Ecobee3 Thermostat CPH

Kjmass1

From what I've read here- steam systems are best run at 1 CPH. Would you want to run it less if you could?

I'm finding with the ecobee3, you can set the temperate threshold/band to .5 degree. With this setting, I'm running .75 CPH...more cycles but less run times, about 14 minutes burns. 3 cycles over a 4 hour period. Temps in the 30s right now. Radiators are hot maybe halfway across. Completely different than with the Nest- which had 4-5 degree swings and filled the radiators all the way across.

Temperature has been incredibly consistent, which is also aided by the multiple remote sensors you can use. I keep it set at 72- boiler will fire at 71.5, shut off at 72, and coast to 72.5 (spreadsheet data you can see 5 min updates).

The only disadvantage I can see running this way is more cycles, and boiler being less efficient with shorter run times. Expanding the band will increase temperature swing, pipes will cool off more, more time between cycles.

Anyone else using the ecobee3?

ChrisJ

I'm a bit confused?
You're saying .75cph but describing it as more cycles per hour, not less?

I run my steam system at 2 CPH and have even done 3 CPH if it's cold enough out. With 2 CPH I can get my temperature to stay between 71.6 and 71.9 most of the time thanks to the Ecosteam. There are times it wonders out of that by accident, usually because the thermostat does something weird, or it's windy out but usually that's what I see.

The times I ran 3 CPH it was below 0F outside.

PMJ

I'm confused too for the same reason.

But you are right that more cycles/hour and shorter burns does even out the heat. All these systems were designed with coal fires that had no cycles at all - just continuously flowing steam and rads partially filled to match the conditions. With on/off control the only way to get back closer to this performance is shorter cycles. The on/off air in/out every cycle was a big step backwards from a control standpoint from what was originally there.

I run 3 CPH no matter what and vary only the %on vs off of the burner within those 20min cycles depending on the conditions. My oversized boiler has never needed to run more than 50% of the total time to heat in conditions to -20F outside.

I don't think more cycles are less efficient. The only "wasted" time is the time from each new fire to actual new steam at the rads. That time is directly related to the time since the burner last turned off. For me this time is 1-2 minutes at most if last fire was 15 minutes ago or less. With fewer cycles and longer off times the wasted time increases significantly - I think on net the total is the same or more with fewer cycles.

Those who have a two pipe system can also use natural vacuum during the burner off times to continue pulling steam from the mains into the rads - unlike open vented systems that pull air back into the dry returns and then to the rads during this time instead. Air which just needs to be pushed back out again - delaying the new steam time to the rads even more on each cycle.

Kjmass1

Sorry for the confusion- if you have it set to 3cph- does it always turn on 3 times within one hour...or only on the coldest days as needed?

Is 1 cph an hour between burner off and the next fire time...or can you have a 30 min burn and the next fire be on the next hour (+30 min)?

How many cycles per day do you guys have on an average 30 degree day?

I wish I had my thermostat hooked up during the -10 degree days last week to see how it handled. Missing an explicit cph setting is one drawback but could be easily added in a future update.

Bottom line is house is very comfortable and we'll have to get a couples weeks of data to see how the usage looks. Remote sensors act like zone controls so you can regulate bedrooms at night differently than first floor during the day.

Thanks for your input!

nicholas bonham-carter

A successful setting 3 CPH assumes you have very good main venting, and that the steam will arrive at all the rads at the same time.--NBC

ChrisJ

My issue with 3 cph isn't balance on warmer days it's how the vision pro behaves.

As far as difficulty in balancing a system that close like Marty said "if you put your mind to it you can accomplish anything" .

PMJ

"I shudder to think of the effort necessary to properly setup a 3 CPH system properly."

