set back thermostats on a steam system

Bob Giovannini

We have a 1 zone (thermostat on second floor hall) steam system (oil), with single and dual pipes depending on the room and radiator. House was built in 1874. This is our first winter in the house and was curious if it is actually more efficient to set back the thermostat at night or is it better to leave at a constant temp. I have been experimenting setting back the thermostat and it seems it takes a lot more time to bring the house back up to temp versus possibly just maintaining a stable temp.

Does anyone have similar experience?

Thanks!

ttekushan_3

Thermal mass of everything

OK. Here's the part that won't help much, but will give you an idea of why one right answer isn't possible. You have to take into account the thermal mass of your heating system (how fast it gets up to speed), the size of the heating system, the construction materials of your home (stone, brick, wood, solid masonry vs stick construction), your usual thermostat setting and the length of time you intend to set back the temperatures.

For the average homeowner, a radical setback doesn't seem like a good idea. But at least a couple of degrees can mean 10% less fuel during setback.

Here's the part that may help:

My rule of thumb is to find a day where the temperatures are somewhere around the midpoint of the design temp of your house. Generally speaking, if the system can keep the house at 70 degrees with the boiler running most of the time with an outdoor temp of 0 degrees, we can say that the design temp of your heating system and house is 0 degrees. So pick a day when its 30 degrees or so, and shut off the heat (or turn it way down). In about 2 hours look at what the temperature is. This is about the most setback you will want to use.

At least this has been a good starting point, in my experience. If it takes more than an hour to make up the temp, you might consider less setback. Every home/heating system/lifestyle combination will be a little different. You'll get a feel for it.

Kara

My setback is set at 10 degrees. I'm trying that for a while and see how well it works. It hasn't been cold yet and that's what I'm waiting for. I've a gut feeling that 5 might be better.

I need to put an hour meter on my burner and time the total burns over a set period. Someone suggested using an sweep hand electric clock wired into the burner as a cheap and accurate method of keeping the time. In a previous discussions most thought that big setbacks weren't very practical with steam.

Mad Dog_2

very good instincts Terry

said it all....you'll just have to find that "sweet spot" that Noel Murdough talked about. In any case, Deep set backs in a high mass systems rarely work out. Much like wet radiant installs (also high mass) these systems thrive!!! around a set point temp. Mad Dog






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Robert Giovannini_2

Thanks

Thanks to each of you who responded. Testing for past week does suggest a minimal or no set back is more efficient.

FJL

How Did You Test . . .

And what did you find.

Fred Harwood_2

Set Back

Personal note on my one-pipe system. Set the thermostat for the lowest comfortable setting and leave it alone, hopefully cycling twice an hour on calls. In baths, use a small electric space heater, or the one in the vent/light/heater overhead. Daily setbacks don't do much. Setbacks of more than several days pay dividends.

Hot tea is nice, as well.

FJL

My Set Back

I live in a four-unit apt blding. We set the t-stat at 70 from 3:15 p.m. to 11:00 p.m., when we use a set back of 62 until 5:45 a.m. when people wake up and the t-stat goes back to 70. We use another set back when people leave the building to go to work. It sets back to 62 from 8:45 a.m. until the children get home from school at 3:15 p.m.

The set back during the day is probably not really needed b/c the building gets a lot of sun during the day and the building temp doesn't really fluctuate too much, at least so far (mid-December). But the temperature does drop a bit for the evening set back when the sun is down.

The heat runs one cycle per hour. It seems to run a little less than once per hour to keep the t-stat satisifed when set at 70, and when it runs it will usually run for at least 15 mins until the t-stat the building is satisfied. (The t-stat is set to read the temp in one of the four apts). This is all from memory, so I might be misremembering things a bit.

In the morning, the boiler runs for between 45 - 60 minutes to satisfy the t-stat. On a really cold day it will run for 90 minutes. So I figure that I save a little bit over the course of an evening, except maybe not if it runs for 90 minutes on a cold day.

Maybe I should try running it with less of a set back, perhaps to 68.

RoyJack

Old house - Mixed System

My house is a variation on the original question and I welcome any comments.



