Duct Branching

[pjsullivan]

I'm a home inspector and I'm seeing this more often. Essentially, there's a distribution branch run off of the main plenum of a forced air unit. This branch is then split into two (a "Y") without the use of a "triangle" junction box, AND the split is NOT equal in size (one large branch, and one small). Then further down the larger branch, there's another split without a junction box (again one large, and one even smaller branch). Many of my customers who complain of poor airflow have this configuration. Is this type of thing proper, and if not, what is a better configuration. I would think that no branching would be best. Any help appreciated.

Peter.

[Steve Wiggins]

Dude you are freakin cracking me up......hahaha

The junction boxes you speak of are the worst way to run a duct system. The wyes you see are the best.

[Irishmist]

Peter: don't know if you are referring to a new or old home, where you come across this. Where I am located (Ohio Valley) it is not at all uncommon to come across duct systems in older homes (vintage 50s and 60s) that I refer to as "graduated duct systems." On these galvanized duct systems each time a branch comes off the main trunk, there is a reduction. The transition at this point resembles a "y" in its configuration, but is really a reducer. At each branch the reducer transition is in place. These are actually excellent systems for air distribution as each time a branch lead comes off, the trunk size is reduced accordingly maintaining good pressure within the system. The only reason these systems are not used today is cost. With the number and type of fittings required, the new construction market makes it prohibitive. I couldn't tell if you were referring to round or rectangular duct, but all this duct in these systems is rectangular, even the branches. One thing to note. In these systems I am referring to, there is a volume damper at each one of the transitions to help balance the airflow throughout the system. I am curious. Is it normal procedure for inspectors in your area, or are you just that much more thorough in getting into the air distribution systems of the hvac system? Around here, the home inspectors some of whom have more background in mechanical systems than others usually look at the equipment and note, "yep, that there's a furnace all right."

[pjsullivan]

Dear Mr. Wiggins:
I'm glad I made your day. BTW, I'm just down the road from you in Round Rock. Perhaps I'll have the pleasure of inspecting your work some day ... then we'll see who has the last laugh. Anyway ... here's a picture. You tell me ... is this kind of thing proper?

http://ww2.imagewiz.net/images/hvac1/178312_Img009.JPG

[Steve Wiggins]

Yes that is proper and thanks for the pic. Some cities want to see mastic on the vapor barrier but I wouldn't ever recommend that.

As for inspecting my work let me let you in on a little secret. I am a design professional and you are not. Challenge me and you will lose.

[duc dowg]

Mr Wiggins,
I to am amused by you. Keep it up.We all know inspecters suck. If he was any good at his job he wouldn't have to ask a thing like that.lol lol lol lol

[Irishmist]

those pants seem to be a little short in the "rise."

[davidr]

Peter a lot of times that type of duct design has so much pressure drop over the various fittings it just can not properly deliver airflow.
We have gone in on jobs before & renovated duct systems where we had to remove this type of design.
It may be ugly but if it delivers airflow & BTU's in the proper quantity to where it is supposed to then no issues.
Problem is most of them don't even come close.
Irish,if you are ever in Frankfort look me up.

[tinner73]

[QUOTE]Originally posted by pjsullivan
Dear Mr. Wiggins:
I'm glad I made your day. BTW, I'm just down the road from you in Round Rock. Perhaps I'll have the pleasure of inspecting your work some day ... then we'll see who has the last laugh. Anyway ... here's a picture. You tell me ... is this kind of thing proper?

http://ww2.imagewiz.net/images/hvac1/178312_Img009.JPG
[/QUOT

now that's quality. i bet they can rough in the whole house in 5 hrs. :D

irish i completely agree with you. we have alot of the old graduated trunklines around here too.

[tin_fab]

Irishmist

That method is called the "static regain method" and I can tell you from experience that it is still used by people that want value rather than price (many still around, you just have to sell TO them). I only use rectangular, wrapped.

PJ

that system in the pic is junk. You are gonna have insulation failure where that lawn chair webbing and pan-ties choke that flex. Also if you instal flex systems you should at least stretch out the flex. I guess nowadays that type of install passes for cookie cutter homes.

[tin_fab]

Challenge me and you will lose

lmao

[Steve Wiggins]

http://www.iwebphoto.com/Clients/quality/Album5/reaganduct3.jpg

[Steve Wiggins]

Originally posted by tin_fab

I only use rectangular, wrapped.



Hahaha .....what kind of dream world are you living in?

[Backspin]

a lot of use of flex duct. Esp for a main trunk line. Poor quality of work, but yes some inspectors pass this kind of work.

[the_guru]

We have an inspector taking his job more serious than alot of other inspecters and u bash him =/.... he was asking for an answer to a legitimate question. dont get me wrong i think most inspecters are screwballs. but u cant knock him for asking,he's attempting to do more than most.last time i checked this was a useful site for learning

Appreciate his curiousity.

[tin_fab]

Hahaha .....what kind of dream world are you living in?

