Cycles Per Hour Problem.

AdmiralYoda

I just installed a new digital Honeywell T87 thermostat.  Set the DIP switches to 1 cycle per hour and set the temp.  It came on when it was supposed to....but then turned on again shortly after.

Maybe I'm not understanding cycles per hour correctly.  If the thermostat calls for heat and is satisfied...does it wait for one hour before it will call for heat again?

Just now the T87 thermostat called for heat and was satisfied.  The boiler did not cycle on pressure, then 15 minutes later I heard the boiler kick back on for a couple of minutes.

Sound normal or am I missunderstanding this?  Thanks!

ChrisJ

If that is like the more expensive Honeywell thermostats it may need to learn how the system behaves and settle in.

Its not literally 1 cph.  That's just what it uses to plan how it's going to behave.   2 cph would be shorter cycles etc.

Let it run for a day and see what happens

AdmiralYoda

Thanks @ChrisJ.  I don't think it has much for smarts inside, it's basically the digital version of the mechanical T87.

It overshot by one degree.  I'll keep an eye on it and see what it does.

ChrisJ

AdmiralYoda said:

Thanks @ChrisJ.  I don't think it has much for smarts inside, it's basically the digital version of the mechanical T87.

It overshot by one degree.  I'll keep an eye on it and see what it does.

Consider what is inside of a modern smart phone and what it's capable of.

acwagner

The CPH logic for thermostats is kind of a black box. My own experience with "dumb" thermostats is the CPH setting really just adjusts the temperature band at which the thermostat calls for heat and is satisfied. The lower the CPH setting the bigger the range, the higher the CPH setting the narrower the range.

PMJ

Consider also that as these devices become capable of more and more we seem to be supplied less and less information about what they are doing. Let's just say you can't be accused of failing performance promises when you don't make any. I'm quite sure Honeywell has thought of that.

ChrisJ

PMJ said:

Consider also that as these devices become capable of more and more we seem to be supplied less and less information about what they are doing. Let's just say you can't be accused of failing performance promises when you don't make any. I'm quite sure Honeywell has thought of that.

How's your Nest treating you these days?
Still trouble free?

PMJ

What Nest is that?

AdmiralYoda

So for the past 24 hours it has been typical winter temps.  The T87 is consistently overshooting by 2 degrees although the other rooms are comfortable.

I'm pretty sure it's the nature of the beast with a big heat mass that continues to heat after the thermostat is satisfied.

The real answer is one of those time delay timers to slow things down a bit.

For the fun of it today I'm going to change it to 3 cycles per hour to see how it handles being in a tighter range.

ChrisJ

AdmiralYoda said:

So for the past 24 hours it has been typical winter temps.  The T87 is consistently overshooting by 2 degrees although the other rooms are comfortable.

I'm pretty sure it's the nature of the beast with a big heat mass that continues to heat after the thermostat is satisfied.

The real answer is one of those time delay timers to slow things down a bit.

For the fun of it today I'm going to change it to 3 cycles per hour to see how it handles being in a tighter range.

Change it to 2 CPH if possible, if not, try 3 and let it settle in for another day.

AdmiralYoda

@ChrisJ that's the plan. It only has 1, 3, 6 or 9 cycles per hour so I'll try 3.

Looking into it a bit more, the T87 doesn't have any smart learning features to anticipate the heat.

I may eventually move on to a more advanced model just for learning features and more cycle per hour options.

acwagner

Being well main vented (and balanced) becomes critical at the higher CPH settings on a one pipe system. The boiler runs more frequently, so the piping stays warmer between cycles, and the vent capacity becomes the limiting factor for the time it takes for the steam to reach the radiators.

I bet you'll find the 3 CPH a good balance, since it sounds like the system is responding quickly.

You could also find a thermostat that lets you directly adjust the temperature sensing range and forget about the CPH setting black box logic. I have an older White-Rodgers thermostat that allows that. I like it because it has much finer settings and I know what I'm getting by changing them.

Precaud

Maybe just a litle off-topic, but here's the question: How do you implement an "anticipator" digitally?

SImple. A short time after a call for heat, you just add some fractional degrees to the measured temp before comparing it to the set temp.

