No difference for non set back savings.. (ME)

Kevin O. Pulver

Insulation/heat loss

Mark the big show home I entered in the Wirsnor contest was superinsulated with spray foam and blown in cellulose from the 21' high ceilings on down the walls. One wall had glass all the way to the ceiling. It lost about 6 degrees overnight at design conditions, but that was with NO HEAT WHATSOEVER. I thought that was pretty good. Kevin

[Deleted User]

Old school, old rules...

John, you are citing old school rules of thumb that might have been relevent when used in comparison to the old atmoshperic appliances with significant standby losses. THe standby loss of these new appliances is nearly non existant, and most of that truly ends up IN the house, not UP the stack.

MOdern day science is based on a flawed study of homes that leaked air horribly. Is that applicable to all homes and all scenarios? How many homes have you seen where the savings from apllying a set back thermostat is miserable? I have quite a few, hence the reason for my minim experiment.

Living with hard and fast rules of thumb without qualifying them can end up with unpredictable results.

THe whole point of my experiment was to establish the base relative efficiency of a mod con boiler in MY setting. What it does in YOUR setting is probably completely different. Instead of me data logging everything going on in MY home, why don't you try the same experiment in YOUR Home and see what happens? More information that is less annecdotal.

I didn't do this experiment to change the world John, I only did it based on a gut feeling. My house is more comfortable now than it ever was, the equipment is working less hard and using the same amount of fuel. I realize it goes against the grain, but thats what happens when we think outside the old school box.

If certain people had not thought outside the box, we still be in the dark ages...

ME

[Deleted User]

Rob...

Boiler efficiency is very subjective. As for true thermal efficiency, which NONE of the usual consumer oriented BS (Read AFUE) is concerned, I've witnesed my "appliance" at 99.8 percent efficient when my combustion analyser was telling me 86% efficiency.

My method of analyis is pretty straight forward and simple. I have a gas meter on the appliance that gives me a contact pulse every cubic foot. THe caloric content of the gas is a given.

My system is based on a one pipe system. THe flow is a fixed constant. I have a visual flow meter on the hydronic side, and the on board control has data logging abilities monitoring inlet and outlet tempratures. About th eonly variable on the fluid side is temperature adn delta T and its actually fairly stable.

Output (flow X delta T X 500) divided by input (gas meter), = efficiency. 99.8 percent was witnessed at design condition, with the boiler running at minimum input, operating at an average of 140 degrees F. The theoretical advantage of operating within the condensing range is true, but like combustion analyzer efficiency, it too is subjective. I don't even monitor the condensate production, other than noting that it is occuring, and treating it with tree root killer and marble chips for PH neutralization. It is what it is, and does what it does. I'm certain SOMEONE has done their research in that arena, but to me, its just there.

My emmiters are a vast combination of flat panel radiators, radiant ceilings, cast iron radiators, radiant floors, towel warmer, radiant bathtub, most all controlled by NETRV's. Extremely stable and VERY comfortable, except when coming out of a deep set back period, when we experience human discomfort due to lower temperatures. Or should I say USE to experience lower temperatures...

About the only disadvantage of not doing set backs is that the radiant floor, which is my reference zone, is not as warm as it use to be coming out of set back, but it's NOT uncomfortably cool either. Just slightly warmer than neutral for the most part until it gets colder outside.

No biggy compared to overall wall to wall, corner to corner comfort.

ME

Ken_40

Mark,

I do not doubt your observations, mine are parallel in the new house we now live in. I do however question the pure science of a cooler home losing fewer BTU's to outside than a warmer house.

My home's thermal envelope is so good, my 5 degree setback never gets "struck" despite sub-zero OD temps.

When you save 5 or 10% of an already obscenely low fuel consumption/efficiency, the setback stat's benefit is not nullified, merely diminished to a point that makes justification almost moot.

