We are finally replacing the HVAC in our house. The furnace is
original in 1971, 140,000 BTU. Central air is 3 1/2 ton Trane put in
1987. The new ones will be both Trane units. The new furnace will be
92.5% AFUE 112,000 BTU. AC is the same tonnage at 15 SEER. The house
is 2,100 sq ft in NJ.

The HVAC contractor suggested raising the duct returns on the second
floor from the existing near floor locations to a higher location near
the ceiling when I told him our second floor doesn't get cooled that
well. The plan is to raise it without additional ducting by using the
joist space. Does it make sense?

yaofeng wrote:
We are finally replacing the HVAC in our house. The furnace is
original in 1971, 140,000 BTU. Central air is 3 1/2 ton Trane put in
1987. The new ones will be both Trane units. The new furnace will be
92.5% AFUE 112,000 BTU. AC is the same tonnage at 15 SEER.

Did the contractor do a heat loss / heat gain calculation to come up
with those sizes?

No. This guys has his business in our town and has been in business
for 35 years. He takes out about 1,000 permits a year. He did most of
the houses in my neighborhood. Actually one of my neighbors gave me
his number. He probably did the existing AC before I moved in the
house in 1990. We have had a couple of estimates for replacing the
system since late spring but kept procrastinating. His number is the
lowest, although not by very much. What started it again was the AC
condenser went kaput a week ago. The compressor heater went. He sent
a gu to fixed it the same day coming to our house to give me the
estimate.

In addition to pricing, I am prejudiced because I like him. He
explains how things work to you.

yaofeng wrote:
We are finally replacing the HVAC in our house. The furnace is
original in 1971, 140,000 BTU. Central air is 3 1/2 ton Trane put in
1987. The new ones will be both Trane units. The new furnace will be
92.5% AFUE 112,000 BTU. AC is the same tonnage at 15 SEER. The house
is 2,100 sq ft in NJ.

The HVAC contractor suggested raising the duct returns on the second
floor from the existing near floor locations to a higher location near
the ceiling when I told him our second floor doesn't get cooled that
well. The plan is to raise it without additional ducting by using the
joist space. Does it make sense?


it does and its simple. What effect will it have in the winter?

--
Respectfully,


CL Gilbert

yaofeng wrote:
No. This guys has his business in our town and has been in business
for 35 years. He takes out about 1,000 permits a year. He did most
of the houses in my neighborhood. Actually one of my neighbors gave
me his number. He probably did the existing AC before I moved in the
house in 1990.

In addition to pricing, I am prejudiced because I like him. He
explains how things work to you.

Don't let size or emotion drive your decision.

http://www.proctoreng.com/articles/bigger.html

The same scientific process should be used to size heating equipment.
Ask your contractor if he'll do a "Manual J" load calculation prior to
sizing and installation of the furnace and A/C. Tell him it is for your
peace of mind if nothing else.

I presume the hot air will be recycled back to the furnace inlet, which
is not necassarily bad. The furnace just don't have to crank out as
much heat working on heated air.

Don't forget he is the low bid.

"yaofeng" wrote in message
oups.com...
Don't forget he is the low bid.


If the guy chooses the wrong size unit for your house, "low bid" won't mean
much to you a year or two from now. Travis is making a good suggestion.

What you will likely have is some pretty extreme stratification, where
the elevated returns are, besides reduced heating efficiency.

At least if he put the discharges near the ceiling with the returns
below, you'd have a manageable loop, just be overheating air at
ceiling.

What I've found to work very well, for heating and cooling is plastic
flow-diverters that magnetically attach to registers. E.g. instead of
cooled air flowing across floor to return, diverter makes it ascend for
a bit and mix with room air well above ankle-height. Much cheaper, and
more effective, IMHO than raising return.

OTHO, if return and discharge were reversible summer-to-winter, you'd
be in business.

HTH,
J

yaofeng wrote:
We are finally replacing the HVAC in our house. The furnace is
original in 1971, 140,000 BTU. Central air is 3 1/2 ton Trane put in
1987. The new ones will be both Trane units. The new furnace will be
92.5% AFUE 112,000 BTU. AC is the same tonnage at 15 SEER. The house
is 2,100 sq ft in NJ.

