Is there a chart out there...

[apex_predetor]

Hello all,

I was wondering if there was a chart out there that can give me the amount of supply lines (or floor/celing openings) that a particular sized line can handle?

I have a few different contractors telling me that different sized ducts can adequately "handle" a particular number of runs and they aoll seem to reference some type of chart that Ic an't find online.

Thanks

[2old2rock]

Manual D
If you can't get that, rough estimation is times 2 plus 2. But you really don't want to go with a rough estimate, unless you're willing to possibly sacrifice your comfort.
Manual D has all the info you need.

[beenthere]

They are probably using a ductulator.

And just using a rule of thumb on its friction rate..

[numbawunfela]

Hello all,

I was wondering if there was a chart out there ....

This is the kind of question where you will end being certain that we are not answering you straight, instead urging you to buy some book you do not want to thumb through to find the answer.

But in all honesty the answer is not something that can possibly be shown on a chart - there are too many variables involved. It is like asking for a chart to show how to interpret a woman's moods... ;)

If you think your contractor is fleecing you, you need to develop better relations or get another contractor.

[pecmsg]

Hello all,

I was wondering if there was a chart out there that can give me the amount of supply lines (or floor/celing openings) that a particular sized line can handle?

I have a few different contractors telling me that different sized ducts can adequately "handle" a particular number of runs and they aoll seem to reference some type of chart that Ic an't find online.

Thanks

From your previous Posts


WHy would I ahve to "pay" in addition to something that is, what I think, standard operating procedure?

What exactly there should cost me in addition? I can see possibly the Manual J, or Manual D calculation but lets be honest here, that isn't that difficult. I have enough experience and knowledge with fluid mechanics/dynamics, and thermodynamics to do the layout myself, but that would take me forever to figure out the fowrates, friction losses, etc... THat's why I want an experienced contractor! Very detailed Manual J calculators (spreadsheets) are available online, or through books available online.

I guess I digress. What exactly is not STANDARD items on my list. I would provide the scale plan-views (blueprints). All the have to do is tell me where the registers go, what type of duct is going to be used and be able to defend their decision. Fairly standard things I would assume, especially with a permit involved.

Thanks for any more info.


Makes sense about the Manual J/D calcs. I wouldn't expect them in the free estimate period, but I do expect them to be used to justify or defend the ultimate design, as well as I wil have them reviewed outside of my chosen contractor for accuracy and completeness.

As far as the T&M I would only require a breakdown for LAbor (with estimated hours total to comlete), and materials. I don't want an hour-by-hour breakdonw so I can figure out the profit/mark-up. I definetly intend to get an itemized quote for the materials with out question. We can all find the pricing of these online anyway.

thanks for the info


Yeah, that would be in an ideal world, but I am just not that trusting of a person especially when it come to a major chunk of cash, and in an industry that isn't all that familiar to the general public.

To stand back and let them do their job becasue thy are all professionals is a statement that does not sit well with me. I am a professional and we are checked and rechecked over and over again. This all while being highly educated and licensed by the state, so I don't presume not to analyze and verify everything that s given to me by a company that is not regulated by much of anything.

Sorry if I hit a nerve with some of the professionals here but I think you can all understand that I want satisfaction that the job has been done correct, the first time.

Thanks for all fo the help folks


You would be providing basically what I am looking for, except for the materials and labor breakdown.

Why is it that some of you out there feel as if it is completely unacceptable to get a material and labor breakdown?

Is that now how all homes are built? The material and labor is broken down separate from each other. All other cotractors providing cost estimates are expected to provide a cost for materials, and a cost for labor, why not the HVAC folks here? What is there to hide?

Thanks again for all of the info.

And my personal favorite is:


Why the animosity or offense when I question some practices?

I believe that there is a bit of a difference between a Licensed Profesisonal Engineer and a HVAC Installation company.

Sorry if I offended any of you...

Thanks for the info..

Yes you did offend several. You are the “Licensed Professional Engineer” DO IT YOUR SELF.:patriot:

[seatonheating]

Oh geez, did he start another one?? ME head hurts.

[numbawunfela]

Holy cow!! :eek2:

I might bump this thread a few times to make sure your history preceeds you the next time you ask for help on the forum to do a DIY project apex_predetor.

Thanks a million pecmsg

[GREGHVACGUY]

O-no not again.Just pick a guy who will do the job right. Let him do his job we dont tell Engineer's how to do there job we just fix what thay dont do right.
Here is your break down 10,000 total. 100 for parts,100 for labor, 9800 to put up with you s**t. price less. How are you paying for that(cash only all up front) that is how we deal with you.

