advice on tank vs tankless

Constantin

... yet another instance where regulatory standards-setting bodies introduce confusion into the market instead of sensible standards. But I guess 109% efficiency sounds better than 98%, so that's preferable... :-P

IE

need to update heating system-

Hello all, TIA for any advice to follow (and feel free to cybersmack me if I seem to be completely confused).. I recently moved into a house that has a very old heating/ hot water system... The heat for the house is currently forced air fired from an ancient oil fired sunbeam furnace that is the size of a small car (perhaps it was converted from coal?), the hot water for the house is a big 50 gallon oil fired water heater which is in also pretty poor shape.. Together the two consume oil like a Kuwaiti refinery fire from the 90's ... I would like to update both systems- right now I'm just trying to learn sd much as I can about options... Althogh I live alone- the house has 2 full baths and I'd like to update with the idea of trying to be more eco friendly, better efficiencey, and keeping a family in mind for the future..
The house has no gas lines so I'm guessing LP would be the fuel of choice... The water is from a well btw (I don't know if that makes any difference) From what I've been reading a tankless water heater would seem to make sense as my current hot water use is pretty much one shower/ washing hands a few times, doing dishes by hand/ etc a day, but being tankless it would be able to handle a higher demand as needed... other advantages to the new breed of tankless would be being able to direct vent outside (I would like to have the main chimney re lined for use with a wood stove in the living room), as well as requiring less basement real estate. For tankless heaters I've heard good things about buderus, munchkin, rennai (sp?) , and Takagi(sp?) , but at say Home Depot I see brands like Paloma and Bosch... I'm new to all of this so I'm not sure why any of the above brands would be a beter bet...
Right now due to financial constraints- I'm thinking of switching to the tankless heater just to stop wasting insane ammounts of money, and then eventually switching from the forced air to some form of hydronic heat (for now I just keep the heat pretty low) - radiant would be nice but I don't have any idea what installs run... If I plan on eventually switching over to some kind of hydro heating radiant/baseboard/radiators/ whatever- Is it still OK to use a tankless for regular hot water showers & such or would the heating system draw generally need to have a tank? I know I've asked a ton of questions, but I will be grateful for any advice given...

thanks again - IE

John_82

Dude, propane is never the way to go. Once they get that bottle in your yard, they can charge you whatever they want. Plus oil has a 140,000 btu value vs. 90,000 btu's w/ propane. So no matter how you cut it, oil gives you more bang for the buck! As far as the tankless domestic water heaters go, I've heard only negatives. For you, and only you it would be fine. For 2 or more Americans, it ain't gonna work. These heaters are from europe, where you take a 2 minute shower twice a week. hardley the average American water usage. In my opinion, if your planning a family, stay away from any tankless. If your planning a hydrinic system, go hydro-air. You already have the duct work in place and you have the ability to put in some radiant too. Use a oil boiler, with outdoor reset and an indirect heater..... May I suggest a Buderus package of boiler, r2107 reset control and one of there vertical indirects... Nice!!! That would be Cadillac!!

chapchap70_2

Furnace first

I'm not there so I can't tell you how bad the water heater is. I would think that your furnace wastes more energy than the water heater though.

I know you said your finances are tight so I am guessing you can't plunk down thousands of dollars to have a new heating system installed. Here's what I think you should do. Find a contractor that is willing to finance you or get a home improvement loan. Your monthly bills wasting oil with the old system will not be much less than paying monthly for a new heating system with maybe a 60% reduction on energy costs. What is the condition of your oil tank?

As far as comparing heating oil vs. gas: Remember that when comparing pricing between the two fuels that the price per gallon for oil is not the same as the price per therm of gas. I'm not sure of the units of LP though. I think LP is usually more expensive than natural gas. The BTU content of a gallon of oil is about 140,000. The BTU content of a therm of gas is 100,000. So when comparing prices, $2.24 per gallon of oil is about the same as $1.60 per therm of gas.

