running non-condensing boiler at lower temp - does it make it more efficeint?

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Old 12-28-11, 07:09 AM
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Lightbulb running non-condensing boiler at lower temp - does it make it more efficeint?

Recently I started a topic on this forum regarding balancing temperatures in two different rooms on the same zone. I learned a lot and folks here were very helpful. During the discussion it turned out that my old cast iron boiler has an aquastat set hit Ė at 200F. Many, including a very helpful NJTrooper suggested turning it down to 180F. One of the reasons that was mentioned was that the boiler runs more efficient and saves money. While I want to return it to the design 180F, Iím curious about the idea of the boiler running more efficiently at lower tempÖ

I decided to do some research since it wasnít clear to me why it would be more efficient. I read some technical papers online and it seems that it makes a lot of sense for condensing boilers Ė you extract all this latent energy when the water does the phase shift at lower temps (~130F) and that boosts the efficiency by 10-12%. Huge, as long as you stay in the condensing range.

For old cast iron boilers things are not so straight forward. The only reason to have higher efficiency at lower water temp is higher difference between the hot gases (result of combustion ~750F) and colder exchanged (160F-200F). The higher difference in T results in more efficient heat transfer which adds about 1% to overall efficiency according to one paper. While 1% is still an increase, what I find strange is no mentioning of decrease of efficiency when heat is transferred from the heating element (150F-190F) to the air (70F). Lower temp difference here will result in less efficiency and drop in the difference between temperatures here is more dramatic in relative terms (%%) so I would expect greater loss of efficiency here than gain in the boiler.

But letís say we keep this 1% of increase in efficiency due to lower temp. The circulating pump will have to work longer to deliver the same BTUs at lower temperature. So we will have electricity cost here decreasing the overall efficiency of the system even further.

So, am I missing something here? Can someone either provide some relevant information to back up the idea or point me at some technical papers? With some number is possible. I do see mentioning of Ērunning at lower temp saves gasĒ on the forums, but not many explanations why and how.

Of course, there are other aspects to running the boiler cooler Ė possibly longer lifespan due to lower stress to the system, less noise due to less pipe expansion/contraction, ect. But right now Iím curious about the relationship between the water temp and the efficiency.

Thank you
 
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Old 12-28-11, 07:54 AM
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I've wondered about the very same things myself. I'll be interested to see the replies to your post. I know one of the things mentioned frequently is stand-by losses.
Steve
 
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Old 12-28-11, 08:13 AM
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I don't believe I said that the 'boiler runs more efficient'. I did say that it would save some fuel. I suppose that you could call this ' fuel efficiency ' if you wanted to.

Here are some of the definitions:

1. the state or quality of being efficient; competency in performance.

2. accomplishment of or ability to accomplish a job with a minimum expenditure of time and effort: The assembly line increased industry's efficiency.

3. the ratio of the work done or energy developed by a machine, engine, etc., to the energy supplied to it, usually expressed as a percentage.
I don't want to get into a huge discussion of the various ways efficiency can be defined, so I'm going to try an analogy...

═══════════════════════════════════════════════════════════════════

Let's say you're making a cup of tea. You heat the water to say 180... drop in the tea bag and some time later you have a cup of tea... it cost you x amount of fuel to heat that water, and you have a cup of tea.

Heat the water to 200 and do the same. You still have a cup of tea, but it cost you more fuel to brew that same cup of tea.

It may have taken a few seconds longer to brew at the lower temp, but the end result is the same.

═══════════════════════════════════════════════════════════════════

The higher difference in T results in more efficient heat transfer which adds about 1% to overall efficiency according to one paper.
Could you provide a link to that paper?

I don't understand how the term 'efficiency' could be applied to this... wouldn't this only affect the RATE at which the heat was transferred? Wouldn't it still require the same amount of WORK to transfer the BTU from one medium to another?

what I find strange is no mentioning of decrease of efficiency when heat is transferred from the heating element (150F-190F) to the air (70F). Lower temp difference here will result in less efficiency and drop in the difference between temperatures here is more dramatic in relative terms (%%) so I would expect greater loss of efficiency here than gain in the boiler.
There is no LOSS of efficiency here... there are charts that will show the BTUH output of fin-tube baseboard vs. entering water temperature. Of course there is less BTU output at lower temperatures, but no LOSS. The BTU that are not extracted just continue to flow around the system until they too are extracted. The efficiency does not change.

