Frequency and Length of Steam Cycles?

wanttolearn

My house is heated with steam radiators. The entire steam system is on one zone, operated by a Honeywell digital thermostat.

When if first moved into the house a few years ago, I noticed that the boiler would often short cycle. It turned out that the thermostat was set on a too sensitive setting, and it shut off well before the steam got to all the radiators. I fixed that my changing the setting on the Honeywell to Steam sensitivity, and now it works much better, i.e. the heating cycle stays on long enough for the radiators to get warm.

But by doing so, I have caused an opposite problem now. Because the thermostat is less sensitive, it comes on much less frequently than before. I would estimate that on a typical winter day (outside temp 35 degrees or so), the boiler only comes on once every four hours or so, for a total of 5 to 6 heating cycles per 24 hour period. When the weather gets very cold (sub 20) the cycles get much more frequent than that, but those days are the exception, not the rule.

I would like to know what is the typical frequency for a steam system. How often should it come on per day? And how long should each heating cycle last? Mine last only approx 30 mins each before the boiler turns off again. My house has average levels of insulation and air tightness.

The reason for asking is that the house feels quite cold on days that the heating cycle comes on infrequently. After a few hours of no new heat, it gets quite uncomfortable until the next cycle comes along. But according to the thermostat, the temperature has not yet dropped to turn on the system.

To optimize my steam system, should I change the settings on the thermostat and make the cycles more frequent again? I am concerned that by doing so, I will cause short cycling problems again.

Any thoughts and insights are appreciated.

KC_Jones

If the thermostat is happy then the system won't run. Setting it for more cycles won't change that. As far as frequency and run times that all depends on the house. At 35° OAT the run times and frequency don't seem that unusual to me. At 55° OAT my system will fire in the AM and then shut down for almost the entire day. I have seen mine off for extended periods at the temps you are referring to. The reason you are feeling cold is because you aren't feeling the radiant energy off the rads as they are cool from being shut down for so long, but the air temperature is still where it is supposed to be. This is the difference between warm air and radiant energy. The radiant is like the feeling of the sun on your face on a cold day....the air is cold, but you feel nice and warm. I don't think there is much that can be done about this. What temp do you set your system to?

Fred

Most steam systems run at 1 or 2 cycles per hour. If you have a Honeywell, it should be programable based on type of heat. It sounds like you have the Round Honeywell with the anticipator, rather than the set up program. My boiler runs once an hour (if the thermostat calls for heat (typical temp swing around 1 to 1.5 degrees between cycles) The boiler will run for about 15 to 20 minutes on days when the outside temp is in the 20's or 30's. It runs maybe 35 to 40 minutes when the temp is 0 or wind chills are below 0.
Some use the 2 cycle setting on their thermostats. That gives you two shorter cycles per hour that run about 10 Minute heating cycle each. That tends to even the temp swings out.
I think you have your heat anticipator set for way to much temp swing.

Jamie Hall

How cold is cold? That's a perpetual question! Since the thermostat stays off, I would guess offhand that it may be in one of the warmer spaces in the house? You might want to consider whether it might be better located in some other room, perhaps.

As KC said, you situation and experience doesn't seem that odd to me -- the place I care for here does much the same thing. Paradoxically, it often seems more comfortable on colder, cloudy days -- when the boiler runs more often.

KC_Jones

Jamie Hall said:

How cold is cold? That's a perpetual question! Since the thermostat stays off, I would guess offhand that it may be in one of the warmer spaces in the house? You might want to consider whether it might be better located in some other room, perhaps.

As KC said, you situation and experience doesn't seem that odd to me -- the place I care for here does much the same thing. Paradoxically, it often seems more comfortable on colder, cloudy days -- when the boiler runs more often.

My wife often wishes for colder days because of this! Those rads staying a little toasty all day long increases comfort. The shoulder times upper 30's to low 50's "feel" the coldest in my house, but the temp is still the same.

KC_Jones

I have EcoSteam for that now...Honeywell is just a switch and a program at this point.

KC_Jones

Yep like I said it's basically just a switch and a program. What it is actually controlling now is limited. We are hijacking this thread now.

KC_Jones

To the OP are all rooms in your house a similar temperature? Where do you have the Tstat located? Sometimes this can be a tuning issue and sometimes it's like I said the Tstat is happy. A lot of us on here try and put the Tstat in a room with a slower venting scenario OR a cooler room to maximize run times and comfort. If you have significant temperature variations or keep the Tstat in a warmer room it can also affect the overall comfort level. Is this a digital or analog Tstat?

wanttolearn

Thanks for all the early feedback. Wanted to answer some of the points: I set the thermostat to 71 degrees at all times. Yes, the room with the stat is slightly warmer than some other parts of the house, but not dramatically so. The coldest room in the house is probabably 69 degrees, and there are parts of the house that are 73 degrees, so i don't want to turn the stat any higher, otherwise those hotter room get too hot.

