Am I dealing with ding-dongs?

[bicknell]

I've got a 11 year old house with dual 4 ton units (up/down config), and the upstairs has failed needing thousands in repairs. Thinking at that age I may do better to replace the units than repair, I've called in two people for estimates. I also have complaints that the upstairs has never kept up on hot days or kept the floor evenly cooled.

First guy quoted new everything, upgrading the upstairs from 4->5 ton. Of note he didn't recommend any more vents or returns (I had a return question, so I asked specifically).

Second guy is sending me two options in writing tomorrow, one with new everything, the other reusing the existing furnace, just new AC. Also a 4->5 ton upgrade. He noted there were not enough returns and quoted adding one, and noted the outside copper pipes were not big enough for a 5 ton high efficiency unit, so he quoted upgrading those.

The return thing got me looking, so I've found a lot of things online with "rules of thumb" for both return and supply sizing and it appears to me the downstairs (still running, keeps the floor comfortable) has returns matching the 100inch per ton return sizing (barely) and a similar number of outputs, but the upstairs is more like 320 sq in return, and 340 of supply (based on straight round pipe size, not accounting for runs/bends).

So I'm thinking the problem upstairs is not 4->5 ton, but rather lack of returns and supplies. Also, just upgrading without more returns and supplies seems like a bad idea if they are already marginal.

It seems to me both of these guys should have measured and counted all returns and supplies before quoting complete system swap outs. Am I dealing with ding-dongs or is that just not normal practice? Is it worth specifically asking for someone to do the calculation, and if so do I want someone independent to do it? How do I find such a person?

[dj3901783]

most of the estimaters I've seen are more salesmen than install/service tech. If there is a major error in the duct sizing of the unit, then a service technician should be able to tell just by looking at the pressures, superheat, subcool... I would find someone... a technician, who's experienced in duct design/sizing. Find out what's really wrong before you put in the wrong unit and or incorrect duct work...

[ampulman]

most of the estimaters I've seen are more salesmen than install/service tech. If there is a major error in the duct sizing of the unit, then a service technician should be able to tell just by looking at the pressures, superheat, subcool... I would find someone... a technician, who's experienced in duct design/sizing. Find out what's really wrong before you put in the wrong unit and or incorrect duct work...

I'm sure the readers would like to know your location and size/layout of your home. That's a lot of tonnage.

AM

[Jay 41]

I've got a 11 year old house with dual 4 ton units (up/down config), and the upstairs has failed needing thousands in repairs. Thinking at that age I may do better to replace the units than repair, I've called in two people for estimates. I also have complaints that the upstairs has never kept up on hot days or kept the floor evenly cooled.

First guy quoted new everything, upgrading the upstairs from 4->5 ton. Of note he didn't recommend any more vents or returns (I had a return question, so I asked specifically).

Second guy is sending me two options in writing tomorrow, one with new everything, the other reusing the existing furnace, just new AC. Also a 4->5 ton upgrade. He noted there were not enough returns and quoted adding one, and noted the outside copper pipes were not big enough for a 5 ton high efficiency unit, so he quoted upgrading those.

The return thing got me looking, so I've found a lot of things online with "rules of thumb" for both return and supply sizing and it appears to me the downstairs (still running, keeps the floor comfortable) has returns matching the 100inch per ton return sizing (barely) and a similar number of outputs, but the upstairs is more like 320 sq in return, and 340 of supply (based on straight round pipe size, not accounting for runs/bends).

So I'm thinking the problem upstairs is not 4->5 ton, but rather lack of returns and supplies. Also, just upgrading without more returns and supplies seems like a bad idea if they are already marginal.

It seems to me both of these guys should have measured and counted all returns and supplies before quoting complete system swap outs. Am I dealing with ding-dongs or is that just not normal practice? Is it worth specifically asking for someone to do the calculation, and if so do I want someone independent to do it? How do I find such a person?

Ding dongs, yes!

[dash]

Manual J,S,and D ,are what need to be done.Call until you find a contractor that can/will do these.


www.acca.org is where these are from

[bicknell]

Sadly, finding someone willing to do the work is proving difficult. I've now had two people tell me I didn't need all that. *sigh* It's frustrating to want to pay someone to do it (I'd rather spend a couple hundred on figuring out the right size, than $10k on a wrong sized system) and not be able to find them.

I'll keep hunting.

[targetman]

What's your location? Maybe one of the professionals on this site can help you.

[bicknell]

Suburb of Memphis TN. If anyone knows of a competent HVAC guy, I'm all ears.

[Daltex]

I just purchased the HVAC Calc program so I could do my own. I have the same problem as you regarding finding people willing to spend the time to do it right. You can click on the link at the top of the page and download a trial version to see it.

The size of the ducting per the tonnage as you mentioned, is only one part of doing it right. Finding out if you need to upsize or not is another part. Alot of if not most new installs are oversized systems running through undersized ductwork.

[aintitfun]

I WOULD LIKE TO CONGRATULATE EVERYONE, INCLUDING MYSELF. For clicking on something on the internet, that had the word ding-dongs in it.

[eglide99]

I WOULD LIKE TO CONGRATULATE EVERYONE, INCLUDING MYSELF. For clicking on something on the internet, that had the word ding-dongs in it.

MMMMNNNN ding dongs MmmmNmmm

[MB1211]

MMMMNNNN ding dongs MmmmNmmm

Me too.. I clicked on it cause I was hungry ....

[Shark207]

GREAT!!! Now I have to go to the store and get some ding dongs or ho-ho's and a mountain dew.

[bicknell]

I finally got a guy with some more clue. He wants to put a return in the one room without one, add a vent in one room, and add a vent in the hall; all while keeping a 4 ton unit. I'm waiting for his written quote later today.

I called back the first guy (5 ton, no additional vents and returns) and asked some questions. The story he wants to stick to is because his unit has a variable speed fan it can "overcome any duct problems" which is why he doesn't need to add any to do it.

[dash]

I finally got a guy with some more clue. He wants to put a return in the one room without one, add a vent in one room, and add a vent in the hall; all while keeping a 4 ton unit. I'm waiting for his written quote later today.

I called back the first guy (5 ton, no additional vents and returns) and asked some questions. The story he wants to stick to is because his unit has a variable speed fan it can "overcome any duct problems" which is why he doesn't need to add any to do it.

You'll be better off with VS ,but not with that guy.

Even it it could overcome undersized ducts,it increases the operating cost and likely shortens the life of the VS motor.

[troyorr]

Great, saw the words Ding-Dong and immediately started thinking about Chuck Berrys song My Ding-A-Ling. Now I can't get that damned song out of my head.

[energy_rater_La]

And I was wishing I had some hostess cream filled cupcakes.
gotta admit I kinda liked ding dongs in the title also!

VS is used a LOT as a fix all for under sized ductwork & over sized hvac systems.
It does undoubtalby provide more humidity control, savings and comfort.

keep shopping!
and best of luck.