Would you agree?

carol_3

I just have to jump into this! Not all setback thermostats are the same. Like with any product,there are great quality ones that don't necessarily cost much, and there is very expensive junk. Having been in the thermostat biz for 27 years, I have to say that quality means tight temperature control. To get that you need a stat that does not add heat to itself by using cheap elecronic conponents. That leaves only Honeywell and White-Rodgers. Other brands of electronic stats add heat whenever there's a call for heat (current draw), and who knows what temperature you actually end up with. Today's set back stats don't need to be expensive or difficult either. As for changing batteries, when you're installing a stat, run that extra wire to connect the stat "C" terminal to the transformer, and no batteries are ever needed--not even for backup, becaue modern stats have non-volitile memory.

jp_2

self heating tstat?

the question i have for you carol, whats the heat dissipation difference between a triac and a relay?

i would think the different is quite minor in such low power applications.

this actually comes from a topic weeks ago, but I only thought about it recently.

realolman

Huh?

without regard to fuel savings, creature comfort, or system design or functionality...simply because somebody said it was a good idea.

I thought that was the way everything worked

Ken_40

Darrell

I agree with everything you write, except for the notion, "which should put the least strain or heavy load on a heating plant."

Boilers are either on, or off. True, when "on," they may be modulating, but we do not "overwork" or "overburden" anything by turning it on, or off. The number of times we may turn it on or off per day however, IS a consideration!

Using terms like "overburdening" or "making the boiler work extra hard" by virtue of it simply being "on" is mis-leading and innacurate. Using that term, "strain" suggests a burden on the boiler that cannot exist. Boilers made to run for long periods of time are far more efficient AND far less "wearing" than boilers that turn on and off.

John Ruhnke

Scientific rules...........

Mark,

Once you understand the rules of science you should be able to predict the out come of an monitoring project. They aren't old school. They are tried and proved methods. In Europe, you are not allowed to design a system for more then 138 degrees. Outdoor reset reduces temps even further. They have been using Mod/Cons a lot longer then we have. They still believe in lower water temps. Only a few contractors here on the wall believe what you believe. No one else.

I am not saying you are wrong. I am only saying that your results contridict science. When that happens you have to find out why. I have done HDD analysis on a few projects. The savings were around 20-30%. They were as predicted. By the rules of science, I predicted the outcome. So I am not going to try and look deeper. The rules matched the field research results.

You should save money by running a condensing boiler under the condensing mode of 130. That is a rule of science. If you didn't get the expected results then you have to look deeper and find out why. Maybe the rules are wrong. Fine give us a new rule. Maybe the boiler doesn't recover the heat from the condensate properly. Maybe the setback thermostat short cycles the system. Maybe if you fix some of the problems then you will see the expected results. Maybe you will find that the old school rules are wrong.

I don't have a condensing boiler in my house. I have a Buderus oil fired boiler with tekmar controls. I tore the roof off of my house and doubled the square footage. A before and after HDD analysis is useless on my house. If I had a condensing boiler then yes I would repeat the experiment.

Maybe another wallie with a condensing boiler could help us out. Maybe you could help them to set up the same experiment on there house. Anybody out there up to it?

John Ruhnke

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Dave_4

T'stat temperature

Didn't most of the older stats have heat anticipators that intentionally heated the stat For the triac, the heat would be whatever the voltage drop across the semiconductor junction is. Figure about .6 volts. Take that times the current and you have the wattage. Relay contacts should have no resistance, no heat generation, except for the coil; and sense they can run for a year on a penlite cell it has to be minimal..

Back on topic, for an on/off boiler, wouldn't the savings have to be equal to the time difference between how the long boiler would have to run to maintain temperature, versus the amount of time it has to run to recover in the morning?? There has to be some real savings at some point???

Dave_4

T'stat temperature

Didn't most of the older stats have heat anticipators that intentionally heated the stat For the triac, the heat would be whatever the voltage drop across the semiconductor junction is. Figure about .6 volts. Take that times the current and you have the wattage. Relay contacts should have no resistance, no heat generation, except for the coil; and sense they can run for a year on a penlite cell it has to be minimal..

Back on topic, for an on/off boiler, wouldn't the savings have to be equal to the time difference between how the long boiler would have to run to maintain temperature, versus the amount of time it has to run to recover in the morning?? There has to be some real savings at some point???

