Will Limiting On-Off Cycles Save $$$

dennis53

I noticed you have a Lux TX-500E thermostat with a 1* differential. Perhaps you could set your differential lower-more like .5 or even .25*. I believe that thermostat has a range of 1-9 with each number representing .25*. Do you have it set on number 4 (1*) or on number 1(.25*)?
If you already have it set on number 1, then never mind

FXProglJr

It's set at #4.....I wanted a 1* differential.... think that's a pretty close tolerance.....wouldn't a smaller differential cause the furnace to cycle more often?

My initial thought was to stop the furnace from coming on if the radiators were still hot from the last cycle and, therefore, still adding heat to the room.

NOTE: after recovery from the night time setback (which I'm not concerned about), it seems that the furnace always cycles (on pressure) 2 or 3 times before satisfying the thermostat. The result of that (I think) is the room temperature is not as constant as it could be

Captain Who

Hatterasguy said:

On my hot water system with CI rads, I have the Honeywell CT3500. It learns the rate of climb and the overshoot and then cycles itself during the climb to prevent any overshoot. Unlike most other 'stats, you can hear it open and close several times during the climb.

Watch out! Fred and MarkN may tell you that no digital thermostat can possibly do that and they are only temperature controlled switches I received quite a bit of criticism from them for suggesting that an algorithm in my White Rodgers 1F97 may be learning the rate of descent and determining the variable off time in advance and using that calculation to fire up the burner for the next series of on cycles. The giveaway was that the on and off times were in exact to the second 1 minute increments. That's a dead giveaway that there is an algorithm at work, not just a temperature controlled switch.

nicholas bonham-carter

FX, are you sure you have enough venting on those mains? Gorton #1's seem undersized for the lengths of those mains. Since you have a low pressure gauge, see what pressure is showing during the venting phase, (back-pressure of venting). Compare it with the vents removed, so you know what the open pipe pressure is.
You may or may not be able to down fire the burner, but you can certainly do something about letting the air out as quickly as possible!--NBC

Captain Who

Hatterasguy said:

My only criticism of them is the fact they the temperature sensor is slow to respond to the room change. It's very accurate, but a mercury 'stat placed right next to the CT3500 will show a two degree differential on a climb. The CT3500 is always lagging. Once equilibrium is established, both 'stats read within .5 degree.

I have noticed a LOT of discrepancies between the display readout on the White Rodgers 1F97 and two different digital thermometers with 0.1 F resolution, which are placed on top of the thermostat. When I come down in the morning before the recovery has taken place, all 3 are "fairly close" in readings. That is the ONLY time that is true. When the system has been running the two digital thermometers can read around 3 to 5 deg higher than the display and disagree between each other by as much as 0.5 to 1.0 F. I think that different thermometers / sensors vary GREATLY in their response times and even more so their sensitivity to radiant heat as opposed to convection heat or air temperature.

Mark N

Ok lets now confuse Honeywell's "Intelligent Recovery" feature of their set back thermostats, with how a thermostat functions when maintaining the set point.

Captain Who

Awww come'on Mark N, don't be a thermostat snob. You put it in quotes but you got it wrong. Their marketing lingo is "Smart Response Technology". The point that Hatterasguy and I made is that digital thermometers today are like computers. They employ whatever algorithms their designers saw fit to instill upon them. They most definitely are not just temperature controlled switches and they most definitely CAN detect rate of change of temperature and use that information as input data to their algorithmic control software. The White Rodgers 1F97 has a similar function when in recovery mode where it tries to hit the desired setpoint at the desired programmed time. Do you really believe that Honeywell has a lock on the ability to detect rate of change of temperature in a digital thermometer?

I don't want to hijack this thread so I won't go on.

Captain Who

PS: If you're curious, White Rodgers calls it "Energy Management Recovery (EMR)". OK I'm done.

Fred

I'm not even going to get back into that discussion with you Captain Who. I already told you if you are happy with your data, and it is consistently repeatable (even with a 3 to 5 degree variance from the other digital thermometers) I'm happy for you. The issue we were trying to address with you is all your heat cycles were around 4 minutes (with 30 minutes to hours of off time) which just isn't enough time to heat water, make steam, fill the mains and heat the radiators. But I digress. It's cool with me!