The circulating pump will have to work longer to deliver the same BTUs at lower temperature. So we will have electricity cost here decreasing the overall efficiency of the system even further.
True, but don't confuse 'cost of operation' with efficiency. Semantically they are different terms.

It would be interesting though to take some empirical measurements to determine how much longer the pump would have to run in order to reach the goal of heating the space to setpoint.

Don't forget that the only LOSS from running a pump is that which goes into making heat in the motor. The energy which is transferred to the water by moving it isn't 'lost'. Actually, the HEAT from the motor isn't 'lost' either! It also adds to the heat in the home.

The answer to this dilemma would be to use a more efficient pump! One which does the same amount of WORK with less energy applied.

═══════════════════════════════════════════════════════════════════

A couple more points that seem to be relevant:

The hotter the boiler runs, the higher the STANDBY LOSSES. [I see that Steve beat me to this point! ]
There is going to be more heat 'lost' to the surrounding area if the boiler is left standing by at a higher temperature... but again, these aren't really 'losses' at all if this heat is transferred to the home.
Also, one must account for the heat lost in the combustion process. The hotter the boiler gets, the hotter the flue gases get, so part of the savings comes to play in this fact.
 

Last edited by NJT; 12-28-11 at 08:44 AM.
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Old 12-28-11, 08:39 AM
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Hello,
I've read it in a number of places, that for every 3 degrees of boiler temperature reduction, 1% of fuel saving can be expected.
Sorry no links.

I gernerally keep my boiler high limit at 170. It is hot enough to do the job most of the time.
When it gets really cold, 10 or below for days on end and windy, i usually turn it up to 180-185, because my first floor doesn't quite have enough excess radiation, to come back from a 2-4 degree setback fast enough. We need the set back because mom (94) is usually cold under 73-74+ durring the day, but likes to sleep at 70-71, or less.

Peter
 
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Old 12-28-11, 08:40 AM
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condensing boilers Ė you extract all this latent energy when the water does the phase shift at lower temps (~130F)
The water in the FLUE GASES to be a bit more precise.
 
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Old 12-28-11, 09:20 AM
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NJTrooper,
My post was in no way directed at you or what you said in one of my previous post Ė it just made me think, hence this post. I respect your knowledge and experience, Iím just trying to understand things better for my own sake. So donít look at this as me being defensive or argumentative.

In order not to bog down in the definitions, letís talk about if it would save you money to run colder..

I donít agree with the cup of tea example. The tea water represents the water in the system and if the objective is to heat that water to either 180 or 200 then there is no doubt it will take less energy to heat it to 180. The objective is however to heat something else with that water, so that part is missing from your example.

The higher difference in T results in more efficient heat transfer which adds about 1% to overall efficiency according to one paper.
Could you provide a link to that paper?

http://www.riversidehydronics.com/pd...or%20reset.pdf

from the paper:
Itís easier to transfer heat when the difference in temperature between the heating medium and
the medium to be heated is larger. Compared to the average temperature of the products of combustion
in a boiler (letís assume 750įF), a 20 degrees difference in entering water temperature may seem insignificant, but it can affect boiler efficiency by a full percentage point. The higher the efficiency of the
boiler, the less fuel used to heat a given amount of water and the lower the fuel bills. So operating the
boiler loop at lower temperatures, when possible, saves money.
I don't understand how the term 'efficiency' could be applied to this... wouldn't this only affect the RATE at which the heat was transferred? Wouldn't it still require the same amount of WORK to transfer the BTU from one medium to another?
as you can see they are talking about efficiency of the heat transfer with a higher differences in temperatures. The more the difference is the better the heat is transferred from the hot gases in the boiler to the air in the room. The same way the solar systems are designed to run cold and fast Ė the colder the water in the loop the better it absorbs sunís energy.
There is no LOSS of efficiency here... there are charts that will show the BTUH output of fin-tube baseboard vs. entering water temperature. Of course there is less BTU output at lower temperatures, but no LOSS. The BTU that are not extracted just continue to flow around the system until they too are extracted. The efficiency does not change.
This is the same process as in the boiler. If we agree that the heat is better extracted at higher temperature differences in the boiler the same should apply here. you say ĒThe BTU that are not extracted just continue to flow around the system until they too are extractedĒ Ė donít you think that this is a sign of inefficiency? Instead of being extracted, the BTUs have to be moved around, get lost in the walls and other parasitic ways? Wouldnít it better to have them extracted and have the boiler heat up colder water at higher efficiency? Since the temp delta will be higher?