Dave_4

T'stat temperature

Didn't most of the older stats have heat anticipators that intentionally heated the stat For the triac, the heat would be whatever the voltage drop across the semiconductor junction is. Figure about .6 volts. Take that times the current and you have the wattage. Relay contacts should have no resistance, no heat generation, except for the coil; and sense they can run for a year on a penlite cell it has to be minimal..

Back on topic, for an on/off boiler, wouldn't the savings have to be equal to the time difference between how the long boiler would have to run to maintain temperature, versus the amount of time it has to run to recover in the morning?? There has to be some real savings at some point???

Chris_82

old school?

Doesn’t matter if it's a mod con or iron, until we face up to the fact this country uses more fuel than any other and was the only country to not sign the Kyoto protocol, until we as a nation change our ways many of these arguments are academic and not USA based! They only serve the marketing departments of those that are exploiting energy savings and media hype! Low temps save fuel, cast iron saves money, Mod/ cons enable a class of people to live on the Marion shoreline in million dollar homes and make the rest of us that listen to our customers sick of listening to our customers.

Tony_23

Oh please,

Aren't you the one who doesn't like "the rules" ?

With all due respect, John, get your facts straight. Max temps in Europe are higher than 138.

Open your mind a bit and realize that condensing isn't the only ride in the carnival. Modulation has a much larger role. I have customers that saved close to 30 % by switching to mod/non-cond equipment. Close regulation of space temps, as well as water temps, also plays a larger role, IMO. You're ignoring the fuel required to recover from setback, and only looking at what was saved during the setback period. Even if you setback 5 deg and the house only loses 3, you still have to make up the 3.

Here's a rule : Heat moves to cold. If the mass of a bldg loses 5 deg during setback, it must also gain those 5 degrees in recovery. How many btu's are required to recover ? To maintain ? ME says his house is the same. My experience with customers' homes and my own are the same as his. Show me a "rule" that will disprove what I've seen with my own eyes is wrong. Hard to argue with facts. Fuel usage / degree days with the same indoor setpoint is hard to disprove.

Darrell

OK I'll go there with you...a boiler system doing what it was designed to do isn't asking too much, or working it too hard. However, setback settings, allowing the structure to cool must necessarily be made up at some point, which does in fact translate to "work" being done. The resting period does not equal the make up period...it requires more "work" to make up the temperature swing than it saved by coasting. Such is the nature of things. I do not have any kind of a science degree...I started out to be a history teacher...but I can observe the world I work in...and the equipment that I work on...which was the original question. In my opinion...we can design and build a technically superior heating system that is as efficient at converting fuel to comfort as humanly possible. And as long as the only parameter that we use for judgement is efficiency of conversion the arguement is confined to that. But, when we introduce creature comfort, a highly subjective parameter, to the arguement, the science of efficient conversion of fuel seemingly becomes largely academic and has to make some adjustments in the real world. In other words, as the original question asked, does a technically superior system design necessarily equate to a more comfortable living environment? The answer, apparently, has been observed by many knowledgeable heating pros to be no.

Efficiency of fuel conversion, creature comfort, and economic yearly cost considering fuel AND maintenace are three aspects that should be considered in any heating system sale. They are not the same thing and a happy balance has to be struck between them based on what the owner wants. Does he want walk away/never touch a t-stat comfort? Does he want the absolute lowest monthly fuel bill? Does he wants long term system reliability and low maintenace cost? We can dress up a Mod/con boiler with all the bells and whistles and get as close to a perfect living environment as possible...but the maintenance costs will, at least potenially, eat up any economic realization of dollars in the owners pocket. We can strip the system design to an atmospheric on-off boiler with no bells and whistles, we'll potentially sacrifice some of the perfect living environment, but the maintenace cost will be comparatively nil.

Ken_40

Perpetuating a myth?

The notion that the energy "saved" during setback is then "lost" on re-heating the same structure back to the original temperature and the restoration of its original "thermal mass," is false.

