You can't vent all of that crap together!
What's wrong with this flue system and how would you remedy it?
11 yr old 2 story home zoned up and down. 2nd floor is 1/2 the size of first floor.
2 Carrier 80% 80,000 btu furnaces with 4" flues
2 40,000 btu water heaters with 3" flues
All flues single wall into single wall 8" which goes into 8" vertical double wall with 30' rise
Flue system all original except for 6 mo old 3" water heater flues which were replaced when orig. water heaters were replaced 6 mo ago.
(Single wall 8" continues about 3' to the right out of picture range before tieing into 8" double wall riser)
2 yrs ago large amounts of rust began falling out of furnace flues onto top of furnaces and you can hear dancing rust when inducer motors start.
Showing signs of acidic condensation & flue connections starting to rot.
[Edited by midhvac on 03-04-2004 at 02:47 PM]
You can't vent all of that crap together!
I think I would just start over completely that is dangerous I don't see how that could ever work.
Theres nothing wrong with 4 appliances hooked to a common vent. The first problem is the size: 30' of 8" double wall will handle around 470,000btu. The second problem is the way they are hooked together: The furnaces should be the last thing entering.
As for an actual rememdy, I couldnt give an actual answer without seeing the job firsthand. However if this would have been my job from the start, I would have done a better job of either placing the stack, or the appliances. Also I would have sized the stack properly instead of just guessing. From the info you have given I would have installed a 6". And last but not least, I would have used double wall connectors instead of single wall.
I've inherited the job of fixing it and am not relishing it. You're right, the placement is a major problem and all of the single wall has to go.Originally posted by ls-1_eater
Theres nothing wrong with 4 appliances hooked to a common vent. The first problem is the size: 30' of 8" double wall will handle around 470,000btu. The second problem is the way they are hooked together: The furnaces should be the last thing entering.
As for an actual rememdy, I couldnt give an actual answer without seeing the job firsthand. However if this would have been my job from the start, I would have done a better job of either placing the stack, or the appliances. Also I would have sized the stack properly instead of just guessing. From the info you have given I would have installed a 6". And last but not least, I would have used double wall connectors instead of single wall.
I don't think a good load calc was done as the 2nd floor is 1/2 the size of the first floor and both have 80,000 btu furnaces and 3 ton a/c units. First floor furnace never runs very long and 2nd floor furnace hardly ever runs. I also don't think they need 2 50 gal water heaters.
1st floor unit is on the left in the photo. When only it is running you can hold your hand on the 8" single wall flue just to the left of where the right furnace tees in and it's not even uncomfortable. A foot to the right of there just after the right furnace tees in is much cooler still, just barely warm at all. Every time I've been there I've never see more than one of the 4 appliances on at one time. I can't even imagine what happens when only 1 water heater is on and no furnaces.
You should see the closeup photos. All 3 connections to the 8" single wall are home made. They just snipped tabs into the smaller ones and folded them over. One of the tabs was eaten by acidic condensation and fell off in my hand when I touched it.Originally posted by pmccune
I think I would just start over completely that is dangerous I don't see how that could ever work.
It drafts real good though!
And here I thought I was the only one who ended up with jobs like this. Good luck. I'm sure you will come up with something better than what they have now.
I see your point. With only one ot two appliances coming on at a time the gases will surely cool off too quickly and condense water in the flue. You almost need to run some seperate flues. At least the two WH together and the two furnaces together all in B-Vent.
I bet if you put a drain in the 8 inch just as it turned up for the 30' rise you would collect some water!
I know. This is one of those situations where something can be done according to venting tables and still produce tons of acidic condensation. I too thought about separating the wh and furnace flue systems and tieing them in closer to the 8" riser but there's still going to be lots of moisture.Originally posted by PaysonHVAC
I see your point. With only one ot two appliances coming on at a time the gases will surely cool off too quickly and condense water in the flue. You almost need to run some seperate flues. At least the two WH together and the two furnaces together all in B-Vent.
I bet if you put a drain in the 8 inch just as it turned up for the 30' rise you would collect some water!
Sometimes I think codes should require more than one flue out the roof for x number of appliances.
If you follw the 7 imes rule your waterheaters are a problem 8" is to big the waterheaters flue connections are only 3" flue connenctor correct they should be 4" I would sell them a bigger water heater.
Tell customer that they need to suffice with one water heater...or relocate one...that takes care of the sizing issue.
