Setback with Steam...Revisited.

AdmiralYoda

I used to use a large setback way back when I didn't know better. 68 degrees during the day and 60 at night and away at work. My rational was...keep the heat off at night and when I'm away at work, and have it at 68 when I'm active inside the house.

My thermostat was smart enough to turn on the heat early enough to have it at 68 when the set time was chosen. It didn't really overshoot unless it was warm out.

My boiler is 40 years old and my rationale for NOT using a setback was to minimize wear and tear on the boiler parts. My boiler is oversized and will short cycle on pressure. So once a minute it would cut out and cut back in once the radiators were fully hot. I saw no difference in fuel usage, maybe a little savings actually by not having the large setback.

But I have been wondering....would a small setback save some fuel? Say 2 degrees? This has always been a curiosity of mine. I prefer it cooler at night anyways and if I can save a few bucks why not! The moving parts in the boiler will have to work a bit more but that's about it. Thoughts?

Jamie Hall

Grey area. I do use a two degree setback for Cedric. I don't have anywhere near sufficiently reliable data to tell me whether it saves anything -- and I don't know anyone who does.

Why two degrees? Well... three degrees and he has to run long enough (like an hour) that he shuts off on pressure. That annoys me. Two degrees and he doesn't do that.

dabrakeman

I tried to address this with data last year. Link to a discussion and one of my posts below. Bottom line setbacks do save total burn time and thus money as long as pressure build and cycling on pressure is avoided. Less total temperature differentiation between the outside of your house and the inside the less energy loss. When objective data agrees with theory, I tend to believe it.

the below from discussion: https://forum.heatinghelp.com/discussion/comment/1687153#Comment_1687153

@Nicolas bonham-carter I wish data supporting the repeated claim that setbacks do not save any energy would be shared. As much as I respect all the experts here I keep hearing this but never see any data supporting such claim other than the correct fact that if recoveries leads to pressure build and short cycling any savings would be eliminated and extra wear and tear on vents and such would occur. I continue to emphasize that to benefit from setbacks a recovery must be executed without causing such pressure build by which there are numerous methods discussed in this forum. I just presented one which works for me even with a 30% oversized boiler. I think it is arguable that more energy is lost to the environment with a larger average inside to outside temperature differential than a smaller one. This is just simple conservation of energy. In 2019/2020 I ran the entire year with constant hold temperature and in 2020/2021 switched to a setback strategy with same constant temperature during normal prime home occupation time period. Data was plotted for each month total cuft of gas use vs total HDD/month.

The main vent location had been previously debated so a few years ago I decided to start my own experiment. I was running constant hold temperature for the entire winter of 2018/2019 with the main vents back at the boiler at end of the main extension. Data was plotted for each month total cuft of gas use vs total HDD/month. 2019/2020 only change made was to move the vents to the actual end of the mains.

A plot comparing the strategies should be attached below. I understand no data is perfect and HDD data (in my case 1.5 miles from my house) does not reflect variables like wind or solar heating but I don't think it is a bad attempt at quantifying potential improvements.

This poster was looking for potential ideas to save heating costs. These have been successful for me.

PMJ

At the end of the day the total demand is directly related to the net difference between inside and outside temperatures. This is what determines how much heat leaves the structure and therefore how much needs to be replaced. So fundamentally setbacks reduce total demand.

I do it not to save money but for exactly the reason you mentioned. Slightly cooler at night, and, the subtle encouragement for people to go to bed. Properly done I do think it saves a little, nothing dramatic.

If in recovery your system runs a lot at pressure this is definitely a negative and can possibly even end up costing more than continuous temperature. The solution I used for that is extended recoveries (as in 6 hours or so). No one noticed the lower temperature as radiators were always warm and radiating.