I have an old house (1886) that had radiators on two floors. We moved into the house last July & I installed a brand new gas boiler last Sept. The radiators worked fine & I never had any trouble "hitting" my temperatures. However, the house was drafty. We remodeled the kitchen this summer & took out the radiator. In the interest of saving space (small kitchen) we installed a kick space heater. Since that required "changes" to my steam boiler to "step down & mix" the temperature, I decided to "go all the way" and install baseboard heat on the first floor. My expectation was that I would get a "wall" of heat all around the outer perimeter. I was however concerned that the baseboards would not provide sufficient heat. In fact, I objected to using "standard" baseboards (vs. high output) because I was concerned my home would be too cold. Contractor assured me that he had done all the calculations & they would "stand behind" what they did. That's when my problems began.



I have 3 zones: 1st fl (baseboards) 2nd fl (steam) & kitchen (kick space). 2 of my 3 zones work fine. The 1st floor has been nothing but trouble. After incorrectly installing the t-stat to measure water temp on the baseboard return (instead of correctly measuring demand) I then could not get sufficient heat and often heard "gurgling" sounds when I was supposed to be getting heat. Another visit "moved" the demand in the boiler, because it was set too high and would draw air when the water level in the (steam) boiler fell! [OBTW - in between when this system was installed and now, I have installed brand new front and back doors with a full glass storm door on the front, AND I have had my entire house insulated with blown in (cellulose) insulation.] My house is now colder than it was last year.



I prefer to sleep "cool," so I like to set back temp at night, and for 9 to 10 hours during the day, the house is empty. Virtually every web sit I found on this issue (including state and federal government websites, Energystar, etc.) ALL say that you will save energy and money by setting the t-stat back. I start at 0430 demanding 72 and go to 60 at 0715. I then go back to 72 starting at 1530 and drop to 66 at 2230. The contractor came in and said it would cost me MORE money to do that because I would have to spend extra to get the heat back up to 72. He is now insisting that I should not lower temp below 68. Just to see how his system worked, I did. It takes me an average of 3 to 4 hours to move from 68 to 72 and when I questioned his "reasoning" that I "should not set my t-stat back more than 4 degrees," he referred me to THIS website to support his claim that everything else I found was wrong, and that his advice - never more than 4 degrees - is correct. Really?? Since the system is supposed to shut off when it hits the demand temp (72 for me) how can it cost me "more" money? Also, is it reasonable to take 3 to 4 hours to go up only 4 degrees? The kick space works fine in the kitchen and the radiators on the second floor pump out the heat, but I am still cold on the 1st floor. Does anyone think I should have insisted on the high capacity baseboards? What should I do now? Any suggestions?



Roy

Jamie Hall

for what it's worth...

after years (literally) of fine tuning and measuring, I have found that, for my steam system, a setback of more than 4 degrees cost me money and comfort.  Ten degress would have taken all day to bring back to temperature.



I now run with no setback, at a space temperature of 65; the place is now a museum (used to be a "cottage" in the Berkshires) and I have noticed practically no difference in energy use between the 4 degree setback and what we are doing now.

Jamie Hall

And some further thoughts, specifically on this one...

On setback.  Mad Dog and Terry nailed it.  You are dealing with a high mass system (even the baseboards are relatively high mass).  In any such system, you are heating objects, not the air, and they take time and energy to heat.  The recommendations for deep setbacks which you have found on the various "official" web sites are intended for forced air systems, where you are heating only the air -- which holds virtually no heat at all.  This means that you can change the air temperature with relatively little energy.  On the other hand, it also means that the objects (including the house itself) will actually be at a temperature somewhere between the upper and lower temperatures.  This is one reason why it is often possible to be as comfortable in a steam heated house set at 65 as in an air heated house moving between 60 and 72.  The deep setback with a high mass system costs you money -- with the setback you quote, lots of it -- because you are heating all that mass.  Your technicians advice is absolutely correct -- for steam and hydronic systems.



On the system itself.  Well... at least the steam side of the system is still working well!  The hydronic side... could be any one of a number of problems.  You need to pay attention to the temperature drop between when the water heads out to the baseboards and when it comes back.  The circulator(s) should be sized so that that drop is around 20 degrees or so.  You also need to find out what temperature water is going into the baseboards -- and you may need to raise that, to get the heat output required.  It almost sounds as though you are taking boiler water directly and running it through the baseboards.  If this is the case, you may find that the boiler water just isn't hot enough at the location where you are tapping it.