The 2 50 gal water heaters are 6 months old and were replacements for the 2 original 40 gal ones. HO wanted bigger ones. The new ones were put in 6 months ago by my plumber buddy who is the one who referred me to the ho.Originally posted by trgams
Tell customer that they need to suffice with one water heater...or relocate one...that takes care of the sizing issue.
There's no room anywhere nearer to the 8" run going up through the house for a water heater.
Everything drafts okay now. I know the single wall stuff has to go, but I'm just trying to figure out what configuration of 4 B vents would minimize the acidic condensation and cold flue problem and still allow everything to draft well. I'm supposed to give them a price on redoing it.
Any suggestions on the best way to hook these 4 things together with b vent?
Was this put in by a NATE installer ?
No. It was done by a LAME oneOriginally posted by kb0vso
Was this put in by a NATE installer ?
After poring over this thing, it appears that the 8" common flue was in fact necessary because of the number of offsets in the common flue *BECAUSE* as it oftens happens, the builder's floor plan was so chopped up, there was nowhere else to locate the gas appliances, so the common flue had to change direction a few times in order to come out the roof where it wouldn't be seen from the street.
All I can do (for less than *thousands* of dollars) is to replace the single wall with B vent. There's still going to be lots of acidic condensation though.
What a mess
I don't think (even with B-vent) you will ever get this mess to work. The B-vent will quickly corrode and I doubt the equpment will vent properly anyway.
Your lialbility is huge - I'd recommend to the customer they replace everything with sidewall vent equipment or heat pumps and electic H2O tanks (if that is even possible), if not, I would "run away".
JMHO
I know. If I mess with it, it becomes my problem. Under the circumstances, the contractor should've gone with 90%ers when it was built, but the builder's probably didn't want to pay the extra $$$. The current owners bought the house when it was 3 years old.Originally posted by Rudy
I don't think (even with B-vent) you will ever get this mess to work. The B-vent will quickly corrode and I doubt the equpment will vent properly anyway.
Your lialbility is huge - I'd recommend to the customer they replace everything with sidewall vent equipment or heat pumps and electic H2O tanks (if that is even possible), if not, I would "run away".
JMHO
It gets worse. A few years ago, the current owners spent 25,000 to have the basement finished and the ductwork (now inaccessible) done. The basement's still freezing and he wants more heat down there. The original hvac contractors installed 2 80,000 btu furnaces, (one for 1st floor & one for the 2nd floor) even though the 2nd floor is less than 1/2 the size of the 1st floor. The finished basement ductwork comes off the 1st floor unit so it's pretty well tapped out. The bldg inspectors busted the remodeling contractors who did the basement and made them put in much more combustion air into the furnace room, much of which comes from an uninsulated cold space on the outer wall from the finished area floor up over the top of the ceiling to the furnace room. 50 degree air comes out of vents in the finished area near the floor in the winter.
It would be a hell of a lot colder down there if it wasn't for the heat from those single wall flues too. Furnace room is nice and toasty.
New 90% furnaces with outside combustion air would eliminate the need for the cold combustion air inlets.
It's a $#@$ mess!!!!
"Run Away"
Yep, I can't tell you how many times I tried to do things that weren't quite right just to try and help customers out. More often than not it came back to bite me in the bu**.
Fortunately, I don't think I ever hurt anybody but ya just can't take that chance.
If they don't want to do it right, don't do anything at all.
You sure don't want to see a post in a couple of years in the "Wall of Shame" from some other contractor showing pics of your B-vent all falling apart (and it certainly will)!!
Plus, he'll be the one making the big bucks on replacements and your reputation will take a hit....
I guess you guys are right. This guy isn't going to shell out the money for new furnaces, and the water heaters are only 6 months old too. There are so many problems here it's unbelievable. To make things worse, there's a steel support beam all the way across above the finished basement ceiling that's in the way of running the pvc for new 90% furnaces. Some sort of pipe chase would have to be built.Originally posted by Rudy
"Run Away"
Yep, I can't tell you how many times I tried to do things that weren't quite right just to try and help customers out. More often than not it came back to bite me in the bu**.
Fortunately, I don't think I ever hurt anybody but ya just can't take that chance.
If they don't want to do it right, don't do anything at all.
You sure don't want to see a post in a couple of years in the "Wall of Shame" from some other contractor showing pics of your B-vent all falling apart (and it certainly will)!!
Plus, he'll be the one making the big bucks on replacements and your reputation will take a hit....
I think I'm going to suggest he should move (and take all of my stickers off the equipment)
Absolutely, get your stickers off the equipment!!
Then explain what you have found and give an estimate to fix it.
They'll probably find someone else who will just revent it, then in a couple of years, they'll be calling you back.