Anti-short cycle timer

acwagner

My timer only comes into play when recovering from large setbacks due to extended absence for travel.

I set it up in a very similar method to how @PMJ just described. Basically the timer "on" interval is long enough to satisfy a typical regular call for heat. The modulation only comes into play beyond that.

We don't travel as much now, so I just see it as another safety for my boiler. I agree it's a simple way to tame an oversized boiler. It worked for my application.

PMJ

> @Jamie Hall said:
> I'm right with you, @PMJ , on a seriously oversized boiler. It's a perfectly valid and simple approach. And I'm not deaf. Where I have trouble understanding the concept is its application to a system with a correctly sized boiler.

I think a boiler maxed out on design day will hit a pressure stop on a really mild day with 1/4 the load or less. I've never understood what correctly sized meant anyway as the load varies by multiples. With the timed approach plus a preheat sensor for cold starts boiler size literally makes no difference. And as I have stated many times lots of extra is required to take full advantage of natural vacuum ..... which is also of little interest here.

Jamie Hall

Ah. I think I see.

No, a boiler which is sized exactly will not max out on pressure -- ever. While it is true that the structure load varies over a huge range with the weather, this can and should be taken care of by thermostats or some other space comfort sensing system, the load the boiler sees in a steam system varies over a much smaller range (not quite zero, as the space temperature does affect the heat transfer rate from the radiation). Thus it is possible -- and should be but almost never is done -- to dial the boiler in to within 5% or better of the actual load -- particularly if some care is taken to account for minor losses, such a stretches of uninsulated pipe.

Perhaps the confusion arises from sloppy use of the term "correctly sized", of which we are all guilty to a greater or lessor extent. We use it -- loosely -- in two different and conflicting ways. One, we refer to a system being correctly sized when it can meet, operating at full capacity, the space comfort demand on a design day. This concept is used all the time in hot water heat, but there is no reason to not think of it for steam systems -- and by that usage, virtually all installed steam systems are significantly oversized (not all: there is, in fact, a whole class of residences and structures which are not: those originally built as three season vacation "cottages", where the steam system may be only just barely big enough for four season use. Cedric's home is one such). However, there is another sense in which the term is used: "correctly sized" within the system. There are lots of places where this comes up, but in steam it is mostly used to refer to the match between the installed radiation and the installed boiler capacity, both of which are fixed at the time of installation.

PMJ

> @Jamie Hall said:
> Ah. I think I see.
>
> No, a boiler which is sized exactly will not max out on pressure -- ever. While it is true that the structure load varies over a huge range with the weather, this can and should be taken care of by thermostats or some other space comfort sensing system, the load the boiler sees in a steam system varies over a much smaller range (not quite zero, as the space temperature does affect the heat transfer rate from the radiation). Thus it is possible -- and should be but almost never is done -- to dial the boiler in to within 5% or better of the actual load -- particularly if some care is taken to account for minor losses, such a stretches of uninsulated pipe.
>
> Perhaps the confusion arises from sloppy use of the term "correctly sized", of which we are all guilty to a greater or lessor extent. We use it -- loosely -- in two different and conflicting ways. One, we refer to a system being correctly sized when it can meet, operating at full capacity, the space comfort demand on a design day. This concept is used all the time in hot water heat, but there is no reason to not think of it for steam systems -- and by that usage, virtually all installed steam systems are significantly oversized (not all: there is, in fact, a whole class of residences and structures which are not: those originally built as three season vacation "cottages", where the steam system may be only just barely big enough for four season use. Cedric's home is one such). However, there is another sense in which the term is used: "correctly sized" within the system. There are lots of places where this comes up, but in steam it is mostly used to refer to the match between the installed radiation and the installed boiler capacity, both of which are fixed at the time of installation.

I still say that a boiler making steam at a rate that will satisfy design day demand is a rate that is several times what is required on a mild day. Given the natural time lag of these systems that boiler will have already put much more steam into the system than is needed by the time the stat is satisified whether there is an actual pressure stop or not on mild days. The resulting swings are more than are necessary. This current thread was initiated by someone trying to do something about exactly this. Doing better absolutely requires a control with a time factor limit in some form. It is so simple, so inexpensive, and so effective. The resistance to it is astounding. Boiler replacements will be recommended here first.