The HVAC contractor suggested raising the duct returns on the second
floor from the existing near floor locations to a higher location near
the ceiling when I told him our second floor doesn't get cooled that
well. The plan is to raise it without additional ducting by using the
joist space. Does it make sense?

The return changes should help. How much will be seen. The issue
Travis presented is valid. I would have the computations done.

--
Joseph Meehan

Dia duit

I am very biased in this matter as you will see if you haven't already.

This guy is an electrical engineer. I am also an engineer licensed to
practice in New Jersey. We talk the same language even though in
different disciplines. He has 35 years experience in this field. My
experience is not much different. If you ask me to provide
calculations for something I know the answer already I'll dismiss it as
a waste of time. But if I must do it, I will. There are no fewer than
four models similar to my house in the block. I trust his estimation.
Further more, is he providing far larger capacity heating and AC unit
than the previous rwo estimates? All three estimates were in the same
size range. One estimate was by PSEG. Another indication is the size
quoted in the estimates as compared to the current unit and is my
current unit adequate? Except for the less than satisfactory AC on the
second floor which he is providing a solution for we have no
complaints. This is engineering. Not science. Could all three have
made the same mistakes? I can not rule it out but it is not likely.

Call me pigheaded. One thing I am glad I am not in the medical
profession is the defensive medicine and measures they have to put up
in their daily work. Although they probably bring home much fatter
bacon than I. Does experience not count anymore that one has to
document and substantiate every thing he does? Does experience, trust,
relationship and credibility not count in your profession? I can not
say I will enjoy my work if I have to put up defensive medicine
(measures) on a daily basis. No matter the amount of bacon I earn.

yaofeng wrote:
Call me pigheaded.

Why an engineer wouldn't want to get the facts of the matter and make a
decision based thereupon is beyond me.

yaofeng wrote:

No. This guys has his business in our town and has been in business
for 35 years. He takes out about 1,000 permits a year. He did most of
the houses in my neighborhood. Actually one of my neighbors gave me
his number. He probably did the existing AC before I moved in the
house in 1990. We have had a couple of estimates for replacing the
system since late spring but kept procrastinating. His number is the
lowest, although not by very much.


What started it again was the AC
condenser went kaput a week ago. "The compressor heater went." (?) He sent
a guy to fixed it the same day coming to our house to give me the
estimate.

In addition to pricing, I am prejudiced because I like him. He
explains how things work to you.


If he puts that many A/C systems in two story homes the design should
have had them cooling both stories equitably!

I can explain to you how airconditioning systems work until hell freezes
over, and it means nothing if I don't design the systems I install in
two story homes to work properly for the occupants. I knew guys that
had been in the HVAC business for many decades and didn't do much right;
some keep doing it the way they had always done it and never learn to do
it right!

Running the returns up the walls should help some; have top and bottom
registers so you can close one off according to the season. (Use bottom
return for heating.)

Every home should have a manual J heatgain done by someone that will do
it right. You might be able to make some changes that would allow you to
drop down a half or full ton in unit sizing. A lot of 3.5ton systems are
only putting out 2 to 2.5-ton of cooling to the conditioned space.

For example I replied to this Tech: 35 ton 10 SEER system.

I'm at a loss for the 8 degree DT. HO has never said house doesn't cool
well just runs quite a bit when above 88 deg. Coils, ductwork, blower,
etc. checks OK. If I plug these numbers in my psychometric calculator
(which by the way works very well) I get these numbers

Here are my readings.

Ambient Temp= 78

Suction PSI= 70

Suction Temp= 61

Head PSI= 225

Liq. Line temp= 104

Entering DB= 74

Entering WB= 64.5

Leaving DB= 66

Leaving WB= 61

3.5-Ton equipment yielding:

17203 "total Btu/hr" Not even a 1.5-ton

13306 Btu/hr Sensible.

3717 Btu/hr Latent
What is up?
-----------------
The above tonnage loss is not as unusual as you would think; it is
rather common but not quite to that extent!
http://www.udarrell.com/ac-trouble-s...ubcooling.html
There is also probably a lot more wrong than just the charge and
airflow. - udarrell - Darrell
--

Factors in the Correct Sizing of Residential Air Conditioning Systems -
Recommended Procedures for Proper Duct Sizing of Residential Air Conditioning Systems
http://www.udarrell.com/proper_cfm_b...syste ms.html

Wait a minute.