Eliminating pressure altogether in all circumstances requires more than a standard control offers in most cases. I was reminded of this recently because I finally added a bypass switch on my control so that a technician(should my wife ever need one) could with one switch bypass my control and return the system to original Tstat/Vaporstat control. I made the mistake of going to work leaving the switch on "original control". My wife was not happy when I got home that evening. She said every time the boiler came on the radiators filled all the way, got blazing hot, and over shot the thermostat setting. Then, there was a long wait during which time the radiators got dead cold before the next firing. I went to the boiler room, saw the switch and realized what had happened and returned to apologize. I said she just spent the day running the system like it was when we moved in and asked if she remembered how that was. She said she did, and added that it was awful.

For the record my boiler is well matched by the specs to the system at 1000 EDR. I watched a cycle myself and the boiler ran until the tstat was satisfied, the vaporstat did not trip though it was set a low as it will go. But by then the radiators had way more steam in them than was needed for the conditions which overshoots some amount and produces a very long wait till the next firing. I've said many times (without stirring much interest) that these systems were not designed for boilers to run on high until the tstat is satisfied. I've also said the the most even heat by definition would be only when the radiators are the same all the time. Anticipators, smaller boilers etc. can help, but nothing comes close on an intermittently fired system to simply stopping burns at a target fill level some small amount more than will heat the place if filled that way continuously. That amount by the way isn't even 1/2 full on my system. A simple temp sensor on a remote radiator to tell when the system is filled that much (and also when enough heat has left the radiator that another firing is needed) makes all the difference and is so easy to do. That sensor plus a couple of fixed timers then create cycles that maintain a partial fill level, and produce burn/wait times that vary with the demand. Radiators are never blazing hot nor ever cold (except in very mild weather) and the heat dramatically more even.

Just sayin.

ethicalpaul

It definitely uses less fuel, but you won't be able to retire on the savings. The other factors that Jamie and PMJ mentioned are much more important IMO

dabrakeman

The average savings per month averaged over the heating season based upon the usage profiles in the plot and ~$8/McF total gas cost annual savings were ~ $187. If you don't have a way to control your recoveries to not build pressure with your oversized boiler then you probably will not see as much savings. There are other discussions already on that with suggestions from myself, PMJ and others.

Don_175

dabrakeman said:

The average savings per month averaged over the heating season based upon the usage profiles in the plot and ~$8/McF total gas cost annual savings were ~ $187. If you don't have a way to control your recoveries to not build pressure with your oversized boiler then you probably will not see as much savings. There are other discussions already on that with suggestions from myself, PMJ and others.

I'm confused. In the graph it says 7 degree nightly setback and 5 degree recovery. That would mean to me 58 at night and then 63 in the AM?

dabrakeman

Yes, In the evening I am at 66, have setback to 59 at night and then do a staged recovery to 64 which completes about breakfast time. The daytime stabilizes at 65 and then for the evening hours it steps up to 66. There are actually 14 steps to the schedule control overall per day (my Ecobee allows this control). Most of this is because of how I force the boiler off before starting a recovery, control the burn lengths during the recovery and force time between the recovery burn cycles. This all to prevent building pressure during the recoveries with my 40% oversized boiler.

PMJ

@dabrakeman , approx how many burns per hour during recovery?

ChrisJ

With how I have everything setup I can do a 10 degree recovery and likely not cycle on pressure.
That being said, I do not do a setback.

The reason is, people are always and home often some are awake at night at different hours.
To address temperatures I have TRVs on 5 out of 10 radiators. The bedrooms are kept much cooler. The bathrooms are kept on the warm side (I don't like a cold toilet). Cold bathrooms was my #1 dislike about a setback.

This keeps most of the house at 72 and the bedrooms around 67-68. The bathrooms may run a little higher on very cold nights.

SteamingatMohawk

Assuming I am reading the chart correctly, the red and green plots differ by two factors (as stated in the legend): location of main vents at the boiler versus at the end of the main, before it returns and "Ecobee". The text does not mention the Ecobee, so I can't see main vent location as the only difference. Am I missing something?

