C Units for the square footage of conditioned space? For example, a 2 ton unit for 8000 sf of conditioned space. Just curious on what others are reporting. Thanks for your time,


Ben Duckworth

2

Originally Posted By: psmothers
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I do not. In the HVAC section of my report use the following sentence.


“The scope of this inspection does not include the effectiveness or adequacy of the system.” I am curious what everyone else here does.

–
Foxe Smothers


"Its not a matter of will we rebuilt it is matter of how soon..."

"A hero is no braver than an ordinary man, but he is brave five minutes longer."
- Ralph Waldo Emerson

3

Originally Posted By: dandersen
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Quote:
Does anyone report on undersized A/C Units for the square footage of conditioned space?


Yes I do.

Can you post how you are making the determination that it is/is not the correct size?
4

Originally Posted By: Steven Brewster
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Absolutely I inform them!! but I make darn sure that I am correct about the size of the unit and the area served. icon_wink.gif

5

Originally Posted By: jsmith10
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It depends on if the A/C is for the entire house or are they only cooling a certain area.


As a Home inspector do you feel confident in doing an energy assessment on the house to advise them on the proper size of A/C they require?


Is the house well insulated? how much window coverage on the south and west side of the house. What type of window’s do they have? Are the walls insulated? and there is much more.


I am a licensed HVAC journeyman and in so I feel confident that I can but I am experienced and that go's with my licence.

As a home inspector do you feel your qualified to give that info?

Most power companies will provide a FREE energy assessment of a home/business for proper sizing of mechanical equipment and insulation requirements.

For a home inspector I would recommend that possibly a comment to say would be something to the effect of:

A/C, furnace, or heater appears to be undersized for this home. Recommend further evaluation by a qualified HVAC craftsman or contacting your local power company as many provide this service at no charge.

You might look for the utility companies web site or contact info for this service and provide that for your clients.

Just a suggestion as there are a lot of variables that are involved as what one person needs is not necessarily what another needs.

I hope this helps.

If anybody has any questions concerning HVAC please feel free to contact me via email as I'd be more than happy to help.

Very good question though as many are undersized as builders are always's cutting corners and the HVAC is one of the biggest they use here in Idaho anyway.

--
Joe,
Vice-President, Idaho Chapter,
www.NachiIdaho.org

Inspected as though my family are to live or work there.

http://www.Treasurevalleyinspections.com

6

Originally Posted By: dandersen
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How do you make these determinations?

7

Originally Posted By: rcooke
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No how can I be expected to know if it is the correct size too big or too small.


I am a Home Inspector a generalist not a professional AC Person.


How can you be sure a unit is the correct size when so many variables can effect it .


Area of the country ,insulation in walls ,insulation in attic, air intrusion , shade trees ,


is it on a windy hill or a sheltered valley, does this area get little sun or is it a sunny area .


Is it near a lake that effects the temperature of the surrounding area .


Plain and simple it is not me job PERIOD.

NACHI Where We all Learn

--
Roy Cooke Sr.

http://Royshomeinspection.com

8

Originally Posted By: dandersen
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You guys are getting closer! icon_biggrin.gif


hint: Q = U A delta T

9

Originally Posted By: lkage
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I don’t specifically report on the size of the AC unit regarding square footage served but I do take the temperature differential (usually at the return and supply ducts) and report that.


If it is too far off from 20 degrees, I recommend further evaluation by a qualified HVAC technician and he may determine that it is undersized.

--
"I have never met a man so ignorant that I couldn't learn something from him."
Galileo Galilei

10

Originally Posted By: rcooke
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lkage wrote:
I don't specifically report on the size of the AC unit regarding square footage served but I do take the temperature differential (usually at the return and supply ducts) and report that.

If it is too far off from 20 degrees, I recommend further evaluation by a qualified HVAC technician and he may determine that it is undersized.

Correct me if I am wrong but I thought 14 to 22 was in the proper range.

NACHI Where We all Learn

--
Roy Cooke Sr.

http://Royshomeinspection.com
11

Originally Posted By: jsmith10
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With winter coming, I hope to get some time to develop a training aid for inspectors as to what I feel they should report on and how too.


This seems to be a vague area for a lot of inspectors and I believe it would be helpful to some.

--
Joe,
Vice-President, Idaho Chapter,
www.NachiIdaho.org

Inspected as though my family are to live or work there.

http://www.Treasurevalleyinspections.com

12

Originally Posted By: lkage
This post was automatically imported from our archived forum.


rcooke wrote:
lkage wrote:
I don't specifically report on the size of the AC unit regarding square footage served but I do take the temperature differential (usually at the return and supply ducts) and report that.

If it is too far off from 20 degrees, I recommend further evaluation by a qualified HVAC technician and he may determine that it is undersized.

Correct me if I am wrong but I thought 14 to 22 was in the proper range.

NACHI Where We all Learn



A 14 to 22 degree differential sounds about right, Roy, I was thinking of the 6-10 degree struggle after 20 minutes of running.

--
"I have never met a man so ignorant that I couldn't learn something from him."
Galileo Galilei
13

Originally Posted By: rcooke
This post was automatically imported from our archived forum.


lkage wrote:
rcooke wrote:
lkage wrote:
I don't specifically report on the size of the AC unit regarding square footage served but I do take the temperature differential (usually at the return and supply ducts) and report that.

