Short Cycling New Burnham 5SIN

Steve Nichols

Okay Folks,

I had a new 5 section Burnham gas-fired steam boiler installed on my home's 1 pipe steam system.  The piping looks good, Everything seems proper.  Multiple skims and drains to get a lot of the crud out of the boiler (either due to boiler itself of stuff from existing piping) has tamed a wild water line.

The problem I think I am having is that the system seems to be short cycling.  I have the pressuretrol set for 0.5psi cut in and about 1.5psi cut out.  I'll know exactly when my low pressure gauge arrives and I get that installed.

Right now, once the system hits the high limit, it takes about 1 minute to get back to where the damper re-sets and the burner fires off again.  The burner stays lit for about 1.5 minutes and then trips off on high pressure setting.  It does this repeatedly until the Tstat is satisfied.

I have new Gorton #1's on the Main lines (one at 45' long the other at 30' long) and a mix of Venrites and Varivalves as I early on tried to balance the system.  Mind you, this is a convector system. 

The one thing I will say up front is that the EDR for my house fell at the high end of what the 4 section could accomodate so the contractor thought it would be better if we went for the 5 section, so this thing could very well be oversized. From reading all the posts and Dan's books,  I know that can be one factor that causes the short cycling.

I am going to be calling the Burnham rep tomorrow and see what s/he has to say, but wanted to see if you all had any advice for things I should check or have my contractor check. 

Thanks in advance again folks.

nicholas bonham-carter

short-cycling

i think you will find when your gauge arrives, that there is not enough main venting on, and the back-pressure is tripping the pressuretrol.--nbc

ChrisJ

Pictures

Everyone here loves to see pictures of the boiler piping including my self.  It will also help us rule out the piping with no disrespect to you.  Its just one of those things, it makes you feel better to be able to see it your self.



A friend of mine had an IN5 installed which was way oversized.  Once it was downfired quite a bit it helped things a lot.  This can probably be done in your situation as well though I doubt Burnham is going to be willing to talk to you.  They usually refuse to help homeowners directly.





Chances are also fairly high that what you set on the pressuretrol is not what it is actually tripping at, though they are usually biased towards the highside rather than the low.

Steve Nichols

Boiler Pictures

Here are the pictures of the boiler piping.  Thanks NBC and ChrisJ. 

Paul48

Steve

Are those returns running diagonally down that back wall?

Steve Nichols

Yes, Paul, angled returns

Yes,

the returns come off of the mains and then angle across the front wal with some considerable pitch, l and then make a 90 degree  turn down the side wall and continue to angle down.  I'm guessing you are not loving that setup.  The old boiler had no Hartford loop, no equalizer, etc....but ran fine.



Should I drop those returns straight to the floor and pipe across and up into Hartford loop (or pay someone to do that?).

The topmost return feels hot hot showing evidence that steam is traveling down it a good ways.  The topmost return is essentially dry until it hooks up to the union where it then drops below the water line.  The bottommost return is a bit more below the waterline but not much.  The new waterline is much lower than the old one and I was concerned about how the placement of the returns would act with the new setup.



The fun never ends!  At least I do have heat!  I can post more pictures if need be of the return piping.  I did that in another thread but can repost if you'd like to see.

Steve Nichols

this might help...return piping pictures

before I got the boiler in the house, I was seeking advice about the returns....here is the thread.

http://www.heatinghelp.com/forum-thread/142118/wet-return-question#p1270596

Paul48

Read "A" Dimension

http://www.comfort-calc.net/Steam_FAQ.html

Steve Nichols

Getting hung up on A dimension, I think.

Paul, yes I have read that many times and where I am getting hung up is on where to determine the lowest steam carrying pipe.  From the current waterline to the steam mains, I have about 40".  Even with the old boiler, most of the return length was above the water line until they got close to the back of boiler where they were piped in.

As the system currently sits, most of the return piping is indeed dry until they join and drop down to near the back of boiler, at which point they enter into the near boiler piping.

So, I guess I am misunderstanding the proper location/position of dry vs. wet returns.  Anything below normal waterline is wet--got that.  So, dry returns are returning the condensate as droplets until they reach waterline level?   

And the big question.....Should these things not be angled along the back wall? Should they be piped horizontally, keeping them above normal WL, then drop straight down and across into Hartford loop?

Or should these lines drop straight down from the end of the mains to floor level and snake around to the boiler?

Sorry for all the questions.  I'm a scientist by profession and somewhat of an engineer by hobby, meaning I love all things mechanical and otherwise.



