"ComboverFish" wrote in message
om...
Hello, experienced masses....
I am selling my home and have fixed everything that has been asked by
the prospective buyer and the city so far but am having difficulty
with the buyer's inspector in regard to his A/C performance spec.
The inspector told buyer that the temp drop from return vent to
evaporator test point was 10 degrees. The buyer was told that my A/C
system isn't performing as it should. I verified his finding of 10
degree drop after they left with MY thermometer. I'm not arguing his
number or his method. Please read on to see what I AM arguing about
(to myself).
The temperature outside at that time was only 75 F. and relative
humidity was 70%. This is a pretty cool day for St. Louis in July.
It was also overcast with virtually no sun. It was only 10 Oclock am
and with no sun load, the house was quite cool. My probe-style
thermometer read 68 degrees on my kitchen counter and in the return
air duct. I think its accurate within 1-2 degrees. I believe it to
be relatively accurate in terms of temperature differential, atleast.
So as stated previously, I put the thermometer in the same test point
as the inspector did with the system running and got 58 degrees. The
magic delta figure to fail a system and scare a buyer seems to be
below 15 - 17 degrees from what I've gathered in talking to realestate
agents and dealing with several home inspections. But don't you have
to take into consideration the temp and humidity and solar load to
some extent before interpreting delta temp?
I just happened to have an A/C company out two weeks ago to give my
system a performance test so I would be armed with a professional
opinion on paper before negotiations started. This is because the
previous owner had several big dogs, and apparently their big bladders
found the warm condenser fins a common target. (I was told that dogs'
urine is a common cause of condenser fin errosion). The missing fins
in one lower corner area coupled with some rust on the thin cage that
protects the condenser make the outside unit appear old and worn to be
sure. It isn't a great selling point visually. But this house isn't
the fricken' Taj Mahal either. I don't feel that someone can use the
APPEARANCE of my A/C unit to demand $2000+ for a new one IF IT WORKS!
The A/C guy I hired wrote that the temp change was 18 degrees,
pressures were normal and that 'system was operating normally at this
time'. It was about 85 degrees out and sunny that day and he did the
work around 2 pm. I tested the temp drop several days before he came
out and actually got 21 degrees but I can't remember the temperature
or sun condition then.
So how do you all feel about the accuracy of DELTA for the purposes of
condemning an A/C system? Do I really have a problem? Or may the
inspector have seen that the unit was around 15 - 20 years old with
fin damage and just found an easy way to condemn it that isn't
accurate? (much less than 5% fin damage)
I feel that for my 900 sq ft house with full basement (all cooled with
ductwork) and poor insulation my electric bills are reasonable. I
also feel that the A/C FEELS cold and the system has never been
charged in my 8 years here. I mean, 58 degree temp in the furnace
ductwork can't be that bad can it?
I thank you all for any responses yay or nay!!!
Tony
This is Turtle.
1) Checking the T.D. / Delta-T is not a very good test of the proformance of a
system for on high humitity day it will make the TD number look very poor and on
a dry day make the numbers look very good and it being the same system but at
different times. With the TD you can make a system look anyway you want it by
picking the time and days you want to check it. It sucks to check a system this
way.
2) Call all of them over to see the results of the TD but let the house get up
to about 95ºF or more in the house and then turn it on and you will have a 30ºF
to 35ºF [ TD ] . You can make the number what you want when choosing the time to
check it.
3) If you have a 58ºf discharge temperature and about 70ºf to 75ºf indoor
temperature. a TD of 10ºF or 15ºF can be just fine.
4) one for a thought. Take a brand new tune to perfection 14 seer hvac system
flower rater type and not expanion valve type evaperator coil and turn it on in
outdoor temperature of 50ºF and you will be luck as hell to get a 7 to 10ºF TD.
You need a low ambiant controller to get it to work in 50ºF or less outdoor
temperatures.
5) If your agent is going to use the TD to see if the system is working
properly you don't need a hvac professional at all and just get the yard boy to
check and turn up your system.
6) Using TD for a standard good test of a system is really just a joke talk
about.
TURTLE
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