But that is just it. My system on the piping side is far simpler than anything I read about here. All I did was remove all the vents. I currently do what little venting is required for the whole 1000 EDR system 23 rads and all through one single 1/2" pipe opening on the dry return. That is really it. Maybe it is just the advantage of 2 pipe, but when you consider the original design of these systems both one and two pipe - venting was not the issue. It was not because conditions in the system never did (or possibly could) change quickly. The mains were always full of steam - no air breathing in and out. It was simply impossible to change quickly how much steam/air was in the system like we can today.

The whole idea of hurry up - vent quickly, satisfy stat quickly, runs exactly opposite to how these systems were originally set up to run. A coal fired steam system had no thermostat switch - what would it do? I admit it took me a while to tumble to this. From that point on, the more I tried to mimick the original operation (think well insulated mains always full of steam), the better things got. And when I closed things up and let vacuum form when the burner was off things got even better. I found that the vacuum was slightly stronger in the dry return than the steam mains and that it continued to pull steam from the mains on the off cycle rather than air in from the rooms. In the end, a dramatically better result than what I had when I moved in.

ChrisJ

My thoughts have been different PMJ

I honestly don't care what the original design was for, it's moot in my world. Just as moot as the guys that started the 33% BS years ago. What I care about is making what I have do what I want.

One thing we agree on, steam systems should behave slow. For that matter, all heating systems probably should. Slow to heat, slow to cool means people don't notice the changes. Compare the complete opposite, even the best forced air system provides rapid changes and you definitely feel them.

For a steam system to behave slow, you need a boiler that will allow this. You can use the fastest vents on the planet and the system will still run slow if you feed it steam slow. Feed it a ton of steam and you'll build a lot of pressure unless you get the air out fast enough and now you're back to the fast lane.


Slow and steady most certainly wins the heating race.

ChrisJ

Hatterasguy said:

I can appreciate slow, which by definition requires minimal pressures, but where I have trouble is with balance.

Sure you can balance a SFH that's 1800 square feet with pressure below one ounce. What occurs when you try to feed a four story apartment building under the same conditions? Can you even get steam to the furthest rad in the building? Why would it go all the way out there?

I suspect that attempting to direct steam where you want it in a larger building would be an exercise in futility on one pipe. You get what you get.

This idea of slow and steady is valuable but I fail to see the control capability for it on one pipe.

I would assume trying to make a huge system behave the same as mine would require more pressure at the boiler for similar results.

More pressure at the boiler on one system vs another system doesn't necessarily mean faster and a smaller boiler doesn't necessarily mean "below one ounce".

The pressure at the boiler is almost irrelevant. What matters is the pressure at the radiators.

ChrisJ

Hatterasguy said:

Agreed.

However, to get that pressure at the boiler will generally prevent the use of a "small" boiler. Say, as an example, we use a boiler with a zero pickup factor on a larger apartment building. There is less than one ounce in the boiler room.

You might be in trouble with such a system.

I think you missed the point in what I've been saying.
You need to account for piping losses, always. Especially on larger systems.

But it can't be assumed to be 33%. I've been comfortable recommending 10-20%. 33% would be am absolute max, never over that. But really, to make a system right the piping loss needs to be calculated IMO.

ChrisJ

I don't know.

How did all of the single pipe systems including mine work with a coal boiler? They obviously did, and we all know they didn't run the boiler at 100% from October until April.........


Something tells me if you made a steam boiler that would start slightly high, but then back off and could vary it's output from enough to heat 1 section in every room, to enough to heat all sections in every room, that you could control that with an outdoor reset and vary it's output the entire time.

Instead of changing the temperature of the radiator, you're changing the surface area of the radiator. The outcome is the same, no?

And I believe one thing has been proven. Once you get steam to a radiator, it will continue to slurp the steam out of the main even if pressure drops. The radiator will even create a vacuum, so to speak.

It must have worked with coal, and that means there is no reason it can't work now with gas and oil.

ChrisJ

Yeah,
But no one makes such a beast.

I need 70,000 output sometimes, and only 5,000 other times and everything in between.