I have to admit that I find hybrid systems of this sort very iffy, as they are so difficult to control and get in balance, if it can be done at all (since the nature of the demand from the steam and the hydronic is so different). 



I might also note that the boiler was probably sized based on the radiation which was there -- if it worked well, that's quite likely.  Now that you have removed all that radiation, that boiler is way oversized based on the steam demand.  This isn't going to help getting the system to heat evenly...

DavidK_2

steam setbacks

I have to admit, this advice to not have much of a set back with steam heat is a new one to me.



I can understand the comfort issue. It takes a little while to bring the house back up to temperature. About an hour for me if the house has actually reached the setback temperature. I've actually considered getting a programmable thermostat so I could start bringing the house up to temperature about 1/2 hour before we get up.



I still do not understand how not using a setback can use less energy.

The house loses energy at a rate that depends on the difference between inside and outside temperature. The smaller this difference, the less energy the house loses.

If the boiler is cold, it also has less standby energy loss.



I understand that when the setback ends I have to use energy to bring things back up to temperature. But how can that energy be more than what I would have used to keep a constant temperature? If the house starts and ends at the same temperature, haven't I used less energy if the house has lost  less energy (because of the setback)?



I sleep better when it is cooler at night - probably an evolutionary thing since that is the environment we evolved in. I run 68 in the morning, and evening. I run 60 at night and when nobody is home. It takes a very cold night to get my house down to 60 - so I'm probably not actually using the full 8 deg setback except for maybe a dozen very cold nights.



Maybe I need to find two days of similar weather - and take gas readings with and without a setback. But I'm not sure 2 days would be enough. Probably a timer on the burner would be more accurate than a gas meter reading (and would eliminate the DHW heater)



Just trying to live and learn. Thanks for your help.

RoyJack

The Numbers / Logic does not make sense

For the record, I am using set back t-stats on all 3 zones.



I believe I understand and follow the difference between forced hot air (or "hydro-air" as some systems are now defined) vs. steam vs. (hydro) baseboards. The concept of a mass losing energy / heat is quite clear. However, as was noted by DavidK, the energy "loss" is a function of the total difference between the temperature set and the overall outside temperature. I don't see how you can possibly spend "more" energy bringing a system "back up" to a set point than you would spend maintaining that set point. This is especially true when my system - and presumptively all systems - are designed to turn off once the set point is reached.



If I set my house at 70 and the outside temperature is 30, my house will "lose" heat / energy. How much is a function of a lot of variables (such as how much insulation I have, energy gain from the sun, other sources of heat within the house, etc.) but at some point the house will "stabilize" at a given temperature where the energy in the house can maintain a fixed temperature at some number (presumptively) higher than 30. Maintaining 70 throughout that time "costs" me the same amount of "total" energy as it would if I immediately began re-heating the space the instant it hit the so called "stabilized" (let's call it base) temperature. That would cost me roughly equal amounts of energy. Now, the point of the discussion is that once my house cools to the "base" point, it is NOT going below that point, and the longer it stays at that base, the more money / energy I save because I am not "adding" heat / energy to the system. If - because there is no one in the house and so there is no reason to add heat to keep someone comfortable - I can leave the house at the "base" level for say 4 or 5 hours, I have just saved the energy difference between the base level and the higher level (in this example, 70). That seems to be straight physics.



I agree that my boiler will not run as constantly nor as continuously throughout the day simply "maintaining" the (higher) heat level, but it will run. Heat will "flow" to the colder level until it equalizes. There is no question and no disagreement that because the "mass" of the house has been allowed to cool that I will add "more" energy to bring it back up than I would otherwise have added had I only been "maintaining" the set point heat. However, that strikes me as nothing more than a perception, and not the reality. The reality is that my house constantly loses heat. My boiler is tasked with maintaining a certain level of heat. The greater the differential between what I am demanding and what the outside temperature is, the greater the energy demand. By lowering that differential (say by setting the demand temperature back) the smaller the differential and the less energy that will be used. The longer that state exists, the more money I save over what it would have cost me to maintain the higher differential.