Captain Who

Ahhh Fred Fred. Why don't you put it back in the other thread where we don't hijack this one. You didn't even bother to read the thread carefully before you called into question my ability to read a clock to the nearest second, or worse still, my integrity. It WASN'T a single 4:47 heat "cycle" that put the steam in the radiators, it was TWO back to back heat "cycles" of 4:47 each, so you are off by a whole 100%. I guess you are the board curmudgeon who is very set in his ways and his knowledge of steam systems (considerable) but I don't like being wrongly criticized or told my data must be faulty.

Fred

No comment. Let's move on.

Captain Who

Can't move on without an apology buddy

Fred

Not gonna happen, my friend, Get over it.

Captain Who

OK. That would be the proper thing to do, but I guess instead you will go back and alter your posts to save face, like I have seen you do recently. To each his own, too bad.

dennis53

I think you are correct in saying a smaller differential on the thermostat will decrease the run times and increase the number of cycles, but the boiler will be cycling on the thermostat and not on pressure,
I have found a lower differential results in lower temperature swings and more even heat, although deep setbacks are still a problem. Lower differential results in less over-run.

FXProglJr

well....it's another heating season and I'm back at it. And yes, I realize my burner is oversized - 471 sq.ft rated and 316 sq,ft connected - but I inherited the building that way and am not looking to replace it until I have to). What I had in mind is a little setup that will detect a pressuretrol system shutdown and not let the system restart for a preset time. I'm thinking that when the system is up to pressure, all the cast iron radiators should be hot (190*F or so). I can measure the time it takes them to cool to say 100*F and use that as the preset time. This allows a flexible time on/off as needed by the weather, but the number of restarts will be limited (that has to save some money) and the system will not overshoot the set temperature by as much (that has to make it more comfortable).

Any thoughts?

I've been keeping gal/degree day data so once I get this built and installed, I'll let you guys know what effect it has.

PMJ

FXProglJr said:

well....it's another heating season and I'm back at it. And yes, I realize my burner is oversized - 471 sq.ft rated and 316 sq,ft connected - but I inherited the building that way and am not looking to replace it until I have to). What I had in mind is a little setup that will detect a pressuretrol system shutdown and not let the system restart for a preset time. I'm thinking that when the system is up to pressure, all the cast iron radiators should be hot (190*F or so). I can measure the time it takes them to cool to say 100*F and use that as the preset time. This allows a flexible time on/off as needed by the weather, but the number of restarts will be limited (that has to save some money) and the system will not overshoot the set temperature by as much (that has to make it more comfortable).

Any thoughts?

I've been keeping gal/degree day data so once I get this built and installed, I'll let you guys know what effect it has.

The best way to control overshooting is to not let the radiators ever fill enough to trigger a pressure shutoff in the first place. They never need to be that full and the original coal boiler on these systems never filled them full. Obviously coal boilers did not have on/off control. The fire was modulated with a pressure controlled damper on the fire. If you really want to prevent overshooting with an on/off control you simply can't let your boiler run that long. Especially since yours is oversized you need to pace the boiler on and off whenever the tsat is calling for heat and give the distributed steam time to dissipate into the rooms between cycles. My vaporstat is a safety shutdown only.

FXProglJr

my primary objective was to reduce oil usage....uneven heat during the day was not a problem but smaller swings would be an added benefit. That said, are you saying that once the furnace starts, I'd be better off forcing the burner to cycle on and off (I'd have to figure out the best duration for each) until the thermostat is satisfied?

FXProglJr

no gas....it's oil fired

FXProglJr

no downsizing yet....I'll look into that...thanks

FXProglJr

the boiler is a PEERLESS ECT-04-125 and
the burner is a RIELLO 40F5
here is a 1.25 gph nozzzle

FXProglJr

WOW...thanks much for sharing your knowledge

PMJ

FXProglJr said:

my primary objective was to reduce oil usage....uneven heat during the day was not a problem but smaller swings would be an added benefit. That said, are you saying that once the furnace starts, I'd be better off forcing the burner to cycle on and off (I'd have to figure out the best duration for each) until the thermostat is satisfied?

Yes. That is what I am saying.