Dream world?? I am about 1500 miles and 180 degrees from texas

lmao

[pjsullivan]

Guys:

Thanks for the replies. However, there seems to be some minor disagreement in the group ...

Steve Wiggins said: Yes that is proper and thanks for the pic. Some cities want to see mastic on the vapor barrier but I wouldn't ever recommend that.

davidr said: Peter a lot of times that type of duct design has so much pressure drop over the various fittings it just can not properly deliver airflow. We have gone in on jobs before & renovated duct systems where we had to remove this type of design.

tin_fab said: That method is called the "static regain method" and I can tell you from experience that it is still used by people that want value rather than price (many still around, you just have to sell TO them). I only use rectangular, wrapped.

It seems that although "proper", this design may not be the best alternative. Since the builder is likely to use the same materials, can anyone offer a solution to provide better airflow to the various trunks?

I'm way out of my element here, but I promised my customer that I would do my best to help. FYI, this is part of a pre-sheetrock inspection ... normally I would refer the client to a pro, but in this case, I have to provide convincing evidence that the builder's HVAC installer could have done a better job.

Thanks for your help.

[Steve Wiggins]

Wait a minute......you said you were a "home inspector". Do you mean you are an inspector for the city of Round Rock?

You were comparing the triangle juction boxes to the metal wyes and yes the metal wyes are better. I never said a flex system was better than a rigid metal pipe system.

Yes, the-guru, you are right this site is for learning and I apologize to PJ for coming across as a smartass. Learn we shall.

[GradyWhite244]

Originally posted by tin_fab

Hahaha .....what kind of dream world are you living in?

Dream world?? I am about 1500 miles and 180 degrees from texas

lmao


I agree with tin fab. You want chicken salad or chicken sh**? Sorry I don't deal in chicken sh** & most builders won't pay for chicken salad. That's why I stay out of new construction.

[trane]

I welcome a educated inspector. If you do everything the way it should be then the only ones getting hurt by him are your lowball competitors.

[pjsullivan]

Dear Mr. Wiggins:

I am a professional real-estate inspector. I own my own company (visit my web site if you like). I am not a building inspector. I do many different kinds of inspections ... all the way from slab to finished product, and I am experienced and educated in many different aspects of residential and commericial construction. I am a "general practitioner" ... you are a "specialist". I know a few things about many subjects, whereas you know many things about a few subjects. I accept your apology, and I apologize for that "last laugh" jab.

I have a report to write ... What should I say about this duct design? Here's a first cut:

"The HVAC ductwork in the photo, although branched correctly, may not provide adequate airflow to the smaller diameter sections of the branches. Recommend a qualified HVAC professional evaluate and determine a course of corrective action."

I would like to be more specific about a remedy that uses the same materials. However, I do not wish to "pi** off" the builder's pro.

Any takers?

[Irishmist]

important clarification: tin fab's reference to "static regain method" was referring to my reference to a "graduated ductwork system" utilizing all rectangular fittings. Please don't confuse the system we are referring to with what is shown in this picture. We are talking about two entirely different systems. Correct me if I am wrong tin fab.

[Steve Wiggins]

(w) Specific limitations for ducts and vents. The inspector is not required to do the following:

(1) determine the efficiency, adequacy or capacity of the systems;

(2) determine the uniformity of the supply of conditioned air to the various parts of the structure;

(3) determine the types of materials contained in insulation, wrapping of pipes, ducts, jackets, boilers and wiring;

(4) operate venting systems unless ambient temperatures or other circumstances, in the reasonable opinion of the inspector, are conducive to safe operation without damage to the equipment; or

(5) operate a unit outside its normal operating range as reasonably determined by the inspector.

[pstu]

PJSullivan wrote:

>>I have a report to write ... What should I say about this duct design? Here's a first cut:
>>
>>"The HVAC ductwork in the photo, although branched correctly, may not provide adequate
>>airflow to the smaller diameter
>>sections of the branches. Recommend a qualified HVAC professional evaluate and
>>determine a course of corrective action."
>>
>>I would like to be more specific about a remedy that uses the same materials.
>>However, I do not wish to "pi** off" the builder's pro.

Like you I am in S.Texas, we are almost close enough to be neighbors. One of my good friends lives in Round Rock. I am a homeowner who tries to educate himself, perhaps you will forgive me for asking an ignorant question.

PJSullivan, I do appreciate an inspector who learns more than the minimum, and want buyers in general to be well protected against defects. But there is such a thing as raising false warning, and that is a holy PITA to the seller. During a recent home sale I had the unpleasant experience of an inspector raising false warnings. I want to ask you, what exactly is the basis for raising this as a homeowner problem?

I submit that the actual method of duct construction is not sufficient to say it "may" not provide adequate airflow. Of course if one of the duct experts such as Dash will give a contrary opinion, I will gladly defer to his judgement.

