Possible to Extend direct vent?

Users who are viewing this thread

protivakid

Member
Messages
31
Reaction score
0
Points
6
Location
MA
The direct vent exhaust pipe was placed right near my bathroom window. Talking to the furnace guy he said he was pretty sure it was against MA code to begin with but I am not the original owner of the home so this wasn't my decision. Anyways each time the furnace kicks on the bathroom and adjacent bedroom get a lovely fragrance of the oil burner's exhaust.

My thought was to get some pipe matching the diameter of the inside pipe, cut off the end screen of the current pipe, and extend only the inside exhaust pipe it all the way up just above my roof line. This would leave the outer fresh air intake piping as is.

Any thoughts on this? Problems with my plan or better ways to do this without completely doing an overhaul?

Here is a pic of my current setup:

0902151612.jpg


Thanks!
 
Last edited:

BadgerBoilerMN

Hydronic Heating Designer
Messages
485
Reaction score
10
Points
18
Location
Minneapolis
Website
www.badgerboilerservice.com
The appliance manufacturer will have a specific "approved" method for venting this unit. A skilled technician can decipher the factory installation manual and, following the local mechanical code, give you save options.

Simply extending any fuel fired appliance vent, more especially beyond the conditioned space is asking for trouble and may lead to premature equipment failure, personal injury or death.

Seriously.
 

Dana

In the trades
Messages
7,889
Reaction score
509
Points
113
Location
01609
Even with the non-compliant location for the you shouldn't be smelling exhaust when the furnace is running unless both

A: the windows & walls are pretty leaky and

B: The ducts & returns are configured such that the air handler is de-pressurizing those rooms relative to the great outdoors.

If this is in fact a boiler (and not a furnace thus), the air-leak factor at he walls/window is big, and you have big air leaks out the top of the house de-pressurizing the conditioned space.

Either way it's worth fixing, but it may take blower-door directed air sealing to find & fix all the bigger air leaks. It may also require adding jump-ducts or something for l0w-impedance return paths in rooms with supply ducts but no dedicated returns.
 

BadgerBoilerMN

Hydronic Heating Designer
Messages
485
Reaction score
10
Points
18
Location
Minneapolis
Website
www.badgerboilerservice.com
This is a vent configuration I detest, deflecting the byproducts of combustion radially along the load plane. Perfect for re-circulation to the living space. Again, check with the manufacturer for approved vent terminals and have the burner tuned for efficiency and safety--mandated by all oil-fired appliance manufacturers.
 

protivakid

Member
Messages
31
Reaction score
0
Points
6
Location
MA
Even with the non-compliant location for the you shouldn't be smelling exhaust when the furnace is running unless both

A: the windows & walls are pretty leaky and

B: The ducts & returns are configured such that the air handler is de-pressurizing those rooms relative to the great outdoors.

If this is in fact a boiler (and not a furnace thus), the air-leak factor at he walls/window is big, and you have big air leaks out the top of the house de-pressurizing the conditioned space.

Either way it's worth fixing, but it may take blower-door directed air sealing to find & fix all the bigger air leaks. It may also require adding jump-ducts or something for l0w-impedance return paths in rooms with supply ducts but no dedicated returns.

I apologize I should have been more clear. It's summer so our windows have been kept open most of the time and thus the smell creeping into the house. When they are closed we don't smell it at all. I thought a boiler & furnace were one in the same like basement & cellar but perhaps I am using the term wrong?

This is a vent configuration I detest, deflecting the byproducts of combustion radially along the load plane. Perfect for re-circulation to the living space. Again, check with the manufacturer for approved vent terminals and have the burner tuned for efficiency and safety--mandated by all oil-fired appliance manufacturers.

We just had it cleaned and tuned by the oil company and he said the same thing. That this vent configuration was the worst.

The common advice seems to be that I need to pull the furnace's manual (which I have someplace) and check out what options I have? Seems it's not possible to just extend some?
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
The difference between a furnace and a boiler is that a furnace is a hot air heating device (ductwork, blowing hot air to heat the house), and a boiler heats water...they are not the same thing! Now, you could use a boiler to run to what amounts to a radiator in the ductwork (I actually use that), but it is more common to use a furnace in this situation.

As has been said, you need to read and understand what the manufacturer's installation allows. FWIW, there is always some carbon monoxide in the exhaust, and that is the reason why there is a minimum offset distance required for ANY combustion exhaust system relative to openings or overhangs in a dwelling. IOW, it should NEVER have been installed directly beneath a window unless it meets the minimum distance requirements listed in the installation manual.
 

protivakid

Member
Messages
31
Reaction score
0
Points
6
Location
MA
The difference between a furnace and a boiler is that a furnace is a hot air heating device (ductwork, blowing hot air to heat the house), and a boiler heats water...they are not the same thing! Now, you could use a boiler to run to what amounts to a radiator in the ductwork (I actually use that), but it is more common to use a furnace in this situation.