You like him, you are prejudiced toward using him, your are both EE's.

But you come to a usenet forum asking people you don't know and never
will know, if he knows what he is talking about?

You aren't pigheaded, you are two faced.

wrote in message
ups.com...
What you will likely have is some pretty extreme stratification, where
the elevated returns are, besides reduced heating efficiency.

At least if he put the discharges near the ceiling with the returns
below, you'd have a manageable loop, just be overheating air at
ceiling.

What I've found to work very well, for heating and cooling is plastic
flow-diverters that magnetically attach to registers.

If the duct is extended, you have two outlets. Open one, close the other,
depending on season. I've seen that done with good success.

"yaofeng" wrote in message
oups.com...
No. This guys has his business in our town and has been in business
for 35 years. He takes out about 1,000 permits a year. He did most of
the houses in my neighborhood. Actually one of my neighbors gave me
his number. He probably did the existing AC before I moved in the
house in 1990.

In addition to pricing, I am prejudiced because I like him. He
explains how things work to you.

I'm going to buck the experts here. Forget the Manual J.

In a new house, new design, I'd agree 100% that the Manual J calculations
should be done. If, however, you'll lived in the house for 15 years, it has
been very comfortable with a given sized unit, it is the same as 10,000
other similar homes in the region that have the same sized units and are
comfortable, I'd trust the guy with 35 years experience to say, "yep, this
size is OK".

I don't care how well the calculations are done, the situation will change
anyway. You have three more kids that add body heat and more laundry and
the associated heat load. Cooking heat load. A big tree gets cut down. A
small tree grows up. The four teenagers you have now move out of the house
and it is just the two of you. You add a better storm door. You leave the
garage door open. All these things affect how well the AC works in YOUR
situation.

I told the story before. I used to quote tooling for our company. I'd do
the estimate in less than five minutes. The engineer in the machine shop
would do the calculations over a period of three days and a few hours of
actual calculating and getting quotes from suppliers. We'd be within $100
or less on a $10,000 tool, every time. He felt the need to do the math each
and every time. I started out looking at what he quoted for a similar item
and use his numbers over and over again.

If you feel comfortable with the guy, he is probably the best for you in
your situation.
--
Ed
http://pages.cthome.net/edhome/

I want to give you an opportunity to substantiate your accusation that
I am two faced. Please tell me how and why I am two faced.

I obtained three bids. He not only came in the lowest, he has
references from at least three of my neighbors. He is using similar
size units as my existing ones which work and those he installed in the
neighbohood which has houses built in the same era of similar living
space. He has been in business in this town for 35 years. He
explained to me how he intend to do it and as much as I could
understand how things work. We talked in my kitchen. We found we both
have engineering degrees and share comon intersts in cars and other
hobbies. His kids grew up in the same school system as mine.

So how does that make me two faced if I use his service?

I am not an electrical engineer for your information.

And finally is that how you treat people in your daily encounter by
calling them names?

Edwin Pawlowski wrote:
"yaofeng" wrote in message
oups.com...
No. This guys has his business in our town and has been in business
for 35 years. He takes out about 1,000 permits a year. He did most of
the houses in my neighborhood. Actually one of my neighbors gave me
his number. He probably did the existing AC before I moved in the
house in 1990.

In addition to pricing, I am prejudiced because I like him. He
explains how things work to you.

I'm going to buck the experts here. Forget the Manual J.

In a new house, new design, I'd agree 100% that the Manual J calculations
should be done. If, however, you'll lived in the house for 15 years, it has
been very comfortable with a given sized unit, it is the same as 10,000
other similar homes in the region that have the same sized units and are
comfortable, I'd trust the guy with 35 years experience to say, "yep, this
size is OK".

I don't care how well the calculations are done, the situation will change
anyway. You have three more kids that add body heat and more laundry and
the associated heat load. Cooking heat load. A big tree gets cut down. A
small tree grows up. The four teenagers you have now move out of the house
and it is just the two of you. You add a better storm door. You leave the
garage door open. All these things affect how well the AC works in YOUR
situation.

I told the story before. I used to quote tooling for our company. I'd do
the estimate in less than five minutes. The engineer in the machine shop
would do the calculations over a period of three days and a few hours of
actual calculating and getting quotes from suppliers. We'd be within $100
or less on a $10,000 tool, every time. He felt the need to do the math each
and every time. I started out looking at what he quoted for a similar item
and use his numbers over and over again.