FXProglJr

Thanks for your insight

Jamie Hall

There are, fundamentally, two ways to control the output of an oil fired boiler so that it matches the capacity of the radiation (which has to happen). One, adjust the firing rate. Most boilers have a range of acceptable firing rates. If it reaches a pressure set point while it is maintaining a given temperature, down firing -- lowering the firing rate -- will help (this is not true of recovering from a setback; that will almost inevitably result in cycling on pressure eventually). The other is to turn the boiler on and off -- which amounts to much the same thing in the end, but is slightly less efficient. That is the function of the pressurestat or vapourtrol. The boiler fires and the radiation becomes full. At that point the pressure begins to rise, so you sense that and turn the boiler off until you need more steam.

Take your pick...

FXProglJr

turn the boiler off until you need more steam

yes, I understand...and I'm going to look into downfiring my boiler....but to respond to your comment, my initial thought was that, when the thermostat calls for heat, the system fires, gets up to 1-1/2 lbs pressure in about 20 minutes and the pressuretrol stops the firing. After the pressure drops back to the cut in pressure (about 2-1/2 minutes), if the thermostat is still calling for heat, the burner will turn on even though the cast iron radiators are still hot and adding heat to the room. On most 2nd cycles the thermostat gets satisfied before the system get up to the cut-out pressure again. I was thinking that the thermostat would have made it to the set temp without adding more steam. And, by delaying the second firing I could save some fuel and maintain a more even temperature. (I'm a tinkerer and would have enjoyed trying this)

But, there's nothing like experience so I'll go with the suggestions provided here

Thank you to all for your input

PMJ

Jamie Hall said:

There are, fundamentally, two ways to control the output of an oil fired boiler so that it matches the capacity of the radiation (which has to happen). One, adjust the firing rate. Most boilers have a range of acceptable firing rates. If it reaches a pressure set point while it is maintaining a given temperature, down firing -- lowering the firing rate -- will help (this is not true of recovering from a setback; that will almost inevitably result in cycling on pressure eventually). The other is to turn the boiler on and off -- which amounts to much the same thing in the end, but is slightly less efficient. That is the function of the pressurestat or vapourtrol. The boiler fires and the radiation becomes full. At that point the pressure begins to rise, so you sense that and turn the boiler off until you need more steam.

Take your pick...

Jamie,

When you say downfire to match the radiation aren't you still are left with a firing rate that will heat the house on the coldest day designed for? That same firing rate is way more than is required on the average day. That boiler on the average day will still need to be stopped on pressure during each call and will overshoot the space it is heating by some amount for sure. And there will be a longer wait for the next call and a longer than necessary preheat time when the next firing does come. As I understand it the OP here is wishing to minimize this swing. It is exactly the problem addressed by Ecosteam.

Short of investing in that kind of sophisticated control or in a fully modulating burner I maintain that the best way to have partially warm radiators all the time radiating the appropriate amount of heat to most closely match the actual real time demand is simply to pulse the boiler on and off - that is spread out the run. Try to spread it out so much that the call is never satisfied or at least goes on for hours. I don't know about one pipe but I think operating this way is more efficient in two pipe if you take advantage of natural vacuum between each and every cycle.

PMJ

FXProglJr said:

turn the boiler off until you need more steam

yes, I understand...and I'm going to look into downfiring my boiler....but to respond to your comment, my initial thought was that, when the thermostat calls for heat, the system fires, gets up to 1-1/2 lbs pressure in about 20 minutes and the pressuretrol stops the firing. After the pressure drops back to the cut in pressure (about 2-1/2 minutes), if the thermostat is still calling for heat, the burner will turn on even though the cast iron radiators are still hot and adding heat to the room. On most 2nd cycles the thermostat gets satisfied before the system get up to the cut-out pressure again. I was thinking that the thermostat would have made it to the set temp without adding more steam. And, by delaying the second firing I could save some fuel and maintain a more even temperature. (I'm a tinkerer and would have enjoyed trying this)

But, there's nothing like experience so I'll go with the suggestions provided here

Thank you to all for your input

Hat is right - this is what Ecosteam does. But if you want to tinker you are on the right trail with what you say. I'm just suggesting that you think about delaying (spreading out) the first firing too. Perfectly even heat means that the temperature always sits in the deadband of the tstat and the call is never satisfied. You just need to fire enough that the temp rises slowly and doesn't fall.