Requesting a Manual D analysis of the duct system would give professional evidence of its adequacy or inadequacy, but is that the norm anywhere in home inspections? Directly measuring supply airflow with a flow hood would also be professional evidence. But such a thing is so out of the ordinary that I have to wonder if it is really within the professional norms of the inspector.

It seems to me you have an equal basis for alleging any other deficiency of the HVAC system. How do you know the system is sized to the house's cooling or heat load? How do you know the airspeed is under the 700 fpm limit stressed by Manual D for flex duct? In each case the homeowner would benefit from having the system tested (except for cost of testing), but what is the basis for raising the original accusation? I submit that there is not enough basis.

My skepticism is colored by the fact my own attic ductwork resembles the picture you showed. I am not under any illusion that my house has great ductwork, but after several HVAC guys have looked it over, they have found various things to criticize but I don't remember any raising the objection you have. I have actually had measurements of supply duct flow made, and they are reasonable. After addition of some much needed return ducting, ESP for the system is in the range of .45-.60 inches of water column depending on filter loading, about .35 if the furnace is on low speed. Not ideal but with a variable speed fan not a source of big problems either. It seems if the construction method were going to cause pressure drop and airflow problems, the measured ESP would be higher and/or airflow would be lower.

Just a devils advocate thought. I am sincerely interested in learning what is right.

Best wishes -- P.Student

[Edited by perpetual_student on 01-08-2005 at 10:27 PM]

[pjsullivan]

First of all, I appreciate Mr. Wiggins for reminding me of TREC's standards of practice about what I am not required to do. Just because I am not required to do a thing does not mean that I am not free to do a thing; provided of course that I am well grounded in what I write. I know inspectors who often learn about a subject thoroughly, and offer opinions based on their well researched knowledge; however, they (and I) never imply that we are a professional. In fact, I always defer to the professional in my reports.

I'm simply trying to determine if something is installed correctly. The customer raised the issue, not I. He wanted me to research the subject, and see what I could find out.

As I'm sure you are all aware, homes in this part of the country are literally thrown together by immigrant workers who cannot even speak English. In fact, in my county, if you want a job as a building superintendent, you have to know how to speak Spanish (a sad situation). So, as a result, many homebuyers harbor a deep mistrust for builders because the customer rarely gets what they want because of miscommunication, etc. So, when the customer saw this (he's an engineer), he asked what I thought. I said "I don't know". He asked if I could find out if it's ok. I said "I would try". Hence, my question. I'm not trying to be a HVAC pro. That's why I came here. Isn't this forum for people who want answers to HVAC questions?

How about this ... forget the fact that I'm a home inspector. Pretend that this is my home. I have this ductwork. I'm concerned that the airflow may be inadequate. I have come here requesting a professional opinion about whether there is a concern or not. So far, I have received many different replies ... some say it's ok ... some say it's not. I've already spent way more time on this than I wanted to. Can anyone help me, or should I go somewhere else?

[pstu]

If you really want to learn what makes good duct design, you can buy the ACCA Manual D book for about $40. I did, it's not an easy read but the info is in there. What I expect you will find is that sizing is more important than type of construction. And I will say again that size needs to be measured against the job the HVAC system needs to do, how can you criticize the duct system without equally examining the AC system, and how can you criticize that with no knowledge of the heat load on the house? Lotta questions that are easier to ask than to answer.

Hope this helps -- P.Student

[-80guru]

PJ, how did you get in my attic? Seriously, That method used in the picture in my opinion is an abhorent way to install flex duct work. The Y branching method is fine if installed correctly. Is that amalgamation of ducts that I see installed correctly? NO! there is your answer. Is it going to be a problem? That is not a question anyone can answer except the technician who does an airflow analysis on that duct system. So tell your client to hire an HVAC professional to perform an airflow analysis. If that is not acceptable then you or anyone else cannot honestly answer if "It will be a problem".

[Steve Wiggins]

Originally posted by pjsullivan


"The HVAC ductwork in the photo, although branched correctly, may not provide adequate airflow to the smaller diameter sections of the branches. Recommend a qualified HVAC professional evaluate and determine a course of corrective action."



PJ, that statement is horribly inaccurate. You are going to have an a/c contractor dead in the middle of your xxxx.

Part of the problem here is there is no design requirement on the blueprints. You will find all sorts of other trades design but no hvac. The builders refuse to pay a design professional to draw out good design. Therefore all the decisions are left up to the installing contractor or his subs.

This notion you have of the smaller branches not getting enough air is weak. How do you know how much air should be coming out of the supply register? Even if you measured it with a balometer you still won't know because there is no requirement for that to be listed on the blueprints.

[mark beiser]

What it comes down to is whether the duct system was designed and sized properly for the fittings and materials used. I'll bet any of you a weeks pay that it is not, and the installer just tied all that together as the most convenient place to do it, using the least materials.

Ductwork run like that is very typical here in north Texas, and in my experience, is the cause of a lot of airflow issues.
Any time I see multiple wyes that close together in flex duct like that, I find badly uneven airflow.