The basis and scientific rationale of setback thermostats is simply this: "Any 'conditioned space' loses LESS energy when the differential between the outdoor's is less than the inside was - prior to the setback."

Does returning the conditioned space back to its original temperature (including the thermal mass which was also lost to some degree during setback) equal the same loss as would have occurred WITHOUT setback? The answer is unequivecal. No; i.e., a house that was 68F while 20F outdoors, will always use less energy if setback ANY AMOUNT OF DEGREES LESS - THAN HAD IT NOT BEEN SETBACK AT ALL. The fuel consumed to return that space to 68 will ALWAYS be less than with no setback, would have taken.

The real issue is not debating basic science, which is after all, undebatable. The issue is just how much "savings" will be realized by the setback strategy! The answer to that is, "That depends."

Given that most of us like much cooler bedrooms when sleeping, the issue seems to have morphed into far more an issue of comfort than savings.

I would totally agree, the alleged "savings" day/night programmable 'stats advertise, is only valid in extreme situations (poor envelopes) most of us will never see. On the side of the setback 'stats, the ever escalating cost of fuel may make the minimal savings most homes might see, more and more justified in the future.

The bottom line becomes, will a $50-$100 setback 'stat save its 30 to 70 dollar increase over a plain-jane 'stat fast enough to justify its "savings"? Better yet, who wants their bedroom zone at 68F while under a 200-dollar L.L.Bean down comforter, sweating their butts off?

Weezbo

i think set back is particularily valuable in commercial

light industrial industrial settings.*~/:)

sensors...sensors good. slow acting globe valves..slow acting globe valves good.

constant circ good..injection systems good.

Caleffi Profile Good.

Tony_23

Well there you have it

Nevermind what you see or experience yourselves.

Personally, I think setback stats have been "marketed" very well in spite of logic. Maybe we should use them on ALL systems, regardless of type. After all, they save fuel no matter what, right ? Theory sounds right, but it really only works as advertised when practiced for longer periods of time than most homeowners do, overnight.

Mike T., Swampeast MO

Ken:

Every setback study (actual structures & mathematical) that I've found says in one way or another that the savings from setback begin once the reduced temperature is being maintained. That Canadian study of the two identical homes for instance found no savings from setback unless the outside temp was less than about 32°F.

Were the houses furnished and occupied I suspect that the outside temp required for savings would have been significantly lower.

Chris_82

Ken and others...

When you start to mention programmable t stats, they are the only thing the USA, DOE is and has since 1920s lobbied for mandatory installation...they save energy with out all this rhetoric. They work regardless of outside temp...they work when we forget to turn the thermostat down...they work period...they work and are mandatory in federal buildings...Feel free to quote that CN study...because every study I am familiar with says they do work! Since 1960 when I was first involved with "The New Alchemy Institute," All of the DOE energy studies and homebuilding recomondations, my first total envelope home construction made with the assistance of Anderson insulation company of Abington MA and with the assistance of Menneprogg (spelling) heat ex changers air/air, Heat assoc., New England Solar Energy Association, Mass Audubon Energy saving project, The Energy Design update Cutter information group, Arlington MA, or feel free to contact NATAS in Montana, or the National Appropriate Technology Assistance Service, and I can go on... Turn the temps down and you save...period, not debatable. Attributing energy savings to a particular "heater" is irresponsable and blatently opportunistic.

[Deleted User]

You're just mad...

because its a Munchkin.... (BIG smiley face at ya:-))

ME

John Ruhnke

How setback works...........

Tony,

You said " Even if you setback 5 deg and the house only loses 3, you still have to make up the 3."

That is not how setback works. At night when the outside is 40 degrees and the temperature is set for 65 degrees, the system has to maintane a delta tee of 25 vrs maintaning a delta tee of 30 if setback wasn't used and the temp was set at 70. At night the system is operating for a long time at a smaller delta tee so you will save money with night time setback. You have to think about the whole night. Not just the cool down and start up periods. It is coldest at night, so the delta tee is always larger. Scientific studies are much more accurate and in depth then what you do or think you might experience. Many studies have proved that setback works. The experts make some very good rules to go by from their studies. You can use the rules to predict what is going to happen in a monitoring project. Sometimes the results don't match the rules. That means you have the wrong rules and need to study up a bit more. You need to learn more until you have the right rules. That is how good science works.