KC_Jones

Hatterasguy said:

You, my friend, are simply begging for an Eco-Steam steam enthusiast's boiler control. It does exactly what you are seeking to accomplish.

@MarkS sells 'em. ChrisJ and KC use them with great success.

Love mine. It decides how much heat you really need and fires the boiler accordingly. So if it has calculated a need for 15k BTU it fires your boiler long enough to put out that much then goes into a holding pattern to let the steam work, if the thermostat satisfies during this hold period then no more firing. If the stat still isn't satisfied it will fire again according to the cycle time you have set. I am running a true 2 CPH on mine right now so if the boiler fires for 10 minutes it will hold for 20. It's pretty rare (once you get it tuned in) that it does't satisfy in that time frame. It also tracks savings by tracking the length of time the stat was calling for heat versus how much time it actually fired the boiler. So far this season I am showing 30 hours of "savings" with 228 hours of boiler run time. I can't complain at all. My system NEVER over shoots with this setup even when doing 4 degree recoveries in the morning. For this you can set a recovery boost so that it detects the indoor temp and knows by the differential that you are in recovery and allows extra run time for this. All parameters are user adjustable to suit your needs. @MarkS built a quality product that works fantastic.

PMJ

Hatterasguy said:

PMJ said:

When you say downfire to match the radiation aren't you still are left with a firing rate that will heat the house on the coldest day designed for? That same firing rate is way more than is required on the average day. That boiler on the average day will still need to be stopped on pressure during each call and will overshoot the space it is heating by some amount for sure.

There is a little confusion here.

If the boiler's size matches the radiation (with a small pickup factor), it will never trip on pressure. It will run forever and supply it's gross output to the radiation as long as the 'stat is closed.

It is, of course, agreed that this will overheat the building in just about every case as most buildings have more radiation than they need even on the design day.

Most boilers that have the traditional 33% pickup factor will trip on pressure as the ambient drops and they run for a longer period of time and fill all the radiation. Those that have a pickup factor of, say 15% or less will never trip on pressure no matter how long you run them. I have one of those.

I agree there is confusion. The boiler's ability to fill the rads and trip on pressure is related to the rate at which heat leaves the rads and flows into the room and then to the outside. The colder it is outside the higher this continuous rate of flow is. When you pass design temp outside and the rads can no longer radiate enough heat to hold the room temp the rate of heat leaving the rads increases even further because the temperature in the room is dropping. At some point steam is condensing so fast in the rads that the boiler can no longer supply the amount of steam required to trip on pressure at all. Going the other way when it is hot outside(think running the boiler in the summer) that same boiler will fill the system very quickly and trip on pressure quickly. Your 15% pickup boiler will trip on pressure if the room temp gets warm enough. It is not just about installed radiation - it is very much about demand too.

ChrisJ

I did a 9 degree recovery when it was in the teens out and had no overshoot with the Ecosteam.

Luckily, because my boiler is sized right I can run for a long long time and not build much pressure. And if for some reason I hit 2 "WC it'll trip the Ecosteam into hold mode for 10 minutes and let the radiators dissipate some of the heat. After all, 1 ounce is way out of line, we can't have that kind of roughhousing going on in my system.

Not sure if that 2 "WC trip point will cause issues, but it hasn't yet. The most I've seen this year is 0.50"WC.

PMJ

null
Careful now Hat. The rate at which heat leaves the rad can't be constant and is related to the outside temp. That is because the colder it is outside the faster heat leaves the room. The faster it leaves the room the faster it must leave the rad in the room to keep the room at temp.

This fact is plainly evident because the colder it is outside the fuller the rad must be to heat the room. On a mild day it need be only filled partly across. On design day it needs to be completely full. That same rad is radiating very different amounts of heat, the steam is the same temp, the room is the same temp, the only difference is the outside temp.

If you are talking about only totally filled rads then I guess I agree. But we never need totally filled rads! Totally filled rads on an average heating day are the definition of overshooting.

hvacfreak2

PMJ said:

null

Careful now Hat. The rate at which heat leaves the rad can't be constant and is related to the outside temp. That is because the colder it is outside the faster heat leaves the room. The faster it leaves the room the faster it must leave the rad in the room to keep the room at temp.