When I return to the house and I start adding more energy to bring the ambient heat level up to my desired set point, to the extent that the "mass" of the house has cooled, I need to add heat. However, the "mass" of the house is constantly "cooling." That is the very nature of the transfer of energy. Higher energy always flows to lower energy until they equalize. The greater the differential, the greater the flow. Given that, my system adds heat / energy until I "hit" my set point - then it stops. If I still have not added sufficient energy to the "mass" of the house, it will come on again more quickly than it would have if I had maintained the mass at the higher temperature, but that does not change the calculus of the overall heat loss. The fact that is cycles back on again more quickly does not change the fact that as long as there is an energy differential it needs to add heat. How and when it adds that heat will vary, but it still needs to add heat.



Maybe I slept through those physics classes, but I don't see how anyone spends "more" money lowering the differential than they would have maintaining the higher differential.



Also, for the record. I am not running boiler temperature water through the baseboard. The steam system demands (approximately) 212. The baseboard system is set to demand 200. I agree 100% that an important measurement is the difference between temperature of water into the baseboard and temperature of water out of the baseboard as that measures how much total energy was transferred. However, temperature alone is not the issue. The calculation would have to include total "volume" of water to accurately measure heat transfer. Finally, the system has a "plate" that transfers heat from the boiler to the baseboard water system.



I do not want to have to maintain a "single" set point for heat. The installers charged me extra for "set back" heaters. I do not have a hand held laser heat scanner to measure the exact temperature of the baseboards, but my (totally unscientific) assessment is that the baseboards do not deliver consistent heat, and they seem to "cool down" when they are supposed to be delivering "maximum" heat to reach the "demand" temperature on the t-stat.



I have invested a lot to be warm. Each door replacement cost me several thousand dollars, and having the whole house insulated (the contractor estimated it would take 37 packages of "product," and it ended up taking a total of 52!) MUST have improved the ability of my house to maintain heat. Is it absolutely "drum tight?" Of course not. It is over 120 years old and there is no such thing as a straight line or a perfect right angel in my house. But is a lot tighter than it was last year, so I should be at least as warm.



Roy

Jamie Hall

OK, I give up

20 years of records support my position, but hey -- who am I to argue with the theorists?  I'm just a knuckle dragging building superintendent...

AlexR

don't give up!

I agree with the above theorists, so I'd love to know why we're wrong.  Reasons I can think of might include



  - the boiler is less efficient coming off a deep setback. Though actually, I'd  guess the boiler is more efficient when the contents are cold...



 - deeper setbacks cause more thermal cycling of the boilers, pipes, radiators such that they fail sooner



 - the long recovery time from a steam system bothers the occupants and they end up setting the thermostat higher than they would have with a shallow setback, thus wasting more energy than the deep setback saved.



 - heatflow from a house is more complicated than just k*(inside_temp - outside_temp)



Disagreements between theorists and experimentalists are always a chance to learn something.

RoyJack

Who to believe

Sorry, Jamie, but I am the guy in the middle. I am neither a "theorist" nor am I someone with your years of experience. I am just trying to understand the process.



Saying that it costs me more in terms of total energy / heat (and telling me that you have 20 years of data to "prove" it) doesn't explain it to me so that I can understand it. I don't mean to insult you in any way. I don't know what your data is or how it was arrived at, but at this point you are one person making this claim. Your position is at odds with virtually 100% of all of the websites I have found when I go online to research the topic such as this one from EnergyStar, http://www.energystar.gov/index.cfm?c=thermostats.pr_thermostats; or this one from Madison Gas and Electric in Madison, Wisconson http://www.mge.com/home/saving/thermostat.htm that specifically addresses the claim that "it costs more to re-heat" a space.



I don't claim to "know" any of this, I am just trying to learn. However, at this point I will have to respectfully disagree with you.



Roy

David Nadle

Physics vs. perception

If your first floor can maintain 68 on the coldest day of winter then your baseboards are adequate. In theory the physics should work out as you say, but like others have said above, a radiant system basically heats the other surfaces in the home first, and the air eventually comes along. This is why it can take a long time to feel comfortable coming out of a deep setback. The alternative is to heat the air and blow it around, but most people here think that's overall an inferior way to heat your house.

I'm not surprised it takes 3-4 hours to recover 12 degrees. A system that can recover 12 degrees in an hour would be way oversized. You may have a better experience with deep setback if you get a VisionPro thermostat. Instead of setting the time at which you want to start recovery, you set the time at which you want the house to be at the setpoint. The VisionPro has an adaptive algorithm that uses a running average to predict when to start recovery so that you reach the set point at the set time. However, I think the result would be that your setback period would end hours before you wake up, and you wouldn't see the expected big savings on your gas bill.

ttekushan_3

long recovery times

I don't think there's anything wrong or anything less efficient about running the heating system for extended runs. Indeed, this is where the boiler's combustion efficiency really stabilizes at it's maximum.



