Steamed up over Steam Boiler Short Cycling

BobC

T-stat and skim

I don't think the baseboard is going to take enough energy from the boiler to materially affect the short cycling, the boiler is simply too large.



The radiator covers were there with the old boiler and everything seemed fine so lets look at the thermostat. You changed that anticipator for the new boiler and maybe that has something to do with some of the problems you have. If you lower that does the heat improve, not counting the short cycling?



I would get a skim port added asap, draining the boiler will not solve the oil in the boiler water and THAT is causing you a lot of problems.



My boiler is oversized like yours and it short cycles but it maintains temperature within one degree no matter where i set the thermostat (Honeywell digital with a steam setting - about $50).



Bob

Dave in QCA

those radiators are not hot

You should be picking up a surface temperature of around 200F + or - a little bit on the fully heated surfaces of a radiator saturated with steam. If you have an accurate reading that is considerably cooler, and appears that you do, (we don't know how you were taking the temperature) then there appears to be something wrong.  I'm sorry if you already said, but what vents are you using?



As far as the hot water loop, yes, that has to be factored in the sizing of the boiler unless it is something that only occasionally runs.  When it is running, you have about 112 EDR or 26,880 BTU on the baseboard if the boiler is at steaming temperature. 



If the HW zone is running while the boiler is steaming, it will still steam, but it will not make as much steam.  When the water loop is circulating there is water coming back that has been slightly cooled and it will reduce the amount of steam.  You can't take heat out of the boiler without it affecting the steaming capacity, the water loop does not make heat, it takes it from the boiler.



Regarding your thermostat, I know that my own hot water system will continue to run even after the thermostat has reached the set point, but then it stops.  The question on your system is whether the thermostat is shutting the boiler off and then causing several short cycles for a the next hour, or whether it is shutting off on pressure.  If it is on pressure, that happens, especially when a boiler is over-sized.  If you run the water loop the amount of short cycling off of pressure will be reduced.  If you are short cycling because of the thermostat, did you get a new one?  What kind is it?  Is there an anticipator?  What is it set at?

STEAM DOCTOR

near boiler piping

Hard to tell from pics but you seem to have the pitch in the wrong direction on the near boiler piping. The first and second horizontal pipes above the header(near the ceiling) seem to be pitched in a way that would leave a buildup of water in that connecting elbow. This will reduce the size of the pipe and can lead to a buildup in pressure with will shut down the boiler. Obviously this will also result in reduction of heat getting to the radiators.Look on left of boiler toward the back. There should be a 1 1/4" nipple and cap. This is the skim port

vaporvac

Retrofit Radiator Covers

RedFred,

I'm a homeowner like yourself, so I'll leave it to the experts and experienced folks on this site to guide you with the boiler issue. However, I can comment on the radiator covers..  I retrofitted all my covers and achieved an amazing increase in the heat output of those radiators. Yours are really attractive and could easily be changed by studying the pdf posted above. I did various fixes depending on the radiator. The main thing was to have ample space on the bottom and solid sides and back. The front should be partially solid. I made the tops  removoable or hinged them and then lined the back inside with reflective foam. These changes create a chimney effect and help draw the air up and over the radiator and out into the room.  It looks like your bottom gap is pretty good so it should pull up the air. If not you can add just a bit of wood on the bottom.This worked even better than having no covers so I plan on doing this for the remaining ones. The good thing is I can close them in the Summer.

I doubt this is the only problem with your system, but even after sorting those out, this really increases comfort and saves a few pennies.



Reflective surfaces behind the rads really do help.Somewhere there's a post where someone took a side-by-side thermographic image. Amazing difference and it helps with enclosures or oTen radiators.the sheet metal should work well, but the double-sided foam works a bit better by reflecting heat into the room and cold back through the wall. Good luck.

vaporvac

Additional info.

