System Design Help - Buyer's Remorse

[ciltep]

Would appreciate some help and advice. I live in Iowa (cold winters, hot humid summers and everything in between) and just bought a new house. It’s a ranch with a walkout basement. There are 1980 sq. ft. on the main level and the same below. Nothing is finished yet in the basement. House itself is built well—good insulation and though I think the windows are not real great, a blower door test indicated .12 air infiltration. I guess that means their ok? Back on point.

I’m not real happy with the heating system. I’ve got a single-stage WeatherKing 92 AFUE 105k output Btuh model 90RJ10EGS01. I’ve got a WeatherKing 12 Seer AC with an Aspen coil. It’s a 4 ton and the model is 12AJA4801. The builder went with a 4 ton because he said that will be necessary if the basement is finished off someday.

The problems that I currently have are noise and the house feels cool at times. I’ve called a couple of places to get some advice and opinions, but none of them seem to have the knowledge that some of you folks have.

The general consensus is that my noise problem is ducting. I thought it was the unit itself and still think that might be part of the problem. The blower sounds loud when I compare it to my parent’s lennox which is also single-stage 100k output. I’ve been told my trunk ducts are two small. The furnace is centrally located in the basement and has two trunk supply ducts running in each direction. The one duct measures 8 x 14 and the other is 8 x16 for about 5 feet and then reduces down to 8 x 14 for the remaining run. The cold air return is all 8 x 14.

On another board, I was told the unit is oversized and that is part of the problem. I did a load calc using heatpro and it said I should be more in the 75k output range with a finished basement. The person who said it was oversized also said there’s no way my duct system will handle the 4 ton a/c. The heatpro calc suggested trunks sized 8 x 18. I should mention that all of my supply runs are the rigid 5” pipe.

The real issue is that I’m planning on finishing the basement soon. Unlike Jeff, however, I’m lucky in that it’s wide open and I can basically change anything I want. Of course it all costs, but I have access to everything. I want to balance comfort and noise and right now both seem a little out of whack. I’m planning on adding five more supply runs in the basement. The only part that seems ok are my cold air returns. There’s one in each bedroom near the ceiling, one in the living room near the ceiling, and a spot for one in the basement at ground level.

Will adding the five additional runs in the basement help or hurt my situation? Is my ducting really not going to be able to handle the 4 tons of cooling? Are my furnace and AC way oversized? How can I reduce the noise and increase comfort?

I realize this is a short novel, but I’m not touching anything in the basement until I get some good advice. I’m not that confident in the local contractors. I’m looking to you good folks for some advice. I appreciate any constructive feedback you give.

If anyone would like a photo of my layout, Posting your email address is against the Forum Rules (http://hvac-talk.com/vbb/showthread.php?threadid=1241) Sometimes a picture is worth a thousand words.

Thanks.

[Edited by Lusker on 02-03-2006 at 06:27 PM]

[tinknocker service tech]

14x8 return for a four ton unit is way to small
it is about 500cfms off the top of my head and you need 1600 min. your supply is small also and imo all the ducts need to be replace with the proper sized
have some do man-d to size the system ducts properly

[pstu]

The ACCA Manual D method is the most proper way I think, to size your duct system. A really good HVAC technician ought to be able to apply this (though by this definition such techs are hard to find where I live). This book states clearly that using hard pipe, you are best to limit airspeed to 700 feet/min for supply ducts and 600 feet/min for returns. It also states the maximum airspeed approved is 900 for supply and 700 for returns.

If this limit is exceeded, you can expect excessive duct noise. This is not merely academic, I can testify that my own supply ducts are very noisy when my air handler pushes 1400 cfm -- I estimate this makes for 860 feet/min in some of my ducts (flex, which has 600 recommended and 700 max). In my case choosing 1200 cfm gets down to about 750 feet/min, still exceeding the limit and slightly noisy.

As has been said before, your 4.0 ton AC air handler will need to supply about 1600 cfm. If you do some arithmetic you can easily calculate the airspeed necessary to push that 1600 cfm through your ducts. I think you will find some numbers which definitely exceed what Manual D approves.

This is only one part of Manual D, there are other parts which I have far from mastered. But I do believe there is nothing misleading in what I have stated. If any of our professionals care to point out any errors here, we all will benefit.

Best wishes -- Pstu

[ciltep]

Thanks for the responses thus far. However, I really am a novice. I really don't understand all the cfm talk. Are you saying I can adjust the air handler to lower the cfm? Is this advisable?