I have seen both of the Honeywell tstats I have owned do exactly this. Including this morning. I'll explain.

This year I am using CPH of 2 and a setback to 68º overnight. When I awoke, the room temp showed 68 but hadn't called for heat yet. So I increased the set temp to 69, resulting in an immediate call for heat. Five minutes later I walked by the tstat and saw that the room temp display was at 69. But no heat had been generated yet! About five minutes later heat started to arrive at the radiator valves. Shortly thereafter the tstat acts as if the set temp had been satisfied and switches off the call for heat. Again, no actual heat had been introduced into the rooms by the rads yet.

The tstat sits like this for maybe 10 minutes and then starts up again. This time actual heat is produced, because the system has warmed up. From there it operates normally.

Jamie Hall

The older mercury T87 used a true anticipator. It was a fiddly beast to get set right -- but when it was, it responded well to varying environmental conditions around it (such as a cold room recovering from a setback vs. maintaining a warm room -- or a warm room without draughts vs. a warm room with, and so on).

The concept is fundamentally very simple -- it was a small heater in the thermostat, the output of which could be adjusted to match the characteristics of the room. Not prefect, but astonishingly close.

To do this digitally, however, is not simple, and actually requires a fair amount of computing power. You need to have fixed inputs for the maximum heating power of the radiation, of course. You also need to have input the variation of the power of the radiation with time (after the thermostat asks for heat, how long does it take for the radiation to start heating? How fast does it ramp up to full power?) Then you need to measure the rate of change of the space temperature, and compare that to the target and the known amount of energy stored in the radiators; the rate of rise compared to heat output will give you the current heat demand of the space.

And so on.

Needless to say, this is not implemented in most thermostats. The ones which claim to learn do try to incorporate some of this, in a "black box" model, but they cannot learn to cope with environmental variations -- and don't.

I like my mercury T87s...

PMJ

I'm not much into someone else's "black box" either. I like the boxes that run code I wrote so I know what it is doing. I also like to be able to learn and change my mind. Most can't or don't wish to get that involved which is understandable. To them I say Honeywell surely appreciates your regular and ongoing support.

I agree nothing available is going to be more solid than the mercury T87 once adjusted - as astonishing as it is I can say that. Likewise nothing will outperform my 63 year old standing pilot bimetal strip safety on any basis - not annual cost obviously. Oh well, let's have a toast to all the technical progress.

All I want is an accurate on/off temperature switch with a tight dead band. I'll take it from there.

Jamie Hall

I have no real problem with all the up to date technology. Except two things: forced obsolescence, and the utter inability of people to cope with it when it goes toes up. Had a nice experience with that today -- quite irrelevant. The powers that be are phasing out 3G telephone service in my area, so I need to get a new 'phone, all singing and dancing and 5G. Marvelous. Went to get it. Got it. It didn't work. The dealer clown show spent two hours trying to get it to work. No joy. Then another hour to get my old 'phone working again. Then had the gall to charge me a restocking fee for the dead on arrival 'phone.

Say again?

The Western Electric dial 'phone on my daughter's desk still works as well as the day AT&T installed it in 1954. Some day I'm sure that they will drop support for it -- and probably land lines entirely.

Then I think I'll resort to smoke signals and carrier pigeons...

ChrisJ

@Jamie Hall I can't stand the sound quality of a carbon button.  I have several WE500s including a more modern plastic dial one.  I also had a wall hung.

Yes they work and yes they're bullet proof but most things need to be when rented to the public.   

PMJ

@betweentheframe , I don't recall arguing there are no possibilities. I'm using more of them than most. I just like to know more about the logic in the box than is provided.

Sounds like you say Nest has steam all figured out and then some. Feel free to sell it to the users here having trouble. Obviously they are ready for solutions. Step right up. I have no first hand experience with it. This is the first I am hearing Nest makes all the problems go away. But then I do miss stuff.

ChrisJ

I had a Nest connected to my steam system once...

Then it went back to the store.

PMJ

I won't knock the Nest - really just don't know anything about it.

I've heard it is pretty good at recording what actually happens and making that easily available.