At least they used metal wyes, those ductboard triangle things are total crap, and should be outlawed, lol.

[pjsullivan]

Thanks so much -80guru. I followed your advice, and informed my client that if he still has a concern regarding the ductwork, then he should contact an HVAC pro to perform an airflow analysis.

And thanks sincerely to all who replied. I will definitely be coming back here whenever I have HVAC questions.

[johnl45]

Originally posted by pjsullivan
Thanks so much -80guru. I followed your advice, and informed my client that if he still has a concern regarding the ductwork, then he should contact an HVAC pro to perform an airflow analysis.

And thanks sincerely to all who replied. I will definitely be coming back here whenever I have HVAC questions.
Now your acting like a true professional, good job.

[pstu]

A question I hope one of the more expert people will answer: Is the problem with this picture, partly that the Wyes are so close together? Can anyone explain why triangle boxes degrade airflow?

What can you see that will degrade airflow? Can you describe in a few words how it would be built better?

If there were a clear and simple answer, and the price were not thru the roof, I would probably pay to have it corrected in my own house.

Thank you -- P.Student

[dash]

There is nothing wrong with the wyes,or even tri-boxes,IF they are accounted for in the Man. D ,duct design.

In this case we have no information,to make a decision,as to what the airflow will be.

If you want to redo your duct system,it's Man. J,room by room,then a redesign using Man D.This will allow you to bring the ESP down to whatever you select,and provide even temperatures throughout the home.

[tinner73]

flex duct degrades the airflow. it is not smooth like the metal pipe. the smoother and squarer the duct, the better. the part here that gets me is even if you went with CHEAP round "stove" pipe it would be way better than this. it would be fairly close in price and you wouldn't need a
tin-shop. this way saves on labor mainly and what's more important than their bottom line anyway. i'm happy they don't do this around Chicago.

[pstu]

Dash, I have always consistently heard that message from you, "Manual D is the only way to be sure". Thanks for reassuring me that the universe is governed by natural laws and not by whims.

Although after the system has already been built, would not a flow hood test of each supply register (and maybe the returns too) give a valid after-the-fact answer?

Best wishes -- P.Student

[dash]

Originally posted by perpetual_student
Dash, I have always consistently heard that message from you, "Manual D is the only way to be sure". Thanks for reassuring me that the universe is governed by natural laws and not by whims.

Although after the system has already been built, would not a flow hood test of each supply register (and maybe the returns too) give a valid after-the-fact answer?

Best wishes -- P.Student

Testing would give you the total airflow delivered,thru the supply and return ducts,less any duct leakage.

This is valuable information,but you need to know what each rooms cfm should be(Man J),and what is the airflow thru the equipment(ie. without leakage).

[dash]

Originally posted by tinner73
flex duct degrades the airflow. it is not smooth like the metal pipe. the smoother and squarer the duct, the better. the part here that gets me is even if you went with CHEAP round "stove" pipe it would be way better than this. it would be fairly close in price and you wouldn't need a
tin-shop. this way saves on labor mainly and what's more important than their bottom line anyway. i'm happy they don't do this around Chicago.


Flex is not a problem,IF the Man.D design is for flex.Flex does not degrade airflow,poor design and install does.

[conrad1]

You are on the right path /do have an HVAC company check the design airflow airflow airflow 2nd only to unit size in importance the pic you showed actually looks better than most but that does not mean it is sized correctly to the unit or that the unit is sized correctly to the bldg. location have a manul j and manual d calc done

sorry dash I had not read the 3rd page before I posted you already settled it apologies for the redundancy

[Edited by conrad1 on 01-09-2005 at 11:59 AM]

[dash]

Looking at the photo,I'd check to make sure the wyes are insulated properly.

[tinner73]

dash...my arch nemesis;)...please tell me why an all flex system would be better than an all metal one.

[Steve Wiggins]

I mostly agree with Dash.

P. Student has some great points but they are in a perfect dream world. Nice goals to work toward though - keep going p.

One of my pet peeves is connecting the flexible duct straight to the boot box. When I walk through a new construction house I want to see clean shiney metal inside the box with a nice clean metal elbow making the turn.

The only place flex is ok (and in some cases preferrable) is between this metal elbow and a metal wye (or elblow and metal starting collar @ plenum.

My preference until someone talks me out of it:
1. Well sealed, easily accessable air filtering system

2. Metal plenums, screwed and sealed with clear silicone (or mastic)

3. Externally insulated metal boot boxes with metal elbows on them. Usually 3 way throw ceiling mounted on an interior wall with curved blade grille (not stamped face).

4. Flexible duct supported in the attic slightly up off the blown insulation. Ran in a way to provice the smoothest possible air flow path. Yes round metal is better but not practicle in the places we are asked to install it. And round metal is better than rectangluar metal, esp when the rect. in insulated on the inside.