The answer to this dilemma would be to use a more efficient pump! One which does the same amount of WORK with less energy applied.
This is not the answer to my dilemma - my dilemma is to understand where the savings are coming from when running at colder temp. for the same non-condensing boiler.

The hotter the boiler runs, the higher the STANDBY LOSSES.
I agree with you here, this a valid argument. However I want to use this argument for something I said earlier in this post Ė the standby losses are higher because the temp difference is higher between hot water and ambient air. So here is another proof that hither temp delta results in better heat extraction.

The hotter the boiler gets, the hotter the flue gases get, so part of the savings comes to play in this fact
Can you elaborate on this? why would hotter flue gases result in less savings? More heat escaping thru the chimney?
condensing boilers Ė you extract all this latent energy when the water does the phase shift at lower temps (~130F)
The water in the FLUE GASES to be a bit more precise.
Yes, the flue gases, sorry if it read differently in my post. But again, weíre talking about not condensing boilers.
 
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Old 12-28-11, 09:56 AM
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i have to admit, there must be something to support the savings with colder water.

otherwise not condensing boilers like burnham es2 wouldn't have ODR capabilities.. but do they only really go for elusive 1-2% gain?
 
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Old 12-28-11, 02:18 PM
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My understanding of why it saves fuel to heat a building by reducing the temperature of the medium that delivers the btus. from the appliance to the zone weather it is air or hot water is : When the water in the radiators is 180f the air being heated is raised to a high temperature and since rads are on the outside walls and under windows these surfaces are the coolest in the room and since heat travels to cold and the greater this difference the faster the heat btus travels, therefor there is a greater heat loss from the room.Also since room air is continually being exchanged from inside to outside, the lower the air temperature being expelled the less btus being lost.I reduced the air temperature of the hot air furnace in a home i once owned from 150f to 90f coming up the registers and saw a reduction in fuel oil consumption of approximately 2000 liters and a increase in comfort .
 
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Old 12-28-11, 02:39 PM
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saves, so basically what you're saying is that with increased temperature the efficiency of the heating element to air transfer is improved, but also parasitic loss is improved as well. and since parasitic loss is between the heating element and the wall that is colder than the air there is more loss there than between the element and the air?

i would incline to agree that there could be some merit to it.

but i still feel that there is something else that we're missing...
 
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Old 12-28-11, 02:57 PM
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My post was in no way directed at you or what you said in one of my previous post .... So donít look at this as me being defensive or argumentative.
No, of course not... I hope my response didn't make you feel I took it that way... no problem! I like discussing this stuff too, in case it hasn't been obvious!

The objective is however to heat something else with that water, so that part is missing from your example.
Probably because we didn't DRINK the tea! Yes, the analogy was rather simplistic, but I think it does fit... the goal was to make a cup of tea, and that we did in both cases... the end result was the same. In case of heating, the end result will be the same, the home will still get heated. It may take a few minutes longer to satisfy the thermostat, but as long as there's enough radiation in the home, satisfy it will.

Itís easier to transfer heat when the difference in temperature between the heating medium and the medium to be heated is larger.
I disagree with 'easier'. I would agree with FASTER.

I will read the entire article later, but I don't think I agree that it actually effects 'boiler efficiency' in the way that they claim. It may be because they are simplifying their statements... or they may not understand that COMBUSTION EFFICIENCY is not the same as 'boiler efficiency'. If by 'boiler efficiency' they mean that there is improved heat transfer... i.e. more heat into the water, and less up the chimney, that's sort of impossible. That efficiency is determined by the physical design of the boiler.