ChrisJ

PMJ said:

I won't knock the Nest - really just don't know anything about it. I've heard it is pretty good at recording what actually happens and making that easily available.

After using one for a short time I have developed this opinion of it.

Dan_NJ

A T87 has never been bricked by a firmware update.

ChrisJ

Dan_NJ said:

A T87 has never been bricked by a firmware update.

Neither has a pocket calculator but you'll have difficulty trying to post on HH with it.

ChrisJ

betweentheframe said:

PMJ said:

@betweentheframe , I don't recall arguing there are no possibilities. I'm using more of them than most. I just like to know more about the logic in the box than is provided. Sounds like you say Nest has steam all figured out and then some. Feel free to sell it to the users here having trouble. Obviously they are ready for solutions. Step right up. I have no first hand experience with it. This is the first I am hearing Nest makes all the problems go away. But then I do miss stuff.

@ChrisJ - Its a piss poor carpenter that blames their tools. 

Most people have a lot of problems, the thermostat prob least of them. The nest uses anticipated heat loss based on weather and history of heating recovery and kicks on and kicks off before up to temp to avoid overshoot. I also used it in my place upstate with modcon and radiant/panels/etc. Never had problems

I install a nest temp sensor in all major rooms, have used their performance to set up venting and downfire my oversized radiator and am using about 28 percent less therms (based on run time, not cutting out on pressure). I can also use it to make sure I give priority to temp in my wife's office M-F during working hours, bedroom at night (kids room if I had kids) and living room in evening and morning. Not that it matters as much since I have balanced system(by balance I mean everything at 70 except wife's office super hot lol cause she demands it and has to wfh so what can I say)

That's funny.

I'm sorry but it sounded like you were suggesting my heating system has problems.

PMJ

@betweentheframe, it sounds like the Nest can zone and provide heat to rooms individually too. How does it do that? I admit, I have a lot of catching up to do.

ChrisJ

betweentheframe said:

@ChrisJ no, have no idea about your heating system. my tag to you was in response to your nest comments being what my old norwegian mentor called “typical carpenter blaming a tool... all tools are hammers except flathead screwdrivers, those are chisels”.

The rest was response to the steam and problems etc etc. This website is very web 1.0, and I did not use it’s reply function in a way that made my two diff responses clear. 

I tried a Nest.
Besides it seeming very gimmicky and locking up I had little interest in it.  I'm sorry but I have no use for a thermostat that locks up.

I currently run a Honeywell Prestige with an outdoor sensor and 3 indoor sensors as well as duct sensors for the be AC and an Internet gateway.   

Between that and the boiler is an actual outdoor reset for a steam boiler.

PMJ

betweentheframe said:

PMJ said:

@betweentheframe, it sounds like the Nest can zone and provide heat to rooms individually too. How does it do that? I admit, I have a lot of catching up to do.

@betweentheframe said"No, just can put sensors in other rooms and use those instead of tstat for the temp sensing. Much easier than running wires. Like lutron caseta picos-no more 3/4/5 way switch wiring nightmare!" 

So the Nest makes it easier to see on one screen that steam delivery has been uneven, but doing anything about that is done the old fashioned way right? I could use a different temp sensor or average of several with the Nest to turn the boiler on, but once steaming all places get steam just as before as determined by the existing hardware. The only thing I have come across that actually adjusts steam delivery to different places in real time according to changing conditions and evens things out through the same hardware is vacuum.

Looking quickly it seems that Nest doesn't say much or really anything about the logic they use in their unit. Only that it "learns" about you and does a really great job of that. I suppose they can't give away their secret sauce. Being connected to the internet all the time I assume they have the ability to change what they are doing without notifying you. I know, they promise not to do that. I assume you have an old style backup unit you can throw on just in case they make a mistake with an "update" and accidentally shut you down altogether. I would have one ready and practice the switch back at least once.

Don't get me wrong, I am really not against this approach at all. It is all the vast majority of people have to throw at this. I am always studying cause and effect in my system and have to know exactly what is doing what. Obviously that would not be possible with a Nest which they say is constantly changing what it does.

BobC

Ten thousand Swedes ran through the weeds looking for one Norwegian, ten thousand more were held at the door by one . . .

