engineer

Paul S_3

I'm in the beginning stages of a job....im working with the customers engineer...he has to draw out the plans then the building dept approves them. there is an existing 6 inch b vent chimney already there. not exposed....chimney runs about 45 ft to roof....total btus are (3) 40k water heaters and (2) 50k input boilers so total btus are 220k....when I look in my Selkirk manual it says that the existing chimney can handle the load and properly vent.....the engineer is insisting on us running a new 10 " bvent chimney....the engineer says "he does not feel comfortable with a 6 in chimney" am I wrong with my calculations ? this engineer is not budging and gets aggravated when I question this. I really do not want to run an exposed 10 in bvent ..also what happens when one water heater runs is the chimney oversized? he told me he never heard such thing...can that pose an condensation problem down the road?....thank you

ChrisJ

Paul S said:

I'm in the beginning stages of a job....im working with the customers engineer...he has to draw out the plans then the building dept approves them. there is an existing 6 inch b vent chimney already there. not exposed....chimney runs about 45 ft to roof....total btus are (3) 40k water heaters and (2) 50k input boilers so total btus are 220k....when I look in my Selkirk manual it says that the existing chimney can handle the load and properly vent.....the engineer is insisting on us running a new 10 " bvent chimney....the engineer says "he does not feel comfortable with a 6 in chimney" am I wrong with my calculations ? this engineer is not budging and gets aggravated when I question this. I really do not want to run an exposed 10 in bvent ..also what happens when one water heater runs is the chimney oversized? he told me he never heard such thing...can that pose an condensation problem down the road?....thank you

What does the manufacturer of the B vent say for multiple appliances?

You'll have to check for yourself, but this is what I just grabbed out of Simpson's Duravent book.

JUGHNE

Could he be not considering the height? That should suck your hat off your head with a little wind.
Delicate feathers to ruffle aren't they?

Can't believe an engineer would allow such small appliances in the first place .

Paul S_3

Thank you @ChrisJ ....im at around the same with the btus on the 6 inch on the Selkirk manual....he just insisting on the 10 inch because "he does not feel comfortable with the 6 inch"

ChrisJ

Paul S said:

Thank you @ChrisJ ....im at around the same with the btus on the 6 inch on the Selkirk manual....he just insisting on the 10 inch because "he does not feel comfortable with the 6 inch"

I wouldn't feel comfortable with the 10" at 45 feet.
My 6" 30 foot B vent pulls one hell of a draft when it's cold out, especially near 0F. That's why I left the barometric damper on it even with the drafthood.

Tinman

Are the boilers Cat I (Nat) or Cat III (Fan Assist)?

Paul S_3

@Stephen Minnich there CAT I natural draft

JUGHNE

Here is a generic chart from AGA & GAMA of 1991, no brand name or company associated with this info.
I doubt if these things change with time.

He is actually arguing with his peers as I would bet there were a lot of ME's involved in all three charts here.

Perhaps he is looking at vent connector capacity, that always kicks my but as I seldom ever run "B" vent at all.

Rich_49

Cold flues are cool . What is his reasoning for the 6xs larger than necessary vent ?

JUGHNE

Somewhere there must be a guide for the maximum oversizing of existing "B" vents for orphan water heaters abandoned when condensing boiler/furnaces are installed.

Just a gut feeling that the 3 standing pilots of WH's would be overwhelmed trying to warm an outside exposed 10" vent.
Then one of the boiler fires and backdrafts thru WH hoods until draft is established. Just a thought.

Paul48

Maybe there's an up side...It could be used as a cell tower

gennady

NYC fuel gas code. Chapter 5
http://www1.nyc.gov/assets/buildings/apps/pdf_viewer/viewer.html?file=2014CC_FGC_Chapter5_Chimneys_and_Vents.pdf&section=conscode_2014



6" dia 45' high can handle 300,000 btuhr.