Perhaps they don't realize that there is a direct, proportional relationship between the flue gas temperature and the water temperature? If one uses the formulas for 'combustion efficiency' (or a 'fire finder' slide rule), it's obvious immediately that cooler flue gas causes the combustion efficiency to increase. Maybe that's what they are talking about?

The more the difference is the better the heat is transferred
Not better, FASTER. Everywhere in your reply that you've used the word 'better' you could probably substitute FASTER. It doesn't mean more efficient.

ĒThe BTU that are not extracted just continue to flow around the system until they too are extractedĒ Ė donít you think that this is a sign of inefficiency?
No, not at all... for it to be inefficient, the BTUs would have to be somehow 'lost'.

Wouldnít it better to have them extracted and have the boiler heat up colder water at higher efficiency?
Here's another way to look at this question:

Again, not more efficiently, only FASTER.

When there is a greater DT, the heat will move from the flue gases to the water more quickly. So, let's just use an example that it takes say 10 minutes of burner firing to get from 100 to 160 water. It might then take say 5 minutes to go from 160 to 180 because the transfer of heat is slower with less DT. In this case, fully 33% of the fuel burned is used to heat the water only 20 degrees... where the other 66% heated it up by 60 degrees.

It's not truly 'efficiency' in the strictest definition though, it just costs more!
 
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Old 12-28-11, 03:04 PM
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Forget EFFICIENCY! The only thing we are talking about is COST!

It COSTS LESS to heat the medium to a lower temperature.

This does in fact reduce all the 'parasitic losses', which can also save money.

But it doesn't equate to higher efficiency, unless you want to redefine efficiency to include a $ term.
 
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Old 12-28-11, 03:09 PM
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Although, if you wanted to loosely define Efficiency like this:

Accomplishment of or ability to accomplish a job with a minimum expenditure of time and effort
By saying that you need to expend more time or effort at your job in order to earn more money to pay for the extra fuel...

I guess I could accept that.
 
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Old 12-28-11, 03:14 PM
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I agree with you here, this a valid argument. However I want to use this argument for something I said earlier in this post Ė the standby losses are higher because the temp difference is higher between hot water and ambient air. So here is another proof that hither temp delta results in better heat extraction.
The higher standby losses is not because of the greater temperature difference. It is because you stored more BTUs in the boiler with 180F water than you would have with 130F water. So if the boiler cools itself down to room temp, those BTU's were lost up the chimney or into a place in the home that doesn't benefit from heating.
 
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Old 12-28-11, 03:15 PM
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One last comment for now:

I believe that in order to properly measure 'efficiency' of a system, it would need to be at a STEADY STATE of equilibrium. Very difficult to do... and to calculate efficiency when not at a steady state, you would have to start messing with calculus functions... derivatives and such... even more difficult to do.
 
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Old 12-28-11, 03:16 PM
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On/off, single(high)-temperature heating control results in a lot of cycling, and adds heat to the building until the limit (thermostat(s)) say stop. It is not efficient because of the cycling, and because of the excess work being done to heat the water. Simple reading here:

http://www.taco-hvac.com/uploads/FileLibrary/OM01.pdf

What you want is to match the heat input to the heat loss. Continuously. In real-time. There are several ways to go about this, by adjusting flow rates, water temperatures, and also firing rate. Simple reading here:

http://tekmarcontrols.com/media/literature/e0004_06.pdf

For a fixed firing rate, non-condensing boiler, fuel savings can be achieved by using some combination of the approaches in the brochure. Some of the approaches may also require some form of boiler protection, for which there are also a number of approaches.

For a standard residential setup, adding an outdoor reset to achieve partial reset (water temps constrained by return temp above condensing; generally 115F for oil, 130F for natgas), will reduce fuel use by reducing the amount of work required to heat the water to satisfy the heat loss.

How deep down the rabbit hole do you wish to go? There's a lot of neat stuff here.
 
