Is this short cycling??

skimmer

start up boiler from a period of rest. Header pipes still warm/hot to touch.

Runs 14 minutes until shuts off on pressure

Off for 30 seconds

Restarts and runs for 2 minutes until shuts on pressure

Vaporstat. 1.5 main. Dif 4 oz.

KarlW

Not short cycling per se, but an indication of an oversized boiler if this happens on the coldest days as well. On the coldest days your system shouldn't shut off under pressure unless you have it all TRV'd like my system.

That 14 minutes creates the steam and distributes it, filling the pipes until the system is pressurized. It only takes 30 seconds to lose the 4oz and restart - since it is already at steam temperature, it doesn't take long at all until it is re-pressurized and shuts off again.

I'd turn the differential up to 1psi or even 1.25psi if you don't mind living on the edge (missing a heating cycle) Check your radiators - if they are still steam hot after a reset with the higher differential you are probably where you want to be.

bburd

That sounds like your boiler is sized about 20% larger than needed for the radiation you have. This is very common and basically a fact of life for most steam heating systems. If any of your radiators have been removed or are turned off, that can also cause this to happen.

The other possibility is that your air venting, especially the main venting, is inadequate.

if that were my boiler I would increase the differential to about half the main scale setting. That would at least slow the cycles down.

Jamie Hall

I beg to differ. That 30 seconds is long enough for the blower to slow to a stop (if this is a power burner) and then restart without damage. The boiler never actually goes off a boil (residual heat in the metal) — if it did the pressure would drop to zero — so when it restarts your mains and radiators still have some steam in them and the boiler just starts to make more steam. This means — bottom line — that there is almost no hit on efficiency from that cycle timing.

Leave the pressure settings where they are.

KarlW

@Jamie Hall you make a compelling point, but isn't the boiler still at a steam even at the lower non-zero pressure?

Mark N

@skimmer why is the pressure getting so high so quick? Is it because the vents on the convectors are closing?

skimmer

Well I just raised the diff to 16oz and I will see what happens. I dont think its oversized, years ago I did a EDR measurement with all my rads and one 30 foot 2" main with the help of noel murdough and we came up with a number including the pickup factor of I believe 295 sq feet although i may be off but not over 300.

I have the IN4 rated AT 271 SQ feet

The only thing is my rads are all copper fin, and they dont hold much steam, they got hot quckly, but the cool down just as fast.

I am thinking maybe they are the problem.

ethicalpaul

Check your main venting to make sure it is not the thing that is causing the high-pressure. The basic question is: are your main vents open while the pressure is OK and then only after they close is the pressure getting high? Or is the pressure getting high when the main vents are still open?

If it's the latter you need more main venting.

I can't remember, is this 1 pipe or two pipe? If one pipe, then check all your radiator vents to make sure they are letting steam into the radiators. If they are very small you might consider making them larger. But don't go crazy. I'm thinking like a #6 Gorton or Maid O Mist on most of them.

To me, 14 minutes of burn time on a call for heat before a pressure-limit cutoff is significantly oversized (or something amiss with the venting as described above).

Switching from a broken pressuretrol to a working vaporstat you'd expect to have a shorter burn time, but hopefully it's just pointing out some issue with venting that you can address.

skimmer

the main vent is inaccessible at the moment (rented space ) but I haven’t been made aware that’s it’s hissing or spitting water

1 pipe system.

All the radiators are getting heat.

I have Hoffman #40 on 2 rads on the first floor. The smaller one is the at the end of the main. The larger one is right above the boiler.

I have a baseboard steam convector in my kitchen too. Can’t get to it to easily. No hissing or spitting and gives off heat. All 3 give off heat at the same time

skimmer

@Mark N yes all the vents are closing at the convectors. I get heat out of all of them.

I have a mixture of Hoffman and Gorton vents.

I have one small 3 foot baseboard convector closed off in a floor 2 bathroom due to a stem leak that if difficult to get to

ethicalpaul

the main vent is inaccessible at the moment (rented space ) but I haven’t been made aware that’s it’s hissing or spitting water

The bigger concern, since you are experiencing quick pressure buildup, is that it might be failed closed.