If you could afford the monthly payments, look into a hydro air system. That is a boiler that delivers hot water to an air handler. The air handler blows the hot air which is made from the hot water going through coils into the duct work. You can then also use your boiler to heat your domestic water in a variety of ways. Pick one.

As far as the tankless water heaters like Rinnai, these are gas units. I believe these units are efficient but you may run out of hot water if you have a large demand need at once. I don't think these can handle high flow rates. I do not think oil has anything that is equivalent.

I think that the most efficient oil boiler for making hot water is the System 2000. www.system2000.com The boiler sits cold when not in use and when there is a need for hot water, it first comes from a storage tank and the boiler heats up more water before you would run out of hot water from the storage tank. More hot water would be available with this setup than with an on demand tankless heater. The boiler is very efficient for heating as well. You can also choose this boiler if you prefer gas. The boiler would be the same in this instance but the burner is different.

As far as relining your chimney so you can burn wood, this does nothing for your heating system because you need a different flue for your heating equipment than your fireplace. You can reline both flues or else you can vent through the wall. This is called power venting. This is probably cheaper than relining the chimney but there are limitations with this; odor and discoloration for example if your boiler isn't working just right.

I hope this information is useful.

Mike E_2

Your statements that "Propane is never the way to go" and "oil gives you more bang for the buck" are not always true.
There's alot more to look at than propane has 91,600 BTU/gal while oil has 140,000 BTU/gal.

I have neighbors that are on propane and they are locked in at $1.40/gal. So far this year, I have paid $2.47, $2.23, and $2.19/gal for an average of $2.30.

If you work out the price per 100,000 BTU in my area -
Propane boiler at 98% efficiency - $1.30
Oil boiler at 88% efficiency - $1.43

Also note that that the 98% efficiency for the propane doesn't take into account the extra heat you get from the latent heat of condensation. Viessmann says their Vitodens is 109% efficient. 98% combustion efficiency, and and extra 11% from flue gas condensation. I don't have any personal numbers to prove this as I don't yet have a condensing boiler, but other people on this board have started to post findings showing this.


After saying all that, I personally do not like propane all that much. The fact that it is heavier than air will cause leaking propane to start pooling on the floor, and if it is in a basement or crawlspace, that could be a big problem.
Also, if you don't buy your own tank so that you can price shop, you are at the mercy of one company. You also have to locate a big white tank somwhere on your property.

If you decide on oil, get a 3-pass boiler such as a Buderus, or the Burnham MPO, Weil-Mclain Ultra Oil, Crown CT series, and others. These are all around 88% efficient. For your DHW needs, get an indirect water heater. For the time being, use hydro-air until you can install some form of radiant, or panel radiators, or baseboard.

If you decide on propane, spend the extra money for a condensing boiler. There are many of these to choose from - Buderus GB142, Weil-Mclain Ultra, Munchkin, Lochinvar Knight, Trinity, and others.

Scott Gregg

Oil vs LP and Tankless

JP, there is a lot out there on tankless you really need to see. If you have never heard anything good about them, you are not looking in the right place. I think you should learn more about them. These are great machines that do what they say and millions of Americans now have them in their homes and are enjoying them.

Start here:

http://profitableplumbing.com/_wsn/page5.html

All that said, I think ChapChap is right. This is more of an oil v/s LP question. With oil to your home already, I’d look into a good contractor with a great reputation and get some local recommendations on a good oil system. You already have a great fuel source and you would be money ahead to upgrade with some of today’s new oil equipment. A new Hallmark Furnace with a Bock 51E (The best oil fired tank water heater) sitting next to it would make a warm home and probably save oil. (I don’t know anything about your system from here) You would have loads of hot water and nice solution without a complete fuel changout to go with it.

If you are going to go hydronic soon anyway, start planning it now. It would be a shame to put in new equipment only to rip it out in a year or two.

Good luck.

