Can I vent Combi Boiler through chimney with PVC?

[frodo]

this reminds me of my favorite episode of the Andy Griffith show, call your manufacture

 

[breplum]

Sounds like you could potentially remove the chimney, then use the framed chase. Start at the top and get rid of it.
Then make a simple run.
We do this sometimes but usually to get more room in the house. This assumes the flue is obsolete and abandoned.
Here in CA it is a seismic liability anyway, so there is a benefit to the effort and cost.

 

[mdk0420]

Vent according to local authorities & unit manual specs. No Shortcuts (void warranty&call manufacturer)after all your nice work, sounds like u may have no choice but a chimney liner....

Some of the advice I'm getting say that a chimney liner may not be an option, and probably not even a double wall vent.

That boiler creates condensation in the flue gas you cannot use any metal venting and you cannot have it venting to a lined chimney it needs to be PVC all the way to the exterior of the house pitchedback towards the unit plain and simple done and done

The manual says that I can use all the common materials for venting, even corrugated aluminum, galvanized steel, and "other materials" so it must be a broader list. Just trying to understand why I can't use other material besides PVC since condensation builds up on aluminum (At least it sure does on my AC system, but on the outside instead) and I'm sure any other material that would transfer the heat/coldness. Wouldn't it fall down into the boiler in all of these cases except for lining the chimney to create that high efficiency from condensating?

this reminds me of my favorite episode of the Andy Griffith show, call your manufacture

I'm going to this week. Just finishing up the gas line today so my next project is the venting... so I definitely want to figure it out asap. I'm getting a whole lot of conflicting answers. Maybe you can chime in on the reason for not being able to use any other material besides pvc? From what I saw throughout the forums you know your stuff.

Sounds like you could potentially remove the chimney, then use the framed chase. Start at the top and get rid of it.
Then make a simple run.
We do this sometimes but usually to get more room in the house. This assumes the flue is obsolete and abandoned.
Here in CA it is a seismic liability anyway, so there is a benefit to the effort and cost.

It's a rental property. It is very unlikely to ever be used again. The only thing I can think of that might be possible for usage would be a small wall hung gas heater, but that would have more options of placement and probably be much closer to rear of the home where it can easily vent out. And farther options would end up just being an electric heater so it wouldn't need to vent. But that would probably take a huge amount of work to remove a chimney and I just couldn't justify the cost, time and effort to remove the whole thing.

 

[breplum]

"The manual says that I can use all the common materials for venting"
What manual are you referring to? The Installation manual says, on P33, ONLY use (in USA):
PVC Sch 40 solid core
CPVC SCH 40 or 80
Approved Polypropylene

THERE IS NOTHING SAYING YOU CAN USE ALL THE COMMON MATERIALS.

Also read the" Measuring Vent Length" details about distance and elbows. Two 45 deg. elbows equals 3 linear ft of vent. 90 deg elbow equals 5 ft of vent. using 3"
I suggest you reread the installation instructions and have a licensed pro help you.

The Navien Warranty is "void" in the event of being "installed by a non-licensed installer." and or purchased from a supplier or distributor not authorized by Navien (which includes all e-commerce channels).

 

[mdk0420]

"The manual says that I can use all the common materials for venting"
What manual are you referring to? The Installation manual says, on P33, ONLY use (in USA):
PVC Sch 40 solid core
CPVC SCH 40 or 80
Approved Polypropylene

THERE IS NOTHING SAYING YOU CAN USE ALL THE COMMON MATERIALS.

Also read the" Measuring Vent Length" details about distance and elbows. Two 45 deg. elbows equals 3 linear ft of vent. 90 deg elbow equals 5 ft of vent. using 3"
I suggest you reread the installation instructions and have a licensed pro help you.

The Navien Warranty is "void" in the event of being "installed by a non-licensed installer." and or purchased from a supplier or distributor not authorized by Navien (which includes all e-commerce channels).