My grandfather and uncle (mothers brother0 used to recite different versions of this while bottling beer in the cellar.

Before anyone gets upset I am half and half on my mothers side, Irish on my dads side. My doctor once said this mix makes the hardest cement - after patching up my skull again.

Bob

AdmiralYoda

After a few days with the digital T87 I'm not so impressed.  Here are some very short term observations:

One cycle per hour:
The outdoor temp was consistently around 20 at night and 30-35 during the day.  The thermostat would call for heat and it would take a while for the boiler heat up the cool radiators.  The thermostat would be satisfied but there would still be plenty of heat in the now HOT radiators and the house would overshoot by 2 degrees. 

Then as the house slowly cooled, by the time the thermostat called for heat the radiators and boilers would be stone cold and it would take a significant time just to start to warm things up.  Meanwhile the thermostat now indicates the room temp is now 2 degrees below the set temp, and the whole cycle repeats itself.  

So overall there is a 4 degree temp swing in which we feel too warm and then too chilly.

3 cycles per hour:
Outdoor temps were 20-low 30's at night and 30-40 during the day.  The indoor temp seems to be more stable but the mild conditions may be helping that.  Time will tell.

To be honest my old programmable Honeywell worked pretty good and kept the temp pretty stable.  I am replacing it because buttons are starting to stop working, it's old, and I like new shiny things that might make my system a bit more efficient.

As best I can tell there isn't much for smarts in the T87, just some built in historesis and a very simple algorithm that utilizes different cycles per hour to determine the dead band.

I'd prefer a "learning" thermostat that can turn the boiler off and on accordingly to maintain a more stable temperature.  

Any suggestions???

ChrisJ

AdmiralYoda said:

After a few days with the digital T87 I'm not so impressed.  Here are some very short term observations:

One cycle per hour:
The outdoor temp was consistently around 20 at night and 30-35 during the day.  The thermostat would call for heat and it would take a while for the boiler heat up the cool radiators.  The thermostat would be satisfied but there would still be plenty of heat in the now HOT radiators and the house would overshoot by 2 degrees. 

Then as the house slowly cooled, by the time the thermostat called for heat the radiators and boilers would be stone cold and it would take a significant time just to start to warm things up.  Meanwhile the thermostat now indicates the room temp is now 2 degrees below the set temp, and the whole cycle repeats itself.  

So overall there is a 4 degree temp swing in which we feel too warm and then too chilly.

3 cycles per hour:
Outdoor temps were 20-low 30's at night and 30-40 during the day.  The indoor temp seems to be more stable but the mild conditions may be helping that.  Time will tell.

To be honest my old programmable Honeywell worked pretty good and kept the temp pretty stable.  I am replacing it because buttons are starting to stop working, it's old, and I like new shiny things that might make my system a bit more efficient.

As best I can tell there isn't much for smarts in the T87, just some built in historesis and a very simple algorithm that utilizes different cycles per hour to determine the dead band.

I'd prefer a "learning" thermostat that can turn the boiler off and on accordingly to maintain a more stable temperature.  

Any suggestions???

I'd recommend a higher end Honeywell. Something in the $100-150 range.  I'm using a Honeywell Prestige.   

Others say the Ecobee is good.

I wouldn't use a learning thermostat because I like to set things the way I want them.

ethicalpaul

The nest or any thermostat is no more likely to die than a safety switch or gas valve on the boiler.

As a software engineer (and no luddite I assure you), I can say with 100% certainty that this is completely false.

AdmiralYoda

Thanks @ChrisJ.  I don't want a thermostat to learn when I'm home, when I'm moving around, etc.

I leave the thermostat at 70 all winter long except if I leave for a significant amount of time.  I just want it to "learn" the ramp rates when the heat is on and the temperature is rising and shut it off at an appropriate time to avoid overshoot.

And also to know how long it takes to make heat, and turn know how fast the room is cooling off and turn on the boiler so things don't get too cold. 

So I guess I want a smart thermostat that learns how to be a better thermostat.  I don't need what the Nest provides, unless it is damn good at being a thermostat...which I haven't heard great things about.

acwagner

You could also try it at 6 CPH and see if that gives you results you're looking for.