Also, just so I am clear (my terminology may not be correct), I have 5" snap together supply run pipes. My supply trunks that feed those pipes are roughly 8x14, but the plenum is much larger than that. The cold air return run is the same size 8x14. However, when it gets back to the furnace, before shooting downward, it widens out dramatically. The vertical part that then runs down almost to the floor and then over to the furnace is 10 x 25.5. That part is about 8 ft. tall and runs down then kind of elbows over and once it actually poors air into the furnace it's 16 x 25.5. That's roughly the size of my filter. I didn't want to paint a picture of the cold air return only being 8x14 when it feeds back into the side of the furnace. That isn't the case.

Does that make a difference with respect to some of the previous comments? Sorry to sound naive, but I am. Is the manual D something that a complete novice could attempt to get through?

[Advanced Response]

What has been stated is you need a HVAC Professional/Contractor!!

You need to have them do a detailed room by room load calculation(Manual J)...
You need to have them do a detailed duct layout based on manual D..
They can point you in the direction on if anything you currently have can be salvaged or if all is mis-sized..

PSTU is great guy but not your average homeowner..

Good luck
J

I vote that PSTU become a homeowner Pro!! He is more knowledgeable than some techs that have been in the field many yrs.. Great posts Student..

[ciltep]

I would love to hire a professional HVAC Contractor. Unfortunately, around here there are a ton of contractors but none that I would call professional based on your standards. The places that I have called (three in total) all just spout off old rules of thumb and I'm talking about Lennox, Trane, and Carrier dealers/techs. Now, I'm not saying they don't know their stuff, but none seem interested in doing a load calc for each room and a duct design based on Manual J and Manual D, so maybe they are just lazy.

I think I'll probably just read what I can in these forums and take a crack at it myself. I can't do any worse than the random rules of thumb that I'm being quoted and it'll probably be a step up from every other new const. home around here who uses these guys. At least the HeatPro calc gives me a rough estimate of output I need.

I'd hire a good one if I could find one. There aren't any ACCA contractors within 50 miles of my zip.

I did mispeak earlier. My supply runs are 6" not 5".

[Advanced Response]

There might be a contractor on this site that is near you..
You might want to start a thread asking if any contrators from this site service your area....

Also check the NCI website and see if there are any trained pros from your area..

A proper ductsystem design is tough to do.. I made some major mistakes when I first started doing them and it took me a while before I found out some steps I was not doing correctly.. These mistakes were costly.. Also proper installation of ductwork is not an easy chore.. Metal is sharp and cuts deep.. I know first hand(lucky I still have both my hand left)..

I would not recommend trying to do your own design and install... Will not save you any money and will cost you many times over, untill it is totally done right..

Also, this site will not allow step by step directions over the internet and any that will may not give you the correct advice for your situation as they have not seen the job and may not know how to do it correctly but think they do..!!

Good luck
J

DIY in this project is a disaster waiting to happen.. I am sure there is atleast one true hvac contractor in your area,, probably more than one..

[beenthere]

Your duct work sounds like a beginners first atempt at design.
With out any trainning.

Tear out and start over.

Get out the phone book and start calling contractors, ask them if they use manual D, keep calling until you find one that does.

Yes, you can buy the books and study them, and might be able to do a better job then what you have now. But a quality contractor will check the sizing of both your furnace and A/C and be able to advise you if its worth while just redoing the duct work.

If your furnace is over sized that much, wonder how far off the A/C sizing is.

[ciltep]

That's what's funny about it. They weren't beginners. The company has been in business for over 35 years under the same family ownership.

I don't know much about HVAC, but I know a little more than the average homeowner. I think most folks out there don't know anything about it.

[ciltep]

No luck on the NCI website. Thanks for mentioning it though.

So with that said, are there any professionals out there who serve the Cedar Rapids, Iowa area?

Any by pro, I mean someone that will do a manual J and D.

Thanks.

[dash]

What's your zipcode and city/state?


you really need a Pro,to resolve the issues.

Ther is Profesional Design available on the web,might try to google it,not sure where but I've seen it.

[Steve Wiggins]

I think there is some confusion about who is considerd a "pro" and who is not.

HVAC installer - A green rookie that is just starting out and does hard hot work that old fat guys can't do anymore. Some are stuck in this position due to their criminal background and/or drug & alcohol addictions.

HVAC Technician - An employee; a person that can accurately diagnose hvac failures and repair them correctly (within reason).