If you feel comfortable with the guy, he is probably the best for you in
your situation.
--
Ed

Thanks. This is exactly what I was referring to. Experience counts.

If you are so trusting on his advice for the size of the unit, why are you
asking the group for advice on his suggestion to raise the return air to the
ceiling on the second floor????

Regardless, to answer your question, this is a fairly common practice,
particularly in retro-fitting into an older home. That is as long as it
meets the local code, and it is on an interior wall.


"yaofeng" wrote in message
oups.com...
I am very biased in this matter as you will see if you haven't already.

This guy is an electrical engineer. I am also an engineer licensed to
practice in New Jersey. We talk the same language even though in
different disciplines. He has 35 years experience in this field. My
experience is not much different. If you ask me to provide
calculations for something I know the answer already I'll dismiss it as
a waste of time. But if I must do it, I will. There are no fewer than
four models similar to my house in the block. I trust his estimation.
Further more, is he providing far larger capacity heating and AC unit
than the previous rwo estimates? All three estimates were in the same
size range. One estimate was by PSEG. Another indication is the size
quoted in the estimates as compared to the current unit and is my
current unit adequate? Except for the less than satisfactory AC on the
second floor which he is providing a solution for we have no
complaints. This is engineering. Not science. Could all three have
made the same mistakes? I can not rule it out but it is not likely.

Call me pigheaded. One thing I am glad I am not in the medical
profession is the defensive medicine and measures they have to put up
in their daily work. Although they probably bring home much fatter
bacon than I. Does experience not count anymore that one has to
document and substantiate every thing he does? Does experience, trust,
relationship and credibility not count in your profession? I can not
say I will enjoy my work if I have to put up defensive medicine
(measures) on a daily basis. No matter the amount of bacon I earn.

Panning joists violates the codes in most areas. Not doing a load
calculation also violates the codes. What other code mis he going to
violate. He may explain things, but he must be explaining things wrong
if violating codes is ok with him. Check the International Mechanical
Code and International Residential Building Code, now used all over the
USA, except in the few places where there are no codes.

Stretch

"yaofeng" wrote in message
oups.com...
I am very biased in this matter as you will see if you haven't already.

This guy is an electrical engineer. I am also an engineer licensed to
practice in New Jersey. We talk the same language even though in
different disciplines. He has 35 years experience in this field. My
experience is not much different. If you ask me to provide
calculations for something I know the answer already I'll dismiss it as
a waste of time. But if I must do it, I will. There are no fewer than
four models similar to my house in the block. I trust his estimation.
Further more, is he providing far larger capacity heating and AC unit
than the previous rwo estimates? All three estimates were in the same
size range. One estimate was by PSEG. Another indication is the size
quoted in the estimates as compared to the current unit and is my
current unit adequate? Except for the less than satisfactory AC on the
second floor which he is providing a solution for we have no
complaints. This is engineering. Not science. Could all three have
made the same mistakes? I can not rule it out but it is not likely.

Call me pigheaded. One thing I am glad I am not in the medical
profession is the defensive medicine and measures they have to put up
in their daily work. Although they probably bring home much fatter
bacon than I. Does experience not count anymore that one has to
document and substantiate every thing he does? Does experience, trust,
relationship and credibility not count in your profession? I can not
say I will enjoy my work if I have to put up defensive medicine
(measures) on a daily basis. No matter the amount of bacon I earn.


Engineering isn't science? I'm never driving over a bridge again! And by the
way - it's possible to install an AC unit that's too large for your house.
It'll cool the air down quickly, but not run long enough to remove humidity.
Bummer. Makes for a clammy feeling house.

What he's saying is that if you trust the guy so much that you're willing to
do all this typing, then why did you come here looking for other opinions,
most of which you're arguing with?

"yaofeng" wrote in message
ups.com...
I want to give you an opportunity to substantiate your accusation that
I am two faced. Please tell me how and why I am two faced.

I obtained three bids. He not only came in the lowest, he has
references from at least three of my neighbors. He is using similar
size units as my existing ones which work and those he installed in the
neighbohood which has houses built in the same era of similar living
space. He has been in business in this town for 35 years. He
explained to me how he intend to do it and as much as I could
understand how things work. We talked in my kitchen. We found we both
have engineering degrees and share comon intersts in cars and other
hobbies. His kids grew up in the same school system as mine.