Going upstairs now to re-read Dan's book WRT return piping, venting, etc.

nicholas bonham-carter

high returns

those returns should definitely drop down to the floor from the a dimension height.

as the pressure builds in the present piping, the rising water in those returns could starve the water in the boiler.--nbc

Hap_Hazzard

"A" dimension

The "A" dimension is from the water line to the lowest horizontal steam-carrying pipe. Emphasis on horizontal because any horizontal pipe above the water line can potentially carry steam. Also, for the sake of argument, consider any pipe that isn't vertical to be horizontal.



You can run your returns high and dry, with a 1"/20' minimum pitch, as long as they stay more than 28" above the maximum water level. As soon as you start approaching that level, you need to drop your returns vertically to the level of the Hartford loop or below. Once below water level, pitch is unimportant.

Rod

Sloped Returns & the "A" Dimension

I agree with NBC. You may find your boiler runs out of water!  The "A" dimension is 28 inches vertical above the boiler's waterline  Going straight up just fills 28 inches of pipe above the water line with water. Going at angle, especially slight angle over a long distance means you have many FEET of pipe to fill  to reach the 28 inches height above the waterline.  I don't know about the Burnhams but I know some Weil McLain models don't have much extra boiler water capacity and something like this would cause the LWCO to shut down and/or activate the automatic waterfeeder which would then cycle and flood the boiler.

   The other thing I noticed is the returns joint either above or very close to the waterline. They shouldn't join anywhere except well below the boiler waterline.

On the short cycling- More main venting should help. The burner should also be able to be downfired a bit. You will need someone with the equipment (combustion analyzer) and knowledge to do that for you.

The high boiler riser and header looks very good and it should produce nice dry steam for you.

- Rod

Hap_Hazzard

Down-firing atmospheric gas burners

There's only so much you can do on these without getting smaller orifice spuds. If you just turn down the gas control, you may drop the manifold pressure too low. These things allow only a narrow range of deviation in manifold pressure, and most techs prefer to set it right in the middle to avoid having it drift out of range. Even if it allows a wider range they don't like to go too low and risk a callback on a really cold day.



You can adjust it yourself by clocking the meter and then having a tech come out and check it. If the flue gases and temperature look good they usually don't even check the manifold pressure, and if they do they're less inclined to change it if everything looks good and you're not complaining about performance.



But it's important to have a professional do a combustion analysis, unless you have the equipment and know how to use it. No one can smell carbon monoxide, and you can't tell how much of it you're producing by the color of your flame.

Steve Nichols

The pieces are coming together!!

Okay, now it all is making sense to me.  Thanks for the input on the sloping returns and why they present a problem.  It should not be a big deal to repipe as you guys suggest.  Should there be some type of venting at the elbow where the dry return drops to the floor?

Thanks so much guys!  Waiting for more main vents and will start to get estimates to repipe returns as you have suggested.

ChrisJ

Safety valve

Not to make your day worse, but your safety / pressure release valve is installed incorrectly.  As per Burnham's instructions the safety valve MUST be installed with the spindle in the vertical position.

Paul48

Equalizer

Is that equalizer 1.5"? Not trying to beat ya up, but you might as well get everything straightened out now.

Steve Nichols

okay, okay

Thanks for the heads up, everyone!

Safety valve will be properly positioned once I fit a tee to allow for additional skimming.

WRT Equalizer pipe, I'll see about bumping it up to either 1.5 min or 2". 

I am really beginning to understand how all this fits together, albeit a bit late in the game.  

Going to see about those return lines, also.

At least I think I can get those mains vented more effectively to increase cycle time on the boiler!

Paul48

Steve

The 1.5" equalizer is by-the-book. If you paid to have the boiler installed, they must install it to manufacturers specs,or make it right.Steve, did you look at the link I posted about "A" dimension? Look at the picture at the end of the paragraph. There has to be that 28" vertical drop to the wet return. It creates the pressure imbalance that allows the condensate to return to the boiler. I don't mean to "beat a dead horse", if you've got it already.

Rod

Location of Main Vents

On your question "Should there be some type of venting at the elbow where the dry return drops to the floor?"   The answer is No if you already have main vents at the end of the steam mains.

 On a 1 pipe parallel steam system, the best place to put the main vents is on the top of the steam main just down stream from the last radiator lateral on the steam main.

As an alternate position you can place the main vents at the end of the dry return pipe just before it drops down to the wet return. Placing them here is more matter of convenience than a benefit.  It's a waste of steam and time, making the steam travel all the way to the end of the dry return just to close the main vent.  When the main vents are just after the last radiator lateral, when steam reaches them, they quickly close and trapped air in the dry return stops the steam from going further down the main/dry return so steam is now routed into the radiators.

