Simple 2 Pipe Vacuum Setup

Sailah

A raspberry pi mini computer is $35 and has wifi. I was using one to control a steam solenoid when designing our steam trap monitor. I had also hooked up 3 thermisters which are very inexpensive when data logging.

I would think one of these would be perfect for controlling a system like this.

I was able to remote in on my smartphone and change set points, alter solenoid on off time, see datalogging.

Could allow you to monitor boiler run time. Add in outside temp would be interesting. My new American Standard controller has all this built in and it's interesting to see run time at various firing stages.

I had a developer write the code for my raspberry pi and I wired it up. It wasn't difficult to add to our network at work. I'd just open my browser and log into it. If anyone is interested in that service I could inquire about how much it would cost. He's exceptionally reasonable and it's almost the same task just changed a little.

Great work I love the thought process behind the methods.

PMJ

Thanks for this @Sailah . Sounds like a lot of control at a very low price.

I have one caution for folks on choice of control. The fundamental difference between PC and PLC based equipment is reliability. True PLC's literally never stop. No reboots ever. PC's as we know..... I have no experience with Raspberry and I don't want to unfairly question it for reliability but generally speaking PC based is not close. The Teco I can vouch for - never stopped once in many years now. Continues on by itself after power outages too. I believe it is the brain in Ecosteam.

I have much factory floor experience with this kind of equipment and run both systems. Where the occasional reboot is no big deal I save the money and go PC. Any critical system control must be PLC. Commercial PLC's with lots of I/O cost much more than PC's.

But it sounds like the setup he mentions here is a great way to start out and try things. Maybe even reliable enough as the final control - I can't say it isn't. I would just pause before I leave something running my house with it zero degrees outside while I was somewhere on vacation.

Jamie Hall

@PMJ -- your comments on the reliability (or otherwise) of PCs and PLCs are, quite frankly, why, if I choose to try some of these ideas -- which are very attractive -- it will have to be done without any solid state components at all. The operation I care for must be able to restart, on generator power if need be, with at best a mechanic from the oil company. The controls need to be bulletproof -- or as close to bulletproof as possible. They must also be both simple and obvious. To which end, while there is a solid state programmable thermostat, it is backed up by two mercury T87s. Pressure limiting is a mercury vapourstat, backed up by a mercury pressuretrol, backed up by a microswitch manual reset pressuretrol (with a Hoffman Differential Loop to protect the system if all three controls fail, and a pressure relief valve, of course). Low level is a McDonnell Miller 67 (all mechanical), backed up by a manual reset probe unit. I would like the system to be fail operational for any single unit, but it isn't; the weakest link is the oil burner.

So... if I do go vacuum, it will be natural... still thinking about it.

Sailah

@PMJ that's a valid concern. The other business in our building builds custom panels and MG sets and they wire and run a ton of PLCs.

My experience with the Pi was very good. It ran continuously for 1.25 years without a reboot. Maybe there was one I can't remember. Had it controlling a SS relay that ran the 120v steam solenoid. The thermisters were Dallas protocol units.

What I like about the concept of the Pi is that if someone came up with a workable program, you can share the disk image freely. The Pi runs off of a micro SD card so you just pop a blank card in a computer, burn the disk image to the SD card and put in the Pi. Apply power and you now have a clone.

The other issue which I would think would be particularly interesting is the ability to run remote sensors or control the system via web interface. I'm working heavily on this now with my steam trap monitoring system. Off the shelf sensors are so incredibly cheap it's crazy. You could set up remote sensors or remote solenoids anywhere in your house where you had Wifi and control all of them with the Pi from your phone or computer.