So how does that make me two faced if I use his service?

I am not an electrical engineer for your information.

And finally is that how you treat people in your daily encounter by
calling them names?

mwlogs wrote:
If you are so trusting on his advice for the size of the unit, why are you
asking the group for advice on his suggestion to raise the return air to the
ceiling on the second floor????

Maybe I am bored?

I have no problems regarding his selection of either the furnace or AC.
Two other prior estimate made the same selection. My neighbors all
have similar size unit. Raising the return is something new to me,
however. I still trust him. Does that mean I am not supposed to
verify?

No engineering isn't science.

yaofeng wrote:
I still trust him. Does that mean I am not supposed to
verify?

Why bother? You're not verifying his sizing of the equipment.

yaofeng wrote:
No engineering isn't science.

Right...that's why an engineering degree is a Bachelor of What degree?

Why should I? Am I preparing for a litigation down the rood if the
house is not heating or cooling to MY satisfaction?

"Travis Jordan" wrote in message
m...
yaofeng wrote:
No engineering isn't science.

Right...that's why an engineering degree is a Bachelor of What degree?



Cooking?

yaofeng wrote:
Why should I?

Because you'd want to be sure that the system was sized correctly.
Maybe your neighbors with identical homes are all oversized, too. That
would be quite common. The ONLY way to know is to do a heat gain
calculation.

Or live with the question. Your choice.

"Travis Jordan" wrote in message
.. .
yaofeng wrote:
Why should I?

Because you'd want to be sure that the system was sized correctly.
Maybe your neighbors with identical homes are all oversized, too. That
would be quite common. The ONLY way to know is to do a heat gain
calculation.

Or live with the question. Your choice.

He has been living with the same sized unit for years now. So have he
neighbors. What is a calculation tell him that experience is not?

Edwin Pawlowski wrote:
"Travis Jordan" wrote in message
.. .
yaofeng wrote:
Why should I?

Because you'd want to be sure that the system was sized correctly.
Maybe your neighbors with identical homes are all oversized, too.
That would be quite common. The ONLY way to know is to do a heat
gain calculation.

Or live with the question. Your choice.

He has been living with the same sized unit for years now. So have he
neighbors. What is a calculation tell him that experience is not?

http://hem.dis.anl.gov/eehem/95/950509.html

"Edwin Pawlowski" wrote in message
news:qs0Me.4874$Xw5.869@trnddc02...

"Travis Jordan" wrote in message
.. .
yaofeng wrote:
Why should I?

Because you'd want to be sure that the system was sized correctly.
Maybe your neighbors with identical homes are all oversized, too. That
would be quite common. The ONLY way to know is to do a heat gain
calculation.

Or live with the question. Your choice.

He has been living with the same sized unit for years now. So have he
neighbors. What is a calculation tell him that experience is not?


Hmm. Young first time buyers may not know there's something better than what
they already have. That happens with many details of home ownership, as well
as car maintenance, boat maintenance, garden maintenance.

"yaofeng" wrote in message
oups.com...
I am very biased in this matter as you will see if you haven't already.

This guy is an electrical engineer.

Hes not a mechanical engineer?
So, basically, you are having an electrician, do your mechanical
work....thats like hiring a plumber to do sheetrock.

I am also an engineer licensed to
practice in New Jersey. We talk the same language even though in
different disciplines. He has 35 years experience in this field. My
experience is not much different. If you ask me to provide
calculations for something I know the answer already I'll dismiss it as
a waste of time. But if I must do it, I will. There are no fewer than
four models similar to my house in the block. I trust his estimation.
Further more, is he providing far larger capacity heating and AC unit
than the previous rwo estimates? All three estimates were in the same
size range. One estimate was by PSEG. Another indication is the size
quoted in the estimates as compared to the current unit and is my
current unit adequate? Except for the less than satisfactory AC on the
second floor which he is providing a solution for we have no
complaints. This is engineering. Not science. Could all three have
made the same mistakes? I can not rule it out but it is not likely.

As someone that IS in the field of mechanical work, yes, all three can make
the same mistake, and all three can talk to you like you want to be talked
to.
If no one did a proper manual J, or T, or D, then all 3 are screwing you.
You want professional work you should expect professional work.
If no ones done their work, then its all guesstimates.