My manual has that on page 44. I was looking at page 40 where it says that I can use "ABS, PVC, CPVC, PP, Galvanized Steel, corrugated aluminum, or any other such materials" but just noticed that is for intake. Page 44 does recommend PVC/CPVC. But does not require it. It just has to be in accordance to the local laws and ANSI Z223.1 NFPA 54. No clue what that list describes though. I'm sure things like stainless steel would be fine to use. Which brings me back to the question of what exactly is wrong with using something like double wall venting. Does it just condensate less or something? It has the same flue gases going through it at the same temperature.. When it is cooler outside then in the flue, wouldn't it still remove the moisture out of the gases. I'm getting conflicting answers saying to do it, some saying they don't recommend it and others saying I can't with a condensing unit. Explain please.

I'm familiar with the distance I can go. With 3" PVC I have a total of 150 FT I can use. The longest distance I would run is around 55 ft. Even with a max of 8 elbows (the most I can legally have) I would still be under 100 ft total of my allowance.

My biggest problem there is that according to the manual I would not be able to clear the 8 elbow maximum. I'll have to call Navien on that one but I need a total of seven 90 degree elbows just to get it pointing in the direction I need it to go. But then I need to offset it which would require two 45 degree elbows. That is 9 elbows all together. There is not enough clearance to turn the last 90 degree elbow upwards to do the offset that I would want. The only other option would be to go straight at it but then it will have to go through concrete. The concentric systems also adds an additional 5 ft of venting. Before I even consider that I need to find out what the snow level in PA is (Tried searching it and couldn't find it). I plan on calling my township to get an idea of that. I'm at around 24" above the ground where I originally planned on exiting at.

The boiler is already pretty much installed except for the venting part. I understand that the warranty is voided because I installed it. Doesn't bother me much since I saved about the cost of a whole new boiler anyways (That was the lowest bid I got of 6k, most others were upwards of 10k). Was a great learning experience. I have no plans on hiring anyone for any of the work. I enjoy learning new things and to me, it is not worth hiring someone for something I can do myself just as well. Just takes more take for me because I have to do my own research. Nothing wrong with that and I'm sure once it is all done it'll be done as professionally as anyone else.

 

[Drew]

The bottom line is, if a 90% unit states PVC ,shortest distance, least elbows,and 12in. above min. Snowfall level with and 1/4 pitch per feet back towards the unit to drain condensation, all other sceneries, flue is most important, windy day, weather etc.
Your asking for problems....
I’ve installed many.....
80% furnaces were installed with chimney Liners or B vent do to sulfuric acid from combustibles in brick.
I’ve put put these units in closet, laundry rm, pantry. Wherever works best, u need minimal clearances.

 

[mdk0420]

The bottom line is, if a 90% unit states PVC ,shortest distance, least elbows,and 12in. above min. Snowfall level with and 1/4 pitch per feet back towards the unit to drain condensation, all other sceneries, flue is most important, windy day, weather etc.
Your asking for problems....
I’ve installed many.....
80% furnaces were installed with chimney Liners or B vent do to sulfuric acid from combustibles in brick.
I’ve put put these units in closet, laundry rm, pantry. Wherever works best, u need minimal clearances.

The most convenient setup would be to run it through the chimney is why I'm adamant about it. It would still run back into the unit which is why I'm so confused about it but maybe it has to do with It would take only several elbows and its probably about a 25 foot run. It allows for roof vents, but there is just the legality issue of putting it through the chimney with PVC. The alternatives require it to run somewhere between 44ft and 55ft. I would like to run the 44ft distance but that requires that 9th elbow, but I need to call Navien and ask them about that one since it would be using two 45's for the offset. At the exit I'm within all of my clearances except for maybe the anticipated snow level. I need to ask the township what their requirements are for that. PA doesn't get a whole lot of major snow fall. So far I've only been able to find other states with "10 year average" and such. I'm sure the township will have more insight on that. I do own another home that has a furnace/AC unit that vents out only about 18" off the ground, if that, in the same township. Not 100% sure if it was professionally installed but they work well and are about 10-15 years old.