I don't know if the PLC has that functionality but the IoT (Internet of Things) is probably the fastest growing segment for machine control and machine learning. I'm working with IBM Bluemix and Watson to enable predictive analytics to control steam systems based on weather patterns (IBM owns the weather channel) and also to have our monitoring system tell a large university that there is a 92% chance that a trap will fail in 15 days etc. It's actually a little frightening how advanced the computing power is getting. And how inexpensive it is. You can rent IBM Watson for $30/month!! It's like SkyNet, but a friendly SkyNet

Chris_L

I've taken a different approach to the question of reliability. I am using an Arduino microcontroller to turn off and delay the refiring of an oversized, residential, gas boiler on a one-pipe system. (Once a pressure of 12 inches of water is reached, the boiler cycles off for 14 minutes, and on for 7 minutes, as long as the pressure limit is not reached or the thermostat satisfied.)

The control is wired in series with the thermostat, so it designed to simply revert to the normal boiler controls in the case of a power or other failure. There haven't been any since I started using this at the beginning of this heating season.

Since the boiler uses a millivolt gas valve, I don't want a power failure to stop it from working. Once the power comes back on, the Arduino restarts like it did when I began using it.

With the power on, for the relay to stay open (no heat) when it should be closed, it would have to fail mechanically, something the code checks for, or the code would have to freeze while the relay is open, which seems very unlikely.

There are a couple things I have concerns about with these home-made controls, though. One is relay chatter. You don't want the relay quickly turning the system on and off when calling for heat. This hasn't been an issue for me, but is something I need to protect better against.

The other, for those who access their controls through the web, is security. That is a whole other area, one I don't have to deal with, as I limit access to my local network.

Finally, @Sailah mentions how inexpensive sensors have gotten. I've had good luck measuring steam pressure with 0-5 psi pressure sensors you can get for $20 - $30 on eBay or Amazon. (Haven't seen any with a lower range.)

PMJ

Really cool stuff for sure @Sailah . I'll work on extending my thinking into the remote/wifi zone.

Looks like Jamie is going to take more convincing!

PMJ

Chris_L said:

I've taken a different approach to the question of reliability. I am using an Arduino microcontroller to turn off and delay the refiring of an oversized, residential, gas boiler on a one-pipe system. (Once a pressure of 12 inches of water is reached, the boiler cycles off for 14 minutes, and on for 7 minutes, as long as the pressure limit is not reached or the thermostat satisfied.)

Great approach @Chris_L . Really great to hear from someone cycling a one-pipe. No balance issues? That seems to be of great concern here.

7 minutes of fire out of 21 ongoing will heat on the coldest day? That is really oversized.

I'm curious what the pressure limit is and how often you hit it.

Thanks for sharing this.

Chris_L

Thanks @PMJ. I'll try to answer your questions, but note that this boiler serves my tenant's unit in a two-family home so I don't have complete information.

I haven't heard of any balance issues. Tenants say the heat is fine. (If they are happy, I am happy.) Even on the 7 minute runs, the pressure starts to build quickly indicating most or all of the radiators are full. And if the vents are open on any, that is where the steam is going.

Boiler is rated for 356 square feet of steam and the connected EDR is 203. So it is very oversized, which I suppose is why I can keep it off so much.

It hasn't been that cold this winter, but I too wondered how well it would do on our coldest days (10 - 15 F). Didn't have any problem heating the place.

I currently have the pressure limit set at 12 inches of water (about 0.43 psi or 7 oz.) My tenants set back the thermostat a lot. Figure the boiler has been off 10-12 hours before coming on in the morning. It will always shut off on pressure (and did so with the pressuretrol at about 1.2 psi). On the 7 minute runs, it might or might not, but the pressure is getting close even if the clock runs out first.

I log the pressure when the system is running. If I have a chance, I'll post some plots later, both on a cold day with the microcontoller on and earlier in the season with it off.

PMJ

@Chris_L ,

I jumped to concluding the first 12" stop was separate from the actual boiler pressure control on one of your other sensors and that you stopped first at a point that indicated enough rad fill for the first fire and then cycled from there with some room to go up. I actually run 3 different on/off ratios now trying to lengthen calls depending on conditions.

Thanks for the info. Any data you wish to share is welcome. The tenant thing makes it a bit tougher.

Koan

@PMJ Was hoping I could ask a few questions.
The solenoid you suggested was an Arcon UG86 - by chance did you mean UGB6?