5. No dampers. They are for inadequate duct designers and only hamper air flow.

6. Accurate thermostat location (usually close to return air intake) but definately NOT where supply air will blow on it. If two story home need one on each floor. Not in line with sunlight beam through windows. Not inline with fireplace radient heat. One or two extra conductors just in case. Digital but NOT programmable. Top plate wire penetration and wall hole SEALED air tight.

7. Outdoor unit secured level on its own poured concreted pad attached to the house so it won't tilt later. Mounted at least 10" to 12" away from the house so it can be washed on the backside.

8. TXVs & start kits are essential among numerous other safety features. I prefer recips over scrolls but that is purely opinion mostly due to noise and breakdown problems.

9. Crankcase heaters = longer compressor life no question. Most all equipment has been stripped of these features (#8 above also) to the detrement of equipment life and the benefit of manufacturers saving on cost.

10. Indoor cooling coils ARI match in new construction. Inspectors only look for that yellow energy tag on the outdoor unit to verify SEER rating. They have no clue of the indoor sections abilites or ratings. This is really sad for the home owner. Lifetime warranties can be denied because of this mismatch.

CONCLUSION:
There are SOOO many things a good inspection should reveal to the homeowner but 99% are mised by non professionals. This is a battle between TREC and the TDLR/TACCA in Texas. I think there is a need for these inspections but not by unqualified people. An inspector stating some problems and then saying the system should be checked by a professional only causes problems and doesn't help them. With some work in Austin I think inspectors and professionals can strike some sort of truce to help increase public trust.



[Edited by Steve Wiggins on 01-09-2005 at 02:31 PM]

[tinner73]

no dampers?? how do you regulate (direct) the airflow? whenever you put in a tee of any kind the should automatically be a damper installed.

recip over scroll?




i dunno about those Steve.

[trane]

Air will always take the path of least resistance. I don't know how you can get by without dampers. We put dampers in the main ducts anytime there is another duct going off from it and dampers in all supplies.

[Steve Wiggins]

Originally posted by tinner73
no dampers?? how do you regulate (direct) the airflow? whenever you put in a tee of any kind the should automatically be a damper installed.

The only tee I would see is the supply plenum. If your plenum is the right size (not those supplied by the manuf) and the holes are cut in the right locations you can get pretty close to predicting the air flow from each run. Since heat load are variable and duct sizes are not there is no way to be exact. If heat loads were constant and air flow to each duct was variable then yes I would agree with dampers.

Dampers (for balancing purposes) are an engineers crutch and should only be used when the symptoms call for it. All the residential dampers I have seen are left wide open anyway so why bother and hamper air flow?

[pjsullivan]

Steve:

What sorts of problems do you encounter with home inspectors? I'm sincerely interested in finding out.

My inspection of HVAC systems includes the following:
a. Check temp drop (14-22 deg).
b. Check temp rise (if manufacturer's specs available).
c. Look for visible damage to unit or heat exchanger.
d. Check for gas leaks.
e. Flame is correct color, size, and burns properly.
f. Blower is clean, and runs smooth.
g. Flue is secure, and has proper clearance.
h. Condensates are properly configured & insulated.
i. Pan is in good shape, and pan switch works.
j. Proper work space in front of unit & accessible.
k. 110V outlet & emergency switch are available.
l. Electrical wiring is secure and not a hazard.
m. Check for air leaks around plenums, and connections.
n. Check filters for correct size, and cleanliness.
o. Outdoor condenser is level, and runs smooth.
p. Suction line is well insulated and secured.
q. Shutoff panel is accessible, and properly wired.
r. Circuit breaker in main panel is correct size.
s. Size of supply wire is correct for installed breaker.
t. Look for visible damage to condenser (fins & fan).
u. Operate thermostats in heat, cool, and manual fan.
v. Location of thermostat is near return, not in direct sun, and not near supply duct.
w. And other stuff I'm probably forgetting right now.

I do home warranty inspections (1 year home whose builder's warranty is about to expire), and the #1 complaint is the HVAC system not delivering enough hot or cool air to various parts of the home. This type of thing is a really pervasive issue throughout the new home industry. Even custom homes use flex duct strewn all over the place. I inspect 300+ homes a year, and I have only once seen rigid metal duct in a new home. Is this just regional (Texas?), or is the problem a matter of builders not wanting to spend the extra money on a quality designed and installed HVAC system? I think you mentioned earlier that most spec homes do not have a system designed for the home, and I agree. I'll inspect a specific model of a spec home, and it'll have a 3.5 ton unit downstairs with a 2.5 ton unit upstairs ... the following week, I'll inspect the exact same layout two blocks away with a 2.5 ton unit down, and a 3 ton up. What's up with that? What's more, it's the same HVAC company doing the work!

You indicated problems between TREC & the TDLR/TACCA in Texas. What sort of solution would you offer to help mend the relationship in order to regain the public trust?

I understand the need for more qualified people in the inspection indusrty, but when we are faced with the abominations that pass for HVAC system ductwork of the like I've illustrated in brand new homes ... what qualifications do we need? All of the pros in this forum seem to agree that improperly designed systems are the root of most poorly operating HVAC systems. So why don't the systems get properly designed?

