New water heater / chimney drafting problems


On 12/21 I had a new 40-gallon natural gas water heater installed in my 69-year old house. The water heater is vented via a dedicated chimney/flue. Previous heater was 13 years old and making lots of noise (I just closed on the house 12/20). New heater is Rheem (but under the GE label). 9-year warranty.
New heater working fine for about 2 weeks. We go out one day, come back after a few hours and I mention to the wife that I smell exhaust and/or gas -- from around the draft hood on the water heater. I notice that the plastic caps that surround the hot/cold water pipes are melted where they extend under the hood. I know this isn't right, so I call the installer (local company contracted out by Home Depot).
They send a tech out. He takes a look in the flue and says it must be a clog somewhere (but not where he can see) and that it's not his problem: call a chimney sweep.
So I do. They come out and do a more thorough investigation inside. Can't find anything -- and flue seems to be drafting OK, but they agree to come out with a 40-ft ladder the next day and remove the cap (fancy copper, shaped like a 'T') and advise me to install a carbon monoxide/natural gas detector. I do -- reading remains at '0'.
Next day they remove the cap -- and an old, compacted squirrels nest (no longer in use). They replace all the screening, clean everything out -- and the water heater is now drafting out the flue like a champ.
That was 4 days ago. Now tonight I notice a similar (more faint) smell of exhaust. I turn on the hot water tap in the basement sink; water heater kicks in. Top of heater (draft hood and area underneath) get fire-hot, exhaust pipe remains cool to the touch (initially). I let it run for a bit, don't notice much of a change (pipe began to get a bit warmer) -- then I crank open a couple of the glass block window vents and the thing begins to vent much better (top of water heater cools off, exhaust pipe gets hot).
I am at wits end. Any idea what could be going on here? With my most recent gas bill (furnace is old, oversized and needs replacing), I can't afford to keep the basement windows open (previous owner did not need to). Could the heater itself be defective?
I am a 1st-time homeowner, and while I consider myself somewhat handy, this one has me stumped. And I'm getting close to want to go back and be a renter -- this has become ridiculous. Do I really need to scrap the new water heater and replace it with a power-vented unit? That seems crazy since this house has been here since 1938 and has used a normal, dedicated chimney-vented flue since its construction 69 years ago.
Help!
Thanks.
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There is not enough combustion air to the water heater. More efficient water heater probably has a cooler flue temp and can't overcome the heg pressure in the room that it's in.

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I was thinking something along those lines -- but what should I do now? Do I need to replace with a power-assisted water heater? Do they make kits you can retrofit a std water heater with to make it a power-assist? Would shutting the door to the furnace room help at all? The house is old and not very well insulated -- but their are all-new Pella windows (that have been here since 2005) -- still plenty of "leaky" spots, though.
Advice?
Thanks.
Terry wrote:

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snipped-for-privacy@yahoo.com wrote:

No, don't shut the furnace room door.
I would think a leaky old house (even w/new windows) would have plenty of draft available. Is it possible that the furnace was running at the same time the heater came on? (It should not affect it, but just curious.)
The point about the flue taking too long to heat up is well taken. This heater is in an "orphan" chimney. I would consider dropping a metal flue liner down it. This could be a very cost-effective solution. The liner (aluminum or stainless per local practice) will come to operating temp in minutes and produce good draft.
Don't give up and rent! If this is your biggest problem, you are well off...
Jim