This fact is plainly evident because the colder it is outside the fuller the rad must be to heat the room. On a mild day it need be only filled partly across. On design day it needs to be completely full. That same rad is radiating very different amounts of heat, the steam is the same temp, the room is the same temp, the only difference is the outside temp.



If you are talking about only totally filled rads then I guess I agree. But we never need totally filled rads! Totally filled rads on an average heating day are the definition of overshooting.

I think Heat Timer ( controls ) got their start based on this , right ?

PMJ

Hattersguy said:

I do need to clarify one point.

The rate of heat distribution to the room for a steam radiator is always changing due to the fact that it is never (or rarely) filled with steam. The rate is increasing throughout the cycle due to the radiator gradually filling during the cycle.


Not sure why my quote thing isn't working but I say:

You can't have it both ways. You admit that the radiators are never full of steam. A radiator only a little filled is delivering steam at a slower rate to the room (as in btu per hour) than one that is more full plain and simple. The old cold fired control systems could not change the amount of steam in the radiators quickly. They were partly filled all the time to an amount to match the radiation required to match the heat loss of the room. Sophisticated pressure measuring devices working in ounces of pressure changed the amount of steam delivered (consequently the amount of rad fill) very gradually and the btu/hr delivery rate of each rad to the rooms changed very gradually. That is the whole point here. Even heat requires constantly varying btu/hr heat delivery from the rads not a constant one. And the more gradual the change the better.

This point is critical to be understood by anyone trying to even out their heat. In the perfect system (one where the room temp was absolutely fixed at one temperature) how would radiators have to perform to accomplish this? Their heat output to the room would NEVER be constant. The rads would very gradually fill and become less full providing a little more or a little less heat to the room per unit time to match what the room is losing to the outside. Obviously perfection is impossible. But this is the behavior in the rads we need try to create to provide the most even heat.

In my education about steam when I discovered how terribly inferior on/off control was to the original system installed in my house in 1926 I was really shocked. The MarkS narrative about how he developed Ecosteam to address this very subject describes it the best I think.

PMJ

null
Yes to hvacfreak2 you are right.

Tolik

I'll start out saying that I have mixed feelings about my Nest thermostat. One thing I will say is it does work calculating how long the boiler should be on to heat the home. Sounds exactly what you need. It basically calculates how long it takes to warm up the house and will know to turn the boiler off early and let the radiant heat do the work. They call it, not surprisingly, radiant heating.

KC_Jones

Does the Nest have an outdoor temperature sensor? Without that it can't do what you say reliably, it's just "guessing".

ChrisJ

KC_Jones said:

Does the Nest have an outdoor temperature sensor? Without that it can't do what you say reliably, it's just "guessing".

No outdoor sensor.
I *think* it may use local weather reports, but I'm not even sure of that. The fact it locked up for no reason in the first hour is the reason I ditched mine.

The Ecosteam doesn't do that and if I ever have a problem, or want a feature Mark see's what he can do. I'd also bet the PLC is a lot more reliable and durable than a Nest.

MarkS

KC_Jones said:

Does the Nest have an outdoor temperature sensor?".

I believe the Nest fetches the outdoor temperature from the internet based on its location.

ChrisJ

Hatterasguy said:

PMJ said:

You can't have it both ways. You admit that the radiators are never full of steam. A radiator only a little filled is delivering steam at a slower rate to the room (as in btu per hour) than one that is more full plain and simple.

Fair enough.

Steam systems are unique as the rate of delivery climbs with TIME. Unlike a hot water baseboard system where the rate is constant with time.

Understand, however, that it does NOT climb with outdoor temperature. The steam system will deliver the same number of BTU's in 15 minutes when the ambient is 50°F as it will when the ambient is 0°F.

If we agree on this then we're good.

I disagree.
The walls behind my radiators are a whole lot cooler when it's 0F than when it's 50F. That ice cold wall is just sucking the IR right out of the radiators.

Even an insulated wall would change too, so I can't agree in any structure.

Also, the temperature obviously doesn't have to change a degree to change the output of a steam radiator. If it changes 1/100 of a degree the output changes.