High Efficiency Gas Furnaces and Hot Water Heaters - Is the Chimney Obsolete?

[JHZR2]

Hi,

In my home, I have a gas furnace (hot water) and hot water heater. Bth vent up the chimney.

The HW heater is about 6 years old, the furnace is about 22. The HW heater needs to be net to almost full hot to get good temperature for the shower... The furnace runs excellently.

My chimney needs some repointing and potentially some tera cotta work in the upper flue. No telling what needs to be done until some bricks start being removed... I guess it has the potential of being a pretty high dollar task to repair fully.

I dont have a fireplace, this is a small single flue chimney.

I have seen a lot of houses that have these new high efficiency furnaces and hot water heaters. I guess they have a bunch of extra recouperators in there or something like this, as thye vent out of the side of ones' home, through nothing but white PVC pipe!

Is this the wave of the future? Should I not worry about the chimney? Heck, should I have it removed from the roofline, and the remains within the house structure filled with concrete and re-bar? I can just wait until the furnace goes, then replace both with HE units.

Putting two holes in the side of the house seems a lot easier than doing a partial chmney rebuild.

OK, sure, if I bought a new furnace and HW heater tomorrow, or in a year from now... it would likely be *** for another 25+ years; enough time for me to think and rethink how to deal with the chimney. Its not like the chimney doesnt work or is in danger of falling over anyway... Its just that some pointing needs to be done, and the tera cota on the top is broken/chipped.

But do you think this will be one of those things where in x years, the only things that will be available are HE gas furnaces and water heaters, and thus I'm wasting $$$ to get a real good job done on the chimney? Id hate to spend a few thousand $$$ to repair it properly, then in a few years when the furnace goes, be stuck putting holes inthe side of my home anyway, and then having no use of the chimney, it essentially going to waste.

Sorry for the babbling... your opinions please?!?

Thanks!

JMH

 

[Matt_S]

A couple thoughts:

It's becoming more and more common for cities to require stainless steel chimney liners for any new furnace or hot water heater installations. This prevents the moisture from the flue gasses from getting into the chimney structure, which should greatly enhance the chimney's life in the future should you choose to repair it.

Second, I would put my money on chimney-vented furnaces and hot water heaters being around for quite some time to come. The primary reason for this is simplicity. Most current hot water heaters don't need electricity to run as the high-efficiency ones do. That's a big advantage and makes for a much simpler, more reliable machine. Also, the 80% furnaces are much simpler, more reliable and cheaper and easier to fix than their 90% counterparts. Add to this the fact that it takes more than a few years to get your payback from a 90% furnace, even with the high cost of gas these days.

So IMO, unless the government comes up with a high efficiency mandate of some sort, which I think would be a mistake on their part, you're going to see non-high efficiency heaters well into the future.

 

[joatmon]

I installed two 90%ers about 10 years ago. I found that the total price, including furnace and venting, to be about the same for 90% vs. 80%. The PVC savings was about equal to the cost difference of the furnace. The HVAC guy told me that the Trane units should have similar repair experience. I've had no problems with either furnace in that period.

BTW, American Standard is a Trane in a different dress. Usually a little cheaper. My FIL went with the AS and is very satisfied.

 

[Brett Miller]

All high efficiency furnaces vent with PVC. When mine was installed a stainless steel liner was placed in the chimney to vent the water heater. It is required by code.

 

[Papa Bear]

"High Efficiency Gas Furnaces and Hot Water Heaters - Is the Chimney Obsolete?"

YES...We removed the chimney from our 1905 1 1/2 storey brick to run duct work up to the second floor. Installed a new (this was in 1990)Ultra 90 Bryant furnace w/ac and high-eff water heater. The furnace has had 1 igniter in 16 yrs.
The house looks a lot nicer too with no chimney.

P.B.

 

[Gary Allan]

Looks like they heat exchange on this setup

 

[PandaBear]

What about HVAC your furnance? Then you don't need to worry about duct and chimney, have an AC for the summer, and very good efficiency.

On demand water heater should be able to support one shower and kitchen at the same time. If you are not using hot water continuously for a long time it is a worthwhile investment.

 

[thooks]

I design HVAC systems and do Plumbing design for a living.

Your post was somewhat difficult to read, but I think I got most of it.

High Efficiency furnaces (90%+ split systems) have been around for over 10 years. They aren't "the wave of the future", they are current. I've had a Lennox Pulse 92% furnace in my home for 10 years. Runs like the first day.

I do not have a high efficeincy water heater. BTW, if the water is hot, you don't need a water heater ( just a little industry pick on "Hot water heater" ).

The "wave of the future" on Water Heaters is also here, has been for over 4 years. It's called an "Instaneous Water Heater" or "Tankless". Most are gas-fired, and your consumption on your typical 4-member household will drop 30% monthly. Little more if you have a new front-loading washer.

Your local gas company utility should be a great source of information about these. Your local Lennox dealer should be helpful about the furnaces. I do not work for Lennox or "push" them professionally. They do make some fine equipment and they are very strict on their dealers. They just don't let some billy-bob shade tree sheetmetal beater that works out of his 14x16 tool shed install their equipment.


As for the exhaust(and intake) on these systems, it is done with 2" Schedule 40 PVC pipe. There is an additional 120v blower on the tanked water heaters.

On the Tankless, it is usually mounted outside on the wall, and there are restrictions on how close it can be mounted from a window and/or door. They also require a 120v circuit to operate. There is hardly any power draw, it is more for the electronics and opening the gas valve.