However, the whole theory gets blown out of the water (sorry) if the burner starts short cycling if the heat from the boiler is not effectively being transferred to the heated space. So your steam side is good.



I just can't see why the kickspace heater works so well and the baseboard won't get hot. Is there a tempering valve/ balancing valve installed to lower the temperature of the water going to the baseboard? I'm thinking that the baseboard loop may be either getting air from the boiler water when the boiler is supplying steam or at least allowing steam into the baseboard supply piping and perhaps creating localized steam condensation and cavitation of the pump and/or enough vacuum to stop circulation.



What's keeping the water from returning to the boiler when the circulator shuts off? Are both supply and feed run well below the boiler water line? Is the circulator on the return or the supply? Can the circulator run without the boiler in "steam" mode and if so, does it act differently? Does the water from the loop return to the boiler when the boiler is off? It shouldn't if no air or live steam gets in there. Is there an air eliminator at the baseboard somewhere? Is the loop isolated with a strainer? It get clogged with sediment before long if using water straight from the steam boiler. Steam systems are open to the atmosphere and allow corrosion of the cast iron. Not a big deal ordinarily but a big deal to water circulators and air vents.



Is the boiler water level stable while steaming? All the new piping work will contaminate the boiler water and when it steams, the water level may be surging and allow the baseboard circuit to lose prime or gather enough air to cause trouble. A boiler skim cleaning will help this. Also the pump can be cavitating due to the high water temperatures and utter lack of static water pressure. Don't forget, a circulator is expecting to work in the environment of 12lbs static pressure at the very least and water temperatures well below boiling. Water systems can run up there to 200+ F but the pressure is usually > 20psig at that point! You've got virtually no compressive pressure at all around that pump.



These are some of the many reasons that running a water loop off a steamer without a heat exchanger is a problem. Of course, there may not be any provision for a water coil in your boiler and even if there is, it won't be large enough to heat a whole floor of the house.



I would have suggested running cast iron baseboard directly with steam, or at the very least, I would have suggested steel fin tube baseboard running off steam. I see this frequently enough, with motorized globe valves performing the zoning function. I know the argument that the water zone doesn't require the boiler to make steam to heat up . I think we know how thats working out for you.



Sooo... Check the boiler water first and make sure there's no boiler water line trouble due to contamination. Then post a few pictures of how this water loop is actually piped to the boiler.



-Terry

DavidK_2

Roy, if your house is cold

you probably have to have somebody come in and look at that 1st floor baseboard - sounds like it is not working properly

DavidK_2

Another possibility

If the system is balanced to work properly when it is maintaining a constant temperature, that balance might work when from a cold start. This could overheat parts of the building, resulting in higher energy cost.



For example, perhaps usually you need a big vent on a radiator so that steam gets to it during the relatively short fires required to maintain temperature. But in a cold start that radiator might now be over vented. So you could be over heating that room, while the thermostat room is still not warm.



In an ideal world the balance for constant heat should be about the same as the balance for cold start - but things are rarely ideal  . . .

Jamie Hall

Well... I'll comment again...

I'm not sure that there is one good theoretical reason why a deep setback will be less fuel efficient, overall, than a shallow one (such as suggested by Terry and MadDog).  The shallow setback is slightly better than keeping a constant temperature -- but in my situation, I have to keep a constant temperature (the curators, particularly of the musical instruments, get badly warped if the temperature varies).



However, a few possibilities.  First, coming off a deep setback requires a run time much longer than that required to fill all the radiators.  This means that the system must cycle on pressure (1 ounce to 9 ounces) and it would seem reasonable that this would use slightly more fuel than the equivalent constant runnng -- but I can't modulate the burner (I see this in another application -- my car gets significantly better fuel mileage if I drive a constant speed vs. speeding up and slowing down, maintaining the same average).  A shallow setback just barely reaches cut out, and a constant temperature only reaches cut out in rather cold (say, 0 F) and windy weather.  Second, in colder weather neither the radiators nor the boiler ever get "cold".  Near room temperature, yes, but never cool to the touch (this isn't true in warmer weather -- but then, in warmer weather, the system only runs two or three times a day).  And then, in my situation, there are some huge thermal masses to heat up -- several very large chimney stacks, for instance.