ChrisJ

I suspect each persons idea of comfort is different.

There's a rumor going around that I'm picky. I disagree with this rumor.

That being said, I tried @PMJ 's method and didn't like it. Either my system disagreed with it, or I'm just too fussy. However, I suspect it's still better than just a thermostat.

As @PMJ said, there's a huge delay and it's actually the best thing about cast iron radiation. As I've said before, I feel radiators act as capacitors, smoothing out the bursts of heat. If controlled properly, they convert a boiler's on\off cycles into a smooth almost continuous output.

I've yet to find a thermostat that will do this properly. Even my Prestige set to 3 CPH on it's own wasn't close to what the Ecosteam does. The Ecosteam literally makes my system transparent. You cannot tell when the boiler is on or off. My temperature will often only swing a few tenths of a degree. For example, If I'm set to 71F I'll see 71.2 to 71.6. And this is using a real thermometer, not the thermostat that will lie to you and tell you the temperature isn't moving.

The Honeywell thermostats tend to over-compensate. They will short cycle and then run super long cycles to fix undershooting and then end up with short cycles because they overheated badly. Over and over. They seem to settle down after a while, but changing conditions outside etc throw them off constantly.

Some how, the Ecosteam working with it keeps it "in line" so to speak. I think it just keeps the thermostat maxed out to the longest cycles it can run at whatever CPH setting it's on, so it becomes predictable rather than varying all over. Then the Ecosteam controls the cycles vs outside temperature.,

I still agree with the OP wanting a simple delay if pressure gets too high. It allows the radiators to cool down, get rid of some of their heat and could even satisfy the thermostat while the boiler is off. This can actually result in making the thermostat tighten it's swing if its using CPH. Less overshoot each cycle.

I'm sorry but a simple thermostat and pressure control isn't "good enough" anymore. It's almost 2020 and other systems have come a long way. Look at HW with it's outdoor reset and even forced air setups changing temperature resulting in greater comfort and increased efficiency.

ethicalpaul

Additionally from what I’m reading, I think these types of controls would make an oversized boiler much more efficient (by not running and running during the time when the radiators could be “coasting down”)

Edit: I guess that’s the whole point of this thread, but you know when it takes your brain some time to really internalize an idea? That just happened 😅

Jamie Hall

Perhaps, if I may draw a line under all this, we can agree on a few points...

First, each situation is different.
Second, there are many different ways to design and control a system, each of which has advantages and disadvantages.
Third, it is the responsibility of the designer to evaluate, without bias, all the available control and design strategies of which he or she is aware, and chose the approach which will function best in a particular situation.

Meanwhile, Cedric, with a stone age thermostat (one mercury T87), vapourstat, and boiler matched to the radiation (no pressure cycling), and dealing with near design conditions (it's cold out there!) is holding the temperature of a 7,000 square foot building, three stories, 100 feet long with a terrific wind load, to plus or minus half a degree at the thermostat and less than 3 degrees difference in different spaces. Works for me.

PMJ

ChrisJ said:

I suspect each persons idea of comfort is different.

There's a rumor going around that I'm picky. I disagree with this rumor.

That being said, I tried @PMJ 's method and didn't like it. Either my system disagreed with it, or I'm just too fussy. However, I suspect it's still better than just a thermostat.

As @PMJ said, there's a huge delay and it's actually the best thing about cast iron radiation. As I've said before, I feel radiators act as capacitors, smoothing out the bursts of heat. If controlled properly, they convert a boiler's on\off cycles into a smooth almost continuous output.

I've yet to find a thermostat that will do this properly. Even my Prestige set to 3 CPH on it's own wasn't close to what the Ecosteam does. The Ecosteam literally makes my system transparent. You cannot tell when the boiler is on or off. My temperature will often only swing a few tenths of a degree. For example, If I'm set to 71F I'll see 71.2 to 71.6. And this is using a real thermometer, not the thermostat that will lie to you and tell you the temperature isn't moving.

The Honeywell thermostats tend to over-compensate. They will short cycle and then run super long cycles to fix undershooting and then end up with short cycles because they overheated badly. Over and over. They seem to settle down after a while, but changing conditions outside etc throw them off constantly.