@AdmiralYoda You say, "My boiler is oversized and will short cycle on pressure. So once a minute it would cut out and cut back in once the radiators were fully hot." Once a minute seems too often, 60 times an hour?

PMJ

ChrisJ said:

With how I have everything setup I can do a 10 degree recovery and likely not cycle on pressure.
That being said, I do not do a setback.

The reason is, people are always and home often some are awake at night at different hours.
To address temperatures I have TRVs on 5 out of 10 radiators. The bedrooms are kept much cooler. The bathrooms are kept on the warm side (I don't like a cold toilet). Cold bathrooms was my #1 dislike about a setback.

This keeps most of the house at 72 and the bedrooms around 67-68. The bathrooms may run a little higher on very cold nights.

You also have a very advanced control which limits your boiler run time and matches it to the demand based on a number of factors about your structure and system you enter into it right? Then based on current outdoor temp it calculates in real time how long to burn. I see it even has a "recovery boost" setting you can use to limit what % over steady state demand operation you will allow it to do. There is just plain a lot of control available there that very few people have to fine tune things to prevent pressure from ever occurring. Really great stuff.

ChrisJ

PMJ said:

ChrisJ said:

With how I have everything setup I can do a 10 degree recovery and likely not cycle on pressure.
That being said, I do not do a setback.

The reason is, people are always and home often some are awake at night at different hours.
To address temperatures I have TRVs on 5 out of 10 radiators. The bedrooms are kept much cooler. The bathrooms are kept on the warm side (I don't like a cold toilet). Cold bathrooms was my #1 dislike about a setback.

This keeps most of the house at 72 and the bedrooms around 67-68. The bathrooms may run a little higher on very cold nights.

You also have a very advanced control which limits your boiler run time and matches it to the demand based on a number of factors about your structure and system you enter into it right? Then based on current outdoor temp it calculates in real time how long to burn. I see it even has a "recovery boost" setting you can use to limit what % over steady state demand operation you will allow it to do. There is just plain a lot of control available there that very few people have to fine tune things to prevent pressure from ever occurring. Really great stuff.

Yes to all.
I have recovery boost disabled though, and my thermostat handles that. The reason was I just had too many issues trying to get the indoor sensor to behave so I got rid of it, It was laziness on my part I think. Instead, the thermostat goes into 2nd stage if it's more than 1 degree away from set point which bypasses the Ecosteam. I have no doubt if it does a 10 degree recovery it's going to overshoot quite a bit. But a small normal recovery wouldn't, at least not much.

On days where I decide to raise the set temp a degree it takes a long time to do it, so no one notices but it slowly creeps up throughout the day.


I don't think most realize the difference it makes.

It truly makes a steam heating system invisible.........You don't even know it's there, you don't even know it's cold out side, the house just stays one steady temperature and nothing makes a sound.

Oh....and it never needs to be touched, reset, anything. It just works every day, day after day. What else would anyone expect from an expert in industrial process controls?

@KC_Jones Can comment on his experiences too.

I wish everyone with a steam heat system could have an Ecosteam. I really do..... One of the best things I've used from one of the best people I've ever known.

AdmiralYoda

So I'll give a little follow up to my own question. Since my boiler is something like 45% oversized I cycle on pressure with just about any setback, even just maintaining a set temperature when it is in the teens.

At something like 8oz of pressure my radiators are full and the pressure just keeps increasing until the Vaporstat kicks in. I installed an adjustable Dwyer pressure switch and a timer to help let the system dwell when it got to a certain pressure, say 10oz. This gave the system time to radiate some heat and try and satisfy the thermostat before kicking back on. If the thermostat wasn't satisfied after a certain time period the boiler would kick back on and the cycle would repeat.

The problem is that when the boiler first reached 10oz....the radiators were pretty warm but not really hot. My system just makes steam way faster than the radiators can condense it.

On a very cold day the thermostat would basically be calling for heat 100% of the time and the timer would keep the radiators warm enough to maintain temp, but not hot enough to satisfy the thermostat and take a break.