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Old 12-28-11, 03:18 PM
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The higher standby losses is not because of the greater temperature difference. It is because you stored more BTUs in the boiler with 180F water than you would have with 130F water. So if the boiler cools itself down to room temp, those BTU's were lost up the chimney or into a place in the home that doesn't benefit from heating.
True, but the point being that with the boiler hotter, the DT will be greater, and the energy will be lost FASTER. So it is due to the greater DT in a way... non?
 
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Old 12-28-11, 05:21 PM
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True, but the point being that with the boiler hotter, the DT will be greater, and the energy will be lost FASTER. So it is due to the greater DT in a way... non?
I'm sure it plays some sort of a roll, but I think the extra BTUs are more important. This is just my opinion. Seeing a graph of the rate of heat transfer would certainly go a long way here.

Let's check out some numbers. My boiler is the Burnham ES2-4. It holds 3 gallons of water weighing roughly 25 pounds. Takes 1 btu to raise 1 pound of water 1 degree F, right? So let's assume my room temperature is 70F. To raise that 25 pounds of water from 70 to 130, it takes 2,500 BTUs. To bring that 25 lbs of water from 130 to 180, it takes an additional 1,250 BTUs. That's 50% more energy to bring it up to 180 than to stop at 130. So for this additional energy to be a waste, the boiler would have to cool down to room temp before another call is made, right? This is most likely, and probably only likely, to happen during the shoulder seasons.

So, in closing, I don't know.
 
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Old 12-28-11, 05:33 PM
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25 pound of water from 70 to 130 ...

25 * 60 = 1500 ? non?

So for this additional energy to be a waste, the boiler would have to cool down to room temp before another call is made, right?
It depends on where the heat goes as it cools. Into the home, or up the chimney...

Standby losses are probably higher during the shoulder seasons... because there is probably more heat left 'stranded' ...

This is, I'm sure, a big factor in the theory that not heating the water as hot saves fuel. If you only heat it to the temperature required to heat the home, and use all the heat you've made, there's less waste...
 
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Old 12-28-11, 05:45 PM
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But isnt 180F better or actually 190F for finned baseboard to emit optimal heat? So heating a boiler at a lower temp will prolong the circ to run and use more electric. Waste of resource?

I would say heat fast to 190F for optimal heat release, less burn time once optimal temp is reached and maintained, and less circ run.????? No?

Mike NJ
 
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Old 12-28-11, 05:53 PM
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Up the chimney or out the cellar walls and floor.
It depends on where the heat goes as it cools. Into the home, or up the chimney...

Standby losses are probably higher during the shoulder seasons... because there is probably more heat left 'stranded' ...

This is, I'm sure, a big factor in the theory that not heating the water as hot saves fuel. If you only heat it to the temperature required to heat the home, and use all the heat you've made, there's less waste..
I agree and also, imo, it is that simple. No need to complicate it any further.

Peter
 
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Old 12-28-11, 05:58 PM
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The primary energy loss for a hot-water boiler, by far, is the stack loss. That includes the thermal energy in the flue gas going up the stack, plus the latent heat of the moisture in the flue gas (for non-condensing units). The stack loss will be less if the exhaust temperture is lower - which happens if the water temp is lower. In that situation, more heat from the stack gas will be absorbed by the water. Boiler efficiency is, then, higher with lower water temps. Q.E.D.

Quit fighting it.
 
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Old 12-28-11, 06:09 PM
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But isnt 180F better or actually 190F for finned baseboard to emit optimal heat? So heating a boiler at a lower temp will prolong the circ to run and use more electric. Waste of resource?
Better? I guess if you are impatient and want to FEEL that blast of heat... yeah, then it's better, but certainly not as comfortable.

I personally would rather pay the pennies to run a pump than the dollars to burn the fuel, and be more comfortable with a more constant room temperature.

If your theory were correct, then how could ODR save any money?
 
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Old 12-28-11, 06:15 PM
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Stack losses are going to increase significantly at higher tempertures.

