how can i fix an ice buildup on my roof from new furnace exhaust

Techman

How close to the roof was the top of the exhaust? how close is it now? Give both height and horizontal measurements!

deb_5

furnace exhaust causing ice buildup on roof.

We installed a new rheem 80% 2 stage furnace airconditioner and whole house humidifier this summer.
In the cold weather there has been an ice buildup on the roof from the condensed exhaust. My contractor came and lowered the stack but it is still happening. He is stumped and I am wondering if this has happened to any one else and what the solution can be. thanks deb

jp_2

got a picture?

can you post a picture of the problem?

Edward A. (Ed) Carey_3

Lowered????

He lowered the stack???

Am I missing something here?



Ed Carey

deb_5

our vent stack had been raised earlier because the wind would blow out the old pilot light. the theory was that because the stack was about 4 feet above the roof water was condensing in the exhaust and as it hit the exhaust cap it drops down and forms a cone like shaped ice stagalmite next to the stack so the contractor lowered the stack to about 2-1/2 feet where the original vent stack had left off. he put new flashing around the stack and thought that had it fixed. but a new cold snap came and the problem is back. the ice is as high as the exhaust cap. and kind of sitting next to it. it isnt restricting any openings but i worry about melting. it melted and came through the attic and made water spots on the ceiling. but I think the flashing might have fixed that. i will try and get a picture of it and maybe that will help in describing it. thanks deb

Techman

deb

Did they single wall vent pipe?

deb_5

venting

i talked to my contractor this morning and he said that we either had to go into the attic and put a insulating wrap around the pipe or cut the vent stack even shorter.
they used the existing vent work when they installed the furnace. does either of these solutions sound realistic. i think he is trying to just stall me out thinking it will soon thaw out. thanks again for trying to help me. deb

jp_2

pictures sure would help here

we need to 'see' whats going on here to give you the best help we can. not all vents are the same.

what was the 'existing' vent?

Edward A. (Ed) Carey_3

Photos and furance Model Number

When you said that he used the existing pipe when he installed a new furnace, concerns me.

Sounds like the old,,,, "It can't be wrong because we always do it that way".

You may have a new furnace that is not compatible with the old vent pipe.

A few photos of the vent pipe and of the furnace, and also the model number of the of the furnace would help.


Ed Carey

Ed_26

ice

What size is the vent pipe (chimney)? Perhaps your installer should have installed a liner inside the old vent. Most new 80% units require a 4" vent system. too large a vent will cool the flue gasses & cause condesation.

deb_5

funace pic

okay the pictures arent the best but i dont have a ladder to get closer. my furnace model number is RCBA 4882GG21XI.
my husband says he thinks it looks like 4" pipe. thanks deb

deb_5

okay i have a couple of pics now and the model no of my furnace. rheem RCBA 4882GG21XI. my husband says he thinks the pipe is four inches as well.

deb_5

im sorry i gave the wrong number the furnace is RGPK-10EBRJR

Eric_25

raise the pipe

The stack needs to be a minimum of two feet above the peak on the higher roof to work properly and to meet code. It looks like you have a draft problem that should be checked out, CO checked etc.
Where is the furnace located?

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deb_5

the furnace is in a crawl space under the main floor of the house. it is a horizontal furnace... the strangest thing is we just took off two feet of stack... and now he is telling me no that because it is not a drafted vent

deb_5

it is power vented 80% furnace

Eric_25

draft induced

unless you have a seperate power venter this furnace is not "power vented" it is "draft induced" which means it has an inducer fan to overcome the pressure loss in the heat exchanger but is not powerfull enough to power vent the furnace. I suspect that the chimney is not drafting properly due to the fact it is not tall enough and may or may not be oversized (can't tell from info onhand. This condition may be made worse if the unit is running on low speed which slows the inducer fan down further.
You need to get this checked out properly, you could be spilling CO into the crawl space.

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GW

Deb, you gotta play ball with us, please post a pic of the furnace area; you may have a bigger problem than an ice cube outside

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jim lockard

Question

Deb the wall chase where the furnace flue runs thru your home is it damp? wallpaper or paint peeling? is there a smell in your home when the furnace runs? I suspect that you may have a damaged flue pipe in your home. If so your going to need it looked at now. Have a pro check that pipe and the furnace top to bottom. Best Wishes J.Lockard

deb_5

more pitures

pictures of the crawl space and the flue connections.
contractor says pipe is 3" to 6". he suggests comming back in and running 4" through 6"run, capping off the 6" on the roof and then running another foot above cap with 4" how does this sound to everyone? there isnt any wet or condensate any where i could see.

Unknown

This unit, according to the manufacture...

As said earlier, your stack is too large of a diameter if this is the only appliance being vented into it.

According to the manufacture your unit should be vented using 4" vent, 5" MAX. It looks in the pictures to be 8"

I have attached a page from the installation manual for your unit.

So Deb, what is the INSIDE diameter of your vent going through the roof?

Thanks,

Steve

j carta

4

> pictures of the crawl space and the flue

> connections. contractor says pipe is 3" to 6".

> he suggests comming back in and running 4"

> through 6"run, capping off the 6" on the roof and

> then running another foot above cap with 4" how

> does this sound to everyone? there isnt any wet

> or condensate any where i could see.

j carta

4

> pictures of the crawl space and the flue

> connections. contractor says pipe is 3" to 6".

> he suggests comming back in and running 4"

> through 6"run, capping off the 6" on the roof and

> then running another foot above cap with 4" how

> does this sound to everyone? there isnt any wet

> or condensate any where i could see.

j carta

vent

someone stated ealier in your thread that the venting should be reduced to the proper size--increasing from 3" to 6" is compounding your problem-when the exhaust gas enters the 6" from the 3" it expands /cools and the velocity is reduced possible causing the condensing of the exhaust

Empire_2

J Carta

I think that looks even bigger than 6" pipe. It's hard to tell. But, Yea as stated earlier, 2' above any roof line within 10' is code. Also, did anyone notice the B-Vent from the basement does not have the 1" clearance from combustibles as stated by the manufacturer and code book. Also is the HW tank connected to this main vent pipe? I would think so.....

Mike T.