Venting Question

masterplumb

Does anyone know if there is a maximum distance to tie flu piping from a boiler or water heater to the chimney? I was originally going to use a direct vent kit through the side-wall but I cant find a "safe" spot to pop through where there isn't any windows, doors, etc.

What is the rule on piping size, do I have to increase the size of the piping farther down on the run? We're talking about 25' or so to the chimney. It'll take about 5 90* turns to get me into the chimney. The boilers flu is 5", will I have to increase this as the run goes on?

Thanks in advance. Chris

S Ebels

Best source of info

On a problem like this is always the manufacturer. They will have a max length and each ell usually counts as 5' of straight run. Sounds like you may be on the edge.
I've never heard of increasing the vent pipe size on longer runs, it would just slow down and cool of the exhaust more than the recommended diameter pipe.

One suggestion......... If you have a vent connector that long you may want to inquire about using stainless. I have a feeling that there will be condensation issues in a connector that length. You'll want to check your exhaust temp carefully to make sure you aren't getting into trouble with low temps.

masterplumb

I was planning on using double wall b vent because it will be boxed in. I was also concerned about condensation and also draft. I guess I should have stated it's a gas boiler. Thanks again. Chris

DaveGateway

Direct vent kits

usually are limited to 15 feet. Sounds like you just as well go back to putting the boiler back and use the chimney.

DaveGateway

Even a condensing gas boiler

with PVC piping could pipe up through an unused chimney, but you'll probably hit the max length of the pipe limits with all that distance and elbows. Check the manufacturer specs. Any reason the boiler can't go back where the old one was?

masterplumb

The homeowner is finishing the basement and making a smaller room the utility room. Chris

Unknown

Chris, how high is the

chimney? Is it lined? Is this a conventional boiler and water heater? Are you connecting the boiler and water heater together into a common vent connector? What is your connector rise? What is the flue size of the water heater? What are the BTU inputs? Is the boiler a category I flue? Is it fan assisted? Is the chimney inside the building or is it exposed? With a 5" flue connector the maximum lateral allowed is 7 1/2 feet. So if you have 25 foot run you will have to reduce capacity 10% for every 7 1/2 feet so your reduction would be roughly 25% and that is assuming that this is a conventional non fan assisted boiler.

To give you a possible solution I need this info. Off hand however with 5 90 degree bends and the distance involved you will need to increase the connector size. Double wall will probably have to be run all the way as single wall for that long a run will not work.

masterplumb

Timmy

The chimney is lined with clay(masonary). It is a Crown boiler cwi103 hot water boiler(gas), 103000 btu. It is standing pilot, no vent damper. The boiler makes hot water. This boiler comes as gravity draft(?). It has an option to be direct vented outside. I planned on running double wall, because it will be boxed in. Thank you. Chris

Unknown

Just need chimney

height and I will give you a solution or at least whether you can do this or not.

Just looking at the Table 13.3 in NFPA 54 you are probably going to have to run 6" or 7" all the way double wall. I can give a more accurate figure with chimney height known.

masterplumb

Chimney

Do you mean where i will pop into the chimney or the height of the clay chimney?

Unknown

How high is the

chimney? Is it 20 feet or 15 feet from the bottom to the top. I think you need some training on venting based on the information you are having trouble getting out.

In order to size a vent connector to a masonry chimney you have to know the HEIGHT of the chimney and the LATERAL run,then the BTU input of the equipment. With all that I can go into the table 13.3 and give you a double wall connector size which also will have to apply the rule for lateral runs from Table 13.2.2 Vent Connector Maximum Length for your 5" Flue size the maximum run you can have is 7 1/2 feet you then reduce the capacity 10% for every multiple of 7 1/2 which in your case you said your lateral run was 25 feet with 5 90 degree elbows. So you will have to reduce capacity 25%. Then an additional reduction of 10% for any number of 90 degrees over two so that is another 20%. So the overall capacity will be reduced by 45%. Once I have the chimney height I will give you the connector size you need.

masterplumb

I agree...

I do need more training on venting. Ok, try and bear with me as I really appreciate you helping me with this. I will try to get an exact measurement when I go back thursday, but if memory serves me right the clean out for the chimney is about 3 feet off the basement floor, its 2 stories plus an attic and the chimney extends about four feet above the roof so I will say 30 feet. But I will get an exact. Once again I appreciate your kindness. Chris

Unknown

Chris if the

chimney is 30 feet high with all of the other information you have given me you need a 7" double wall connector. Even with that it may still be a problem with condensing. It is a long run with a lot of 90's.