# opinion needed and any fact as well...



## ShtRnsdownhill (Jan 13, 2016)

what set up creates hot water more economically gas usage wise only...a separate hot water heater or a boiler with an indirect hot water tank? on another forum ( not plumbing) they have a debate on which one will use less gas to produce hot water..so any opinions and anything based on fact..


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## OpenSights (Mar 23, 2015)

I can’t answer your primary topic, but you did ask for a fact. The fact is in most parts of the world tomorrow will be Tuesday, some areas will experience rain, some areas will be sunny, some cloudy and some can expect snow. 

I need to be a weatherman!


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## Tango (Jan 13, 2018)

Without looking at my books if I remember correctly aquatubular boiler is better. Ignitubular boiler second.


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## ShtRnsdownhill (Jan 13, 2016)

OpenSights said:


> I can’t answer your primary topic, but you did ask for a fact. The fact is in most parts of the world tomorrow will be Tuesday, some areas will experience rain, some areas will be sunny, some cloudy and some can expect snow.
> 
> I need to be a weatherman!


and today is yesterday tomorrow and tomorrow will be yesterday the day after...


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## OpenSights (Mar 23, 2015)

In ‘00 I left Okinawa and arrived in San Diego the day before!:vs_whistle::surprise:


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## ShtRnsdownhill (Jan 13, 2016)

if your on a fast plane you can have 24 new years...


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## ShtRnsdownhill (Jan 13, 2016)

what we have here is a..............


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## Tango (Jan 13, 2018)

ShtRnsdownhill said:


> what we have here is a..............


................Derailing hid own thread! :biggrin:


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## Toli (Nov 7, 2015)

My opinion-

The amount of energy needed to heat a fixed amount of water from one temperature to another doesn’t change. So if the efficiency of the boiler and tank type heater are the same, the gas consumption will be the same, assuming everything else is the same.


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## Tango (Jan 13, 2018)

Toli said:


> My opinion-
> 
> The amount of energy needed to heat a fixed amount of water from one temperature to another doesn’t change. So if the efficiency of the boiler and tank type heater are the same, the gas consumption will be the same, assuming everything else is the same.


Read my first post, it takes less energy to heat water in a aqua tubular boiler. It's all about surface area/heat exchange/ and efficiency use of combustion.


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## The Dane (Feb 19, 2015)

Tango said:


> Read my first post, it takes less energy to heat water in a aqua tubular boiler. It's all about surface area/heat exchange/ and efficiency use of combustion.


Nope not right. As Toli said, to heat a fixed amount of water to a fixed temperature takes the same fixed amount of energy. Now how much energy you use is a different matter. If let's say for example a gallon of water takes 100 kilojoule to heat up 1 degree Fahrenheit. An 80% efficient tank water heater will use 100 kilojoules of gas or electricity but only 80 Will be transformed to the water so you still need to give it an extra 20 kilojoules before getting the 1gallon up 1 degree Fahrenheit. If you have an on demand water heaters that is 98% efficient you use 100 kilojoules of gas or electricity and 98 is transferred to the water then you only need to give it an extra 2 kilojoules to warm up that gallon 1 degree Fahrenheit.

In all an 80% efficient heater will use 125 kilojoules of energy to heat 1 gallon if water 1 degree Fahrenheit. An 98% efficient heater will only use 102 kilojoules to heat up that same 1 gallon water 1 degree Fahrenheit.

In conclusion if you switched from an 80% efficient heater to an 98% efficient heater you just saved yourself 23 kilojoules heating up the water and therefore used less gas or electricity to get the same amount of hot water.

All numbers are made up and not true numbers.

Sent from my BLN-L24 using Tapatalk


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## Toli (Nov 7, 2015)

Tango said:


> Read my first post, it takes less energy to heat water in a aqua tubular boiler. It's all about surface area/heat exchange/ and efficiency use of combustion.


If the argument is the efficiency of one appliance vs another then ok. 

The original question was which system uses less gas. In my opinion, it’s the same until you figure the appliance efficiency.


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## ShtRnsdownhill (Jan 13, 2016)

Tango said:


> Without looking at my books if I remember correctly aquatubular boiler is better. Ignitubular boiler second.



ok if thats so, then will burning 45000 btus for a standard 50 gallon water heater and burning 1300000 btus in a boiler to make hot water, using those figures as they represent the average size and btus for a standard home, which one at the end of the year will use less NG to make the needed hot water?? I know there are many variables on efficiency of each unit and so on, but the general question is does a unit using almost 3x the btus to heat water indirectly use more or less gas than a unit using 1/3 the btus to make hot water for a year or month at a time??


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## Alan (Jun 18, 2008)

This reminds me of a stupid system I saw. They were using an electric boiler to heat both the domestic hot water and the radiant floor (They only put it on the 2nd floor not in the slab). I can't remember how it was set up, but it seemed horribly inefficient. 

They also had a guest house they didn't want to put a water heater in, so there was a domestic hot water line underground and insulated out to this other building.

Add to the list of other dumb things : 

Building measurements down to 1/32"

Flat roof with scuppers and internal downspout piping that exited the siding about 18" high. It looked like Dr. Octopus when it was done. We get a ridiculous amount of rain in the winter here. Nobody builds flat roofed buildings, save maybe for commercial stuff. There's only one commercial building I know of that has internal downspouts and it is horribly noisy. Can't imagine having that in my house.