Some how, the Ecosteam working with it keeps it "in line" so to speak. I think it just keeps the thermostat maxed out to the longest cycles it can run at whatever CPH setting it's on, so it becomes predictable rather than varying all over. Then the Ecosteam controls the cycles vs outside temperature.,

I still agree with the OP wanting a simple delay if pressure gets too high. It allows the radiators to cool down, get rid of some of their heat and could even satisfy the thermostat while the boiler is off. This can actually result in making the thermostat tighten it's swing if its using CPH. Less overshoot each cycle.

I'm sorry but a simple thermostat and pressure control isn't "good enough" anymore. It's almost 2020 and other systems have come a long way. Look at HW with it's outdoor reset and even forced air setups changing temperature resulting in greater comfort and increased efficiency.

I completely agree @ChrisJ .

What I proposed here is very basic and in no way could compete with Ecosteam. It is where I started over 20 years ago. I've progressed a long way from that now.

At one time I saw a really good writeup Mark S. did explaining all this and why he developed Ecosteam. I can't seem to find it. Do you have it? I think people should read it (again maybe?).

PMJ

@Jamie Hall ,

I do agree with you that a boiler that barely gets it done on design day running flat out likely won't stop on pressure at any time. But I recommend more boiler than that; in fact I do like one that is big enough to pressure out if just let run.

There are significant benefits to extra boiler contrary to popular opinion. Since I believe the supposed negatives so often associated with big boilers (namely pressure and short cycling) are so easily and inexpensively eliminated with a more sophisticated control, I choose to take advantage of the positives. I like not barely getting by in the unusual cold snap. I like being able to recover much more quickly from a power event. Vacuum operation and all of its benefits are diminished as the size of the boiler goes down and the percent on time required goes up.

It is also clear that given the amount of discussion on this site about where to set vaporstats and pressuretrols that bigger boilers are the more common condition. To me that just means there is a lot of opportunity for control improvement. I do find it concerning when homeowners are told there really is no solution to be had for pressure other than new(smaller) boilers or expensive burners.

Jamie Hall

A few other pithy engineering maxims...

If you are evaluating two different approaches to a problem, both of which will do the job, the simpler one is to be preferred. KISS.

Software can mask a multitude of engineering and construction errors. It can also kill you.

Software should never be used to compensate for fundamental engineering problems.

A system which relies completely on software for control of a potential life safety situation must be at least triply redundant (this is more from transportation work -- there have been way too many single point failures in software and sensors for comfort; granted, only about a half dozen of these have resulted in fatalities, but... that's too many).

If you are working with a combined mechanical and software system -- get the mechanical system right first. Then tweak.

PMJ

Jamie Hall said:

A few other pithy engineering maxims...

If you are evaluating two different approaches to a problem, both of which will do the job, the simpler one is to be preferred. KISS.

Software can mask a multitude of engineering and construction errors. It can also kill you.

Software should never be used to compensate for fundamental engineering problems.

A system which relies completely on software for control of a potential life safety situation must be at least triply redundant (this is more from transportation work -- there have been way too many single point failures in software and sensors for comfort; granted, only about a half dozen of these have resulted in fatalities, but... that's too many).

If you are working with a combined mechanical and software system -- get the mechanical system right first. Then tweak.

Here we must agree to disagree.

I have spent my career designing and running equipment on the factory floor totally integrated with mountains of software from the very beginning of the first commercial Texas Instruments PLC. I use software to compensate for shortcomings of both hardware and humans all the time. I now use robots which are clearly a marriage of hardware and software where either one is worthless without the other. I use software to build in safety on machines where none existed before.

So what you consider a mechanical failure of my steam system (oversized boiler) to be fixed first at great cost; I view as not only not a problem but using software actually an advantage with just a $100 control and obviously my know how. The control can be bypassed and go back to original in a minute. But forgoing all these new controls have to offer out of a concern for reliability and or safety is really not a reasonable position today. Residential steam heat has suffered greatly for it.

Jamie Hall

The brave new world. I still won't ride in, never mind drive, a Tesla...