Jamie Hall

https://forum.heatinghelp.com/discussion/comment/1832457#Comment_1832457

Yes — so long as it is above atmospheric. There is a gentle gotcha with some bigger burners: if there is a pre-purge (like Cedric!) the trick is to get the timing right so at the end of the pre-purge the boiler is still fractionally above atmospheric…

skimmer

hmmmm. Ok I will have to check that. Do you think changing the vents on the individual rads will improve things to?

skimmer

latest test. I let it run until all the rads got steam and then.

next cycle it ran for 1:30 before shutting off on pressure

stayed off for 1:23 before restarting

next cycle ran for 1:51 before shutting off on pressure

stayed off for 1:24 before restarting

at this rate the cycling will be excessive.

Im hoping its a main vent issue

Jamie Hall

That doesn't sound like a venting issue. It does sound like a significantly oversized boiler… unless it can be downfired, not much you can do about it.

It's enough too large that the time delay for a restart might be worth looking into.

skimmer

yeah maybe so. I don’t know how, I worked with Noel years ago and he was very helpful. It may be the copper convectors which are hard to get a accurate edr?

it is a small house so anything is possible.

I still have to check the main vent. I believe there is a regular gorton vent on there maybe a C

109A_5

I would say that it is short cycling at least after the initial 14 minutes of run time. I don't think it has anything to do with your main vent, since with 30 feet of steam main that main vent should be closed in under 5 minutes and remain closed for the remainder of that cycle.

If it were me I would redo the EDR survey very carefully, so you truly know what is going on. Or you have radiators that are plugged up and can't radiate well. With that one radiator turned off you would not include that radiator in the present EDR size (for this purpose) since it is not presently being used. Shutting off radiators makes the actual EDR being used smaller, which acts like an oversized boiler, since it is oversized for the present available EDR.

If you were replacing the boiler you would use the total system EDR.

If you want run the system the way it is with the present diminished EDR being used I would add a timer to extent the off time a few minutes, after it trips off on pressure. Personally I don't like the short cycling since most mechanical things (like gas valves and dampers) that cycle have a limited number of cycles, why needlessly use up the cycles. I'd rather see one or two additional normal run time cycles a day then 3 or 4 short cycles with every normal cycle. It is a balance and every system is different.

skimmer

I just reopened the bathroom radiator. So now all 7 radiators are online. I think the problem was that the pressure was going to high and causing the stem to leak.

From what I can remember I don’t think Noel was able to find an exact EDR for my radiators but found something close. Maybe that was an error who knows.

I ran it again after a few hours off. It went 19 1/2 minutes until my first floor radiators gave off heat.

And at 20 1/2 minutes it shut off on pressure.

And basically I have it down pat. A minute and half on and off over and over until the stat is satisfied. This is not good.

I am contemplating going back to a higher pressure to combat the short cycling.

I am interested in a timer. What is it called exactly and where do i wire into?

109A_5

For the moment I would not raise the pressure much, I would have the differential as high as possible that still provides reliable pressuretrol operation. Simply the greater the differential the longer the burners off time is.

I shut my system off for at least two hours tonight (its 19 F degrees outside). The steam main approached the ambient basement temperature. Upon starting it back up, it took 5 minutes for steam to start to heat the riser, it took another 3:30 to get to the far end of my 36 foot main. The radiators just above the end of the main were warming up by the time I got to them. Its been running for 45 minutes now and things are warming up. The pressure never got any higher than 2 inches of Water Column (1.16 Oz).

I have a variety of cast iron radiators 9 total and insinuated pipes in the basement. Looking at the pictures of your convectors the amount of pipe inside seems small compared to radiators, maybe they are more efficient with the amount of fins. They need to dissipate what the boiler produces to keep the pressure down. I would still double check your EDR figures.

With the timer, I like the ICM203F Delay-on-Break Timer with 6 inch Wire Leads, .03-10 Minute Knob Adjust Delay, it is inexpensive and only two wires. Basically it would be connected in series with the pressuretrol or the gas valve. If you have a Damper and you want the damper to close with the timer it may require an additional load resistor to meet the minimum current requirement of the timer. Basically when the pressurertrol shuts off the burner (Cut Out on pressure), the radiators are hot, so the timer locks out the burner for a short delay disabling all or part of the the short cycling phase.

https://cdn.lsicloud.net/gothermals/Resources/ICM203Bdata.pdf

skimmer

maybe I will play around with the heat cycle rate and set it to fast to allow tighter temp control and shorter on/off cycles.

It seems on the slow settings i am allowing the system to run longer. While desirable for steam it’s allowing it to run longer when it shows it has hit the room temperature

109A_5

Many ways to interrupt a call for steam and insert a brief delay. Once interrupted the radiators continue to condense and the pressure drops. As I think I stated in one of your other threads I don't like excessive system cycles and excessive pressure and pressure cycles, I think it is mostly pointless to the task of heating the building and just adds to the wear and tear of the equipment.