Gerry posted this to another question from his site. It's slightly different from the other pdf and explains how the different enclosures work. Ignore what i said about closed sides. A few tweeks should be all your need. https://www.ideals.illinois.edu/handle/2142/4165

Red_Fred

Skimmed

Skimmed boiler for a few hours for last 3 days with heating cycles in the evening.  Water looks cleaner.  Also added the Groton #2 valve to the main.  Boiler seems to be running for longer periods of time, about two 20+ minute runs. House warms up.  But still short cycling.  Example: If old mercury thermostat set to 65, and house reaches 65, but boiler keeps running.  It runs for a few minutes and shuts off, off for a minute, then on again. It never seems to stop. I get tired of it after 15+ minutes and just turn down the thermostat to get it to stop.  I tried adjusting the delay on thermostat from 1.2 to about the middle  .7 but it does not seem to change anything.

Thermostat: Next I will install a new thermostat, new thermostat sets cycles per hour. So if set at two 30min cycles for steam an hour I am assuming it will know it has reached the right temp and not ask the boiler to go on any more until the temp goes below set temp.   I don’t care if it drops 3 or 4 deg before it goes on again.  Not sure if the new digital will keep calling the boiler for steam to keep it at set temp.

Dave in QCA

1 cycle per hour

The recommendation for steam systems with cast iron radiators is 1 cycle per hour.    You might feel a small temperature fluctuation, but not much, perhaps none at all.

Pilot1226

Feel your pain

I feel your pain. I switched from a mercury-based slider Honeywell to a new "programmable" thermostat.



I mistakenly set the "cycles per hour" way too high when I installed it and resulted in tripping the low-water-cutoff every time it would turn on (because the water was still in steam phase condensing back to liquid throughout the system).



I can get around this by adding slightly more water than suggested to the boiler itself, but obviously this results in more energy required to change the water to steam and thereby hurts efficiency / raises my natural gas bill.



I'd suggest a double check of that cycles setting. I fixed the problem with a mere push of a button.



Now, I'm trying to determine if it's better to leave it on a constant mode (IE, set the thermostat to 70 and leave it alone forever) or actually have it use a program (7AM heat to 70, 8AM drop to 60 since nobody's home, 4PM heat back to 70, etc.)



I'm wondering if the short cycle you're mentioning could be caused by the low-water cutoff? I'm considering putting in an auto-feed this season for our boiler, but my concern is obviously failure of the auto-feed resulting in water gushing out of my radiators (happened at my sister in law's)

Jamie Hall

Setbacks

For Pilot 1226: Steam systems really truly do NOT like setbacks.  You might get away with 3 degrees daily setback.  10 degrees daily setback, as you were saying you might experiment with, will be completely counterproductive.  Might work for scorched air -- though even there I'd say it was excessive -- but not with steam.  No way. 



Did the OP ever get the short cycling fixed?

gcp13

Short cycling

How is the basement loop wired?

Does it have an aquastat that maintains 180

Is it wired correctly since you replaced boiler?

You need to disconnect both tstats and do a continuity(beep) test while moving

Above & below room temp if they are bad get rid of them

Boiler shouldn't run if tstat isn't calling for heat

You also need to check the test light on Hydrolevel

L.w.c.o. If it comes on when boiler shuts off.

Read the manual for that unit it explains the intermittent test

PMJ

Setback/Stepping

Sorry Jaime but I have run a night setback for years on a 1926 Mouat system - 460,000 input brick home with no insulation and wouldn't do it any other way. The dropping temperature around 11PM encourages heading for bed and sleeping is better a little cooler anyway. In the AM I step the temperature back up slowly over 6 hours. Mornings are much more pleasant with guaranteed warm radiators. With this gentle approach I am convinced I end up ahead on cost - but comfort is the main attraction anyway.

ChrisJ

setbacks

I also can do a setback on my system. In fact on a 9 degree recovery it only cycled once due to pressure @ 1.5PSI. The story may be different if it is 0F outside but I could probably still do a 3-5F recovery with little trouble.



However I think overall Jamie's comment is correct. Perhaps it should have been worded "Most steam systems do not like setbacks".

PMJ

Maybe so

I sure don't wish to ruffle any feathers - I'm just don't understand the blanket rejection of setbacks. I don't think the math supports it.