I should add, in at least an attempt at fairness, however, that I have no problem with using software or other efforts to compensate for poor initial design or construction, when rework (such as putting in a right size boiler in this discussion) would be significantly more expensive. That's quite valid, and there have been many occasions on which I have recommended it. Nor do I have any problem with using software -- some of it very advanced -- to enhance the capabilities or efficiency of an otherwise sound design, provided there is a way to fail operational to the underlying sound design. (such as, in aerospace, turning off the magic when it goes squirrely. Boeing allows you to do that. Airbus does not). What I do object to is not doing the fundamentals to the highest and best standard possible, and then using software to cover -- but that is for initial work, not recovery later. Two very different things.

ethicalpaul

With a Tesla, the traditional safety firewall is the driver, who must remain attentive (if we're talking about self-driving). So a failure of the software has to be corrected by an attentive driver or disaster can occur.

With steam controls, it seems to me that if one puts in some additional software controls, they can't really cause an unsafe condition because the good ol' pressuretroll and LWCO are still there being vigilant watchdogs.

The software could cause a failure to heat which could definitely result in damage, but I don't see it causing for example an explosion or boiler dry fire.

ChrisJ

Jamie Hall said:

The brave new world. I still won't ride in, never mind drive, a Tesla...

No one's saying it so I'll just say it...........
Ok Boomer.

Jamie Hall

ChrisJ said:

Jamie Hall said:

The brave new world. I still won't ride in, never mind drive, a Tesla...

No one's saying it so I'll just say it...........
Ok Boomer.

Worse. I'm a prewar baby -- World War II, that is.

rlev11

I've been following this thread as I have a similar situation on my small steam boiler (sgo-3). Only when it gets really cold like in the 20's or teens and usually when I am recovering from my 2 degree setback in the morning by boiler will cycle once or twice on pressure now that I have a vaporstat set at 10oz cutoff before the thermostat is satisfied.

Before with my pressuretrol it NEVER cycled on pressure even with it set to the lowest setting. Boiler off time from the vaporstat is usually only 45 seconds to a minute until it kicks back on. Some sort of timer inline to cut the power on the return line voltage leg from the vaporstat back to the burner would be of benefit to me. Even set at 5 minutes, I doubt the boiler would ever fire back up as the rising temp in the house had time to satisfy the thermostat.

Not looking for some expensive or convoluted device, just something that sensed the dropout of the line voltage from the vaporstat, started a timer and opened the line, then closed the line back up after the timer is done.

PMJ

Jamie Hall said:

ChrisJ said:

Jamie Hall said:

The brave new world. I still won't ride in, never mind drive, a Tesla...

No one's saying it so I'll just say it...........
Ok Boomer.

Worse. I'm a prewar baby -- World War II, that is.

Never to old for PLC's @Jamie Hall . Downright fun they are with steam. I bet you'd be good at it.

Hap_Hazzard

Jamie Hall said:

Software can mask a multitude of engineering and construction errors. It can also kill you.

Software should never be used to compensate for fundamental engineering problems.

See Boeing 737 Max.

Jamie Hall

Hap_Hazzard said:

Jamie Hall said:

Software can mask a multitude of engineering and construction errors. It can also kill you.

Software should never be used to compensate for fundamental engineering problems.

See Boeing 737 Max.

Or any Airbus. Sully was d__n lucky to pull off the miracle in the Hudson, as the control computers kept trying to dive the 'plane -- and he couldn't shut them off to make a decent flare for the touchdown.

It's not just Boeing or Airbus (both have had fatal crashes from poorly thought out or mishandled software), though -- I could draw more or less horrifying examples from shipping, or the British Network Rail, or US rail (particularly rapid transit) or automotive applications where computers tried (and sometimes did) manage to crash the machine or kill people.

rorylane

As with many of these things, it comes down to personal choice. Even though modern cars get better mileage and have airbags, I choose to drive old ones because I understand how they work and can maintain myself. Self driving cars are an example of giving up one kind of control in favor of another. With distracted driving on the rise autonomous cars aim to fix that. I choose to drive machines which require your utmost attention just to drive straight down the road... In this case I may be more comfortable with the application of technology in boiler controls than I am in vehicles, but I do still love the beautiful simplicity in a two pipe gravity return steam system.

ChrisJ

Are you seriously comparing a Boeing or Airbus to a simple PLC controlling a steam system?