It will take 25.5 minutes longer to heat at 160 vs 190
190*=640btu's hr, 160*=450btu's hr.
Just the comfort factor alone, if nothing else wins the day, imo.
Even if it does cost more for electic.
Longer smoother lower heat vs a big blast then a cool down then another blast.

Peter
 
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Old 12-28-11, 06:23 PM
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I personally would rather pay the pennies to run a pump than the dollars to burn the fuel, and be more comfortable with a more constant room temperature.

I agree. Plus, if we are worried about total energy usage, the power consumed by the pump will wind up in the circulating water - except for maybe 10% that will be dissipated into the boiler room, and then wind up in the house, eventually. Of course, electrical energy is more expensive than gas or oil. But the cost of the electricity to run the pump is miniscule compared to the fuel to heat the house.

Need to get real here - and quit fighting what is commonly known. Better, to spend our energy trying to understand the basic principles. Either that, or propose a new law of thermodynamics.

 
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Old 12-28-11, 07:04 PM
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then how could ODR save any money?

Government conspiracy.....

ODR runs two pumps, or sometimes three with p/s piping. Plus increased cost of install parts and labor.

I would have to see #'s on circ use vs fuel savings, over cost of unit during the units lifetime, cost of install...etc..

I say it may be break even. But the goverment profits.

Maybe I am delusional?

Mike NJ
 
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Old 12-28-11, 07:40 PM
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quit fighting what is commonly known
I don't think he's fighting it... just trying to understand the why's and wherefore's ... curiosity is a good thing.

Maybe I am delusional?
 
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Old 12-28-11, 08:04 PM
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I dont think I am that delusional really. If you really do the math and incorporate real statistics I am sure it can be calculated.

Look, all these low temp boilers with fancy controls also break down more. Hence more service calls. Hey lets add all the diesel fuel burned from the service techs doing ODR repairs...

Lightning strikes. Electronics fried? What kind of energy does it take to make all the controls?

Add the additional fuel to make the mostly plastic parts for these ODR type boilers amd controls.

And soon lets add possible medical costs. All the techs working on these ODR low temp 130f boilers would have the greatest chance of Legionella.

LOL.

Sure reduce your carbon foot print by 50% but the industries doubled theirs to manufacture it.

Like the new CFL light bulbs as an example. Saves money but big cost to produce.

Ok I hear sirens......are the men with the white jackets here for me yet?


Mike NJ
 
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Old 12-28-11, 09:05 PM
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An oil burner that burns at a 0 smoke spot is considered to be converting all the oil into heat, in a practical sense and a steady state efficiency test measures the efficiency of the heat exchanger only.
 

Last edited by NJT; 12-29-11 at 07:48 AM. Reason: removed pointless dialog
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Old 12-28-11, 09:38 PM
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Keeping a steady 180F during the shoulder seasons or even in 30F outdoors leads to temperature spikes. In the boiler core it translates to increased stack loss because in essence the core becomes a radiator when the heat source is removed. The greater the temp differential, the greater the transfer of heat energy up the pipe.

In the heated space, overly hot baseboards cause the temperature to overshoot the target, and though its not exactly wasted, it affects the comfort level. Compare it to your car making jackrabbit starts as opposed to smooth steady throttle control.

Low cost and efficiency right now are two different things. Mod/cons win the efficiency contest. The Prestige Solo would save me about $90 per heating season in fuel. But the $2k higher price over the ES2 means I may never make up the difference in dollars. The ES2 with ODR is a nice blend of old and new tech that works. The outdoor temp is now 30F and the set point just bumped up from 130 to 134. Good stuff, and it's quiet too!
 
