How to delay boiler from firing again right away after max op pressure is reached?

MilanD · December 2016

I am starting a new question as searching for it here on the board did not yield answers.

It's along the lines of best tstats for steam heating, but with a twist, I suppose.

We have a one pipe system that I would call well-balanced and that vents well. LGB 7 with 3 zones, 29 rads in total (EDR was calculated at the time of install 7 years ago, and LGB 7 replaced the older LGB11). There is a new 50 gal insulated condensate return tank, FT traps and Warren Webster 78 traps at end of each main, Hoffman 17cs at the beginning of each main to drain back any left over water back to condensate tank. All traps were serviced and replaced this fall and are working beautifully. Main vents, rad vents, all checked and replaced as needed (new Hoffman 75 on mains replaced old Hoffman 75 - next time I'll put on Big Mouths). All rads get hot before pressure rises and vaprostat cuts off the burners. Op. pressure is set at 8 oz, with cut in at 4 oz. It works flawlessly, 95 % of the time. Set-back is 3 degrees, and most of the time, it does not cycle on pressure before satisfying tstat. I am proud to have done most of this balancing/servicing work myself, with learning a great deal from @Dan Holohan 's books

This is in a large 10,000 sqft brick building with 2 38x61 ft auditoriums (15 and 18+ ft ceilings, one on top floor vaulted to probably 30 ft), a lot of large old wood windows and no insulation other than attic in half of the building that's not auditorium. The rest can't be insulated without making this a multi hundreds of thousands of dollars project. Other side of the roof is above the mentioned vaulted ceilings in one auditorium. So, building envelope it's as good as it's going to get without any major renovation.

2 scenarios, one of which happened this past weekend, and falls in that 5% scenario.

Scenario 1: a particularly cold day when the heat loss is greater (a few days a year really) and to keep up, boiler has no other option but to cycle on pressure.

Scenario 2: days as what happened this weekend - not so cold day BUT a shut off rad in the room with tstat. Tstat was set to 71, but the room could not get above 69 (with the rad closed).

These 2 scenarios create longer cycles on pressure due to fact that the heat loss exceeds heat input, or that tstat is not satisfied. Nothing one can do about scenario 1 but add more rads/bigger boiler, or insulate. On 2nd scenario, this of course happens when no one is in the tstat room to realize what's happening.

This said, in both scenarios, with steam and latent heat, delaying boiler firing by 5-10 minutes after the initial rise in pressure and burner shut-off would not make big difference in room temperatures except for saving on fuel by not cycling on pressure. System is balanced and all rads are hot. However, in scenario 2, the building heating system was on all day, with tstat calling and not being satisfied, and the rest of the building, figuratively speaking, burning up.

So - my question is this: is there a way to delay boiler from firing again for 5-10 minutes after the initial rise in pressure to the set limit, and it shutting off via vaporstat/pressuretorl (some kind of time-out switch)? Can this be done with any particular tstat?

If not t-stat, how can this be achieved?

I am aware Tekmar 279 has some abilities to do something like this, but I am not a pro, and my knowledge on Tekmar 279 is only tangential - by reading about it. Is Tekmar 279 the only thing that can achieve this: delay boiler from firing after the pressure rises and pressuretrol/vaporstat turn off the burners? Can this be done any other way and how?

Fred · December 2016

@MilanD , from your description of the system, it sounds like a Two pipe system, not one pipe???

MilanD · December 2016

@Fred

All zones are a big pitched loop. Rads are connected with 1 pipe, condensate flows back to the same pipe and flows with the steam back to what other systems would call 'wet return'. We don't have a wet return. We have FT and WW78 traps, after which pipes drop down and take the condensate into the 50 gal condensate receiver tank. It is piped with a motor, then check valve into the equalizer, 2 inch below water line. So, I think that's 1 pipe, no?

Fred · December 2016

MilanD said:
@Fred

All zones are a big pitched loop. Rads are connected with 1 pipe, condensate flows back to the same pipe and flows with the steam back to what other systems would call 'wet return'. We don't have a wet return. We have FT and WW78 traps, after which pipes drop down and take the condensate into the 50 gal condensate receiver tank. It is piped with a motor, then check valve into the equalizer, 2 inch below water line. So, I think that's 1 pipe, no?

I don't know? With all the traps you mention, I don't know of one pipe systems using them. Also, what do you mean by three zones? Do you heat specific areas at different times? If so, then the boiler is over-sized for that and only sized correctly if all three zones are calling for heat, at the same time. That would explain the short cycling. Have you posted any pictures on any of your other posts? I'd like to see this system.