HVAC Design professional - A real book smart dude that can work up numbers on paper and tell someone else how to build a hvac system. In some extreme cases they even have college degrees in Engineering.

HVAC Guru - A guy that uses the correct formal calculations to aid him in prescribing a comfort solution based mainly on his years of experience and competence proven through examination.

Homeowners seem to think just because they called a "company" they should be getting the guru. Guess what cheapskates you get what you pay for and good design work isn't cheap. Now start asking for credentials of a person and not a company and be willing to PAY for their hours of design work and experience, more than just a standard service call. I am talking about severl hunderd dollars for a good road map to guide most anyone through the installation process. I mean why would a guru want to spend hours telling you how to install your own system or let some other company use your design for free. Now get off the bucks and quit whinning about not being able to find a guru. They are out there I promise.

[ciltep]

You probably mean "get out the bucks"--I don't ride too many bucks.

I'm willing to pay for quality. The problem is, with all these guys undercutting each other, the quality guys are hard to find. As I said, I don't think most people even think much about their HVAC. Most people probably wouldn't even complain about the things I'm complaining about, but I'm a bit of a perfectionist.

I'm willing to pay a couple hundred bucks to have a good system mapped out for me, but whose to say they won't just b/s me anyway? They could tell me that they performed the load calcs according to Manual J and the duct design according to Manual D, but how would I know they really did?

You see what I'm getting at? Any schlop can put together some papers and show them to someone and say here are the results of your calc. I've said before, I'm uneducated in this area, so I'm trying to pick a few things up so that I can tell if the wool is being pulled over my eyes.

Until that time, I'll keep my "bucks" in my pocket and hope for some more constructive feedback.

Oh, my zip is 52401. Thanks.

[Steve Wiggins]

Look ciltep, anyone can be precise, exact, anal, perfectionist....whatever you want to call it if:

1. The sun never changed position in the sky
2. The RH never changed throughout the day
3. The same number of people are always in the house
4. The seasons never changed
5. The air filter never got dirty

But reality is ALL these things are variable. It's just not possible to address all these things exactly. You can be paralzyed by analyzing it all day long and never come up with the "correct" solution.

It is best to find your guru through years of preventive maintenance and relationship building. Those that haven't shelled out the bucks to do this research get stuck with a big pile of crap. Guess what, a pile of crap covered up with dirt is still a pile of crap.

So find your guru and afford him the time and money to rip it all out and start over. We cannot continue this "constructive feedback" to the point of teaching you how to DIY. We all know that is what you are after no matter how well you try to sugarcoat it.

[pstu]

Given the difficulty in finding a pro who can offer Manual J and Manual D, it might be time to get a copy of HVAC-CALC from the red button near the top of the page. The main thing in using this, is measuring the dimensions of your house. The rest is either easy, or you can guess without making much error. A couple hours work ought to get you your first Manual J report, and it does offer some help on duct sizing -- although not Manual D. One of the important things on the report will be recommended airflow for each room.

The #1 thing that I see, is the possibility the duct sizing is just not large enough. Even if you cannot locate a pro to do Manual D properly, at least you can get most of the benefit by (probably) getting larger ducts. Personally I am agnostic whether you DIY or get a pro, I am confident the results will be better with a pro but each person has different circumstances.

My final straw in buckling down to do HVAC-CALC room-by-room, is when a local company started to show me a Manual J report and they got a room size wrong. That gave me the motivation to do *that* report DIY, at the same time I would have welcomed them returning to correct their mistakes but that company acts a little weird and has not acted too interested in the business. Perhaps for the original poster, now is the time to get HVAC-CALC and use it.

What I expect is, something or other in the Manual J reports will beg to be discussed with an HVAC contractor. Very possibly a report showing that you need a given airflow, and the duct system is not able to deliver it. If nothing else, you should be able to identify duct sizing that will allow your airflow to be under the feet/min limits in Manual D.

By all means we would like to take the high road and get one of the better pros to diagnose this problem, but the homeowner here may have to settle for what he can get.

Best of luck -- Pstu

[ciltep]

Never claimed I was trying to DIM. I laid out what I have and what my complaints are while looking for advice. If someone had said, "all you need to do is change your supply trunk ducts from 8 x 14 to 8 x 18," I probably would have done that--snapping sheetmetal together doesn't take a Ph.D.

Obviously, my concerns require a fix that is much more involved than that. However, if scrapping my entire system and duct work is the solution, then you pros ought to move to Cedar Rapids. Honestly, in my neighborhood alone, there would be hundreds of homes that need to be redone. Could be tens of thousands city wide.