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Old 12-29-11, 04:37 AM
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My 2 cents on cast iron boilers.
As stated when you raise boiler temp you raise stack temp. As stack temp increases the O2 decreases and the flame cools off due to more air over the flame. Stack increase, higher O2, cooler flame, equals less efficient. Remember efficiencies are tested at 120 return temp and 140f supply temp under AFUE procedures.
Btu's and water temperature are two different things. You can have 100k btu input and have 120f maximum supply water or 100k input and have 180k maximum supply water temp. I have seen jobs where the same boiler goes from not being able to heat the home to where it can heat the home in the coldest months. The boiler went from not being able to get the water temp in the system above 125f to now heating the system to 160f. Same btu input but different output temps. The same amount of btu's were added to the system. Other than what goes out the vent, btu's are never wasted. The question becomes are they used to full potential.
As far as the baseboard goes, higher temps increase the airflow across the baseboard due to higher delta-T's, which does give us more btu output but will also increase heatloss due to more air currents in the home.
The one thing that is not addressed is flow. Flow changes with water temperature. As water temperature increases the resistance to flow is decreases. This being said the flow is the only down side to operating with lower water temperature, more resistance to flow.
ODR runs two pumps, or sometimes three with p/s piping
ODR can be done with one pump, it does not require two pumps. You can do boiler reset with one pump along with manifold systems. This would mean one zone for the whole home or multiple zones with zone valves.
 
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Old 12-29-11, 08:14 AM
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xiphias,

I read both of your pdfs and unofrtunately it doesnít really explain why it more efficient to use colder temperature. It uses the same old analogy with a car that I find faulty Ė itís more applicable to overshooting the tstat temp while using the higher water temperature, which I buy into, but that should explaing the whole mechanism of more efficient boiler work on loweer temperature. The other articule explains differenet approaches how lower temperature heating could be controlled/configured, but again it doesnít explain why and how. They also allude that higher temp heating is more on-off and lower temp heating is more continous. I would think that on/off is more applicable to bigger size boilers vs appropriately sized. Lowering from 200F to 180F would still result in cycling, but instead of going between 180 and 200 it would go from 160 to 180. The matter of fact, I beileve that 180F water would give away temperature to the air more readily and it will cool off faster, possibly making the boiler firing longer. So that might negate the negatives of overshooting the temp.


So, yes, I would like to go deeper into a rabbit hole

lawrosa,

But isnt 180F better or actually 190F for finned baseboard to emit optimal heat? So heating a boiler at a lower temp will prolong the circ to run and use more electric. Waste of resource?

I would say heat fast to 190F for optimal heat release, less burn time once optimal temp is reached and maintained, and less circ run
This is the very thing that prompted me to start this topic. NJTrooper mentiones that itís less comfortable, but this topic is strictly about fuel saving. While comfort is an important aspect, itís out of scope for this discussion (I feel like Iím on one of my work meetings, saying that something is out of scope )

gilmore,

stack looses, standby losses so far at the most valid reasons for energy saving with lower temp. I think these are valid. and Iím not fighting! as a matter of fact, due to the input of many members here (thank you!) I lowered my temp from 200F to 180F as of yesterday

NJTrooper,

If your theory were correct, then how could ODR save any money?
My understanding is ODR works wonders if you get into condensing range for condensing boilers. And there is a very simple explanation for it Ė latent energy. What Iím trying to do is to find such clear explanation for ODR or simply lower water temp for conventional boilers.

rbeck,

ODR can be done with one pump, it does not require two pumps. You can do boiler reset with one pump along with manifold systems. This would mean one zone for the whole home or multiple zones with zone valves.
Can you please educate me on this a little bit? I was under impression that ODR is simply a sensor that based on the outdoor temp figures out desired boiler temperature and if possible tries to keep it in the condensing range or for conventional boilers as cold as possible. In my simple thinking a boiler like Burnham ES2 can be supplemented with an ODR card (purchase separately) and now have the ODR capability without any changes to existing infrastructure. What are the additional pumps being mentioned here?

Also, can someone explain to me how on Earth can Burnham ES2 work with water as cold as 110F and not condense??? Or condense and not require a drain? And if it condenses, then shouldnít it be condensing boiler?

Sorry for long posts, I like to dig deep
 
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Old 12-29-11, 08:45 AM
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What are the additional pumps being mentioned here?
Infrastructure... there are a number of different piping strategies that can be used. I think that Mike is under the impression that in order to use ODR one must use the 'primary/secondary' method of piping, and this would require 2 pumps. A further extension of the primary/secondary method would be one were a 'bridge' is built between to hydraulically separate loops, one around the boiler and one around the radiation. This 'bridge' would inject heat from the boiler into the radiaton by means of yet another (variable speed) pump.

