Question on Gas Boilers

camiarrobino

Hello -

My question is whether or not it is possible / relatively common to direct vent a cast iron boiler (not the fancy new condensing / high efficiency type) outside, without a chimney. I know that historically, cast-iron boilers have been vented into chimneys, which I want to avoid

The reason I ask is because I am planning ahead trying to decide what kind of heating system I want when I build my eventual new construction home

I am wanting the older-school cast iron type boiler, because from the research I have done and the folks I have talked to, cast iron boilers tend to last much longer and require less maintenance (and cheaper maintenance) compared to these newer fancy high efficiency boilers. Fuel is cheap, service calls (and replacement cost) is not. I plan for this to basically be my forever home. If it was a flip then I would go with high efficiency.

I want to avoid having a chimney because they are such a weak spot for getting roof leaks - gives me anxiety just thinking about it. I've seen newer chimneys, and older ones that were just entirely repointed & capped, let water into the house during pounding rain. No chimney is the best chimney to me

Can anyone provide some thoughts? Thanks

Jamie Hall

Other than a comment that a well-constructed and maintained chimney and roof won't leak...

camiarrobino

Sure but you're missing my point. Perhaps I'm being irrational and treating the chimney like it's a bigger issue than it is, but the bottom line is that it's a common failure point. Well-constructed and maintained knob & tube wiring & fieldstone foundations & balloon framing aren't issues either but that's not the point - the point is, if there is a better alternative that eliminates a common failure point / potential issue without detracting in any way, then great. If the boiler that I would want does not need a chimney and will work the same in either scenario, then to me there is 0 point in having a chimney - could care less about the look of the house with / without one

Hot_water_fan

Take a look at some install manuals, like the US boiler series x-pv.

KC_Jones

First question on your worry about a chimney in new construction is this. Why are you planning a masonry chimney for an appliance that needs a metal flue? You stated repointing so that implies you are only considering masonry chimneys and not the metal chimney that would be used for a modern cast iron boiler.

The metal chimney you would need for a boiler would be sealed in basically the same manner as a plumbing penetration, are you concerned about those as well? Just trying to understand where you are coming from on this.

That said there are cast iron boilers that can be power vented. If you are worried about failure points you should be significantly more worried about that failure point than a metal chimney leaking.

Basically you want the simplicity of a cast iron boiler, but don't want one of the main things that makes it simple, the chimney.

camiarrobino

KC Jones you make good points, thanks. I had not thought about stainless steel chimneys but that does sound like a good option since, as you mentioned, they could get tied into the roof the same way that a vent stack would. And they would not be porous at all like a masonry chimney is, which is usually the culprit of their leakiness. I think either the stainless steel chimney or power vent is probably best bet.

ChrisJ

I'm just confused why this is in the oil heating section.

camiarrobino

ChrisJ sorry about that, I may have posted in wrong place by accident. Feel free to move if you're able to

hot_rod

This was one of my favorite side vent boilers. I think all the cast boiler manufacturers offer this venting option. They will have electronics, most all boilers do nowadays. You need to be careful where you vent sidewall, they can make a mess on siding, and some noise issues for you and a close neighbor

What type of system? A multi zoned system is a better match for a modulating boiler. Fixed output boilers drop in efficiency when short cycled on multi zoned systems. Look for the post on
How Efficient is my boiler, really

JUGHNE

I don't know about SS venting thru the roof, but the old school standard "B" vent has a pretty good track record. Galvanized outer pipe with aluminum inner liner is the standard.

"B" vent I installed 30-40 years ago is still in use.
Perhaps at the most the roof flashing might be changed with reroofing, but I think that seldoms happens.

The closer to the center of the house is better in that the minimum of pipe exiting the roof can be used.
This gives less exposure to the elements and can often hide the pipe behind the roof ridge.

Also can include the venting for the plain Jane WH if desired.

In any case you need to allow for combustion air for all the gas burning appliances.
Often simply a pipe thru outside wall into the boiler room will suffice.

Install instructions are pretty clear on this.

Mad Dog_2

Power-vented boilers every company makes them.  Or u could do an up the outside wall Steel chimney.  Mad Dog

Jamie Hall

As much to be contrarian as anything -- but how long do you expect a metal chimney to last? Never mind a power venter? There are three masonry chimneys in the main house I care for. They date from about 1800 to 1893. None leak... Another house I care for has only one, built in about 1740. It doesn't leak either...

camiarrobino

Jamie Hall - a little while back at a different property I got quote to have a SS liner put in a masonry chimney by a reputable company who offered a lifetime warranty. Perhaps I shouldn't just assume but I more or less assumed that the same principle would apply to a SS metal chimney, as it's basically just a liner but not enclosed in masonry. As for a power vent, if the boiler were placed next to exterior of home it would just be a few feet run of PVC no? you make valid points

KC_Jones

camiarrobino said:

Jamie Hall - a little while back at a different property I got quote to have a SS liner put in a masonry chimney by a reputable company who offered a lifetime warranty. Perhaps I shouldn't just assume but I more or less assumed that the same principle would apply to a SS metal chimney, as it's basically just a liner but not enclosed in masonry. As for a power vent, if the boiler were placed next to exterior of home it would just be a few feet run of PVC no? you make valid points

Incorrect.