So, either I'm too picky, or everyone around here has a crappy system. Maybe I should just live with it. We'll probably build again in three years as this is a jumper home. I can always let the next guy live with it and use what I've learned to do it better next time. Like I said, most people that I've told about my issues don't really seem to notice it. I probably shouldn't expect so much precision, but in my job, if I'm off a little bit, people die.

[dash]

Originally posted by ciltep
Never claimed I was trying to DIM. I laid out what I have and what my complaints are while looking for advice. If someone had said, "all you need to do is change your supply trunk ducts from 8 x 14 to 8 x 18," I probably would have done that--snapping sheetmetal together doesn't take a Ph.D.

Obviously, my concerns require a fix that is much more involved than that. However, if scrapping my entire system and duct work is the solution, then you pros ought to move to Cedar Rapids. Honestly, in my neighborhood alone, there would be hundreds of homes that need to be redone. Could be tens of thousands city wide.

So, either I'm too picky, or everyone around here has a crappy system. Maybe I should just live with it. We'll probably build again in three years as this is a jumper home. I can always let the next guy live with it and use what I've learned to do it better next time. Like I said, most people that I've told about my issues don't really seem to notice it. I probably shouldn't expect so much precision, but in my job, if I'm off a little bit, people die.




Though I don't agree with Steve's attitude,he's correct,you need a Pro.


You need a much more accurate evaluation of you cfm needs per room and sizing of the duct system than can be done on the net,without plans and complete info..

We could give you a guess as to size,then when all the work is done,and it's still not right??

My guess is all the trunks and branch ducts are too small,oversize them ,and air flow will be to great for proper operation,that's why we don't want to guesss.

[ciltep]

Thanks PSTU and Dash. Appreciate your advice and your demeanor. We can stop posting on this thread. I've got my answer from you guys. Thanks.

[Steve Wiggins]

I normally don't have good demeanor to posters that refuse to fill out their profiles....that is just rude.

[jacob perkins]

I just skimmed over the thread...so I might not have the facts,but you want to do it yourself or check what you have ?

buy the manual d and read it. fairly simple text. if you have specific questions about it,or just want to discuss your new found knowledge ,there is a website you can try www.hvac-talk.com.

good luck

[Edited by jacob perkins on 02-04-2006 at 06:01 PM]

[jacob perkins]

Originally posted by Steve Wiggins
I normally don't have good demeanor to posters that refuse to fill out their profiles....that is just rude.


yes steve, you are sometimes a rude person...and if you believe what you read on the profiles then you aint too bright either

[arc8]

Thanks PSTU and Dash. Appreciate your advice and your demeanor. We can stop posting on this thread. I've got my answer from you guys. Thanks.


But you haven't got an answer from me!

I'm also a perfectionist when it comes to installing HVAC equipment.

There are ways to weed out contractors, determine good contractors versus not so good ones.

First, they must performed a heat load calculation. forget about guessing and using ductalators when the equipment hasn't been determined yet.
Note: if a contractor gives you a heat load report and didn't measure your house, then stay away from them

Second, once you get a real heatload report, you should look for the proper equipment on that report. Note: a 24,000 heat gain does not mean you get a 2 ton system. i haven't seen too many 2 ton systems that can remove 24,000 btu's. So watch out for those.

Third, then they should be able to use the ductalator to determine the correct duct size.

I'm willing to help you determine a pro contractor. If you need help with your proposal/s to figure it out, just email me! it should be posted.

Me

[tinknocker service tech]

Originally posted by ciltep
Thanks for the responses thus far. However, I really am a novice. I really don't understand all the cfm talk. Are you saying I can adjust the air handler to lower the cfm? Is this advisable?

Also, just so I am clear (my terminology may not be correct), I have 5" snap together supply run pipes. My supply trunks that feed those pipes are roughly 8x14, but the plenum is much larger than that. The cold air return run is the same size 8x14. However, when it gets back to the furnace, before shooting downward, it widens out dramatically. The vertical part that then runs down almost to the floor and then over to the furnace is 10 x 25.5. That part is about 8 ft. tall and runs down then kind of elbows over and once it actually poors air into the furnace it's 16 x 25.5. That's roughly the size of my filter. I didn't want to paint a picture of the cold air return only being 8x14 when it feeds back into the side of the furnace. That isn't the case.

