water heater flue backdrafting

Bruce_6

furnace guys installed a new furnnace, power vent 80,000btuh. now water heater has pilot problems.

any guesses??

the WH and furnace flue are connected 5" from furnace 3" from WH connecting with a tee 6" in horizontal position, runs for 2 feet, then turns vertical.

what causes the backdraft? it only happens when the furnace is running, tested with a smoke pen, you can see the puffing back and forth. when the furnace goes off, the backdrafting stops.

lchmb

question? what type of power vent water heater do you have? most now have ignitor's..I would also guess that pulling the tee and putting in either a tee wye or a wye itself wouldn't hurt...

kevin coppinger_4

sounds like there...

is a power vented unit AND an atmospheric water heater sharing a common flue....this is a no n...NOT code, very dangerous....get power vent to go out seperate from flue...kpc

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Bruce_6

it

is an old style water heater, with the new furnace being power vented into same flue.

the problems didn't start til after the hvac company installed the furnace. the furnace used to be an old american standard with standing pilot, no problems with draft.

now that the new furnace is in, we have pilot problems with the WH.

tombig

Wye Tee

In some areas common venting is allowed. Check the local codes. The power vented appliance should wye into the flue.

Mike Kraft_2

DANGEROUS!!

Check the furnace manual for exhaust venting.This will be very specific.Venting a draft induced appliance through an existing chimney is not allowable other than usign the chimney for a "conduit" for a very specific venting "install schedule".As far as combing a atmospheric drafting appliance with a draft induced.....forget about it.

cheese

Bruce_6

I

will be going back to change the flue. I have checked the code, and it is allowed.

the power vent should be in the branch portion of the wye??

as it is now, the WH is in the branch portion of the tee. this stuff sits in a basement, and not much room for rearanging things.

lchmb

so what you are saying is you have a power vented unit into a chimney along with an atmospheric hw tank..cannot do this...look in your owner manual under venting and see what it is listing...if they didn't leave this give the name and model of the unit and btu rating..see what we can give you..

Mike Kraft_2

interesting...................

I am a non scorhed air guy.I hope I stand corrected from my post below.There I go assuming things.Just sounds like a bad scenerio.I am going to my truck and dig in NFPA code.

cheese

Mark Hunt

Fan assisted furnace


with an atmospheric water heater right?

Call the company back and get them to fix it IMMEDIATELY.

The furnace is venting into your house.

Call them right now!

Mark H

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Jack_23

Creepy!

Check the rating plate for the furnace. Is it Cat I or III. Big difference. What model/manuf power venter and WH. Does the chimney have a metal liner or is it just a good ole (not) masonry liner. Is the power venter on the furnace really a "draft inducer". Are you mistakenly calling the built in inducer motor on the furnace a "power venter". With this info we can better answer your question. Per your current description (*as I interpret it)...it does not sound good.

Murph'_5

yeah what he said

get this unit shut off before someone dies!!!



Murph'

Mark Hunt

P.S.

I do not want to have to post about this family on the "CO again" thread.

This isn't something that should be left until Monday morning, it needs to be addressed NOW!

I would bet money that neither of those units were tested for CO and unless they are, you can't possibly know how much CO is being pumped into that house.

We definately know that the heating company did not test THEIR installation. If someone gets hurt or killed in that house, the water heater will be blamed.

Don't wait.

Mark H



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Bruce_6

shame

on me because I did not test either! I should have, but the furnace and water heater are turned off til I get back there tomorrow. tho Owners are staying with friends tonight. I will bring my testo tomorrow!

I am not a furnace tech, and I might have confused a draft inducer motor for a power vent unit, sure sounded like a power vent, but the backdrafting is the main issue.

the flue is not in a chimney, it is double wall flue type B vent straight up through the roof. I was not even sure the furnace and water heater could be vented together, as one is a possible power vent. the code here states it can be done.

I will be on the job tomorrow, and get it fixed one way or another. I might have to add an additional flue, a lot of work, but that would be better than the existing conditions.

don't worry mark, you won't be reading about these people in the news!

lchmb

chris..I applaud you for asking and taking steps necessary to protect your customer's.. as to the code allowing a power vent and atmospheric unit being vented together..never personally heard of it. and don't know of a oem that allow's for it..I would tread lightly there...sound's like the best option is to put in the second chimney..as to there not being a chimney..;) there is, the b-vent is your chimney..same thing differenet material..good luck..
btw...if your code allow's for it I would still fall back on the manufactoring directions'..check with them to see if they allow for common venting with another unit and see if they specify what type's..

Mark Hunt

You're Awsome!


Those folks are lucky to have you looking out for them!

Keep us posted!

Mark H

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jim lockard

jack

Think your right they are calling an induced draft furnace a power vent.

October Home

You See?

You see why I read the posts on this forum!

Arlene

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tombig

Induced draft

I also stand corrected somewhat. I ASSUMED it was draft induced furnace and OK to common vent in some municipalities. It turns out I was right but when it comes to venting, assumptions can lead to more than usual consequences. Way to jump in Mark,Cheese, and the rest.

Brian_24

Per Jim Davis the CO guru in my humble opinion the proper way to vent the water heater and draft induced furnace is to use gas barametric controls on both appliances. You will have to add spill switches for both appliances. I have done this many times and it always works. Code does allow common venting of these two appliances however it is not a good application. Hart and Cooley recomend the furnace vent to be the closest to the chimney. I have found that this still does not cure the spillage problem. You will also find that after a period of time the chimney will stop spilling but I am not comfortable with any spillage.

don_16

Not enough

B vent after the tee,it should be 7" and even bigger depending on how far it got to go,before it passes roof peak.

Dont let that draft inducer fool you,it only there to pulled the air and flame thru the hx,after that well we
like to think it become a natural draft furnace.

Where Timmie?

Murph'_5

Good eyes Chris

As BKG says they need changed, take a no tolerance approach. what works one day (perhaps when they were installed) may not work under different scenerios. pressures change from outside to in, the rules of nature do not, the pilot is the least of thier problems!!




Murph'

Unknown

What do the manufacturers

instructions for the furnce say? As someone else mentioned we need to know what Venting Category. There is provision on the National Fuel Gas Code to vent "Fan Assisted" with "Natural Draft" equipment. I would be careful with starting to remove draft hoods and putting in barometrics without professional help and approval from manufacturers. Jim Davis is the "Guru" and I know he would be the first to tell you to get someone trained in this kind of alteration. Let us all slow down here and get some information.

Make, model, serial numbers of equipment, input, flue sizes and what does the installation manual for the furnace say. With this information we can determine if this equipment can in fact be connected together. The requirements for Type "B" vents can then be addressed.

I would tell you to leave this equipment shut off until proper information as to venting can be obtained. I will also tell you that many times even when this type of hook up follows all the rules and instructions you may still have problems with the "natural draft" appliance working correctly when both are running.

Bottom line the equipment will need to be combustion tested.

MIKE6

venting

In our area we vent water heaters atmospheric burning and fan assisted furnaces together all the time.We use a tee or wye as close to the chimney as possible.Make sure the chimney is clear.

Greg Swob

As ususal, Tim hit right on.

We had a similar situation here. Did some forensic inspecting and found the Type B in attic ran virtually horiz. way beyond limits. And... in this case, home had been vacant for some time, birds had entered flue cap and nested within flue. Revised the vent in attic, removed 5 gal. bucket of nesting material, changed cap to a finer screened, high-wind type- no more problems. Check what you have for venting all the way to and through the roof in your preplan investigation. Draw it out & compare to NFPA 54 or local codes and the HVAC appliance installation manuals. Your customers have a good man on the job! Greg