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Air for Combustion
bob_25
Member Posts: 97
Tim, Just out of curiosity have you ever measured the CO from one of them gas log setups with the trough of sand for a burner? bob
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Comments
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What affects Air for Combustion
From time to time here on the Wall questions have come up about Air for Combustion (One of my favorite subjects along with CO). In particular DRYERS and the affect they have on air requirements. I thought I would post some interesting information.
In the National Fuel Gas Handbook authored by Ted Lemoff P.E. he states the following concerning dryers:
"Type I clothes dryers (residential dryers) exhaust fans typically range from 180 cubic feet per minute (cfm) to 200 cfm. Higher exhaust models may exhaust up to 250 cfm. The air exhaust rates include air for removal of moisture, as well as the air needed for combustion of the fuel gas. For example, models with 180- cfm require 10,800 cubic feet per hour of makeup air. A gas dryers energy input ranges up to 35,000 btus per hr regardless of exhaust rate. Which at a rate of 10 to 1 for complete combustion is 350 cubic feet per hour. Therefore a dryers combustion air is only about 3 percent of the total air required for dryer operation. It goes on to say farther on in the code section that list requirement for installation of dryers, that it is a mandate to provide "make up air". Because this amount of air would include sufficent combustion air, the code requirements for combustion air need not be applied."
In the section on requirements for make up air it states the following:
"The quantity of make up air required for dryers exceeds that of other gas appliances. Generally, five to ten times the air required for an appliance of similar heat input should be allowed (similar would be say a 35,000 BTU water heater)." That means the typical 350 cubic feet of air required per hour would be 350 times 10 or 3,500 cubic feet for the dryer not including all the other equipment. Even on the low end it is 1,750 cubic feet.
Let it be noted that in many cases I have found that equipment installed in a confined area in the basement do not have adequate air for combustion. People get alarmed when I walk in and without any measurements tell them they have insufficient air. It is a no brainer - when I see the dryer and no provision for air I do not need to measure anything. The dryer creates a definite problem no matter what.0 -
What
do the clothes dryer manufacturers say about this Timmie?
Mark H
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Most instructions on Dryers
do not even mention air for combustion or any sizing for air requirements.0 -
Thanks
I had a feeling about that.
Had a situation the other day where a young couple purchased a new gas stove from a big box (Lowes)
They told the salesperson that they would be connecting to LP gas and asked if they needed to convert it. The Lowes person said "No".
Well needless to say the thing was producing HUGE amounts of CO.
I read the instructions and I couldn't find anything in them that differentiated between fuels.
Scary stuff!
Had a furnace last week that was spewing 2100ppm co diluted!!!!!
Undergassed and the air shutters were almost completely closed.
Even after I made the adjustments it was still over 1000ppm.
20+ years old and it's outta' there.
While you were out, look at the boiler we found.
It has been serviced every year for the last 15.
Kinda' tough to miss this wouldn't you say?
Mark H
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What condition...
do you think caused it to fail? I presume we're looking at a bottom burn out?
I've never seen anything like that.
ME0 -
Thanks, Tim
I just printed that one, it's a real eye opener.0 -
Sealed dryer?
Why couldn't a clothes dryer get its intake/combustion air from the outside?.
Never seen such a thing, buy why not?
If negative pressure from your dryer causes you to need a heat recovery exchanger it becomes a very expensive appliance...0 -
Good points
As a design engineer, this air flow and air requirements info has always been difficult to obtain from the appliance suppliers and manufacturers. In this modern age of well sealed buildings and much lowered infiltration rates, the air required for combustion and make up air to residential appliances is now a serious issue. Many of the leaky condo envelope failures in the Pacific NW are now educating the residential building designers as to the critical issues around proper indoor air pressures, and adequate ventilation of residential spaces. This is likely becoming a serious issue in the colder climates of North America where buildings are even better sealed. Unless the home or apartment has some source of dedicated outdoor air for ventilation, there is serious danger.
Direct vented/makeup connections for dryers and gas ranges are a good idea, but don't forget, in a cold climate, the heater size of the dryer has to be sized to account for heating up that cold outdoor air, PLUS sized to dry the clothes in a reasonable amount of time. Could add 12,000+ Btuh to the dryer heater size just to warm up that colder air to the design setpoints. Plus the Architects will hate having to try to locate all the appliances on outside walls, or dealing with furred walls for vertical duct drops from additional roof jacks.0 -
dryer air
air is required for electric dryers too not just gas ones . And people can't figure out why their houses are sooty.0 -
mechanical space allowances
High Time for the builders and designers to make space for the needed mechanical components of the building, and if they need to cut cost cut the ginger bread junk that falls of the wall in a couple of years anyway.0 -
I can't begin to tell ya...
how important this is for ANY combustion appliance, be it dryer, water heater, boiler, furnace or range. Another problem we find here in the East has to do with the industrial-strength range hoods that get installed in the kitchens in most step-up and better homes. Those things really move some air, but unfortunately, the builders & designers or architects don't think of where the air to replace it is coming from, and as we all know, it's got to come from someplace, usually the chimney or fireplace flue.