It is a digital stat, not one of the old round analog ones. It has a few settings for different kind of heat: forced air is the most sensitive setting, and steam heat is the most insensitive, i.e. widest temp swings. and there are a few settings in between.

i do not use the anticipator function on the stat, so that is not the issue.

i agree with KC Jones that the coldest feeling in the house is on days when the temp is between 35 and 50, because the radiators only go on a couple times a day.

it sounds to me based on the varied posts that there is no "standard" for how often radiators should heat up? I guess I could experiment with a tighter differential setting, and see what the result are.

Abracadabra

Throw a slower vent in the room with the thermostat. Make sure your main venting is adequate. If after taking care of main venting you have rooms that are still a little bit cool, you can adjust those radiator vents.

ChrisJ

Hatterasguy said:

MarkS said:

Theoretically there's no reason it can't. If you jumper the thermostat input there'd always be a "call for heat", and it would run like a typical ODR control.

I like that approach. Let the ODR control the entire operation. Takes a bit of effort to get the curve dialed in but beats the need for a 'stat to determine when it runs.

Doesn't take as much as you think.
I've had mine run that way a few times without much effort. However, personally, I feel it's correct when the thermostat is never satisfied and yet the house stays the correct temperature with high winds. This way, it always maintains the correct temperature windy or not. Also, how do you factor in the effect of the sun without some sort of indoor sensor?

If that's how the Tekmar works then forget it.

crawas

wanttolearn said:

My house is heated with steam radiators. The entire steam system is on one zone, operated by a Honeywell digital thermostat.

When if first moved into the house a few years ago, I noticed that the boiler would often short cycle. It turned out that the thermostat was set on a too sensitive setting, and it shut off well before the steam got to all the radiators. I fixed that my changing the setting on the Honeywell to Steam sensitivity, and now it works much better, i.e. the heating cycle stays on long enough for the radiators to get warm.

But by doing so, I have caused an opposite problem now. Because the thermostat is less sensitive, it comes on much less frequently than before. I would estimate that on a typical winter day (outside temp 35 degrees or so), the boiler only comes on once every four hours or so, for a total of 5 to 6 heating cycles per 24 hour period. When the weather gets very cold (sub 20) the cycles get much more frequent than that, but those days are the exception, not the rule.

I would like to know what is the typical frequency for a steam system. How often should it come on per day? And how long should each heating cycle last? Mine last only approx 30 mins each before the boiler turns off again. My house has average levels of insulation and air tightness.

The reason for asking is that the house feels quite cold on days that the heating cycle comes on infrequently. After a few hours of no new heat, it gets quite uncomfortable until the next cycle comes along. But according to the thermostat, the temperature has not yet dropped to turn on the system.

To optimize my steam system, should I change the settings on the thermostat and make the cycles more frequent again? I am concerned that by doing so, I will cause short cycling problems again.

Any thoughts and insights are appreciated.

this is my EXACT problem. how can i set my honeywell thermostat to be less sensitive and stay on long enough for the 2nd floor radiators to get some steam? as it is now, the boiler shuts off before it even touches 2nd floor radiators. they all have gorton c valves and my therm is set on 70 permanent hold.

ethicalpaul

Slow down the venting on the radiators near the thermostat

crawas

the radiator in the room of the thermostat is a gorton 4 valve and doesnt get hot at all.

Fred

What you are describing is typical of a steam setting during what is called the "shoulder season" that period when the outside temp is reasonably mild and the indoor temp doesn't drop enough to cause the boiler to kick on as frequently as you'd like. A steam setting on the thermostat is 1 cycle per hour (if the indoor temp drops enough to call for heat). Many people get around that issue and achieve a more even temp by setting the thermostat to hot water heat which is 2 cycles per hour or even 3 cycles per hour. What that does is reduce the temp swing for the call for heat. Try one of those settings and see if that resolves your issue.

crawas

I don’t think My thermostat has a setting for hot water heat. It has conventional forced air, radiant heat, heat pump, and other. It’s the Honeywell th8320 and I have it set to other with 1 cycle per hour. The boiler cycled on just now and it was barely on 15 minutes. It’s fairly cold here in NY. Like 25 degrees today.

Fred

Try setting it to radiant (which is hot water) and set it to 2 cycles per hour.

crawas

As a side note, all 2nd floor rads have gorton C valves and 1st floor ones have 4, 5, or 6 gortons

Fred

Don't worry about the radiator vents until the main venting is fixed, then you can balance the radiators with different vents, if needed.

crawas

How many radiant stages do I set to?

ethicalpaul

> @crawas said:
> I don’t think My thermostat has a setting for hot water heat. It has conventional forced air, radiant heat, heat pump, and other. It’s the Honeywell th8320 and I have it set to other with 1 cycle per hour. The boiler cycled on just now and it was barely on 15 minutes. It’s fairly cold here in NY. Like 25 degrees today.

