|
| Author |
Message |
larry
Member
|
# Posted: 22 Feb 2012 08:58pm
Reply
can anyone explain the difference between a 3in. tank-less water heater vent and a regular b-vent pipe?
|
|
greenacarina
Member
|
# Posted: 23 Feb 2012 03:44am
Reply
I believe the tankless vent is stainless and very expensive. When I changed my tank style to a tankless I ended up using the b-vent. Nobody could convince me why the stainless was necessary...most of the answers I got were "just because". Been a couple years now with zero problems. I would love to hear anyone's insight on this.
|
|
larry
Member
|
# Posted: 24 Feb 2012 07:43am
Reply
i do know if galvanized pipe gets hot enough the galvanic coating can burn and give off toxic gas. i really don't see it getting that hot. so my plan is to use b-vent for my tank-less water heater. after comparing the prices i think the stainless is just crazy. will let you know how it goes.
|
|
MtnDon
Member
|
# Posted: 24 Feb 2012 10:47am - Edited by: MtnDon
Reply
The tankless heaters I am familiar with use powered vents, a blower to horizontally vent the exhaust. The exhaust is hotter than a regular non powered heater. That's one reason. Standard vent pipe is also not rated for pressure exhaust. That's the other reason for the stainless with special locking joints. Sealing tape won't hold up under the heat.
Personally I would believe there is a reason id the mfg says so.
|
|
TomChum
Member
|
# Posted: 24 Feb 2012 12:04pm - Edited by: TomChum
Reply
Quoting: MtnDon Personally I would believe there is a reason id the mfg says so.
The reality, for many recreational cabins, is that if the only option is to "do it right" then you can't do it at all. Or other projects suffer budget-wise. Lots of folks are interested in researching a sensible answer in-between. Cabin folk get away with lots of offenses that a craftsman with a certain pride would never do. Plus many homeowners don't mind doing the job twice, whereas a contractor can't do jobs twice. Always remain cognizant that there are some things beyond your ability to second-guess, and burning propane is likely to be in that category.
Sometimes a manufacturer is forced to take a certain stance to relieve liability concerns. 99% may be good enough for people but only 100% protects from attorneys. Other times, just to relieve consumer complaints from bad installs or even just forum pressures. You can't even imagine all the trouble they've seen. If they wrote in the manual NOT to use Aluminum 'dryer vent', someone would use it and sue them and quote the manual. Someone's probably going to ask here "what's wrong with Aluminum dryer vent?" It's impossible to explain all the ins/outs - consequently the most conservative / expensive is their best option to publish. If you can't get valid advice from someone experienced, (and most likely NOT) then the conservative approach is good advice and may turn out to be the least cost in the end.
I suspect (as a non-expert) that stainless is recommended because galvanized coating could overheat in an extended-runtime + low-water-flow condition. Galvanized is toxic while burning off, but when it's gone, it's gone (from that hot spot), and no longer toxic. And then it will rust. Both of these 'failures' may not pose any problem at all to you. One option to economize is to use Stainless at the first elbow and first section, then go galvanized the rest of the way. But now you're electrically connecting galvanized to stainless which will cause your galvanized coating to "sacrifice" faster (corrode). If it's in the dry it may last long enough to satisfy you. If the B-vent doesn't last you can decide in 20 years (and maybe your checkbook has cooled off) to replace it all with Stainless. I would seal it with hi-temp silicone rather than aluminum tape.
|
|
larry
Member
|
# Posted: 24 Feb 2012 06:53pm - Edited by: larry
Reply
many good points tom. i will do some more research and come spring will let you all know how it works out.
|
|
greenacarina
Member
|
# Posted: 25 Feb 2012 01:53am
Reply
In my particular case I am using a Bosch water heater. No exhaust fan, just heat rising naturally...same as my tank-style water heater did. I didn't see how my tankless would be generating any more exhaust heat than the tank style (if it had an exhaust fan, I may have thought differently). Good info here...you guys have been more informative than Lowes and Home Depot combined! 
|
|
brokeneck
Member
|
# Posted: 25 Feb 2012 06:37pm
Reply
The tankless heater we have in our big lodge vents through an exterior wall with stainless --cost of through the wall was small.
|
|
|
beachman
Member
|
# Posted: 20 Mar 2012 05:25pm
Reply
I have installed a Selkirk vent system in our new camp - up through the ceiling and the roof. The vent is a type-B gas vent 5 inch. The whole system costs about $110 - but I needed another two pieces and try to get those... Well I have them on special order and it will cost about $90. I almost got another complete vent kit. You can see these vents at the Bosch hot water heater site. I purchased a Bosch 1600 LP model that we will install this Summer. Hope it all works.
|
|
larry
Member
|
# Posted: 23 Mar 2012 08:34pm
Reply
although i like the idea of tank less water heater it just want be possible. no one will warranty it if used on well water.
|
|
jeffgreef
Member
|
# Posted: 24 Mar 2012 11:09pm
Reply
Not absolutely sure, but I think I heard or read that with many of the newer high efficiency gas burning appliances the products of combustion are more acidic than with lower efficiency burning setups. That may be a reason for stainless- galvanized will eventually corrode.
B vents are generally used in naturally vented situations, that is, not under pressure, where the gasses rise by their own heat alone. In such a case they need air access from the bottom of the vent, so they can pull in air as the hot gasses rise. Look at a gas tank-type water heater, you'll see what I mean. But if your tankless is a forced-air flue type, you don't want this air access at the bottom. It needs to be sealed so the fan will not blow gasses into your cabin.
Manufacturers and testing agencies (like UL) carefully test their products and engineer them to operate with specific equipment. If you do other than what they recommend, you could create a dangerous situation without knowing it since you don't know the engineering of that particular product. I suggest you do what the manufacturer says, but if you don't, protect yourself with all the extra slack you can- keep the clearance to combustibles from the vent as far as possible, locate it where if it leaks the gasses won't get in your cabin, and check the thing periodically for corrosion or other failure.
Carbon monoxide detectors are cheap and readily available.
Please be careful with gas.
|
|
jeffgreef
Member
|
# Posted: 25 Mar 2012 10:03pm
Reply
Forgot to mention- many high efficiency appliances also have a lot more moisture in the exhaust gasses than less efficient appliances, and often the manufacturer instructs you to instal a condensate line in the flu itself to get rid of this, in a special fitting that attaches to the stainless flu. Galvanized B vents won't hold up as well to the moisture, and don't have condensate drain fittings. You could be dumping the condensate back into the heater with a B vent.
|
|
|