MilanD · December 2016

Here are pics:

This check valve was moved down to being right next to the motor. In this location it would knock before closing, I'm assuming as the boiler is boiling steam and water would back into that leg and not allow the check valve to seat right away. On the bottom location, by the motor, it works as it should, some hydrostatic pressure and being away from boiling water, it now works silently.

Installed drip-legs and blow-down valves after servicing the 17c traps at the beginning of the mains. Any excess water that remained in the main riser would go down it, and to the condensate tank.

This is the end of 2 loops, just after the main vent and before pipes take the condensate from here to the condensate tank.

MilanD · December 2016

Everything is heated at the same time. 3 mains coming out of the header. Actually 4, but attic rads are shut off as we have a separate furnace up there. Incidentally, there are zone valves, but we don't use them - well we do use one - and when that zone is on, it does get to pressure quicker, but not enough to where it cycles on pressure before temp is satisfied on 3 degree set back. 95% of the time, as I said, works flawlessly.

DavidK_2 · December 2016

Put a label in t-stat room valve not to turn off radiator???

MilanD · December 2016

One more of FT and Warren Webster 78 on the 3rd loop.

DavidK_2 · December 2016

Other method is to reduce turn down turn on pressure. You need an expert. I'm not one

MilanD · December 2016

@DavidK -- easier said than done... I do have a sign that if anyone touches tstat I'll be hunting them down.

Pressure is already at 8oz. Any less, rads farthest from boiler don't get hot. 8 oz is pretty good I think.

SWEI · December 2016

Is this auditorium intermittently occupied?

MilanD · December 2016

Oh, and all - disregard the dirt on walls - traps were originals and never serviced before I did it this fall. There was so much black gunk on that low loop - it took 10 minutes of hosing it down from the main vent some 20 ft up stream. A lot of crud came out. Didn't feel like washing the walls...

Fred · December 2016

That is not your typical one pipe system. I can't even begin to understand what is going on there but I'm sure others will.

MilanD · December 2016

@SWEI Yes, upstairs one is used 3 times a week for a few hours each time. That's the one I shut off when not in use. It doesn't affect the rest of the system. The pressure does build a bit quicker, but after about 2 cycles, all rads a hot again. I'm planning on adding one more big mouth at the very last rad. It's a 1 1/4 riser to the rad and has plenty of room to add a tee and a 3/4 nipple to attach it. I feel this will allow for better venting on that last rad once the auditorium 'zone' is closed off.

As I said, after cleaning and servicing, replacing main vents and all that work, it's working flawlessly.

Abracadabra · December 2016

All radiators have a single pipe?

MilanD · December 2016

@Fred

Yes, I have not seen anyone talk about this set-up on the wall. @Dan Holohan does have it on one of his books - I think I read about it there.

Simple really, instead of having a wet return, you pipe in FT traps (and Warren Webster - which is just a larger version of Hoffman 17c). This creates the stop for steam. Below these traps, everything is pitched into the condensate receiver tank. It has a motor connected to a float switch on the Boiler. When steam is made and water level drops, pump engages and replenishes water (which is condensate temp at about 200 or so). I have, since the pictures above were taken, insulated the receiver tank with R13 bats (3-4 inces) and that water will stay hot for a long long time.

MilanD · December 2016

Abracadabra said:
All radiators have a single pipe?

Yes. One pipe steam people...

Fred · December 2016

Traps are a lot more expense and maintenance than dry and/or wet returns. I'm just not sure what advantage they offer on a one pipe system.

MilanD · December 2016

MilanD · December 2016

@Fred

I gather it's because the system is so large (790,000 btu boiler - in fact, old boiler was 1,3 million BTU imput), There is no room for pipes to hold all that condensate. All return pipes are 1.5 inch...

When system is cold, there is probably 35-40 gallons of water in the condensate tank.

MilanD · December 2016

This was built in 1922 as a masonic temple. I have no doubts resources were not an issue, nor was it lacking in expertise when it was built. As I said, the system is working flawlessly after service and repair of traps. It used to take 1.5-2 psi to push all the steam out, and we were losing steam like crazy. No longer the case.

MilanD · December 2016

Back to question at hand: can the 5-10 min delay of firing of burners be achieved, after the first rise of pressure and them shutting off against vaporstat/pressuretrol, and how?