If you want a cast iron power vent that is a metal pipe because the combustion gases will be hot. Plastic vents are for high efficiency ModCon boilers that run at relatively low temperatures.

TonKa

I have had a power vented Weil Mclain w/o a chimney in a property for about 30 years now. I've had to replace its igniter twice,  its electronic module once (due to a recall), the circulator pump, a couple of Honeywell zone valve motors, and  the Amtrol indirect water heater. However, the power vent motor and gas valve are original. The sidewall vent frequently throws out an impressive plume of water vapor in the winter.

While it is true a power vent does add complication and another moving part, they work.

BTW, a direct vent draws its combustion air from the outside. A cast iron boiler which does not need a chimney is usually power vented and will draw combustion air from the room. It also almost certainly cannot use PVC for its exhaust.

JUGHNE

You need to do some homework on boilers....so far it is free.

Look at the boiler that Hot Rod posted above with his comments.

PVC venting is for the fancy Modulating Condensing boilers, low temp exhaust that is acidic producing and would eat up most metal piping.

Cast iron boilers have a higher exhaust temp that cannot use any PVC type venting.
They rely upon that high temp to utilize gravity exhausting up and away thru metal pipe of some type.
(Free as in requiring no power venting with it's certain eventual failure and no electricity for operation)

Jamie has a point about his masonry chimneys in that they are "forever" if kept dry and have a lot of heat headed up thru them.

The standard "B" vent will certainly last thru the "expected life" of a modern house.....by that I mean because they will get remodeled, almost gutted, every 40 years and the pipe can be replaced if needed.

mattmia2

I'm sure there are 15 comments here gettign to:
1. A good modcon will be more reliable than a CI boiler with an add on power venter. That is largely the part that is unreliable in both instances. The HX in a modcon can last a long time if you choose wisely and it is installed well.
2. A well built chimney isn't a source of leaks, if a good mason and roofer are involved it can be made to only require attention every few decades.

Mad Dog_2

I PREFER Old School Brick &. Mortar, but the man is against it.  He's not all wrong. My 123 yr old chimney has some weeping around the flashing and brick in to the attic.  The roof was ripped and all new plywood, flashing weather watch....copper flashings. The other problem 23 yrs ago (forget now) was finding any capable and willing masons to even do a brick chimney. "..nah..I only do flat work (pavers ground work)...aint done a chimney in yrs.. I gotta do some research "
It took me 10 "brick & masonry companies to find one who was willing and able to do one.  Nothing wrong w Powerventers especially with a SS system.   Mad dog

JimP

I’m not sure if I understand all this discussion but I think that you want a conventional cast iron boiler that can vent through a sidewall rather than chimney. If so this is an excellent boiler (it may be a similar boiler to the post from hot rod).

https://www.supplyhouse.com/Weil-McLain-381-359-006-CGI-5-88000-BTU-Output-Cast-Iron-Boiler-Spark-Ignition-Series-4-Nat-Gas

They come in a range of sizes and I find them to be excellent equipment. Be mindful of where you locate it the boiler. Study and plan based on the manufacturer specs. Get as close to the outside wall as possible because the vent hardware is very expensive. They also make noise on inside and outside that you don’t have with a conventional boiler and chimney.

Mad Dog_2

Yes  Jim  that's what he wants

yellowdog

what are you going to have for a heating system? radiant, baseboard, panels rads? the way the future looks, i would definitely design the house with a low temp heating system that could easily be converted over to an a2whp or an electric boiler in the future. this would lead to me to putting in nothing but a mod-con.

rick in Alaska

My first question is if this is a gas or an oil boiler? That will tell you what type of metal chimney you would need, if you go that way. To me, a metal chimney would be the cheapest low maintenance way to go. If you go with a power venter, then you have issues with them going out over time, the electrical consumption, and the extreme noise they make, especially after they get older.
Also, as others have said, a sidewall vent is at ground level, or so, and they are noisy if they are in an area that you hang out in.
I am not sure about any current boilers, but Ultimate had a boiler that could be direct vented without a power venter. You just had to use special sealed piping, and make sure all your joints were well sealed when you did any maintenance. They were very efficient though.
Rick

ChrisJ

Mad Dog_2 said:

I PREFER Old School Brick &. Mortar, but the man is against it.  He's not all wrong. My 123 yr old chimney has some weeping around the flashing and brick in to the attic.  The roof was ripped and all new plywood, flashing weather watch....copper flashings. The other problem 23 yrs ago (forget now) was finding any capable and willing masons to even do a brick chimney. "..nah..I only do flat work (pavers ground work)...aint done a chimney in yrs.. I gotta do some research "
It took me 10 "brick & masonry companies to find one who was willing and able to do one.  Nothing wrong w Powerventers especially with a SS system.   Mad dog

GET OUT there's no way any of us would believe you prefer old school anything..........