well you could add a regular say 40 gallon tank, and just trurn it off during the cooling season. in pittsburgh the AC season is very short, so standby is trivial.
some tanks are forced vent with fan running only when burner is active. this would elminate the loss up the flue, which ultimately exhausts heated home air 24/7 forver.
that loss of heated air likely exceeds normal standby losses.
You are partly right -- the Bosch 2400E has vent assist during burn & positive forced vent for 60 seconds after burner shutdown to clear flue of any residual combustible gasses. However, this is a non-heat loss issue to living space as the heater has a 3-inch air intake vent flange which I have plumbed through ceiling to roof intake vent. So no heat loss there either. Not sure if other tankless heaters do this though.
some tankers use outside air intake, so inside heated air isnt wasted for venting.
at some point your $ spent could of been invested in things like insulation with better payback.........
I use the small 170000btu battery ignition Bosch with incomming of down to 35 at the coldest point, my main incomming is in a hill that has lost dirt over the years so its getting shallower, I have never needed to set it more than 75%-80% to get a hot shower. For tanks your standby loss is up the chimney through the center of the tank which is uninsulated, that is why tank have an Energy Factor of around 55-65, this is a much more realistic rating than AFUE. So i dought you benefit from heat loss into the home, rather you net loose through chimney draw and heat comming out the center of the tank. Tankless Energy Factor are near AFUE, mine is about 80. What I did was leave in the old tank as a tempering tank, then the water goes to the tankless. Some makes turn on at less a flow than mine but that is an issue, you basicly turn it on or only down a bit, but why overheat water, set it hot enough to take a hot water only shower, you will save $. The biggest problem I would guess installers make is not testing supply with a manometer with all competing gas apliances on so be sure 100% tankless output can be reached on the coldest days, and not calculating low winter mains supply on the coldest days. For single use the 117000 btu is fine but if someone else needs HW while you shower the 190,000 btu unit is needed. Two tankless together are for apartment buildings, not regular homes.
Modern boilers have auto vent stack valves that close when the boiler shuts off to help maintain the heat in the boiler, I have heard this adds 2-5% in efficency, I do not believe water heater tanks use this. This contributes to the low Energy Factor rating of tank water heaters, which is a more realistic value of efficency. Tankless dont have this issue. Europeans-NG importers have known this for years, thats why most of Europe uses tankless, Research Energy Factor of Tank water heaters and compare it to Tankless
Thank you, this is what I have been saying all along, that tankless are more efficient than tank-type, period. But there are some in this thread who will argue you every different which kind of way to justify their stubborn decision to own tank-type heaters, sometimes even claiming that tank-types are cheaper. I believe I will give up now on trying to convince folks that tankless are cheaper in the long run.
Regarding your comment on most of Europe using tankless: from 1969 to
1970, I lived in a small town in Belgium. When I first got there, I wondered what the white box was near the bathtub. As soon as I turned on the hot water, I found out. It made a lot of noise, so I went to investigate and determined it was an instaneous hot water heater. In those days, they were quite primitive compared to today's instantaneous heaters. This one had a pilot for ignition, so it did not use any electricty. After this, I began to notice that -- as you pointed out -- almost all European homes had, and still have, tankless heaters. Must be a reason, eh? $$$$
europens homes tend to be smaller, so a tankless in a small home saves space. high end europen homes have tanks.
tank type with forced thru the wall venting naturally doesnt lose heated air up the flue since it only vents during operation. but feel a tanks sides, if they are warm its helping to heat your home.
true theres losses up the flue but most of the tanks walls are inside your home not up the flue
my whole point was letting perspective tankless owners know what thew downsides are, after all its a expensive conversion.
You may as well give up. There are enough factors that must be taken into account that no clear answer on which one is more efficient has been proven in this newsgroup. The people who are focusing on "Europeans use them" are bringing in irrelevant, nationalistic information and further clouding the issue.