My understanding is that you have the valve in the dry return vent set to open to vent once pressure in the system build to anything over atmospheric (zero gauge) to allow steam to pass to the vent. I assume you put a vent into the outlet of the solenoid valve so that air can pass and steam will not. Once the system starts to go below atmospheric (negative gauge) the solenoid to the vent closes (like a diode but for steam) so that air does not go back into the vent. The system cooling with no air coming back in creates a vacuum.

Do I have this correct??

Also, you are using the PLC to set the run time once the system cycles on to prevent overshoot, and the wait time to allow distribution.

thanks for the clarification

I have 399EDR connected to a 750EDR boiler. It is a 2 pipe Hoffman Vapor system complete with differential loop with a vaportrol set at 8oz off and 4oz back on. Currently there is a Gorton no 2 vent on the dry return that I was going to change to B&J 3bm bigmouth.

PMJ

Koan said:

@PMJ Was hoping I could ask a few questions.
The solenoid you suggested was an Arcon UG86 - by chance did you mean UGB6?

My understanding is that you have the valve in the dry return vent set to open to vent once pressure in the system build to anything over atmospheric (zero gauge) to allow steam to pass to the vent. I assume you put a vent into the outlet of the solenoid valve so that air can pass and steam will not. Once the system starts to go below atmospheric (negative gauge) the solenoid to the vent closes (like a diode but for steam) so that air does not go back into the vent. The system cooling with no air coming back in creates a vacuum.

Do I have this correct??

Also, you are using the PLC to set the run time once the system cycles on to prevent overshoot, and the wait time to allow distribution.

thanks for the clarification

I have 399EDR connected to a 750EDR boiler. It is a 2 pipe Hoffman Vapor system complete with differential loop with a vaportrol set at 8oz off and 4oz back on. Currently there is a Gorton no 2 vent on the dry return that I was going to change to B&J 3bm bigmouth.

I'm happy to answer any questions I can.

Looks like you are right - Alcon ugb6. It is 3/4NPT normally closed 110v AC. I have done this with smaller size 1/2 OK too. Lots of choices for these. Nothing special about them.

In the dry return there isn't any steam so we are dealing with air only there. I removed a steam stopping vent on the steam main so there are no openings on it. No rads are ever full so no steam ever makes it to the dry return. So this one location on the dry return handles all the air that leaves the system. It closes just as you say when the system goes negative and vacuum sets in every time the burner goes off.

Yes, the PLC sets a regular on/off cycle during the call to prevent overshoot..... on,wait,on,wait. Currently I have 3 different on/off ratios.

I am not familiar with the details on the Hoffman system.
I don't know how the differential loop would behave in vacuum and if it will cause any problems. Maybe someone can help with that. At a minimum I think you would benefit greatly from cycling that boiler and spreading things out.

Chris_L

@PMJ
I am really just putting another pressure sensor on the boiler, but using it to shut off the boiler at a low pressure and control the off time. I haven't done anything with the radiators or any of the piping as far as sensors go.

I can use my ear to tell when all the radiators are full of steam, however, since I live beneath the unit this control is on. The living room radiator in the unit is the largest and farthest from the boiler. It has an adjustable Vent-rite vent on it, and these vents close with a noticeable clink when the steam hits them if they are set on a high number. I can hear it, and it reliably closes at about 8 inches of water.

My goal was to reduce the amount of cycling with the Pressuretrol. The attached charts show that this has been accomplished. (In the Jan. 8 plots, the boiler is off when the plot is horizontal or slightly sloped at 0-2 inches of water.)

This isn't a vacuum system so I don't care about air getting into it. When the system is hot, the air doesn't stay around for much time at all when the boiler fires.

PMJ

@Chris_L ,

Thanks for this perfect graphical example of what controlled cycling is for. You took an oversized boiler which was banging off the high end of the pressuretrol wasting fuel for no reason and spread the runs out and dropped the pressure. I'm guessing you can spread even further. The outside temp was significantly higher on the ptrol day but the point is still made. My point is that any system banging off a pressuretrol at all is filling rads past what is required for the conditions.