Call me pigheaded. One thing I am glad I am not in the medical
profession is the defensive medicine and measures they have to put up
in their daily work. Although they probably bring home much fatter
bacon than I. Does experience not count anymore that one has to
document and substantiate every thing he does? Does experience, trust,
relationship and credibility not count in your profession? I can not
say I will enjoy my work if I have to put up defensive medicine
(measures) on a daily basis. No matter the amount of bacon I earn.

Any legitimate contractor, will: Document every move on a job. Document
every sizing calculation to defend his position, and in most areas now, any
AC permit must have a load calculation with it, so that in the event there
is a mold claim at a later date, the contractor can show where he sized the
unit properly, and installed it correctly to code.
He will also document any changes to the original agreement with a change
order, signed by himself, the homeowner and any subs involved.
While respect, reputation and trust all factor in, you dont get that way by
not doing your job properly.
I can also tell you that depending on your region, a 15SEER unit wont be the
same size as a 10SEER on the same home.
You also can NOT use the same duct that a unit installed in 1971 used on a
new 12SEER unit, much less a 15SEER.
If you are truly an engineer, you understand why proper calculations are
important for you to have the correct information on paper when all is said
and done....therefore, going on a mans word, isnt the way you want it done.
Also, have you asked your friend how many calculations he will do AFTER the
unit is installed to insure you have the SEER you paid for? You should get a
sheet with over 100 calculations done, AFTER the unit is installed, showing
that you have the proper SEER. Meaning, in plain English, you paid for a
15SEER unit, are you really getting 15SEER, or only 10?

As a homeowner, anyone I hire to work on my home better back up their talk
with some facts. Being in a building trade, as a company owner, we get to
see alot more than the average man, in regards to home repair, and
contruction. We see some real crappy work, and we see some real nice stuff
that would be called overkill by some. One thing we have learned is that the
low bid is not always the wrong bid, nor is the high or middle bid always
the best....however, we have been, and continue to be staunch in our
position that most HVAC contractors are rapists, not all, but most, and
since the average man knows little to nothing about the trade, these guys go
out, and rip people off daily. They are not the ones you find posting in
self help groups, or in the alt.hvac group. They are the ones that charge
$300 to show up on a Sat afternoon, and do nothing. They are the ones that
charge $35 a pound for refrigerant and never use a scale....they are the
ones that think that charging a system only requires the use of a jug of R22
and a set of guages...nevermind the other 5 to 10 tools that are required to
do it right.

If you are NOT getting documentation to the size of the unit, HOW that size
was come to, the duct layout, WHY that duct layout was needed, and
documentation about the final testing, you are getting screwed. Period. You
can be happy with the price you paid, you can be happy with the
installation, you can be happy with it all without it, but bottom line,
without it, you have a POS installation, since all the legwork was not done
properly.

Were you part of the team at NASA for the Columbia mission?

"yaofeng" wrote in message
oups.com...
I am very biased in this matter as you will see if you haven't already.

This guy is an electrical engineer. I am also an engineer licensed to
practice in New Jersey. We talk the same language even though in
different disciplines. He has 35 years experience in this field. My
experience is not much different. If you ask me to provide
calculations for something I know the answer already I'll dismiss it as
a waste of time. But if I must do it, I will. There are no fewer than
four models similar to my house in the block. I trust his estimation.
Further more, is he providing far larger capacity heating and AC unit
than the previous rwo estimates? All three estimates were in the same
size range. One estimate was by PSEG. Another indication is the size
quoted in the estimates as compared to the current unit and is my
current unit adequate? Except for the less than satisfactory AC on the
second floor which he is providing a solution for we have no
complaints. This is engineering. Not science. Could all three have
made the same mistakes? I can not rule it out but it is not likely.

Call me pigheaded. One thing I am glad I am not in the medical
profession is the defensive medicine and measures they have to put up
in their daily work. Although they probably bring home much fatter
bacon than I. Does experience not count anymore that one has to
document and substantiate every thing he does? Does experience, trust,
relationship and credibility not count in your profession? I can not
say I will enjoy my work if I have to put up defensive medicine
(measures) on a daily basis. No matter the amount of bacon I earn.