I feel like a broken record when I say this, but when will they learn that the house is a system and the performance of any one component effects all the others?0 -
combustion air
is not to be trifled with. Because of the stone masons and HUGE fireplaces, "unusually tight construction" and adequate sized combustion air inlets blocked by tenants that "felt cold air coming in", this licensed plumber and trained heating professional installs damned few atmospheric vented boilers. Get your air from outside, pipe it to your sealed combustion boiler, (Burnham Spirit is a good choice) and quit trying to compete for the inside air. Sleep better, make more money, and be responsible.0 -
> is not to be trifled with. Because of the stone
> masons and HUGE fireplaces, "unusually tight
> construction" and adequate sized combustion air
> inlets blocked by tenants that "felt cold air
> coming in", this licensed plumber and trained
> heating professional installs damned few
> atmospheric vented boilers. Get your air from
> outside, pipe it to your sealed combustion
> boiler, (Burnham Spirit is a good choice) and
> quit trying to compete for the inside air. Sleep
> better, make more money, and be responsible.
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"combustion air is not to be trifled with. Because of the stone masons and HUGE fireplaces, "unusually tight construction" and adequate sized combustion air inlets blocked by tenants that "felt cold air coming in",..."
I couldn't agree more. So let me work through an example for a new 6200 sq. ft. residence which is being built using ICF concrete construction and super insulated and air-sealed.
Say you have a sealed combustion boiler, eg. Viessmann Vitodens or Munchkin, or whatever is correctly sized, etc... No problem here.
Now we add a big wood burning fireplace - which we are trying to convince the architect to provide outside air intake for,.... and the customer wants a big 48" gas cooktop in the kitchen with all 5 burners going at once, and 2 wall mounted gas ovens running at the same time.
Add to that the upstair and downstairs clothes dryers running at the same time on laundry day or when the cleaning staff arrives for the weekly cleanup and are spraying this chemical cleaner or that disinfectant.
And the exhaust fans going in the bathrooms while the teenage kids take showers for 40 minutes.....
Code here says I need a minimum of 600 cfm kitchen exhaust for a gas cooktop. But this customer is worried about the 'sight lines' to the lake from their island located cooktop. So they want a monster commercial roof-mounted exhaust fan to the cooktop hood can be more than 30" above the cooktop surface and still draw fumes out, so we're talking 1000 cfm here!!!
We look at Venmar (VanEE) ERV's to deal with steady-state air quality issues, but when the big range hood fires up we need to bring a ton of air inside in a hurry.
It isn't such a big deal in the summer if the windows are open, but if the a/c is on it can be a problem. In the winter the makeup air should be pre-heated.
I'm looking for something I can use to interlock with the range hood that will allow me to pre-heat the makeup air.
Since we are using hydronic heating in the structure, my best approach so far is to use a hydronic air handler to run the cold makeup air through (hoping the heat is on or even treating it as a zone calling for heat) before we dump the warmed air into the kitchen and laundry areas.
Any suggestions?0 -
I have not done this
But I have a strong feeling it would work very well indeed. (This is in reply to your question about preheating incoming air) I think if a person installed a hydronic coil in the airstream of the HRV and used a trv with a remote sensor mounted in the duct, your reheat situation would be solved easily, simply and efficiently.0 -
Overkill
Once the heating system is taken care of, I think that calculating total max air replacement need for all of these
appliances being on at the same time is a bit overkill. A fireplace should have outside cumbustion air just to save energy of sucking warmed interior air. All high end ovens are electric, not gas. I think a simple solution to negative air pressure (if it exsists) in a laundry room or maybe in a kitchen cabinet under a large range top with access to an outside wall, attic or basement, would be to install a louvered outdoor dryer vent on the interior, ducted to the outdoors. While a dryer or a hood exhaust was operating, I doubt a cold draft would be felt if a warm dryer was running or heat from the range top warmed the kitchen. Remember that bathroom and hood exhausts are not air tight when off, probably pulling fresh air into a closed space when some other appliance is tring to create negative air pressure.0 -
Over kill?
You should take the Guru of Partially Burnt BTU's (A,K,A, Jim Davis) course on Carbon Monoxide poisoning.
You will come away with a unique perspective of a person who has seen most of it all, and has done everything.
Over kill is a bad word to use when talking about the potentials of carbon monoxide poisoning. It comes from more than just the appliances we're used to dealing with.