- Rod

Steve Nichols

Oh boy....

Okay,

Yep, I have read the selections about the A dimension.  I need to get someone over here to give me a quote to repipe these.  As it runs now, the water level has been relatively stable, fluctuating 1" max near center of glass.  Still getting lots of dirt out of the boiler.  Water level fluctuation might change once we really get into cold weather, but that's a guess.

The dry returns after the main vents are definitely hot for a good portion back towards the boiler.  Again, with the new boiler, all sorts of new stuff is cropping up.

I didn't notice the size of the equalizer being too small.  It's a 1.25" pipe not a 1.5" pipe.  I know that Burnham specs call for 1.5" minimum.  I need to tread lightly with my contractor about the repipe as we don't have the best working relationship.  Let's just leave it at that.  I'll call and see what he says.  He may surprise me, but I doubt it.

Since we've opened the can of worms, is having the equalizer 2" below center of gauge glass acceptable or should it be lower? I think Burnham spec. is about 2" down from center.   If we're redoing the piping on that side, maybe this should be done also?

"A dimension"...does it matter where the vertical drop occurs?  Namely, can I keep the returns straight and drop vertical near boiler in addition to dropping them straight down from the mains and around the basement floor?  The second option may be necessary as the lines are just below basement windows and any raising will put them right in front.

 

Paul48

Dry Returns

Like the mains, must continue to pitch 1/4" min./ 10', to 28" above the NWL at their lowest point. I believe the 2" dimension you are refering to, is the height of the Hartford Loop below the NWL, and that is correct.

nicholas bonham-carter

not on the best of terms

i wonder if you could elaborate on the experience you had with your installer. so many people looking for answers here seem to have the same problem. maybe in retrospct you can offer some advice.--nbc

Steve Nichols

I'll get back to you on this NBC

Let me see what I can do with talking with him and we can go from there. My story is somewhat complicated but I'll be happy to share once I see where I stand.  There were some motivating factors that I'll describe later on. 

crash2009

Convector system huh?

  Are they cast iron convectors, or the lightweight fin-tube?  What is the EDR?  Also, What is the model # of your thermostat?  Was the thermostat replaced recently? 

I am not dis-agreeing with your need to drop the returns to the floor, and maybe increase the venting capacity of your mains, and possibly get a vaporstat.  I just wanted to throw the thermostat thing into the discussion because it is part of having a thourough overview of your system.

Steve Nichols

Info for Crash and NBC

Okay, here's some more info:

Tstat is LuxPro PSPA711a.  Was in house when I moved in during fall '08. 

House has all thin tube semi-recessed floor convector units.  EDR using Dan's EDR book comes out to 256SF.  I realize the boiler may be oversized b/c there probably is not that much of a pickup factor on these things.   I did the calcs myself. I thought I'd be on the upper limit of the 4 section.  I gave my numbers to the contractor and he had his engineer do them.  They came back and said I needed a 5 section to make sure on those zero degree days it provided enough heat.



After the first burner cycle when steam has made it to all convectors, the Gorton#1 on the  longer main line "breathes", but the vent on the shorter line does not.

To add to the mix, I have varivalves on many of the convectors and Ventrite 33's on some.This was done because the reducers in the convectors were frozen in place and some were 1/8" and some were 1/4", so I worked with what I had.  I tried to get Ventrite 51's but I don't think they make them anymore.



On a more positive note, I contacted the contractor and he agreed to come out next Tuesday with the Burnham rep and take a look at the setup. He indicated that he has never installed anything other than 1.25" on an equalizer but was willing to change it.  He indicated that it would not help the short cycling, which I said understood.  I more want the water to not push out the bottom of the boiler, right?



Should I push to go to 2" instead of settling at 1.5" for the equalizer?

And..will the rep not like to see a low pressure gauge teed into the pigtail below the pressuretrol?  I can wait on this if need be

Again, I am very very thankful for the contributions everyone has given to me as I navigate this process.  I hope I can return the favor.

Paul48

Engineer

I think that engineer toots the whistle.He obviously knows nothing about steam systems. The 4 was perfectly sized for your system, and the 5 is 30% over-sized.It either makes enough steam for the system, or it doesn't. Does he think you make hotter steam on 0* days? As for the equalizer size,  the manufacturers spec is sufficient, and all you should expect. Regardless of the fact he likes 1.25" equalizers, he has to install it to manufacturers specification, period. You can't drop in a replacement steam boiler into an existing system, and then head for the door. It requires an evaluation of the whole system, including venting and return configuration. Make sure you get a business card from the rep, and provide him with the sizing information, as well.

