Boiler Exhaust

HydroAir

Hi All!


I have a question for you that I'm hoping you can help me with.
We have a customer who is doing a full renovation in their home and the architect has decided to remove the chimneys that the boilers are connected to and have us install a power venter.
It is not possible for us to put the power venter directly outside the boiler room, however the architect was thinking too possibly bury the exhaust pipe underground and run it to a power venter that's remoteed about 15-20 ft away. I was thinking to use a b-vent and sleeve it in a polyvinyl coated duct underground.
Have you ever seen anything like this before or is it even possible? I was worried about it condensing or even water issues but wondering what your thoughts are on this?


Thanks for your help

STEVEusaPA

Sounds like a horrible idea. The architect should’ve researched this on his dime before he decided to take the best way to vent, and try to hack in a way that will give the customer problems long after he gets his final payment.

EBEBRATT-Ed

The chimney didn't look good so he took it down. That's what happens when you have a designer think like a mechanical engineer

unclejohn

No. And run away from that job.

Steamhead

unclejohn said:

No. And run away from that job.

This.

If the architect is that bad, there's no telling what else he'll try to get away with.

kcopp

Is this gas or Oil? If its a Oil set up is it possible to switch to gas and re route the vent up and out the roof?

BillyO

Geez, the thought of him even presenting that idea pisses me off

HydroAir

> @kcopp said:
> Is this gas or Oil? If its a Oil set up is it possible to switch to gas and re route the vent up and out the roof?

There are two gas boilers about 300,000 BTUs each. The architect wanted the homeowner to upgrade and convert to modulating condensing boilers, but the homeowner is over budget and trying to reuse the existing boilers and get another few years out of them.

motoguy128

Exhaust buried going below the boiler and then buried? How you going to drain it?The genius engineer knows it makes condensation sometimes especially if buried in the ground right?

Not sure I’d use b vent. It would still rust out. Almost rather accept condensation and use stainless and pitch it back toward the boiler with a drain tee in a sump pit with a condensate pump in there with water sensor.

Power vent mfgs should have a chart for maximum equivalent distances.

SuperTech

My personal opinion is that any oil fired equipment and non condensing gas equipment the best way to vent it is a chimney. I'm not a big fan of power vents. Just another thing that can break down when you need it.

Solid_Fuel_Man

Hmmmm....2x 300,000 btu/hr boilers. Must be one big leaky house!

I'd run away! Sounds like it's a hack job on the heating side just from that statement.

Jamie Hall

This is why engineers and architects get a bad name.

Bail out, @HydroAir .

Solid_Fuel_Man

Should be a requirement to work in the trades for so many years in order to become an engineer.

Jamie Hall

Solid_Fuel_Man said:

Should be a requirement to work in the trades for so many years in order to become an engineer.

Perhaps not in the trades, @Solid_Fuel_Man , but definitely boots on the ground. I completely agree. That's the way I came up, though, so perhaps I'm biased! Book learning (or nowadays, YouTube I suppose) is all very well, but there's no substitute for getting out there and getting your hands dirty and doing the job.

clammy

With boilers that size you will not find a off the shelf kit5hey usually stop at about 140 mbtu if memory serves. I think they should use there kitchen and bathroom renovation money for either a new chimney or mod con or buy some blankets and space heaters . Unless you make a custom power vent exhaust system and are married I would do as other suggest and run away seems like the architect is non reality based and might be clueless . Don’t waste to much time unless your getting paid to waste it Peace and good luck clammy

HydroAir

Sorry for the vague description but yes there are two boilers and roughly 300,000 BTUs each. It's a very large house roughly 16,000 ft²
The boiler exhaust will be going underground but not below the boilers. There's plenty of height and pitch but nowhere to mount the power vented exhaust to the side of the house as you conventionally would. The thought was to trench on the side of the house about 20 ft away to get the power venter away from the terrace.
I know it's not conventional and frowned upon but is there any code restrictions against it?

Jamie Hall

Off hand, I can't think of a code restriction against running the breeching that distance.

However.

I can imagine there might be, and honestly if there isn't there should be, if the idea is direct burial. Equally honestly, I would never have approved it when I was a building inspector, and I certainly would never put my professional stamp on it. If it is direct burial, you have absolutely no way of ensuring that there are no defects in the ductwork, and thus no way of ensuring that there isn't a leak, nor that water won't accumulate and block the ducting. You would have created an obvious and avoidable danger to health and safety, and if anything -- anything -- went wrong, you would own it, jointly and severally as the legal eagles say, with the architect and any engineers silly enough to stamp it.