As has been said, you need to read and understand what the manufacturer's installation allows. FWIW, there is always some carbon monoxide in the exhaust, and that is the reason why there is a minimum offset distance required for ANY combustion exhaust system relative to openings or overhangs in a dwelling. IOW, it should NEVER have been installed directly beneath a window unless it meets the minimum distance requirements listed in the installation manual.

I guess I have a boiler then as the home is forced hot water, no ductwork. As for the vent I'll pull the manual. It is just to the left of the bathroom window and even the next window down in the bedroom we can also smell it.
 

Dana

In the trades
Messages
7,889
Reaction score
509
Points
113
Location
01609
If you're keeping the windows open you're not running the heating system, so it shouldn't be running at all. Though you keep calling it a furnace, if I had to guess it's probably actually a boiler, and the reason it's running in the summer is that you're using it to heat your domestic hot water (?). Care to share the model & make?

A boiler is not a furnace (and conversely), and using a misnomer makes it confusing. (There may be a personal/regional dialect thing going on, but most of the folks I've known who use the terms interchangeably all seem to come from central PA , not MA, though one of them currently lives in MA.) If the thing is heating water internally (whether steam or pumped hot water), it's a boiler. If there is no water plumbed to it and the heat is moved via air ducts, it's a furnace.

As BadgerBoilerMN points out, simply extending the co-axial vent isn't likely to help much since the exhaust is being disbursed radially in a plane parallel to the wall. If there is a compatible vent terminal that blows the exhaust straight out and pulls the combustion air in from the sides it may help a little.
 

Reach4

Well-Known Member
Messages
38,796
Reaction score
4,413
Points
113
Location
IL
Are you sure that is a combination intake and exhaust? I am not familiar with the offerings, but that looks like it would do a particularly bad job. My suspicion is that that is exhaust only, and the intake air comes from inside.
 

Dana

In the trades
Messages
7,889
Reaction score
509
Points
113
Location
01609
If it's a co-axial the air-intake is probably on the bottom (where it won't be subject to direct rain intake) and possibly obscured by the angle of the pic, which is how many of the coaxial side terminals work. But it could also simply be exhaust only.

Either way, it looks as if it may be possible to pry the deflection cone out with a screwdriver, if that's deemed legit per the manual.
 

protivakid

Member
Messages
31
Reaction score
0
Points
6
Location
MA
Here's what it looks like inside. Yes the intake vent us underneath and doesn't show in the original pic above.

The boiler is a PB WV-DV-03-WPCT and the burner is a Beckett 7505 which the oil guy said are cheap units.

0910151125.jpg
 
Last edited:

Dana

In the trades
Messages
7,889
Reaction score
509
Points
113
Location
01609
The output of that Peerless is probably 3x your design heat load, which isn't great for as-used efficiency, but it's unfortunately a common scenario in MA. The smallest jet they ship it with is 0.75GPH, which has an output of 92,000 BTU/hr. A typical ~2000' post Y2K vintage code-min house in MA would have a design heat load of about 25,000 BTU/hr @ 0-5F, often less. Even an antique that size that's been tightened up and insulated would be under 35,000 BTU/hr.

Almost no houses in MA really need a 92,000 BTU/hr output boiler- it's less than 5% of the market (guesstimate), but to cheap out on water heating these oversized boilers get installed with tankless coils. The instantaneous hot water load could easily be 92,000 BTU/hr, but only for a few minutes at a time. In the meantime the boiler has to idle at an elevated temperature (= much higher standby losses), to ensure that just in case somebody needs to wash their hands or something.

Assuming you have the space for it, you could get higher net efficiency out of it if you installed an indirect fired hot water tank as a separate zone, giving that zone priority over space heating zones, and installed a heat-purging economizer control such as the Intellicon 3250 HW+, and set it up for cold firing. The standby loss of a well insulated indirect hot water tank is a small fraction of the standby loss of a boiler maintained at 160F or whatever.