Jamie Hall

Permit me to make a comment on @betweentheframe 's praise of computers and the like. Indeed, he or she is quite correct in that most people -- the vast majority in fact -- neither know nor care what code changes are made to their cell phone or computer -- or any of the other whizzy things we use. I am not going to judge whether this is good or bad. However, he also makes the claim that a computerized device is no less likely to fail than a simple gas valve -- and this is simply not true. The failure may not be as obvious -- a gas valve either works or it doesn't -- but it may be far more dangerous for being subtle. This is, perhaps, not so true for a thermostat; most people can tell when they are too cold or too hot -- but the cause can be essentially impossible to fix without replacement. It is more true in more sophisticated devices (computer control of fuel/air ratio, for instance, could easily have lethal results from a minor coding error). And, since the error is buried in the device, it is -- again -- impossible to repair and results in replacement.

I would be among the first to note that the use of more advanced controls can and does have many benefits. However, blind reliance on the magic can and does have many problems (I can think of at least four air crashes as a result, not to mention an uncountable number of automobile accidents) even when it is working properly. Further, dependence on the magic results, almost inevitably, in equal total dependence on the manufacturers of the devices. If it has a problem, you have to go to the manufacturer for replacement. If the manufacturer discontinues the device -- or goes out of business -- you're out of luck.

PMJ

betweentheframe said:

PMJ said:

betweentheframe said:

PMJ said:

@betweentheframe, it sounds like the Nest can zone and provide heat to rooms individually too. How does it do that? I admit, I have a lot of catching up to do.

@betweentheframe said"No, just can put sensors in other rooms and use those instead of tstat for the temp sensing. Much easier than running wires. Like lutron caseta picos-no more 3/4/5 way switch wiring nightmare!" 

So the Nest makes it easier to see on one screen that steam delivery has been uneven, but doing anything about that is done the old fashioned way right? I could use a different temp sensor or average of several with the Nest to turn the boiler on, but once steaming all places get steam just as before as determined by the existing hardware. The only thing I have come across that actually adjusts steam delivery to different places in real time according to changing conditions and evens things out through the same hardware is vacuum.

Looking quickly it seems that Nest doesn't say much or really anything about the logic they use in their unit. Only that it "learns" about you and does a really great job of that. I suppose they can't give away their secret sauce. Being connected to the internet all the time I assume they have the ability to change what they are doing without notifying you. I know, they promise not to do that. I assume you have an old style backup unit you can throw on just in case they make a mistake with an "update" and accidentally shut you down altogether. I would have one ready and practice the switch back at least once.

Don't get me wrong, I am really not against this approach at all. It is all the vast majority of people have to throw at this. I am always studying cause and effect in my system and have to know exactly what is doing what. Obviously that would not be possible with a Nest which they say is constantly changing what it does.

"Do you know what code changes are made to your computer, phone(which is a computer, also nest is a computer), no. Do you use them still and not worry about them dying all the time. Yes. The nest or any thermostat is no more likely to die than a safety switch or gas valve on the boiler. Its a two wire thermostat, if I needed to I’d just pull the nest puck off and put a wire cap on the wires to make a call for heat or wire in a light switch temporarily. They sell nest’s everywhere and same day delivery from amazon, so who really cares. I’ve had several of them, some for 6/7 years and they always worked. My sonos speakers always work. I don’t give it any thought. Obviously a TRV would help with a mechanical change to delivery but the sensors are useful for gauging your balance. But you still have to use your brain and put the system it controls together correctly. It is very good at learning as when I say, change the temp two degrees it tells me it will take 20/30/40 minutes, whatever it says and its always right on. Also if I am not home and it says my system is not responding or it lost power I know I have lost power. Which was super useful when I had a weekend olace in Woodstock." 

I'm quite aware of these things as I own and am ultimately responsible for the operation of a few hundred computer devices - PC's, PLC's, and VFD's all brands all shapes and sizes.

And I do give it a lot of thought as to which I will allow to be connected to the internet and which I will not and what the backup plan is. Using your brain I think you called it.

