Indirect vs.Tankless efficiency?

Eric L._2

my main is 1 1/2". Yup got myself a steam system and I was all set to convert to HW but at least for know I'm just going to get a steam guy in here to give the system a good looking over and make sure I'm getting the most out of my system.

Since we are comparing equipment , would there be any benefit to changing out my 8 year old beckett burner with a Riello or some such? Thanks again guys.

Eric

Eric L._2

Indirect vs.Tankless efficiency?

What makes an indirect more efficient than a tankless? On average how much more efficient do you think? I make DHW for myself and two other apts. with an WM SGO-7 2.00gph and its getting really expensive to make hot water. Thanks for your time and experience.

Eric

Wayco Wayne_2

The definitive answer is....

It depends. It depends on the efficiency of your boiler. It depends on whether you have a big enough chimney and/or gas line to run the tankless big enough to cover your HW demand, and what the installation cost of said items might add up to vs the returns on savings. An indirect has almost no standby losses, since it is insulated on all sides. A tankless has very little standby losses because it only runs when there is a demand for hot water. If you have a high eff. boiler the combustion efficiency can transfer over to your hot water. Anyone who has a 90% eff boiler and does not have an indirect is missing out on some significant savings. WW

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kpc_11

interesting.

Wayne is correct...however in your case you have 2 apts plus you and you use the steam boiler to make hot water...year 'round...I would suggetst 3-40 gallon electric water heaters....each tapped into its own apt.eletric service (presuming that every apt has its own service)I usually tell apt. owners to do this because tenants don't conserve what they don't pay for. This way you don't have to pay for someone elses 30 min shower...electric water heaters are very easy to install compared to gas. kpc

jp_2

not correct

on-demands are more efficient than indirects.

a 40 gallon indirect will waste approx 4 million btu's per year waiting to be use; on-demand Zero.

this equals about 6 gallons of hot water a day. on demands win over indirects where water usage is low.

ALH_4

Instantaneous vs. Tank

A mod/con could negate the indirect tank's standby loss in comparison with an instantaneous. Where water use is low, a small tank-type water heater will provide a more consistent temperature at the tap.

For low water use situations, I see it as a wash, in terms of energy. As hot water use goes up, the indirect w/mod-con looks better. Of course, a SDHW system looks even better from an energy use standpoint.

Derheatmeister

I Stand with WW! Especially of one's using a condensing boiler Like the Triangle in conjunction with the Domestic Expansion kit from them ,that allows you to program the boiler to condense at Dom H2O production.!Even better jet Combine this with a Double Coil Tank and Solar on a "Timeout"for Boiler Production ,And now we are Rocking! did it, Many times, and Lowered lots of Happy customers Bills !but again ,This system most be Thought out before one takes a torch in you hand(Design by solder)I've said it before: Inst. Waterheater have there place but one must look very hard to find it ! Richard from Heatmeister. HM

Uni R_2

That's seems a bit high...

That's a bit high compared to what the manufacturers are claiming. I thought most claimed only about ½°F per hour and your calcs would require over 1°F per hour drop. That said, a modcon can condense through most of the DHW cycle so at 60 gallons per household it would save a couple of million BTUs over the year compared to a less efficient tankless.

Take in the fact the over half the indirect's standby losses occur during the heating season around here and it tips the balance for an indirect. To make it more apples to apples, I wonder what the standby BTU losses are from the venting on a tankless? Probably not much, but they should probably be factored in to make it fair. Anyone ever take readings around one from outside during the winter when the tankless is idle?

Eric L._2

Indirect vs.Tankless efficiency?

Well its not exactly what I wanted to hear but I guess it makes sense. I already bought the tank so I'm stuck with it. That might not necessarily prevent me from getting an instant heater for the other apartments. Thanks for all your time.

Eric L.

Eric L._2

Indirect vs.Tankless efficiency?

Well its not exactly what I wanted to hear but I guess it makes sense. I already bought the tank so I'm stuck with it. That might not necessarily prevent me from getting an instant heater for the other apartments. Thanks for all your time.

Eric L.

jp_2

never try to remember what can be

looked up.

you are right Uni R, redoing it looks more like 1.4 million Btu's. thats what I get for not checking with what I think I remember.... still come out to 6 gallons a day in lost heat.

Steamhead (in transit)

Eric has a STEAM system

the water version of the W-M Gold Oil would be the WGO- so he can't use a mod-con boiler.

If sub-metering hot water is not allowed, individual heaters may be the only way to get tenants to pay for their hot water usage. But I hate to use direct-fired tanks that burn out in 6-8 years.

Is the gas main big enough for a fleet of instantaneous heaters? Will the chimney handle them?

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Wayco Wayne_2

JP You should double check your facts.

They may have been given to you by a Tankless salesman. A Tri Tube Smart tank has a stanby loss os 2 degrees F in a 24 hour period. That aint much. WW

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Derheatmeister

Eric,IF your "Service" into the building has enough amps then you can also look into Electric on demand, Check Stiebel Eltron i have one installed in conjunction with a solar preheated tank. Even if there is no solar gain the tank sits at close to room temp and the Delta tee to overcome is not what great of a barrier. In other words it works great!You may be even able to hook these units to the individual panels Thrus having each user pay for there own Half hr shower! Oh yes and there is a way to use the condensate of your boiler tru a heatexcharger to make DHW. as per your new post you may start a new topic and get better results. Good luck HM.

jp_2

wayco, you should double check your facts

as far as the triangle tube smart series, their literature states less than 1F per hour. remember, its only 2 inches of foam around the tank.

so, now we are even!!!

Wayco Wayne_2

Sorry..

Even we are. WW

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realolman

I have a Burnham v73 with a tankless coil and a single family, and it took 2 gal of oil a day to keep it going over the summer for nothing but DHW. Once I found that out it didn't take long to put in an electric water heater.

I truthfully don't know what it would do in the winter, but I suspect you're getting killed providing hot water to tenants this way.

Edited... slow mind and typing.

tim smith

Another reply re: indirect consumption

You also have to factor in the pump and boiler kw useage. This will have a definite factor. With that said, I am a fan of indirects vs demand heaters except when the boiler goes down, both heat and dhw are down, which it will happen. With the dual heaters at least you are most likely going to have one or the other. Just a thought. Tim
Regarding tank standby loss, thats only $2 a month, not much.

Derheatmeister

realolman what kind of indirect was it and how old was it? was there a well involved?

realolman

it wasn't

an indirect. It was a coil inside the boiler, similar to what the OP has in his steam boiler. It's from about '86 I guess. I have a well.

I sticked the oil tank and it cost a lot more in oil than it did to heat DHW with electricity in the summer... winter I don't know.

Derheatmeister

Realolman, Oh yes that will explain it if your exchanger is "Isolating" it self from the boiler it becomes VERY inefficient!

carragebolt

If the question is indirect vs tankless coil then it is a no brainer.tankless coils should be outlawed.Keeping the boiler at 200 deg 24/7 incase someone wants hot water is like keeping your car running 24/7 so it is warmed up when you get in it. 99.999% of my inssufficient hot water calls are tankless coils.We always have to walk the line between overheating the boiler and getting enough hot water.

realolman

As far as

hot water goes, it worked swell in that respect. You could've stood under the shower till the well or the oil tank went dry.

But it used too much oil, at least in the summer. I think most everything just went up the chimney or in the cellar. I don't know how well it did in the winter when you needed the boiler anyway.

DerHeatmeister, what do you mean "isolating" itself?

Derheatmeister

Isolating as in scale buildup especially if you are on a well. Once you have scale the exchanger does not work as good and yes you must read caragebolt's post as well.