It takes a full rads to build pressure. But rads don't ever need to be full to heat for the conditions so your goal is to keeping dropping that pressure and run them partly full. You have a really oversize boiler. I am only seeing 2 inches water pressure after 7 minute runs. Only my very small bathroom rads are ever full enough to close a trap.

Thanks much for sharing this.

Jamie Hall

Running a Hoffman Equipped system into a vacuum won't affect it -- indeed, the coal fired versions were equipped with the Hoffman 76 or its predecessors, and they close tight on vacuum or steam, but open for air. They were designed to drop into a vacuum, naturally. If it were desired to let the system drop into a vacuum naturally -- an approach I'm contemplating -- it would simply be necessary to swap the existing vent(s) for enough76s to achieve similar capacity.

There is one hitch, however. The Hoffman Differential Loop protects the system from excessive differential pressure -- anything over about 8 ounces between the steam main and the returns -- by allowing steam from the mains to enter the dry returns if that pressure differential is exceeded, thus limiting the excess pressure (hence the name of the device!). This means that any vent mechanism will be exposed to live steam in the event of a slight overpressure. And that means that if a solenoid valve were to be used in place of a vent, that solenoid valve would have to be able to close instantly when hit by steam -- and survive the temperatures. I have no doubt that this could be implemented with a suitable solenoid valve and suitable additional controls, if desired -- but I admit to having some doubt as to whether it is worth it.

It might be argued that the various controls would successfully prevent any possibility of a pressure in excess of the six to seven ounces which a Hoffman Equipped system vapourstat should be set at, and that thus the precaution is unneeded. I would beg to differ -- but I'm a pretty cautious sort of fellow, and I would want my heating system to fail operational, or as close as I can get to that.

PMJ

@Koan,

It looks as if you are good to go with your Hoffman based on what Jamie says.

What is hard for most people operating the conventional controls to realize is that with cycling and vacuum there is no pressure anymore - or only a barely measurable one. Maximum differential pressure between any two points in the system is barely measurable either - in vacuum or the short period each cycle at atmospheric. I monitor the pressure differential between the pigtail and the dry return and 2" water is about the max. I see. I would put the solenoid as far from the Hoffman loop as possible but I think exceeding 8 ounces differential is basically impossible. The boiler is never allowed to run continuously long enough to do it.

Jamie Hall

PMJ said:

@Koan,



...I would put the solenoid as far from the Hoffman loop as possible but I think exceeding 8 ounces differential is basically impossible. The boiler is never allowed to run continuously long enough to do it.

Which would defeat the operation of the Differential Loop (the correct location for the only vent in a Hoffman Equipped system is directly on top of the loop fittings). So long, however, as you have complete confidence in the electronic controls that's fine.

Koan

@Jamie Hall you are spot on for the location of the main vent on the dry return, atop the fitting down to the Hoffman Differential Loop. My traps are mostly Hoffman #18 with one Webster O2H - don't know if that matters. Also using one BJ 2CR and one Hoffman 18 for the two crossovers - the 18 is on a very short main.

One thought - if there was a main vent on the outside (down-flow) side of the solenoid, it would close to steam. Would that work - to simply screw a Bigmouth vent in the output side of the solenoid to prevent steam flow? in any normal operation that vent would always be open. I am thinking it may protect the solenoid from almost all steam flow.

I am confused as to the suggested location of the solenoid - obviously unscrewing the existing vent on top of the Hoffman Differential Loop makes retrofitting easier.

Also I think the Alcon Valve used by @PMJ may be rated for steam.

I also think using dwyer type pressure control along with the vaporstat as a safety would help with safety.

I was doing some research and found Hoffman even made vacuum pumps (though it seems for larger systems) - I'm attaching a pic.

Jamie Hall

Putting a Big Mouth on the output side of the solenoid would probably work just fine. As to confusion on where to put the solenoid -- if you want to keep the protective function of the Differential loop, the solenoid should be placed exactly where the vent is now.