BTW, as of 01/2005 TREC now requires a professional inspector applicant to have 448 credit hours of approved coursework (it used to be 188).

It seems that whenever an inspector raises a flag, he gets shot down because he's not qualified to raise the flag. Fair enough, but if we can all agree that the systems being installed in new homes are basically crap, then what's wrong with raising a flag now and then? Just maybe if the builders have to call back the HVAC installers often enough, then things will get better over time (I'm propbably being overly optimistic).

Steve, you are preaching to the choir. I abhor using the phrase "Recommend a qualified HVAC professional evaluate ... etc". I wish I was more qualified to make sure that I was not wasting a HVAC pro's time ... but I have to know about foundations, grading, roofs, attics, structures, doors, windows, water heaters, plumbing, electrical systems of all ages, and all kinds of other stuff as well. There's just not enough time to learn everything.

Anyway, I'm rambling.

Peter.

[dash]

Originally posted by tinner73
dash...my arch nemesis;)...please tell me why an all flex system would be better than an all metal one.


Didn't say it would be better,just that properly designed,there is no air flow difference between the two.

Metal is more difficult to seal and insulate,and is seldom done correctly in Florida.I've never installed metal in my own homes or business(have in many others,in the 60's and early 70's).I don't see the value of the increased cost.

Of course Florida is all most exculsively ductboard and flex.

[davidr]

Originally posted by Steve Wiggins

Dampers (for balancing purposes) are an engineers crutch and should only be used when the symptoms call for it. All the residential dampers I have seen are left wide open anyway so why bother and hamper air flow? [/B]

Steve,I have to disagree with you on this one.
Dampers are there because no design process is 100%.
Things change in the field that don't allow the duct to be installed in the exact way the designer intended.
There are too many variables that can take place which will affect air distribution for them not to be installed.
If an adjustment needs to be made on start up to allow for airflow adjustment it is nice to have them there.

[pstu]

I just wish there were a way to get the real problem in your crosshairs -- absence of competent HVAC design. Kudos to you PJ, if you ever get a legit reason to nail those builders who make a mess of our HVAC systems!

-- P.Student

[Steve Wiggins]

Originally posted by pjsullivan
Steve:

What sorts of problems do you encounter with home inspectors? I'm sincerely interested in finding out.



Home seller calls me and says the "home inspector" left a report that says the "coils are dirty" and the system needs to be "serivced".

This happened to me recently and here is an example of how the call went:

I asked the home seller which coil the inspector was talking about (indoor or out). She didn't know and the inspectors report didn't specify. So I checked them both and both were very dirty as was the evap drain pan.
The indoor coil required removal to clean it and it had a non repairable refrigerant leak. Checked charge and system was low on refrigerant and the run cap was only half value µf so it ran the compressor but needed replacing.

When I told the seller of the problems she was very angry at me because she wasn't about to pay for all those repairs. She only wanted done what was on the inspectors report so she could sell the home. She didn't give a rip if the system worked correctly or not.

In her eyes the inspector was the ultimate authoritative professional and I was merely the grunt hired to "do what I was told".

The problem here lies with the wording the inspector used. The wrong word was "service". If the inspector had used the word, "evaluate" everything would have worked out.

Please please please all you home inspectors out there make sure you tell the customer to have their system "evaluated" NOT SERVICED by a licensed professional. Further state in writing that you are NOT a professional and that the licensed contractor is most likely to find things wrong above and beyond what was covered by your inspection. Systems cannot be serviced without evaluating them first.

The above example has happened to me more than once and I see a terrible problem developing in the state of Texas in this area. The end result was the HO was furious with me and refused to pay the bill. They will never call me again and am sure it will tarnish my reputation by them telling others. I did my job as politely and professionally as I could and still didn't gain public trust.

[Edited by Steve Wiggins on 01-09-2005 at 05:37 PM]

[Steve Wiggins]

Originally posted by davidr

Originally posted by Steve Wiggins

Dampers (for balancing purposes) are an engineers crutch and should only be used when the symptoms call for it. All the residential dampers I have seen are left wide open anyway so why bother and hamper air flow?

Steve,I have to disagree with you on this one.
Dampers are there because no design process is 100%.
Things change in the field that don't allow the duct to be installed in the exact way the designer intended.
There are too many variables that can take place which will affect air distribution for them not to be installed.
If an adjustment needs to be made on start up to allow for airflow adjustment it is nice to have them there.
[/B]

Changes in the field need to be reflected in the design and not corrected by a bandaid dampering system.

No one that I know ever checks cfm at each register to see if it matches the designed value. The only reason a damper would get adjusted is if a HO complained and then when the seasons change they are uncomfortable again. They just get tired of calling the contractor about it and put up with the discomfort. All the while the contractor is thinking he actually fixed the problem.