I'm sure that the optimum setback is different for different buildings -- and probably for different systems in the same building.



Oh -- and one other thing: in my book, the ten most terrifying words in the English language are "We're from the government, and we're here to help you"!

nicholas bonham-carter

to set back or not to setback-that is the question!

friends of mine, who have bought new cars often proudly point out the EPA mileage sticker on the windshield. that sticker lists 2 ratings for consumption: city driving, and highway. of course, not only are objects closer than they appear; but also your mileage may vary from the ratings! the most important part of the ratings is that "stop and go" driving will make the city consumption higher than the highway consumption.

most pros here, equate the use of setbacks as being "the stop and go" of the hydronic/steam world, with consequent higher fuel use.

it would be interesting to devise an experiment, using an hour-meter on the burner, to answer this question. one could clock the burner for one of the setback periods, and then raise the temperature 10 degrees, and clock it for just the time needed to bring it up to that point. finally clock the burner for the same amount of time at the higher temperature. would the difference in run-time of low and high offset the run-time needed for the 10 degree rise? finally how long a setback should be chosen before you have real savings? we can all see that a couple of weeks at a lower temperature will probably save fuel, but that a series of alternate hourly periods of high and low will use more fuel.--nbc  

RoyJack

One Boiler, but separate systems

David and others. I may not have been clear on my description. Since this is not my area, I apologize for any mistakes I may have made in the description.



One clarification: When I say it takes 2 - 3 to sometimes 4 hours to raise the temperature to my "target" level, I am talking about going from the 68 degrees they are insisting I keep my temperature at, to the 72 degrees that I want my house to be at. That is a rise of 4 degrees, NOT 12. I feel the system should be able to accomplish a rise of 4 degrees in under 2 hours. I am - to accommodate the heating company's request to "check" the system - keeping my lowest set temperature at 68. This is warmer than I would prefer at night when I sleep, and I believe it is a waste of money during the day when there is no one in my house from 7:15 AM until around 3:30 or 4:00 PM (or later). I believe I should be able to set my t-stat back more than 4 degrees. We have had some warm weather the past few, but we are just entering a cold snap starting tonight. We shall see how this system performs.



I have a single, gas fired boiler that was purchased last year for my steam heat. When that system was installed, I also had an "automatic" water fill installed. The water in the glass that shows the water level is pretty much clear, as I have personally bled off sediment from the system and I keep an eye on it to make sure it stays clear.



The baseboard (I wish I had thought about steam baseboards now!!) is a water (hydro) system that is installed off of the main boiler. When it was originally installed there were apparently two mistakes that were made. The t-stat that measured the temperature of the water in the baseboards was set to measure the return temp rather than the feed temp. Until that first mistake was corrected, I could not turn the heat off.



The second mistake was that supposedly the unit that "draws" (I may not be accurately describing this) the water out of the boiler to heat a PLATE that heats the water in the baseboard system was installed (physically) "too high" up in the boiler, so it occasionally "pulled air" when the level of the water in the boiler fell below the feed because of the steam. When the system was supposed to be running to produce heat, I would hear "gurgling" and "dripping" noises. Since the baseboard is supposed to be a "closed" system (??? I think??) I don't know how this would cause air in the baseboard system, but since the pump (?) has been lowered, I do not hear the noise.



There appears to be a "transfer plate" of some sort that I am told "heats" the water in the baseboard system. The baseboard system appears to have a pressure tank on it that feeds both the baseboards and the kick space blower in the kitchen. It is my understanding that the temperature of the water in that second (??closed??) system is set to be 200. If my second floor is not calling for heat and neither of my other two zones need heat, the water temp will move to 200. If my second floor (steam) zone is calling for 212 it will do that, and if neither of the other zones needs heat, the circulator pumps will not come on. If all 3 zones are calling for heat, the main boiler goes to 212, and the water circulated to the plate will heat the baseboards / kickspace heater ONLY to 200.