It is a law in Germany that you are not allowed to design for more then 138 degrees. It is also a law that you have to use some form of reset to reduce the temps even further like in warmer weather. They use both indoor and outdoor reset. Buderus has a method that measures the delta tee of the feed and return and adjusts the temps accordingly.

I believe that many of the setback thermostats short cycle the boiler in an attempt to improve comfort. Honeywell has a soft start feature that seems to do this. This sometimes will negate any savings from setting the thermostat back. But setback is a very good way to save money in fuel bills and if done right it will work. I am in the process of monitoring this in a few houses and I will know more in a few months.

JR

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Dave_4

Ken is bang on.

He's saying that there's a savings but it becomes infinitely small in some cases. Kind of the reverse of insulation. On a R12 wall that first R gets you much much more than the eleventh or twelfth. Declining returns. Same thing if it takes a long time for the home to leak enough heat to stabilize at a lower temp. If simply in a free-fall the whole time, the system is going to have to restore all the heat to get it back up to a stable temp. The stable temp is the variable we have at our disposal for control strategies. If the house needs minimal heat why not use it for warm feet in the morning? If a house is high mass and has uneven heating, then any setback would cause discomfort whenever the system is falling back and possibly even more on the recovery. I guess the question becomes, was the system designed to benefit from setback. It is possible to increase comfort through setback if done right. Let's face it. Different materials heat up at different speeds. If the stat doesn't move eventually the whole house equals out about as well as it can. The MRT hits a steady state. But do we need it the same temp all day?

My house is fairly tight, but the wall insulation is really marginal (but it's brick on one side and perfectly fine 5/8" drywall on the other so I'm not doing it or paying for doing it). My house drops temps. My setback saves a bit. With the new modcon, the bit is now less than half and may actually be the bad example if I set the curve too high and have it come out of condensing just to give it headroom for recovery.

Setback t-stats are a tool for a control strategy. Useless on super-houses unless you want to apply heat for morning feet or something like that, but most of your customers probably live in normal leaky but healthy homes? It's a control strategy. If you don't need it, you don't have to use it. It saves less and less fuel as efficiency of the boiler, envelope and mass increase and if it results in a modcon running too hot as a result is costs. Outside of that it is a comfort thing. With anything other than a constant temp, the house's heat will not be fully even (I think it takes several days to even out). That said, some homes can be comfortable in the way they recover from setback - it is how it is designed. Some people take also take a different kind of comfort in thinking that they are doing what little they can. The value of the comfort factor may be a huge multiple of the minimal savings in some cases.

It's just a tool.

I can't figure out why this subject is debated this much?

realolman

no consequence

> He's saying that there's a savings but it becomes

> infinitely small in some cases. Kind of the

> reverse of insulation. On a R12 wall that first R

> gets you much much more than the eleventh or

> twelfth. Declining returns. Same thing if it

> takes a long time for the home to leak enough

> heat to stabilize at a lower temp. If simply in a

> free-fall the whole time, the system is going to

> have to restore all the heat to get it back up to

> a stable temp. The stable temp is the variable we

> have at our disposal for control strategies. If

> the house needs minimal heat why not use it for

> warm feet in the morning? If a house is high mass

> and has uneven heating, then any setback would

> cause discomfort whenever the system is falling

> back and possibly even more on the recovery. I

> guess the question becomes, was the system

> designed to benefit from setback. It is possible

> to increase comfort through setback if done

> right. Let's face it. Different materials heat up

> at different speeds. If the stat doesn't move

> eventually the whole house equals out about as

> well as it can. The MRT hits a steady state. But

> do we need it the same temp all day?

>

> My house

> is fairly tight, but the wall insulation is

> really marginal (but it's brick on one side and

> perfectly fine 5/8" drywall on the other so I'm

> not doing it or paying for doing it). My house

> drops temps. My setback saves a bit. With the new

> modcon, the bit is now less than half and may

> actually be the bad example if I set the curve

> too high and have it come out of condensing just

> to give it headroom for recovery.

