weak draft, chimney lining

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Old 07-06-12, 07:13 AM
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weak draft, chimney lining

Hi!

I had a 30 yo gas fired boiler with atmospheric venting. Itís not the most efficient unit, but itís working ok and I hope I never have to replace it. But in case if I do I want to know what I want as a replacement.

Few months ago I had an energy audit done in my house. The guy found that my draft was weak and with clothes dryer running in the same room (basement) and a fan in the bathroom upstairs it was border line backing up. He said it was probably chimney obstruction.

A month or so ago I took the boiler apart to clean it and also took down all the venting ducts. Ducts were all clear and so was the chimney Ė I could see it all the way to the top crown and could see some day light. I realized itís probably my big effort of house air sealing that resulted in the air restriction and weaker draft.

For multiple reason I want to stick with atmospheric venting for my new boiler. Simplicity, cost, DHW boiler that also uses the chimney, existing infrastructure is among them. So I would like to address the draft question, but Iím not sure if there is anything I could do. I could be conscious about not to run dryer and any fans at the same time, but I think thatís about as much as I could do to remedy the situation. Is there anything else?

Also researching different types of venting I came across several mentioning of chimney lining for atmospheric venting. My chimney seems to be just bricks and mortar. Am I not up to code because it was done 30 years ago or did I misinterpreted the requirements?
 
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Old 07-06-12, 12:29 PM
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The weak draft

Most building codes require a seperate air inlet the same size as your chimney flue opening. You are flirting with killing everyone in your house with CO poisoning. the pros will tell you how to procede, in the mean time open a window in your boiler area to get some air to the boiler.
Sid
 
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Old 07-06-12, 12:34 PM
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Sid, I appreciate your concern, but i don't think i'm flirting with anything, since it's still passed the inspection and I have the co detectors everywhere.
 
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Old 07-06-12, 05:33 PM
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I have to think that, in a highly-regulated state like MA, some sort of chimney liner is a code requirement. That being said, you might want to hold off on a new liner until you take the plunge and replace your old boiler with a new one, assuming that's in the cards in the not-to-distant future. That way you can select the best liner for new boiler application.

Regarding your immediate problem, try and find a way to introduce more outside air directly into the basement. If there is a basement window that opens, then you can fashion some sort of vent cover for it.
 
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Old 07-07-12, 10:16 AM
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Another option to look at:

Google "Fan in a can"
 
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Old 07-07-12, 02:40 PM
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The draft

Just saying that with a dryer and an exhaust fan running,especially at the same as your boiler with natural draft, you could possibly create negative pressure in your tightly sealed home. A fresh air opening, or indused draft, as Trooper suggested should help.
Sid
 
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Old 07-11-12, 07:42 PM
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I am not the biggest proponent of fan in a can on new boilers but it is a good product. It solves many existing boiler problems but if you need one with a new boiler the wrong boiler was chosen. Again it is a good idea for the situation you now have. Some other options are an elephant trunk, vents to the out side to name a couple.
 
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Old 07-11-12, 08:41 PM
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Not a pro, but what about adding a make up air intake next to the boiler? They are as easy as running some insulated flex duct and looping into a "J" by the boiler.
 
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Old 07-12-12, 08:11 AM
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guys, thanks for you help.

fan in the can might not work for me without some duct work redesign since i have a boiler and HW heater converge right before the big duct goes into the wall and into the chimney. i would have to move the T with the HW heater and put the fan in the can right after that.

since my draft is only marginal under the worst conditions i think for time being i will be mindful not to have a fan in the bathroom and dryer in the boiler run at the same time. without them running the draft was ok according to the energy audit dude.

i have an opening on the bottom of the chimney for ash cleaning from the fire place. it's 5 feet below where boiler exhaust enters the chimney. my fire place is not functional at this point (plugged), so i'm wondering if sealing that opening on the bottom of the chimney would increase the draft?

on one hand it will let the air flow thru the boiler only and into the chimney, so it seems like it would help. on other hand, the draft from the lower opening might create some venturi effect? but then it's not design for that at all, it's simply to collect the ash.

rbeck, i'm curios about the "elephant trunk". i search online and found one forum that actually referred back to you on this forum and there wasn't much explanation there. i search on this forum and found this post of your:

The air intake pipe I call an elephant trunk, goes down to the floor, 2 elbows to create a "U" back up the wall about 1/2 to 3/4 of the way and again 2 elbows. This traps the air and only comes in when the room goes into a vacuum.