I would never see anything like 1.5psi. And I introduce extra cycling on purpose - maxed out at 3 per hour. The Mouat is an ultra low pressure system achieved with extra large pipes. I suppose that is one reason it fell out of favor - the extra up front cost. But it sure is nice. I can have burning hot radiators throughout the house and not see 2 ounces in the main - and there is no main vent at all, only one on the return.

ChrisJ

single pipe

Mine is just a cheesy single pipe system. But it does the job.



After a recovery mine doesn't run for several hours. Don't you consider cycling the burner with the thermostat almost as bad as with pressure? I would think you're still loosing efficiency vs one long run time.

PMJ

Efficiency

I cycle it with a PLC not the tstat not that it makes a difference. Check my other posts for more details.

I cycle on purpose to even out the heat. Rads are gentle warm almost all the time vs hot and cold cycling. I think efficiency loss is mostly related to time to steam after the call for heat. Systems that have build pressure to move steam each cycle have longer times to steam at the rads from call. My system which falls into natural vacuum between cycles is literally less than a minute after call to steam chasing vacuum down the mains if the burner has been off less than an hour. It is generally accepted here that pressure is the enemy and I agree completely. Starting each cycle with the main at negative pressure and never needing more than 1 or 2 ounces to fill all the rads is a major advantage. 

Dave in QCA

It Depends....

As with everything relating to steam.... it depends.



But, most steam systems when coming out of a deep set back, perhaps even a mild setback, will tend to over shoot. So, while a constant setting of 70, with a well tuned system and a well adjusted thermostat, the actual space temperature may not fluctuate more than a 1/2 degree F. But, if you run a setback down to 65 or lower, many systems will overshoot when warming up, perhaps as much as 4-5 degrees F. So, on one hand, you could have a comfortable setting of a constant 70, or your could go down to 65, and up to 75. It is the overheating that robs most if not all of the savings that might be had from doing a set back. If you can control your system so that does not occur, then, you would be ahead to do a setback. And as you said, you like to sleep in a cool room and comfort after all is what this is all about.





Another thing worth mentioning about setback and subsequent warm ups is the hard work that the system does in coming out of the setback. Many one-pipe systems in constant temperature firing will not fire long enough for steam to reach the radiator vents. This increases their life because they aren't doing any work. The same goes for traps on a two-pipe system. Of course it could be said that coming out of a deep setback would be a good practice to observe that all parts are working the way they should, because this will certainly put things to the test.

PMJ

All Very true

and it is the overshooting that I identified years ago as the enemy. Rads get hot but there is a significant time lag for that heat to get to the tstat. With the conventional set up by the time the stat is satisfied, most of the room is over temp if even a degree or two. If you cycle some on purpose you give that heat time to mix in the room and overshooting is minimized. On recovery from setback you just don't do it too fast - I spread out the recovery. Live radiant heat from radiators in the morning seems nice even though the actual room temp is a few degrees below the regular set point.

About working the system, that is another nice thing about the Mouat - traps have no moving parts - only a water leg. But then, this is another advantage to cycling to prevent rads from getting too hot on systems with conventional traps. Rads only need to heat all the way across on max capacity days anyway so they really never need to close. If you run long enough to close them on an average demand day you work them for no reason.

Jamie Hall

I quite agree

with the warm radiators when you get up!  I like them just as much, I dare say, as you do!  And I like to sleep cool, too.  But I use only a 3 degree initial recovery (59 to 62) set to get steam to my radiator when I have to get out of bed -- and another degree set to get steam to the kitchen radiators when I've finished chores and am sitting down to breakfast!

ChrisJ

Holy smokes!

59-62?



I was doing 67-70F and my wife complained the house was too cold at nite.

Pilot1226

Thanks!

Thanks for the great responses about setbacks. I just posted another thread about the issue on the wall to avoid hijacking this person's thread...



So it's the deep recovery that seems to be the big no-no for the steam heat?



Like was posted above, my family prefers a warmer setting, we have little kids, so our target around bedtime should be around 69-70, primarily because my son refuses to use a blanket!