It would be nice to read an unbiased and thorough study of the matter. I think that people in the US would be happy to move to a different type of water heater, if it could be shown to be more efficient. Natural gas and electricity prices are not going to get any cheaper. I'm ready to give up my tank right now, if it gives me a return on my investment.
Such a study must consider the ways that people use hot water and the amounts of water needed in a specific period of time. It must also consider initial costs and ongoing costs.
I want to know that a tankless unit would be able to keep up with the demand for hot water for several people in a row taking showers. I want to know that a tankless unit that size won't cost a fortune to buy. I also want to know that the enormous, instantaneous blast furnace that would be necessary to heat that much water won't use just as much fuel as the more gradual gas usage of a tank water heater.
Bernardo
Thanks to all who contributed their positive and negative feedback, as well as a large amount of related useful information concerning tankless vs. tank-type domestic hot water heaters. I am satisfied enough with the replacement of my ancient tank-type hot water heater with a new Bosch
2400E (nat gas) that this post will most likely be my last. I filtered this newsgroup for my own posts, and discovered that I had written no fewer than 30 posts -- and some of them fairly lengthy. So, I have invested some time into this discussion thread, as well as others of you who have taken the time to respond. For that, I say thank you. I may monitor this thread tonight just to see if something turns up that I just can't live without... but other than that, I'm signing off until the Next Home Project.Prior to having carefully conducted my own cost justification analysis on replacing an end-of-life tank-type hot water heater with a new tankless instantaneous type; then shopping for, choosing, and finally installing a Bosch 2400E heater myself, I had never participated in the alt.home.repair newsgroup. FYI, I subscribe to many newsgroups -- some on an ongoing basis, some on a "let's see what that group is like" basis, and some on an "I need some specific information on a specific subject or topic". The latter is why I have participated in alt.home.repair for the last couple of weeks. I have read much, learned much, and considered much. There are a lot of experienced opinions expressed here in this group. I hope that the tankless vs. tanker water heater discussions will continue unabated. Conserving one's finite bank account, as well as conserving planet earth's finite natural resources are important, and newsgroups such as this one are a great forum for discussing and debating just how to accomplish such conservations.
I do have one closing remark, before I go. Bernardo, you said that
I would like to leave you and others who may read this with what I consider to be important and relevant information. Sometimes, making a decision is 100% about saving money, even if it comes down to saving a single penny over several years or decades. After all, fortunes have been gained and lost over a few pennies per share in the stock market.
However, sometimes there are other reasons to make a decision. For example, making a decision to recycle aluminum cans rather than tossing them in the garbage, even if it means having to carry the cans to someplace other than your kitchen trash can. Or, if you own a dishwasher, forgoing the dry cycle to let the dishes dry naturally with the door cracked open (saves $$ and energy). Or, in the case of one of the recurring topics of this newsgroup, replacing a tank-type water heater (better if it is already worn out) with a tankless model -- even though the initial tankless cost is higher than the tanker replacement cost, knowing that monetary investment and energy payback is in the long term. Granted, tankless heaters might not be the appropriate choice in every situation, but when they are, one should give due consideration to installing one IMHO.
To any newcomers reading this post, please take a few moments to review the many related posts in this thread concerning the storage tank versus the tankless, or "instantaneous" water heater. The original thread name is "rinnai vs rheem tankless", which I changed to "Re: changed to: tank vs. tankless water heater" after it became apparent that the discussion was pretty much focused on just that.
Long life to the tank-type vs. tankless-type hot water heater debate!
-- Maxodyne.
Here you go. Some of these are fairly standard comparisons, but the last one is very detailed and should give you far more information than you ever wanted to know.
On Dec 29 2007, 8:33=A0pm, maxodyne rolled out of bed, bumped his head and then slobbered the following:
You moron, you are comparing the efficiencies to a NEW tankless vs. your "ancient" tank. Why not compare it to a new foam insulated tank. And your use of "ancient" is too much along the Madison Ave. mantra for the tankless hype. Methinks you have an interest maybe.
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