It's like drivers that accelerate hard and brake hard, their gas mileage sucks and they need brake jobs and tires a lot so more $$$ spent just to get from point A to B.

I feel lucky with my system, as I received it, pressure has never been an issue, and years ago I did not understand why it did not build pressure, I know now. I do play with my system a bit and I do have the timer mentioned above, so I know it basically works as intended.

AdmiralYoda

https://forum.heatinghelp.com/discussion/comment/1832460#Comment_1832460

You'll want to re-do your EDR survey but no need to include a pickup factor. The EDR is what it is, the pickup factor is already built in to the boiler's rating to overcome losses due to uninsulated pipes in the basement and other inherent losses.

I think you need more venting. You mentioned it looks like a Gorton C, install a Gorton #2 or a Barnes and Jones Big Mouth. You can't really have too much main venting.

I think your boiler is oversized…but not horribly and you need a bit more main venting and possible some more radiator venting. If you have long risers you may even want to add a vent at the end of the risers prior to the radiator too.

dabrakeman

Only 1 minute between when your radiators start(?) giving off heat and when the system shuts off on pressure??? Assuming the radiators are full all the way across when the system shuts off on pressure you might consider venting your radiators slower than you currently are. You mentioned Hoffman 40 vents and some Gortons. Hoffman 40 is already reasonably slow but maybe those small fin radiators have little internal air volume and combined with oversized boiler just fill remarkably fast. You could try MoM or Gorton #4's or Ventrite adjustable #1 vents for slowest control. This might increase cycle time with slower radiator venting. This is a balancing act since if the boiler is oversized too much slower venting could shut off the boiler before the radiators fill but if you slow the radiators and the shutoff still only occurs after the radiators fill then the slower radiator venting is good.

I'd put a Gorton #1 on the main.

Jamie Hall

Did I actually read nineteen and a half minutes from a cold start for the radiators to start giving off heat — and twenty and a half before the system shut off on pressure?

Really?

The timings which @109A_5 gave are much more reasonable — and quite similar to what others have observed, given variations in the systems.

Something is really amiss there.

I doubt very much that the EDR figures are off enough to cause much trouble. Noel was pretty good with that kind of thing.

Would you mind checking your timings again? From burner light off: time to steam at the header, time to steam at the far end of the longest main, time to steam at the inlet to the fastest radiator, time to steam at the inlet to the slowest, time to fastest radiator vent closed, time to slowest vent closed, time to shutoff on pressure.

I know it's a lot, but it will be helpful — since we can't physically be there.

skimmer

yes that is correct. I was in my living room timing the entire thing last night. I can hear the boiler start up and hear the vent click shut.

yes this is after the vaporstat install. 1.5 cut off and 16 oz cut in. Before that it was running on a higher pressure.

Basically once everything is hot it’s 1-2 minutes off and 1-2 minutes off all on pressure. I can’t see the IN4 being so oversized. There was never a main vent and one was drilled in and the Gorton 1 was placed but it was then replaced with the smaller Gorton.

The end of the main is in a rented space so I have to coordinate access there. There is a vent but it hasn’t been check in years.

All I can say is the Hoffmanns are on floor 1 and the gortons are on floor 2. All rads heat. All the way the across. The furthest radiator is the master bedroom there might be a delay with that one I will have to time it. That one uses a Gordon 6

skimmer

@dabrakeman yes I imagine these don’t have much air volume. They look like copper pipes with fins around them. How much air can they hold??

If you zoom in to this picture it looks like 3 half inch copper pipes surrounded by fins. Doesn’t hold much steam. Maybe that’s why I build pressure so fast? All my rads are like this except for 2 which were converted to baseboard but they are short metal pipes with fins surrounded them too.

109A_5

To me its not about how much air or steam they can hold, the steam should push the air out (as needed) and bigger will dissipate more heat. Its about dissipation of the heat into the surrounding environment, which will condense the steam. Once the vent closes the radiator or convector should be condensing at about its maximum rate. If your radiators or convectors can't keep up and condense what the boiler is producing the pressure will build. That's why when the Square foot rating of the boiler closely matches the EDR the steam power applied to the system is dissipated by the system into the environment as heat, and its all in balance. An undersized boiler can never totally fill the system, an oversized boiler can overfill the system so the result is pressure.