I did position the boiler to make the run. I dropped it 14" from the joist to make the longest 55' run, but i rather do the 44' run since it is more practical and it allows for the concentric venting (It runs with the joists since it exits to the side rather then rear). That easily gives me the 1/4" per foot drop that I need. I wish I could do it with less elbows but there is no way. No matter what way I run it, it'll be about maxed out with elbows.

 

[Drew]

2-45’s fittings equal to 1-90 minus 3-5 ft according to installations docs & termination according to mechanical code year your municipality uses (12”,18”, 24” 36” where ever your terminating near window, or above grade, be aware of snow drift, sometimes u have to check,
Stay 3 ft away from inside corner,
Because of back pressure

 

[Drew]

GOOD LUCK

 

[mdk0420]

2-45’s fittings equal to 1-90 minus 3-5 ft according to installations docs & termination according to mechanical code year your municipality uses (12”,18”, 24” 36” where ever your terminating near window, or above grade, be aware of snow drift, sometimes u have to check,
Stay 3 ft away from inside corner,
Because of back pressure

Thanks for the advice! I'm really hoping that's the case with the fittings. I'll still confirm with Navien just because their wording is a little weird (Doesn't specify the type of elbow, just that 8 elbows are allowed). Won't be in any corners. I'm actually putting it along the utility side of the home. There are 2 electric meters and 2 gas meters there. But I already checked with the township and I meet the minimum clearance from everything. Is it a good idea to cover the intake/exhaust so rain water doesn't come back into it? I've seen a lot of venting without any covers besides the screen. Some come straight out of the wall, others come up but then elbow back out (probably to clear the 12" distance from each other). All seem like if it rains to the side even a little bit, some water would get in. I've always wondered if that would be an issue

 

[mdk0420]

Confirmed it with Navien and the 7 90's and 2 45's are acceptable with the concentric venting. Now I just need to make sure it is high enough off the ground once the township returns my call

 

[mdk0420]

Scratch that. I called back to get an email that the 2 45's would be OK and a different tech said that is not OK and won't work. I asked him about using flexible PVC and he said each time it bends also counts as an elbow. So even if I offset it by a couple of inches over about 5-6ft it would still be considered 2 bends (One to go up and one to straighten it back out). Not sure if the inspector would OK it or not. Running out of options on how to run the vent line...

 

[TomFOhio]

You got a lot of ideas on how to do this vent. I think at this point I would call the person that is going to inspect this and have
him come to your house and tell you exactly how he wants it done. Do it that way. Have him come back and inspect it, put the inspection
sticker with his name on the boiler and be done with it. You're ready for the winter.

 

[frodo]

I have already said it,
you always run the vent then set the equipment 2 the vent
because of space restrictions and the bend rstrictions

start from the roof top with the vent, and install the vent
after you have installed the vent , move your boiler to match the vent

 

[mdk0420]

I have already said it,
you always run the vent then set the equipment 2 the vent
because of space restrictions and the bend rstrictions

start from the roof top with the vent, and install the vent
after you have installed the vent , move your boiler to match the vent

Moving the boiler isn't an option I'm willing to do. I did contemplate it at one point but it wouldn't work the way I wanted it to work and would be more inconvenient if I did it that way then the way I'm doing it now.

You got a lot of ideas on how to do this vent. I think at this point I would call the person that is going to inspect this and have
him come to your house and tell you exactly how he wants it done. Do it that way. Have him come back and inspect it, put the inspection
sticker with his name on the boiler and be done with it. You're ready for the winter.

I called them and I think we figured it out. Although flexible PVC isn't allowed because of having only a 130 degree working temp, I can heat bend regular PVC to make the curve. He is going to give me the OK tomorrow if it'll work but he doesn't see why not if the radius of the curve isn't enough to be an "Elbow"

 

[mdk0420]

Lucky me, the inspector said that he is going to OK the 9 elbows because their manual says 8 elbows (With max of 90 degrees) and will consider the two 45'2 as one 90 so I can make the pass I need to make.