If it is too far off from 20 degrees, I recommend further evaluation by a qualified HVAC technician and he may determine that it is undersized.

Correct me if I am wrong but I thought 14 to 22 was in the proper range.

NACHI Where We all Learn



A 14 to 22 degree differential sounds about right, Roy, I was thinking of the 6-10 degree struggle after 20 minutes of running.

Look for dirty filter or dirty Plenum coil .
Did one last week 6 years old same filter .
Felt sorry for the poor furnace.

--
Roy Cooke Sr.

http://Royshomeinspection.com
14

Originally Posted By: lkage
This post was automatically imported from our archived forum.


rcooke wrote:
lkage wrote:
rcooke wrote:
lkage wrote:
I don't specifically report on the size of the AC unit regarding square footage served but I do take the temperature differential (usually at the return and supply ducts) and report that.

If it is too far off from 20 degrees, I recommend further evaluation by a qualified HVAC technician and he may determine that it is undersized.

Correct me if I am wrong but I thought 14 to 22 was in the proper range.

NACHI Where We all Learn



A 14 to 22 degree differential sounds about right, Roy, I was thinking of the 6-10 degree struggle after 20 minutes of running.

Look for dirty filter or dirty Plenum coil .
Did one last week 6 years old same filter .
Felt sorry for the poor furnace.


I believe dirty filters are one of the top reasons for cracked heat exchangers, too.

No air to keep the exchanger cooled to the design temperature for proper operation...overheats and cracks.

--
"I have never met a man so ignorant that I couldn't learn something from him."
Galileo Galilei
15

Originally Posted By: dandersen
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If you determine the size of the HVAC by the SF of the house you may or may not be close.


If you determine A/C performance by dry bulb temp Supply/Return you may or may not be close.

Flipping a coin, may or may not be close too. ![icon_eek.gif](upload://yuxgmvDDEGIQPAyP9sRnK0D0CCY.gif)

I highly recommend that you do not use these methods to determine HVAC performance and size alone.

I recommend that unless you spend a great deal of time studying thermodynamics and become EPA certified to take the required measurements, that you simply run the equipment, take temperature measurements, write them in your report and give your "opinion" that it "feels" like the unit is working "at the time of and weather conditions present at the time of inspection". In accordance with federal law you can not and are therefore not required to do HVAC system evaluations.

The experts in the field can hardly agree at times (most of the time). "Comfort levels" can hardly be identified by the heating and cooling engineers of the world. It is my recommendation that you remain as vague as possible when it comes to HVAC performance.

There are things you can measure, compare with nameplate information and report on. You can open panels and observe conditions. You can comment on overall maintenance. You can feel if there is or is not air coming from all registers. You can look at the electrical and plumbing installations. You can detect air leaks, water leaks and even refrigerant leaks without any special equipment. It is not recommend that you get into system performance evaluation.

I say this because the issue becomes nothing but a big argument between the mechanical contractor and the home inspector. Then the RE Agent, Builder and even the client get frustrated with your inspection work. You'll start getting less referrals because if it.

16

Originally Posted By: bkelly2
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I would never size an AC unit. I observe the uint/s and commnnt. I take temp splits and comment (AZ 18 degrees to 22 degrees F). I have a 3000 sq/ft home with 7.5 tons.


Now if I see an 8000 sq/ft home with a 2 ton unit I would be curious. Is that the only heating and cooling? Are there registars in each room?

--
"I used to be disgusted, Now I try to Be amused"-Elvis Costello

17

Originally Posted By: jmertins
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Guys,



HI's should know general "rule of thumb" in determining tonage per SQ. foot. If you did not bring this possible problem to your buyers attention you better start in the future. At the very least reccommend a HVAC tech evaluate to ensure system is acceptable for sq. footage of the house/unit.


Not saying anything is far worse than throwing a red flag and being wrong.

--
John Mertins

Baxter Home Inspections, Inc.

"Greatness courts failure"

Roy "Tin Cup" McAvoy

18

Originally Posted By: bkelly2
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Sorry to disagree but I do not do “rules of thumb”. I believe if you go down that road you had better apply your “rules” to the entire system. Sizing a HVAC system is Engineering, of which I am not a practitioner.


OMHO


BK

--
"I used to be disgusted, Now I try to Be amused"-Elvis Costello

19

Originally Posted By: bsmith
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Quote:
No how can I be expected to know if it is the correct size too big or too small.
I am a Home Inspector a generalist not a professional AC Person.


Excellent point. "Sufficient cooling" can be very subjective. What I find adequate makes my wife shiver. What she finds comfortable is like a sauna to me. I report on whether the unit is functioning satisfactorily or not.

--
Bill Smith
www.SmithHomeInspection.com
"The difference between stupidity and genius is that genius has its limits." A. Einstien
20

Originally Posted By: lkage
This post was automatically imported from our archived forum.


bsmith wrote:
I report on whether the unit is functioning satisfactorily or not.


Basic, clear information on what we really do. ![icon_wink.gif](upload://ssT9V5t45yjlgXqiFRXL04eXtqw.gif)
Thanks, Bill.

--
"I have never met a man so ignorant that I couldn't learn something from him."
Galileo Galilei