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Funny thing is -- there is a metal flue inside this chimney (this was sort of a 1938 "designer" home so it featured things the average home didn't necessarily have at the time).
I think the furnace was on at the time. And it's a BIG furnace (way oversized) -- it is a Bryant, installed in 1971 (I just had it serviced and the tech told me it really needs to be replaced because it is way oversized and overdue). It is actually (2) Bryant furnaces "daisy-chained" together (because at the time, they told the owner that "we don't make a furnace powerful enough to heat your home -- you'll need two..." -- putting out 165k BTU. Tech told me a quick look tells him I shouldn't need more than 100 BTU for this home.
The squirrel didn't come back -- I've eyed the screens, they're intact (one side was missing before the sweeps came out). Plus, the nest was old -- it would have to be his relatives that came back, because he's probably long dead!
I am going to check to see if there is perhaps a return air duct in the basement that is closed -- perhaps this is causing a problem...
Thanks -- I'll give you an update once I know something. I'm trying so hard to be a good homeowner and show this house the love it deserves (example: I cleaned out the ash pit on Saturday -- and I am the FIRST owner to do so, because I emptied about 150 pounds of ash, mortar, brick, cement, porcelain fixtures, red oak flooring (including a piece that was nearly 5 ft long!), scrap wood, steak bone, tin cans -- and a newspaper, dated August 11, 1938. I figure that the guys laying the hardwood floor had lunch and tossed a bunch of this down the ash door in the floor of the fireplace. It was stacked so high inside it was ridiculous.
I'm really trying to help this house stick around for another 69 years -- but this issue with the water heater is driving me crazy!
Speedy Jim wrote:

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snipped-for-privacy@yahoo.com wrote on 21 Jan 2007:

Assuming that the furnace(s) and the water heater share a chimney, there should be no problem with the chimney being warm enough for a good draft. OTOH, those furnaces have got to be sucking a huge amount of combustion air out of your house, making a backdraft down the chimney very likely.
Despite the house being old, I suspect those Pella windows have reduced the available amount of makeup air significantly.
If you replace the furnace(s), you might consider a high-efficiency unit that obtains its combustion air from outside the house and vents through the wall. That will eliminate the furnace as the source of any backdrafting. But then the water heater will be the only user of the chimney, which may then be too large, so you may yet need induced draft for the water heater.
You may also be able to install in the furnace room a makeup air vent to the ouside that opens only when the furnace is on.
Sounds as if you have a good HVAC tech who knows how to do heat loss calculations. Get him and your chimney sweep to advise you. Unfortunately, some trial and error goes with this process. In the mean time, keep a close eye on your CO detector.
--
Doug Boulter

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Doug-
Great advice -- and you're right, I think those (2) furnaces are indeed sucking a huge amount of combustion air out of the house -- and I plan to replace them with a high-efficiency (90+ AFUE) unit in the spring. I'm leaning towards Trane or Rheem -- but Bryant is in the top (3), too...
Here's what I did last night that seemed to help: checked the ductwork in the basement for any blocked or closed vents/returns. There is a single large return that is unblocked -- but there were (2) vents (one in the "newer" ductwork run in the 70s, I think) and (1) buried in the cement-finish ceiling where I can't actually see the duct, just the vent.
They were both closed.
I opened them both, figuring that it would improve and negative air pressure situation in the basement (2 vents closed, 1 large return sucking more air away from water heater).
This seemed to help. The top of the water heater cooled off, and the flue pipe got hot. So far, so good.
The new furnace will be vented out the side of the house (probably right through the chimney; neighbor has it that way) -- but the water heater actually has it's very own, dedicated chimney and flue -- totally on a different side of the house, so I'm hoping it can stay that way.
I'll post again if I find out more...
Thanks!
Doug Boulter wrote:

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Could the pissed off squirrel have come back and built a new nest? It is doubtful that a 69 year old house would be so tight as to require a window to be open to vent a water heater. Does the main heater fire ok? Was it firing while the water heater was not venting properly? It may be causing the down draft for the water heater.
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snipped-for-privacy@yahoo.com wrote:
I can only offer that the flue pipe should be cold. In fact, the pipe should be two pipes, one inside the other for just that reason.
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HeyBub wrote:

try making a little smoke around the heaters draft hood, see if smoke is sucked up chimney.........
try opening window or door a little so heater can pull enough fresh air for combustion
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