Come on guys.

Not to mention the thermostat and in my case, PLC, are wired in outside of the safety devices. The LWCO, Pressuretrol, Spill switch and rollout switch all have the final say.

Hap_Hazzard

Okay, kid.

ChrisJ

rorylane said:

As with many of these things, it comes down to personal choice. Even though modern cars get better mileage and have airbags, I choose to drive old ones because I understand how they work and can maintain myself. Self driving cars are an example of giving up one kind of control in favor of another. With distracted driving on the rise autonomous cars aim to fix that. I choose to drive machines which require your utmost attention just to drive straight down the road... In this case I may be more comfortable with the application of technology in boiler controls than I am in vehicles, but I do still love the beautiful simplicity in a two pipe gravity return steam system.

Ford model T or A?

Although with good king pins and alignment I'd expect even those to stay straight for the most part. But you do need to double clutch and manually control the ignition timing.

Jamie Hall

I learned to drive on our Model A pickup... if you fiddled the ignition timing right you could get a lovely backfire out of it to scare the girls... But the brakes did leave something to be desired.

Hap_Hazzard

I bet you used to take the girls to the submarine races in that thing, @Jamie Hall.

Jamie Hall

Snipe hunts...

rorylane

> @ChrisJ said:
> (Quote)
> Ford model T or A?
>
> Although with good king pins and alignment I'd expect even those to stay straight for the most part. But you do need to double clutch and manually control the ignition timing.

I may have exaggerated slightly. Most of the fleet is from the 60s and 70s, they have all the modern convenience I require.

BobC

Even a properly sized boiler is only really proper at design temperature so some systen has to be devised for it to work the other 99% of the time.

Using software for control makes sense be cause it's cheap and repeatable. I would not want to trust just software for safety without a mechanical fail safe to back it up.

I worked on the post offices robotic containment systems a decade ago and those had software safety controls. One day I was helping a coworker clear a jam, he was in the cage while I was outside at the control panel. We were doing well when the robotic arm took off on it's own with Jimmy in the cage. I hit the E-stop and it didn't work, I then knifed the power and it stopped immediately.

Anything can fail, best to have redundant safeties in place.

Wellness

@PMJ & @acwagner. You two guys are my heros. I know my boiler is not oversized but for months it has cycled way too frequently. I had always said I hated integrated boiler controls because they are not flexible enough to work with every situation. The maximum anti-cycling control on my boiler was 10 minutes. Got a Timing Relay and increased the delay to 20 minutes and my system is now running like a champ. During any 20 minute pause, my secondary zone circulator keeps pumping hot water from my buffer tank to satisfy any thermostat call for heat, if necessary. And now with my boiler firing up to 50% less frequently, I expect my fuel bills to go way down. As @PMJ put it: "It is so simple, so inexpensive, and so effective. The resistance to it is astounding." Kudos, gentlemen.

PMJ

Wellness said:

@PMJ & @acwagner. You two guys are my heros. I know my boiler is not oversized but for months it has cycled way too frequently. I had always said I hated integrated boiler controls because they are not flexible enough to work with every situtation. The maximum anti-cycling control on my boiler was 10 minutes. Got a Timing Relay and increased the delay to 20 minutes and my system is now running like a champ. During any 20 pause, my secondary zone circulator keeps pumping hot water from my buffer tank to satisfy any thermostat call for heat, if necessary. And now with my boiler firing up to 50% less frequently, I expect my fuel bills to go way down. As @PMJ put it: "It is so simple, so inexpensive, and so effective. The resistance to it is astounding." Kudos, gentlemen.

@Wellness , Thank you for this. Your support is much appreciated.

PMJ

BobC said:

Even a properly sized boiler is only really proper at design temperature so some systen has to be devised for it to work the other 99% of the time.

Using software for control makes sense be cause it's cheap and repeatable. I would not want to trust just software for safety without a mechanical fail safe to back it up.

I worked on the post offices robotic containment systems a decade ago and those had software safety controls. One day I was helping a coworker clear a jam, he was in the cage while I was outside at the control panel. We were doing well when the robotic arm took off on it's own with Jimmy in the cage. I hit the E-stop and it didn't work, I then knifed the power and it stopped immediately.