To make it work correctly I'd have to let the boiler cycle on pressure 2 or 3 times to really heat up the radiators and then have the boiler take a pause to let the radiators do their thing. I don't have the desire to engineer that complexity in. I've since removed the pressure switch and just "set it and forget it". It only cycles when it is in the 20's or colder.

I've always wondered if having a small setback would save fuel even though the boiler would be cycling on pressure for quite some time.

PMJ

@ChrisJ said:

"It truly makes a steam heating system invisible.........You don't even know it's there, you don't even know it's cold out side, the house just stays one steady temperature and nothing makes a sound."

"I wish everyone with a steam heat system could have an Ecosteam. I really do..... One of the best things I've used from one of the best people I've ever known."

Truth be told I'd have one if I hadn't been too late. I still can't believe this market rejected this solution.

I do use the same PLC that is in it and used some of the ideas. Mine is a lot simpler and I don't use outdoor temp or calculate anything. I wanted to stay with something that could be in a non-PLC form. But the fundamental I operate on is the same - the boiler burn time must be spaced out in more even pulses and limited somehow to more closely match the actual demand to eliminate pressure altogether and even out the heat. I also use a remote temp switch. It is the only sensor I use for actual control. It is used to determine the end of each burn and the beginning of the next. Anyone who thinks about this will realize that those times will be very much affected by how fast steam is condensing in the radiators which is an exact measure of the real time demand.

When you do these things the system becomes invisible and without sound. Even more so with natural vacuum with next to no air going in and out.

PMJ

I guess I use 2 sensors actually. A digital pressure switch opens the single solenoid vent to the atmosphere at the point in the burn when all the vacuum is gone. The amount of vacuum(it is generated a lot faster the colder it is) and when the solenoid opens also affects the burn length increasing the fill amount some in the cold. But it all changes automatically. I haven't changed any timer numbers in years.

Hipape

A home heating enthusiast here...evidently with too much time on my hands. I live is a 120 year old home in Wisconsin and had to replace my 30 year old steam boiler last year - New Yorker CGS50C. I measured the EDR of my radiators and came up with 263. The CSG50 is maybe too large - it's rated at 354. However, it's not quite as bad as the Weil-McClain EG-50A it replaced - 446sq.ft! Anyhow, last year I worked to insulate the mains and near boiler piping and instrument the boiler: measure near boiler temperatures and burn times. I also installed a 32" H2O pressure gage with a valve in front of it when not in use. By the time I was done, the cold weather was pretty much over. This year it's finally gotten into the 20s and 30s. I would like to thank you all for great suggestions and hints!!

I have a about a week's worth of data from mid 20s to mid 30s. The thermostat is set up for boiler, making at most two cycles per hour. Set to 68 during the data (7:45AM - 9:00PM) and then 60 degrees overnight. Below is an example of the burn cycles throughout the day - nothing between midnight and ~ 6:00AM, then a recovery, then steady state till ~ 8 or 9. Note: there are 2 ~ 20 minute burns separated by 90 seconds of cycle-guard, another 90 second of cycle guard, then a 17 minute burn. After that, there are 12 10-ish minute burns evenly spread over the next 12 hours or so.


Note: I can watch the pressure (if I remember to) - usually it gets to ~ 10" H2O or so (when the tstat sees 62 or 63 degrees. On a couple of days when the temp inside fell to 60 deg, the pressure gage did hit about 32" H2O before I shut the valve to protected it. The pressuretrol never kicked in. the following plot shows the 24 hour burn time in blue for the 7 days I looked at as well as the expected burn time in orange if no recovery was needed but had the same average 10-ish minute burns over the 24 hours. On the right-hand scale is the average temperature in grey. It would have been more satisfying to see an inverse relationship between temperature and burner times, but what can you do? Perhaps radiant heating of house on sunny days?