Joe Brix

LP is nice

if you can buy your own 500 gal tank and burry it, not cheap, but allows you to shop for LP. If you has an oil tank in the basement that's in good shape and a chimney that's not falling apart, I'd stick with oil. Get an indirect tank that will probably only call for heating only a few times a day, but have a good store of hot water whenever you need it. Don't count on a tankless being able to make hot water for more then one person at a time.
Stick with hydro-air and think about radiant floors down the road when you renovate rooms.

Scott Gregg

Joe

Noritz tankless heaters easily handle 3 showers at the same time with unlimited hot water! Rinnai, and Takagi also have models that can do this. See the link above.

6-8GPM for just one unit. How much hot water do you need? A tankless coil in a boiler only gives about 4.

Joe Brix

true scott

but those models are not the $600 Tagaki Jr. or Bosch units the customers see at the home centers. From what I've seen, those high output units are as much as a boiler and indirect.

chapchap70_2

109% efficiency? Neat trick

Most oil burners have a 99+% combustion efficiency.

I don't know how to figure gas steady state efficiencies but with oil, 109% would look something like this:

3500 degree fire multiplied by 1.09 equals 3815 degrees
3500-3815= -315 degree flue gas going through the smoke pipe and up the chimney. Add 60 degrees for room temperature and that brings the flue gas temperature up to -255 degrees F

Put a heat exchanger around that smoke pipe and bring the air into the duct work and you'd have one mean A/C system.

Scott Gregg

Good things cost money

Noritz N-063S Retail price is $899. (listed on their web site) Typical flow rates range from about 5 to 6.3 GPM (300-378 gallons per hour)

That's a pretty good investment. Compare that to any boiler/indirect for cost and DHW delivery.

Yes the professional grade equipment cost more than the "Stuff" the Big box stores sell. That's also why the big boxes get a very high return rate on those machines. People think they can save some money and do the same job.

A good tankless system is worth the proper investment. Kind of like radiant though, it won't be for everyone.

Ron Schroeder

109% efficiency??

Be carefull about comparing condensing boiler efficiency from european boilers to AFUE. Make sure you are getting an AFUE rating rather than the european efficiency standard. The european measurement standard is entirely different.

The european standard for 100% is the theoretical fuel energy content and efficiency WITHOUT condensing. The american standard for 100% is the theoretical fuel energy content and efficiency INCLUDING condensing.

Mike E_2

It's not a trick. It depends on what you define as 100% efficient. What most people define as 100% efficient is based only on sensible heat.

While oil BURNERS may have 99% combustion efficiency, oil BOILERS aren't that high for heat transfer efficiency.

Non-condensing oil boilers have at best high 80's%
Buderus G115 - 86.8%
Burnham MPO - 87%


Your calculations are treating everything as sensible heat. Combustion analyzers also only measure sensible heat.

Latent heat is a source of "free" heat that you can recover before it goes up the chimney.


Since I don't have any knowledge of condensing oil boilers yet, I'm going to use natural gas as an example.

The theoretical maximum of condensate produced from burning a therm of natural gas is 1.127 gal. The heat you gain from condensing water vapor is 600 calories/gram. Multiply by .00397 to get BTU = 2.382BTU/gram

1 gallon of water = 8.3lb. Multiply by 453.59 to get grams = 3764.797 grams/gal water.

3764.797 grams * 2.382 BTU = 8967.75 BTU/gal of condensate.

1.127 gal/therm * 8967.75 BTU = 10,106.65 BTU of "free" heat.


Now remember that this is the theoretical maximum. In practice, condensate production is less than that.

Mike E_2

It's not a trick. It depends on what you define as 100% efficient. What most people define as 100% efficient is based only on sensible heat.

While oil BURNERS may have 99% combustion efficiency, oil BOILERS aren't that high for heat transfer efficiency.
Non-condensing oil boilers have at best high 80's%
Buderus G115 - 86.8%
Burnham MPO - 87%

> 3500 degree

> fire multiplied by 1.09 equals 3815 degrees

> 3500-3815= -315 degree flue gas going through the

> smoke pipe and up the chimney. Add 60 degrees

> for room temperature and that brings the flue gas

> temperature up to -255 degrees F

Your calculations are treating everything as sensible heat.