[Steve Wiggins]

Originally posted by pjsullivan

e. Flame is correct color, size, and burns properly.


Peter I am very worried about this statement.

1. What color are you looking for?

2. What size is the right size?

[Steve Wiggins]

Originally posted by pjsullivan

Size of supply wire is correct for installed breaker.


How do you determine this?

[davidr]

Originally posted by Steve Wiggins

No one that I know ever checks cfm at each register to see if it matches the designed value. [/B]

Well now you know at least one person,trust me there are others. :D
If we have a sizeable difference in how much CFM an area takes in heating & cooling we recommend zone controls.
If you take the time to adjust your systems there won't be as many unhappy HO's.
It is not about making the system perfect,this is not practical.
What it is about is making your customers comfortable & making sure they are getting what they paid for.
With that much confidence in your duct system design you should appreciate having it tested to verify your design has been achieved.
All it would do is give more credibility to your engineering skills.

[davidr]

Originally posted by Steve Wiggins

Originally posted by pjsullivan

e. Flame is correct color, size, and burns properly.


Peter I am very worried about this statement.

1. What color are you looking for?

2. What size is the right size?

Steve I agree with you 100%. :D
The only way to be sure an appliance is burning properly & safely is through combustion analysis.

[tinner73]

Originally posted by Steve Wiggins

Originally posted by davidr

Originally posted by Steve Wiggins

Dampers (for balancing purposes) are an engineers crutch and should only be used when the symptoms call for it. All the residential dampers I have seen are left wide open anyway so why bother and hamper air flow?



how would an open damper hamper the airflow.




Steve,I have to disagree with you on this one.
Dampers are there because no design process is 100%.
Things change in the field that don't allow the duct to be installed in the exact way the designer intended.
There are too many variables that can take place which will affect air distribution for them not to be installed.
If an adjustment needs to be made on start up to allow for airflow adjustment it is nice to have them there.


Changes in the field need to be reflected in the design and not corrected by a bandaid dampering system.



dampers are not band-aids they are valves. how else do you control the volume? how do you control the flow of water? with a valve (damper).



No one that I know ever checks cfm at each register to see if it matches the designed value. The only reason a damper would get adjusted is if a HO complained and then when the seasons change they are uncomfortable again. They just get tired of calling the contractor about it and put up with the discomfort. All the while the contractor is thinking he actually fixed the problem. [/B]


..if the homeowner complained then a damper would be the ONLY way to re-direct the airflow. dampers are cheap and as long you don't bury them under drywall, they should ALWAYS be installed.

[caliweath33]

I can't believe that PJ Sullivan is now trying to blame immigrant workers for this crappy duct design. First let me tell you that behind that desk designing these systems is an old us of a good old boy.I can guarantee you that the only language good old boy speaks is english and nothing else. Also parts lists are supplied from you guessed it the good old boy from behind the desk. The only difference you would have if you replaced the so called immigrant workers with 100% us of a good old boys would be very high employee benefits, sh##load of workers comp. Backed up on builders schedule and so on and so forth. You need a new job if all you do is use hard working people as scapegoats everytime you have to use your brain.

[41gasman]

pjsullivan. I commend you on your efforts to do a indepth
inspection for your customers.This is very rare around here.
I have been in a nasty little crawl of a home a week after there closing to install gas pipe(hard pipe of course).Only
to roll over and soak my shoulder in what was not quite
just water. The 4" sewer main was leaking and there was
a big white ring were the "water"had flooded and evaperated.
How this was missed I don't know.I know of one home inpector
around here who try's this hard.And sellers don'tlike him.
But buyers love him.I have seen him cause people to get
quite irritated. Because he really "inspects" a home.
It seems to me the way for you to really check a hvac
system would be to do what you all ready do.Than use the
hvac-cal that is sold here.That and a air flow hood would
very quickly put the ball in the installer court.Let them
prove you wrong.You just got to know they went by a"rule of thumb".And that's before the installers whith very little skill,or thought to a job well done.And in a big hurry!
Around here installers get a way with murder because of
the mild weather.Back to back to back 6"dia. 90's going
into wall stacks two floors up!!And the customer wants to
know why the bedrooms up stairs are so cold all the time.
It's called "hack and slash"here.I do mostly retro fit's
And it can be a real bear to fix alot of this and make
a buck at the same time.I love my trade a lot.And find
some of this stuff very embarrassing.But I digress.Good
luck with you efforts. And keep up the good work!

[cem-bsee]

again, ACCA manualJ is used to determine the load, given many physical parameters & the designer makes certain assumptions. manual S is used to size the equipment | unit. manual D is to design ducts for airflow necessary for the equipment and the loads. [ perhaps a local commercial plumbing shop will let you come & see manualD, one here did]

Same info are in ASHRAE manuals [ ~$150 ea ], which have LOTS of design info; in 4 volumes, one updated ea year. [ Engr school libraries may have <1990 vintage, $$$ have prevented most from just getting them since then. In fact, none in a 400mi radius of me had one! including Purdue, GA Tech, ... ]

regarding the ductwork, good insite can be gained just viewing the 3-4 pages of manD relative to "equivalent lengths" for the various fittings; eg: wye, tee, scoop take offs, etc.

remember that air is a fluid which can be compressed.