ODR can be as simple as you state. A sensor on the boiler supply, and a sensor outdoors. The boiler water temperature is modulated by controlling the burner based on the calculated heating curve.

can someone explain to me how on Earth can Burnham ES2 work with water as cold as 110F and not condense?
Rbeck will have the final word on this, but the way this boiler (and the MPO oil boiler) are set up, there is a 'jet' in the return port of the boiler which 'shoots' the cooler return water into the center of the volume of water inside the boiler. This action mixes the cooler water with the hotter water before it has a chance to contact the cast iron surfaces and cool the interior of the boiler. This is versus a conventional design where the cool water is simply 'dumped' into the bottom return port and 'pools' there, causing cold spots on the cast iron where the condensation would occur. Jetting the water into the center of the water volume inside the boiler reduces the stratification that occurs in 'standard' designs.
 
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Old 12-29-11, 08:54 AM
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What Iím trying to do is to find such clear explanation for ODR or simply lower water temp for conventional boilers.
1. REDUCED STACK LOSSES

2. REDUCED STANDBY LOSSES

Those are the big two. There are other probably nearly insignificant reasons.
 
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Old 12-29-11, 09:03 AM
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I think that Mike is under the impression that in order to use ODR one must use the 'primary/secondary' method of piping, and this would require 2 pumps.


Not really, isnt a boiler bypass called the poor mans ODR? Cooler system temps, or hotter depending on outdoor temps?

Frome comfortcalc.com

 

Last edited by lawrosa; 12-29-11 at 09:51 AM.
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Old 12-29-11, 09:42 AM
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NJTNJTrooper,

Thank you for explanation of the jet shooting technique used in ES2 Ė pretty cool! And Iím glad that ODR could be used in a simple configuration as well. Iím happy with stack/standby losses explanation as long as savings are mere percent or two for 20F difference. The higher saving must come from condensing. If thatís the case, I think all the questions are answered here.. Except this one (not related, but Iím going to piggy back on my original thread):

I noticed that one particular boiler (donít remember which, but I could dig it out) has build in air separator. None of the others (Burnham ES2 in particular) I looked at mentioned anything to that regard specifically. I do not have any air bleed valves in the baseboards, so I was under impression that there must be a device somewhere in the boiler loop(s) that would take care of it. I doubt my old Repco boiler has something built in for that purpose.

So the question is Ė will any modern boilers have it? If not, could a separate device be purchased if needed and retrofitted into a system? Just trying to cover all fronts here
 
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Old 12-29-11, 10:01 AM
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Iím happy with stack/standby losses explanation as long as savings are mere percent or two for 20F difference.
Yeah, no more savings than that really... you weren't expecting miracles I hope! Remember when I first mentioned it... I said "save a few dollars on fuel" ... I meant that literally!

I do not have any air bleed valves in the baseboards, so I was under impression that there must be a device somewhere in the boiler loop(s) that would take care of it.
There is an 'air scoop' device... of various forms, which collect the air in the passing stream and if you have a bladder/diaphragm tank, will vent the collected air to the atmosphere, if you have a standard steel compression tank are supposed to pass the collected air back to the tank where it belongs. If you have a standard compression tank then automatic air vents are NOT to be used.

This is what a typical diaphragm tank setup would look like.


image courtesy masterplumber.net
 
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Old 12-29-11, 10:08 AM
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That pump dont look like its pumping away.... "Trooper"???? Doh....

Mike NJ
 
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Old 12-29-11, 10:18 AM
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No, maybe not... I just included it as a 'looks like this' example of scoop/tank/vent. I didn't even see the pump in the lower left until you mentioned it.
 
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Old 12-29-11, 10:30 AM
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Oh, thought it was your boiler troop.....

Mike NJ
 
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Old 12-29-11, 10:32 AM
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NJTrooper,

The top of the air scoop on your picture looks like this thing on top of my boiler:



it's not the same thing, is it? there is nothing on top of the expansion tank.

my old thread http://www.doityourself.com/forum/bo...ml#post1921068 has more pictures of my setup
 
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