If you're not testing appliances at commisioning time, you're guessing, and gambling with lives.
I see JennAire grills cause CO poisoning ALL the time.
Take this course.
http://www.ncinstitute.com/Seminars.htm#Schedule
ME0 -
It is not overkill
It is a very complex issue we are dealing with here. I can tell you that after over 40 years in this business and over 3,600 gas conversion buners installed and set up that air is a major issue today. It is vital to the prevention of de-pressurization of homes and the ultimate prevention of Carbon Monoxide. I agree with Mark get to Jim Davis's course or if you are in the east come to my classes. You will leave with a very different perception of this problem.0 -
Has anyone thought about this...
With all the air we bring from outdoors into buildings in order to insure complete combustion and safe equipment operation we are changing the ultimate heat loss in the building.
Does anyone figure that when doing a heat loss? Just curious.0 -
I agree 100%
on issues related to gas heating equipment. But let's not call every Viking commercial 6 burner grill a killer. If dryers and range tops were a problem why are there no fresh air building codes only on exhaust? Sure we all want healthy home air quality, but I don't think a 10 grand fresh air/heat exchanger is realy needed in most cases. Just require fresh air combustion intakes for all heating and fireplaces.0 -
In Denver...
if your kitchen exhaust move more than 200 CFM, you MUST provide relief air in the immediate vacinity of the appliance.
There have been numerous cases where the range cause CO Poisoning.
As a matter of fact, water heaters and boilers are responsible for 75% of CO poisoning cases. F.W.I.W.
Better safe than sorry. I don't want any of my customers waking up dead...
ME
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Most commercial ranges and ovens
have very high levels of CO right out of the box. They require proper set up and venting/ventilation. Having set up many commercial kitchens an example :
A Bldgett commercial oven brand new 1,500 ppm out of the oven. After proper adjustment and set up of intake and exhaust air we left it at 25 ppm. Same equipment with 8 top burner running at 12,000 BTU's each (96,000 btu's total)making 250 ppm in the air 30 inches above ccoktop. With proper adjustment of primary and secondary air and intake of fresh outdoor air "0" ppm CO.
When we start putting what used to be commercial equipment into homes we have to be doubly careful.
Watch out for Jenn-Air units when running they need a lot of air and can cause negative pressures in the area they are operating in.0 -
Many times the codes have
not caught up with the problems.0 -
Joe - do you test every
gas appliance in the house for possible Carbon Monoxide? Do you do a combustion analysis on all heating and water heating calls? If you do not test you do not know. This should not be taken lightly, everyone needs to be testing and making sure the quality of living for our customers is safe.0 -
Here is another one for you!!!!
All you technicians that work in the inner city of many of our major cities in particular the North east. What about all of those console heaters (space heaters) and gas on gas kitchen heaters. Many still around you would be shocked if you tested some of those.
Think about this a gas on gas range 4 top burners 40,000 BTU's, oven 22,000 BTU's and the heater 30,000 BTU's that is 92,000BTU's in that kitchen, right around the corner in the living room a console heater 50,000 BTU's. The total 142,000 BTU's potential load on that apartment. Is there a dedicated air intake to those pieces of equipment? NO!!! Then somebody gets real smart and decides to install an unvented space heater in a spare room another 30,000 and NO VENT. Sound way out - not really I had that very situation last winter here in the Providence area. People were getting sick and could not figure out why.
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commercial ranges in residential homes
> have very high levels of CO right out of the box.
> They require proper set up and
> venting/ventilation. Having set up many
> commercial kitchens an example :
>
> A Bldgett
> commercial oven brand new 1,500 ppm out of the
> oven. After proper adjustment and set up of
> intake and exhaust air we left it at 25 ppm. Same
> equipment with 8 top burner running at 12,000
> BTU's each (96,000 btu's total)making 250 ppm in
> the air 30 inches above ccoktop. With proper
> adjustment of primary and secondary air and
> intake of fresh outdoor air "0" ppm CO.
>
> When
> we start putting what used to be commercial
> equipment into homes we have to be doubly
> careful.
>
> Watch out for Jenn-Air units when
> running they need a lot of air and can cause
> negative pressures in the area they are operating
> in.
According to the International Mechanical Codebook 2000, adopted here in the state of Alaska, section 917.2 says "cooking appliances designed, tested, listed and labeled for use in commercial occupancies shall not be installed within dwelling units or within any area where domestic cooking operations occur.0 -
commercial ranges in residential homes
According to the International Mechanical Codebook 2000, adopted here in the state of Alaska, section 917.2 says "cooking appliances designed, tested, listed and labeled for use in commercial occupancies shall not be installed within dwelling units or within any area where domestic cooking operations occur. You said when we start putting what used to be commercial equipment in homes we need to be careful. Please reconsider whether you should put commercial equipment in the home at all. In addition to Jenn Air, there are plenty of other commercially styled units that are specifically designed for domestic use.0 -
fresh air requirements
> on issues related to gas heating equipment. But
> let's not call every Viking commercial 6 burner
> grill a killer. If dryers and range tops were a
> problem why are there no fresh air building codes
> only on exhaust? Sure we all want healthy home
> air quality, but I don't think a 10 grand fresh
> air/heat exchanger is realy needed in most cases.