But if oil is headed for a buck a gallon after Iran floods the already glutted oil market during the China slowdown, maybe that doesn't matter(?) . :)

According to the manual, they only ship one type of vent terminal for this unit. Section 4 on page 7 (p.9 in PDF pagination) they start with the notice:

This boiler is shipped with a Z-Flex Vent Terminal carton, and a Z-Flex Venting Components Kit. The following components from these two cartons must be used in the installation of this boiler:

· Z-Flex Oil Vent Terminal
· Z-Flex Vent Pipe
· Z-Flex Appliance Adapter
· Z-Flex Terminal Adapter
· Z-Flex Sealant


That reads like they don't have an alternate terminal approved for use with this boiler.

They spell out the minimum clearances to windows & snowpack depth, etc in figure 4.2. If it's directly under a window you need a minimum of 4', but it can be as close as 12" to the side of an operable window, but needs to be at least 4' from the side of the power meter, etc. More clearance is (of course) always better.

It's not clear from the boiler picture whether they've met all of the access & clearance specs on p.3 (p5, PDF) of the manual either but it might.

Get out your tape measure and verify it all. Height-wise there's no way the exhaust terminal would have stayed 12" above the snow line at my house in this past winter, (and it wasn't even a record year for us, though it was close.)
 

protivakid

Member
Messages
31
Reaction score
0
Points
6
Location
MA
The output of that Peerless is probably 3x your design heat load, which isn't great for as-used efficiency, but it's unfortunately a common scenario in MA. The smallest jet they ship it with is 0.75GPH, which has an output of 92,000 BTU/hr. A typical ~2000' post Y2K vintage code-min house in MA would have a design heat load of about 25,000 BTU/hr @ 0-5F, often less. Even an antique that size that's been tightened up and insulated would be under 35,000 BTU/hr.

Almost no houses in MA really need a 92,000 BTU/hr output boiler- it's less than 5% of the market (guesstimate), but to cheap out on water heating these oversized boilers get installed with tankless coils. The instantaneous hot water load could easily be 92,000 BTU/hr, but only for a few minutes at a time. In the meantime the boiler has to idle at an elevated temperature (= much higher standby losses), to ensure that just in case somebody needs to wash their hands or something.

Assuming you have the space for it, you could get higher net efficiency out of it if you installed an indirect fired hot water tank as a separate zone, giving that zone priority over space heating zones, and installed a heat-purging economizer control such as the Intellicon 3250 HW+, and set it up for cold firing. The standby loss of a well insulated indirect hot water tank is a small fraction of the standby loss of a boiler maintained at 160F or whatever.

But if oil is headed for a buck a gallon after Iran floods the already glutted oil market during the China slowdown, maybe that doesn't matter(?) . :)

According to the manual, they only ship one type of vent terminal for this unit. Section 4 on page 7 (p.9 in PDF pagination) they start with the notice:

This boiler is shipped with a Z-Flex Vent Terminal carton, and a Z-Flex Venting Components Kit. The following components from these two cartons must be used in the installation of this boiler:

· Z-Flex Oil Vent Terminal
· Z-Flex Vent Pipe
· Z-Flex Appliance Adapter
· Z-Flex Terminal Adapter
· Z-Flex Sealant


That reads like they don't have an alternate terminal approved for use with this boiler.

They spell out the minimum clearances to windows & snowpack depth, etc in figure 4.2. If it's directly under a window you need a minimum of 4', but it can be as close as 12" to the side of an operable window, but needs to be at least 4' from the side of the power meter, etc. More clearance is (of course) always better.

It's not clear from the boiler picture whether they've met all of the access & clearance specs on p.3 (p5, PDF) of the manual either but it might.

Get out your tape measure and verify it all. Height-wise there's no way the exhaust terminal would have stayed 12" above the snow line at my house in this past winter, (and it wasn't even a record year for us, though it was close.)

Thanks so much for taking the time to write a detailed post!

Looked at the manual and I agree, they tell you to use the included vent system without giving any other options. Kind of implies that if you are cheap enough to get this boiler then use the cheap vent system as your only option. The house is only a few years old built with 2x6 and very well insulated. We also have a pellet stove that heats the house most days in the winter so really this boiler is used primarily for hot water. Getting a separate hot water tank may not be the worst idea taking a lot of the load off the boiler.

As far as options would perhaps getting rid of the cone on the end (and replacing it with some sort of screen to keep small animals out) help push the air out instead of along our wall? At this point it looks like extending the pipe isn't an option for me.
 

Dana

In the trades
Messages
7,889
Reaction score
509
Points
113
Location
01609
If you're heating primarily with the pellet stove you might consider installing a heat pump water heater HPWH) in the basment and not using the oil for heating hot water at all. The cost of installing an indirect is going to be about the same as a 50-80 gallon GeoSpring (dependingon your hot water needs. Either of them has an EF north of 3, which makes it cheaper hot water than the oversized oil boiler w/indirect that's spending all it's time idling, even at recently higher electricity rates in MA. During the muggy days of summer the HPWH will be doing most of the latent-cooling of the basement, drying it out. If you're currently running a dehumidifier in the basement to avoid the musty basement smell, a heat pump water heater would take over most of that function.

