Setbacks for One Pipe Steam

Cast Iron

oh, man. Now I am confused. I'll just wait for you guys to sort it out. It's an interesting discussion.....

Cast Iron

Should a Setback be used for Steam systems

Quick Question:
Is it more efficient to turn down the t-stat during the day and at nights for a single pipe steam system, or is it better to leave at the same temp. Right now the t-stat calls for 67 when heating is required, ie morning hours and evenging, and at all other times, it is set to 58 degrees. We just had insulation blown in, did air sealing, and previous owner did new windows. So the house is pretty tight.

67* 4:45AM-7AM
58* 7A-4:45PM
67* 4:45P-11P
58* 11-4:45P

Any thoughts? I was thinking that keeping all that iron warm instead of heating it every time might make a difference in energy usage.

Thanks!

Tom R.

Quick answer

Setback always saves.

Christian Egli_2

A major setback

Tom is absolutely right, the physics are on his side.

And the deeper and longer you go with your setback, the more you'll save.

Steam heat is particularly well suited to any setback you want because it is quick at recovering any temperature you want, also because it immediately provides good usable heat you can feel right away, and because you don't have to necessarily be worried stiff about freezing your radiators.

Nothing but advantages.

gerry gill

really? does the physics

take into account mean radiant temperature?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Mad Dog_2

I'm with Gerry..............................

Yes, you can setback a bit....3-5 degrees during unoccupied hours with steam, but anymore than that is usually a game of pedal-to-the-medal.....is THAT fuel efficent? Mad Dog

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Cast Iron

Hmmm... that's what I was thinking. All-thanks for the feedback.

I have enjoyed reading the postings here quite a bit. I have gotten my steam heat to be silent and fast thanks to all of you. For what it's worth, I want to make it as efficient as possible.

Thanks!

Bob W._3

Eric, I am not using setback because my home is all masonry. Swampeast posted a study that indicated there were little or no savings in large mass homes. If you have a frame home the results may be different.

Tom R.

At least

During the idle periods, you have less chimney losses with the boiler water at a cooler temperature. No two dwellings are going to give the same results, but I would think the older the equipment, the more oversize the boiler, the less the insulation, the more often you do not approach design temp., the more setback makes sense. At the extremes, you could keeping the building at 95* all year or not heat it at all. The difference in fuel consumption would be drastic. Setback gets you somewhere inbetween.

Lurker_2

I tried testing in my own home

I basically measured fuel usage on days with a steep steback (roughly the same as yours except that I had it at 70 degrees at the high points, and I wake up later than you do. . . ), and then turned off the setback and measured the fuel usage. I did this for about a month half with setback and half without, correcting for degree days and so forth, but eventually I stopped because it was fairly obvious that setback was saving me a lot of fuel, and I didn't want to pay the additional fuel cost to experiment.

Of course, it was more noticeable in my home since it has basically no insulation.

-Michael

Rodney Summers

Another setback to comfort

Setback is a scheme to provide savings on the heating bill. That's the only objective and it's obvious. When the resident does not directly pay for the fuel, you all know the scenario, thermostat at 95F and windows open.

For X-treme setback and extreme savings, all you need to do is turn the heat completely off... Moderate setback will provide moderate savings and no setback provides no savings. The principle is about as simple as lowering the thermostat, with setback there is just an ingenious time component to it.

So what about comfort? Oh, was that important?

Setback is not meant to improve comfort.

On the other hand, a reasonable setback will not harm comfort in any way and will provide reasonable fuel savings, like 3 to 5 F. But if you can tolerate more and if you value savings more than comfort, go for it.

I like the pedal-to-the-metal description, it's exactly what an ample sized steam boiler can do and putting full power to a boiler is not a source of inefficiencies the way it is in accelerating a car. In filling a home with heat, only heating beyond the desired indoor temperature causes inefficient operation (and that overshoot is what outdoor reset prevents)beyond the system inefficiencies.

How do you most easily boost mean radiant temperature? by placing a steaming hot radiator in the room, the MRT is instantaneously affected. Next, the placing of a radiant floor works the same way, less hot, more surface, same result.

The trouble is, floor heat is less quick at reacting than steam is, so you can't be as loose footed in timing your setback.

It can be worse, though. With forced air, objects rely on air temperature to get hot. On deep setback you get cold drafts and indoor wind chill effects. All together, with hot air heat, comfort will decrease more than with hydronic heat for the same setback.

There, I said nice things about steam heat.

All I really wanted to do is knock out the argument that setback actually causes an increase in fuel usage, because that's impossible. I would also argue that steam and radiant gas heaters are the systems that can yield the biggest savings from a setback scheme and at the least loss of comfort.

Anecdotal evidence:

A changing room in an otherwise unheated building used to be heated with a forced air gas unit hanging from the ceiling. The heat used to have to be turned on a long while before people would use the room, and still only the seats near the air outlet had some semblance of comfort. Cold walls, mild air, low MRT.

We added a gas radiant tube of half the power of the old air heater. This made an enormous improvement in comfort (that was the goal). The main advantage was that now, anyone using the room at odd hours could flick the switch, turn on the fire, and within seconds enjoy the heat. Cold walls, cold air, one very hot source, bingo, high MRT.

The surprisingly big difference came with the heat bill. The control strategy had been changed from keeping the room constantly at mild temperatures with a timer to boost heat in anticipation of occupied times (minor setback) to simply turning it on and off following occupancy (extreme setback). This was much better because occupancy couldn't really be predicted . Nothing but bonuses.

Two big changes: 1) the switch from hot air to radiant 2) the extreme and flexible setback. These provided 1) much improved comfort and 2) saved fuel. Converting to steam heat would have been just as cool.

The hot air unit is still there, the radiant system was initially meant to boost comfort on top of the air heat, and what I did not predict is that now the room is plenty comfortable that no one turns the hot air on anymore.

Isn't that a happy ending?

JohnNY

What changed???

I've been going to IBR seminars and manufacturers' classes for about 20 years now.
The official line on setback was, for years, a 3-4 degree setback maximum, and not advised at all for steam during a 24 hour period.

Suddenly, this is not the case?

Why does this conversation always involve people's opinions? Where are the irrefutable studies?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Tom R.

If

If setback doesn't work, then Honeywell, W-R, Powers, ITT, and all the rest have been ripping us and large building owners off for $billions. To anyone who is not a believer, do as the gentleman earlier did. Try it. You'll like it.

Dave DeFord_3

A question I have not had answered...

If I understand this issue correctly the heating system replaces the BTUs lost to the atmosphere. If this is the case, I can see some advantage to set-back - but not a lot. The only efficiencies I see are a small decrease in the heat loss through the envelope due to a smaller differential between inside and outside temp. The only time this loss would stop is when the inside and outside temps equalize. This would not happen during a 24 hour period. A small increase in the heating plant efficiency (of whatever variety) due to longer run times when the temp is coming back up. The upshot is that you have to replace every BTU lost with the heating plant and I don't see the change in the loss rate and the efficieny of the heating plant giving the claimed double-digit savings. As the other poster stated where is the research. I know from personal experience that it takes my house about 18 hours to recover from a 20 deg. setback when I leave it for an extended period of time. Anybody have any thoughts?