> Just require fresh air combustion intakes for all
> heating and fireplaces.
The International Mechanical Codebook 2000, adopted here in Alaska, table 403.3 lists the required outdoor ventilation air in private dwellings, single and multiple. If your jurisdiction has not adopted this code or does not enforce it, I am sorry to hear that, however realize that fresh air intake, especially in cold climate (tightly wrapped) homes is not just a luxury, it is a life and death necessity.0 -
fresh air requirements
The International Mechanical Codebook 2000, adopted here in Alaska, table 403.3 lists the required outdoor ventilation air in private dwellings, single and multiple. If your jurisdiction has not adopted this code or does not enforce it, I am sorry to hear that, however realize that fresh air intake, especially in cold climate (tightly wrapped) homes is not just a luxury, it is a life and death necessity. Venmar and a handful of other companies make air to air heat exchangers that allow complete compliance with the code while scavenging most of the heat that otherwise would be lost, and as a mechanical contractor, I can tell you that the systems don't have to cost "10 grand" to a builder or homeowner, but even if they did, the savings in doctors bills, and mold/mildew/moisture damage would cover it.0 -
Commercial cooking Equipment
Most of these that are being put in residences are not classified as commercial. However from my many years of experince they are commercial cooking equipment. The specs and rating plates are listed for residential but the design charcteristics are certainly commercial. When you start putting 6 burner double oven ranges into a residential setting attention needs to be payed to venting and ventilation no matter what their classification.
One home I was in recently with a full commercial kitchen was actually installed by a restaurant service company. The local inspector classified it a commercial kitchen as long as it meet all the criteria for same, which it did. This is a $2,000,000 dollar home.
My sons new home has commercial equipment with commercial venting and ventilation equipment in the kitchen. As long as all the criteria for a commercial installation are met then around here they will pass the installation.0 -
Yes I did about a year ago at
a hotel I was staying in. They had that type of decorative fireplace in the lounge area. I noticed it was running with a very high flame and very yellow. It also had the glass doors open. I went and got my CO tester, about a foot in front of the fireplace I had 1500 PPM. Those are never supposed to be operating with the doors open. They also better have a good venting system.
I actually did some follow up on that installation with the company who put it in and the manufacturer. They said there was something wrong with my CO tester. I was using a dedicated CO tester (Bascomb Turner). So I went back in that area the next day with my Bacharach tester, this time I had 1200 PPM, after the unit had been running for an hour I checked it again and it was 1500 ppm.
They got real upset with me because I shut if off and made it inoperative at the managers request. I was able to convince him to looking into a better type of fireeplace insert with low CO activity. I have not been back there in a while.
Those units definitely make high levels of CO.0 -
I was working on a vented pizza oven at a ski lodge a few years back. Pilot was dirty and the thermocouple was weak. Cleaned everything up and fired the oven up to observe the burner. The cook came in while I was looking through the observation door to the burner area and started up the exhaust hood; the burner flame came flying out the door right at my face. I moved faster than I thought was humanly possible to avoid being burned. The ventilation system was new that season and nobody gave makeup air a thought when it was installed. Come to find out it was pulling the smoke from a woodstove back into the building at times and also the exhaust from the oil fired furnace in the basement. They couldn't figure out why it was happening. This lodge was a big open room with cathedral ceilings about he size of a basketball gymnasium. It taught me to keep an eye looking behind my back.0 -
GOOD points Mark. We do HRV's in the majority of the places we work on, as I know you guys do as well.
Still doesn't answer the high cfm range hood, regardless of its commercial or res. rating. When the 200 cfm HRV has a tug of war with the 700 cfm jen-air guess who wins. Throws the balance of the whole system out a bit and burns holes in the nice carpet, when the fireplace is being used.
We are in the midst of a job, where the home owner is installing a commercial 1400 cfm range hood, and they also have a wood cook stove in a a different part of the same kitchen!! Not to mention the oil fired boiler system, which even though its in a sealed seperate room w/twice the combustion air than needed, its still going to be a problem, since its not sealed that good.. The have promised to downsize the range hood some and promise to open the window in the kitchen when turning it on. I have promised them that it will smell like there behind the school bus, in their living room, every time they use the range hood, and it still hasn't quite sunk in.
Code is one thing. Enforcement is another.
Steve
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