SWEI

Can they remove a section?

Just wondering...

ChrisJ

Remove a section

Probably not as the burner and housing as well as the outer jacket is all designed around the 5 section block.



He can however, remove a burner tube but it will take longer to make steam.  Either way because the installer messed up he is stuck with a boiler that will never work as nice as an IN4 in that setup.

crash2009

Does this new boiler

 only short cycle in the morning, and then after that it runs ok?  Is it possible that the short cycling is being caused by an overnight setback, or, possibly bad batteries, or, defective thermostat?

Steve Nichols

yep, that's what I thought

To answer a previous question, the boiler takes about 15 mins to produce steam at the mains from ambient conditions.

From that point on, if Tstat calls for heat, system runs, trips off on high pressuretrol setting (1.5psi), takes about 1 minute to "come down" past differential setting and refire and then is on for 1.5 mins; cycle repeats until Tstat is satisfied.

Again, I will add more main venting to see if that helps.



I'll definitely give the rep my EDR values but I pretty much had a gut feeling that the boiler was going to be oversized and I'm stuck with it. 

Just a thought, but can I use the extra boiler heating capacity to heat hot water or is that going to cost a lot?

crash2009

Let me re-word that

  Is the thermostat contributing to your problem.  Check for setback and also make sure the thermostat is set for the type of convectors that you have.  If the thermostat is non adjustable (for steam and convectors), toss it and get one that is.

SWEI

atmospheric burner

Right, forgot there was no gas gun on this.

Hap_Hazzard

Burner Tubes

Funny you should mention that. I had been wondering if it would be possible to down fire a boiler by taking out a burner tube. (Actually you'd remove an orifice spud and plug the hole. You could leave the tube where it is.) It would be less expensive than replacing all the orifices while still maintaining the correct manifold pressure. Since I'd never heard of anybody doing this, I thought there might be a downside, like uneven heating putting stress on the castings somehow, but I've never heard of that either.

Steve Nichols

tstat for steam?

Crash,

The tstat defaults to the most precise setback in that it samples temp more often per minute.  I fiddled and bit and moved the setback value so it samples  less frequently.

I'm definitely interested in updating the Tstat but have never heard of ones that could be as detailed as you describe.  Any suggestions?



I'm now believing that the short cycling is due primarily due to boiler size coupled with less than adequate venting.  I can solve one easily, the other...well that's another story.

Paul48

Rep

Talk to the rep about the size issue. Some things mentioned will only delay the inevitable. Once that boiler starts to steam, it will produce to much. If you can get him on your side, he may offer reasonable solutions for you. You have to walk a tight-rope between the contractor and the rep, and don't expect him to take sides in your presence. When they get outside, the rep may wise him up.

crash2009

I am using a Honeywell T87

  It looks like a bit of a dinosaur, however, I am told that it is one of the best "old style" thermostats out there.  There are some newer Tstats that some others around here are using successfully.  I am not trying to start a Tstat debate, it's just what I happen to have.  Mike Kusiak coached me in getting mine setup.  I was surprised at how adjustable an old dinosaur can be. 

  http://www.heatinghelp.com/forum-thread/138952/Mike-Anticipator-Settings



To begin with, shut off any setback features that you might have programmed into your Lux.  Oversized boilers and setbacks do not work well together. (guess how I know that) If you look on the following picture, you can adjust a T87 and other steam thermostats, (I think Vision Pro is another one) to run the boiler long and hard, or short and light.  In your case, oversized boiler and fin-tube you want to be set short and light.  Maybe not as extreme as the right side of the following picture, but you definately don't want to be set like the left side.  If you look close at the left side, you can see a short cycle just before the cycle is over. 



In the second picture, this is a zoomed in shot of a short cycle and a normal one.



It might take me some time to find it, but the third picture shows a cycle with 5 short cycles within it.



The point is, short cycling can be reduced with the proper thermostat and correct venting.  If you decide to look into the thermostat option, start a new thread for thermostats.  You will find out everything there is to know about them.  There are a lot of very smart people here.

crash2009

Found it

  This one was a very long cycle, definatly not normal, I think a window was accidently left open on a very cold day.  I wasn't here at the time and I am not sure if the boiler was cycling because it was out of water, over-pressured, or both.  I just wanted you to see the picture because an improperly adjusted thermostat can give you the same scenario.