MilanD · December 2016

This was from my similar question from on the tstat thread: good answer and some food for thought:

Jamie Hall said:
It sounds to me that you may be looking for a solution to a problem which doesn't exist.. however, a simple way to approach doing what I think I hear you wanting to do would be to add a relay to the pressurestat/vapourstat which would allow for a time delay on reclose. That is, the pressurestat/vapourstat would open on pressure in the normal, simple fashion. It would then reclose rather quickly, as the steam collapsed. However, instead of directly restarting the burner you have a time delay relay in the circuit which would prevent the burner from firing for an additional five to ten minutes.

Mind you, I don't think this would accomplish much. In that time the system would get back to atmospheric and the boiler would cool below a simmer, so you would spend additional time and fuel reheating the boiler and getting the air back out of the system. But... whatever.

And my answer - for anyone following this:

MilanD said:
@Jamie Hall

Great answer! This is exactly what I was wondering if can be done. So there is a delay switch that can be added to vaporstat to delay it on reclose. This is what I'll be doing.

We now have a question if fuel burned when cycling on pressure is less vs. fuel burned after 5-10 min delay in order to get the water to boil again, create steam and move air out. Hmm... if venting is as good as it can be, my assumption is that this would quickly create steam and get it to rads.

I didn't consider this angle, as you call it - problem that doesn't exist. I've approached it from other forum questions where oversized systems cycle on pressure until all air is expelled (not enough venting capacity for the amount of steam created), and all rads hot. This creates excess fuel consumption. I'm wondering if the well-balanced system, properly sized and venting as it should, could also have this happen under certain circumstances, as it did to me last weekend.

On such system, there is, sometimes, a delay between the time radiator is hot and the room is warm and the boiler reaches its max op pressure (esp. after set-back on especially cold days, or if tstat is not satisfied because someone turned off the rad in the room where it's located...) I am talking 5% of the time when this happens and I'd like to make sure we don't waste fuel.

So, what is better? On a balanced system that works as it should and gets hot on the initial firing, all rads hot before pressure rises, is it better to then cycle on pressure until tstat is satisfied (on those cold days), or is it better to delay firing and allow rads to dissipate some heat into the space before getting new steam to them?

I am assuming that it would use less fuel to delay firing the boiler by 5-10 min and allow latent heat to dissipate, vs. cycle on pressure until tstat is satisfied. I would think that with only a 5 min delay, well insulated and still hot pipes, good venting and insulated condensate tank (I have one of those systems no one here seems to have seen, 1 pipe system with FT and Warren Webster 78 traps, and a condensate return tank), this would create savings in fuel consumption. Esp. as my now inulated condensate tank will have no problem at keeping the water in it at about 200 degrees for 5 - 10 minutes, nor would boiler loose too much heat waiting 5 minutes.

So, question is - will it be more fuel to bring back steam from 5 min delay to the point of producing the steam again (say 7-8 min total), or will it be more fuel if the system is cycling on pressure for 7-8 minutes)...

I am talking about my particular system that's all hot and at capacity at 8 oz of pressure, and most of the times, does not cycle on pressure at the 3 degree setback.

Here's a link to the thread I just started, explaining my particular situation.

http://forum.heatinghelp.com/discussion/160248/how-to-delay-boiler-from-firing-again-right-away-after-max-op-pressure-is-reached

SWEI · December 2016

Can you vent enough to reduce the pressure rise?

MilanD · December 2016

@SWEI

Yes. Venting is great! Pressure only rises when 2 conditions happen: when all rads are hot and there is too large of a set-back, at which point it takes time for the tstat to get satisfied and it will cycle on pressure. This also happens on a particularly cold day, or if tstat room rad gets shut down (as it was this weekend). So yes, venting is adequate. I made sure of it.

Even when that big auditorium is zoned off, other venting keeps up for the most part - only with a larger temp swing it takes a few cycles on pressure to get the temp rising. All rads continue to be hot after the 2nd or 3rd cycle. Because of this, I am thinking of replacing the 3rd loop/main vent that is Hoffman 75 with a Big Mouth (it's the one pictured above). It is on that a narrower loop and it also has a funky branch with 3 rads on the end of it and that's the one that vents poorest - those 3 last rads - when the one zone is closed. Even as is, they vent ok, but I know they can be better, and as there is room and it'll be quite easy to do, I'll add another Big Mouth just before that last rad. It's on a 1.25 inch rad riser.