Anything can fail, best to have redundant safeties in place.

All of these controls, timer or PLC based, just go in series with the output of the tstat. All the standard safety devices remain as before. These controls simply limit maximum straight burn times and establish minimum wait times in between burns. They just spread out the burn time which reduces maximum system pressure peaks which evens out the result. The simple timer allows just one setting for all conditions. The PLC platform opens up limitless possibilities for additional sensor inputs and individual control development.

Properly done they won't and can't cause the boiler to run any time the standard control wouldn't run it. They do, however, keep the boiler off at times the standard control would have it on.

ethicalpaul

It keeps being said 😅

Kjmass1

@PMJ Helped me install the on/off delay timer and it is a thing of beauty. At outdoor temps above 10F or so, my ecobee can handle all the call times while shutting off and not overshooting the set point no problem. No pressure is built up with cycles around 15-20 minutes. I keep a tight deadband of .5-1F which is averaged across 4 sensors in the house.

At temps below 10F, my 200K/153K boiler would start to build pressure and vents would be hissing like crazy. Boiler is 3x-4x oversized for my heatloss of 45K or so at 9F. Below 0F my boiler would be running 30minute on/30minute off. Radiators would still be hot by the time the next cycle came on so pressure would build way too fast and I'd be turning off the stat in the middle of the night to quiet it down, no sleep!

So now I have the timer hooked up and when I know temps will be artic, I'll set it to 15 on/15 off. My house still gets 30 minute runtimes per hour, but is allowed time to rest to prevent short cycling and pressure. It also works great if you are gone for a week and are coming out of a 10 degree setback. It'll just call for heat for a couple hours and slowly work it's way back without building any pressure. Best thing is it's a piece of cake to adjust. With ecobee runtime data you know exactly how long your boiler cycles per hour.

More cycles keeps the pipes warm in the basement, delivering steam faster to the rads, which means better efficiency reducing standby losses. Also more even heat.

ChrisJ

Kjmass1 said:

@PMJ Helped me install the on/off delay timer and it is a thing of beauty. At outdoor temps above 10F or so, my ecobee can handle all the call times while shutting off and not overshooting the set point no problem. No pressure is built up with cycles around 15-20 minutes. I keep a tight deadband of .5-1F which is averaged across 4 sensors in the house.

At temps below 10F, my 200K/153K boiler would start to build pressure and vents would be hissing like crazy. Boiler is 3x-4x oversized for my heatloss of 45K or so at 9F. Below 0F my boiler would be running 30minute on/30minute off. Radiators would still be hot by the time the next cycle came on so pressure would build way too fast and I'd be turning off the stat in the middle of the night to quiet it down, no sleep!

So now I have the timer hooked up and when I know temps will be artic, I'll set it to 15 on/15 off. My house still gets 30 minute runtimes per hour, but is allowed time to rest to prevent short cycling and pressure. It also works great if you are gone for a week and are coming out of a 10 degree setback. It'll just call for heat for a couple hours and slowly work it's way back without building any pressure. Best thing is it's a piece of cake to adjust. With ecobee runtime data you know exactly how long your boiler cycles per hour.

More cycles keeps the pipes warm in the basement, delivering steam faster to the rads, which means better efficiency reducing standby losses. Also more even heat.

I have to disagree with the efficiency comment.

The longer the pipes are at full temperature, the greater the standby losses. Just because steam gets to radiators faster doesn't mean overall efficiency is higher.

The bigger the temperature difference between piping and surrounding air, the bigger the losses are. Period. Their losses are peaked while steaming and zero when at the same temperature as the surrounding air.

This also includes those who feel keeping piping hot for no reason is beneficial. Beneficial to comfort maybe, but not to efficiency.

In your case it sounds like you're using those piping losses to heat the basement. If that's the case, that's not lost at all IMO.

PMJ

ChrisJ said:

Kjmass1 said:

@PMJ Helped me install the on/off delay timer and it is a thing of beauty. At outdoor temps above 10F or so, my ecobee can handle all the call times while shutting off and not overshooting the set point no problem. No pressure is built up with cycles around 15-20 minutes. I keep a tight deadband of .5-1F which is averaged across 4 sensors in the house.