>

> Setback

> t-stats are a tool for a control strategy.

> Useless on super-houses unless you want to apply

> heat for morning feet or something like that, but

> most of your customers probably live in normal

> leaky but healthy homes? It's a control strategy.

> If you don't need it, you don't have to use it.

> It saves less and less fuel as efficiency of the

> boiler, envelope and mass increase and if it

> results in a modcon running too hot as a result

> is costs. Outside of that it is a comfort thing.

> With anything other than a constant temp, the

> house's heat will not be fully even (I think it

> takes several days to even out). That said, some

> homes can be comfortable in the way they recover

> from setback - it is how it is designed. Some

> people take also take a different kind of comfort

> in thinking that they are doing what little they

> can. The value of the comfort factor may be a

> huge multiple of the minimal savings in some

> cases.

>

> It's just a tool.

>

> I can't figure

> out why this subject is debated this much?



I don't remember whether my brother in law was talking about some city meeting or a school board meeting, but it would probably apply to either... He said they'll spend a million dollars in 2 min but argue and discuss 20 bucks for hours.

I go to an electrician forum and they'll have long threads like this one on the subject of sticking a piece of romex through a 2 ft piece of conduit to a receptacle on the basement wall.

Probably the reason I'm jumping in is that a wrong answer has no consequence.

I have hooked up some sensors and a computer to my boiler and I can tell you that determining whether or how much you are saving is not easy.

Wayco Wayne_2

Uni R

I like your comment on customers that take a different comfort in being proactive in saving money. I have customers like that. One of them was having problems because I installed a Mod Con with Outdoor reset, and his house temp wasnt catching up in the morning like he was used to, because of the lower boiler temps. Then someone pointed out that the new boiler, (TT Prestige) had a boost function where you can program a time interval where if the boiler is not satisfied it will boost the temperature 16 degrees, and continue until it reaches a 180 limit. This was a perfect remedy for this particular customer who loves turning back his temp at night. I pesonally think he should not set back and ride the curve, but he's happy so I'm happy. By the way I have started refering to the lag in thermal mass temps in a room coming out of set back as "charging the space," much the same as "charging" a slab in a radiant floor application. It helps some people understand. WW

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[Deleted User]

BINGO!!

Professor Wayne gets the Cupie Doll.

The reason I don't think I was seeing any additional significant savings from the programmable set back thermostat, AND wasn't experiencing the comfort issues I had expected was due to a conflict in design.

I had an intelligent ramping thermostat connected to an intelligent reset boiler, and neither knew the other existed. I heard my programmable thermostat turning on at 1:00 AM trying to hit its target in the AM. And it NEVER did unless it was extremely mild outside. In an effort to correct the situation, I took the ODR out of the equation. THis made a difference of one hour in the start time (2:00 AM) for the AIRS thermostat. Not a significant savings.

I guess the point I'm trying to make here is multi fold.

1. If you are using an intelligent outdoor reset boiler, then the conservation is being done at the point of energy generation, NOT the point of use.

2. As Ken Secor so eloquently pointed out, 10% savings of nothing is still nothing... Go multi zoned and turn down only those spaces in which you want a cooler environment.

3. If you have an energy hog for a dwelling, your money would be better spent (ROI wise) doing massive conservation efforts first, ultra high efficiency heat generating appliances second, and programmable thermostats last.

I'd say I was sorry for stirring up the pot, but in reality, I am not, and the original post got a lot of people thinking, which as Martha would say, is a good thing...

Good job Wayne. Education of the public is key here. You can have one or the other but not both without giving up something in the way of comfort, and limited energy savings. Think outside of the box. The greatest reduction in energy consumption is due to the application of one type of appliance (Mod Con) over an archaic technology (atmospheric), NOT the use of programmable thermostats.

If you can't afford to do energy conservation, nor appliance upgrade, then the use of a programmable thermostat is probably your best bet.

Carry on...