PMJ

I think the balancing issues - one pipe or two - are more of a problem when the boiler is off so long that any rads in the system end up with no steam at all in them or even worse when the mains are filled back up with air too. Because when an even partly filled radiator is condensing steam it does create a small vacuum there and if the main is still full of steam it will be slightly higher pressure than the atmosphere so the result at the rad is to pull more steam from the main rather than air from the room through the vent. But if you keep the boiler off long enough to totally condense the steam in the rad then that little vacuum assist is gone and you go to just bringing air from the room back into the system. Once there you need a longer run time and higher pressure from the boiler to get steam everywhere again because you have to push all that air back out. This is why I ended up with more cycles and shorter burns. Calls go on for hours, the mains are always full, at least a few columns of every rad have steam and the air never comes back in. I do it with a very big boiler just pulsing steam into the mains to keep them full.

ChrisJ

PMJ, that would never fly in my house. My radiation is way too big. Your way may work in my house when it's below 20F out, but otherwise not.

Not to mention how picky I am with temperature swing. If it's more than 0.5F or so I get annoyed. More than 1F and I consider the system to be broken. I expect my temperature to remain very close to my set point.

PMJ

Chris, what part wouldn't fly? I have way more radiation and way more boiler than I need to heat the place. And what is your average call time from call to satisfaction? The shorter that is the more the temperature swings. Perfectly even heat means a call that is never satisfied.

Kjmass1

I think that is one advantage to the ecobee3- multiple remote sensors. Typically the thermostat is never placed in the right spot- corner or exterior wall not in a central place like first floor hallway. To be able to average temp sensors from where you place them- living room, cold office, second floor bedroom, goes a long way to help even out the the perceived temp. Even from the floor to ceiling can result in a 2 degree swing.

Even better, at night you can have it ignore the thermostat sensor and only use remote sensors in the bedrooms. Our bedrooms used to get too hot at night because by the time the thermostat was turned off, the bedroom rads would be scorching. Put the sensor close to the radiator to shutoff boiler once it gets hot and let it coast to prevent swings.

ChrisJ

PMJ said:

Chris, what part wouldn't fly? I have way more radiation and way more boiler than I need to heat the place. And what is your average call time from call to satisfaction? The shorter that is the more the temperature swings. Perfectly even heat means a call that is never satisfied.

Not sure what "average call time from call to satisfaction" means?

Typical preheat times are 2 to 3 minutes but drop down to 90 seconds in extreme cold. Preheat being the time from when the thermostat calls for heat until steam hits the end of my long main.

Doing 2 CPH :
In very mild weather I'll see a 3 minute heating cycle. In cold weather 8 to 10 minutes. In extreme cold, 25 to 30 minutes.

As I said, my demand is as low as 5,000 btu/h to as high as 70,000 btu/h.

PMJ

ChrisJ said:

PMJ said:

Chris, what part wouldn't fly? I have way more radiation and way more boiler than I need to heat the place. And what is your average call time from call to satisfaction? The shorter that is the more the temperature swings. Perfectly even heat means a call that is never satisfied.

Not sure what "average call time from call to satisfaction" means?

Typical preheat times are 2 to 3 minutes but drop down to 90 seconds in extreme cold. Preheat being the time from when the thermostat calls for heat until steam hits the end of my long main.

Doing 2 CPH :
In very mild weather I'll see a 3 minute heating cycle. In cold weather 8 to 10 minutes. In extreme cold, 25 to 30 minutes.

As I said, my demand is as low as 5,000 btu/h to as high as 70,000 btu/h.

I mean what is the time from when the thermostat calls for heat to when it is satisfied. This is the time it takes for the room temperature to travel from the low end of the deadband to the high end. The faster this is accomplished the more the temperature in the room is swinging. This time for me is hours. After I get a call for heat at the low end of the deadband I try to make it take a very long time to get to the high end.