OK but what was the temperature at the end of the 15 minutes according to the thermostat vs its setting

crawas

The thermostat never changes. I never see it go above or below 70 but the issue is the second floor.

ethicalpaul

> @crawas said:
> the radiator in the room of the thermostat is a gorton 4 valve and doesnt get hot at all.

Gotcha. Well something is getting 70 degrees to the thermostat, satisfying it. You have to make whatever that is to get hot slower. Then the thermostat will ask for heat more and your cold places will get more.

Is the temperature actually 70 there or is your thermostat lying? Is there some other heat source near it? Is it just getting heat from a giant radiator 8 feet from it? Something is heating that air.

crawas

It’s a central part of the house so could be body heat?

crawas

Also I have an indoor sensor in one of the bedrooms so it’s averaging the thermostat sensor along with the indoor sensor

ethicalpaul

It’s averaging? I think this is completely new info 😅 Is it a multiple input thermostat? What is the other one reading?

Body heat and other stuff like the oven add heat of course, but if it was affecting things that much, we wouldn’t need boilers 😉

Fred

Did you check your main venting? Also, does the thermostat happen to be mounted on a wall that has a steam riser, to the second floor, behind it ?

crawas

I found one of the main vents. It’s a gorton 1. Is there more than one?

crawas

I don’t think it’s on a wall that has a steam riser. It’s a visionpro Honeywell thermostat that has a wireless indoor sensor as well

Fred

crawas said:

I found one of the main vents. It’s a gorton 1. Is there more than one?

There should be a vent on each of the mains. How many mains do you have? Also, a Gorton 1 is a small vent. Unless your main is 10 ft. long or less, that's not enough venting. Steam will spend a lot of its cycle time pushing air out of the mains and not on heating the house.

Additionally, is that remote sensor in the coldest room upstairs?

crawas

Yes it’s in the coldest room on the 1st floor and I’m thinking to add one to the coldest room on the second floor as well (it’s a 2 family home). I don’t know how many mains I have. I only found the one vent in the back of the house.

crawas

In case you haven’t already noticed, I’m a huge amateur!

ratio

Pics of the NBP are in this thread. Far from the worst install that's been showcased around here.

crawas

I don’t understand

ratio

NBP (near boiler piping) is critical for a modern steam system. Yours looks a lot better than what we typically see. I can't tell if that boiler is supposed to have two risers, but the one it has appears to be full size & rises up what looks like twoish feet, has two separate takeoffs for the steam mains, then drops down to the equalizer in a way that won't trap water. The Hartford Loop is a little long. The pressuretrol looks to be set slightly higher than it should be, & there aren't provisions for cleaning the attaching pipework.

Like others have mentioned, go over the main venting—if the main that serves the upstairs is inadequately vented, the radiators attached to the other main will heat a lot faster.

When the thermostat is calling for heat, does the boiler burner itself cycle on & off; or does it run continuously until the thermostat is satisfied? Any of the radiator vents spit water or hiss at all?

crawas

None of the radiators hiss or spit. When the boiler calls for heat it stays on until the therm is satisfied and I only found one main vent. Should there be more?

neilc

Did you dial the Ptrol down?
I see it set for around 2., and that's too high.
Dial it down to the bottom of the scale, 0.5.
Check under the cover, there's a white dial, it should be set to 1.
You can power the boiler down while under the cover for safety.
The lower steam pressure actually moves faster than higher pressures.

From your boiler pictures it looks like you have 2 mains coming off the boiler header.
Each of those mains should have venting.
Follow each to their end and find that other vent.
Post pictures of what you find there.

crawas

I hope the contractor left the second main vent exposed like he did with the first one. I don’t know of any other locations there would be another vent. I’ll look around. Should I change the gorton 1 vent that I found already to a gorton 2?

Fred

How long is that main (from boiler to the vent) that has the vent you found. That will help us determine what size vent you need there. It is imperative that you find the vent on the other main. If that main doesn't have a vent or if it is failed closed, that will prevent steam from getting to the radiators connected to that main in a reasonable amount of time.

gfrbrookline

I would skip the G2 and go with Big Mouth's Much more band for the buck.

crawas

Fred, how can I find it if it’s been concealed? Should I just installs a new vent on the second main to play it safe?

Also how can i tell if the main vent that I did find is in fact working properly?

How’s long should it take for steam to reach second floor radiators when things are working properly?