Leakage is a BIG concern along with duct sizing and its insulation.

[Edited by cem-bsee on 01-09-2005 at 08:14 PM]

[fat bob]

Originally posted by tinner73
flex duct degrades the airflow. it is not smooth like the metal pipe. the smoother and squarer the duct, the better. the part here that gets me is even if you went with CHEAP round "stove" pipe it would be way better than this. it would be fairly close in price and you wouldn't need a
tin-shop. this way saves on labor mainly and what's more important than their bottom line anyway. i'm happy they don't do this around Chicago.

I've heard that Chicago still requires cast iron drain pipes--no PVC--and armored power lines in the attic. That's good for plumbers and electricians, and I suppose makes for a better house. But I wonder, are Chicago's codes looking out for the trades or the homeowners? Maybe both.

[tin_fab]

armored power lines in the attic

No BX or romex except for 3'BX whips..all EMT conduit
No pvc for DWV OR potable....cast iron and copper
NO FLEX SYSTEMS...5'of flex or less and sheet metal required

Yes Chicago protects homeowners and requires trades to know their stuff

[kim]

Duct systems can be designed and constructed without dampers.

Dampers are for easy changes.
If you add an addition for example, dampers can compensate.

Too many people do not know how to design duct systems. They have a hard time balancing a system with dampers.
If I had a digital camara, I could fill the wall of shame section with pictures 20 times over.

Never could figure out how somebody was going to quess how much air is needed if they will not even do a load size.

[tinner73]

Originally posted by tin_fab

armored power lines in the attic

No BX or romex except for 3'BX whips..all EMT conduit
No pvc for DWV OR potable....cast iron and copper
NO FLEX SYSTEMS...5'of flex or less and sheet metal required

Yes Chicago protects homeowners and requires trades to know their stuff


technically bx is illegal. greenfield is ok. ALL wire should be able to be replaced. from what i see and read on this board Chicago has set their construction bar pretty high compared to some parts of our country.

[dash]

Originally posted by Steve Wiggins



When I walk through a new construction house I want to see clean shiney metal inside the box with a nice clean metal elbow making the turn.




5. No dampers. They are for inadequate duct designers and only hamper air flow.





[Edited by Steve Wiggins on 01-09-2005 at 02:31 PM]


Using a metal elbow ,instead of a flex one,only saves about 10 equivalent feet of duct.This has a very small impact on the FR or ESP.But to each his own.

Although Man. D recommends dampers at branch ducts,we haven't found them needed.With a branch duct and grille velocity of 600 fpm or less,the damper at the grille can reduce air flow by 30% without a problem.

With duct systems in hot attics,I doubt they would be used/adjusted very often ,in Florida.

[rimek]

To Tin-fab and Tinner 73-
quote:
--------------------------------------------------------------------------------
armored power lines in the attic
--------------------------------------------------------------------------------


No BX or romex except for 3'BX whips..all EMT conduit
No pvc for DWV OR potable....cast iron and copper
NO FLEX SYSTEMS...5'of flex or less and sheet metal required

Yes Chicago protects homeowners and requires trades to know their stuff
--------------------------------------------------------------------------------



technically bx is illegal. greenfield is ok. ALL wire should be able to be replaced. from what i see and read on this board Chicago has set their construction bar pretty high compared to some parts of our country.
___

I also am in Chicago and isn't it a treat to see these installs? All flex and ductboard- the only time I got to do a job in that stuff, I think it took me longer because I had to fasten the stuff so that it didn't sag,seal all the joints and I took part of it out anyway and put in steel because I couldn't stand to leave it looking like that. I was probably way too picky. But I don't have an opinion as to its quality, if it is calculated for in man D., dynamics should work. I don't know that I'd ever use it for return, tho'. Yes, Chicago is picky, but we deal with it.

[kim]

Originally posted by dash
Using a metal elbow ,instead of a flex one,only saves about 10 equivalent feet of duct.This has a very small impact on the FR or ESP.But to each his own.
[/B]

Depends on how the pipe is run. A long sweeping flez line has less resitance than an elbow.

[AllTemp]

Originally posted by pjsullivan
Dear Mr. Wiggins:

Any takers?

Home Inspectors provide a buyer a false sense of well being. How many of us have gone to a new homeowners to only hear them say the inspectors said... The Inspector said Crapola... And a perfect example is one is here getting ready to write a report that he has absoulutley no clue let alone a proffesional opinion about... The money spent on a home inspection just as well been used to wipe your axx ... Mr. Real estate Inspector I will praise the day when legislation finaly requires a written mechanical report be given by a license qualified proffesional. Knows alot about nothing is about what it's about!

Any takers.. You bet ya get a real job!