Armed with this new information, I'm considering:



7 AM - Thermostat set to 60 (will still be around 69 from previous day's setting)

2 PM - Thermostat set to 63

5 PM - Thermostat set to 66

8 PM - Thermostat set to 69



Thoughts?



I will try and use this for the next week, then try holding a constant temperature the following week, and compare the gas usage.



We can deal with a little overshot here and there.



Also, as a sidebar to the picture above, those radiator covers are beautiful! I have dark (walnut colored) wood trim around all of my windows, baseboards, doors, etc in the house. We have metal radiator covers painted the same color as the walls.



How did you make these? Table saw? Did you put a polyurethane on it when finished? I can't wait to make a few of these - I definitely have to make at least one for the spare bedroom upstairs when it gets occupied this winter with our family's newest arrival.

ChrisJ

Overshooting

Not sure on your system but even raising my house 1 degree causes an overshoot.

Raising it 3 degrees causes a huge overshoot.

Red_Fred

Winter #2

Update:  Last winter I got sick of dealing with the boiler and then the winter ended.   I skimmed the boiler from the top about 4 times last winter when new, drained it over the summer and refilled it, added more insulation around the steam pipes. I added a the big #2 Gorton valve to the end of the steam line, All new valves on the radiators last winter.



I also removed the old thermostat with the mercury switch and replaced with

a brand new electronic round manual Honeywell controller set at Steam.



This winter it still short cycles. It runs for a while for the first run. But eventually starts to run for 5 minutes, shuts off, motor closes flu, motor opens flu and starts up again just as fast as you have read this. Several times the flames barely get ignited and the unit is shutting off again. It will do this about 10 times or more.



I get really annoyed since I am in the finished basement listening to this. So I shut the boiler off. Then about 10 min later I turn the boiler on. Guess what. The boiler stays off. Yet the thermostat upstairs was never touched.



It seems to run better set at 60 or 63, but if I set at 70 I just get short cycling for a long time.



SO. The Honeywell thermostat is not doing 2 cycle or 1 cycle an hour.

I never see the Stat thermometer move. Even when Thermometer next to it says 70. But the thermostat says at 63. It may go to 59 at times but rare above 63. So I used a hair dryer to see if it moves. Eventually it does.



Then I pulled it off the wall and used a toggle switch. The boiler ran a long time. 20 maybe 30 minutes. Shut off for a bit then ran another 30 minutes. The house got nice and warm.  A lot of times while home I just use the toggle switch. I get longer runs from the boiler with just the toggle switch.

6

So it would seem the Honeywell thermostat has no idea how to control the steam boiler. It does not appear to be the pressuretrol turning the boiler on and off every 5 minutes. Or maybe the temperature reading component is broken.

Steamhead

Those round non-mercury stats

have been known to be a bit flaky. Try a 6000 or 8000 series unit, we have had no problems with them. Both let you set the CPH as low as 1, though we generally use 2 or 3 on most of our steam jobs.

mcsteamy

Covers ...

Covers don't matter, however they will have the net effect of down-sizing the radiators, making the system even more oversized.  Still, the radiators themselves are grossly oversized for the house with the insulation.  We have much uglier things done to the rads in our office building, and they still work just fine.... I wouldn't think the issues have much to do with the covers.  And wow are they nice looking!

mcsteamy

Nice!

Looks like you've made some progress here and winnowed the issue down to thermostat problems.  If you can't get the stats locally that Steamhead recommends (and following his recommendations is usually a short path to success), you might try buying a handful of them at the local big box, and swapping them in until you find one that works right for you, then bring the rest back....

Dave0176

Piping size

Hey Fred, I'm no expert either, but the near boiler piping seems inadequate. If that boiler has provisions for two steam risers they should be used, and also a three inch header, and a drop header would be best, it would be the smallest I'd go, yours looks like two inch. With your piping I'd say your getting wet steam which is why it isn't heating well. And cycling too much. It is way oversize but better piping would help dealing with it a lot better.