At temps below 10F, my 200K/153K boiler would start to build pressure and vents would be hissing like crazy. Boiler is 3x-4x oversized for my heatloss of 45K or so at 9F. Below 0F my boiler would be running 30minute on/30minute off. Radiators would still be hot by the time the next cycle came on so pressure would build way too fast and I'd be turning off the stat in the middle of the night to quiet it down, no sleep!

So now I have the timer hooked up and when I know temps will be artic, I'll set it to 15 on/15 off. My house still gets 30 minute runtimes per hour, but is allowed time to rest to prevent short cycling and pressure. It also works great if you are gone for a week and are coming out of a 10 degree setback. It'll just call for heat for a couple hours and slowly work it's way back without building any pressure. Best thing is it's a piece of cake to adjust. With ecobee runtime data you know exactly how long your boiler cycles per hour.

More cycles keeps the pipes warm in the basement, delivering steam faster to the rads, which means better efficiency reducing standby losses. Also more even heat.

I have to disagree with the efficiency comment.

The longer the pipes are at full temperature, the greater the standby losses. Just because steam gets to radiators faster doesn't mean overall efficiency is higher.

The bigger the temperature difference between piping and surrounding air, the bigger the losses are. Period. Their losses are peaked while steaming and zero when at the same temperature as the surrounding air.

This also includes those who feel keeping piping hot for no reason is beneficial. Beneficial to comfort maybe, but not to efficiency.

In your case it sounds like you're using those piping losses to heat the basement. If that's the case, that's not lost at all IMO.

I agree with @Kjmass1 on efficiency. The warm basement pipes radiate heat into the house primarily so it isn't a dead loss at anyway.

But more importantly my experience is that efficiency is directly related to the percentage of the time the boiler is firing that there is actual positive steam delivery to the rads. The most wasteful time is all the minutes the boiler is firing that no steam delivery is happening at the radiators. I have found without question that warmer piping between cycles raises this delivery percentage. Time to steam off 30 minutes is more than double off 15 minutes. So total time to steam is less with two 15/15 cycles per hour than 1 30/30 cycle.

Vacuum operation significantly increases this percentage with the positive flow of steam to the rads after fire. This keeps the piping significantly warmer than it would be open vented for the same off time which further reduces time to steam at rads on the next firing. Vacuum steam total delivery percentage is significantly higher than open vented and the average supply piping temperature is significantly higher. It is quite clear to me that warmer piping overall is more efficient not less. It is a win-win comfort and efficiency.

Thanks for your comment @Kjmass1 . I see that you like having the option to easily dial in any on/off /CPH scheme you want to for your maybe $100. investment. That big boiler is now only as big as you want it. Now you have a whole range of options and aren't just stuck with one size. Good show.

ChrisJ

@PMJ you're going to argue basic thermodynamics?

I'll pass my friend.

Jamie Hall

At various times there have been a whole rang e of comments on various control strategies for oversize steam boilers (and not oversized ones) and cycle time variations and warmer starts and cooler starts and so on... and on... and on... and several of us have fondly held opinions on the subject.

What we don't have is hard data, and I'm not at all sure that anyone (certainly not me!) has the money to set up a test rig to actually get the data. I'd love to see it happen! What we need is a slightly oversize boiler -- say with the EDR equal to the radiation (and the radiation actually known accurately -- another can of worms) which should give a steady state situation of the boiler producing that magic 33% more output than the radiation can absorb. The boiler must be piped to give high quality dry saturated steam Then we need to have the boiler clean and properly adjusted, and the combustion efficiency -- again at steady state -- measured. All of this feeding into a controlled space where the heat loss from the space can be actually measured (space outside the test space separately controlled) . We also need an accurate fuel flow meter and (much harder!) an accurate steam flow measuring system.

Now we can set about running the boiler. We can measure the actual BTUh input to the boiler's burner. We can measure the actual heat output of the boiler (steam temperature and mass flow rate). We can measure the heat delivered to the space. And from that we can determine the actual real life efficiency.

Then we can play with various control strategies for our boiler and see how -- or if! -- the affect the efficiency. Should do this for both gas and oil burners, too.

Could also throw in, since everything is controlled or measurable, the effect of setbacks...