Read more: http://www.doityourself.com/forum/bo...#ixzz20PwAV95W
i have hard time visualizing this, do you have any links, pics for this?

NJTrooper, you mentioned that he tried it, do you still have it or did you take it down since it wasn't visually pleasing to you ? if you still have it, can you share some pics?

thanks!
 
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Old 07-12-12, 05:57 PM
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fan in the can might not work for me without some duct work redesign since i have a boiler and HW heater converge right before the big duct goes into the wall and into the chimney. i would have to move the T with the HW heater and put the fan in the can right after that.
Eh? I think you might be thinking that 'fan in a can' is a 'draft inducer' that mounts in the flue pipe?

No... fan in a can is a fan in a can that is connected to a duct leading to outdoors. The fan is controlled by the boiler firing. It runs and draws outdoor air when the boiler is firing.

NJTrooper, you mentioned that he tried it, do you still have it or did you take it down since it wasn't visually pleasing to you ? if you still have it, can you share some pics?
Confused... I never used one myself. There is no shortage of outdoor air in my installation!
 
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Old 07-12-12, 06:53 PM
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My chimney seems to be just bricks and mortar.
I would say definatly need a liner.


What is the dimension of the chimney opening and heght?

What size flue is off the boiler?

What size flue goes into the chimney?

How is the HWH hooked up, with a Y and what size?


How many BTU is boiler and HWH.

Mike NJ


 
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Old 07-12-12, 07:43 PM
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By the code you do not have a chimney you have a chase. The code states a chimney needs a liner of some kind. We all talk about lining chimney's but he code calls it re-lining as to be a chimney it already requires a liner.
 
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Old 07-13-12, 07:47 AM
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NJTrooper, I think you're right, i'm confusing draft inducer with a fan in a can. As for elephant trunk, it seems that you tried it 6 years ago and probably forgot about it:

http://www.doityourself.com/forum/bo...ml#post1311087

lawrosa,

the original boiler was installed 30 years ago, so i guess it was either ok by the code back then or it was wrong to begin with. since i've decided to go direct venting, i guess it's irrelevant now.
 
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Old 07-13-12, 04:21 PM
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Ohhhhhh... THAT Elephant trunk!

Two completely different things, same moniker.

The one I used was on the FLUE PIPE, where the barometric damper resides. Instead of installing the damper directly into the flue pipe, an extension is used to drop the damper down and away from the flue pipe in order to create a bit of 'expansion' space for the flue gases when the burner first fires. Gas fired systems don't use baro dampers.

The one they are talking about here is obviously for INTAKE COMBUSTION air...

It's a moot point really, since it's not the same thing, but yes, I do still have it connected, and yes, it serves it's purpose. It's kinda ugly to some, but then, I have a jaundiced eye. The things I think are beautiful are eyesores to many... like a 100' tall tower in the backyard with a tri-band yagi on top... BEAUTIFUL! Neighbors don't dig it too much though.
 
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Old 07-13-12, 08:04 PM
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Imagine this for the elephant trunk. Outside the building is an elbow with a critter screen on it.
Through the wall to an elbow inside directing to the floor. Pipe down to the floor with two elbows which send the pipe back up the wall. Go up about half way and install two elbows connected together to head back down. Going to the floor and back up creates an air trap. When the room goes negative the air will come out of the pipe. When the room is not negative air stays in the pipe. No fans, now electri and no switches.
 
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Old 07-14-12, 08:22 AM
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rbeck, that's pretty cool. as far as i understand, cold air sinks to the bottom of the trunks and sits there creating a trap. but i would imagine if it's windy outside it would still leak a lot of air in..
 
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Old 07-14-12, 08:32 AM
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if it's windy outside it would still leak a lot of air in..
Only if the wind created enough of a pressure difference within the home to cause airflow in the trunk. Which unless the home is very tightly sealed, is quite possible.
 
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Old 07-15-12, 08:59 AM
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T is the purpose of the elbow outside to keep air from blowing directli in. The air must go up, then down, move the air at the bottom up the wall, around two more elbows and back down. It has to change direction 6 times which creates resistance.
 
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