However -- and I haven't gotten an answer on this -- I have to admit that I fail completely to understand exactly what benefit the solenoid and the electronics and all would provide over simply replacing the regular vent with one or more Hoffman 76s, which will do exactly -- so far as I can make out -- the same thing. That is to say, open if and when there ever was positive pressure in the system, but no steam; close on steam; and close and maintain on a vacuum. Perhaps @PMJ can explain what the magic boxes can do that the dead men didn't.

PMJ

For the Hoffman Loop to work the dry return must be closed and pressurize to keep pace with a main already at a pressure way higher than we want to have anything to do with here. Cycling correctly will prevent getting anywhere close to these pressures. If there is even a possibility of the loop actually operating the whole system is way out of the range this whole thread is talking about operating in. 8 ounces in the main means really full rads - something I have absolutely no interest in and is exactly what I have been trying to avoid for years.

I see no reason not to use a Hoffman 76 - especially if you already have one. With the "magic box" I can see exactly when it is actually closed on the computer screen and time the total percentage of the cycle it is closed and things like that. Helps with the study. And I have a standard check valve right next to it for safety should the solenoid not open which costs much less than the 76 because there will be no steam there. I don't think either of the devices will be damaged by steam anyway.

Jamie Hall

Ah. OK. Yes, if one is monitoring on a computer or something of the sort I can see it. Fair enough. I'll stick with the 76s -- but then, my summertime daily driver is a 1970 Chevy C10, which I can tune up with a screwdriver and a dollar bill... just the kind of guy I am!

Koan

My vaporstat is set to cut out at 8 oz. - the gauge sometimes goes a bit higher (about 9 OZ) but a small amount of fiddling should fix that. It is the old mercury tube. I 'll double check and probably dial it back down to 7 OZ. My understanding is the Hoffman Differential loop starts equalizing at 10 OZ.

Jamie Hall

Koan said:

My vaporstat is set to cut out at 8 oz. - the gauge sometimes goes a bit higher (about 9 OZ) but a small amount of fiddling should fix that. It is the old mercury tube. I 'll double check and probably dial it back down to 7 OZ. My understanding is the Hoffman Differential loop starts equalizing at 10 OZ.

Theoretically. However, the very best way to set your vapourstat is not to worry about the numbers, but to listen to -- or feel -- the Hoffman Differential loop. If the pressure gets too high and it trips, you should hear it (they gurgle!), and you will be able to feel that the dry return pipe coming into it at the top gets hot. If that happens, dial the vapourstat down.

Koan

@Jamie Hall
Great point. I intentionally bypassed the vapor stat once and noticed exactly what you state. I remember hearing the gurgle but it was over an indicated 12Oz pressure. Here is a thought though - the Hoffman Differential loop works based on a pressure difference. Does creating a vacuum in the system make it trigger sooner??? It seems the reference point is atmospheric, but maybe creating a vacuum makes it trigger at lower pressure??

Jamie Hall

The differential pressure which the Hoffman Differential is looking at is the one between the dry returns (and by extension, any wet returns) and the steam mains -- specifically, the pressure in the boiler header. Since the traps don't seal against a vacuum, if the steam main drops into vacuum the dry returns will also be in vacuum, with very little pressure difference -- so, after way too many words, the operation of the loop should not be affected by a vacuum in the system.

It might seem that the reference would be atmospheric, but it isn't.

It really is a most amazingly simple contraption! With several nifty benefits -- and no moving parts.

PMJ

@Koan,

As you move down field with this you will find out that operating your system stopping on a pressure limit of any kind is a waste of time and energy. Pressure means over filled rads for the conditions period. Think about a first cycle that warms up your piping expels air slowly and fills rads a little. Then a cycling program that fills a little more and expels a little more air each time with vacuum in between for more minutes than your burns. Each cycle will fill a little more than the last with the piping a little hotter a little farther out each time. In this way there will be no pressure - mostly vacuum. The Hoffman loop will see single digit inches of water difference between main and dry return and do nothing. Your vaporstat will become only a safety device. I don't think my vaporstat has tripped in 10 years or more.