And to clarify pipe dimensions on the 3 zones/loops. Earlier, somewhere in other discussions, I called the loops 2.5 and 2.0 inch - but I looked at them yesterday again, and they are actually quite wider - two are at least 4 inch out of the boiler room (if not larger - didn't measure them just compared to what I knew was 2.5), and the narrower one is a size smaller, probably a 3 inch.
Header is 3 inch, then the 3 mains come up of which 2 are 4 inch and the 3rd is 3 inch, then the 2 of the 4 inch risers reduce to on an el to 2.5, pass horizontally through the zone valve, a tee for the condensate drop pipe (one going to Hoffman 17c and then to on to the condensate tank), and then then these 2 horizontal 2.5 inch sections have a 2.5 x 4 el and go onto the loop. I am attaching the pic below of the near-boiler piping.

All these mains reduce after the last rad on the loop, and come back as 3, then quickly reduce to 2 and then 1.5 and 1.25 inch returns before the FT and WW78 traps (which are at 1 inch connections), and then are piped on 1 inch to the condensate receiver.

Hope this makes sense.

SWEI · December 2016

If the venting is good and it rarely trips the operating Pressuretrol, you might try raising the limit and just accepting the occasional hour or two of higher pressure operation.

MilanD · December 2016

Great suggestion @SWEI . I suppose that could do that too.

With all this 'greening the steam' thought process though, I am trying to lower fuel consumption while maintaining the most optimum performance and not make it hard on the system by cycling a whole lot. This will be the first winter with all the serviceable parts serviced and back to operating as they should (traps, vents, etc)... so, I'll see how it performs.

For good measure, I'm in the process of installing the water meter by the boiler feeder, and also while at it, I'll add a 5 micron water sediment etc, filter just for the boiler, as an added water treatment. Figured, it can't hurt. We don't have any buried pipes and we are not making up too much water at all, but I'm curious now as to what a normal replacement is. I do blow-down once a week through the port on the water feeder float switch, and do it as long as the water is blackish/murky. Then the same on the bottom drain. This is probably a gallon to 2 gallons a week between the two ports, in terms of flushing out the dirt.

Chris_L · December 2016

MilanD said:

So - my question is this: is there a way to delay boiler from firing again for 5-10 minutes after the initial rise in pressure to the set limit, and it shutting off via vaporstat/pressuretorl (some kind of time-out switch)? Can this be done with any particular tstat?

If not t-stat, how can this be achieved?

I had looked into this for a small one-pipe residential system, but didn't find any thermostats that could do the delay--or other reasonably priced options for a residence.

I have a two-family home and have been experimenting with a home-made device I made for my tenant's oversized boiler. It consists of a pressure sensor attached to a microcontroller (Arduino) and a relay wired in series with the thermostat.

I currently have it set to turn off the boiler for 13 minutes once it reaches 14 inches of water (8 oz.) If the thermostat is not satisfied during that off time, the next run is limited to 10 minutes--though so far, it always seems to cut out on pressure before then. Today, for example, after being off for the 13 minutes it was on for less than 7 minutes before reaching the 14 inches of water again.

I am logging the time on, but don't have enough data to see how much gas it saves. It's clear that even after being off for 10 minutes or so, the steam reaches the radiators in a matter of seconds when the boiler fires again.

If nothing else, this setup saves me the annoyance of listening in to the boiler cycle numerous times (1 minute off, two minutes on) if I let it cycle with the Pressuretrol (set at about 1.25 psi).

EBEBRATT-Ed · December 2016

I think you have done about as much as you practically can with this system. You are bound to have some pressure control cycling from time to time. As long as it isn't excessive and you keep your eye on it occasionally I wouldn't be concerned

MilanD · December 2016

Thank you @Hatterasguy . I googled the "delay relay switch" after the earlier comment from @Jamie Hall and what you suggested was what came up first as recommended buy via google ad (kudos to the company for ad optimization!). I was going to post it to the wall to confirm with the brain trust here, and you beat me to the punch! Awesome and thank you.

I think a lot of people can start using this setup to make steam even more green. Just great!

And thank you everyone for great discussions here and on this wall. @Dan Holohan is a national treasure for all he did to bring this knowledge back to 21st century and for getting together this awesome online community.

KC_Jones · December 2016

It's too bad one can not get this anymore, it works fantastic.

MilanD · December 2016

@KC_Jones

Ecosteam? I've seen some posts about it but not much. Is it known why was it discontinued (was it a one guy shop type thing and he just couldn't keep it going)? Is there schematics plan anywhere for it so it can be reproduced?

MilanD · December 2016

@KC_Jones
Btw, what paint did you use on the header and risers on the boiler that's on your profile picture? I've used regular latex on rads and seems to be holding up just fine. Was wondering if I can use it too to repaint our header and riser pipes on the boiler pictured in this thread, after some of those corroding pipes get replaced in the spring.