Don't take all this the wrong way - I'm not making a judgement about anyone's system. I am considering this just a theoretical discussion. In theory, the more even the temperature in the room the fewer cycles the thermostat would make from call to satisfaction. Absolute perfection would be after the very first call the system would move the temperature to the middle of the deadband and keep it right there - never ever being satisfied. To accomplish this the rads would have to be partly filled all the time - creeping slightly fuller as it got colder and slightly less full as it got warmer outside. This is in fact the way the coal systems ran. The fire was damped more and less by pretty sophisticated pressure sensing mechanisms to maintain always a very low pressure in the main. The amount of steam required to do that varied with the outside conditions.

ChrisJ

@PMJ
That depends on what the ambient temp is outside.
The Ecosteam also messes with this because it shuts the burner off often 5 to 10 minutes before the thermostat is satisfied.

I'm going to say on your typical 20-30F day from start to finish 10 to 15 minutes for the thermostat.

Like I said, my temperature stays very close to my set point. My thermostat has been set to 72F and a thermometer right next to it generally goes between 71.6 and 71.9.

PMJ

ChrisJ said:

@PMJ
That depends on what the ambient temp is outside.
The Ecosteam also messes with this because it shuts the burner off often 5 to 10 minutes before the thermostat is satisfied.

I'm going to say on your typical 20-30F day from start to finish 10 to 15 minutes for the thermostat.

Like I said, my temperature stays very close to my set point. My thermostat has been set to 72F and a thermometer right next to it generally goes between 71.6 and 71.9.

Chris,

I'm sure your results are just fine. I'm just pointing out that if you put enough steam into your rads to raise the room temp .3 degrees in 15 minutes that is at a rate of 1.2 degrees per hour. The amount of steam that must be put into your rads to do this is considerably beyond what is required to offset the current demand (heat loss to the outside). That means the system must then stop and allow the rads to cool off considerably to a point below what is required to match the demand. I'm just saying that a "perfect " system only puts enough steam in the rads to match the current demand at all times. The closer this match is the longer the calls for heat will be.

My system is far from perfect. But my goal is an endless call for heat and rads which are basically never crazy hot and also never at room temperature.

ChrisJ

PMJ said:

ChrisJ said:

@PMJ
That depends on what the ambient temp is outside.
The Ecosteam also messes with this because it shuts the burner off often 5 to 10 minutes before the thermostat is satisfied.

I'm going to say on your typical 20-30F day from start to finish 10 to 15 minutes for the thermostat.

Like I said, my temperature stays very close to my set point. My thermostat has been set to 72F and a thermometer right next to it generally goes between 71.6 and 71.9.

Chris,

I'm sure your results are just fine. I'm just pointing out that if you put enough steam into your rads to raise the room temp .3 degrees in 15 minutes that is at a rate of 1.2 degrees per hour. The amount of steam that must be put into your rads to do this is considerably beyond what is required to offset the current demand (heat loss to the outside). That means the system must then stop and allow the rads to cool off considerably to a point below what is required to match the demand. I'm just saying that a "perfect " system only puts enough steam in the rads to match the current demand at all times. The closer this match is the longer the calls for heat will be.

My system is far from perfect. But my goal is an endless call for heat and rads which are basically never crazy hot and also never at room temperature.

This is the Ecosteam's job.
As I've said in other threads, my radiators act as filter capacitors.

The Ecosteam predicts how much energy to put into the radiators. Without the Ecosteam, it's a guessing game and the thermostat will overshoot most of the time.


I get what you're saying and I think I agree.
Just I don't think I could keep one section of my radiators full all of the time a lot of the season without overheating.

LarryK

I have an ecobee 3 and it has a setting for minimum on time which has a similar effect to CPH, I think.

Kjmass1

Pretty sure a lot of those settings are for forced air and are not available for radiant heat?

LarryK

One pipe steam here. I have mine set for 15 min but It always fires for 20 minutes minimum. The best part of the Ecobee is looking at the usage graph online. I've noticed the temp takes a 1 degree dive whenever the boiler stars firing. That must be from cold air being sucked into the house by the boiler. Where do I go to find out about adding an external combustion air supply? I should start a new topic and ask.