Look at the charts @Chris_L posted. Look at the pressure reduction he got cycling and spreading just a little. I am telling you the peaks can go to 2-4 inches water tops and still heat your house. I know this is a little difficult for folks who have spent their lives operating on pressure - even very low pressure.

Jamie Hall

PMJ said:

@Koan,



... I am telling you the peaks can go to 2-4 inches water tops and still heat your house. I know this is a little difficult for folks who have spent their lives operating on pressure - even very low pressure.

Ah yes. Well, my knuckles are dragging a bit, but I guess I'll just get on from this. 'bye.

izhadano

PMJ. "I got to thinking that some people might be thinking that my setup is complicated and expensive. It really is neither so I thought I would detail a possible simple starting place for any 2 piper interested in giving it a try".
=======================================
Peter,

thanks for discussion and shearing your impressive results. Sorry, I'm late with my 2 cents - tax prep timing, etc.

I've tinkered with single pipe steam heating system with naturally induced vacuum back in 2010 in my house. Every radiator was equipped with Hoffman-401419 1/8" x 1/4" Angle Steam Air Line Valve and check valve (1 psi ) combo in order to let air out at cold start and prevent air entering into cooling system. Here are graph of vacuum formation in cooling system and achieved fuel savings from presentation at ASHRAE conference, Montreal 2011. The achieved results were ~ 10-12%,- pretty modest compared to your results for 2 pipe system with naturally induced vacuum but keep in mind that it's single- pipe system vs two-pipe system.

Later on the leakage on check valves problem started and I have to look for better solution. So the idea came of boosting steam system by vacuum at cold start and minor assistance to a naturally induced vacuum later on. For new leak tight installations vacuum pumps would be employed only at the very first start to create vacuum in a system and on rare occasions later to maintain it.
Making/keeping retrofitted old steam system leak tight is difficult, but starting system in a vacuum and running it at positive pressure (1-2 psi) would prevent air leakage into the system and improve efficiency. These are data on HDD and heating bills for single pipe steam heating system on second floor apartment of my house before and after retrofit; for comparison first floor is shown where no retrofit happen.

It seems to me that in 2 pipe steam systems with naturally induced vacuum, which are bigger then yours, several solenoid valves should be employed in order to evenly push air from the system and controlling/orchestrating these valves would be more sophisticated task.
Also, heat load in cold weather counts for ~30% of the total heat load for climate in cities like Boston and NYC. So, for the rest of 70% heat load (spring/autumn) your system have to employ 102-104oC steam at any boiler cold firing. That's significant overkill of demand in warmer weather and would reduce system energy efficiency.

And regarding vacuum pumps. I bought piston vacuum pump (oil-less, corrosion resistant) for ~$500 for my 1050 sq. ft. It's sufficient also for a recent 3000 sq. ft. project (mixed 2 and 1 pipe system); put another vacuum pump there for back up.
The pump life expectancy is 10000 hrs, so 25-30 years can be expected 1-1.5 hr/day. So it's ~$20/year for improve comfort and energy efficiency. I believe it worth the gains.

Hope it helps.
Igor

PMJ

Jamie Hall said:

PMJ said:

@Koan,



... I am telling you the peaks can go to 2-4 inches water tops and still heat your house. I know this is a little difficult for folks who have spent their lives operating on pressure - even very low pressure.

Ah yes. Well, my knuckles are dragging a bit, but I guess I'll just get on from this. 'bye.

Jamie,

I see I put that poorly and I apologize.

I meant to say that I can see how it might be difficult for folks who have operated on pressure controls for a very long time to believe that there is a pretty simple way to operate at pressures so low that all the pressure devices are basically obsolete.