ME

Ken_40

Wayne,

I believe the Honeywell "anticipatory logic" feature would mitigate your observed shortcomings. We are amazed at the adaptive intellegence recovery feature's accuracy and ability to "learn" the timing on extremely variable weather conditions.

Have you tried one of that style?

Wait. Mark and you already found the problem/solution. Never mix technologies without review of all the "what-ifs."

John Ruhnke

Mark should have saved 25-35% with ODR...........

Heatman,

The following quoted savings are compared to a standard atmospheric boiler.

The savings with ODR and a Mod/Con using some form of water temperature setback, wether it is ODR or indoor reset is on average 49%. This is based on a study involving 10 schools.

The savings for a conventional boiler with ODR is 20 to 35%. This is based on HDD analysis done by a few of my clients. One boiler was not changed out. We added radiant heat and Tekmar controls and saved 25%. At my parents house we changed the boiler out to a Buderus and used outdoor reset. They saved roughly 30 to 35%.

In order for a Mod/Con to work properly it needs to run at low water temps below the condensing mark of 130 degrees. With outdoor reset on a system designed for 180 degrees you will often find that the system is over designed and only actually needs maybe 150 degrees on the coldest day of the year. 97% of the time the boiler will run under the 130 degree mark thus you should see the predicted 49% savings.

Mark E claims that he ran his boiler at 150 degrees and it used the same amount of fuel as when it ran with ODR and lower water temps. Something is wrong with that statement. It is not scientifcally possible. He should have seen huge savings in the condensing mode vrs above the condensing mode. I want to know why. Either his honeywell thermostat doesn't work well with ODR or the actual temps in the boiler were lower then 150 degrees even though the boiler was set at 150 degrees.

The important thing to remember is to not change your opinion as to how things work because of just on case study (Marks). It controdicts what happened in other studies.

The Mod/con gets its savings from three sources. One, the modulating burner is more efficient then atmospheric, two, the boiler can run lower water temps, and three at lower water temps the flue gases condense and the boiler recovers the heat from the condensate. All three add up to 49%. My guess is that each of the three parts is equal to aproximently 15% savings. If you run a mod/con at a setpoint higher then it can condense you should only save about 15 to 20% in fuel. Add ODR and you should save another 25% to 35%.

Mark should have saved 25 to 35% in the ODR mode with his condensing boiler vrs setpoint at 150. If he didn't, it doesn't mean that the science is wrong. It most likely means that something in the controls is not doing its job properly or that the controls operate the system differently then Mark understands. Mark should look over the results until he understands why it came out like it did. Maybe he didn't monitor properly. Maybe the controls operate differently then they are designed to.

Never change your understanding of science on just one study without looking deeper into things.

JR


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Uni R_2

Why 25-30%?

"The Mod/con gets its savings from three sources. One, the modulating burner is more efficient then atmospheric, two, the boiler can run lower water temps, and three at lower water temps the flue gases condense and the boiler recovers the heat from the condensate. All three add up to 49%. My guess is that each of the three parts is equal to aproximently 15% savings. If you run a mod/con at a setpoint higher then it can condense you should only save about 15 to 20% in fuel. Add ODR and you should save another 25% to 35%."

For #1 the higher efficiency doesn't come through modulation, it comes through the ability to condense. The MZ wall hung boiler has an AFUE rating of 95% - very efficient yet it doesn't modulate. 2. Lower temps... and yes this is where modulation pays off. I would say #3 is not having a big heat sink in the sky nor having to pull cold moist outside air in through the walls for combustion. I've heard that idle stack losses could account for 14%. It would be really nice to know what the change is in total for the lack of stack losses and not using the whole house as the boiler's air filter. That number would be interesting.

Mark has a modulating boiler. Just because a simple fixed firing rate atmospheric boiler can save an extra 25-30% without ODR, that doesn't mean that a modulating boiler will have the same savings benefit. Mark has stated his target temp is 150, but this may not be at all indicitive of his return temps which would show whether or not he is fully using the condensing capabilities of his T50. I would easily imagine that he is.

John Ruhnke

Years of research.......