[samtheman]

we don't tell you how to drive trains, and you don't tell us how to do our job.

[apex_predetor]

Like I said before; I wasn't trying to offend anybody. I am informing/educating myself on the process. If you feel the need to keep the information a secret then that is your perogative. I feel as if the job is being done correctly there is no need to "hide" anything.

I also thought that the reason for the forum was to educate and to help consumers not get ripped off and to help your industry? some people are helpful and others are just not, but I digress...

I do know that there are many variables that go into determining the proper duct supply lines, but more than one of the contractors I met with referred to checking some chart to determine off-hand if the supply proposed at the site inspection waould be appropriate or if it would need to be larger?

Manual J and D has been used by each contractor and the Manual J has been provided to me by each (for free).

Thank for the information to all that helped, or tried to answer my questions. to all else, well...

thanks again...

[seatonheating]

You just answered your own question. Let me clue you in, it is one of the manuals!!


I know what's going on here. You are trying to do this yourself and want someone to give you some magic formula to build your own ductwork!! Not gonna happen buddy.

[apex_predetor]

I'm not trying to do anything myself. Each of teh contractors that have given me proposals have given me their load calculations and duck schematics with their proposal. when I ahve questioned their dimensions, or asked as to how it was calculated I was given an acceptable asnwer from each one of them.

I just like to check calculations to be sure. It settles my curiosities. Check one or two here and there to see if I get a similar value. If that happens it is a safe assumption that the rest of the design is correct. I don't think that it is out of the question to imagine that there are companies out there that RIP people off, especially cutting corners since mostof this work can not be seen after it is completed, wrapped, sealed and closed in.

I have been burned by trusting an HVAC contractor in the past that was supposed to be very reputable, now I am scared to get burned again. Especially since this is such a large percentage of my renovation budget.

Ic ould bust out the fluid mechanics books and get to some value, but I know there are assumptions made to make this calculation easier and more emperical.

thanks for any of you who wish to help.

[heaterman]

Manual D
If you can't get that, rough estimation is times 2 plus 2. But you really don't want to go with a rough estimate, unless you're willing to possibly sacrifice your comfort.
Manual D has all the info you need.

That certainly is old school but was the standard around these parts for years. Might still be with some. It is better than just a total guess. Really only comes close to working if it's 8x duct with average length 6" runs using standard fittings. Disclaimer::::::: Some math required! :) :) :)

[mchild]

I'm not trying to do anything myself. Each of teh contractors that have given me proposals have given me their load calculations and duck schematics with their proposal. when I ahve questioned their dimensions, or asked as to how it was calculated I was given an acceptable asnwer from each one of them.

I just like to check calculations to be sure. It settles my curiosities. Check one or two here and there to see if I get a similar value. If that happens it is a safe assumption that the rest of the design is correct. I don't think that it is out of the question to imagine that there are companies out there that RIP people off, especially cutting corners since mostof this work can not be seen after it is completed, wrapped, sealed and closed in.

I have been burned by trusting an HVAC contractor in the past that was supposed to be very reputable, now I am scared to get burned again. Especially since this is such a large percentage of my renovation budget.

Ic ould bust out the fluid mechanics books and get to some value, but I know there are assumptions made to make this calculation easier and more emperical.

thanks for any of you who wish to help.

I'm a HO and I have to agree completely with what every Pro has told you (words and attitude). You have a way of marginalizing everything that others do and think the whole industry boils down to a couple of rules of thumb. A real pro doesn't use rules of thumb but you want to test their work/design with rules of thumb.

You have stated that every contractor performed a Man J and D, provided documentation, and answered your questions with appropriate responses. But you still want more?

If you are so danged worried have the contractor that gets stuck with your job guarantee that the TESP is not greater than X and the duct leakage will not be greater than Y. Then get out of his way and let him do the work. Jeezzz!!

[seatonheating]

I'm not trying to do anything myself. Each of teh contractors that have given me proposals have given me their load calculations and duck schematics with their proposal. when I ahve questioned their dimensions, or asked as to how it was calculated I was given an acceptable asnwer from each one of them.

I just like to check calculations to be sure. It settles my curiosities. Check one or two here and there to see if I get a similar value. If that happens it is a safe assumption that the rest of the design is correct. I don't think that it is out of the question to imagine that there are companies out there that RIP people off, especially cutting corners since mostof this work can not be seen after it is completed, wrapped, sealed and closed in.

I have been burned by trusting an HVAC contractor in the past that was supposed to be very reputable, now I am scared to get burned again. Especially since this is such a large percentage of my renovation budget.