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## Alan (Jun 18, 2008)

ShtRnsdownhill said:


> ok if thats so, then will burning 45000 btus for a standard 50 gallon water heater and burning 1300000 btus in a boiler to make hot water, using those figures as they represent the average size and btus for a standard home, which one at the end of the year will use less NG to make the needed hot water?? I know there are many variables on efficiency of each unit and so on, but the general question is does a unit using almost 3x the btus to heat water indirectly use more or less gas than a unit using 1/3 the btus to make hot water for a year or month at a time??


I'm not a physicist but logic dictates to me that if you are using more BTU to heat the same amount of water, given that it takes the exact same energy to heat the exact same amount of water to a desired temperature, then the 130k btu unit is just heating the water faster.

None of that of course takes into account heat loss up the flue piping during heating and at rest, but I assume that these are things figured into the fake efficiency rating numbers.

So if your efficiency rating of your storage tank water heater is the same as the indirect fired tank, then you could assume that the fuel usage would be the same. (I don't know if Indirect heaters have efficiency ratings. I would think the government would be all over that, though.)

IOW can the indirect tank maintain it's temperature for the same amount of time as the 45k btu water heater? Or Vice versa? That would be the question.


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## ShtRnsdownhill (Jan 13, 2016)

Alan said:


> I'm not a physicist but logic dictates to me that if you are using more BTU to heat the same amount of water, given that it takes the exact same energy to heat the exact same amount of water to a desired temperature, then the 130k btu unit is just heating the water faster.
> 
> None of that of course takes into account heat loss up the flue piping during heating and at rest, but I assume that these are things figured into the fake efficiency rating numbers.
> 
> ...



my thoughts are, and im not saying its correct, is that with a boiler with an indirect tank you are first heating the boiler water to now heat the water in the indirect tank, so you would have heat loss up the chimney and in the loops heating the water compared to a stand alone that the flame is directly heating the water with heat loss up the chimney..im just thinking the more steps to get the heat into the final water leads up to more heat loss and you can boil a pot of water on a small stove burner or a huge commercial one, but how much of the excess heat from the commercial one doesnt contribute to heating the water and goes unused, like the boiler having more go up the chimney at 3x the rate than the water heater..I know its splitting hairs and unless you have the 2 systems working side by side with the efficiency parameters laid out this can be debated for weeks..I just asked to see if anyone had their personal opinion on it, not to beat it to death..:smile:


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## Alan (Jun 18, 2008)

ShtRnsdownhill said:


> my thoughts are, and im not saying its correct, is that with a boiler with an indirect tank you are first heating the boiler water to now heat the water in the indirect tank, so you would have heat loss up the chimney and in the loops heating the water compared to a stand alone that the flame is directly heating the water with heat loss up the chimney..im just thinking the more steps to get the heat into the final water leads up to more heat loss and you can boil a pot of water on a small stove burner or a huge commercial one, but how much of the excess heat from the commercial one doesnt contribute to heating the water and goes unused, like the boiler having more go up the chimney at 3x the rate than the water heater..I know its splitting hairs and unless you have the 2 systems working side by side with the efficiency parameters laid out this can be debated for weeks..I just asked to see if anyone had their personal opinion on it, not to beat it to death..:smile:












In that case I suspect it would be the average efficiency of the boiler + the indirect tank. I don't know if heat loss through the chimney is factored into fake efficiency numbers but I would think so, otherwise they are missing a huge part of energy usage.


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## GAN (Jul 10, 2012)

Lets not forget the bottom line. Overall your using to different device if a boiler then separate WH.

2 devices, more initial cost, maintenance, plus sperate energy uses. All that taken into account. You breaking down total cost or just partial costs.

Much of what is being seen in wind energy. It takes so much energy to make the devices, transport them, install them and maintain them the saving are a bit of a falsity.:whistling2:


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## skoronesa (Oct 27, 2015)

Tango said:


> Read my first post, it takes less energy to heat water in a aqua tubular boiler. It's all about surface area/heat exchange/ and efficiency use of combustion.



He said if the efficiency is the same. At the very least with a boiler and indirect you have pipes between them which may or may not be well insulated and will lose heat so that's something I guess. Also the boiler and the water heater together have much more surface area than the heater by itself so they will lose more heat to the air.



If I had the space I would go with an 80 or 100 gallon propane water heater and run a loop through a coil on my furnace for heat. My house isn't that large so I would still have more than enough btus to shower as well. Probably still run a 30 gallon electric in the summer though.


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## skoronesa (Oct 27, 2015)

I think you really need to pick out specific models so some of the more motivated heating guys here can run the numbers and figure out heat loss/efficiency. You ask for a factual response but all we can give you without more specifics is opinion.


There is a very factual, number answer to which will be more eficient, we just need to know what numbers to put into our equations.


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## skoronesa (Oct 27, 2015)

Also, did you know that electric water heaters are 100% efficient?


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## Plumbus (Aug 4, 2008)

skoronesa said:


> Also, did you know that electric water heaters are 100% efficient?


An electric heater run by a solar electric panel would be optimal, at least while the sun shines.
A condensing on demand (tanlless) heater with the fixtures supplied within 10' feet would be the most efficient system I could think of. They are often mounted in the bathroom with the kitchen sink on the other side of the wall. The short runs would negate the need for circulating the water. It's the way I've seen the technology used in Europe and as I've heard in Japan.
Supplying a whole house, as is common in the US, I'd say efficiency is not so easy or as big a priority.


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