Latent heat is a source of "free" heat that you can recover before it goes up the chimney.

Since I don't have any knowledge of condensing oil boilers yet, I'm going to use natural gas as an example.

The theoretical maximum of condensate produced from burning a therm of natural gas is 1.127 gal. The heat you gain from condensing water vapor is 600 calories/gram. Multiply by .00397 to get BTU = 2.382BTU/gram

1 gallon of water = 8.3lb. Multiply by 453.59 to get grams = 3764.797 grams/gal water.

3764.797 grams * 2.382 BTU = 8967.75 BTU/gal of condensate.

1.127 gal/therm * 8967.75 BTU = 10,106.65 BTU of "free" heat.


So you pay for 100,000 BTU of heat, but you are capable of gettting 110,106.5 BTU total.


Now remember that this is the theoretical maximum. In practice, condensate production is less than that.

chapchap70_2

Good grief

Do you think IE would be confused if he reads all this efficiency mumbo jumbo?

"Viessmann says their Vitodens is 109% efficient. 98% combustion efficiency, and and extra 11% from flue gas condensation."

This statement makes no sense. Combustion efficiency is the percent of fuel that is consumed by the burner. How can anything having to do with flue gas enter in to this? This statement mixes combustion efficiency with steady state efficiency or what you called heat transfer efficiency.

My point was that if you have 60 degree air going into a heating appliance, you will not have less than 60 degree air coming out of the appliance.

I would think that if there is 10000 BTUs available from condensing, there are only 90000 available from not condensing.

IE

First off I want to thank everyone for talking the time to help out with all the advice given! You guys have definitely helped me to understand some of the efficiency rating stuff much better now... most important- you've helped me to understad how much I don't know- but now have a clearer idea of the questions I need to start asking/ looking into when I find a contractor in my area..I particularly liked the idea of using something like tthe GB142 (even though they are pricey- from what I've been reading it seems to be a worthwhile investment)and possibly doing hydro air using the existing ductwork for now until I can afford to do radiant...

chapchap70_2

Using this logic...

IE would be better served by taking a non leaking oil fired boiler from the curb and maybe a new burner than buying a Viessmann Vitodens. It would be more than 99% efficient where the Vitodens is only up to 98% efficient according to their web site. (94% AFUE)

Kevin__Flynn

European Efficiency

aemeeich,

Be careful, you are comparing the higher heating value efficiency used in the European market for the Vitodens at 98 + 11 to the lower heating value efficiency used in the US market for the Buderus/Burnham.

As you've stated, in Europe efficiency is based soley on sensible heat (a system established before it was realized that any latent heat could be extracted). Without being able to extract latent heat from flue gasses the highest efficiency you could ever hope to achieve was 88%-89%. So this was considered 100%

So to compare apples to apples, it would either be Vitodens at 94% compared to MPO/G115 at 87% in the US or Vitodens at 106% compared to MPO/G115 at 97%-98% in Europe. (I might be a point or two off either way for the European standard)

As far as the Oil/LP debate, in my area in most cases oil is considerably less expensive than LP, even comparing the best possible efficiencies of each when being installed in identical distribution systems. However, what we are finding is that new houses have less and less space available for mechanical equipment. So sometimes the decision is made based on the fact that a small wall mounted propane boiler and no oil tank will fit when the alternative will not.


Kevin Flynn

Constantin

I was being sarcastic...

.... if that wasn't already perfectly clear. Not that the AFUE isn't without its flaws either. I wish better resources were available to homeowner and contractor alike to make purchasing decisions a bit more objective...

For example, the AFUE of a Vitodens is closer to 98% once the return water temperatures approach the temperatures that I see in my RFH system. As we speak, Ms. Vitola is sending 92°F water to the 4-way valve while 77°F water is returning... and its 32°F outside...