The head of the company came out & spent a considerable amount of time (2 + hrs.) "checking" the boiler and using a laser heat gun to measure temp in the pipes. He also plugged the 5 holes where the radiator pipes used to run from the basement to the first floor. When the system was installed, I asked (before it was installed) if they were installing "high capacity" baseboards. I was told "No," and the supervisor who did the original quote came down and insisted that - based on his calculations - I would get more than enough heat with the "regular" baseboards. I don't know the (heat) difference, but my unscientific, "gut" feeling is that I should have insisted that the work not go forward unless the high capacity baseboards were installed. (I think I now know why the two companies quotes were so different! My bad.) The supervisor insisted that they would "Stand behind" their work, but I don't feel that telling me to keep my heat no lower than 68 is acceptable. I am still waiting for them to respond.



Roy



PS: Jamie, I couldn't agree with you more. The LAST think I want is "help" from the government.

RoyJack

Start and Stop Set backs and fuel economy

Nicholas:



It seems to me that using the fuel efficiency example the large set back would be MORE efficient than maintaining a fixed temp. Just as the A/C folks caution against installing too large a unit (because it constantly cycles on and off and does not then "run" efficiently) it strikes me that this is similar.



ALL heat is constantly transferring to a "colder" spot. So, "maintaining" a constant "level" differential - especially in a steam system where you need to add a lot of energy to generate the steam that then transfers heat to the space - will actually cost you MORE money. When I drop my temperature a significant amount - say 10% - 15% for a period of say more than 5 - 6 hours, once the system comes on to bring it back up to the "higher" target at the end of the set back period, I would assume that the system runs (continuously) until the target is reached. That strikes me as more efficient than cycling on and off all day long. Isn't that how a system works? If I am at 62 and I want to go to 72 doesn't my boiler "run" continuously until my target (72) is reached? That's how I thought it worked.



Roy

David Nadle

Clarity

My understanding is that most of the problems you mentioned have been corrected and now the problem is you feel recovery time is too long. Right?

I don't know that much about hot water but I'm surprised that the return temp is not factored in to the controls. It seems important for determining the correct flow rate. If your return water is 190 and you don't know it...

Maybe you need more baseboard, but maybe you don't. I'd give them a chance to tweak the controls first, but I agree that you should be able to keep the house at 72 if you want to, and you should be able to recover 4 degrees within 2 hours. 

Mike Kusiak_2

Deep setbacks and cycling on pressure

I have a feeling that the physics and Jamie's practical observations are both correct and do not contradict one another.



You cannot argue that the heat loss of the building will be less when it is maintained at a lower temperature during setback. The disagreement seems to come from the question whether less fuel is used to bring the temperature up from setback than would be used if a constant temperature was maintained. Here is where the practical reality comes into  effect. With a steam system coming out of a  deep setback, the run time may be so long that the burner may start cycling the pressuretrol, and may continue to short cycle until the thermostat is satisfied. Cycling the boiler is in this manner is inefficient and if it continues long enough may increase the fuel consumption to the point that it negates any savings achieved by the setback.



So it seems to me that the most efficient setback for a steam system may be one which allows the thermostat to be satisfied without causing the burner to cycle on pressure.

Mike Kusiak_2

Thats the problem

IF you are at 62 and want to go to 72 with a steam system, most likely the boiler will NOT run continuously, but at some time during the period will start to short cycle on pressure. At the beginning of the period the system will be full of air, and the full steam  generating capacity of the boiler will be used to fill the piping and radiators with steam. At time continues, the radiators will condense the steam and reach a temperature of 215F at a pressure of about 1 PSI. At this point, the system  cannot accept any more steam unless the pressure rises. With the resulting rise in pressure, the pressuretrol will respond, shutting down the burner. The pressure drops until the low limit is reached, again firing the burner increasing the pressure and the cycle repeats. This rapid cycling is not very efficient. If the boiler and radiation were exactly sized so that all the steam capacity generated by the boiler could be fully condensed, or a modulating burner was used, then this cycling would not occur. In a real world home steam system however, the boiler is typically oversized and an on-off burner is used, so the cycling on pressure has to be tolerated.

Jamie Hall

Thank you, Mike

looks like you and I and MadDog and Terry are all on the same page: under more or less average conditions (say about half way from your design temperature to your inside temperature) the ideal is to have the thermostat and the pressure control come to the conclusion that it's time to stop at the same time.  Warmer?  The thermostat wins.  Colder?  You'll cycle on pressure some.  All depends on your particular system, your particular house...