Paul S_3

Thank you guys i appreciate it.... @Rich he says it will not vent...im meeting him at job in a couple days...im showing him the NYC fuel gas code sizing

ChrisJ

Paul S said:

Thank you guys i appreciate it.... @Rich he says it will not vent...im meeting him at job in a couple days...im showing him the NYC fuel gas code sizing

Well,
I'd say his rear end is venting, that's for sure.

Steamhead

Brewbeer

Paul S said:

Thank you @ChrisJ .....he just insisting on the 10 inch because "he does not feel comfortable with the 6 inch"

Ask him to show you his calculations that are making him uncomfortable.

rick in Alaska

Too bad you can't get a new engineer. Any engineer that says he "does not feel comfortable with it", apparently can't back up his engineering. Or he would just say, "this won't work, and here is why". Is he a civil engineer?
Show him the charts and hopefully he will agree with them.
Rick

jumper

Few engineers understand over&under pressure. I confess that I may fail qualifying for the few.

Jamie Hall

If I may... if you can educate this individual, that will be a plus -- for both him and your client. However, may I point out that if he (or she?) doesn't feel comfortable, he (or she) won't and indeed shouldn't put his or her stamp on it. It must be remembered that it is one thing to say "well, it's up to code"; that will usually serve as a good defense if things go pear shaped -- but not for an engineer. His or her stamp says, to put it simply, that he or she has examined whatever it is, has evaluated it, and personally guarantees that it will work as intended.

This is not intended to excuse ignorance on the part of the engineer (although if that is the case, he or she should not be in that particular area of practice -- but that's another story) but only to suggest why some engineers may be seen as rather stuffy or overly conservative.

For what it's worth, that italicized phrase is why I no longer practice as an engineer -- as an individual, there is no way that I could generate enough billing to afford the errors and omissions insurance (and I've never had a claim). I would need to raise over half a million dollars per year just to hang out my shingle -- and then fork over 20 to 30 percent of my gross fees on top of that. Not happening...

JohnNY

Tell him if you're signing the job off, it's got to be your way with this. You've got documentation and know accepted industry practices for which begin and end with manufacturer's testing and published tolerances, and Fuel Gas Code. Not the opinion of an engineer who doesn't care a lick about what a job is costing.
Is this a Staten Island job? Nothing good happens on Staten Island. I know. I lived there for 32 years.

Brewbeer

Jamie Hall said:

For what it's worth, that italicized phrase is why I no longer practice as an engineer -- as an individual, there is no way that I could generate enough billing to afford the errors and omissions insurance (and I've never had a claim). I would need to raise over half a million dollars per year just to hang out my shingle -- and then fork over 20 to 30 percent of my gross fees on top of that. Not happening...

Really? My firm does engineering (geotechnical) and other consulting disciplines (industrial hygiene, regulatory permitting, environmental compliance) and our errors and omissions insurance is about 0.5% of gross billings.

Paul S_3

@JohnNY ...no job is in Brooklyn....and i usually use my engineer

Jamie Hall

Brewbeer said:

Jamie Hall said:

For what it's worth, that italicized phrase is why I no longer practice as an engineer -- as an individual, there is no way that I could generate enough billing to afford the errors and omissions insurance (and I've never had a claim). I would need to raise over half a million dollars per year just to hang out my shingle -- and then fork over 20 to 30 percent of my gross fees on top of that. Not happening...

Really? My firm does engineering (geotechnical) and other consulting disciplines (industrial hygiene, regulatory permitting, environmental compliance) and our errors and omissions insurance is about 0.5% of gross billings.

Yeah... the percent of gross goes down as the gross goes up. A one-man firm gets really truly hammered. Worse, I would be working in hazmat (not compliance -- remediation)... where the potential liability for a screwup is unbelievable!

jumper

Courts and discipline authorities have become unfair to professional engineers. Used to be that if you documented concerns properly then your professional judgement ruled. Now you can get whacked no matter what. If you state a code exemption you can be guilty because you substituted your judgement for the consensus of some code writing committee. Who's never held liable. Or if you state that you decided to follow code then you're still liable. Engineers are paid extra just for their bird stamp.