Uni R,

I have read a lot of material. Seen a lot of projects. Based on what I know. According to a chart in a research paper I have Combustion efficiency savings chart that says Mark should be saving 15% by running much lower water temps in the condensing mode. I estimate that you gain another 10% added to that in Overall Efficiency savings. The ASHRAE paper backs me up and says aproximently the same thing. That is 25%.

This is what the science says. Once your boiler is in the condensing mode the rate of savings double for every degree you drop in water temps vrs atmospheric equipment. That means when you drop in water temperature on a condensing boiler (below 130 degrees), the savings are even greater then with an atmospheric boiler.

This is the oposite of what Mark thinks based on findings in his own house. Mark thinks you will save more by dropping water temps on an atmospheric boiler vrs condensing. Mark's findings are controdicting science.

Why?

JR

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Ken_40

JR,

Look down the thread a ways. ME explained why he has what he has, e.g., Both ODR AND a setback 'stat - which were fighting each other.

Apparently, you also missed the part about the "savings" being so marginal in well built envelopes that the cost of the 'stat cannot be recovered in a reasonable time frame.

Equally missed, is the problematic "flywheel effect" of radiant systems in general - all making night setback either moot, or economically costing more to have - than the benefit derived.

Selective science is not science at all lad. We must consider all the issues, not just the ones that are so obvious - as the one's you properly stated.

I do not regret having programmable 'stats. I regret they will not pay for themselves in a reasonable period of time, that's all.

carol_3

The problem is that even a small amount of unplanned-upon heat inside the stat messes up it's ability to control temperature tightly. Thoughts on anticipator in a second. The industry standard for a good thermostat is to keep the temperature within one degree of setpoint. The triac units have much more temperature swing than that--and here's the kicker--the more demand for heating, i.e. it's colder outside--the bigger the temp swing.

Now for anticipators. Triacs are found in some electronic thermostats and are a problem. Anticipators are found in mercury-bulb non-electronic thermostats and are a solution to a problem of residual heat in any system. So the anticipator is a little resistor (even sometimes called "heater") that makes the thermostat think the room's warmer than it is so that the heat turns off just a little early and lets the heat remaining in the system finish off the job without overheating.

Unknown

Hi Carol,

I'm curious because you indicate only two lines of thermostats, and I'm quite sure the Tekmar thermostats we use generate their own heat; we can see this just by holding them in different directions.

However, they appear to deal with this problem quite effectively indeed, we are aware of no issues whatsoever with discomfort in any of our Tekmar controlled systems. I believe Tekmar introduces corrections in their software, but I'm speculating there.

Any thoughts on that?

John Ruhnke

Its the ODR..........

Ken,

I can understand why programable stats don't work. All of those things make sense to me. You are right. Good science looks at the whole picture. Often there are rules that do bad things to offset rules that do good things.

I just wonder when Mark set his boiler at 150 did it run at 150? or less? I think much less. Which would make sense to me.

I find it hard to believe that his boiler running 150 degrees, outside condensing mode will save the same as running the boiler with ODR and under the range of condensing temps. Unless the control strategy operating the boiler was totally messed up.

I am still very grateful to Mark for doing real time monitoring. We will all learn so much from it.

JR

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Ken_40

JR,

we also have to be aware that a 150 outlet temp may be less detrimental than what the dT is. 150F out does not necessarily mean no condensing; especially if return water tems are low. Then too, the buck-and-a-half number may be the maximum limit setting, not average or even "mean" outlet temps?

John Ruhnke

Yes............

Ken,

I agree. Except, a Munskin requires a good flow rate past the heat exchanger or boiling water could damage the heat exchanger. Thus you need to keep that delta tee from getting to low.

JR

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ALH_4

and

firing rate is as important as water temps.

Ken_40

I agree that

generally low flow rates = high dT's but when you do copper radiant, dT's of 40 degrees and 5+ GPM's (or more) are the norm, not the exception (;-o)

In fact, high dT's have little to do with flow rate. Pipe diameter and load control those factors. Which is why P/S is such a beautiful thing.