KC_Jones · December 2016

I painted with Sherwin Williams All Surface latex enamel. No primer and it seems to hold up just fine. I used "crud cutter" to prep then used the paint. The yellow on the gas lines was a PITA. Yellow doesn't cover well so it took several coats. The black I did in one coat.

MilanD · December 2016

@KC_Jones

Thank you. It looks sharp. And protects the outside pipe from humidity. Two wins!

MilanD · December 2016

So what exactly happened to EcoSteam? Anyone knows?

Fred · December 2016

It was designed and produced by @MarkS (if my memory serves me right) , a member on this site. Maybe he can give you some details.

PMJ · December 2016

@MilanD ,

I see the question of your post raised more and more in slightly different ways. At the bottom of it is that most everyone is dealing with the same fundamental problem. Full fire is too much for almost all conditions and they want to keep the boiler from running at certain times because they know it is not needed but their standard controls are still telling it to run. There are those who tweaked and tweaked with standard controls and have done very well and are happy. There are also those who have invested in sophisticated controls like Ecosteam. What these controls do in essence is limit the run time based on the conditions. To me that is the same thing as spreading the run time out.

I have found that setting a boiler to run 3 even cycles per hour has a dramatically smoothing effect on things. So when you are in this post picking out one particular set of circumstances to delay the boiler restart, try thinking about delaying every restart. Think about adding steam to the system in evenly spaced even amounts. I did this for years with a simple delay on relay and even that was a huge improvement. I have since gotten more sophisticated with a low end PLC control ( the same one that is the brains in the Ecosteam by the way), but my fundamental logic is the same - spread the run out in evenly spaced "pulses". Don't let the boiler run as long on any single burn as it would on standard controls. Radiators never fill (note that conditions never need them to be full) so no pressure is ever built in the system - no cycling on pressure at all ever because there is no pressure.

MilanD · December 2016

Thanks @PMJ! Exchange with KC, Jamie and Hatterasguy have been nudging me to this thinking, and now your comment even more.

Jamie has brought up a point of energy use to get that sitting water to go back to 1150btu per pound of water. It's on a different recent thread here on the wall, pehaps one on wifi tstats. I'm on my phone now and can't find the link.

Anyhow, my question was what wastes less fuel: cycling until tstat is satisfied, or letting the water cool some, or rather, go from 1150 btu to some lower btu level before expending fuel to get it back to boiling and to 1150btu. My supposition is that it depends on boiler efficiency vs. time it take for sitting boiler water to lose btus and then be brought back to 1150 btu. If your boiler efficiency is, say, 80%, boiler needs to be losing 230btu per pound of water that first hour to make it a wash. If it's losing less, you are more efficient to wait to fire. If it's losing more, you better keep cooking sooner. I'm still wrapping my head around this, but I think I'm right. There is also building heat loss to consider.

What you are doing with the delay switch or the PLC (and I'd really be curious what that setup is), leads me to believe that I am correct. Controlled firing will get you close to inputting only the amount of BTU which is lost through building's heat loss, to maintain a certain temperature. On tstat satisfying burn, you basically overshoot the set temp. This means, to be equally efficient, you have to swing the temp around the set temp: for example, heat to 72 and wait to heat again until temp falls to 68. But this is 1. not as comfortable, and 2. may be wasting more fuel because you are now heating from, let's say 850 btu rich water, instead of 920, and will also burn more fuel to heat building back to 72, instead of just 70.

Am I thinking this correctly?

Thanks again! Do you mind sharing what kind of setup you have for this even firing solution?

MarkS · December 2016

MilanD said:
So what exactly happened to EcoSteam? Anyone knows?

Fred said:
It was designed and produced by @MarkS (if my memory serves me right) , a member on this site. Maybe he can give you some details.

Nothing that hasn't happened to other small businesses, insufficient sales over time to cover expenses (esp. insurance). Better to have tried and failed than never to have tried at all.

Gordo · December 2016

@MilanD : Did I see aright that you have an LGB 7 on your system (and one you've done such good work on)?

If that is so, I think there is a lo-hi-lo feature on any LGB 6s and above. You should be able to wire in another vaporstat to get the burners to go to low fire and continue to use your existing vaporstat as a high limit as it is now.

You may experience an issue in finding a vaporstat that will reliably operate at pressures lower than 6 oz/in2, sad to say.

https://www.youtube.com/watch?v=3dBTUp7SAMo

How to delay boiler from firing again right away after max op pressure is reached?

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