Does that make a difference with respect to some of the previous comments? Sorry to sound naive, but I am. Is the manual D something that a complete novice could attempt to get through?


lets start over
the 25x10 riaser is ok
the duct it connects to 14x8 is to small and noway will it supply 1600 cfms of air. it needs to be made larger
the returns in the house need to be looked into also as to make sure there are enough for the size unit you have

the supply dusts of 14x8 are shy also and need to be made larger in both derritions. how large depends on how much air flow you need on each side

would like to help you more but with out seeing what you have so it can be sized properly this is the best that can be done

as far as hvac guru well it time to come back to earth, there is no such thing. some guys are better then other or know more then other but guru yea ok

find someone that is willing to listen and talk to you
look the system over and make sugestions on what you need
tell him all the problems you have with the system and listen to what he has to say

if he knows what he is talking about he will make enough sense to you ao you understand what he is saying

if he wont listen or explain in detail then mave on to the next guy.

35 years doing things wrong doesnt mean good just no one questioned them

[dan sw fl]

Originally posted by ciltep
I would love to hire a professional HVAC Contractor. Unfortunately, around here there are a ton of contractors but none that I would call professional based on your standards.

Now, I'm not saying they don't know their stuff, but none seem interested in doing a load calc for each room and a duct design based on Manual J and Manual D, so maybe they are just lazy.

I can't do any worse than the random rules of thumb that I'm being quoted and it'll probably be a step up from every other new const. home around here who uses these guys.

At least the HeatPro calc gives me a rough estimate of output I need.

I did mispeak earlier.
My supply runs are 6" not 5".

6" versus 5": ONLY mistated flow area by ~40%.
Perhpas, other descriptions are not well stated.

How much did you offer for the HVAC contractor(s)
for a comprehensive evaluation?

"At least the HeatPro calc gives me a rough estimate of output I need."
... and You don't care to share results ? ??

[aaf2000]

4 ton in a 2000sf house may or may not be oversized. I can tell you that it would take alot of glass facing east and west to come up with this kind of heat gain. I have 2000sf houses scattered across eastern Iowa that only required a 75k 2.5 ton system. I just finished up with a house out by West Branch. It was 1410 square feet and required a condenser with a 2.5 ton designation. The house had a sensible load of 20266 btu and a latent of 3208. The only way to get there with the equipment I use and the coils that are made available to me was with a 2.5 ton condenser.

Regardless, like everyone else said, your ductwork is too small. On a 4 ton system if the returns are split up equally on each side of the furnace I use 20x8 for the return duct. I also try to use something bigger than 25x10 for the return drop. 1600cfm through a 25x10 is close to a tenth of an inch of w.c. Thats too much in the return side, for my tastes.

[ciltep]

Sorry about the mistate. The HeatPro calc suggested output of about 75k and suggested trunk ducts of 8 x 18. Like has been suggeted, I should talk to a Pro at this point. Sure, I could replace the trunk ducts. That wouldn't nbe that difficult to do. My layout is pretty simple. The house is essentially a giant rectangle--the only side that has some variance from a straight line is the front. I guess what I'm saying is that it doesn't have a lot of bends, corners, etc.

aaf2000. Where are you located at? West Branch isn't too far from here.

As far as windows, because someone asked, I've got about 360 sq. ft. of window area in the house. Most of it, over 50, west facing.

[ciltep]

Originally posted by tinknocker service tech



lets start over
the 25x10 riaser is ok
the duct it connects to 14x8 is to small and noway will it supply 1600 cfms of air. it needs to be made larger
the returns in the house need to be looked into also as to make sure there are enough for the size unit you have

the supply dusts of 14x8 are shy also and need to be made larger in both derritions. how large depends on how much air flow you need on each side

would like to help you more but with out seeing what you have so it can be sized properly this is the best that can be done

[/B]


I'll try to post a pic later so that you guys can actually see the install. Thanks for the advice that I've received thus far.

You asked about returns...I've got 4 on the main level and one in the basement. 3 are in bedrooms and are all sized the same. They are at ceiling height and span between two studs and have grills that are probably 8 inches in height. I'd have to measure them to be sure. Maybe I'll post pics of them as well. So, 3 of them are approx. 8" x 16" but all the air flow goes down through the studs. There's one in the living room that spans three studs, so it's about 8" x 32". The one in the basement is at ceiling height (note basement is unfinished and there is a plastic attachement for the grill at floor level) it's also 8" x 32".

Thanks for the advice.