Could your tenant have blocked off or shut off some of the radiators ?

skimmer

my tenant doesn’t have steam radiators. They are on a hot water loop. The steam main runs thru their place and the main vent is located there.

So I am guessing I am oversized. Maybe I can slow the rate via venting on the first floor with different slower vents and have quicker vents on floor 2.

I also need to get to the main vent although I’m not convinced there is a problem. My system is not shutting off on pressure before I get heat.

109A_5

I would not slow anything down, that probably would build the pressure faster. If the pressure builds once all or most of the vents close and all the the radiators or convectors are hot its just oversized. Is the hot water loop on that boiler also ?

skimmer

yes the hot water loop is on the same boiler.

109A_5

Well I would imagine if the boiler is sized large enough to keep the whole structure amply warm it is probably oversized for the steam portion of the heat load.

skimmer

I am wondering. If when the hot water loop is calling for heat and circulating and robbing BTUs does that “help” with the steam side?

Meaning does slow down the steam production or the amount of steam?

I will have to test that out once I do the testing asked by @Jamie Hall for the steam side.

But I’m starting to wonder even I had 5 main vents would it make a difference?

109A_5

I would think hot water loop would have an effect depending on when its call happens in relation to the steam call.

The thing is with the vents by the time your system starts to build significant pressure the main vents (and probably most of the rest) are closed for some time, since the radiators or convectors are approaching full and can't dissipate what the boiler is supplying. Once closed what benefit would 5 or even 10 be ? The purpose of the main vent is to fill the main fast and first then close so the radiators or convectors throughout the system can fill more equally or evenly, as needed, they are not really for purpose of pressure mitigation, they are for purging the air out of the system so the steam can fill the radiators or convectors without loosing steam to minimize make-up water.

When the radiation matches the supply and piped correctly the system won't build pressure.

pedmec

How many copper convectors do you have and how long are they. Its easy to calculate.

Just want to correct you on something. Because you keeping referring to the EDR of 271 that is listed from Burnham. That is not the actual EDR. The actual EDR is 362. You need to dissipate the extra EDR or your over-sized. The pick up factor is kind of an guestimate of what you will lose traveling with 271 left for your radiators.

skimmer

pedmec
I am not sure I follow you. This is telling me 271 sq foot of steam is being produced.

I have 5 copper convectors.

24”

36”

36”

32”

20”

The ones on the same side of the house as the boiler (front of home) heat up about a minute or two before the rear ones.

pedmec

You see that 87 MBH? that equates to 362 sq'. this is what's available to the heating system after the flue gas losses from 105 MBH.

105,000 x 82% (AFUE) = 87,000 (rounded)

87,000 / 240 = 362.5 sq'

271 x 1.33 (pick up factor) =360'

everything Burnham does is rounded

skimmer

wow! just about everything I read (or thought I read) told me to go by the manufacturers steam output rating (sq ft) add up your rads and add the 1.33 to that and get your steam sq foot needs.

Is this only a burnham thing or do all manufacturers do this?

now I am really confused

skimmer

So I just went on the burham site and read their guide on sizing a steam boiler.. Now I have more insight..

I am not sure where the disconnect is. I dont have the email anymore where it was figured out what the EDR of all the rads are. I imagine it was small. Maybe in the 200's

I guess I should have went with the IN3

pedmec

Everybody does it but its not an exact science. the 1.33 is a fudge factor but if you don't have much piping attached you most likely don't need to oversize it by 1.33. Which is what the manufacturers are doing for you.

i think the copper convectors are working against you too, there is no thermal mass in the copper so they immediately cool off. steam condenses rapidly in them as you're well aware of. Copper convectors should really be used on hot water although they have been used successfully on steam.

Just think of the positive. You can easily convert the convectors to hot water if needed. With the in4 boiler you have to keep that in mind. Not the most reliable heat exchanger.

bburd

The 1.33 pickup factor is an industry standard built into the boiler steam net square-foot ratings. Some of the regulars here have argued for years that it's too high and responsible for oversizing many systems. It's meant to cover the vast majority and keep installing contractors out of trouble; most people won't even notice an oversized boiler, but they certainly will if it's undersized

skimmer

I noticed it now. When I changed over to a vaporstat. Before that I noticed my gauge out of whack. My big dial 0 to 3 gauge stopped working last year so I didnt notice for a while.. I replaced with a 0 to 30

Also my pressuretrol seemed to be out of whack too. Was letting the pressure build to 7 recently after I was adjusting the settings.

So the question is:

Do i let it short cycle or do I raise the pressure to cut back on the cycles?