Anyone want to play? The whole setup shouldn't be much more than high 6 to low 7 figures... take a few months to run and analyse…

But friends, until we get that it seems to me that we all -- certainly myself -- are running as much on impressions, gut feelings, and theorizing as on anything else, and we should be rather cautious about firm statements...

Or, as they say in the auto industry, your mileage may vary...

PMJ

> @ChrisJ said:
> @PMJ you're going to argue basic thermodynamics?
>
> I'll pass my friend.

Happy to discuss the technical specifics anytime.

I'll say it again. The higher the percent of the time the boiler is actually running that steam is actually being delivered to the rads the more efficient it is. The higher the percent of dead "non -delivery" time, the lower the efficiency.

If warmer piping is not better than colder must be no?

PMJ

> @Jamie Hall said:
> At various times there have been a whole rang e of comments on various control strategies for oversize steam boilers (and not oversized ones) and cycle time variations and warmer starts and cooler starts and so on... and on... and on... and several of us have fondly held opinions on the subject.
>
> What we don't have is hard data, and I'm not at all sure that anyone (certainly not me!) has the money to set up a test rig to actually get the data. I'd love to see it happen! What we need is a slightly oversize boiler -- say with the EDR equal to the radiation (and the radiation actually known accurately -- another can of worms) which should give a steady state situation of the boiler producing that magic 33% more output than the radiation can absorb. The boiler must be piped to give high quality dry saturated steam Then we need to have the boiler clean and properly adjusted, and the combustion efficiency -- again at steady state -- measured. All of this feeding into a controlled space where the heat loss from the space can be actually measured (space outside the test space separately controlled) . We also need an accurate fuel flow meter and (much harder!) an accurate steam flow measuring system.
>
> Now we can set about running the boiler. We can measure the actual BTUh input to the boiler's burner. We can measure the actual heat output of the boiler (steam temperature and mass flow rate). We can measure the heat delivered to the space. And from that we can determine the actual real life efficiency.
>
> Then we can play with various control strategies for our boiler and see how -- or if! -- the affect the efficiency. Should do this for both gas and oil burners, too.
>
> Could also throw in, since everything is controlled or measurable, the effect of setbacks...
>
> Anyone want to play? The whole setup shouldn't be much more than high 6 to low 7 figures... take a few months to run and analyse…
>
> But friends, until we get that it seems to me that we all -- certainly myself -- are running as much on impressions, gut feelings, and theorizing as on anything else, and we should be rather cautious about firm statements...
>
> Or, as they say in the auto industry, your mileage may vary...

Correct me if I'm wrong but what I read here is that this is all too complicated with too many variables to test for and control to satisfy everyone so the exercise is pointless so let's just stop.

Well I don't think some of the basics are that complicated. Warmer delivery piping is either a positive or a negative for efficiency. If one argues that warmer is less efficient then colder must be more efficient. How much colder then? Really? Should we cool it down on purpose between cycles? Nuts.

Having to push air out of the system every cycle is not a plus or more efficient than not doing it. It doesn't help. Surely we can agree on that. Otherwise we should have an air pump instead of a vacuum pump and pressurize on the off cycle to have more to push out each cycle. Again nuts.

No @Jamie Hall , all of this isn't so complicated that we need to just throw up our hands.

Jamie Hall

No, generally I agree with you, you know. Keeping the system warm -- preferably very warm! -- while cycling, if cycling is necessary (which it often is) -- and steam filled is definitely going to be better than allowing it to cool down and fill again with air -- or even just cool down. As a case in point, Cedric -- when he does cycle (such as a very long run out of setback) -- never drops below 1 ounce gauge (he wouldn't drop that far, but the burner post purge/pre purge timing introduces a fixed delay), so no air to push out, and never really quite goes off the boil (there's enough stored heat in the boiler metal). Seems to work well... for that setup.

But I don't have hard numbers. Would a lower frequency pulse modulation, with a longer off band, work better? I honestly don't know. I wouldn't think it would -- on theoretical grounds -- but... Would it work more efficiently with a lower frequency and vacuum vents? Don't know that, either, though honestly in my opinion I doubt it -- but again, no hard numbers, so it's just my gut feeling and my interpretation of theory.