Steve Nichols

Here's Hoping!

Paul,

Thanks again for the guidance.  Your prodding got me to call the contractor and discuss the equalizer concern.  He  is willing to change it.   I mentioned the short cycling also.  It was he that suggested the rep come out, so that's a good start.  I know that I need to be diplomatic and just present the facts.  I am not one to talk down about anyone, especially in front of a company rep.  I'm kicking myself for not going with my gut on the boiler size. 

Steve Nichols

that's pretty cool!

Crash,

Thanks for posting that information.  I'm going to look over my Tstat manual and see what I can do.   I am all for updating/changing the Tstat to be more steam friendly if need be.  That data logger is pretty darn neat.  It looks like the program I I use when I teach labs.

Bio

More venting

As you mentioned in your initial post you have G1's on each main, that's no enough and it will cause more frequent short cycling, if it was me I will add a G2 each, it will fill mains without short cycling, than vent radiators with G6 and Gc, just my 2 cents

Dave in QCA

Two Errors

It seems to me that there were two serious errors made by the contractor relating to the installation of this boiler.   First, they installed the wrong boiler.  It is too large.  Second, they did not follow the manufacturer's instructions relating to the equalizer.



While the equalizer is definitely a problem, I do not think that it is causing the problems that you are experiencing in regards to short cycling at the point the system is fully heated.  Don't let the contractor throw you a bone of offering to replace the equalizer on the basis that they will do nothing more than that.



It really appears that they will have to replace the boiler with the proper size to make the thing work correctly.  What are your EDR numbers?  Maybe you posted them and overlooked them.  Are your convectors tube and fin or cast iron?  If copper tube/aluminum fin, there is almost no mass compared to a cast iron rad system of equal edr.  This means of course the the system heats very quickly.  Once that happens, the only parts of the equation are the rate of steam production vs. the rate of condensation in the convectors.  The more they are out of balance, the faster the short cycling will be.  Vents will not affect this because the shortly cycling only occurs after all of the air has been eliminated and the system is fully steamed.



Here is and idea that might have some effect.  The effective edr of a convector can be GREATLY effected by the accumulation of dust and dirt.  The heat output and therefor the effective edr are greatly reduced if the air cannot freely circulate through the convector.  If you have not already cleaned them, I would certainly do so.  Vacuum the top, and the bottom as well.  Also, if these are tube and fin, use a very stiff brush or wire brush.  Brush carefully in the direction of the fins to knock off crusty accumulations.  Then vacuum again.  Once they are clean, if you think you can still see residual dust in between the fins, put the hose on the outlet of the vacuum and blow air through.   This process can make a real difference if they are quite dirty, perhaps enough to have a great effect on the system operating characteristics.



In regards to cycling comments, it is a good guidline for cast iron rad systems to cycle no more than once per hour.  However this does not apply to fintube systems.  For fintube, the cycles should be no more than 2 per hour.  This will also help to smooth out the space temperatures and perhaps reduce prolonged firing and short cycling.  However, given the speed at which your short cycling begins, it may be a situation that can only be resolve by changing out the boiler.



Suggestions in dealing with the negotiations.  It is obvious that you have much more knowledge than the average homeowner.  The contractor surely knows that and may curse you for it.  Don't push his ignorance down his throat.  I think I would wait until the mfg rep, the contractor and yourself are all in the same room and after the rep has been able to gather the facts, simply state, "You guys are the experts, I'm just the homeowner.  The boiler should not be short cycling as it is and that needs to be corrected.  The solution ultimately has to be determined by you, but I think we all know what that solution is."   Then I'd step away, even tell them you're going to give them some time to confer.  Then I'd come back and see what they have to offer.  If their offer does not include replacement of the boiler, I'd bring the conversation back to the point that the boiler, as it is operating, proves that it is oversized for the application.  That you, as a uneducated homeowner deferred to the advice of the contractor's engineer.  The engineer's advice was in error.   Now, it seems as though the solution is to somehow magically shrink the boiler that they installed or install the proper boiler.



They obvsious charged you for a bigger boiler than you needed.  If they agree to change it out for the right one, I would not expect to see that difference refunded.  As the unfortunate homeowner, I would agree to eat that cost.  I think that I would even (this is just me) agree to chip in a little for the extra labor.  But the contractor should bear the brunt of the error.  They should extract it from the hide of the engineer and he will likely not make such a mistake in the future.  Life is a continual learning process.



Good luck on this as you proceed.  Keep us posted!