Ic ould bust out the fluid mechanics books and get to some value, but I know there are assumptions made to make this calculation easier and more emperical.

thanks for any of you who wish to help.

If every contractor you have asked has given you an acceptable answer why are you bugging a bunch of strangers on the internet about it?? Something just doesn't seem right here.

Oh, and quit making their life a living hell by second guessing everything they tell you. If you don't trust them then why the hell would you trust us?

[TSASteve]

hahahaha

[sprintmj19]

Each of the contractors gave you their load calcs and duct calcs for free???

I guess they know exactly what they're worth.

[beenthere]

I'm guessing they gave loads calcs. And even a drawing print of duct lay out with (sizes maybe).
But, no info on friction rates.

Other wise, you would be able to compare them and ask each for the manual D calcs.


Bottom line. There ain't no sheet.

[Shophound]

You're going at this all backward. You are the end user. Cut a contract with your HVAC installer that a Certified Air Balance (CAB) will be performed by an independent air balancing firm after the system is installed and brought online. You hire the CAB consultant.

Further specify any load calculation performed (cost of which will be added to bid) will include room by room design air flow specifications. When the CAB testing is performed, allow 10% on either side of design target as acceptable actual air delivery to each room.

It is the contractor's responsibility to design and install his system so it meets these specs. Your end is to get it in writing so you have recourse if expectations are not met. If you do not inherently trust the system design capabilities of your chosen contractor, you should then speak to a mechanical engineer. If you believe you can NEVER trust the contractor to design the system correctly, have a competent mechanical engineering firm design and stamp it. Then hold the contractor to those specs given by the engineer.

This will cost more, but the level of satisfaction you apparently want does not come cheaply. Quality and cheap are not synonymous in terms of an undertaking this extensive.

[seatonheating]

You're going at this all backward. You are the end user. Cut a contract with your HVAC installer that a Certified Air Balance (CAB) will be performed by an independent air balancing firm after the system is installed and brought online. You hire the CAB consultant.

Further specify any load calculation performed (cost of which will be added to bid) will include room by room design air flow specifications. When the CAB testing is performed, allow 10% on either side of design target as acceptable actual air delivery to each room.

It is the contractor's responsibility to design and install his system so it meets these specs. Your end is to get it in writing so you have recourse if expectations are not met. If you do not inherently trust the system design capabilities of your chosen contractor, you should then speak to a mechanical engineer. If you believe you can NEVER trust the contractor to design the system correctly, have a competent mechanical engineering firm design and stamp it. Then hold the contractor to those specs given by the engineer.

This will cost more, but the level of satisfaction you apparently want does not come cheaply. Quality and cheap are not synonymous in terms of an undertaking this extensive.

He's going to read this and do what Chris Griffin does on Family Guy and go "HUWAH".

[Some Dude]

Why didnt anyone call me.

[numbawunfela]

Like I said before; I wasn't trying to offend anybody. I am informing/educating myself on the process. If you feel the need to keep the information a secret then that is your perogative. I feel as if the job is being done correctly there is no need to "hide" anything.

Seems as though I kinda predicted that response:


This is the kind of question where you will end being certain that we are not answering you straight....

And this one:

I have been burned by trusting an HVAC contractor in the past that was supposed to be very reputable, now I am scared to get burned again. Especially since this is such a large percentage of my renovation budget.



If you think your contractor is fleecing you, you need to develop better relations or get another contractor.

Apex - the fact that you even got a manual J done is a HUGE point in favor of your contractor.

If you want to know how to find a good contractor, and then see if the ones you have spoken with meet any of those criteria - it may be a good place to start.

That is a conversation the guys here will be willing to have.

[Some Dude]

Seems as though I kinda predicted that response:



And this one:





Apex - the fact that you even got a manual J done is a HUGE point in favor of your contractor.

If you want to know how to find a good contractor, and then see if the ones you have spoken with meet any of those criteria - it may be a good place to start.

That is a conversation the guys here will be willing to have.

Or just start another thread.:oops:

[pecmsg]

He says it better then I do.

[jeff520]

Quote: I'm not trying to do anything myself. Each of teh contractors that have given me proposals have given me their load calculations and duck schematics with their proposal. when I ahve questioned their dimensions, or asked as to how it was calculated I was given an acceptable asnwer from each one of them.


Seems to me that if you have schematics from more than one contractor and the duct dimensions are basically similar then either they are all correct (most probable) or they are all wrong (unlikely, but possible if they used similar rules of thumb).

If the results are all different, go with the contractor using the largest ducts! Too much duct will only hurt your wallet for the installation, the result should be a quieter system that runs a little more economically.