Anymore questions, please ask.

 

[Bret Chase]

quote:

---

Originally posted by thooks:
The "wave of the future" on Water Heaters is also here, has been for over 4 years. It's called an "Instaneous Water Heater" or "Tankless". Most are gas-fired, and your consumption on your typical 4-member household will drop 30% monthly. Little more if you have a new front-loading washer.
[/QB]

---

they're only new in the residential market.. the tankless heaters are nothing more than a "booster" that have been used commercially (esp for comm. dishwashers)for a long time. there was one in the kitchen at a holiday Inn I worked at 15 years ago.

 

[JHZR2]

OK, dumb question... how does a gas-fired instant on water heater work, compared to a standard one?

Off the top of my head, id think that either there must be some constantly (VERY) hot intermediate thermal transfer fluid, so that it can be heated and heat can be exchanged over a larger area than a flame could.... or else there has to be a relatively large flame through relatively small baffles, and besides the point that its not heating anything when anyone is home, it seems that there would neeed to be a lot more gas used during high draw situations to maintain temperature (unless they are recouperated multiple times or something along those lines) due to the space velocity of the exhaust passing through the system.

So how do they work?

Thanks!

JMH

 

[JHZR2]

Post II:

And given that these high efficiency machines ARE here and the common things to use... how do you think they effect the offerings f 'standard' efficiency machines that utilize a chimney, both today and as we go into the future?

If Im thinking about doing chimney work, in your opinion should I simply forgo it due to the fact that likely Ill be uying a PVC vented HE heater and furnace in the future?

Chimney repair is an expensive proposition, so I need to see whatsthe smartest for the future...

The third floor is unheated... It might be nice to fill the chimney from the basement up with cement and re-bar, then just have it operational in the attic, and have a vented gas heater there that runs stainless the few feet to the chimney outlet...

JMH

 

[labman]

I am a skeptic on tankless water heaters. The numbers don't add up. The claimed savings are more than my entire gas bill in the summer time with a gas dryer too. You will only have instant hot water and eliminate water cooling off in the pipe, if its size allows relocating it closer to the point of use. The big problem is minimum flow rate. If I buy a unit the size appropriate for my 4 bedroom house, it isn't going to kick on at all for many of our typical uses.

The other thing is clearances you need around it. I would like to install one in the crawl space near my 80,000 BTU furnace to eliminate the lag due to the length of pipes. Can't meet the clearances. Electric is not an option.

They also mostly specify expensive SS vent pipes, not the PVC vents.

 

[Gary Allan]

quote:

---

Originally posted by Bret Chase:

quote:

---

Originally posted by thooks:
The "wave of the future" on Water Heaters is also here, has been for over 4 years. It's called an "Instaneous Water Heater" or "Tankless". Most are gas-fired, and your consumption on your typical 4-member household will drop 30% monthly. Little more if you have a new front-loading washer.

---

they're only new in the residential market.. the tankless heaters are nothing more than a "booster" that have been used commercially (esp for comm. dishwashers)for a long time. there was one in the kitchen at a holiday Inn I worked at 15 years ago. [/QB]

---

The gas fired instant water heaters are nothing new in residential settings. Do you think daddy warbucks waited 20 minutes for some central heated water source to get to one of his 15 bathrooms ..or maintained 700 gallons of hot water in 10 water heaters? They used the gas fired heat exchangers in many big houses. I've seen them.

quote:

---

Off the top of my head, id think that either there must be some constantly (VERY) hot intermediate thermal transfer fluid, so that it can be heated and heat can be exchanged over a larger area than a flame could.... or else there has to be a relatively large flame through relatively small baffles, and besides the point that its not heating anything when anyone is home, it seems that there would neeed to be a lot more gas used during high draw situations to maintain temperature (unless they are recouperated multiple times or something along those lines) due to the space velocity of the exhaust passing through the system.

So how do they work?

---

The only ones that I've seen almost look like an auto muffler ..except wider and flatter. They're shielded (covered). They're stainless steel (or so they appear) and they spread the flame over a very large surface area. I don't know how it happens ..but the flame kinda clings and climbs the honeycomb of the exchanger. The velocity of the water much be very slow. I've seen the newer versions on This Old House (or one of them feature length commercials where anyone who can afford the stuff has no interest in actually working that hard).

The type I've seen in the past kinda resemble this ..they may be longer or whatever in "vintage" trim.

 

[JHZR2]

wow... nothing to that thing... except surely a big price tag...

JMH

 

[muddawgs]

i went tankless 3 yrs ago and dont regret it at all. i was very hesitant but went ahead after talking to a few people the had them in my area for many years. i purchased a gas fired bosch aquastar from controlled energy corporation(15 yr warranty) and had a local plumber install it. they must also be vented with the proper size outlet and material. i think mine was 5 inches.. i can use 2 services at the same time fine if i need more it starts to lag and is not as warm then. this seems to be a common fault or complaint. but the kids can take a endless shower and the wife can wash dishes to her hearts delight at the same time. my gas bills compared to previous years from the meter readings and the $ was enough to pay for itself within a year. several neighbors and family members have changed out after heater failure or leaking tanks to the same model or similiar models as mine with the same or better results. it cut my elderly neighbors bill by more than half from what they tell me. mine is located in the same location as the previous 40 gal tank and is transparent as far as how it works or reaches the faucet. the typical sized 40gal heater lasts about 6-8yrs in my area due to water quality etc... i wouldnt hesitate to install it again or have it installed from the get go if one is building a new house.