All this stuff is really great until suddenly it isn't. I think you get that I do use it, all of it, and in much greater volume than most people so I'm not guessing about these things.

The business model(obviously a very successful one) is to get you to spend more and more on the same function which clearly you are at $250 a whack and multiple units since inception what 9 years ago? I sure hope that is in multiple dwellings. The business model is also that the latest and greatest won't run on the current unit - you have to get the new hardware too. Allen Bradley is the king of that game. The new "features" may be great, but what if you don't need them? Just continuing my same functions needs to cost me more and more every year? Enjoy that ride - Nest loves you. I have to play that game a lot. My home Tstat is one place I choose not to.

So I promise you, my pause at jumping on the internet tstat bandwagon is not due to a lack of knowledge of the subjects involved.

Precaud

AdmiralYoda said:

I'd prefer a "learning" thermostat that can turn the boiler off and on accordingly to maintain a more stable temperature.  

Any suggestions???

Get one or two of these.
https://www.ebay.com/itm/Honeywell-TH5110D1022-Digital-Thermostat/254821613592

The seller is a nice guy, ask him to send you ones with latest serial number. (He'll understand because I showed him where to look.)

These units were removed from an assisted living community that "upgraded" to wifi-controlled ones. The units I got were both less than 18 months old and looked like new. I installed one, have one as a spare, and am very pleased.

Precaud

Jamie Hall said:

The concept is fundamentally very simple -- it was a small heater in the thermostat, the output of which could be adjusted to match the characteristics of the room. Not prefect, but astonishingly close.

To do this digitally, however, is not simple, and actually requires a fair amount of computing power.

I don't agree that a "Digital Anticipator" (DA) is all that complicated or requires significant computing power. An analog anticipator is a heating element powered by 24VAC. Its "longer/shorter" adjustment is simply a pot that adjusts how much voltage goes to it; less voltage = slower/longer heatup curve; more voltage = faster/shorter. It "fools" the thermostat into thinking the room is warmer than it really is.

It is trivially easy to mimic this digitally. The Honeywell tstats appear to be doing it; it appears they tie the DA heatup rate proportional to the CPH setting, along with temp differential and cycle time parameters. i.e. CPH = 1 would have the slowest DA curve, widest temp differential, and longest allowable cycle time.

But the curve shape doesn't really have to be mimic'ed. What matters is how long does it take to achieve its desired effect. And that is simply a time delay before the DA offset is added to the room temp reading for that on-cycle. Cycle ends, and the offset is cleared after a similar delay. And that is exactly what I have observed it doing.

The parameters would have to be different when recovering from a setback.

Jamie Hall

The difference between the anticipator and a digital time delay type lies in how they respond to the ambient conditions. If the digital time delay ramp incorporates some means of compensating for ambient conditions -- particularly draughts or an initially cold space -- then yes, they would be more or less equivalent. If the digital ramp does not have a way to do that, however, they aren't.

The anticipator, crude as it may seem, does this automatically, since if it is calibrated properly it will heat its small volume of space in an exact mimic of the radiator across the room -- only it starts earlier (the moment the thermostat calls) and will end earlier (allowing for the residual heat in the radiator).

pecmsg

1 of hundreds of articles concerning NEST issues going back 4 or 5 years.

https://steverotter.com/nest-thermostat-troubleshooting-and-power-issues/

Your happy with it fine, I place them where they belong ................
In the garbage!

AdmiralYoda

So here is an update guys.  It's been a number of days with the thermostat at 3 cycles per hour.

The house is staying a consistent temperature and the thermostat isn't over or undershooting.  What I have noticed is that my basement is 2 degrees warmer than usual.

I think this is because the boiler is turning on more often and the radiators are barely getting warm.  So the thermostat essentially is running more frequently but for less time and the boiler is staying hot and makes steam pretty quick.

Not sure which is more effecient, 1 cycle per hour and screaming hot radiators and then cold rooms long after....or 3 cycles an hour with a boiler staying hot..

Thoughts?

Precaud

Sounds like it's working well. I'll take quick steam production and gentle, consistent heat over screaming hot radiators anyday. Is your NPB insulated?