I have been watching my darn system for 25 years and only this season am I really appreciating some of the really subtle reasons why the results of operating this way are so much better. It could be argued that I am a pretty slow learner. Still, it does take more than a minute for this to sink in. @Chris_L I think did us a major favor with his pressure plots. I hope to present soon a graphical representation of pressure in my cycles to show what I have learned about what is happening so people can compare with his. The graphical presentation of the cycle really helps picture fully what is going on.

So I hope you don't go. I think there is much more ahead on this. I think as people much smarter than I latch on to the concept they will push it a lot farther.

Koan

@izhadano What vacuum pump did you buy?? Thanks

izhadano

HP120V Dry Rotary Piston Vacuum - works 3rd season for me no prob.
http://www.airtechusa.com/products/hp120v.html

Eastman

It was a mistake to control automatically fired steam boilers with conventional thermostats. The steam industry should have evolved its own dedicated methods for communicating occupant heating demands and managing burner cycling strategies. The acceptability of cycling on pressure is evidence of this failure.

Koan

Of course a boiler sized for 1.88 x my 400 EDR of radiators isn't helping me one bit. The problem is I see people here replacing 7 year old boiler sections when mine is 49 years old and it makes me hesitant to replace it. My thermostat is horrible and the overshoot is significant. Now that the boiler is clean it rarely cycles on pressure though. Some days I feel I'd be better off with a switch!

Koan

@izhadano My rads total 400 EDR and I have a nice Hoffman Vapor residential system with an oversized boiler (750 EDR). It is down fired a little but this model seems unfriendly to any further reduction. Clocking the meter shoes about 250mbtu/ hr. When it fires up the meter clicks off cu ft in staccato. I assume I could use the smaller version HP40V of this pump to suck out the air on the dry return prior to the burner firing on a timer from the thermostat. My hope would be the boiler would see a vacuum and water would then boil at a lower temp, then fire at cycles on a very low pressure. Just ideas, but if anyone thinks I am off base I would prefer to hear it. I think the cycle idea is where Mark S headed with the Eco Steam ES 20.

izhadano

Koan,
would you, please, tell more about your system type, number of radiators, house sq. ft, etc?
And sorry - I thought that you posted your question under my name - did not realized that it just sub thread. My apology.

PMJ

> @Koan said:
> Of course a boiler sized for 1.88 x my 400 EDR of radiators isn't helping me one bit. The problem is I see people here replacing 7 year old boiler sections when mine is 49 years old and it makes me hesitant to replace it. My thermostat is horrible and the overshoot is significant. Now that the boiler is clean it rarely cycles on pressure though. Some days I feel I'd be better off with a switch!

Oversized boilers become a non issue with managed cycling. The more oversized the boiler, the lower the burn percentage of the burn/wait cycle. Infinitely adjustable, no pressure, no overshoot. My boiler is 60 years old and I am hesitant to replace it just like you. I am sure though that being too big is not a good reason to replace it when a $100 timer relay will solve 90% of your over shooting problems. Too easy. Try it out.

AMservices

Koan said:

@izhadano My rads total 400 EDR and I have a nice Hoffman Vapor residential system with an oversized boiler (750 EDR). It is down fired a little but this model seems unfriendly to any further reduction. Clocking the meter shoes about 250mbtu/ hr. When it fires up the meter clicks off cu ft in staccato. I assume I could use the smaller version HP40V of this pump to suck out the air on the dry return prior to the burner firing on a timer from the thermostat. My hope would be the boiler would see a vacuum and water would then boil at a lower temp, then fire at cycles on a very low pressure. Just ideas, but if anyone thinks I am off base I would prefer to hear it. I think the cycle idea is where Mark S headed with the Eco Steam ES 20.

Even with the 2 cfm pump on your system (as long as the piping is relatively tight) you will see a vacuum on the boilers end.
Anything under atmospheric pressure you will be boiling water at lower temperatures.
Mechanically induced vacuum systems have been around for a long time and the way they would size them for large buildings was 1 CFM for every 1000 EDR. Then they would run the pump to maintain between 5-10 Hg.
the boilers would still need to build pressure to overcome come friction loss of the piping. The vacuum pump on these old systems were there to lower the installation cost more then the boiling point of the water.
With the pump pulling and the steam pushing, it meant the engineer's could use pipe 2 sizes smaller then if they were only relying on the boiler to push the air out.