If you really want to do this, there is one -- and only one -- way I would consider doing it: the ducting goes in a tunnel with standing room, adequate lighting, drainage, CO detectors, and drainage. Access (not just a manway, genuine access) at both ends. I'd have a preference for arranging natural ventilation at the far end, but I'd also provide for power ventilation.

clammy

Your hardest part will be enclosing the flue in some thing to prevent it from contact w soil . I think you will be using stainless steel vent pipe and enclose in concrete storm drain piping .a very costly proposition which when added up will likely be as costly as a mod con replacement . Have you thought of constructing a mechanical room outside the home and then shuttle a supply and return into the existing mech room may be cheaper being at 300 mbtu each that would most likely be some expensive stainless . One last thought is that w power venting 2 units the failure of the power venter means zero heat that will be a issue plus if using one power venter you will be pulling draft across a non firing boiler ? No .personally I would leave it on the architect to deal w he created the issue let him figure the correct way for it to be done but I can assure you running b vent is not possible if it’s oil your looking at triple wall all flue flue pipe and that cannot just be buried it would have to be encased .And don’t forget some combustion air make up will and is required if issues re to be avoided in the future . There s always seems to be room and money for everything else on mansions except boilers rooms, mech rooms ,air handlers ,condensing units and of course in your case chimneys for boilers now if it’s a fireplace different story . Funny thing is by removal of the chimney in a home that large do they really need the max of 4 sq ft of space .i think a lot of times the ho and architect are not based on reality at least for this planet and in 5he future you will be the one dealing w the issues and the pissed off ho ,the architects check would have cleared and it won’t be his issue never is .one word of advise even if he is a ME do the research before you listen to them because when all said and done you will be the one they bring to court for damages not the architect . In the past I’ve had people want me to do stupid crap like that I just walk no sense in doing something the stupid to cover another act of stupidity and usually cheapness ? Even if you get in writing I would chk w local building department before you leap generally I would walk instead of wasting time on a project that sounds like no over thought was given unless they are paying for all of my time and not wasting a second of it remember for free you can work any where you please . Peace and good luck clammy

clammy

Final note in a home that’s 16000 sq ft there kitchen usually cost is more then replacing w mod con . Don’t fall for the not in the budget bs . In a home that large that better have the money other wise they just trying to keep up w the neighbors . Last note I shy away from mansions and renovation they tend to want to spend the least of hvac in my experiences cause nobody see it lol peace and Good luck clammy

Solid_Fuel_Man

Crazy at 16,000 square feet and cant afford to replace the boiler(s). Mod/cons are pretty cheap in the 150,000 btu/hr range. Stage 3 or 4 of them.

Zman

I don't believe you can bury the exhaust without some sort of access.The discharge must be above the snow level.
Anyone remodeling a 16,000 ft home has the money to do it right. They just need to be convinced that they should do it right.

Money is a universal persuader.

• The cost of the hodgepodge solution the architect is proposing may rival the cost of upgrading the boiler plant.
  
• The new plant will be more efficient and save them money.
  
• It is more expensive in the long run to band aid now only to spend more money later on the correct solution.
  

Comfort and Appearance works well, especially with the wealthy.

• The band aid fit will be noisy and smoky, they are entertaining guests in this area, yes?
  
• To do this the right way down the road, the home will be torn up again, yet another mess....
  

I would suggest creating an excuse to talk with the owners without the architectural idiot and mention the pros and cons(maybe you need to stop by and verify a couple details before you can price it). My guess is that the Guy is more responsive to money and the Lady is concerned about comfort. You need to play that one by ear.

Steamhead

Are these hot-water or steam boilers?

HydroAir

These are hot water boilers not that old and in pretty good condition.
I appreciate all of the replies and get the general consensus.
I'll try to convince the homeowner that replacing the boilers now is the preferred way to proceed. He does want to do it, but was trying to get another couple or few years before moving forward because they aren't that old and he's already over budget.
Other than this mosh posh with the boiler exhaust, there's a decent amount of HVAC needed and should be a lucrative job

PerryHolzman

I've actually seen either a furnace or boiler vented by underground pipe like what you are describing. It was in an industrial setting. I think they used 10" Sch 40 316 SS pipe for the section from the underground wall to the above ground exhaust vent. They actually purchased either a 30 or 40 ft length and had a pipe shop bend about a 85 Degree angle to create the riser (and then trucked in on a semi with other pipes for the plant). The exhaust fan was in the basement blowing the exhaust up the pipe (that was a commercial fan from a company that makes industrial induced draft fans). There was a drip leg from the bottom of the SS pipe to collect the drains, and it ran into a plant drain system that was designed to handle all kinds of nasty stuff.

Not cheap. But, that's how to do it and have it last...

Perry

Steamhead

HydroAir said:

These are hot water boilers not that old and in pretty good condition.

I appreciate all of the replies and get the general consensus.

I'll try to convince the homeowner that replacing the boilers now is the preferred way to proceed. He does want to do it, but was trying to get another couple or few years before moving forward because they aren't that old and he's already over budget.

Other than this mosh posh with the boiler exhaust, there's a decent amount of HVAC needed and should be a lucrative job

@HydroAir , better check with the local AHJ to see if they will allow venting the boiler(s) that way.

gennady

Boilers must be vented according their manuals. I never seen this set up in any manual.

Bob Harper

B-vent is not tested nor listed for use inside a sleeve. It requires a 1" clearance to combustibles in a ventilated space. It cannot be encapsulated. A power venter on CAT 1 can only be located at the termination. It cannot use positive vent pressure. A CAT III or IV vent must be pitched for drainage of condensate. I think your architect/ engineer has been reading the wrong comic books.