It is true that I will not be able to retire on the energy savings... but it's almost a 20% savings.... I understand that your mileage may vary - this is an isolated data point... I would be curious what the pros have to say - I'm open to suggestions...

On a somewhat related issue - I'd like to share the temperature profiles of the recovery this morning, probably the coldest day yet - outside temp at 6:00AM was 24F. The blue square wave line is the burner on/off

The ambient temperature is a sensor about 10' from boiler (all temp sensors are Dallas 18B20's read out with $20 NodeMCU wireless computer) The west and east returns are in the return lines just below the Barnes and Jones air vents and the skim port is just easy to get to. All sensors (except ambient) are more or less in contact with black iron with foam insulation around it - lots of plastic shrink wrap and the Dallas packages are plastic - not the best thermal contact... So, you can see when the boiler is off for 10 hours, it takes ~ 7 minutes for skim port temp to rise and maybe 12 minutes for the returns to rise once the boiler fires. Note the "East return" has a bit of downward excursion after the first two cycle-guard events - I believe the east air-vent is defective - I can see (with a dangling fiber) that it starts sucking in air! The recovery takes about 57 minutes - the longest in past week. 23 minutes later is the first of the 10-ish minute burns (actually 11.8) Since the iron is still hot, the response this time (and throughout the day) are much faster - about 2 minutes from start of burn to rise in return temps.

I hope someone found this interesting. I just thought it would be nice to share - and what a great forum!!

dabrakeman

PMJ said:

@dabrakeman , approx how many burns per hour during recovery?

1 burn per hour. Half hour (max) on and half hour (min) off. Picture probably depicts a full days control better:

SteamingatMohawk said:

Assuming I am reading the chart correctly, the red and green plots differ by two factors (as stated in the legend): location of main vents at the boiler versus at the end of the main, before it returns and "Ecobee". The text does not mention the Ecobee, so I can't see main vent location as the only difference. Am I missing something?



The red is year '18/'19 constant hold temp and main vents at end of main extensions. Green is '19/'20 constant hold temp and main vent location changed to end of mains. Yes, an Ecobee thermostat was installed mid season but it was left on hold temp. The next season ('20/'21) purple is same as green except now doing the setbacks and recoveries.

KC_Jones

I agree with @ChrisJ about how good the eco steam is, but I also have a fairly dramatic difference from a lot of steam systems we see and hear about.

My radiation is actually fairly close to my heat loss.  I have a 1500 sq ft 2 story house with 265 EDR.  Why is this important to the discussion?  Well when it’s really cold out, I have to suspend my 2 degree setback, I just don’t have the excess radiation to do a setback when I’m at or slightly below design.

This also means when I am at or below design my radiators get completely filled, on a few occasions, for days on end.  What I found interesting about this is that I thought I had the eco steam tuned in perfectly, and then we got a cold snap, and I was actually losing temperature.  Rads weren’t quite 100% full, so I had to tweak it again to make sure I was filling them completely.

When I do a setback, even with the eco steam running things, I can fill the radiators all the way.

All that said, I have zero issues with full radiators.  No noise, no discomfort, no drastic fluctuation.  This is partially because of the eco steam, but also because of a properly sized boiler, and appropriate radiation.  I agree with @PMJ on keeping the radiators hot longer is much more comfortable.

PMJ

@KC_Jones,

You do have a very different system than most of us who have lots of extra radiation. Filled radiators that need to be filled to match demand won't cause any issues. It's when radiators get filled to levels way above the actual demand that you get the rollercoaster. Your Ecosteam will be very good at preventing that.

Ducryder

What is an ecosteam and where do you buy one?

KC_Jones

Ducryder said:

What is an ecosteam and where do you buy one?

It was a system developed several years ago by an industrial controls guy who participated on this forum. He liked to tinker with his system a lot and developed a steam outdoor reset control system. When it came to market the interest died and he ended up stopping the business after that. Only a few of us have it.

It really is quite a nice set up, wish it would have caught on.