I do agree, you can correct you short cycling problems if you can keep air from reentering the system.
by first pulling a vacuum, then building a few ounces of pressure, cut the burner and let it fall into a vacuum before relighting. Having a pump pulling the air out with a vacuum switch monitoring the system makes everything that much easier and gives a higher level of control if it's done right.
Depending on how tight your piping is will make or break your goal.
If air is rushing in through leaky radiator valves, those radiators won't heat as well as the others.

Do you go through a lot of water?

Be aware! If your boiler block has any signs of rust damage or leaking, do not attempt a vacuum system. If there's sediments filling cracks or small holes in the heat exchanger, a vacuum will clean them out.
And if the boiler can hold water, it can't heat your home.

Koan

@izhadano Mine is a 2 pipe Hoffman vapor system set to run with an 8 oz limit Honeywell mercury vapor-stat that goes back on at 4 oz. Eleven radiators on 3 floors total long 399 EDR. Built in 1928. End of group townhouse with about 2700 sq ft living space. No radiators in basement where the 1969 American Standard 750 EDR 300,000 but/hr boiler is located. Standing pilot. No flue damper. Just replaced the Hartford loop because it was occluded, system had about ten pounds of gunk in the boiler that is now clean. Put in valves to flush wet returns. New Honeywell gas valve. One Gordon no 2 dry return vent on top of the Hoffman differential loop. 1969 Honeywell Chrontherm thermostat that seems to randomly select when the boiler fires. All traps on the radiators are Hoffman 18 except of one Webster O2H. Two crossover traps, one in each of the 2 mains. The short main is a Hoffman 18, the larger a B&J 2CR. All the trap guts are new .. let me know if I can share any other info

Koan

We don't go through any water except what we blow down manually every other day. Usually about 1 a quart per blow down. We do have rust sediment being almost 50 years old, but I just wanded the boiler out in November really thoroughly until all drain water ran clear. That is when I re-piped the occluded Hartford loop and up in flush down valves on the wet returns. Most of the wet returns along the floor looked fine, just the parts just before they turned vertical to go back to the boiler and the vertical section itself.

PMJ

More detail:

@Chris_L 's charts of pressure prompted me to create some of my system in the hope that it will help everyone visualize what is going on - how low the pressures are and why very oversize boilers are easily managed.

This is not actual recorded data. I simply created it from watching actual gauges on my system. It is how things go from a dead cold room temperature start. I do have a preheat sensor on the end of the main. The boiler runs continuously until the preheat is satisfied, then it goes into the 7on /13off cycle. There is a chart of all 3 cycles and then one of just the first cycle to show more detail.

Things to notice:

No more than 2" of water is ever required to push air out.

The pressure differential of header over dry return flowing steam into the rads actually is the biggest in the first two minutes right after the burner shuts off. This is what I mean by forward motion right at the time when vented systems stop suddenly and actually run backwards. This really is a big difference.

It takes about 3 minutes after the burner fires for the system to return to atmospheric pressure. The total time the system is in vacuum is about 16minutes out of 20 or about 80%.

It really doesn't take any pressure to push the air out in the preheat. It takes no more to push out what leaked back in on each cycle + a little more. I am doing it all through one 1/2" solenoid valve.

Any size boiler can be managed at pressures this low simply by changing the on/off time ratio.

I hope this helps picture things better.

Fizz

Have been using vacuum in my system for one year since last March just using 2 Mepco quick vents(vacuum) one on each dry return(Richardson System) no other stuff. My system is set for 3cpm on hot water setting of t-stat. Vacuum is between 2-4, except on extremely cold days-single digits and below, where a run of about 13-14" will lower vacuum to 9-10. My usual run time has been6-7" per fire. Heat has been steady and comfortable. No vapor lock.. Pressure never gets above 0 on run.