Just mothball the hydronic system for the summers- flush the crud out of the boiler and thermally cycle it before turnign it off, maybe adding a heating system water treatment, then don't fire it up again until it's close to the time when you might actually need it.

FWIW, rather than "very well insulated", 2x6 / R20 has been code-min in MA for awhile. From the pictures it looks as if you have NO foundation insulation (at least in the boiler room), which means the standby losses of the boiler are in fact mostly going outdoors (through the ~R1 above-grade concrete) rather than accruing to the conditioned space of the house. If you don't have foundation insulation it probably means you also have no under-slab insulation, which is another sink for wasting the standby heat.

The true heat loads of most IRC 2009 or IRC 2012 (=current code minimums in MA) runs about 11-13 BTU/hr per square foot of conditioned space @ 0F, but many slightly-better-than code houses come in at under 10 BTU/hr-ft^2 . Most locations in MA have 99% outside design temps north of 0F, and many are in positive double digits, so it's entirely possible that even with no foundation insulation your heat load at design temperature is in the 10 BTU/hr-ft^2 range, depending on your ZIP code, and it's very unlikely to be as high as 15 BTU/hr-ft^2 (which would be typical of tight 2x4 construction, or typ. 2x6 / R19 houses of the 1980s.) Unless yours is an unusually large house, that boiler isn't really going to serve the loads every efficiently, even if you WEREN'T heating mostly with a pellet stove.

You'll want to test-fire it a week or so before it's needed just to shake out any issues, but that might not be until late December. Turn the aquastats down to keep the low-limit at ~140F. I'm not sure what the exact low limit needs to be to avoid excessive or damaging condensation for that- it may be totally cold-startable, but it may also not be- I'd have to look that up, but you can too. If the baseboard/radiation is sized for emitting even half the full output of that boiler at 200 F boiler output, it means you probably have enough radiation to heat the house with 150-160F boiler output. It's something that you can figure out with a few tweaks during the cold-snaps, but the cooler the average temp of the boiler, the lower the standby & distribution loss to the outdoors. If you were going to forgo the pellet stove it would be worth installing heat-purging boiler controls, but if it's serving as just your backup there's not much return on that. The biggest return would be getting rid of 90% of the annual standby losses simply by turning the boiler off.

Even if you're not actively heating the basement, it's worth insulating the foundation to IRC 2012 levels where it's accessible (MA is US climate zone 5, except for Martha's Vineyard & Nantucket.), so it takes at least R15 continuous insulation. That would be either 2.5-3" of continuous rigid polyiso on the interior of the foundation wall all the way down to 1/4" off the slab (the gap needed as a capillary break, if there's any chance of moisture wicking up from the footing), or an inch of polyiso trapped to the wall with a 2x4 studwall (with an inch of rigid EPS under the bottom plate of the studwall as a thermal & capillary break from the slab), insulated with either un-faced R13-R15 batts, or kraft faced, but not foil-faced, and with no interior vapor barriers such as polyethylene sheeting.

A 2x6/R19 studwall would also meet code for thermal performance but that creates a serious mold hazard in a zone 5 basement. With the foam on the exterior of a 2x4 wall it can be set up to dry toward the interior, and there is sufficient R value on the exterior of the susceptible wood that the cavity won't accumulate moisture from the conditioned interior during the winter- the average temp at the foam/fiber boundary stays above the average dew point of the conditioned space air.
 

protivakid

Member
Messages
31
Reaction score
0
Points
6
Location
MA
Thanks again for the detailed reply. All great stuff for me to consider next year if my budget allows. Before it gets too cold to work outside though I wanted to address the smell situation if possible. It looks like they say to only use 3'-20' for the exhaust. This would rule out my idea of extending up past the roof line but do you think cutting the end cone off would help? At least that way it would blow out away from the house.
 

Dana

In the trades
Messages
7,889
Reaction score
509
Points
113
Location
01609
Getting rid of the cone may help the smell problem but it's not clear if /how that will affect the operation of the boiler. I suspect it's not a huge problem, but I'm not on the hook for the warranty, nor did I design the thing, and they give zero guidance on alternative venting. The fuel/air ratio in the sealed combustion may or may not be sensitive to that change, but would have to be verified by your burner tech who just tuned it up. Is it worth the extra service fee?

Keeping those windows closed is probably your best option.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks